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Endstops will not trigger using Marlin Firmware
I have an old Solidoodle 2 that I bought broken from a garage sale that I am converting to use RAMPS 1.4 with Marlin Firmware. All the motors work correctly, I am just having issues getting the endstops to work.
I am using a regular limit switch with NC going to the signal pin and the other to ground. I have this switch plugged into first header column for X-min. My endstop configuration is currently:
//===========================================================================
//============================== Endstop Settings ===========================
//===========================================================================

// @section homing

// Specify here all the endstop connectors that are connected to any endstop or probe.
// Almost all printers will be using one per axis. Probes will use one or more of the
// extra connectors. Leave undefined any used for non-endstop and non-probe purposes.
#define USE_XMIN_PLUG true
#define USE_YMIN_PLUG true
#define USE_ZMIN_PLUG true
//#define USE_XMAX_PLUG false
//#define USE_YMAX_PLUG false
//#define USE_ZMAX_PLUG false

// coarse Endstop Settings
#define ENDSTOPPULLUPS // Comment this out (using // at the start of the line) to disable the endstop pullup resistors

#if DISABLED(ENDSTOPPULLUPS)
  // fine endstop settings: Individual pullups. will be ignored if ENDSTOPPULLUPS is defined
  //#define ENDSTOPPULLUP_XMAX
  //#define ENDSTOPPULLUP_YMAX
  //#define ENDSTOPPULLUP_ZMAX
  //#define ENDSTOPPULLUP_XMIN
  //#define ENDSTOPPULLUP_YMIN
  //#define ENDSTOPPULLUP_ZMIN
  //#define ENDSTOPPULLUP_ZMIN_PROBE
#endif

// Mechanical endstop with COM to ground and NC to Signal uses "false" here (most common setup).
#define X_MIN_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop.
#define Y_MIN_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
#define Z_MIN_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
#define X_MAX_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
#define Y_MAX_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
#define Z_MAX_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.
#define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.

I have X-min enabled and inverted. When I send an M119 (endstop status code) I recieve:
Send: M119
Recv: Reporting endstop status
Recv: x_min: open
Recv: y_min: TRIGGERED
Recv: z_min: TRIGGERED

And then when I press down the X endstop with my hand I get:
Send: M119
Recv: Reporting endstop status
Recv: x_min: open
Recv: y_min: TRIGGERED
Recv: z_min: TRIGGERED

-No change. There is no mechanical failure with the switches, I've tested it with a continuity tester. I have even shorted the signal and ground pins on the Ramps board with a jumper wire and I still haven't seen any change.
Where is the fault at?

try uncommenting the following lines to enable endstop detection on all pins for troubleshooting.
//#define USE_XMAX_PLUG false
//#define USE_YMAX_PLUG false
//#define USE_ZMAX_PLUG false

This way the M119 will show any changes.
The only thing I can think of is that either the switch is plugged into the wrong pin on the ramps board (Max instead of Min) or the switch doesn't require the pullup (your could try commenting that back as a second test as well)

It turned out to be a combination of those lines being commented out and the end stops were connected to the wrong two pins. On solidoodles board the + and - are reversed for the endstop connectors by default.

After fighting with this for a while, I found out on the end stop pins, if coming from another setup like mine, you need to switch the ground pin to the center of the connector and the 5 volt pin to the pin it is reading, for example 1.29 pin on skr 1.4.
Once you do that then it will read the status of the pin.

I moved the ground pins to the center of the connectors and works perfectly Upgraded to the SKR 1.4 Turbo and couldn't figure out why nothing in the firmware would work.

Thank you so much to the person who said to move the ground pin on end stop. I’ve been researching for a whole day now and finally stumbled upon your comment. Very helpful and fixed every issue I was having with my mini skr board.

Yesterday I has same error with board MKS Robin Nano with Marlin 2.0.6.
Try to find and uncomment this definition:
#define ENDSTOP_INTERRUPTS_FEATURE

Failure was in disabled endstop interrupts and broken part of code, which going to home and unchecks endstop status between steps. But if you activated endstop before sending homing command - it will work as needed.


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Slicer for "metal" 3d printer
In my last topic I learned that Pronterface can control powder 3D printer provided that the slicer generate g-code for printer which is printing from metal. My question is as follows. Is there a slicer (open-source or other easily accessible), which will generate g-code that will be able to command the printer which operates on the following principle?

"Operating Principle" is not enough. Not all printers even take G-code commands to begin with. What specific printer do you have in mind? This determines the slicer you need to use.

If we go on the assumption that the thickness of the added powder for each scan is known (i.e. how far the RH piston moves per cycle), then all you need is to set the slice thickness to that value.  This assumes further that the X-Y position commands sent to the laser positioner are properly oriented as well.

I would suggest looking into how for Form2 printer slices.  It has a laser that solidifies resin which is basically the same principal as the concept in your question.

"Metal" 3D printing is Additive Manufacturing. Do you have a 400W laser?

Your diagram looks as though you're referring to a "Galvo"-based laser system. Is this correct? If so, there are very few systems on the market that operate this way. My guess is that conversion from polar to cartesian and visa-versa would be controlled by the laser systems' controller and not the slicer. However, what you're suggesting as machine design should be handled through custom software, or at least open-source that focuses on this style of printing. I believe you'll find it difficult to find anything currently available in a working stage.

Here's a KickStarter campaign I just came across recently that has a similar concept, using a Gavlo laser. The product is called SafFire 3D Printer/Laser Engraver

Laser SLS printers (3D Metal Printer) software requirements are very similar to SLA printers specially laser ones.
There are lots of different tools which you can use together.
You can use Lasershark 3D together with creationworkshop.
Also you can convert your source file to SVG or image files, using Slic3r, nanoDLP SLC2PNG or Asiga Stomp/Sleece. And convert SVG or Image files to toolpaths using cad.py, gcodeplot or any other freely available softwares.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

sort: votes


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Marlin Adjusting feedrate
I'm using the Marlin firmware (1.1.0-RC7 - 31 July 2016) for a 3d printer. Currently the printing is not perfect due to slight inaccuracies in movements along the x and y axis. I'm trying to change the feedrate for speed along the xy axis whilst the printer is in operation to make sure the printer stops on time and prints accurately.
I have some code for controlling the feedrate but the problem is that I'm not sure where I am supposed make these adjustments. In the configuration.h file I see this code: (lines 742 and 753 )
/*line 742*/ #define HOMING_FEEDRATE_XY (50*60)
/*line 753*/ #define DEFAULT_MAX_FEEDRATE {300, 300, 5, 25}  // (mm/sec)

I'm probably misunderstanding something but it seems like this sets the feedrate to a default value which is the same as the maximum.
If the feedrate changes during printing I'm guessing it would be done in Marlin_main.cpp but I'm not sure which part it actually changes. Can someone point me in the right direction here?

The feed rate is set by the g-code you provide, why not just set the printing feed rate lower?  The only thing you are going to change in the firmware without modify it is the max and homing feed rates.

You can change the maximum allowable feedrate in Configuration.h, but the actual feedrate that is used isn't determined by your firmware. The feedrate is specified in the G-Code file. A command like
G0 X10.0 Y15.0 Z3.0 F9000

indicates a move to (10,15,3) at a feedrate of 9000 mm/min. If F is not specified, the last used feedrate is used.
You just have to provide the appropriate G-code commands with the feedrate you want in them. There's no reason to modify the firmware to get a different feedrate.

So then would the feedrate need to be the same for all x,y and z axes? Also are you familiar with which part of the Marlin_main.cpp is responsible for reading the commands from the G-Code file?

No, the feedrate for the individual axes is calculated so that the total feedrate is 9000mm/s (e.g. euclidian distance between points divided by time for move equals feedrate). If you move from 0,0 to 2,1 the feedrate for X will be two times higher than the feedrate for Y. I'm not sure what you're trying to achieve, but changing the firmware probably isn't the right option. If you insist, you should probably be looking at the prepare_move function.

You can't set the feedrate for the axes independently because then one axis might reach its destination before another does. You want a move from X,Y to X',Y' to result in a straight line. Therefore the feedrates depend on each other.

It seems like you might be wanting to look at the steps per mm line.
#define DEFAULT_AXIS_STEPS_PER_UNIT

This line is where you calibrate the number of steps per mm. To calibrate, mark a point along an axis, then move that axis something like 100 mm. If it didn't move 100 mm exactly, make a change
(how far it moved)       (how far it should have moved)
------------------   =   ------------------------------
(current steps/mm)         (new steps/mm) --> find this

You have the  lines to adjust the feed rate.
The first one (line 742) is relevant to the maximum feed rate XY while homing (not during printing). I think this is not an issue in your particular case and you may leave it as it is.
The second one (line 753) is the feed rate while printing for XY. Particularly the numbers in the brackets refers to ( X, Y, Z, E). If your printer is moving it may affect XY more than Z and E. So you may try to adjust the first two numbers.
Due to the very specific situation is impossible to give you a feed rate based on calculation because you are dealing with external accelerations caused by the mobile situation. You will need to try and adjust it until you get right.
Another setting that may also help you to compensate the external acceleration, if any, is the acceleration of those two axes.You should find two lines like these:

#define DEFAULT_MAX_ACCELERATION      {1500,1500,50,250}
#define DEFAULT_ACCELERATION          1500    // X, Y, Z and E max acceleration in mm/s^2 for printing moves

However the acceleration of the axes may impact on the quality of the printing.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Using CAT6 cables for 3D printer motor / sensors / fans
I'm considering using CAT6 cables to connect my printer's extruder assembly to the control board. They seem like an elegant solution, but I've read conflicting opinions online on whether or not this would be feasible.
I would like to know if CAT6 cables can handle the required current, whether I should be worried about electromagnetic interference or other problems, and how I should pair up the wires. Cable length would be 30cm max.
Here are the relevant parts:

E3D heater cartridge (2 wires)
E3D thermistor cartridge (2 wires)
30mm hotend fan (2 wires)
Z-axis auto-leveling probe (3 wires)
NEMA 17 extruder motor (4 wires)
50mm part cooling fan (2 wires)

[cable A]  I imagine I would use one CAT6 cable for parts 1-4, which form a logical unit (and in the future I might combine them into a removable module). I've been given to understand that power for the fan can be spliced from the z-probe or heater cartridge, so 8 wires should be enough.
[cable B]  I would use a second CAT6 cable for parts 5 and 6. There will be two spare wires, so I could potentially double the bandwidth for the motor.

Don't forget about stranded vs solid.  Solid wires will break quickly in moving applications.

The ampacity question is not completely answerable because CAT6 does not specify wire gauge, so the current limit will depend on the specific gauge you get. CAT6 can be anywhere from 22 AWG to 24 AWG, and depending on who you ask this can be good for as much as 7A or as little as 0.5A. Given that you will have a bunch of wires in a bundle, this may cause them to heat up more than if they were in free air. For the steppers (1-2A) a single wire should suffice, but for the heater (around 3-4A) you might want to double up.
EMI will likely not cause any problems regardless of how you wire things up. CAT6 cables have the wires twisted in pairs of 2. Some people recommend to take advantage of these pairs: the +12V and GND of the heater should use a pair, each of the two coils of the steppers should have their own separate pairs. The reasoning behind this is that with equal current flowing in opposite directions in each wire of the pair, the generated electromagnetic fields will cancel out.
Twisted pairs are usually used when dealing with multiple pairs of wires that are carrying high frequency signals that might affect each other. The main concern for crosstalk in this application is if the stepper motor might cause the endstop to be erroneously triggered, but this is only a concern during homing when the feedrate (and thus frequency of the signal) is low anyways.

I did this for some of the wiring on my printer, and it's working fine so far. The two cautions are:

At @tom pointed out, the heater is the high current item, so be careful of the wire gauge, and avoid running the wire where air can't circulate well to cool it. Wire ratings differ greatly depending on whether they're in a bundle (poor air circulation) or free.
For the most part I agree that EMI shouldn't be a problem -- but if you switch to thermocouples it might become a problem -- they're much more sensitive, and this might have been part of the problem I described at How to get consistent and accurate readings from thermocouples? (though alternate wiring didn't completely solve the problem in that case).

CAT6 cable by itself is not a problem, it is typically 23 AWG solid core wire which can take you to 4A just fine.  The real problem comes from the connectors you use.  CAT6 usually goes hand in hand with 8p8c ethernet connectors which only have contacts rated to 500mA.
Also typically CAT6 cable is meant to be stationary (hence the solid core wires), so I'd go for something stranded.  McMaster sells some nice cheap cabling that fits your needs, and it's actually meant for moving platforms like a CNC machine.

Good link, thanks! They even have an 8-conductor wire, with 4 heavier power wires and 4 lighter data wires: https://www.mcmaster.com/#standard-electrical-wire/=15gelsa

I've used some cat 6 in one of my printers and just to be safe I used 4 wires for the extruder heat block, 2+, 2-
On the thermistors 1 is more than enough for each +/-.
I also stripped the thick shielding off and used some 'curly' cable organizer in it's place, not the shielding on the wires but the cord. So i could fit 2 cables in slightly more than the same space as one.  You are probably doing this to keep it organized too but this is an option if you run out of space in your wire runs.

I was using network cables, for a new tool head (a stealth burner). I needed 14 wires, so two cables would be amazing, as I would have access to 16 wires, at 23 AWG, with an amazing rate of current for everything I needed.
Observation: Some network cables are 24 AWG, so be aware.
I remade the cable five times, and I am going for the sixth. It always broke something, and I thought it was due to so many mistakes that I made myself. It looks like my big mistake was using these cables for moving parts - they are not suitable, for moving, and will break overtime.
One of the mistakes I thought what that I was using solid core, and then I switched to flexible network cable, but same thing - it just broke on me, for the fifth time.
So this time I will waste a few hours researching for a good flexible cable.
I might be wrong, and I might have made a mistake in another area. I will come back and tell you guys if it's the case. However, I truly believe the cable that I used was my biggest mistake.
Network cables are amazing - just don't put them on anything that moves.

Welcome to 3D Printing! and thank you for your contribution. When you get a chance, please take the [tour] to understand how the site works and how it is different than others.

Thanks for sharing your experience - very interesting. I am (sort of) surprised that the "flexible" (multi-core?) cables also broke.

It would be best to use stranded wire, since the cables will be subjected to constant motion.  The service life will be higher.
Connector current is a issue.  My experiments in years past with connectors is that up to 2 amps it is unlikely to be a problem.  But pin materials and formulations change.
Were this my printer, I would look for commonalities.  For instance, does the thermistor have any direct signals in common with the Z sensor?  Avoiding loops is good, so don't have the wires tied together on each end.  But, if, for instance, the thermistor was connected to GND or VCC on one of the wires, and the Z-sensor had the same direct connections, I would share the line between the sensors.  This saves a wire.
Ideally, the rapidly switching lines would be separated in a different cable from the more static lines.  This requires knowing how the lines are driven.  For instance, the heater could be driven with a 40 KHz PWM signal, or it could be derived with a 1/2 Hz bang-bang signal.  The fans are listed as 2 wire rather than 3 or 4 wire, so rotation feedback may not be used.  The fans are likely to he a high-frequence PWM, which is more likely to interfere with the sensors.
The motors are definitely driven with a high-frequence PWM signal.
If you could consider using 3 cat6 cables, you might use:
Cable 1, pair 1: motor A winding
Cable 1, pair 2: motor B winding
Cable 1, pair 3: hotend fan
Cable 1, pair 4: part fan
Cable 2, pairs 1, 2, 3, and 4: heater, each pair carries the two lines so that everything remains balanced.   One pair could be reallocated in the future if needed, but best to have the current capacity if available.
Cable 3: pair 1: thermistor
Cable 3: pairs 2 and 3: Z-sensor. Double the GND wire, one per pair
Cable 3: pair 4: spare


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Extruder stepper motor problem, what can be wrong?
I bought a self-made Reprap Prusa Mendel 3 printer, modified to be built from cheaper materials, and immediately after the deal I got various problems. I fixed the majority of them, but don't know what the reason of the strange extruder behavior is: The stepper motor is not rotating while extruding filament, it's moving back and forth with small steps instead. I made some footage, Reprap Prusa Mendel 3d printer extruder problem, hoping that someone has met a similar problem before.
If so, please tell me what to do to make it work as it should.
The obvious option while encountering this problem was to slacken the bolt which holds this parts together (in the left bottom corner of the video), but that did not help.
Any ideas are very welcomed. Thanks for your time. I hope this is an appropriate kind of question here.

Your controller board probably requires calibration.
It sounds like, maybe, the extruder's stepper motor is not receiving sufficient current, to make it turn. Or, somewhat confusingly, maybe the stepper is receiving too much current, and overheating.
You don't say which controller board you are using, but regardless, there should be an adjustable potentiometer on the board, next to each of the stepper drivers, or on the stepper driver daughter boards.  Like so,

This potentiomenter adjusts the reference voltage used to control the stepper motor. From this reference voltage, and the resistance of the stepper coils, one can determine the current, which is used to drive the stepper motor.
For the stepper driver of the extruder, you could try turning this adjustable potentiometer slightly, in order to provide more current to the stepper, in turn to provide sufficient torque such that the motor is able to turn. Or, less current to stop the stepper from overheating.
The adjustments can be made whilst the power is on, but a non-ferrous (i..e. plastic) screw driver should be used, so as to avoid short circuits. Also care needs to be taken, when turning the potentiometer, as they have been known to just fall apart whilst being turned. If you are paranoid, then make micro adjustments with the power turned off, and then turn back on to check the behaviour.
Note: it should go without saying that one should never disconnect a stepper whilst the power is on, as both the driver and the stepper motor may be irrevocably damaged.

The photo above is taken from POTs Calibration – RAMPS 1.4.

If a POT is set too high then the associated stepper driver will tend to overheat and go into over-temperature thermal shutdown (to prevent damage to its components). The first sign of overheating is erratic stepper motor behavior. Typically, this can be recognized by the sounds of the stepper motor suddenly losing power (thermal shutdown). If no load or movement is required of the motor, it is hard to detect whether it is over-powered as the driver is barely producing any heat.

and

Conversely, if the POT is set too low, the stepper motor can enter an underpowered state. This can be recognized by a lack of holding torque and a stepper motor that is skipping steps because the necessary movement  requires a higher power demand than the POT setting allows for.

Driver cooling
In addition to the possibility of the stepper motor over heating, it could be possible that the stepper driver is overheating, although the symptoms may be different, to those that you are experiencing. Regardless, you may still find it advantageous to cooler the controller/driver board with a fan that is always on (not temperature controlled).
Additional reading

RigidWiki - Stepper Driver Adjustment, which goes into further detail about the adjustment of the potentiometers, that I outlined above, as well as the reference voltage and the adjustment thereof.

RepRap Wiki - RepRapPro Setting Motor Currents describes a different controller to yours, but goes into the process of adjustment, and description of the reference voltage (which is applicable to all boards):

The wiper on each potentiometer generates a DC voltage that is sent to the chip. This is the reference voltage; it defines how much current the stepping motor driver chip supplies to the motor. The bigger the reference voltage (VREF), the higher the current (A) that the chip will send to the motor. For most NEMA14 motors, the current maximum is 1A, but this will generally cause it to get warm, so a setting of 750mA is recommended. For NEMA17 motors, depending on size, the limit on current is generally between 1.3A and 1.7A. If you drive stepper motors with more current than they were designed for, the motor will get hot, and may be damaged.

Pololu - A4988 Stepper Motor Driver Carrier with Voltage Regulators - this is a very common stepper driver.

MyHomeFab - DRV8825 Adjust Stepper Current goes into the adjustment of the reference voltage, for the commonly used DRV8825, which is an alternative to the popular A4988.

This thread, about non-actuating steppers, may also be useful, Motors, which mentions setting the trimpots and points the OP to RepRap Wiki - Pololu stepper driver board, which, in turn, refers to this thread, Strange stepper behavior and this video, video-2012-02-02-16-37-26.mp4, which describes a jitter in the stepper behaviour.

I've always had a MakerBot, which does not have a potentiometer to set the current. But does the machine have to be turned off to do this properly?

@tbm0115 - I have expanded my answer with an answer to your question as well as some additional info.

@Greenonline Many thanks, driver replacement helped. After that, another problem appeared again, however, but that is a subject for another question.

I also faced similar problem. Mine was a self-made marlin/repetier. The problem was that the motor current was much less than the motor requirement and the axis were not calibrated properly. Giving recommended current according to your motor ratings and limiting your feedrate according to your calibration should work.

If the stepper never turns, even with no filament loaded, it is more likely to be a bad connection to one of the two coils or a bad stepper driver, or a bad motor.
Seems to be a frequent enough problem that they supplied a spare driver with my machine.
Perhaps you can try swapping drivers to see if the problem follows the driver. You can disconnect the motor with power off and measure the coil resistances with a multimeter to see if they are sensible, which will weed out a bad harness, connector or motor.

You make a good point about the bad connection, however, this is not the issue experienced by the OP. The stepper does move, as can be seen in the video, which is linked to in the question.

in my case there were random shifting and I found the motor is getting very warm .. so when I lowered the driver voltage it didn't get as warm and the skipping and shifting just stopped.


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Printing objects with holes using M3D Printer
I am using an M3D printer and loaded an STL design with holes in the middle:

However, the output is an object without holes (so I stopped the printing):

What can be done to be able to print with holes?

Have you tried letting it print a few more layers? It is very common that printers use the first few layers to create a raft, which will make the model adhere better to the bed.
I believe this illustration from Simplify3D displays this well:

Case 1:
There may be an issue with the precision of the print nozzle, not being able to fully articulate the hole. That is to say, the printer is trying to print it with holes, but the material is filling in that area.
Try increasing the size of the hole. Granted, it is not an exact process but there may be an inner hole diameter that winds up mimicking the diameter you're looking for after the material extrudes.
This case could be rejected by nature of the printer depositing straight lines through the center diameter of the cylinder's base.
Case 2:
There may be some discrepancy between the file's appearance and the file's information.
If you downloaded the file from somewhere like ThingiVerse, try designing the part yourself if possible. If you designed it yourself, overwrite the file with a second version.
Case 3:
If downloaded, verify that the center hole is extruded though the entire thickness of the part. It may be that it's extruded most of the way through and there is a sealed bottom layer.


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M4 screw and nut for 3D printing?
Does anyone know where I can get a free 3D design (STEP or STL) of an M4 Screw and nut? I have found only an M3 on Thingiverse: M3 Bolt by Kaleta.

You can get a model for nearly everything McMaster-Carr sells from their website.
M4 Hex Head Screw - https://www.mcmaster.com/#91280a140/=15dmpx8
M4 Nut - https://www.mcmaster.com/#90592a090/=15dmqjy
The options to download models are to the right of the drawings.

NOTE: the site does prohibit use of these models for direct printing.

You shall not use a CAD model to engage in 3D printing or other
  fabrication of the object depicted in the CAD model for any other
  purpose. You shall not otherwise redistribute or make available the
  CAD models (or any design drawings or prototypes that incorporate
  them) to any third parties, including third parties in the business of
  selling products similar to the products sold by us.

The thing you linked to describes itself as being generated from a parametric model:
http://www.thingiverse.com/apps/customizer/run?thing_id=193647
To generate any different bolt or nut, you will need to identify the correct dimensions for not only the thread (where hints exist in the customiser), but also for the hex head. These are obviously less critical to define than the thread.
Once you have generated a custom model, you can share it and answer your own question.

Actually, I think that the  owner of the linked item created the matching customizer page.  You need to start w/ a SCAD dwg before you can create a Customizer, so far as I know.  PLease add info correcting me if I got this wrong.

A 3D printer does not have the necessary resolution to create a functioning screw thread. I suggest you print the hole (for the nut) and the shaft (for the screw) in oversize and use a tap and die set to make the threads.
You must print them out of PA12 nylon obviously. Due to the size, warping will not be an issue.

Maybe you should add that this is true for smaller thread sizes, I've printed larger threads that worked fine. SLS can even have a higher resolution.

I've printed an M36 once, so yes. But as long as you can cut the thread, you should cut it, not print it.

You could also apply a scaling factor in your
slicer to make a downloaded object larger or smaller. An M3 model scaled at +1.333 would produce a working thread with a nominal 4 mm OD.  As noted in the comments below, a different scale factor might be needed in the axial direction if exactly matching the pitch of an M4 thread is required.

That's not true. You'll want to scale it with a factor of 1.33333 along the thickness of the screw, but a factor of 1.4 along the length of the screw. Please study this chart and fix your answer: https://www.carrlane.com/engineering-resources/technical-information/design-standards-and-engineering-information/inch-and-metric-thread-standards
The threads of an M4 screw are 0.7mm apart. The threads of an M3 screw are 0.5mm apart. The threads of an M8 screw are 1.25mm apart. So an M3 to M4 scales 4/3th along it's width and 7/5th along it's length.

It's true that the thread resulting from scaling all three axes at 1.333 would not exactly match the pitch of a standard M4 thread. It would, however, produce a working set of threads as long as both male and female components were scaled at the same factor.  If attempting to make a true M4 part to mate up with a standard M4 component it would be necessary to apply a different scaling factor in the axial direction to duplicate the standard M4 pitch.


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MINTEMP error after crash
I just got my HICTOP Prusa i3 Aluminium frame printer and finished putting it together. After setting it to preheat, I realized the bed was not level - I adjusted it and accidentally caused the head to crash into the bed.
It sounded like something popped, and the printer restarted. It is now showing a MINTEMP error message, and both bed and hotend temperatures read 0°C.
The only visible damage is that a thin layer came off the printbed - After testing with a multimeter, I realized that the metal under this layer is connected to power. As both the bed and hotend were heating, I believe I may have caused a short.
Replacing the thermistor on the hotend with a spare did not solve the issue. I tested the thermistor on the printbed with a multimeter, and it seems to be working correctly (resistance value around ~200 kΩ at room temperature).
Which leads me to believe that I may have damaged the control board. What do I do?
Note: This is not a firmware problem as the printer was getting correct temperature readings before that. Also, I have a second extruder thermistor port that is unused. If I did damage my board, could I edit pins.h and configuration.h to use this port instead, and completely disconnect the heated printbed?

After replacing the control board, it now prints flawlessly. Apparently,I really did damage the control board...

Were you able to determine what failed on the controller board?


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Printing screws - is the output usable? (M3 or M4)
I just want to ask if anyone has successfully printed a screw (M3 or M4). Is the printed output usable as a screw? What printer is capable of printing screws? I am using an M3D printer - is there a configuration to successfully print a screw that is usable?
Can anyone share a picture of the best 3D printed screw?

It's better to print a cylinder and then tap it.

@FarO: Disagree strongly, especially if you're printing the axis in the XY plane. The zigzag walls and how the shifted versions of them in each layer interlock are far stronger than a smooth cylinder printed in any orientation, even before you start cutting into it with a tap.

@R..GitHubSTOPHELPINGICE good point, but interlocking requires parts of the thread to be smaller than the average one, areas which will have a weaker resistance. So it will lock better, but the surface which will then hold will be less than the optimal one. Also, screws don't rely on interlocking but on tension when the nut is tightened. Or am I making a mistake somewhere?

@FarO: I don't understand what you're saying. Interlock was probably a poor word choice on my part but I'm not sure what the right word is. The point is that you have continuous uncut extrusions and almost nowhere the tension is along their length and nowhere it's pulling layers apart. Instead the tightened nut presses everything together more.

On the other hand, if you print a cylinder with axis in the XY plane then tap it, all of the outermost extrusions will be cut repeatedly at spacing matching the pitch, only attached by their bonding to the next wall inward and some small surface with the (also cut) walls above/below, and the tension from the nut tightened on them will be encouraging them to compress along and break off from the next wall inward. Simple inline ascii art: /\/\/\/ vs -=-=-=-=

@R..GitHubSTOPHELPINGICE I see what you mean. My point was that if you tap, you are sure that you will use all the possible area for the thread (area measurd on the section perpendicular to the axis), while if you print it in its final shape, either you use all the available area (but then it's like tapping) or you have spots where the print does not fully cover the available area, and you have less material. This reasoning applies both to XY and to XZ prints. It's just a way to maximise the amount of plastic which will hold.

@FarO: I see. I think that's best handled (see My Tech Fun's video linked in my answer) by printing the threads with slightly negative clearance then using a tap aligned with the printed thread, so as to remove well under a whole extrusion wall at all points, achieving both the maximum contact surface area and ideal extrusion/layer structure.

well... it's hard to imagine printing M3 or even M4
I haven't try but I haven't because I'm pretty sure it's not possible (on my printer of course)
but some time ago I've tried M8 which is of course way from your needs
it was printed on 0.1mm layer height
it went ok into the nut without any problems but the strength is not very high I suppose
I know the quality is poor but even such bad photo shows issues

I'd say it's not just your printer; no FDM printer is capable of doing stuff as fine as M3 or M4.

Yes. This question and most of the answers are old, and 3D printing has come a long way in the past 4 years or so. Alexandre Strube's bumping with one up-to-date answer inspired me to take another try at it, and my first attempt was an overwhelming success.

Bolt printed in horizontal orientation (with support), nut vertical.
Wall line width reduced from 0.4 mm to 0.3 mm (still 0.4 mm nozzle) - most important for the bolt or the thread profile is not achievable.
Layer height 0.12 for bolt, 0.08 for nut (to give nearly 10 layer per revolution)
Both offset 0.045 mm from ideal thread profile (at M6-M8 this is about the maximum allowable by ISO standard; at M4 it's surely excess but extrusion roundness of FDM probably compensates entirely anyway).
100% infill, achieved with high wall line count rather than zigzag fill

The nut and bolt fit tightly but can be turned by hand (if your fingers are small enough) with some force.

These were printed in cheap PLA on an Ender 3 with entirely stock hardware, but upgraded controller board (SKR mini E3 V2.0) and firmware (presently using Klipper).
As for whether they're usable, My Tech Fun has a video testing the strength of 3D-printed bolts in different orientations. His tests were of M10, but the horizontally-printed one was able to hold over 140 kg in a pulling test, making it (especially with multiple bolts) suitable for serious applications.
Since the question mentioned M3, I went back later and figured I'd go even smaller and give M2.5 a try... and it worked! This is pretty surprising considering the pitch is just over the nozzle size, but with 0.2 mm extrusion widths and 0.08 mm layers it came out usable:

That looks nowhere near as good as with a properly sized nozzle for the extrusion widths, I believe the "extrusion width < nozzle diameter --> inaccurate flow" still stands.

@towe: which part are you talking about? I had an error in priming setup when I did these that messed up the heads a bit.

I just did.
I printed a 4 screws at .2mm and 20% infill. surprisingly, all screws worked with a plastic m4 nut I had from china (not 3d printed). The project itself 1 tells to print at 100% and 0.1.
When I started screwing the 4th one, I pushed the tool badly, and the screw head popped off.
After reading this thread, and experiencing what I just said above about the screw's head, I'm printing one more, this time at the maximum resolution and maximum infill. I'm also printing a nut to compare to this.
Even the ones with plastic flying around them worked well (see picture).
1 https://www.thingiverse.com/thing:2591857
Ps: apparently the person can't make hexagons. I will redo the heads in proper hexagons, as well as the little wrench when I have time.

It looks like you were bit by Cura's bad default Maximum Retraction Count and Minimum Extrusion Distance Window causing skipped retractions. Setting the window to 0 fixes it.

At 0.2 mm layer height it's really surprising these work at all. Assuming M4x0.7, that's only 3.5 layers per revolution of the thread, and the thread is almost certainly wide enough (just due to layer height) to be out-of-spec. Normally you want at least 5-6 and preferably 8-10 layers per revolution (e.g. at most 0.2 and preferably 0.12 for M8x1.25). If you're getting by with less it's probably a matter of non-rigidity of the bolt and nut; with a metal nut, threading it on might actually cut a fix in your print. However..

..it's nice that you bumped this question! Things have changed a lot since 2016, and it's nice to see how something everyone thought was impossible then is actually doable now, even on a $200 printer. When I saw this bumped, before reading your answer, I took it as a challenge to print some, and I might still do that.

I've had success printing pins at that size, but not screws. At that size the pins were also exciedingly suceptible to stress, ie easy to break. At that scale the tolerances are a bit tight when printing that small and there will be small variances in precision with most printers. The best example of this is to try to print a lego piece, they dont snap together, some are slightly to big, and some are slightly to small and sometimes they will break.

Its just not possible on a FDM machine. for example using a layer thickness of 0.1 which is standard there would only be 5 layers of material between each peak (the pitch) for a coarse M3 and a fine M3 would not even have four layers (wikipedia on ISO thread) which is just not enough layers to resolve the required shape. The tensile strength of such a bolt even if you could print it would be abysmal.

Not very likely unfortunately.
M3D nozzle diameter is too wide to be able to print something that would print reliably, not to mention any FDM machine won't have the precision to build good threads. even 0.05mm layer heights won't run very well.
I've tried on a Form1 (SLA style printer) and even that set at it's max resolution wasn't able to print clean threads.

Vertically printed threaded bolts generally work better than you might expect, because (1) the layers are nearly parallel to the direction in which they have to slide, so the bolt can turn smoothly, and (2) when a typical bolt is sliced, the resulting layers are just circles, which are about the least problematic shape you could print.
Also note that, especially if you're printing a bolt to use with a metal nut (or vice versa), then as long as the thread is close enough, it will end up being crushed / sheared into the right profile; it's a bit like how you can drive a screw into timber without having to tap a thread.
In principle, the pitch of a printed bolt could be very fine; as long as the layer height is less than half the pitch (i.e. the Nyquist limit), and the spacing is correct, then the threads will engage.  So if you can print 0.1mm layers, you have enough detail for M1 or smaller.  Of course you're not going to print a bolt that small, but the point is, the limit is not resolution, it's the strength of the print.
The horizontally-printed bolt in @R.. GitHub STOP HELPING ICE's answer is impressive – if you can print that, then that's the answer.  But even if you can't, you could definitely print a horizontal 3mm diameter cylinder, and then use a die to cut the thread on the finished part.  It's not a "pure" printed solution, but you can get a cheap tap-and-die set from any auto parts store for less than the cost of a spool of filament.


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What is the MakerBot Grip Surface lifespan?
I've done a few prints on my MakerBot Replicator+ now and I'm curious if anyone else knows what the typical lifespan is signs of degradation are for the grip surface tape?
I'm used to using Kapton tape in the past. Which will bubble, scratch, and even tear at times, indicating that the tape should be replaced. However, this new MakerBot "Grip Tape" is a very stiff, precut material, with extruded plastic anchors to help evenly spread the tape and keep it secure on the build platform. The tape also has texturing on the top face that helps with adhesion.
So, this new tape seems somewhat impervious to bubbling, scratches, and tears. I'm curious what signs I can look out for that indicate that this new grip tape needs to be replaced.
Obviously the tape isn't a permanent solution, so what are some signs that the tape should be replaced?

I use the FFCP grip surfaces. Once I realized I could clean it with Alcohol.. a single pad will last me till my tools have cut too many holes. May be the same for makerbot.

There's no quantitative formula for the lifespan of any grip material, be it tape, glue, or PEI sheet.  If you find a lack of stiction and it's not due to small changes in the Z-origin (50 microns can make a big difference in the way the first layer grabs the bed!), then replace the tape.  It's cheap.
Just to be pedantic, torn and scarred tape should be replaced :-)

Your answer is a very good general break down. However, I'm used to kapton tape. Which typically bubbles, scratches, and tears, indicating that it should be replaced. But this specific MakerBot grip tape is stiff and textured and will not encounter the same signs. So, I'm more interested in what those signs are. I'll try to reword my question. Thank you for your response though. +1 for great beginner tips


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What resolution (pixels/mm) should I use in SVG for CNC?
I am planning a mechanical 40% keyboard build and are coincidentally on the home stretch of a homemade CNC project.
The only thing the CNC needs to do for the keyboard project is to drill 7*48 holes. So what I need to do now is layout those holes in SVG. Therein lies the question. What resolution should I use for the SVG? I want to space the center of the keyboard switches 19 mm apart. An online pixel to mm converter suggested that 72 pixels is exactly 19.05 mm (which actually is what Cherry MX says should be their spacing).
Now, I do understand that this really doesn't matter, but I am curious as I am new on CNCs and was suspecting that there is a number that will "just work".
EDIT:
For example, if I where to print the template (SVG) on a regular printer, what pixel to mm ratio should I use so that it would come out the size I want?

I found one of those printer things that puts ink on dead trees and tested to print a simple SVG file.
<svg xmlns="http://www.w3.org/2000/svg"
     width="400px" height="800px">
  <rect x="10" y="10" width="72" height="72" fill="#999999" />
  <rect x="10" y="100" width="378" height="378" fill="#999999" />
</svg>

As I suspected 72 pixels came out pretty much exactly 19mm. (72/19.05)*100~=378 came out 100mm.
Given this I am going to assume that 72/19.05 is the de facto best pixel to mm ratio to use for CNC projects.
EDIT:
Found this documentation: http://w3.org/TR/SVG/coords.html#Units
<svg xmlns="http://www.w3.org/2000/svg"
     width="400px" height="800px">
  <rect x="10" y="10" width="19.05mm" height="19.05mm" fill="#999999" />
  <rect x="10" y="100" width="100mm" height="100mm" fill="#999999" />
</svg>

Much simpler to use mm as units right away

SVG is a vector-graphics format, there's no particular reason it can't scale arbitrarily. Presumably the CNC software will allow you to select the scale of a pixel? If so, pick a scale that makes the math work out easily (so some integer number of pixels per millimeter). If not, it's probably documented somewhere for the specific tool you're using.


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How to use E1 as E0?
Like many people, I have burnt the pins in the micro-controller connected to the E0 motor - the E0 motor is not working anymore and I need to print tomorrow! I need to control the extruder motor with the working E1 pins. How do I change this in firmware?
I tried to change to the pins in `pins_RAMPS.h" but it was a complete fail, the motors that i tried to change didn't move.
I have a Arduino Mega + Ramps 1.3 in "Extruder Fan Bed" configuration, I use Repetier-Host as host and Marlin as firmware.

How did you find that Arduino pins were burnt? Have you tried spare motor driver?

@MikhailZ Yes definitely ! I swapt the drivers to test them, and I always replace the bad drivers with new/repaired ones.

Changing pins_RAMPS should work. You must have done something wrong when trying it.

To elaborate on this answer of Thomas S, a more detailed description of swapping the pins is found in this 3D.SE answer. Please vote and accept an answer (we want this community to get out of Beta stage), thanks!

I would change the pin assignments by swapping E0 and E1 in pins_RAMPS.h.

A more detailed answer is found here.

As a quick and dirty solution you may try to enable two extruders in configuration file, re-upload firmware, and then edit your GCODE file to replace all E0 references with E1.

That's a really good idea. It should be possible to have the firmware do it. Or there must be a script that can be ran... But it doesn't seem this firmware is all that great. I would suggest a different firmware if it doesn't do what is needed.


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Unable to load G-code in Ultimaker Cura
I have generated a few 3D prints in G-code using KISSlicer and Slic3r, but when I load them into Ultimaker Cura I'm unable to get anything. The number of layers says one but I cannot see anything and print option is not working. I have viewed these G-codes online and they are fine. I'm using a Lulzbot KITTAZ with v2 toolhead (hexagon) and I can print only using Ultimaker Cura. Please tell me what the reason for this is.

Cura prior to version 2.5 won't load G-code, it will only export to it. You could use something like Repetier host to open the G-code and preview it though.

Update:
Cura 2.5, and higher, does load and print G-code.
(The support was added April 19, 2017.)

Cura prior to version 2.5 does not take G-code as an input. I'm not sure what you mean by "print only using Cura." Don't you have a SD slot on your control board? For that matter, why can't you drive the USB port from Slic3r?
Remember: G-code is the equivalent of "compiled code," the raw commands which drive the printer, while STL or OBJ, etc., are the "source code," which you edit to get the shape you want.
I've looked at a few apps which will render a 3D image on your computer from G-code, but I don't know off-hand of one which will "decompile" into a STL or mesh file.

The printer does not have an SD card slot. Is it possible to print using slic3r? I always thought it was only for slicing.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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Resources/methods to construct STL files using disparate parts using OpenSCAD
What resources or methods would OpenSCAD users suggest to piece together disparate STL files?
I'd like to take an existing STL model-library of STL parts (head, torso, arms, legs) and make it a Thingiverse OpenSTL maker, similar to the castle generator and/or the puzzle generators available.
This way, users can generate a custom model using the designated parameters and download the model for printing.

Are you restricting yourself to using OpenSCAD to accomplish this assembly process?

I am currently restricting to OpenSCAD because I can import my OpenSCAD 'framework' and parts into Thingiverse and make this tool easily accessible to the open-source 3D print community. I realized I wasn't clear enough in my original post about the concept - I'll clarify.

That's an interesting and admirable objective. I'll drop back to my answer posted below and suggest that the parametric manipulation of translate and rotate may give you the desired results. You would have to be certain to create appropriate parameters to be passed to the modules when combined. If you create a figure of x total height, the individual components would translate to x, x + part 1, x + part 2 or something similar. I like OpenSCAD, but I'm a mediocre coder. Perhaps your strengths are greater than mine.

I think that the project hinges on fairly standard dimensions. If I can build a set of OpenSCAD files that have a series of fixed positions, and I can prepare a series of model parts that can (essentially) be modular, this will work.

I'll offer up the following options, without waiting for an answer to my question.
One can import a specific STL file into OpenSCAD and perform rotation, translation and scale, but it would be "clunky" as you'd be making miniscule changes to the parameters for those actions. Each imported object would have to be manipulated individually via the changes in the code. If your imported objects have quantifiable dimensions, that is, if you know specific measurements, you would have an easier time of the project.
If you are not limiting yourself to OpenSCAD, I'd recommend the easy-to-use MeshMixer. I recently "assembled" the parts of a cosplay "weapon" for a friend. All the parts were individual STL files and were positioned in 3-space using MeshMixer to make the parts appear as if the project were printed and assembled.
The transform tool in Meshmixer is a graphic three-arrow/three-axis manipulator icon. Grab an arrow tip and the model moves in the direction of the drag. Grab an arc between two arrows and the model rotates. If you want five degree rotation increments, move the mouse outward after the grab and get a calibration circle. When the mouse is on the circle, you get snaps to five degrees. If you need smaller movement, move the mouse out even farther from the center.
The 3-space presented in Meshmixer gives you the ability to align pieces/parts in all three dimensions, to your satisfaction. There is a model hide and a model-ghost feature as well, to assist the placement.
I expect that one could use a program such as Blender, but the learning curve is more like a chasm or cliff-face.
One could use an engineering-focus program such as SolidWorks, Fusion 360 and so many others, but I think your head, arms, legs, torso reference means you aren't using orthogonal models more suited to those programs.
Meshmixer, like OpenSCAD is free. I use both and approve this message.

That's a fantastic idea - my actual concept is deeper in design, it's a customizable figure generator based on a STL parts library.

I hope you'll toss a link here when you get the coding figured out.

Certainly shall!

While this is probably (?) not suitable for the Thingiverse customizer, OpenSCAD has a decent Makefile support. In a project I am currently working on, I have a set of include files that start off with some configurable parameters, then provide some computed dimensions based on these parameters which are then used to render the individual components. Through the Makefile/.deps mechanism, the system keeps track of which component .scad file is influenced by which settings file and automatically rebuilds the parts that might be affected. (Note that the .deps files are not checked into the repository.) In the assembled model, I merely import the individual rendered STL files (in my case, always through some wrapper module for coloring and BOM generation).

I'll have to investigate a bit and find out!


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Unidentified problem in printing
I have printed the XY resonance, Z resonance, bridging performance and the negative space tolerance test, from Makezine (can be found here), and I have encountered the following errors in the prints.
Z resonance test:
The layers are shifting as the height is increasing.
 Click Here for larger image
XY resonance test:
There is continuous extrusion problem that is occurring on the same side, I have printed it a few times and every time I'm getting the same problem at the same side.
 Click Here
 Click Here
Bridging performance test:
Has severe infill drop, the test recommended printing without supports.
 Click Here
 Click Here
Negative space tolerances:
Except for the 0.6 pin, I was unable to remove any of other pins.

I'm using a Lulzbot KITTAZ printer with V2c hexagon tool head (0.35 mm). These are the settings that I used while printing these objects:

Layer thickness: 0.1 mm
infill: 20%
Printing temperature: 230°C
Printbed: 85°C
Bottom and top layer thickness: 0.1 mm

Please provide suggestions on improving the printer performance.

As StarWind pointed out, there are many different questions in this one question. Since you are new to the Stack Exchange network, I would recommend that you take a look at the Help Center. Also, please consider creating new, separate questions for the following topics that you appear to be experiencing: ghosting, Z-Axis straightness, bridging, and ceiling voids. Thank you also for providing pictures, as this greatly helps troubleshooting and welcome to Stack Exchange! :)

Thank you for the photos ( though some of your links are not working right) updated my answer a bit.

Okay so one problem at a time.. You have several issues.
1 You will likely note while it prints, the pillar will almost catch and sometimes twang as the layers get higher and higher. Issue here is you are over extruding a bit and the head is dragging on the print. Add some leverage and then you get this strange pattern. Letting it cool more between layers or by adding a fan will also help. A small pillar like this will not have much time to cool.
Or it could be that your Z is not straight. Whats the name of this test? Right the Z resonance test. Check out your smooth rods and screws and see if they are perfect or not.
2 Hmm maybe some oozing / over extrusion. I mean it will never be perfect.
3 Looks good to me. You are printing PLA not ABS?. Looking at your temps and I hope you are doing ABS.. Which probably should bridge a bit better. That said even my highly calibrated machines would have a hard time with a bridge like that. I've been at this for years. Fan will help. Different material will help. I mean you are printing over air. That said 1-2 degrees will make a difference. Try slowing it down. Try lowering temp. Add that fan. Remember every spool will need a new perfect temp. Even a different color will need calibration as the pigments change the temperature profile.
Last over all, simplify 3d seems to really help. I rarely spend time calibrating these days. Albeit they cost a lot. no affiliation.
I also like this visual guide
http://reprap.org/wiki/Print_Troubleshooting_Pictorial_Guide
EDIT. I see you have added more photos!
For the Z axis, I stick with my first assessment. Over-extrusion. Or it could just be getting too hot the higher you go. Maybe add a min time between layers option if your slicer supports it. Fan is good too.
XY resonance.. Tricky tricky. My research shows this can be solved by using a different slicer program. You will have to research how to solve this with your preferred program. Maybe try to tighten belts, and tweek your oozebane settings. I would also play with acceleration and Jerk at the Firmware level..
Last one, Bridging. You have bigger issues than bridging. All that shows is you don't have temp dialed in 100% yet. 230 might be high.. 85 for PLA would be high as well.

I would also suggest backing up and doing a single wall test and start a new question if you still have issues.


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3D printed mold techniques for long and short term usage
3D printing can be used to make injection molds of unimaginable complexity but which kind of 3D printing process is suitable when?
Suppose that a part is to be made using injection molding in large quantity for an extended period of time, what Additive Manufacturing (AM) process will be the best, such that the mold does not give way too soon?
Also, suppose that the part to be made is custom and only has to be made in small quantities - that is to say that the injection mold will be used limited number of items and then thrown away - which is the best AM technique then? Best in the sense of economic feasibility, lower cost, lower capital investment etc.?

This is one of those questions that qualifies as too broad to be answered in a practical manner. Even the question is segmented into so many parts as to indicate clearly how broad the scope. I suggest to focus on specific examples with easily determined problems for which solutions can be described.

Yes, this is very broad. That said...
For high detail you want SLA. i.e. jewelry. If you just want a prototype of a mold, you can do a standard FDM style printer (95% of printers are FDM, and that number is a guess)
Really, you should be asking what material you need for your mold, but you can open a second question for that.
Do more research on injection molding. There is a great deal of information on how molds are made, i.e. How It's Made Plastic injection molds.
You will see there is a vast difference between a plastic, or silicon, mold and an injection molding machine. You are thinking that injection molding as a single mold, when it is really it is a system composing of several pieces of heavy duty machinery that can pump out hundreds of items a day automatically. However, it usually starts at 20k USD for the tooling for injection molding. Your costs could be a fraction of that or could be several times that. This is just a generality. So, if you are making 100 units you won't want to go down that route. For 10,000 units, on the other hand, it would be acceptable.

Just to clarify... the 20k - is that cost (i.e. $20,000), or quantity (i.e. 20,000 units)?

$20,000 USD which is the cost. It is also a random number based off a general knowledge. It could be half that, could be 10 times that.

It is also worth mentioning that my local hackerspace has offered classes on injection molding. One by you may as well.

Stratasys offers a 3D printing system specifically for producing injection molds. They claim their Polyjet/Digital ABS line of printers can produce prototype injection molds good for 10-100 shots of the same mold and that the material can be used with regular injection molding machines.
Of course, the molds still wear out quickly and are only suitable for prototyping and/or extremely small production runs.

Injection molds generally require tooling and are not usually cast from 3D prints.  Depending on the size of your part - costs can easily skyrocket to over $60,000.  The price per part is sometimes lower than other methods.  Other possible methods (depending on the part) are Thermo-Forming, Vacu-Forming, and different Casting methods - sandcasting (investment casting), flexible casting (rubber, urethane, and alginate), and hard casting (printing mold negative).  Some have immediate use of 3D Printed parts...others have work flows in place to convert your files for use. You can print a mold negative, prep it, use mold release, and cast shapes from that mold... certainly the casting material would be flexible or the mold would need the proper relief-  But it is certainly possible.


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3D printers for ceramic clay?
Are there any extruders and printers that do a good job with ceramic clay?
I assume the clay has to be fine grained and with enough water added to be able to be pushed out through the extruder's nozzle. I also assume the print speed would have to be arther low for the already printed layers to gain stability before printing the next layer. Perhaps some extra equipment on the printer to spped up this drying process?
At the same time, the print speed can't be too low: if the bottom starts to dry enough to start shrinking, the object will crack.
Also, some solutions I've seen tend to result in rather low resolution/thick layers, which is negative.
So, what equipment is "out there"?

What you are looking for is the Frostruder style extruders.
Here is a link to a thingiverse file for it.
You honestly cannot expect fantastic results but it will get the job done! There are many other types. Quality will depend on the size of the point. However with something as high viscosity as clay I would not expect you to be able to push the quality very high.

The Froststruder! lol This was one of my favorite attachments along with "The Unicorn"! Old-school MakerBot was pretty awesome...

Here is an open source clay extruder from standard parts, that i designed
https://www.stoneflower3d.com/projects/clay-extruder-prototype/
Different designs of 3D printers, pumps, extruders etc. for clay are posted and discussed in the Google Community "Make Your Own Ceramic 3D Printer", driven by Jonathan Keep (https://plus.google.com/u/0/communities/109375785524125994679).

That's a really cool design

I cant speak for the quality or type of clay, but there are several designs out there that print in clay. Here is the first one that popped up on my google search.
http://www.wasproject.it/w/en/wasp-launches-the-new-professional-clay-extruder/


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Extruder clicks
I have Prusa i3 derivative with MK8 extruder and Marlin 1.1RC8 as firmware. I already reduced the default speeds as well as the accelerations. But sometimes when trying to print with BQ PLA filament (220°C), mostly during filling areas, my extruder clicks. The below screenshot of Slic3rs Layers view shows the clicking "lines".

What settings I need to change to avoid the overextrusion in this case?

Are you sure it clicks exactly when retracting? Clicking mostly indicates extruder is unable to advance filament. In your case if it sounds when more filament is required (like filling areas), then you may try to reduce printing speed in such areas or increase nozzle temperature.

You are right. On a different object it becomes obvious that the clicking occurs when performing solid infill, even on a long "line". I'm using Slic3rs default values for the speed, so 20mm/s for solid infill (normal infill 50mm/s).

If reducing speed won't help, then there is something else blocking smooth filament extrusion. With PLA you are most likely using cooler. Try reducing cooler speed for areas with 100% infill. Otherwise look at @rwinscot answer.

First 220c for PLA? You must be running at record speeds! But really a video would be a lot of help :-)

@StarWind: no, this PLA is specified to use 220°C. I'm using speeds of up to 50mm/s for inner perimeters.

@ThomasS, will the print continue fine afterwards? If it does, this may simply be the issue of a too large nozzle trying to squeeze infill into a gap smaller than itself - something many slicers struggle to handle elegantly.

Yes, the prints are just fine.

I've tried to reduce the "Extrusion multiplier" from 1 to 0.95, but that caused gaps. Now I've minimized the clicking by setting the Slic3r option "Infill before perimeters" on the "Print Settings > Infill" page.

PS: If the same amount of plastic still gets extruded - just in a different order - won't all parts will grow slightly in size? Also, I suspect that perimeters usually are printed first in order to get a smoother finish. Is this according to your experience? Thanks for sharing your answer. :-)

Yes, I think, that the objects will slightly wider. I don't know why usually the perimeters are printed first - can't say they look worse now.

so, here is my theory: There is the slic3r setting "Combine Infill every: X layers". What this will do if it's set to 3 for example is first print three regular sized layers of perimeters, and after that print one fat infill layer that is 3 times the layer height (that's a speed optimization). Of course this is more filament that must be pressed through the nozzle and may cause clicking. However, if you FIRST print the infill, then this optimization cannot be performed (so infill will always be printed at the set layer height rather than at a multpile of it)

Extruder 'clicking' is an audible indicator that the teeth on the hobbed gear are slipping... determining if this is a symptom or a problem is where things get tricky.
Not so sure about adjusting feed rate - as this will impact the entire print and may introduce other problems. Measuring the dimensions of a sample print with a set of calipers is a good way of identifying over/under extrusion.
General maintenance items perhaps?

Thermistor: Nozzle temperature measurement is dependent upon the precision of the thermistor and how well it is attached... 5% drift at 220 degrees may be as low as 210 degrees or as high as 230 degrees. Use a thermocouple on a multimeter, non-contact probe, etc. to verify your nozzle temperature.
Temperature: Nozzle temperature 'sag' of +/- 5 degrees is normal. Monitor nozzle temperature during a print to see if it stays within this range (see: Speed below).
Speed: Printing fast is awesome... when you have a hotend that can keep-up with the demands of melting incoming filament. Too fast, and the filament may not be properly melted; increasing the pressure needed to force it through the nozzle. Support material and infill typically print faster than the rest of the model - you mentioned hearing clicks "...mostly during filling areas."
Alignment: Make sure the hobbed gear, idler bearing, and filament are properly aligned. Filament that wanders around in the feed path is much more likely to slip and/or buckle.
Teeth: Make sure that the teeth of the hobbed gear are clean and clear of debris. 'Gunk' in hobbed gear teeth reduce grip on the filament.
Tension: Increase the tension between the hobbed gear and idler bearing if possible; worn hobbed gears may need a little extra help holding-on to the filament.
Stepper: Heat generated by the stepper motor can be passed down to the hobbed gear... softening the filament and causing it to slip. Stepper quality, capacity, and duty cycle can greatly effect how much heat is generated; 200+ degrees is entirely possible. Passive cooling (heatsink) is a good idea, active cooling (fan) is better.

A loose heat-break, nicks in the filament path, variations in filament width, etc. are all possibilities as well.
Also, Simplify3D created a great reference for solutions to common 3D printing problems (if you haven't seen it already).
https://www.simplify3d.com/support/print-quality-troubleshooting/

In my experience, the "clicking" isn't the gear slipping on the filament, it is the stepper motor not having enough torque to drive the filament.  This is often caused by there not being enough space for the plastic to flow.  Eventually something gives.  Sometimes it is that the head is pushed away, but often it is that the stepper motor breaks torque, and jumps backward to the same driving phase position.

This is a very generic answer that is not specifically addressing the problem. Tormod and Davo are on the right track. The nozzle tries to squeeze in a line of infill in between two tightly placed perimeters, this causes extra friction as the molten filament does not fit in the left over space, hence the skipping.

Try reducing to just two perimeters, and let that blue area be calculated as infill. This may give you a zig-zag infill instead of a straight, oversized bead.

The only time that I've observed clicking from the extruder on my Anet-A8 is on the first layers when I have the head height set too low - the nozzle is unable to extrude at a high enough rate to allow the filament to progress as requested.
If you have a somewhat repeatable scenario, you could try reducing the filament feed rate to 90% or so, and see what effect that has. I have already observed with one of my reels of filament that 90% feed rate gives me a less over-filled solid area, so maybe the default feed rates are a little on the high side (or this filament is of excessive diameter).

One trap I've seen that causes the extruder to click, and over or underextrude is that the extruder control is in the wrong mode.
The extruder can be set into relative or absolute mode. If absolute extrusion values are sent while in relative mode, then the system will be trying to push more through than the nozzle or hot end can handle. You'll get blobs, clicking, ooze and it will damage the extruder and hot end.
Have a look at the G-code - and see what the "E" numbers look like - it they look relative (the same or close numbers repeatedly) or absolute (numbers slowly incrementing). Cura defaults to absolute - but initially was NOT sending the G-code to put my controller into absolute extruder positioning.
Note also - this is separate from the XYZ absolute/relative positioning modes.

M82 will put the extruder in absolute mode.
M83 will put it back into relative mode.

I had this issue and it turned out to be the extruder cog rubbing on the inside of the hole in the heatsink, causing the stepper to slip.


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Non-Heated Beds affect on 3D Prints
I'm looking to buy my first 3D Printer, on a tight budget of $250. Unfortunately, this printer that I found on Amazon comes with all the bells and whistles, except for a heated bed.
I want to know if this would affect printing severely, as I have read that the plastic/ filament cools down rather quickly, and that it results in Printer "fails".
I'm actually a bit nervous with this buy, as I don't want to spend $250 on a printer that produces 90% print fails.
An example of the printer I'm referring to is the Cube 3 Printer, Grey
by 3D Systems.

Just a thought - Instead of purchasing a ready built printer on Amazon, have you considered building your own reprap? If you look at a Bill Of Materials (BOM), and then purchase the parts individually from China. Not only will you end up with a good spec printer, but you would also understand the mechanics a lot better.  For a little over £200 I have sourced all of the parts separately for a P3Steel v4 printer, w/ kysan steppers, and an aluminium 200 mm x 300 mm heatbed. Note that I knew nothing about 3D printing, 3 months ago, so you do not need to be an expert, just do plenty of research...

It had crossed my mind. But I didnt think I had the Know-how to build one. Building one is starting to look like a very viable option right now.

I would have figured that a pre-built printer would be the better of the two evils

I would stay away from those prebuilt printers. Sometimes they make it difficult to use filament which isn't bought from them and you'll end up spending more in future costs. I recommend (cause I just built one recently and it is running better than my more expensive printer) getting an Anet A8 from GearBest. It's a great learning experience to build one yourself, you'll know the ins and outs about it so repairs will be easy. And for 140$(If you catch it on the sale it commonly receives), it is well under your budget. Plus the printbed is ~8x8 instead of a 6x6 and heated. :)

Yes. That said you can view it as an intro into 3d printing. Once you know you are really into it you can buy a higher end machine, or hunt craigslist / ebay / facebook groups for a used one.
What the heated bed will allow you to do is print more than PLA, and certain formulations of no warp ABS. The Makerbot uses no heated bed, instead in addition to being PLA only it does what we call a raft. That said one of my 6 printers is a makerbot and it still gets warping if the print is on the edge of the plate.
You can also add a heated print bed later. If your electronics allow for it.
That said.. Just buy one with a heated bed? I know you can get one close to that price point. Heated beds cost 7 dollar. However as pointed out by Tom, there are other costs such as a more powerful heated bed. Still one should be able to get a printer in that price range or close to it with a heated bed.
To be more clear. You will not have a 90% fail rate if you use PLA. However your prints will often have some heat warping and you will HAVE to use a raft.
from
http://www.reprap.org/wiki/Glossary

Raft
  A technique used to prevent warping. Parts are built on top of a 'raft' of disposable material instead of directly on the build surface. The raft is larger than the part and so has more adhesion. Rarely used with heated build surfaces. For the small area models, it is very useful to prevent warping via adding a raft for the model before slicing it. It can also help with with precision parts by removing the slight first few layer distortion caused by the heated bed.

I think I was exaggerating a little on the 90% bit. I have been looking at some other printers with heating beds, but they are way out of my price range. Do you have any suggestions?

The 7 dollar price for a heated bed is misleading. To use a heated bed you also need a power supply capable of providing the large amount of current it needs.

@TomvanderZanden That is a very good point. Yes a system that needs no powered bed could use cheaper electronics and power supply.

@GypsyD We are quickly falling into forum topics. Stack overflow is for specific question. Not general help me pick a printer. I recommend joining 3d printing or 3d printing hobbyists on facebook. reprap.org has a great forum as well.

@TomvanderZanden Thanks for the link. Will definetly look into it ASAP.

At the risk of an opinionated answer...
I would say that if money is tight, then get the correct printer in the first instance, en lieu of purchasing one that ends up giving you unsatisfactory prints, and that you then have to spend even more money on, in order to get prints of an acceptable quality.
A heatbed, while not essential, is, IMHO, certainly desirable.
Just a thought - Instead of purchasing a ready built printer on Amazon, have you considered building your own RepRap? If you look at a Bill Of Materials (BOM), and then purchase the parts individually from China, then not only will you end up with a good/better spec printer, for the same price, but you would also understand the mechanics a lot better. A good, and thorough, understanding the printer is essential for repairs, when (not if) the printer goes wrong (and believe me, it will). For a little over £200 I have managed to source all of the parts separately for a P3Steel v4 printer, with Kysan stepper motors, and an aluminium 200 mm x 300 mm heatbed.
Note that I knew nothing about 3D printing, three months ago, so you do not need to be an expert, just do plenty of research beforehand.
FWIW, my aluminium MK3 heatbed was £19.99.

Technically one can build a printer out of user normal printer parts. With an end cost next to nothing.. But one would have to be adventurous. I always recommend that people build their first. That said I assumed for that price it was a kit.
I also recommend they spend 500 min. Because the price is Always more then the BOM.

As in parts from a normal paper printer?

@GipsyD - you can make one from old floppy disk drives and hard drives for $50, although I would not recommend it. See Make Your Own 3D Printer for Under $60 Using Recycled Electronic Components with Instructables Design


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Extending extruder heater and thermistor wires
I wanted to extend the E3D V6's extruder heater and the thermistor wires. Is it ok to solder extension wires or does it have to be crimp only! Also are regular wires ok or does it have to be some special cable?

Soldering is fine, both for the thermistor wires as for the heater.
The wires don't need to be particularly special, though there are some things you should keep in mind:

Current. The heater can draw up to 3-4A, the wires need to be able to handle this. The wires for the thermistor can be thinner.
Flexibility. The hotend (presumably) moves, so the wires should be able to withstand frequent movement. Use stranded (rather than solid) wire.

Thanks! And soldering is fine for the thermistor wires too? I've worked with thermocouples and extending those wires by soldering is a strict no-no

Yes. Thermocouples work on a different principle from thermistors.


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3D Molecular Printers
Are there commercially available molecular 3D printers that can create catalytic structures like Zeolites, if not are there any research efforts underway in such field?

Welcome to the site. This is an interesting question, but it is potentially quite broad in its scope. If you can provide a bit more detail about why this is hard, or the nearest technology you know, that would make for a better question (and better questions get more visibility, and more good answers)

This is probably a bit out of most peoples knowledge here. Very high level academia. That said this is all I find http://www.popularmechanics.com/science/health/a14528/the-chemistry-3d-printer-can-craft-rare-medicinal-molecules-from-scratch/

Thank you for the welcome not Sean, I was looking at a powder bed technology that is currently used for parts manufacture not in molecular synthesis. but I think the link provided by StarWind is closer to what I had in mind -Thanks StarWind

I'm leaving this open despite it becoming outdated. I think that the content could be useful and could become a great Community Wiki as this field (molecular printing) develops over time.

The link I mentioned from popular mechanics is the state of molecular 3d printing. So yes the printer does exist and can do some really impressive things. However as the article states it is limited to what it can create right now. The technology sounds really interesting. However it might be a bit out of our knowledge as it doesn't seem to be widely available passed the scientific academia world.
This link here talks about reactionware for Chemical Syntheses as well as a TED talk about it

This sounds like the first steps to a Star Trek style replicator.  Still a long way to go obviously, but I never realized we were even this far along.


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Reducing amount of material
Just started doing some design. First project was a replacement handle for my angle grinder, so basically a hollow cylinder. I want to reduce the amount of material used in the print. I could sit here and punch holes through the handle with a smaller cylinder, or some other shape etc., but is there an easier way to do this?
It must be a pretty common requirement, just like in the movies where the spies look at a photo and tell the tech to 'enhance ... enhance'. Ideally you could select a surface and overlay some sort of pattern to remove material.

So you are looking for something that is "just like in the movies" even though the movies make that stuff right up?

Great job improving the question. I'll update my answer tomorrow to reflect the changes. Though I'm not sure I can help with Hollywood sudo science but I know your meaning.

If you punch a lot of holes in a thin mesh, it will probably increase the cost. You then have to print lots of walls (expensive) instead of infill (cheap).

Hello @SleepyBoBos, I noticed your question has been up for a while now. Have any of the answers below been able to solve your question? If so, would you mind accepting the appropriate answer. If not, what is missing so that we may help you further? Also, if you have figured it out on your own, you can always answer and accept your own solution. Thank you.

Updated to match the improved question format.
There are a few ways to reduce material usage. First is what you have touched on. Which is to reduce the design by punching out holes, and removing all material that does not add anything to the structure. Even better is what you touched on, reducing it to the point where your print is more like a suspension bridge, where it is a the bare minimum scaffolding in a geometric pattern.
Most tools you will find for reduction are like this tutorial from Shapeways on Meshlab where you reduce the surface detail. It might be worth exploring these a bet, however probably not what you really need.
Next the more hard core cad tools such as solid works will allow you to preform Parametric optimizations and Topology Optimization.
Topology Optimization. seems to be your real winner

Now from the 3d printer standpoint we just simply tweak our slicer settings. There are entries for Infill. I usually print with 7% infill. AKA my print is 93% hollow inside. I then set a few solid shell layers. Think of solid shells as the skin. Usually that is enough to reduce my plastic usage. The only reason I don't make a part 100% hollow and a few solid skin / shell layers is that I need something to print on top of or if I need the part to be strong . Even low percent infill can be very strong if the correct geometric pattern is used (I.E. triangles).
Generally the reduced infill will be enough, unless you are making thousands of this item, though in that case you are probably not going to 3d print it anyways.

3dprintingforbeginners has a nice article on the relationship between infill, number of shells and part strength. A bit more information about the terminology (infill/shells/etc...) can be found on 3D printing blog.

An interesting question would be whether it is desirable to rely on certain infill patterns or to design recesses already in the CAD.

@ThomasS.  That is why I always preview and tweak the infill. Though honestly I prefer thick shells and low infill. Rarely have I cracked a part doing this way. But all depends on what I am using it for.

I also preview the infill settings in Slic3r, but have seen a lot of things at thingiverse that have designed recesses.

"Just like the movies"-type tech typically means $$$.
For those who do not own (legally or otherwise) expensive CAD software, it may be difficult to find an out-of-the-box solution. That's not to say that it can't be done.
A close, readily available, solution would be to use a series of common CAD tools such as Shell and Scale. Between these functions, you should be able to scale a copy of your main solid object, then shell the new inner object. When sliced, the object should have a smaller "inner wall" and a hollow center. I would recommend this over 0% infill as a shell will not provide enough strength for the intended use you mentioned.
There is a great article on My3DMatter.com that provides details and a very interesting set of charts, outlining cost, speed, strength, and quality distributions at varying layer heights and infills.
Please Note: These results are going to differ between different material types, vendors, part shape, and infill pattern. These results were found printing from a MakerBot Replicator and presumably MakerBot-branded filament.


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Does XYZPrinting software allow the creation of rafts when printing?
Ironing out all my worries before buying my first 3D printer.
I'm looking at getting the da Vinci miniMaker 3D printer as my first 3D printer, but it doesn't come with a heated bed.
On my previous question about heating beds effect on a print, I was told that I need to use a raft to compensate for the absence of a heated bed. What I want to know is, does the software that comes with the printer allow the creation of rafts whilst/prior to printing? Or will it create rafts if need be?

Or is there another software that can be used with the Da Vinci printer, that will allow me to create rafts for my prints?

2 years ago I had a prebuilt German Rep Rep Neo in the past and after 2 months problems occurred, so I sold it very cheap. Now I've bought a cheaper assembly kit of a Prusa i3 model and I feel much more confident to cope with occurring problems because I know how to assemble and disassemble. I recommend you to also start with a assembly kit.

It had crossed my mind when I was looking at various 3D Printing Options. But I didn't pay too close attention to DIY Models, mainly because I think I will have a bad time assembling it. Dont get me wrong here, the price is cheaper than a pre-built, the build size is SOOO much more better, and the frame is steel, which is a plus in my books, but when it comes to assembiling the printer for use, Im gonna have a bad time

Would you, in your opinion, say that assembling the Prusa i3 was relatively simple?

I would say a raft is more of a band-aid fix for not having a heated bed rather than a way to "compensate". It's nowhere near as good.

Yea. Thats why I'm really considering the Prusa i3 now. At least that comes with a heating bed. No more rafts :D

Ok. After watching some YouTube Videos, I would take it that the abovementioned software does include the option to create rafts when printing a model.

Maybe you could include some details on how to enable raft generation in the XYZprinting software, for the benefit of those who google the question and end up on this site? As it stands, your answer is rather unhelpful for somebody trying to get XYZprinting software to create a raft.

Ok. From what I saw on YouTube, there is an option when selecting print in the software. A window will pop up for you to choose your printer, and on the side, in another window for you to select whether you want to add rafts


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PLA and bed heating?
I've read different things about PLA and heat-bed. Some say it is not needed, others recommend 60-70°C, but not for the first layers.
For larger objects I often have the problem that the object does not stick to the blue-painters-tape-covered aluminium print plate. Instead the print "curls" up on one or more corners. To reduce this effect, I'm using a brim between 5 and 10mm. Depending on the size of the object the brim works quite well. Will heating the bed also improve the print quality by reducing the amount of heat warping / curling?

What's your extrusion temperature?

+1 -  As this post made me look up the difference between Rafts, Skirts and Brims!

See my answer, I have problems with curling, A combination of tape, hairspray and lowering the 1st layer height helped me overcome this issue. Now I very rarely see curling.

I actually find it's not needed for PLA. I generally have it heated to 40 °C and use blue painters tape along with some hairspray (I prefer Tresemme as it smells gorgeous).
I've experimented with a glass bed, and Buildtak but I find blue painters tape is the key. I overlap the blue tape ends to the bed so it sticks, then spray the hairspray onto the tape. Also bed leveling is super important as are your print settings. What you want for the first layer is to have it essentially "pushing" into the bed. That way it gets good contact and wont curl up during the print, though it can be a challenge to get off later.
TL;DR for PLA you dont need a heated bed, its more about the surface and 1st layer height.

On the rare occasions I print PLA, I set the bed to 40C - because it works well.

Heating the bed helps me, even with PLA.  I print with a 60 °C bed.  The bed is 3/8" 6061 alloy aluminum, sanded with 600 grit sandpaper, coated with Elmer's purple glue stick, and dried.
The brim will help.  You might make the brim thicker than one layer (like 2-3 layers).
If you look at the bottom of your print, are there large gaps where the PLA doesn't touch the bed?  If so, you could zero the head closer to the bed, or increase the flow for the first layer.
I haven't set up a cooling fan, although many praise the results.  It is an experiment for a future day.

Slic3r does not offer an option for the layers of the brim, only for the raft.

It did when I used it 1-2 years ago.

Well, the latest slic3r version 1.2.9 from summer 2015 only has a checkbox for the brim but a layer count input field for the raft - (http://manual.slic3r.org/expert-mode/skirt vs. http://manual.slic3r.org/expert-mode/support-material). Could it be that the word "brim" means something different in slic3r and other slicers?

Heated beds can help, but you have to be careful using too much heat. If you go above the glass transition temperature (about 60 °C for PLA), the stresses of the upper layers cooling will warp the bottom, because above the glass transition temperature, the PLA can deform.
For example, I was making very tall and skinny parts, a recipe for warping. At 65 °C, I had a bit of the bottom corners curling, but the part finished. I turned the heat up to 80 °C, and the parts warped so much they came off the build plate. I ran the exact same parts at 58 °C, and they came out beautifully every time.
A higher bed temperature can aid adhesion, (see Effect of the printing bed temperature on the adhesion of parts produced by fused filament
fabrication), but if the temperature is above the glass transition, the parts can and will deform much more easily.

A nice answer and the link looks interesting too. However, if the link dies (as is the way of the internet) then maybe some useful information may be lost. It might be worth quoting relevant parts (no the whole thing though) of the article here.

It really depends on your formulation. 70 °C would be on the higher end. I think I do between 70 °C - 75 °C. Not any higher.
Add a glue from a glue stick to help with keeping it on the bed.
Use a raft to reduce the issue as well.
A fan is the number one thing you can do.
The last solution is to build a heat enclosure. They are not on every 3D printer because of patents blocking them. You can easily make your own.
Technically it is not 100 % needed, i.e. the MakerBot does not use it, but the guys at MakerBot have PLA down to a science.
Also I thought Kapton is not for PLA usually... see these MatterHackers articles:

How to succeed when printing with ABS;
How to succeed when printing with PLA.

From RepRap Wiki - Glossary:

Raft
A technique used to prevent warping. Parts are built on top
  of a 'raft' of disposable material instead of directly on the build
  surface. The raft is larger than the part and so has more adhesion.
  Rarely used with heated build surfaces. For the small area models, it
  is very useful to prevent warping via adding a raft for the model
  before slicing it. It can also help with with precision parts by
  removing the slight first few layer distortion caused by the heated
  bed.

Why exactly raft should help? IIRC, raft is nothing different than some kind of support.

Well a raft is not really a support. It is to help with heat warping. See updated answer

This is fundamentally a heat transfer problem. As a large print is being made, it is very thin. Thin things cool off quickly, especially when no new hot material is being placed on top in the meantime. A heated bed will only help for a time, depending on the print size, before it starts to actually contribute to warping due to rapidly cooling upper layers and still- heated lower layers.
A hack can be found by improving bed adhesion, but this leaves the underlying problem of thermal stresses intact. Only through better 3D printing thermal properties design or through better object design will the warping problem be solved rather than mitigated.

For printing PLA you can manage to succeed without a heated bed. You can use blue painting tape on any platform. It will help a lot. But sometimes the tape itself curls up and you end up with a bad print. Heated bed helps here for better adhesion of the blue tape to the bed. You can also use hair sprey to ensure that the blue tape sticks to the bed.
Hair sprey is pretty effective on ABS. If you use a heated bed + glass + hair sprey ( Akat Gardi is the best brand) you will never have any problem with your prints.

I can only go with my own experiences; a Printrbot simple metal originally with no heated bed and blue tape was fine for small parts if printed with a reasonable brim and rafts when needed (Slic3r does that) but larger prints tended to warp and curl. I upgraded to a heated bed, which I run at 55 - 60 °C for every print. Additionally, I now use Kapton tape on the bed and glue stick. I have recently reprinted a part for my printer, an LCD housing, to replace the badly warped original, which is my benchmark print. I have no warping/curling problems to the point that I have reduced the standard brim from 5 mm to 2 mm to save some material. Some additional detail - only PLA at present from a 0.4 mm extruder at 205 °C in 0.2 or 0.3 mm layer height for the finer detail. Takes longer but the results are worth it.

The answer depends a bit on the type of PLA (supplier of specific filament), type of machine, type of build platform, size of model and ambient temperature.
PLA has less issues with warping compared to ABS or Nylon, but can still warp depending on everything mentioned. My usual first try to minimize warping is to heat the bed. 60 - 70 °C works well but I'll also go up to 100 depending on a variety of factors. If still not having any luck, generally on larger parts I try adding a raft. If I STILL have issues after that I'll add 'helper disks' (small quarter dollar sized disks) around the part to increase the surface area of the raft. The disks will add more material but I have about a 99 % success rate using these.
If a part is going to take more than about 3 hours and I can't have any warping at all, I always use a heated build plate and place the discs all the way around the part. Generally will add about a hour or more, but well worth the extra time.

Do you mean brim (as option in the slicer, http://manual.slic3r.org/expert-mode/skirt) as "helper disks" or do you design them directly in the CAD?

I'm a little unfamiliar with slic3r but my understanding of 'brim' is essentially the same as a 'raft'. A helper disk is an additional part that you add to the build link. If you're using a raft ( or brim)  adding them around the edge or side that peels effectively extends the raft in that area. If you're printing directly onto the build plate, then you can place them under your part giving it a 'localized raft' removing it afterwards becomes more of a chore though.

Heated bed definitely helps with PLA adhesion, it also helps depending the surface, for example PEI offers better adhesion than glass. Another option is to try to overextrude the first layer (125 %) and make sure it is squeezed out, so basically you get a wavy effect on the first layer. This should help a bit even in the curly corners. Another thing I have noticed from experience is the PLA itself, not all PLAs are the same so you could try another manufacturer or try your PLA in a friend's printer to see if you get the same effect. Generally on PLA we do not expect any warping, but the reality is that some do have.

A lot depends on exactly which PLA you use and the build surface. I'm using one of those new-fangled high-temperature PLA's (MakerGeek's Raptor PLA, black) and a BuildTac surface on a MonoPrice Select Mini v2. From my experiments, I believe that the biggest influence in preventing warping is the BuildTac.
My slicer is Simplify3d, so the settings may be in a different format than yours. I use a hot-end temperature of 240 °C, a bed temperature of 40 °C, layer height of 0.0875 mm, a first-layer modifier of 1.5, an extrusion modifier of 0.95, and a retraction distance of 3 mm.
I've never had a problem with warping, but these settings prevent stringing and allow me to more easily remove parts after printing. And yes, I wait until the bed gets to room temperature before removing the part.

Heating the bed helps with adhesion to the bed, but can seriously interfere with cooling of the layers just above the bed that are in contact with large amounts of material touching the bed. I've found that, if I have a model with a flat region touching the bed and walls leaning outward from it (overhangs) as they go up, any corners will curl upwards before they can cool if the bed is 60 °C or above - it's effectively a heat bath at the glass transition temperature that's going to be hard for a fan to overcome.
At 50 °C the effect is almost gone, and at 40 °C and below it seems entirely gone, but the exact temperature that's safe is going to depend on ambient room temperature, cooling fan power, and effectiveness of the fan duct. I've just found this as a solution to my curling-corner problems, so I might end up tweaking things more, but I think I'm going to try printing PLA without heating the bed at all unless I have trouble with adhesion.
An example showing slightly warped vertex/edge from curling corners at 50 °C vs good ones at lower temperatures: