text:
How to set a new homing position using software and/or slicer without changing hardware end-stop?
Before the question, here is my setup;

Prusa i3 (with mainboard Mks Gen v1.2)
Repetier as slicer
Marlin source code

My main task is to convert my 3D printer into a chocolate printer.
I have replaced the filament extruder with a chocolate extruder. And it is there that my issue began. Because, the new extruder is stopping slightly off the y-axis when homing. It is going out of the standard 20x20 cm bed. The other X and Z axes are OK.
So, I have played with the #defines explained below, but I couldn't even make any single mm difference by homing. They are all ignored when the printer is homing. It goes and rests on the hardware end-stops and stops there eventually.
All I want 10 mm offset for Y axis.
Started with this;
// Travel limits after homing
#define X_MAX_POS 200
#define X_MIN_POS 0
#define Y_MAX_POS 190  <<<< (tested with 190 and 210)
#define Y_MIN_POS 0
#define Z_MAX_POS 200
#define Z_MIN_POS 0

and this;
// The position of the homing switches
#define MANUAL_HOME_POSITIONS  // If defined, MANUAL_*_HOME_POS below will be used

//Manual homing switch locations:
// For deltabots this means top and center of the cartesian print volume.
#define MANUAL_X_HOME_POS 0
#define MANUAL_Y_HOME_POS 10 <<< (tested with 10 or -10)
#define MANUAL_Z_HOME_POS 0

I have also played with the slicer tool (Repetier) settings where homing related values are mentioned but no joy there as well.
Any input highly appreciated.

The Y-Max setting does not help, because it is the software end stop for the  other end of the axis.
The Y Home position also doesn't help as it only changes the coordinate that the printer assumes for when it hits the home position. That is used for printers (like deltas) that home to the max end switches.
What could help is a little bit of G-Code right after the Homing. The Homing is a G28. Just add a G1Y10 after that. That will move your Y Axis 10 mm right after homing. So it will then be in the position that you want. If you then add a G92 then this position will become the home position for the print. So adding these two lines should fix it. Cura lets you edit these start G-Codes so that it then will automatically add the modified codes to all your prints.
You can also try a G10 (with a firmware that supports it.
For Details on G-Codes see:  http://reprap.org/wiki/Gcode

At the end, this was also my conclusion. I mean, software end stop is not really what I wanted. But, i didn't really check which G-Code can do this for me. Now, I know.

I am thinking to reinstall the hardware end stop in order to home as I wanted. Although, I haven't played that much with G-Codes so far. It is also looking promising as a solution. But, What I understand from your explanation, the G-Code correction to the Y homing position is only handled when you start printing not when you powered up or reset the printer. It will still go outside of the boundaries. if this happens, some liquid chocolate drops might still fall out the perimeter. Right?

Exactly the homing process will still move to the homing position defined by the hardware end stops. The G-Codes then fix that, but on every move it will move to the critical position and then back again.

Thanks a lot Lars and Kamuro. This solution is definitely saved my day. But, I guess, It would better do either reinstall the Y end-stop or enlarge the bed 10 mm more on all edges.

Now I've finally had time to look into this, since I knew it somehow existed, but wasn't sure how it worked:
Use the M206 G-code command in Marlin, Sprinter, Smoothie, or RepRap Firmware to offset the 0,0,0 coordinate of your printbed relative to the endstops.
The reprap.org wiki page says:

The values specified are added to the endstop position when the axes
  are referenced. The same can be achieved with a G92 right after homing
  (G28, G161).
With Marlin firmware, this value can be saved to EEPROM using the M500
  command.
A similar command is G10, aligning these two is subject to discussion.
With Marlin 1.0.0 RC2 a negative value for z lifts(!) your printhead.

We see, this basically is the same suggested by @LarsPoetter, but it comes with the great advantage that it can be saved to EEPROM, hence you don't need to add it every time or into every different sliccer (if I understand it correctly, - I haven't yet tried it myself)
Let us know if this works for a permanent solution.

I am away from my setup recently but, I will definitely try saving that G-Codes in the EEPROM and see how it helps. I will then share my experience here for sure.

Thanks a lot @Kamuro. It works OK. If the case is end-stops with Marlin, re-installing end-stops is the best option I believe.


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File Input data types
I'm a newb and don't know much about 3D printers.
In visual basic I can create vector data of 3d objects,that can be loaded into a binary or text file.
Can files like this be used with a 3d printer?
Example:
This is a very simplified example of how the code generates 3d vector data.
ju jv jw determine the size and dimensions of the object
ru, rv, rw are the vector lenghts

The incrementors used to increase the size of the object to the max ju jv jw vaules:
ru=ru+1
rv=rv+1
rw=rw+1

'the angles can also be incremented to for curves and spirials'
the angles of the vectors
angle u =0
angle v =45
angle w = 90

Simplified code:
For k1 = 0 To Ju

    ru=ru+1

    xu = (ru * Sin(angle u))

    yu = (ru * Cos(angle u))

For k2 = 0 To Jv

   rv=rv+1

   xv = (rv * Sin(angle v))

   yv = (rv * Cos(angle v))

For k3 = 0 To Jw

    rw=rw+1

    xw = (rw * Sin(angle w))

    yw = (rw * Cos(angle w))

Output xu, yu, xv, yv, xw, yw  ..to file in the order produced on this line

Next k3 : next k2: next k1

Can a 3d printer read this output as is and use it to make a 3d object?

Hi, goo gle! You question is quite unspecific and therefore difficult to answer properly in its current state. Could you please give us a concrete example of what you are wondering about? For instance, what code do you have, what does the 3D models look like, what file format do they translate to, what do you want to achieve, and what have you tried so far? I have chosen to put your question on hold so that you can make your changes. Please let us know when you are ready to open it. Also, welcome to 3D Printing SE!

Someone else told me it would have to be in STL format and i don't think that will work with my data. Because its just striaght forward vector math that constructs squares in 2d and cubes in 3d, not triangles. But thank you for the reply.

i use the method of Graphical Addition of vectors. found on this web page    http://www.electronics-tutorials.ws/accircuits/complex-numbers.html scoll down to Graphical Addition and Subtraction

Could you please add your information to your question by using the edit button in gray text below your question? You will then be allowed to add pictures, code snippets etc. just as you would when writing the question for the first time. Also, when you are done, you can vote for your question to be reopened for answers by pressing the reopen button just right of the edit button. :-)

@goo gle the answer is NO - it won't work. It's much better to read about 3d printing/slicers/firmwares than presenting your code. It's strongly recommended to get at least basic knowledge because then we would have common area to discuss. You did ask the question and John Sensebe answered but you say you know better. Tell me how to convince you that there are principles which you have to accept rather than convince us that your way (of representing 3d objects) is ok. Converting 3d obj to printer format is a bit more than 15 lines of code. Please read at least passed wikipedia article.

Your question is now open again. I made some further code formatting which you might want to have a look at.

thank you for your reply I'll look into this at a latter date.

@ darth pixel  "goo gle the answer is NO - it won't work" Thank you, you answered my question, thats all i need to know, have a nice day :)

Not directly. The most common types of 3D printers build objects in layers. They "draw" a layer, then "draw" another layer slightly above it, repeating until they've "drawn" the entire model. Preparing your model for this is called "slicing", since you are "slicing" your model into these layers. Slicing is a complex process and it's a lot of work to "roll your own" software for it, and there are several good, free applications to do it for you out there already.
What you probably can do easily is output your data in STL format to be read by the slicing software. STL (either ASCII or binary) is a dead simple format that contains the triangles that comprise your model. So simple, in fact, that the Wikipedia article tells you just about all you need to know.
To get triangles from squares:
A--B    Here is a "square" with vertices ABCD.    A--B    A--B    A
|  |    Splitting it from A to C produces two     |\ | ->  \ |    |\
|  |    triangles, ABC and CDA.  This can be      | \| ->   \|    | \
D--C    done as part of the output by simply      D--C       C    D--C
        writing two triangles for every
        square in the input.

Thanks for answering but i don't think it will work my math is not written for triangles. its just striaght forward vector math that constructs squares in 2d and cubes in 3d, not triangles.

@google - It's really easy to split squares into triangles, though. Just pick a diagonal arbitrarily and divide each square into two triangles, like cutting a sandwich. You can do it as part of the output routine so the original model isn't modified. If your square is defined by vertices A, B, C, and D, going clockwise, then output triangles ABC and CDA.

i'm not useing a program with a graphical interface that you can use with a mouse, like cad or blender. I'm useing a version of qbasic called qb64 it's only texted based. There is nothing for me to split. there are no models to work with its all purely text. The 3d vector data projects a 3d image on the 2d screen as a finished picture not a model

@google I think John gets that. You'll need to do the splitting in your code, to convert the vectors and cubes into triangles as required by STL format. You could also look into using OpenSCAD, which is a programming language designed specifically to programatically generate STL files.

source: Stack Exchange

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

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Does the layer thickness have any effect of the strength of the 3D printed object?
Is a 100 micron layer thickness object stronger than 300 micron layer thickness 3D printed object? Are there any rules to follow?
Filament type - PLA

3D Matter has published an excellent article on the subject. They find that thicker layers result in a stronger part, with 0.3mm layers giving a part that is around 24% stronger than the same part printed with 0.1mm layers.
One small issue with this study is that it did not look at the effects of temperature. Raising the temperature generally results in stronger parts because the layers will fuse better. It is possible that you could make a 0.1mm part just as strong as a 0.3mm part by raising the printing temperature.
Another consideration for inter-layer bonding is how much the next layer is "squished" onto the previous one. Using a wider extrusion width will improve strength.
The main issue with the strength of FDM parts is that they tend to break much easier along the layers, much like how wood is much stronger across the grain. You have to take this into account when making your design, and ensure that features that will be subjected to stress/strain are printed in the XY-plane.

Much of the difference in strength by layer height can be addressed by printing hotter with lower layer heights. A strand of half the height cools twice as fast, give or take. Faster cooling means weaker prints.

@RyanCarlyle: does that also mean printing in a heated chamber increases part strength?

Yes, absolutely. Warping stress weakens the print by leaving residual stresses in the layers, and that makes the print more brittle and weaker against applied loads. Hotter chambers have less warping stress in the print.

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How to reuse modelling bases for the Stratasys uPrint SE Plus?
It's criminal how wasteful the Stratsys uPrint SE Plus is with it's 'one use' modelling bases. Is there a reliable way to re purpose them? I have tried ethanol and acetone, but not had any luck.

Hi, when talking about "one use modelling bases", do you mean the rafts created underneath each model as it is printed?

Hello, I mean the black modelling bases that the ABS is printed onto. With this model of machine they are difficult to reuse as the support material laid down leaves a scar.

What I tried and worked is to apply water based normal Glue-stick on the tray and with few drops of water distribute it evenly across the tray surface, let it dry and then you are good to go!

Thank you for your suggestion. What sort of glue do you mean? Glue that you would use to stick paper together with?

@JPD, although I do not know the exact brand that Mohammad use, I know that UHU Glue Sticks are fairly commonly used. Different glue stick give somewhat different results, so you might want to try a few different types.

The brands I tried are Scholastic glue stick and Staples glue stick both gave the same results. Worth mentioning that it is easier to remove the part when the tray is cool.I plan to experiment with the Aquanet hairspray next week.

People have done quite a bit of experimenting with reusing Mojo build plates over the years. The uPrint is likely similar. Basically a different adhesion layer is placed on the bed that has easier release. BuildTak has been used successfully. Gluestick or hairspray such as Aquanet will work and are water soluble for easier removal post-print.

Thanks for your answer. BuildTak looks interesting. Excuse my ignorance, but would you put a layer of this on top of the modelling base before printing? Then remove the print from it, clean it and re-use?
Also do there have to be some manual adjustments to nozzle height etc. due to the added layer?
Lastly, how do machines that require calibration points (such as the uPrint SE Plus) deal with having a non-native surface to calibrate to?

Right, you put the adhesion layer on the modeling base before printing. That allows the raft to come off easier.  If the added layer is thin enough, it won't interfere with the normal raft building process. But I'm not specifically familiar with your printer, so it may take some experimenting. Obviously this isn't supported by Stratasys, because they want to make money on consumables.

Ryan, can you let us know the source for 'people have done...' to dig a bit deeper in their experience, - temerature changes and adhesion results for example? Thanks in advance

Search for Mojo posts by vrfx and EnginWiz on the 3D Printer Tips Tricks and Reviews Google Group. They've both posted about it a few times. Can't find links from my phone though.

By oversight in training, the operators of one of our UPrint SE Plus printers was simply placing the tray in the bath with the printed part.  After it was in the bath, all support material was removed and they dried and reused the tray.  This process was used for months before it was discovered, and they used the same tray for many prints.  Has anyone else tried this?

I've done the bit where you place the tray and part into the bath. Upon completion of dissolving, I then used a little dawn dish-soap to clean the tray, let it dry. I have access and used DI water for the hand washing (without any scrub or pad, just my hands). The trays worked fine.
Someone else took over for a bit. I think they were trying to clean with Vinegar, and the trays have all turned white (not sure if that is from this?). So, they aren't being reused.
I've started being a bit strategic with some print jobs. I'll print in one corner, then use cutters to remove the support without damaging the tray. Then I'll print on that tray in a different corner.

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Trying to flash Davinci XYZ 1.0, nothing but black bars
I get nothing but black bars and "Unknown USB Device" from Windows 10.  This is after a failed flash that was otherwise going directly according to plan.
This Davinci has been nothing but frustration for me, and I'm really tired of fruitless Google-Fu.
Much of what I see pretty much says it's bricked;  attempting to jump the jp1 jumper any further does me no good.
Is there anything I can do to actually move forward, or are we in soldering-iron territory now?

I had this occur on my MakerBot Replicator Dual after I tried repairing a blown voltage regulator. If you refer to the previous link to my SE question, pay attention to the comments of Ryan's answer where it is explained that (in my case at least) the main processor was damaged and therefore couldn't properly load the firmware. The machine was able to load just enough to initialize the chip on the LCD screen, but since the main boards processor was blown, couldn't load the firmware to send commands to the screen and continue the boot sequence.
I'm not certain that you're encountering the same EXACT issue, but you have all of the same side effects that I did. Basically, if you're not pro with electronics, your board is bricked. Otherwise, you might be able to salvage the board by replacing the processor, but there's no guarantee that something else isn't wrong or that the new processor was installed correctly.

Yeah.  Basically, I'm not interested in doing all that stuff.  I'm a casual maker, and the XYZ is otherwise a pretty crappy printer in my experience.  Thanks for the pointers.


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How to optimally make a 3D model of an object using photos?
I would like to obtain a 3D model of my insoles. I tried to scan it with 123D catch but finding reference points is difficult because the insole is black.
How could I improve the scanning? I attach a photo of the insole to show its not easy shape.
I thought about placing a grid of white spots on the surface, but will it be enough?
Also, is it recommended to keep the camera still and rotate the object (I have a rotating stand) or should I move the camera? in the second case, the accuracy of the photos will be lower, while rotating 5-10 degrees the stand every time is extremely easy.
As background should I use a checkerboard or something else not repetitive?
I noticed that the insole has basically three different "levels", joined smoothly with each other. These "planes" are sloped the same way, so that if I change the pitch of the insole by about 10 degrees, they will be horizontal. Would it improve the accuracy?
Edit: the insole is perfectly new, newer worn before.

Update
I dotted the insole with white paint (the white eraser paint used in office and school) and I took a series of photos with the insole in top of a tripod, laying on a flat white cardboard support. 55 photos in total at 3 different elevations (side, medium, high). I also did a test with fixed camera and rotating object.
Photoscan did not work well in general. Keeping the object fixed produces the best results, but poor.
123D Catch did a much better job! again with fixed object and moving camera. Still, treating the resulting mesh was difficult and the accuracy could be improved.
Autodesk Remake 2017 worked VERY well, as you can see in the attached screenshot, and it allows the editing of the mesh to remove useless parts of the model. I haven't tried yet to process the photos with the camera fixed and the rotating object. I did the processing locally (it's slow!) with maximum details and resolution.

This is likely borderline 3d printing related, more aimed toward scanning. Consider to spray foot powder to lighten the surface. Coat it evenly, as any dark areas will become voids. Placing the insole on a thin wire easel will improve results, maybe 30 degrees. Place light colored chess pieces around the insole, but do not change placement during the scan. The turntable is better, with camera on tripod. Shoot from low angle, medium angle and high angle, full rotation each time.
Agisoft Photoscan does not have photo count limitations and has 30 day free trial for higher quality results.

I know it's borderline, I asked on meta before posting. Thanks for the other info!

Tried Photoscan, both with turntable and with fixed object. No good results, even if I dotted the surface of the insole with white spots (I used the white paint usually applied to paper to correct typos). Object fixed and me moving gave better results. I think the best solution is to build a touch probe to apply to my 3D printer, like https://www.youtube.com/watch?v=8gMF6zWHpz8 and http://www.raspibo.org/wiki/index.php/A_DIY_touch_probe_for_my_Wasp_3D_printer

There's yet one more option available to you, which may provide improved results. It's called FlexScan3D - http://lmi3d.com/products/flexscan3d which uses a computer projector to overlay patterns on the item being scanned. The distortions generated by the shape are taken into the calculations to generate the model. It's equivalent to David Scan but less expensive. Still pricey if you have to buy a camera and projector!

Usually, the largest variability in 3D imaging is lighting, closely followed by the color scheme. You'll probably want to heed some of the following points:

No colors in the background/stand, keep to shades (unless otherwise specified for scanner)
No gradients. This applies to poor lighting causing a "gradient" light effect
Set the backdrop beyond the range of the scanner if possible (like with Skanect w/ Microsoft Kinect)
Ideally set the backdrop and especially the stand in contrast with the color of the object.

You're right, a typical 3D scanner will have a difficult time with darker colors due to physics. However, there are no rules that say you can't change the color of the object.
In this application, I would suggest just going ahead and spray painting the object and scanning it. Scanning the insole is going to require super tight tolerances in scanning as I'm assuming the insole is naturally worn due to use.
Completely alternatively from 3D scanning, you could try using a 3D touch probe like on a CMM (Coordinate Measuring Machine). It will take longer, but a touch probe doesn't care what color the object is.
Update
The touch probe comment seems to be a hit, so I'll elaborate. My experience with touch probes comes only from manufacturing technology and can be found and in a variety of different machine tools:

Mills
Lathes
CMMs
Vision Systems
"Romer" Arms (aka portable CMM)

You could probably get away with searching for a local machine shop (or job shop) and asking if they have a machine for reverse engineering. The quickest and easiest machine for reverse engineering (in my experience) is a portable CMM, I recommend Googling it.
Alternatively, I've heard of people adding touch probes to their 3D Printers, but I haven't seen it before. In theory, a basic touch probe can easily be achieved by using a momentary switch. If you're good with programming and maybe a bit of Arduino, you could do the following:

Add momentary (normally off) switch to Arduino
Find a way of attaching the switch (below nozzles)
Connect to your 3d printer in your preferred method and preferred programming language. I've used the provided libraries in Python that come with installing MakerWare in order to connect to my MakerBot.
Write your routine to sequentially move the new probe in a grid pattern and then incrementally move the Z up until you get a signal from your Arduino that the momentary has been switched on.
For each trigger, append a simple text file with a new line containing the coordinates.
once complete, you should have a "point cloud" of your insole which, if formatted correctly, will be able to import into CAD software

There are a few file types off the top of my head that can be used including:

.pts
.XYZ
.CSV

I like the idea of touch probe scanning. I though of something like that, but didn't know it readily existed so far (on other scales than atomic force microscopy ;-)).

Ok but how can I get a touch probe at home? Also, I edited to clarify the insole is perfectly new. I wanted to scan it before using it, to reproduce it in the future. I will try to use baby powder instead of paint, at least it can be easily removed and it won't stick to my feet when using the insole.

I don't have enough reputation to comment.
This is a short pointer to another webpage:  https://www.sculpteo.com/blog/2016/01/20/turning-a-picture-into-a-3d-model/
It may be helpful.


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Connecting Sain Smart Mechanical End Stops to Ramps 1.4?
I have Sainsmart Mechanical End Stops, and I'm building a Prusa i3 Rework.
I've recently gotten the x-axis to move, but it needs to stop when it gets to the end and it does not do that; I end up having to pull the plug.
From what I understand, there are two ways to wire ends stops in general, but you have to change the settings in the firmware to make it work right.
There are 3 connectors on the board:

S (signal)
- (ground)
+ (VCC)

My Sainsmart Mechanical End Stops have 4 connectors!!!
According to their website, left to right with the white connector facing you, they are as follows:

S
Normally Closed (NC)
Normally Open (NO)
VCC

Now it seems to me that if I take those connections and connect them as follows it should work...(ramps on the left, sainsmart end stop on the right):

S (signal) -> S
- (ground) -> Normally Open (NO)
+ (VCC) -> VCC
nothing -> Normally Closed (NC)

...but!  Screwing this up by either using the wrong firmware of selecting the wrong wire frys your board, so I thought I'd ask here.  Sources please.

The picture shows "S, GND, GND, VCC" but you list "S, NC, NO, VCC" in your post. I think the picture is correct, as indicated in my answer.

The multiple connections are redundant. Your picture indicates the wires labelled as "SIGNAL, GND, GND, VCC". This is correct if the board is a "standard" mechanical endstop v1.2. The two middle pins are both ground, but you only need to use one of them.
You can simply connect signal to signal and ground to ground. That is sufficient for the endstop to work. You only need to connect VVC to VVC if you want the LED that's on the board to function.

I can add as a source: My printer works with the connections as shown in your picture. (I had to learn it the hard way due to all the confusing information on the internet) ;)

@TomvanderZanden Tried this last night, and board did not fry for the x-axis!  Thank you!


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How do you make sure you have the right voltage on the trimpots on an A4988 stepper driver?
I've been looking into this, but:

I'm not certain how to configure my multimeter;
I don't know how to keep the voltage going, and;
I don't know how to keep the multimeter connected to the VMOT?

I'm told you're supposed to aim for about 1 A.

Generally speaking voltage on stepstick output should be around 1V.
To imagine more or less what the current and what the voltage is, you can think about it in the same way as about water.
The wire is more or less the same as the pipe.
The voltage can be imagined as (sort of) the height from which the water flows but the current can be imagined as an amount of water which flows. To simplify things we assume that all our pipes are closed into circuit and we have pump/battery and we have a motor which is a reverted pump ;) and finally we have our stepstick which is a tap in our model.
So no matter what the height (voltage) is we know that tap (stepstick) will pass some amount (current) of water. We can drive it turning tap or turning a potentiometer on the stepstick PCB.
So we got it. Principles (deadly simplified) are now clear. See here for more details
Getting back to your question.
You have to know what is your stepstick reference voltage. To make sure about that you have to check out resistor(s) next to main black element on stepstick board. There should be R100 or R200 which are very common.
Now you should read data from motor label to know what is proper current for your motor and calculate
voltage = motor_current * 8 * resistance_of_resistor
So now you know what is proper voltage for your motor and stepstick.
You measure voltage between potentiometer and GND (see on the picture)

If you set and connect everything and start printouts you should check motor temperature. Use your finger. If you can touch motor and hold your finger not more than half a second then probably the voltage set on potentiometer is too high (motor can reach 80° Celsius and it's fine but more will shorten its life span) and you should reduce it a bit (reduce by 5/100 V). If you notice that motor growls or barks then your voltage is probably too low and you can increase it by 5/100V.
Too high current will also reduce longevity of stepstick so cool them out with fan.
Please be noticed.
Z-axis motors will usually be not too hot as they work less than X and Y but as they are both connected to one stepstick so they need more current - set higher voltage there.
Here is a reprap.org site to get basic knowledge about stepsticks.

I want to add some points and clarifications to the answer that @darthpixel already has given. Most information you need is in there, I want to give some more practical advice, since that is what I understand you're question is asking for. I'll start with some points on the more theoretical side, though:

notice that the Vref is not a voltage that is passed on to your motor. The described pipe analogy is very good, but the Vref is outside of this analogy. The reference voltage Vref is only used to set the current limit. This seems confusing, but has electronic reasons. One can understand the major (side-)benefit easily: Voltages are very easy to measure externally, because you connect your voltmeter in parallel. If you wouldd want to measure the current, you would need to get your ammeter in series with the circuit.
The stepsticks work by supplying the needed current for movement of the motor (current, because it works by creating magnetic fields), the voltage the stepstick supplies is 'just' supplied as high as needed to feed the desired current through your motor (determined by its resistivity/impedance). This just as an add-on.

Now to the practical side and the application of darthpixel's answer and the above:
You want to measure the reference voltage to limit the current that produces the torque, but also heats up the motor - let darthpixel's advice be your guide: if you can't touch it because it is too hot, then there is too much current, i.e. Vref is too high). To do so:

Set your multimeter to volts, range can be autorange or something bigger than 2V.
Connect one lead of your multimeter to the ground of your Prusa i3 controller board's power input (I use the screw that fastens the ground input of the RAMPS). The other lead goes directly to the center of the trimpot on the Stepstick. I took the best of my paint skills to create an image showing the process:
Note the value you read (12V power has to be on)
Use an insulated screwdriver and turn the trimpot slightly.
Get a new reading by repeating the measurement process.
Repeat the whole process until you get the desired Vref.

Warning: While I've had no problems turning the trimpot while everything was switched on (with my DRV8825 drivers), you should switch the power supply off when doing so.
The described process allows only for a stepwise and rather slow setting of the Vref, but this is the easiest way I've found. I have read of people that use a crocodile clamp to attach the multimeter to the screwdriver for a readout while turning.
If you don't have any idea whether you need more or less current on the motor at the moment, check your resistors on the board and calculate the Vref you should need (see darthpixel's answer for the formula). I would however just do what darthpixel already suggested: figure out the trimpot position by ears and touch: klicking motor: go to higher Vref. Can't touch the motor for more than some seconds: go to lower Vref. It might be a lengthy process, but in the end you'd need to do it anyway to get the best out of the printer!

Perfect addendum @kamuro (+1). Especially about connecting multimeter to the screwdriver. One another advice - potentiometer on stepstick is veeeery sensitive. It's worth to be as gentle as possible turning... well... brushing it :) By brush I mean just a little turn... just a little.

Thanks ;-) Also for the advice about the tiny turns of the trimpot, they're a pain - I also found it incredibly hard to see if I actually already turned it or not.

It's better to have a screwdriver which has thick handle. The thicker handle the more precise is your tunning. It sounds strange as usually procise screwdrivers are thin but well... thick handle is like long lever :)


text:
Distortion calibration on XY plane in Repetier
I built a delta 3d printer (like a mini Kossel) and now I'm trying to calibrate it. I made all the horizontal and vertical bars myself with wood and I bought angle joints (between bars) made with 3D printed ABS.
It passes all tests in Z correction tools calibration. I used a z-probe (with manual deploying) to calibrate it with G32 and G33 commands.
Now I'm trying to calibrate the distortion that takes place on the x and y axes.
Basically what happens is that in a test cube of 10x10x10mm it is translated on x and y axes at some points in the corners.
Below an explanatory image:

The dimensions are good (less than half of a mm) but got this bad visible distortion (about 1 mm or less).
There is a tool or a command in Repetier-host/firmware that corrects this issues?

i myself find same problem with my machine after searching i found out my frame of printer is bend at 2 degree angle at x axis so my all printed object are printed at that angle of 2 degree in x axis.
so we need to straight our frame but it is impossible to do for me. So if you found something please inform me as well.

Not an answer as specifically requested to use Repetier, but please note that Marlin Firmware has skewness compensation implemented. This is implemented in the configuration file, and found under header Bed Skew Compensation. You basically print a square and measure the diagonals and insert these measurements into the configuration file. This should be used as a last resort, it is better to fix the geometry of the hardware.

Skew distortion in deltas means there is something physically wrong with your printer build, such as the towers not being evenly spaced or being tilted. The first thing you should do is confirm the mechanical build -- measure the distance between towers, angles between towers, parallelism of all three towers, and perpendicularity of all three towers to the bed. If you post photos of your build, we might be able to provide more specific advice.
If you can't get the mechanical issue sorted, it's possible to calibrate out some specific build errors (like skew due to uneven tower angle), but that's nearly impossible to do "by hand." You really need to use a Z probe and auto-calibration sequence such as in Rich Cattell's Marlin fork or dc42 RepRapFirmware.

Hello, i update the question with more info. I know that there is something wrong in my build (nothing is perfect) but what i'm trying to do is to correct this imperfections in some way (preferably via software).

The way you describe your build, it might not even be possible to get all the errors calibrated out. Deltas require fairly high fabrication precision to produce dimensionally accurate output -- auto-calibration can fix moderate errors but not big ones. This is simply the reality of the deltabot architecture. Cartesian printers are much more tolerant of low-precision construction.

And to answer your main question, Repetier doesn't currently have a full-fledged delta auto-calibration technique that can fix skew distortion. It can only do bed tilt and bed grid mapping to my knowledge. You'll need to switch firmware or use David Crocker's manual calibration tool. See my answer to this question: http://3dprinting.stackexchange.com/questions/1460/bed-leveling-method-not-work-with-repetier-firmware-0-92-9

And a manual one (via firmware/software)? Now check your link. thanks

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


text:
Printrbot simple metal not auto leveling
I have a printrbot simple metal with the heated bed upgrade. Its been working fine until Cura updated, now, after the x,y, and z axis zeros, the print starts without moving to the other corners and auto leveling the bed. Does the new version of cura require me to turn the function on or should i try to re flash the printers firmware? Thoughts? Thanks.
UPDATE
using an older version of Cura, the printer auto levels and works as expected. Is there any clue why the new update of cura stops this function?

See if you can check what the starting G-Code is. I havn't used Cura but what I think has changed for you is that your new software is homing just using the G28 command and not the G29 command.
I think if you can look into your slicer settings you will find an option to change what the starting gcode is and you will probably want to change it to something like this
G28 X0 Y0
G28 Z0
G29


text:
OctoPrint webpage freezes (Setup on a Raspberry Pi running Raspbian)
I have been using a software called OctoPrint that allows you to control your printer in your Browser. For sake of simplicity I have used Octopi, a preinstalled image with OctoPrint, but now I would like to make some changes, and I decided to build OctroPrint by myself, the instructions for building it are here: https://github.com/foosel/OctoPrint/wiki/Setup-on-a-Raspberry-Pi-running-Raspbian. The problem is that when I follow the first commands:
sudo apt-get update
sudo apt-get upgrade
cd ~
sudo apt-get install python-pip python-dev python-setuptools python-virtualenv git libyaml-dev build-essential
git clone https://github.com/foosel/OctoPrint.git
cd OctoPrint
virtualenv venv
./venv/bin/pip install pip --upgrade
./venv/bin/python setup.py install
mkdir ~/.octoprint
sudo usermod -a -G tty pi
sudo usermod -a -G dialout pi

And then I start the octoprint server
 ~/OctoPrint/venv/bin/octoprint

The webpage of Octoprint freezes

I don't know if this is fixed in later commands, but I would like to get a sense of how all fits together before continue. It doesn't look that is the browser (I am capable to visit other websites without any problems), so is maybe Octoprint? How can I fix this? Did anyone have this problem before? Thanks in advance

The output in the console is:
2016-07-11 03:09:19,442 - octoprint.server - INFO - Starting OctoPrint 1.2.13 (master branch)
2016-07-11 03:09:19,502 - octoprint.plugin.core - INFO - Loading plugins from /home/pi/.octoprint/plugins, /home/pi/OctoPrint/venv/lib/python2.7/site-packages/OctoPrint-1.2.13-py2.7.egg/octoprint/plugins and installed plugin packages...
2016-07-11 03:09:20,522 - octoprint.plugins.discovery - INFO - pybonjour is not installed, Zeroconf Discovery won't be available
2016-07-11 03:09:20,524 - octoprint.plugin.core - INFO - Found 6 plugin(s) providing 6 mixin implementations, 3 hook handlers
2016-07-11 03:09:20,533 - octoprint.filemanager.storage - INFO - Initializing the file metadata for /home/pi/.octoprint/uploads...
2016-07-11 03:09:20,536 - octoprint.filemanager.storage - INFO - ... file metadata for /home/pi/.octoprint/uploads initialized successfully.
2016-07-11 03:09:23,615 - octoprint.util.pip - INFO - Found pip at /home/pi/OctoPrint/venv/bin/pip, version is 8.1.2
2016-07-11 03:09:23,620 - octoprint.plugin.core - INFO - Initialized 6 plugin implementation(s)
2016-07-11 03:09:23,625 - octoprint.plugin.core - INFO - 6 plugin(s) registered with the system:
|  Announcement Plugin (bundled) = /home/pi/OctoPrint/venv/lib/python2.7/site-packages/OctoPrint-1.2.13-py2.7.egg/octoprint/plugins/announcements
|  CuraEngine (<= 15.04) (bundled) = /home/pi/OctoPrint/venv/lib/python2.7/site-packages/OctoPrint-1.2.13-py2.7.egg/octoprint/plugins/cura
|  Discovery (bundled) = /home/pi/OctoPrint/venv/lib/python2.7/site-packages/OctoPrint-1.2.13-py2.7.egg/octoprint/plugins/discovery
|  Plugin Manager (bundled) = /home/pi/OctoPrint/venv/lib/python2.7/site-packages/OctoPrint-1.2.13-py2.7.egg/octoprint/plugins/pluginmanager
|  Software Update (bundled) = /home/pi/OctoPrint/venv/lib/python2.7/site-packages/OctoPrint-1.2.13-py2.7.egg/octoprint/plugins/softwareupdate
|  Virtual Printer (bundled) = /home/pi/OctoPrint/venv/lib/python2.7/site-packages/OctoPrint-1.2.13-py2.7.egg/octoprint/plugins/virtual_printer
2016-07-11 03:09:23,628 - octoprint.filemanager - INFO - Adding backlog items from all storage types to analysis queue...
2016-07-11 03:09:23,639 - octoprint.filemanager - INFO - Added 0 items from storage type "local" to analysis queue
2016-07-11 03:09:23,644 - octoprint.server - INFO - Reset webasset folder /home/pi/.octoprint/generated/webassets...
2016-07-11 03:09:23,660 - octoprint.server - INFO - Reset webasset folder /home/pi/.octoprint/generated/.webassets-cache...
2016-07-11 03:09:24,082 - octoprint.plugins.discovery - INFO - Registered OctoPrint instance on raspberrypi for SSDP
2016-07-11 03:09:24,095 - octoprint.plugins.pluginmanager - INFO - Loaded plugin repository data from disk, was still valid
2016-07-11 03:09:24,135 - octoprint.server - INFO - Listening on http://0.0.0.0:5000
2016-07-11 03:09:24,602 - octoprint.plugins.announcements - INFO - Loaded channel _important from http://octoprint.org/feeds/important.xml in 0.43s
2016-07-11 03:09:25,271 - octoprint.server - INFO - Preemptively caching / for {'query_string': 'en', 'path': '/', 'base_url': 'http://0.0.0.0:5000/'}
2016-07-11 03:09:59,143 - octoprint.server.util.sockjs - INFO - New connection from client: 127.0.0.1
2016-07-11 03:09:59,884 - octoprint.plugins.cura - INFO - Path to CuraEngine has not been configured yet or does not exist (currently set to None), Cura will not be selectable for slicing

Do any errors pop up in the console? Press F12 and go to a console tab/menu, paste any errors you see. There might be an issue connecting to a machine. Do you have the machine turned on?

I just added the output in the console. The raspberry pi is turned on. Also I forgot to say that the website is fine when is loading, but after 3 or 4 seconds, it freezes

You mentioned you started with the stock OctoPI build/installation but didn't mention that everything works without your changes.
Have you tried making your improvements one at a time to find out where the freezing web-page is introduced?

I am not making any improvements yet. I am just following the steps of https://github.com/foosel/OctoPrint/wiki/Setup-on-a-Raspberry-Pi-running-Raspbian, and I am stuck in that step

Is it the Raspberry Pi that locks up, or just the webpage? If the whole thing becomes unresponsive I would consider reviewing your overclocking settings. If you've set one of the higher overclocking values in the config script, this can often lead to random lockups.  If you don't see the config script every time you boot the Pi, you can access it by typing the following into a terminal window.
sudo raspi-config

You can find out how to change the overclocking settings from the config script in this guide


text:
How to add internal supports/localized infill, preferably in Cura?
I'm currently designing a very large and complicated model, because it's large and should be strong enough completely hollow I want to print it with no infill to save material.
However, there are some points in the model where there are indentations in the top shell.
The bottom of those indentations are lower then the surrounding shell (pretty mush the dictionary definition of indentation) and so they are printed earlier with nothing to connect to.
For example, in the image below from Cura's layer view you can see two round surfaces just hanging in mid air

Obviously this can't be printed.
What I'm currently doing is designing internal spaces inside the model where the internal space shell is holding the "detached" surfaces.
What I want is a mostly automatic process that will generate a support structure inside where needed or that will generate infill but only between the floating surface and the nearest solid shell below it.
Reorienting the model is not an option because a. it wouldn't fit on the build plate and b. even if it did it has a lot of internal parts with different orientations so it would just move the problem from one part of the model to another.
I usually use SketchUp for designing and Cura for slicing so I prefer something I can do in Cura - but since I strongly suspect this can't be done in Cura I'll accept answers that work with other tools

I'm not really sure if i get you right but it seems like you gotta switch on support material. That's all. Correct me if I'm wrong but it sounds like very common situation where some parts are hanging like your yellow disks.
Otherwise if your model is going to be closed at the bottom and at the top you can mock support on your own to have better control of it. How? Just add hollow cylinders under your disk so in fact cylinder will stay on the bottom layer then its walls will be support and finally your yellow disk will be a top cover of the cylinder. I hopw you can imagine that properly.
Another way is to design support elements wich would grow out of walls and this way support your disks

Maybe if you would explain a bit more, what the model is then I could support you more.
[edit]
To make it more automatic, you could try to use parametric CAD apps. I would say, Autodesk Inventor is one which I can suggest. You can use for example its Ribs functionality as support (varsion C).
[edit2]
After Tormod Haugene's and tbm0115's comments I decided to fill some gaps in my answer. Here go pros and cons of options A, B and C.

option A

The simplest one and more or less automatic one. Which means when user add support then this option will be a result of it. Of course if user needs to have support only for the disk but over the disk there will be... a "ceiling" then option A cannot use regular support as it will generate a support also for the ceiling. For such situation user needs to add a cylinder manually (filled one) or

option B

User can add hollow cyliner (just its walls). This option can give similar or higher stiffness as regular support because solid walls increase endurance tahn thin support grid.

option C

This option (my personal choose) has some advantages unavailable in A or B option. First - support doesn't have to have "ground" base. It means the yellow disk can really hang even if there is no bottom layer at all. Second - it joins walls with disk and walls together so the stiffness concerns other surfaces.
Depending on needs the cylinder (option A or B) can be transformed into a cross or pillar (thinner than cylinder itself). It can be more taper expandint to the top or to the bottom.
There could be even option where the above one would be joined with option C. So these (3) ribs would raise from the bottom but not from the walls.

Thank you, this is what I'm doing right now, I just wanted something automated (the real model is much more complicated and requires a lot of internal cylinders and cones)

Automated you say. Check meshmixer application. It can surprise you in terms of support material :)

@darthpixel mashmixer is great for support, however, I didn't find any feature there that places support/infill inside the object

@Nir I'm quite sure that MM produces inside-support on its own, I mean without any extra option for such support. Objects I managed in MM had it. But the real question is, why don't you just support your disk manually with kinda pillar or cylinder. If it's interior (I assume invisible) then what is the problem. Gimme more light on your model please so I could help you better.

@darthpixel the specific model has lots of those surfaces, sketchup is rather bad at designing small internal spaces and it seems like something a slicer could do automatically.

@darthpixel also MM does not add support inside solids, it only adds internal support if I create holes inside the part - and at that point I might as well create the support myself

In Slic3r, this can be solved by selecting a suited infill pattern and density, while enabling the only infill where needed-option:

Personally, I have found the concentric infill pattern to provide good support for models with internal overhang, although other patterns might work as well. I would try different patterns at ~30% infill and inspect the result in the print previewer.
The option of using only infill where needed will generate internal supports where needed without filling the entire model. That could be what you are looking for.

Additionally, I believe you can add supports in Slic3r, and then export it as an STL to used in Cura. I will verify that later, though.

@TH no doubt. It's Export STL on the right panel on plater.

Thanks, but Slic3r "only infill where needed" also place infill below surfaces that can be printed just fine with normal bridging, in my case this option will give almost the same result as using global infill

@Nir, did you try using different infill patterns as well?

@TormodHaugene It would be awesome if this worked, but as of today, no, Slic3r can NOT export an STL with support material. Exporting the STL just exports the objects imported into the tray. There is a feature request for this here: https://github.com/alexrj/Slic3r/issues/2575

@wjl, I obviously didn't do my fact checking properly. Thanks for clearing that up!

In Cura 2 you can do several things:

Design internal support pillars, and make them an Infill Mesh via the Per-object settings. I suggest you also reduce the top/bottom thickness and Wall thickness of the infill mesh.
Enable Hollow Out Objects and enable support.
Enable gradual infill: increase the Gradual Infill Steps. Although this will still make infill everywhere it will drastically reduce the infill where it's less needed.


text:
How to utilize/calibrate print fans for PLA?
At the moment, I am thinking about print fans that cool the plastic when printing. I am not asking about the design of the fanducts, which might be a whole book on its own. I would like to know how to find out the best application of print cooling for a given PLA filament, - that is fan speeds and setup in a slicer of your choice (to learn what the different options are).

Everybody's combination of fan hardware and print settings is different. Unless someone else has the exact same printer and slicer profiles as you, there's no way to really say anything like "use X% for PLA" or whatever. For practical purposes, you just empirically figure it out with test prints based on a few simple rules of thumb:

Use lots of cooling for PLA, moderate cooling for PETG, and minimal cooling for ABS. (Note that sometimes ABS does benefit from gentle airflow, and PLA shouldn't necessarily always just be blasted at max power.)
Use less cooling on big prints where each layer takes a long time, more cooling on small prints where each layer is very quick.
Axial / box fan? You'll probably want to run it at full power. Radial / squirrel cage blower? You may want to run lower power.
Overhangs curling up or sagging? More airflow may be needed. (Lower layer heights also help enormously.)
Hot end temp sagging when the fan kicks on? Try less airflow. (Or insulate your hot block better.)
Weak layer bonding? Try less airflow. (Or raise your hot end temp.)
Small, fast prints getting mushy or corners "pulling in"? You need more airflow. (Or lower heatbed temps.)
Print warping / corners lifting off the bed? Try less airflow, particularly on the lowest few layers. (Or higher heatbed temps, or a better adhesion layer, or less nozzle/bed gap for the first layer, or any other approach.)
Fan too noisy? Try less airflow. (Or get a better fan.)
Filament stringing during travel moves? Try less airflow pointed directly at the nozzle. (Or tune your retraction settings better, or get the moisture out of your filament, or lower hot end temp.)

Outstanding answer, this was exactly the compilation of knowledge I wished for.

I use side-wind to cool down model as simple as possible. It's just a 12cm in diam fan which is driven from arduino (the same contacts as the fan next to the nozzle). No duct, no other stuff. The only thing I consider in terms of making things better is to set up 2 fans which could coll down model from both sides.
The issue is that when model is more complex then cool air is not reaching out oll these crannies and then on some corners I see the difference. Because of this issue I have to orient model facing to the fan in the way which will decrease such effect and I'm usually happy with results. If you are able to imagine how the airflow behaves then you can achieve perfection :)
Of course fan is driven but to be honest I usually use 100% of its blowing power except with first layer which I usually don't blow at all.

I am pretty fine with the fanduct, it's a so far pretty proven design that can be found here: http://www.thingiverse.com/thing:953811 But I'm glad to hear that your implementation of the part cooling is simple and still works. Thanks for that input. Now I'm still waiting for someone to explain what is ideal and why ;)

Sure sure, I'd also like to see other's solutions. Of course I also got that kinda fan as you have (a bit simpler one) but I still use side-wind because for smal details there is no enough time to cool down printing area especially when nozzle immediatelly jumps to next position (where there is no cooling flow) and then quickly gets back. This is where side-wind works for me.

I use PLA and both my fans stopped working. I am not techy and couldn't figure out how to fix them so I set up a house fan that blew directly at the motor keeping it cool and it works as good if not better than the fans that came with the 3d printer. You cannot let your motors over heat because your filament will get curled up insize the nozzle.So try that before buying 3d printer fans.

Hi, Jeanie, and welcome! I think what Kamuro is referring to is how to control fans for cooling the model during different parts of the print process. Motor cooling is also required in some cases, but I suspect that might not be the issue here. However, in your case, could perhaps the fan cooling the motor also indirectly cool the print? :-)

yes it cools the print too which seems to work perfectly   :-)

How does letting motors overheat make the filament curl up?


text:
What is the influence of a lower BAUDrate?
I am using a BAUDrate of 115200 since I cannot make a connection to my printer with the advised 250000 rate. Are there any downsides or limits I reach earlier given by the lower BAUDrate?

Are you experiencing any issues that you suspect could be related to the baud rate, or are you just asking in general? :)

Baud rate for 3d printers has diminishing return on speed.  Your printer can only go so fast.  The computer sending the data goes a lot of waiting for your printer to catch up.  At 115200 is so fast going above that isn't going to make a great deal of difference unless your printer is super fast.

Baud rate is the rate at which information is transferred in a communication channel, given as a number of bits per second (bps). So a baud rate of 250000 is capable of transferring a maximum of 250000 bits per second (31250 bytes/s). When working with serial ports, both ends of the communication line will have to "talk" with the same speed - the same baud rate - to understand each other.
So when using a baud rate of 11520 you will theoretically be limited to transfer data with about half the speed of 25000. If you are transferring large amounts of data, this might be a limiting factor for your application, but if you are not pushing the limits of your serial port, it probably won't matter at all.

it looks like i was writing an answer a bit too long :)

@darthpixel, I think you bring up some good points on the effect of low baud rate, though! :)

Whoever -1 this, please comment why...

So this depends mainly on instructions/time. ist there a general rule of thumb, lets say, 'if your mordel is with lots of directional changes, you can only go to speed xx mm/s', or single cases which have been documented? (I'd also be interested in the downvote reasons, - this is an excellent answer)

I don't think you're likely to lower the baud rate to the point where it's slower than the actual machine. Lower baud rates can be a good thing if there's a lot of noise in the signal, such as can happen with cheap cables. It's like talking more slowly to help someone understand you. I prefer to simply use the SD card on my printer and take my PC out of the equation.

@kamuro, on some delta printers you will notice a significant lag if you try to navigate the menus while the printer is doing calculation intensive moves, in my case due to a limited CPU. :) John, the increased S/N-ratio is very interesting! Thanks for sharing. I also stopped printing from USB as you don't need additional variables with 3D printers at the moment.. :)

Thanks for the insight. Delta printers and sloggish LCD response is a known issue with non-32bit Arduino processors. Quintessentially I take that I don't need to worry about the lower BAUDrate if I stay under 200mm/s and super complicated models I guess ;)

hey guys - delta calculations and lag of LCD has nothing to low baudrate I suppose, hasn't it? It's a result of managing everything by small cpu. Or - more precisely - it's a result of slow cpu and wrong (or lack of) interrupts processing I would say.

@darthpixel, that is true, although some might suspect it is related if one does not know what baud rate is! ;-)

@kamuro, I doubt you will ever have to worry about the baud rate if it just is related to streaming gcode over USB: the calculations for moving the printhead are performed by the printers hardware and not your computer (the gcode is interpreted differently by each individual printer/firmware)!

...and that's why we have to choose a firmware for which the gcode will be generated

@TormodHaugene: I know, it's only for transmitting the gcode. But if we never need to worry about it, why was a non-standard BAUDrate chosen to begin with and not the standard 115200?

@kamuro, that is a good question. Apparently you can squeeze out baud 2000000 from 16MHz Arduinos (note the hack in the last post), although the reference states a max of 115200. On the other hand, baud 250000 is apparently used in the DMX, which there even is a external Arduino library for.

If your printer doesn't have an SD card then the whole communication between computer and arduino is performed "live". There is kinda buffer of data which arduino can swallow. Then it needs to process it (and then can send some reports to your app) and then arduino is ready to get new "set" of instructions to work on.
Now. If a baudrate is to low then there could be a situation when arduino finishes its job and has to wait for new bite of data. In such a situation you can see the printer pauses printing as it waits for signals from arduino as it waits for data from computer. That's more or less a downside of a low baudrate.
If you have a SD card then the data is sucked from it but reports are still send by port to show results on screen. In such situation you can see sligtly late screen update.
A screen means just a fun of live preview but breaking printing process (caused by late data send) means your hot nozzle stays over the same position which can destruct a surface or even fry up a plastic a bit. It also oozes and therefore creates lasting artifacts.
Resuming - low baudrate is evil ;)

So this depends mainly on instructions/time. ist there a general rule of thumb, lets say, 'if your mordel is with lots of directional changes, you can only go to speed xx mm/s', or single cases which have been documented?

Of course if your slicer will cut a curve into too many pieces then it could appear but... if you don't tune up (or rather derange) slicer/firmware/baudrate too much then I think it will not come up. I cannot find an article I've read :(

If a GCODE line is about 30 characters (which is about the norm), you can send at most 420 of them per second at 115200 bps.
If each GCODE prints 0.15 mm (for example in arcs), you would be limited to 63 mm/s in arcs/circles (straight lines are not an issue).
If that's limiting for you, then you should find a way to set 250 kbps.
You don't mention the firmware you use, but if you use Klipper, which compresses data over the serial line, connection speed is not an issue.

I was hoping to see a quantitative answer for this. Great! Keep in mind the slicer may generate gcode lines shorter than 0.25 mm in order to avoid exceeding max deviation. Anywhere in the range 0.1 to 0.5 mm is typical depending on a mix of model resolution and slicer settings, so this really could be a limiting factor at significantly lower speeds than 64 mm/s.

50 bytes is also quite a long line: G01 X247.951560 Y11.817060 Z-1.000000 F400.000000

The Z is excessive (in practice there won't be any appreciable Z movement except in vase mode) but you forgot the E component. In my experience print (extrude-and-move) lines are about 30 characters each, so I'd say apply a factor of 3/5. They're of the form G1 Xxxx.xxx Yyyy.yyy Eee.eeeee.


text:
Irregular 3D printed part
I tried printing from an STL file on the QIDI TECHNOLOGY 3DP-QDA16-01 Dual Extruder Desktop 3D Printer QIDI TECH I. They recommend using the MakerBot software with the Replicator(Dual) profile. The 3D print that I tried is messed up.
The material used is PLA.
Could you help me determine the cause? The following pictures give more details:
(All settings which are not shown are Makerware default settings)
1 The 3D model

2 The printed sample

3 The Settings

Your print isn't cooling fast enough. With small, thin prints like this, PLA needs a fair bit of airflow to solidify before the next layer goes down. Your printer doesn't appear to have a proper print-cooling fan, so I have two suggestions:

Print two or even three of the part at the same time, spaced a fair distance apart on the build plate. This will give each of them time to cool.
Point a box fan into the front of the printer to get good airflow over the print.

I agree with RyanCarlyle on this:

Your print isn't cooling fast enough.

Please regard this answer of mine that covers a few options to help with the issue you're encountering. Pay particular attention to the layer times, and active cooling.
The essential take-away from my answer (linked above) is this:

Increase Layer Times. Increasing Minimum Layer Duration (Device Settings -> Minimum Layer Duration) will provide the material with more time to naturally cool down closer to its environment's temperature. What this does is ensure that the latest layer is mostly solid before the machine begins printing the next molten layer. If you don't let the previous layer of plastic solidify enough, then plastic gets pushed/pulled around when the machine moves, adding more plastic; thus resulting in the issue you see in your images. The caveat with this approach is the obvious impact on the overall runtime of your print and should ideally be done more or less as a last resort.
Active Cooling. Active cooling is typically done using an additional fan, often times mounted directly in front of the extruder. The act of active cooling provides a quicker and more direct means of cooling the printed plastic. However, depending on machine design, you may see more variability on other places such as dependability in extrusion temperatures. This can be more detrimental with cheaper spools of PLA and especially poorly designed machines that can't properly maintain extruder temperatures. Active cooling is, however, very common and seems to work for the majority of 3D printer enthusiasts and doesn't impede on runtime.


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How to keep Z-axis motor from slipping when powered down
Because of the weight of my Z-axis and the relative ease of its motion, when the Z-axis motor is powered down the bed has a tendency to slip and fall down.
Obviously leaving the motor powered solves this problem, but that is not ideal.
I am looking for some kind of solution that passively stops the Z-axis motor from slipping; some kind of brake or clutch. Ideally I'm looking for something that I can add onto my current motors and that I could print myself. Commercial solutions (preferably ones that could be replicated with a 3D printer) would also make valid answers.

The simple way to do this is to use a self-locking screw pitch. Pretty much any single-start thread using a sliding nut cannot be back-driven so the load will not fall. Normal 8x8 trapezoidal thread screws will easily back-drive because of the steep pitch.
Likewise, a worm drive between the motor and Z stage will hold the load. You would want to switch from screws to belts for the main motion stage in that case though, to avoid having too much total gear reduction.
Both of these solutions will limit your maximum Z speed, of course. But they're simple and reliable. Clutches and brakes add a lot of complexity and must be actuated somehow. Designers who want the load to stay suspended almost always simply use single-start screws.

Nice answer, but I was looking for something that I could add onto my existing setup, without replacing my current leadscrew.

Replacing the leadscrew is by far the easiest option. Anything else you do will be more complicated and/or decrease your Z stage performance. Doesn't really make sense to me why you'd be willing to install something between the motor and screw, but not replace the screw.

The first, the simplest and the chippest solution (as described by Ryan Carlyle) is to use self locking screw - no doubt.
But I understand you already have your printer. Changing screw (thread rod) is a bit complicated I suppose. As it also needs to change "nuts" and change control settings and so on and so on. So in my opinion, in your case, it's much simpler to change motor to one with break or at least the one with permanent magnets which would hold some torque to support your bed.
Another solution which would also not require to exchange your existing parts is to use kinda ratcher driven by solenoid which would work as a break when deenergized. Where to install it, how to ensure it will hold your bed or prevent your threded rod from rotating is another issue but all options I suggest doesn't need to destroy your existing construction. They all work as additional part.
If you would be so kind and reveal some photos of your design, it would simplify to find proper application of solenoid break.

It should be possible for you to add a counterweight. Pulley at the top, and a string / wire / etc up from the build platform, over the pulley, and back down to a hanging weight. You'll probably want two, one on each side.
This won't directly prevent the motor from slipping - but it will lessen the amount of force trying to make the motor slip.
Note that it will decrease the maximum z-axis acceleration downwards, but will increase the maximum z-axis acceleration upwards. Unfortunately, downwards is the direction that matters for a print.
Also, you could try a circuit to short out the motor when the unit is powered off. The simplest thing would probably be a relay. Note that this could cause issues if the circuit fails in shorted position unless it also disengages the controller input. (This may not be enough to prevent movement, however, just slow it.)

Adding c-w is generally well known solution to decrease power consumption as then motor just rewinds cable (string). But in a device as delicate as 3Dp it's hard to apply. #1 c-w needs to counter-weight so it should weight close to equally to the bed. #2 c-w needs to be stabilised but in 3Dp we have rapid mvments in X & Y - inertia will swey c-w and will have influence on printout quality. Creating a circuit which will shortcircuit or crosscircuit Zax motors is ok but only if you can do it well and not manually operated, otherwise sooner or later you will fry up something (probably stepsticks)

The only good, safe way to balance the Z stage weight is a constant-force spring. That would be a good approach. Actual counterweights add moving mass and can cause some bad resonance/ringing type effects.

Good to know. Though, that being said, any suggestions as to where one could find a constant-force spring for a decent price? One nice thing about a counterweight is that it doesn't cost much (if anything).

If your stepper motors have shafts protruding from both ends then it may be possible to simply 3d print a fixture that allows a thumb screw to be tightened and clamp down on the unused part of the shaft.
This would however be a very manual approach and would require you to be mindful that the screw must always be disengaged just after motors are powered on..


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What are the parts that make up a hotend, and what do they do?
My first and only 3D printer is a Printrbot Simple Metal, which has a hotend that doesn't expose any of its internal parts. Easy for beginners, I suppose: "The hotend is that tube that heats up the plastic and deposits it on the print bed."

But I've been trying to learn more, and many hotends out there don't look quite as simple. My Printrbot hotend probably isn't as simple as it looks, either.
What are the parts that make up a hotend, and what do they do?
(PS: This is a general question, not specifically about the two example hotends above.)

This varies by hotend design. The following is a list of components which you might find in a typical hotend, but note that different designs may integrate these components to some extent. For instance, on the J-head the heat block, nozzle and heatbreak are all one and the same component whereas on the E3D hotends these are all separate parts.

Nozzle: This is the part where the filament comes out. It takes in the molten filament (typically as a bead of 1.75mm/3mm) and tapers down to the nozzle size (typically around 0.4mm). These are typically made of brass for its good heat conductivity, but brass is not suitable for printing abrasive materials (such as glow in the dark and metal-filled filaments) so sometimes (hardened) stainless steel is used.
Heater Block: Usually made from aluminium, the heater block joins the nozzle to the heat break and holds the heater cartridge and thermistor.
Heater Cartridge: most hotends use a ceramic heater cartridge, though some older designs use power resistors or nichrome wire. This component is, as the name suggests, responsible for heating up the hotend. The heat block usually clamps around the heater cartridge to provide good contact.
Thermistor: This part senses the temperature of the heat block. It is usually a small glass bead with two wires attached (which are typically insulated with glass fiber or teflon). For high-temperature printing, a thermocouple may be used in stead.
Heat Break: this is the part where hot meets cold. It usually takes the form of a thin tube and is made of stainless steel for its low thermal conductivity. The goal is generally to have the transition be as short as possible so as little of the filament is in a molten state as possible. It connects the heat block to the heat sink.
Heat Sink: the purpose of the heat sink is to cool down the cold side of the heat break. It is typically cooled with a fan. Most heat sinks also have a standard groove-mount for mounting to your printer. The heat sink usually has grooves to increase its surface area and cooling capability.
Teflon Liner: some hotends have a PTFE liner that guides the filament through the heat break into the nozzle. This makes it easier to print PLA, but compared to an all-metal hotend, limits the temperatures at which you can print (making it difficult to print PETG and impossible to print polycarbonate).

The ubis hotend you mentioned is a bit simpler than this, and simply uses a big chunk of PEEK in place of the heat break/sink. PEEK has very low thermal conductivity and thus passive cooling is sufficient. However, PEEK limits the temperatures at which you can print.
Here is an illustration outlining these components on an E3D V6 hotend:

Note that in this image the Teflon liner only goes into the heat sink, and not into the heat break or block. This means the maximum temperature is not limited by the Teflon, but if it did go all the way in (as is the case with, for instance, the Lite6) then it would be.

Excellent. Thanks! If you'd like to further improve your answer, perhaps you can include links to the specific hotend brands you mention (and/or additional images, if you think it would make things clearer).

I recently switched from my old Ubis hotend to the E3D-v6. It can be mounted to the Printrbot Simple Metal with only a minor adapter and it's working quite well. +++ PS: I've learned through painful experience that the heat break is very fragile... twice. The first time, I over-tightened the assembly, and the heat break tore apart. The second time, the heater block pushed on the printer frame while homing the Z-axis, and the heat break bent out of shape. Warning: Make sure that the heater block on your E3D-v6 faces forward when mounted to a Printrbot Simple Metal!

@MarcusAdams The default is aluminium. Quickest reference I was able to find for this is this page by E3D which offers an upgraded copper heater block which they state has some advantages over the usual aluminium.

picture on the left
This hotend is made out of PEEK plastics (beige). It can work in temperature upto 250C. As it is also good heat insulator then it doesn't need to have cooling fan. Red part on this picture is just a cover (insulator) of the heater which heatup nozzle (gold). Black are just wires and connectors.
picture on the right
This hotend is metal so it needs two things - cooling fan and heat barrier. Beginning fron the left - red wires are connected to (silver) block which is heater itself. Between the block and this round silver part (which is a heatsink) there is heat barrier (thin pipe which is poor heat conductor). Heatsink has plastic funnel (blue) which directs an airflow from fan (black) through heatsink.

Thanks! But this answer is a bit too specific. My question was supposed to be general, only using those two pictures as examples.

no doubt Tom's answer is ultimate :)


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Adjusting Bed Temp values on Monoprice/Wanhao I3 (Repetier Firmware)
I have a Monoprice Maker Select, which is a rebranded Wanhao Duplicator I3 V2 (Prusa clone).  I've found that the heated bed temperature values on the LCD are incorrect.  The heater works, and the controller maintains the bed temp just fine, but the temperature reported isn't the true temperature.  When using the PLA preset, with the bed set for 60°C, once the temperature stabilizes at 60°C on the display, I can measure it with a laser thermometer and get a consistent 54°C across the buildplate.  With the ABS preset of 90°C, I read 80°C.  And with the bed set for the maximum value of 120°C, I'm only reading 102-104°C.
I've checked these values with the bare aluminum build plate, and I've allowed the temps to stabilize for at least 10 minutes to ensure that I have consistent readings.  I believe the the firmware is using the wrong temperature curve for the thermistor in my device.
I had hoped that there was a simple scaling constant that I could adjust, but that doesn't seem to be the case.  I've researched enough to learn that my device is running Repetier 0.91 firmware, and this page on temperature control on the Repetier wiki says that each type of thermistor needs a custom voltage->temp lookup table, and talks about building a custom table in "configuration.h".  I've tried to follow this line of research but I feel like I'm going around in circles.  It sounds like I could build a custom version of the firmware to install on my printer, and in doing so I could potentially specify a better conversion table.  This gives me pause for several reasons:

I haven't found any online reference to other people installing a custom Repetier build on a Wanhao I3.
I have no idea what values to use for the temp conversion table.
I can't even find anyone else reporting my issue.
I'm fairly new to this; I rather not brick my printer, and I haven't found any good guides to installing firmware on the device either.
I'm not convinced this is the right option.  Should I be looking at replacing the thermistor instead?  And if so, what's the correct part?

I've also looked into the Melzi board inside the printer hoping for a variable resistor to tweak the thermistor voltage divider, but no such luck, at least in the schematics.
I could just live with it; I've been using a 67°C setting to achieve a true 60°C bed temp for PLA, but I'm starting to work with ABS and I'd like the option to get above 100°C bed temp.  Am I on the right track? Suggestions?  I'm still pretty new to the device and 3D printing in general, so I may have overlooked something obvious.
Update: additional question in light of Tom's answer: what is the expected max actual bed temp achievable on a Wanhao/Monoprice I3?  I'm measuring 100°C with an LCD reading of 120°C, but I'd like to get to 110°C if possible.

It is completely normal for the surface of the bed to be cooler than the indicated temperature. The thermistor goes on the underside of the bed, near the heating traces. The top of the bed (which is further away from the heating traces) will naturally be cooler.
It would be possible, though a lot of work, to build a custom thermistor table that more accurately reflects the surface of the bed, though that means your thermistor table will no longer reflect the characteristics of your thermistor, but instead reflect the particular circumstances under which you build your custom table (which would be affected by ambient temperature, any drafts, ...).
The accuracy of an infrared laser thermometer depends on the characteristics of the surface you're measuring for, so unless you adjusted the thermometer specifically to measure the aluminium surface of the bed, it's possible your thermometer is off as well.
The exact temperature of your bed doesn't matter anyways (you just need it approximately in the right ballpark) so I would suggest to just live with it. The 60C/90C figures are not supposed to be for the surface of the bed. They're meant to reflect the temperature reported by the printer. That said, 90C is a bit low for printing ABS (but the bed/power supply on your printer might not be powerful enough to get any higher).

"The 60C/90C figures are not supposed to be for the surface of the bed" - I had wondered about that, though I found that getting an actual 60°C on the bed produced better adhesion for PLA, and the actual 80°C I measured for ABS didn't hold my test print beyond about 10 layers.  Are there established heated bed targets for PLA & ABS?

@JasonClark I aim for "true" surface temps of 55C for PLA and 95C for ABS (measured via IR gun on a non-reflective surface like a patch of blue tape, or contact thermocouple). 110C true surface temp is way too hot for ABS since the glass point (where it fully solidifies) is 105C. Many people recommend very high bed temps for ABS as a way to make up for poor first layer adhesion, but this causes various print quality issues depending on the print size and geometry.


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Sanguinololu 1.3a fan connection
Can anyone tell me where to connect a cooling fan on the Sanguinololu v1.3a board?  A few of the information pages mention three PWM outputs: Extruder, bed heater and fan, but none of the wiring diagrams that I can find, actually show the connections for the fan.

It appears that there isn't an "out-of-the-box" solution to your request, but luck is with you. Someone with your board and objective has posted what appears to be a reasonable modification:
http://www.instructables.com/id/Add-a-Cooling-Fan-to-your-Rep-Rap-Sanguinololu/

Yes, this confirms what I was beginning to think and it is a mod I can handle. Thanks.


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How to calculate the approximate volume of material used in 3d print?
Is there a reasonable way of approximating the volume of material used for 3D print by knowing only the STL file volume and infill percentage?
Or what is the formula for calculating the exact volume and which parameters can be fixed to reasonable values?
Can this be done easily using Slic3r or CuraEngine in command line?
Note:
Supposedly 3Dhubs use Cura[*] software to calculate the print volume.
Any help is appreciated.
[*] www.3dhubs.com/talk/thread/calculate-print-volume

by knowing only the STL file volume which else volume do you want?

Are you sure you want the volume, or are you asking for the amount of print material required to print?  The volume does not depend on the infill percentage, but the print material usage does.

@emackey Yes I am sure, I would like to know the volume needed independent of material type. It does depend on infill. With low infill the voids in the final print will be greater and thus the volume also. But any help is welcome. Do you know how to calculate amount of material required using CuraEngine?

@dsalaj, so what you are saying is that you want to know the volume of the material used, and not the volume of the final print?

@TormodHaugene You are right. I was ignorant thinking these two are the same. Obviously the volume after melting, cooling, etc. will change. I was able to work out the volume of material used know simply by using the filament length (calculated by Cura) and filament diameter.

@dsalaj, so you found your answer then? Good to hear. :) Would you mind adding what you found out as an answer to this question and accept it? That will make it much more visible and useful to other users!

@TormodHaugene Thank you. Yes I have. I only need to figure out how to do it from command line with CuraEngine. I will do that, thanks.

Just as a small addition: Slic3r gives the amount of used filament in grams when slicing in Repetier. I find this very helpful because it my filament spool is also bought by weight. And I know the weight of the final piece.

Use simplify 3d. It is built in!

Possible way to calculate the volume of material used is to multiply the filament length (calculated by CURA after slicing and displayed in lower right corner) and surface of filament tip.
Volume = Filament_length * ( Filament_diameter / 2 )^2 * PI
Of course do not forget to convert all values to the same order of magnitude (e.g. cm³).

This is the correct answer for the volume of material used as talked about in the comments.  Note that a traditional geometric volume of the final print would of course include the interior empty space between infill supports, not just the volume of the material used (for example, print a watertight model and dunk it in water, check the amount of water displacement).  But for material used, this is the correct formula.


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Monoprice Select Mini - Detached Filament Feeder fitting
The $200 Monoprice Select is inexpensive but also cheap, so experiences I've seen appear to involve lots of repairs.  In spite of that, I've bought one, as I'm able to fix things (sometimes) and the first few prints have been pretty good quality.  ( I hear this unit is also sold as a Wanhao I3 )
First repair was that the control knob only worked in one direction (fix: bad encoder-PCB connector cable. Repaired)
Upon trying to change filament, the feeder fitting that enters the hot-end heatsink has come off. This fitting has a thread, but strangely the heatsink does not seem to.  As I tried to unscrew it, to check for a feed blockage, it just let go, and I see no part that could have held it in place.   (See pic)
I'm guessing that it was just epoxy-glued to the heatsink. Sounds kludgy but possible.  Does anyone know?
Can any other owner verify how theirs is attached?
[ Also, posted as a caution for someone else who tries to do this. :(  ]
Thanks in advance.

Solution - there is a set-screw and a square nut in that T-slot which holds the feeder fitting in place on the heat sink.
One may well think (as I did) that the fitting is threaded into the heatsink, since it does have a big hex-head for a wrench. A small turn an the set screw lets go, the nut sliding down the slot with it. Thus when you inspect it, you don't realize they are involved 'cuz they aren't around.
Simply slide back up and you're in business.
Mystery solved - thx to Mark on Twitter. :)

Do you have a link to the twitter post?


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What does "Uses Mains Voltage" mean on this 200*200mm Square Silicone Heater Pad?
I keep thinking it means that I can plug it directly into my power supply instead of running it though my RAMPs 1.4; is that correct?
Here is the link to it, 200*200mm Square Silicone Heater Pad.

As typhonic points out in his answer, the product description is very confusing, suggesting that 12/24VDC be used, and then that 120/240 VAC can be used. I have written to RobotDigg for clarification

"Mains voltage" is the alternating current provided by your wall outlets (eg 120v in USA). In order to use a mains voltage heatbed in a 3d printer, you will need to wire up your controller to switch an AC SSR. That way, your low-voltage-DC RAMPS board can control AC current.
If you plug a heatbed directly into a power supply, it will never stop heating, and may burn itself up or even cause a fire. Don't do that.
Because mains voltage has enough voltage to kill you, it should only be used for STATIONARY components, such as the PSU supply wiring and Delta heatbeds. With moving beds, particularly Mendel/i3 style Y-beds, wire fatigue and rubbing can expose the electrical conductors and create a serious safety hazard.
200x200mm is a very reasonable size for a DC bed heater, so there's really no good reason to use an AC heater here. It's more complex and less safe. I recommend getting a different heater.

What is an AC SSR?

basically - solid state relay - element which uses low voltage to switch on/off high voltage

"How do I wire an AC SSR with RAMPS" would be an excellent thing to ask in another question.

I wouldn't say a mains voltage bed is less safe than a low-voltage DC one. While AC has the potential to kill you, the current needed for a DC bed is much higher. Therefore you need thicker conductors (which are less flexible and more likely to break due to motion) and higher rated terminals. Considering the majority of printer fires are caused by the high current of a DC bed melting connectors, there's a good case to be made for a mains-power bed, especially considering that earthing mitigates the risk of wiring getting exposed. With RE complexity, a DC heater requires a PSU, AC does not.

@TomvanderZanden In terms of current and under-rated wiring/connectors, yes, I agree absolutely. I'm a strong proponent of 24v systems over 12v for that reason. But anything over 40V puts the equipment in a different class as far as regulatory requirements and safety certifications, simply because it has the ability to kill someone almost instantly on contact. Having all the mains-voltage AC stop at the UL/CE certified PSU is a major testing time+cost advantage for manufacturers. So you're very unlikely to see AC beds on anything but large hobby builds. And those cheap AC SSRs often fail-on!

[edit]
I just noticed you've mentioned "mains voltage"
DON'T DO THAT
If there is 12V on your heatbed and your power supply gives 12 V then you can do it but there will be no control over your heating procedure.
How does it work?
RAMPS is connected to Arduino and then through Arduino to your computer. So applications can say to Arduino - hey, heat it up up to 70°C. So Arduino sends this command to RAMPS and RAMPS is switching on heating, meantime it measures temperature and sends this measurement to Arduino so it knows if your heatbed is already at 70°C or not. Having that knowledge Arduino can decide to still heat it up or rather switch the power of the heatbed off.
If you connect your heatbed directly to your power supply then all of the above controlling sequence will not take place.
Imagine to connect your lightbulb directly to the wall plug. You can do it but then you will not have any chance to switch it on or off. Right? ;)
So in my opinion - don't do that - don't connect your heatbed directly to your power supply.

@Ryan Carlyle - how was it possible to double post??? :D

Note that if you plug a mains heated bed directly into your (12/24)V power supply, it will barely heat up at all (because its resistance is far too high). I don't think the "don't do that" in all caps is warranted, since it suggests there is some kind of danger.

@TomvanderZanden I did think the same way at the beginning till I realised he mentioned "mains voltage" which suggests using 120/250V but not 12/24V

The heater pad described in your link is designed for 12 VDC or 24 VDC. Therefore, the term Mains Voltage in the description is misleading and probably wrong. Read the voltage and power requirements again and it appears that the heater pad can be connected directly to the RAMPS 1.4 without an external relay or SSR.

The pad in question actually has three wires coming off of it; two red ones and one black one.  And it reads 12V on it.

That is correct. The reason for three wires is so that you can hook it up to either a 12 VDC supply or to a 24 VDC supply. The hookup will be slightly different depending on the supply voltage you use. I cannot tell you exactly which connections to make, but my guess is: for 12 VDC connect the red wires together and to one side of the power and connect the black wire to the other side of the power. Even though the links says you can go directly to the power supply, I still recommend you go through the controller. The description on that link is badly written.


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Needing a simple fix for loading TPU
My question is...
Is there a SIMPLE/easy way to load TPU without tearing my printer apart to insert a hose that probably wont work anyways. It keeps curling up by the cog. I have read a few topics in other places but I didn't like the answers. Hoping you all might have a simple fix.

Loading TPU/TPE can be particularly challenging because many printer loading scripts run too fast for the soft flexible filament to effectively purge whatever normal filament you were using before. A couple tips:

Load with a slightly higher temp than either the TPU or previous filament require, so as to minimize the melt viscosity and reduce the force required.
Make a custom gcode file that contains a slower loading routine: wait for heat, then advance the extruder at a very slow rate for a long distance. Then you just "print" this gcode file whenever you need to load TPU.

However, simply being able to load is not necessarily enough. Not all extruders can reliably print flexible filaments, period. The larger the gap between the pinch wheel and inlet to the hot end, the more likely the filament is to buckle and come out the side. You need to make sure this gap is as short as possible. If there is more than a couple mm of gap, you'll need to make gap-filler or print yourself a new extruder designed for flexibles.
Printing slow and without major velocity changes can help, too. Use relatively low layer heights and low, constant feedrates so the extruder doesn't have to run fast or change pressure often.
Harder flexible filaments will be easier to print if your setup is borderline. Ninjaflex is one of the hardest to print because it is relatively soft. Semi-flex type filaments are much easier to print if your hardware isn't set up optimally.

I've noticed that the first layer seems more prone to wrapping flexible filament around the drive, particularly if the nozzle is a bit on the low side. The extra extrusion force required to push the filament against the resistance of the bed means that the filament can't sustain enough pressure without folding.
As a quick workaround for this, I lowered the extrusion multiplier to 60% on the fly for the first layer (as well as keeping the speed right down).


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Printing an iPhone Case
I am trying to 3D print an iPhone case, however, I want it to print standing up. Is this possible to do?
I have a picture of the case in the link below.

It depends on your printer. If you have a multi-material printer with soluble support, you can just print it with the star on the base and let the support raft take care of it.

Yes this is possible. For an FDM/FFF printer, you'll need to print with supports. I might also recommend printing in PLA to minimize the chance of warping during the print (from experience).
It might also help to slow down the feedrate to ensure smooth surface finish and avoiding delamination on such small layers.
You'll probably see a decrease in the surface quality on the inside due to the printing of support scaffolding depending on the slicing engine you use.
However
You'll want to pay attention to the strength of the case. If you print the case upright then it will be more susceptible to breaking without post-processing.
Conclusion
Ultimately, if you can get away with it, it would be better to subtract the star instead of extruding it in the model. Then you can simply print the case back face down on the plate with much better results.

The "however"-bit is a very important addition. If printed like this on an FDM printer it will break the moment you look at it.

It's important to consider, but it doesn't mean that it can't be done. I've personally printed a few [working] phone cases for myself in the past with this orientation, but I specifically designed the backing to be much thicker than a typical phone case with 3D printing in mind.

Not sure if this should be an answer or a comment, but not quite enough rep to comment, so...
Here's an off the wall suggestion:
As an alternate approach, assuming you're using FDM printing, could you print it with the star down on the bed in more than one step?

Print only the star.
Put suitable material around the star that is similar to the bed or usable as a bed material, possibly filling the voids as well.
Either print the rest of the case, hopefully with it adhering to the star, OR, print the rest of the case and use solvent or glue to adhere the star, (this latter step could be done with the star removed and printing directly onto the bed with the rest of the case only), OR, with the first star removed and the foreign support in place, reprint the entire case including the star - which would go into the empty space where the first star was printed and removed.  The first star print then just serves to allow accurate placement of the foreign support if you need that.

I've never tried this, so I can't offer assurances.  The two step print, with the first star in place and the rest of the case printed after filling the empty space probably won't work if you need a heated bed, as for ABS.

Support structure & Orientation
Carefully considering this model, It would be wise to print this on the back-plane with support and then post-process the print to prevent the walls separating from the back when dropped. By activating support, the proposed orientation is however quite possible. To reduce the chance to destroy the print, one has to choose the right support material and geometry. In this case, a soluble support (PVA) would be best, but choosing a proper support structure like tree support originating from an area in front of the case reaching in, for example, generated with Meshmixer is also a very good solution. The orientation that is shown by OP actually has a very nice ability to hold onto the phone from the C-shaped cross-section. However, again this does demand some post-processing to strengthen the inter-layer bonding, preventing the case to split into an "upper" and "lower" section when dropped.
Post processing
Post-processing could take the shape of baking the part in the oven for about an hour to strengthen the inter-layer bonding. For PLA 90 to 100 °C in the oven is common, while ABS is a little higher.
ABS would allow a quick acetone vapor smoothing, which melts the outer layer lines together smoothly and as a result increases the shell stability a little - you have to let it outside to let the soaked in vapor fully evaporate afterward though and you might lose smaller details.

You have a few options. First. I would change the design. Why not make it negative space instead? Else as the other user mentioned, glue the star on later.
Other options are, come up with a modular design so you do not print it as one piece.
From there you can do some more advanced things such as print it with the star up and use HIPS as a support material -- assuming you have a duel extruder
http://reprap.org/wiki/HIPS
You could print it with normal support material, with the star up, and just accept that the left overs will scratch the phone, or spend a lot of time with some hand tools and sand paper.

Another good tip is to add some model supports directly into the model that you can just break off. Like some wings in an X along the corners of the case. So pressure is exerted more evenly across the case as it's being built. Using a big Raft will help too.

Consider printing in other planes - this model would be very suited to be printed at around a 45° angle.
You will need support beneath it, but all visible surfaces should exhibit good quality as well as being more robust than when printed upright due to layer adhesion as pointed out by other answers.