text:
What is causing 'droplets' on first layer?
I recently changed filament and for starters it worked perfectly well, but quickly I got some problems with my first layer. It's like droplets are forming on the surface (finished item + 3 undersides):

The final part is (for me) okay but I'd like to get rid of those pesky 'drops'.
As the defect is quite stable and quite recognizable and it happens all the time, I bet somebody more experienced than me knows what's going on!
Info:
I'm using a 1 week old eSun filament, a E3D V6 Hotend 1.75mm on my scratch CoreXY printer, short Bowden direct drive, Repetier, Marlin, Linear advance (M900 K60 so quite low).
The print is done using a 0.4mm diameter nozzle at 0.2mm height at:
50°C(122°F) heat-bed and 214°C(417°C) hot-end for first layer, then lower a bit to
40°C(104°F) heat-bed and 211°C(412°F) hot-end.
I use Blue-painter tape.
Worked perfectly well with my black eSun and my white eSun.
What's my problem?
Thank you all!
[Edit]
Tried about everything (more temp, less temp, fan on item, more / less bed temp, underextrude, moving around z delta, removing linear advance, radically lowering speed) but the only thing that worked about okay (problem was quite reduced but didn't go away totally) was to bump up the layer thickness to 0.3mm
[Edit 2] Finally it seems it was, as it usually is, a conjuncture of several problems that I will list here:

The bed was not perfectly flat
The heatbed moved/bended when going from a hot first layer to a colder second (and on) layer
Maybe the speed was a bit high for the first layer (25mm/s)

I fixed this by installing a borosilicate glass bed on top of the heat bed which ensures a perfect flatness.
I had to change my inductive sensor to an 8mm one (insteéad of the 4mm I had previously added) to make this function. I think it is not as good as it can be as it detects the heatbed under the glass (which is not perfectly flat), but it's enough for now. I'm thinking about how to make the glass conductive, like aluminium or something, but that's for another day/post.
I also put blue tape on the glass because the first layer was tricky. This might be because the inductive sensor doesn't do its job that well (see above).
Heatbed temperature for first layer: 70°C
Extruder temperature anywhere from 190°C to 220°C works fine, that was not the problem, or it is no longer a problem.
I also lowered the first layer speed to 20mm/s because the first layer didn't stick easily directly onto the glass, with blue painters tape it sticks even too much so I'll try higher speeds. It did mitigate problems though so it might be a path to try if you run into similar problems.
And now it seems that it works even amazingly well, I just have to print something really big to see!
---------------Old:
Moving z up made spaghetti :-) and different temperatures made quite extreme warping:

What's the step size in the Z axis for your printer?

I used 0.2mm getting these problems, 0.3mm works better but still not perfect. Or maybe you are wondering about the setup? It's a classic nema 17 with microstepping and a "lead screw" (http://cpc.cx/ld0) pushing a cantilever build plate running on two vertical 8mm (IIRC) rods with (2+2) linear bearings.

First of all, thanks for all the help, it really is a nice community!
But none of them actually helped and I finally find out what to actually do to fix the problem so here it goes:

Extruder temperature didn't change anything (made it worse under 190°C/374°F)
Speed didn't change anything (tried as low as 10mm/s)
Z tuning didn't change anything
Using 0.3mm layers instead of 0.2mm made it slightly better but still completely unusable

So, what did the trick?
I figured that it was extreme warping, so heating up the heatbed to 80°C/176°F and the first layer comes down really good, for the rest of the print I use normal temperatures and it works okay. For overhangs I bump some degrees and point a small squirrel cage fan on the overhang.
I think the filament is damaged or that this particular color might be a bit different than other colors, but well, now it works!
[Edit] From a recent firmware upgrade the heatbed PID was disabled, re-enabling it really made it simpler too.

Mine is more of an educated guess than a definitive diagnosis, but it looks to me like if your printer may be overextruding (it's difficult to say with certainty with this particular picture, but your top layers too do not look as good as they should).
I wonder if you have calibrated your extrusion for this particular spool of filament?  This is something that you should do for each and every new spool of filament, regardless of whether you have already used the same brand and material, as different batches and colours may differ slightly in diameter or hardness, and both factors can lead to a different overall flow out of your nozzle (I just checked eSun website, and they state "Accuracy:1.7-1.8mm", and 6% variance is quite a lot).
Possibly unrelated, but 211+°C is also quite on the high end of the correct temperature for printing PLA (if that is what you are using).  Still in the range recommended by the manufacturer - so it should be ok - but you may wish to try bringing it down a notch (205°C perhaps?).

Hi @mac thanks for answering! For the overextrusion, I'll try but the rest of the parts (after the first layer) are quite perfect (thin walls are right size and so on). Calibration goes with this but it's really close to 1.75mm diameter. I'll try lower temperatures but I already had bad adhesion between layers with lower temp, maybe I need "high" extrusion temp but lower bed temp? Will try.

@Valmond - As I said, mine is no more than an educated guess, so I may still be wrong.  Keep in mind though that even a massive overextrusion of 10% would only translate in 0.04 extra millimiters on a thin wall, which is below the accuracy of most calipers (0.05mm).  More in general, over-extrusion is typically only a problem on bottom and top layers and if you print with 100% infill, otherwise a typical print (2-4 layers of shell + infill < 100%) won't be affected much, as the excess plastic will simply be pushed around slightly.  That said: I may still be totally wrong! :)

If both black and which filaments give you no problems, then maybe the colorant (beautiful color btw) is changing the print qualities a bit.  I would definitely calibrate your extruder, then I would try lowering print temperature a bit and fiddling with live z.  Your live z may be a teeny bit close to the bed.

Additionally, you shouldn't need tape for PLA.

@ctilley79 Yes it's possible this new beautiful color is somewhat different. I'll fiddle around and report back, but your comment about being close to the bed hit me, I am and it's great for getting that first layer down because my prints warps a bit when they start with an over hang... I'll check that out, thanks!

For the tape, it's just convenient / easier IMO. Also when something really sticks, I can just remove the tape.

@Valmond It seemed to me that when live z is too low, you get a little plowing like that in the first layer. Hope things turned out well.


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Making a plunger
Help, I know how to print simple cookie cutter style molds, but I need to know how to turn that open shape into a closed smaller version that can be used as a plunger.  Reason being, is I make bath bombs, so it would be so much easier to get bombs out of molds if I could make a plunger.  Thank you so much for any help!!

It's important to provide information regarding the program you are using to model your molds. Even without that information, there are general methods to produce the portion you require.
Consider that you already have the outer portion, what you describe reasonably well as a cookie cutter style. If you are using someone else's model cookie cutter shape, the following will still apply.
Most programs have a subtractive feature. An easy program that provides this feature would be Tinkercad. Running with that program, the steps would be as follows:

import the current cookie cutter shape
scale up the shape to ensure
that the inner portion is decreased, by increasing the wall
thickness. It is expected that scaling up the shape will enlarge both
the outside wall and inside wall of the cookie cutter shape create a
block that will encompass the cookie cutter, circular or rectangular
as desired.
use the subtractive feature to remove the cookie cutter
shape from the block
this should also segment the outer portion of
the block, which would be removed, leaving the inside cookie shape.

source: Stack Exchange

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Cooling time query ABS
I printed Thingiverse "Benchy" at the default Anet settings for ABS, hot end and bed, as a first test. The result was fair but needs a bit of tweeking. The model was removed from the "hot bed" and set aside to cool (room temp 23degC). However when I took the model to work next day (to show off obviously) the poor wee soul looked more like the wreck of the Hesparus with cracking across many of the layers. Any thoughts? Splitting was on the side closest to the fan.

As you may already know, ABS is one of the trickiest materials to print with, partly because of its high thermal coefficient, which in turns leads with warping and cracks when not dealt with properly.
The keys to successfully deal with this aspect of ABS are two: cooling it slowly and cooling it uniformly. Typically you achieve this by using an enclosure.
Enclosures can range in quality and price dramatically: there are professional grade ones that are fire and sound proof, maintain a negative pressure, filter the exhaust air and cost a few thousands euros... or you could get away with something as simple as using a cardboard box.  Probably, one of the most common solutions is to use an IKEA lack table and some acrylic or wooden panes as it provides a durable, effective solution at a very low cost.
Anyway: the reason why an enclosure works is because it traps the air that has been heated by your heating bed, thus "immersing" the full print (not just the bottom layer) in it.  In turn, this means that:

The difference between the extruded temperature and the final one is less.
The gradient of temperatures across the height of the printer volume is also less.
The print is shielded by random air drafts, like the one you would generate by approaching the printer to check it
When you stop applying heat (print is over, heating bed off) the print will cool very gently.

Now, about that fan...  Using a fan actually increases the speed at which your part cools, so - intuitively - one may believe a fan is a bad idea with ABS.  However a fan is essential if your print has any type of non-trivial overhangs, and - in general - prints done using a fan (in any material) have better details.  Again, with an enclosure, using a fan is seldom a problem as your fan will cool the ABS rapidly but only down to the temperature of the air in the enclosure (most commonly somewhere between 50°C and 80°C).
If your print is very small (like a benchy) and you don't want to try with an enclosure, you could still try to improve your situation by:

simply reducing the speed of the fan (so to only "partially cool" the part)
using a fan duct that distributes the air jet more heavenly around the extruded filament.  Typically these are 3D printable parts that you find in forums and groups of a given printer model users.  Here's a semi-circular one for the Anet A8, for example.

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What's the best printing technique to produce splints (a device to immobilize a body part)?
One of the most interesting field in which the 3D Printing is being considered is the fabrication of biocompatible devices and parts for a medical applications.
For that I am interesting in knowing what  technique are used for the fabrication of splints or cast used for the immobilization of human body part, also which material is compatible with this technique?

I am pretty sure any material and manufacturing process that needs to be used in a medical environment is subject to tight regulations that are possibly country specific.  Materials like lead - commonly found in FDM printers parts that come into contact with the filament - are potent neurotoxins, and exposure to some additives used in resins and plastic polymers is also considered a health hazard.  So beware that even if the answer may turn out to be "FDM printing PLA", both the printer and the PLA may be specialised "medical grade" ones.

@Mac please say more about "lead commonly found in FDM printer parts". This is news to me

Lead is often used in metal alloys to alter their physical properties.  For example, it is very common to find it in machined brass parts (a nozzle is precisely that) as it increase its machineability.  Basically you should consider any metal part touching the filament (cog wheel, hot end, nozzle, ...) as a potential source of contamination unless you are positive of the contrary.

I'm voting to close this question as off-topic because it is a) too broad and b) a list question asking for 1) techniques 2) materials

The photo you posted is of a cast that was printed using Nylon and FDM, or the extrusion method. Source: https://www.evilldesign.com/cortex

@mac: Lead is not present in fdm printed parts in any appreciable amount. You can do the math with mass of nozzle, percentage of lead in brass, maximum loss assuming some ridiculous enlargement of orifice due to wear, etc. and affirm this. Stop with the ridiculous FUD.

@R.. - Your math may be right, but you are missing the general point: it's not that if you use a off-the shelf machine you will necessarily die or get sick.  It is rather that medical equipment gets tested and certified so that you can be sure you won't.  Lead contamination is most definitively one thing it is commonly looked at.  Lead soldering is for example forbidden in medical equipment, even if patients don't get in direct contact with the electronics.

For anything where there is an open or bandaged wound, you should NOT use 3D printing, and should use sterilized medical equipment to prevent infection and heavy metals infiltrating the bloodstream.
SLA/SLS 3D printing may be the best option for replicating the complex structure of the splint you have pictured above, as FDM printers have difficulty reproducing those structures.
However, FDM printing CAN reproduce it, and generally FDM printers have access to a wider variety of materials of which models can be printed with, so they may be the best option overall.
For something to immobilize a body part that has been broken, you may want to use a stiff material such as ABS or Carbon Fibre, However PLA may work still in these cases.
As for something to support a body part, Flexible or Semi-Flexible materials may be desired, such as Ninjaflex (TPU), Nylon.
As a disclaimer:
I am not a medical professional, This is not medical advice, please consult a properly licenced medical professional first before using 3D printing to solve a medical ailment.

PLA is very stiff, moreso than ABS I believe. That means it's also more brittle though.

note that you could arguably print the splint flat, then heat it some in an oven and wrap it around the bandage, creating a perfect form fit.

That could work aswell, i never thought of that

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Issues with direct g-code transmission via serial port
Model of the printer is unknown, got it as present, probably something generic cartesian on arduino mega and ramps boards stitched together and with marlin firmware.
I've used accepted answer from here to try moving this thing from terminal.
How to directly send G-code to printer from a Linux terminal?
My first attempt to get access to low-level printer interface looked like that:
./baud.py <> /dev/ttyACM0 250000
tail -f /dev/ttyACM0 &
cat > /dev/ttyACM0

First it was fine: i've entered g-code, printer executed it and returned an ok message into my terminal.
Then i've turned the printer off and on again and repeated the whole process, but now tail -f didn't output anything and printer LCD displayed garbage in the status line after I ran the command.
I've also noticed that printer controller reboots every time the serial port is accessed, not sure if it happened in the first time when everything worked well.
The output of cat /dev/ttyACM0 after baud setting is a bit weird too - and there's garbage in the status line instead of standard "%printername% ready" as well:
start
echo:Marlin1.0.0
echo: Last Updated: May 20 2017 18:12:04 | Author: (none, default config)
Compiled: May 20 2017
echo: Free Memory: 3763  PlannerBufferBytes: 1232
echo:Hardcoded Default Settings Loaded
echo:Steps per unit:
echo:  M92 X80.00 Y80.00 Z3200.00 E97.94
echo:Maximum feedrates (mm/s):
echo:  M203 X50.00 Y50.00 Z2.50 E25.00
echo:Maximum Acceleration (mm/s2):
echo:  M201 X750 Y750 Z100 E10000
echo:Acceleration: S=acceleration, T=retract acceleration
echo:  M204 S500.00 T500.00
echo:Advanced variables: S=Min feedrate (mm/s), T=Min travel feedrate (mm/s), B=minimum segment time (ms), X=maximum XY jerk (mm/s),  Z=maximum Z jerk (mm/s),  E=maximum E jerk (mm/s)
echo:  M205 S0.00 T0.00 B20000 X20.00 Z1.00 E5.00
echo:Home offset (mm):
echo:  M206 X0.00 Y0.00 Z0.00
echo:PID settings:
echo:   M301 P22.20 I1.08 D114.00
echo:SD init fail
echo:Unknown command: "starto"
ok
echo:Unknown command: "SD init failstartuthor"
ok
echo:Unknown command: " (none, default config)50.00 Z2.50 E2rBy00.00 Y0.00 Z0.00echo"
ok
echo:Unknown command: "Unknown command"
ok
echo:Unknown command: " "starto"own comm"
ok
echo:Unknown command: "aximum XY jerk (mm/s),  Z=maximum Z jerk (mm/s),  E=maximum E jerk (mm/s)echo"
ok
echo:Unknown command: "PID settings"
ok
echo:Unknown command: "okechecho"
ok

The "SD init fail" line and everything after it appears when sensor data appears on the LCD, there's a delay before that during which the LCD is empty.
If you send commands to printer using something like echo "G0 X10" > /dev/ttyACM0, it executes them only on next serial port accessing (and therefore reboot) - or doesn't execute at all.
The interesting part is that Cura "Monitor" tab can actually manipulate the caret and the Cura itself can print things in general - but i want to be able to do it manually.

That's weird but i've got some code from here: https://stackoverflow.com/questions/6947413/how-to-open-read-and-write-from-serial-port-in-c , changed it a little, removed few lines, ran it - and my port started working just fine. Here's the complete code (for Linux of course).
I guess that was the c_lflag line that solved the problem.
#include <asm/termios.h>
#include <stropts.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>

int set_interface_attribs (int fd) {
    struct termios2 tty;
    memset (&tty, 0, sizeof tty);
    ioctl(fd, TCGETS2, &tty);
    tty.c_cflag&=~CBAUD;
    tty.c_cflag|=BOTHER;
    tty.c_ispeed=tty.c_ospeed=250000;
    tty.c_cflag = (tty.c_cflag & ~CSIZE) | CS8;
    tty.c_iflag &= ~IGNBRK;
    tty.c_lflag = 0;
    tty.c_oflag = 0;
    tty.c_cc[VMIN]  = 0;
    tty.c_cc[VTIME] = 5;
    tty.c_iflag &= ~(IXON | IXOFF | IXANY);
    tty.c_cflag |= (CLOCAL | CREAD);
    tty.c_cflag &= ~(PARENB | PARODD);
    tty.c_cflag &= ~CSTOPB;
    tty.c_cflag &= ~CRTSCTS;
    ioctl(fd, TCSETS2, &tty);
    return 0;
}

int main() {
    int fd=open("/dev/ttyACM0",O_RDWR|O_NOCTTY|O_SYNC);
    set_interface_attribs(fd);
    close(fd);
    return 0;
}

Oh, the marvels of running code without knowing what it does! ;)

Mine is a wild guess, but judging from:
echo:Unknown command: "starto"
ok
echo:Unknown command: "SD init failstartuthor"
ok
echo:Unknown command: " (none, default config)50.00 Z2.50 E2rBy00.00 Y0.00 Z0.00echo"
ok
echo:Unknown command: "Unknown command"
ok
echo:Unknown command: " "starto"own comm"
ok
echo:Unknown command: "aximum XY jerk (mm/s),  Z=maximum Z jerk (mm/s),  E=maximum E jerk (mm/s)echo"
ok
echo:Unknown command: "PID settings"
ok

It looks like you may be looping back the output of your printer as an input to itself.  I am very suspicious of your line: tail -f /dev/ttyACM0 & as that seems to indicate your are trying to perform other actions in the same terminal window after you started to monitor the serial connection.
If this is the case, you should definitively open the monitor in a separate terminal (tail -f /dev/ttyACM0) and feed the input in a different one (note that yo must not use the final &).
Finally, you probably want to use cat >> /dev/ttyACM0 instead of cat > /dev/ttyACM0 as you want to append your commands without truncating the existing stream.

It's not tail -f /dev/ttyACM0 & output, it's cat /dev/ttyACM0 output. And it was in newly opened terminal window, even baudrate was set in another one.

@KarashevichB. either you misread me or you are thinking the commands do something different that what they do. :) tail - f fname will output the last bits of "fname" and keep on outputting lines when they are added to it.  cat > fname will use whatever you type or get as an input on the active console as a input for "fname". Note that this is very different that cat fname!!

As you can see from echo:Unknown command: "Unknown command" your printer seems to have received its own response "Unknown command" as a command itself, at some point.

Also, if you run the tail command in it's own console, you don't want to use the final & and you want to use >> instead of > (see my last edit).

Whatever. The problem was actually entirely different, something with serial port parameters set wrong by default. Running set_interface_attribs from accepted answer from here https://stackoverflow.com/questions/6947413/how-to-open-read-and-write-from-serial-port-in-c on my port solved the problem somehow. Don't know how did i get the port working in the first time but oh well.

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Printing Chocolate with Ramps 1.4
Is it possible to print chocolate or food using Ramps 1.4? I have seen printers that are capable of printing food. But I am not sure if there is one that is open source. Does any of you have any experience printing food? Thanks

chocolate in "normal" form once melted loses temper. It's difficult, perhaps impossible to re-establish the temper of the chocolate once it's been extruded. Work-arounds exist with compensating mixtures, but that removes the pure chocolate aspect from the food product. Not an answer, hence the comment, for consideration.

I use an open source and very cheap model: you probably have all the parts you need to build it right in your kitchen too! https://3.bp.blogspot.com/-pJXV-mEySlE/VPaNe-HaR4I/AAAAAAAAGUw/vCNBJobxxZE/s1600/7_DSC1045.JPG ;)

It's somewhat possible to reduce/mitigate/eliminate the loss of temper by not overheating when melting. While not easy for the average person, a machine might just manage it (or a more complex machine could perhaps re-temper before printing.) (see scene 6 here: http://www.goodeatsfanpage.com/season8/chocolate/chocolate_transcript.htm)

The controller interface board (that being the RAMPS 1.4 you ask about) should be up to the task and not care WHAT it's printing. You'll probably be creating your own hotend design to pull this off, and if you make it open source, then it will be. I'm envisioning stainless steel, careful temperature control, lots of mixing, perhaps some sort of screw-feed extruder (or batch-fed plunger with the melting and filling under close control on a separate machine, then the hotend on the printer doing a fine and careful job keeping the temperature right at 91.7 °F around the plunger.) You'll have design work to do on the mechanical hardware side, but the electronics and software should be easily adapted.
Read up some on food equipment design to make sure whatever you come up with can be cleaned appropriately for food handling, and uses only food-safe contact surfaces and lubricants/bearings.


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Wrong temperature on extruder 2
Firstly, I just bought a G2S mini pro from Geeetech and it is my first 3D printer (therefore I'm 100% newbie in this area).
The first extruder seems to be ok, the temperature varies from 23°C to 201°C and if you touch it you can see that it is hot. However, for the second extruder, the temperature is shown with more than 400°C:

The cables are connected correctly and the firmware is updated.
Do I have to return the printer? Or is there another solution?

If you have access to an IR thermometer, it would be interesting to verify what the actual temperature is.  I doubt the hot end actually reaches that temperature, but:

if it actually does, then it could actually be dangerous, as most extruders are designed for temperatures well below 300°C.  The problem would likely be in the firmware in this case.
if it stays cold, then probably is a problem with the temperature probe or its cables/connectors being broken. Most printers use thermistors as temperature probes, and thermistors let less and less current pass through the higher the temperature is, so: no current would be interpreted as the hot end being "extremely hot" and the firmware would not heat the hot end further.
if it is hot but at another temperature than the one displayed, then it could either be a problem with the probe over-reading or a firmware bug (e.g.: the temperature is shown in Fahrenheit, or the firmware mis-process the signal from the probe).

Either way: thermistors and cables are cheap to replace, while problems with the firmware may be fixed only if you have access to the code.
If you just bought the printer in a physical store, I would simply swap it with another unit, rather than fiddling with it, though.

The tempeature is cold, but the cable is connected...

@HolaSoyEduFelizNavidad - the cable could be broken inside, the connector could be defective, the thermistor could be broken... A tester can help diagnosing where the circuit is interrupted... but replacing the unit (if it is an option for you) seems the cheapsst surefire option...

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text:
What causes "ghosting"?
I am printing some minion chess pieces for my teacher at school and on every model I have found something called "ghosting", or at least I heard that is what it is called. For example there is a strap on the model for the pants. And going left and right there is very shallow "straps" or something happening.
I am interested to know what causes this to happen and how to fix it. It is not super bad, but would be nice to fix.

Your question would greatly benefit from a picture of the piece with the ghosting. :)

@mac I will work on uploading a picture once I get the chance. I only have this happen on these objects with all sorts of details, like these minions. And also, thank you greatly for the answer below. I found it be very useful for me.

Ghosting is an artefact in the print due to the vibrations in the printer that are induced by rapid changes of direction.  It is important not to confuse them with inherent vibrations in the printer due for example to the belts being loose or the bearings not being in perfect order.
The good news is that it is relatively easy to tell them apart: ghosting (also known as "ringing" or "ripples" or "waves" or a number of other names...) is always downstream of a change of direction, and fades rapidly.

Inherent vibrations - on the other hand - tend to be consistently present when printing along a given direction, and do not fade.

Mechanically, ghosting works like this:

The moving part is travelling along - for example - the x-axis, when suddenly the direction of movement becomes the y-axis.
At that moment, the stepper motor of the x-axis stop rotating, but the momentum of the moving part stretches the belt even so slightly past the intended stop point.
At this moment the belt becomes like a rubber bend / spring, absorbs the kinetic energy of the moving mass and releases it by "throwing" it past the intended stop point in the other direction.
This keeps on repeating a number of times, but at each pass, some of the energy is dissipated, and the moving mass moves less end less away from the ideal stopping point.
While all of the above is happening, the object has also begun to move along the y-axis, so the extruded plastic looks "weavey" along the y-axis.

Understanding how this process works, makes it possible to understan why the three main factors affecting ghosting are:

The amount of mass being moved
The speed, acceleration and jerk settings
The elasticity of the mechanical components

Namely, mass and speed are important because their product is the momentum.  That in turn means that diminishing either one of the two will reduce the amount of "overshooting" past the stopping point.
Elasticity of the mechanical components is important as the more flex/stretch the part can take for a given amount of force, the more overshooting a given momentum will result in.
Finally, acceleration and jerk are important because - simplifying things a bit - the faster the change of direction happens, the less time the system has to adjust without vibrating.
So, concretely... what can you do to fix/reduce ghosting?  Three things, of course! :)

Reduce the mass being moved.  Depending on the geometry of your printer, the mass being moved could be the bed+print, the printing head, or an entire gantry.  These are normally considerations done when designing the printer itself, and engineers normally mitigate problems by using lighter materials (plastic over metal, aluminium or carbon fiber over steel, etc...), or adopting different designs (like using a Bowden extruder instead of a direct one, to save the weight of the stepper motor).
Reduce speed, acceleration and/or jerk.  Speed is normally the safest bet, as - besides your prints taking longer - there is really no penalty for it.  Acceleration and jerk - on the other hand - can cause overestrusion at sharp corners.
Reduce the elasticity of the system.  This is commonly achieved by tightening the belts and eventually switching to more rigid rods / tracks / rails.

A couple of resources that may come in handy for you to understand and solve the problem better:

A really nice article with illustrations (two of which I "stole" for this post)
A test model specifically designed to highlight any possible ringing problem with the printer.
A video showing lots of different test prints done with various settings (very useful to understand how changing the above parameters affects the print).

To expand on the #3 solution: reducing the elasticity of the system, if you have your filament mounted on the top of your printer, placing the filament elsewhere on a separate spool holder can also reduce ghosting. Tightening the belts and moving my filament got rid of ghosting for me on my MP Maker Select.

I am in the process of printing some belt tension-er(s) from Thingiverse. I am hoping that by tensioning the belt I will get ride of ghosting, just like you. Unfortunately I have to by more belt because te x-axis is to short by a quarter inch, shot down! Anyway, thanks for the answer!


text:
Extruder driver not working
I have a geeetech g2s pro and when I request to print something, the extruder motor doesn't move (it is connected on the board), therefore, the printer prints some kind of imaginary object. I cannot ask Repetir host to extrude it as prevents moving when the extruder is cold, and when it is hot all the repetier host does is moving the header up. Is there a way a could test these motors without needing a hot extruder?
Here you have a picture of it, maybe it is upside down.

Found the solution, I had to swap the cables on the board, now they are working.


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3d printer drip problem
I have a problem with my 3d printer. When I am printing, the printer seems to drip.
I am very confused because I never saw this before and I do not know what to do.
I attach a picture of it.
Why does this happen?
Thank you very much for yours ideas.
DATA:

Printer: Anet A8
Material: PLA
Temperature: 200ºC

I Have enable retraction and I tried to disable it without changes...

Closely watch those 2-3 first layers and you'll have some good ideas about what's happening (or what is not happening).

I have two theories to offer.
It is really dripping.  If this is the case, the likely culprit is a loose part in the hot-end, namely the nozzle/heating block coupling, or the heating block/heat break one.  If this is the case, you should be able to see it by visually inspecting the part.  The solution in this case is to fully disassemble the parts, clean them thoroughly of any remaining plastic, and reassembling them while hot.  This is essential, as parts that are assembled cold have the tendency to come loose when heated (due to thermal expansion).
It is overextruding, and the nozzle collect and drag around the excessive plastic, until the blob is big enogh to detach and remain on the bed.  If this is the case, then you should calibrate your extruder, and the nozzle height.

You are right.
There is a leak of PLA on top of the heating block.
So I'll have to disassemble it :-(
Thank you very much for your help.

@Jnavero - have a google around for how to disassemble the hot end.  The heat break expecially, that you will have to unscrew, is rather fragile.  Even if the part is loose, you may have to warm it up before disassembly, as the cold plastic may act as glue.


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Changing the home position on a Prusa i3 MK2
As part of a project with my university, I have developed a new extruder to attach to a Prusa i3 MK2. My problem is that both the nozzle and PINDA probe have moved 17mm forward and 0.5mm to the right. As a result when I try and calibrate the printer it moves to the home position and the PINDA probe is too far out over the heatbed so it doesn't detect the printing surface. What is the simplest method of moving the home position so that the printer can be properly calibrated?
UPDATE:
I am planning on removing the heatbed and placing spacers that will move the printing surface 17mm forward. This should then prevent the printer losing any printing area and hopefully prevents me having to edit any code. Can anyone see any problems with this I'm overlooking?
The simplest thing to do would be to move extruder 17mm closer to be the same as the original printer but my deadline is fast approaching and I haven't time for a redesign that large.

This may sound stupid (it does to me, but...), but: move the X and Y limit switches by the same distances.  Keep in mind that, as fred.u points out, you will want to offset the max travel limits so that the head never crashes into a hard stop.

Hi Carl, yeah i was considering doing this but the PINDA probe wouldn't have enough travel to reach the back line of calibration points

Consider the original installation with the orientation of the Pinda probe to the nozzle. Let's say for argument's sake that the Pinda probe is 3 mm to the right and directly in line with the nozzle on the y axis.
If you examine your new nozzle, I would expect that the relationship of the nozzle to the Pinda probe no longer matches the original spacing.
If possible, re-design the mount to place the Pinda probe in such a way as to match the original design.
Thanks for pointing out my oversight, Mac. If the relative position of the nozzle and pinda probe are as the original, the solution is then in changing the appropriate parameters in the firmware.
I found a reference for someone who had a bit smaller error in home position, but the concept is the same.
The link above points to information reading thus:

In Configuration_Prusa.h:
Code: Select all // Home position
define MANUAL_X_HOME_POS 0
define MANUAL_Y_HOME_POS -2.2
define MANUAL_Z_HOME_POS 0.15
// Travel limits after homing
define X_MAX_POS 250
define X_MIN_POS 0
define Y_MAX_POS 210
define Y_MIN_POS -2.2
define Z_MAX_POS 210
define Z_MIN_POS 0.15

it will be necessary to connect the printer via USB to a computer running an Arduino IDE and to load the Prusa specific files for that printer. Edit the noted location, save/write the configuration and test.
I would suggest small adjustments in only one or two parameters at a time, to avoid ambiguity in the cause/result sequence.

I understand the OP to say the relationship hasn't changed ("both have moved..."). ...or maybe I am misunderstanding your point?

Thanks for the answer! I've no experience at all editing code but I'll give it a go. The distance between the PINDA probe and the extruder has remained the same

IIRC,  Cura has settings that will define those min/max and zero offsets for you.

@CarlWitthoft - those settings are used for producing the gcode, here the problem is likely to be the self-calibration routine ran by the firmware.

What is the simplest method of moving the home position...

I think the solution outline by @fred_dot_u is very elegant, so I would go with it.

...so that the printer can be properly calibrated?

I'm not sure that will be possible.
Because the physical lenght of the axis hasn't changed, by moving the nozzle/probe, you have actually reduced their reach in the opposite direction, so the probe may be unable to travel on top of the intended calibration points (the usable printing area has also shrunk, but that's less of a problem).
If that is the case, I can't think of an easy solution (bar not using the auto-calibration feature altogether).

this is more of a comment.

@CarlWitthoft - Can you articulate? My intent was answering the question "how can I have the printer calibrating correctly?" with an explanation on why this may not be possible... but I'd be happy to be educated on any rule I may not know about posting answers! :)


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Simplify3D and Davinci mini
Simplify3D is listing the XYZprinting Davinci mini as a compatible printer for their software. I would never buy such expensive software in combination with this printer if I didn't already think of buying a better printer.
Can anybody confirm compatibility with 'out of the box' configuration and up to date firmware?

Be aware that Simplify3D offers what they call "Risk-Free Guarantee": the possibility to try the software for 2 weeks and get refunded 100% if you aren't fully satisfied.

@tmartin Why you need this information if you never would buy the software? but... works great!

@FernandoBaltazar read the whole sentence, not only the 1st half.

@tmartin you have my answer in my comment, not in the question.

XYZPrinting printers use a .3w file format vs GCode on all opensource printer designs.  I have used Simplify3D since the first month I obtained my Da Vinci Pro 3 in 1 which also has WiFi enabled.
Simplify3D does not connect very well to my Da Vinci WiFi so a 25ft ActiveUSB extension makes the connection for uploading and monitoring the progress of the print.
All the XYZPrinting Da Vinci series are available on the printer configuration wizard if not then sending a request to Simplify3D will obtain a response with the printer configuration file.


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3D850 stuck in the nozzle
I am trying to use a 3D850 PLA filament which is supposed to work without any issues with any PLA printer. As a printer, I use Dagoma NEVA which is supposed to work with any PLA filament. I can print with the filament without any issue, but I encounter a problem when I need to swap the filament. Somehow 3D850 sticks within the nozzle and even when it's heated I have to push really hard with another filament to push the current filament out (usually when the nozzle is heated up I can just easily push a filament inside for it to come out of the nozzle).
Is there any special behavior of 3D850 that may cause it to stick inside of the nozzle?

Consider overheating the head to further decrease the viscosity of the residual material in the nozzle.  Then, of course, return to design temperature before printing.

@CarlWitthoft the max temperature for Neva is 220º C (according to https://3dprinting.com/pricewatch/3d-printer/dagoma-neva/) and this is what their "nozzle cleaning mode" uses. I am wondering in general if I'm doing something wrong because print temperature for 3D850 is 190-230ºC and I printed it at 210º. I can try printing it on 220º but I don't understand why I cant remove the filament easily.  So far my other experience was only with Verbatim PLA. The recommendation for it is 200-220º and it perfectly worked at 210º

My guess is that  particular brand of PLA is changing state inside the nozzle as it cools. Quoting from the manufacturer's page,

Materio3D PLA uses the NatureWorks Ingeo 3D850 polymer, specially
  engineered for 3D printing. It is tougher and stronger than standard
  PLA and can be annealed for improved heat resistance and toughness!

If the residual material in the nozzle cools slowly enough (at the end of a print) to anneal, then by design it won't re-melt at the same temperature as the raw filament material.   I would recommend changing your gcode so that the extruder hotend is held at temperature after a print completes, and making sure to clear the nozzle with an alternate type of filament before allowing the nozzle to cool.
quoting from another page,

To achieve a heat treat on a printed part, submerge in water (or bake
  in oven) at 200F for up to 30 minutes.

notice that's Fahrenheit, well below extruder temperatures.

I'm totally fascinated by this explanation, +1, but it has to be noted that all PLA can be annealed, so to a certain degree, all filaments should manifest this behaviour. Also: holding the hotend hot indefinitively without extruding is likely to cause clogging the first time you forget about it, I would suggest instead that the OP use G4 or equivalent code to delay the shutdown of an amount of time sufficient to purge the nozzle.

@mac  I suspect all PLAs do show this -- Whenever I restart, and do a "push-through," the initial glob is definitely stiffer to push out than when I'm feeding fresh filament by hand.

Annealing affects the structure, and maybe the behaviour around the glass transition, not so much the fluid transition. There could still be some baking/polymerisation or loss of solvent though.


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Any code to move up Z axis after finishing the printing?
Is the firts time that I saw this movement after the printing has finishig and causes the nozzle crashes to the printed part and I noticed due the part is 14x8 and the nozzle is to near and below to the border of the shape. I supposed that some scripts has changed but, seems to be everything ok.
this is the end script:
G92 E0
G1 E-1.5000 F1800
; layer end
M104 S0 ; turn off extruder
M140 S0 ; turn off bed
G28 X0  ; home X axis
M84 ; disable motors
; Build Summary
;   Build time: 3 hours 9 minutes
;   Filament length: 12689.1 mm (12.69 m)
;   Plastic volume: 30520.78 mm^3 (30.52 cc)
;   Plastic weight: 38.15 g (0.08 lb)

Z axis moves down 4mm after finishing going to X0, why? I don't want the nozzle crashes the part on going to zero.

You can use:
G91
G1 Z10

G91 make the printer use ralative positioning, while G1 Z10 would move the gantry up of 10mm, reagrdless of its actual position.
In order to understand what's going on, you could experiment with the position of those lines in the script.
The safest bet it to insert them at the very top, but you could insert them straight after the homing of the X axis to understand if the drop you are seeing is caused by the homing command itself or by the ´M84´ one.
My guess is that the drop is actually caused by the latter.  M84 doesn't really "disable motors", rather it stops using energy to keep them still (i.e.: it stops the idle hold).  What I believe is happening in your case is that when you stop the idle hold, the weight and mechanical play of the X gantry causes it to move slightly (a bit like when you relax your body on the sofa and you "sink" in it a bit more).

This is actually very dangerous if you print at the max Z height, you then would not have the extra 10 mm.

Care to elaborate? The worst thing that I can think can happen is that the stepper motor will skip a few steps.  Not a big deal...

E.g. acrylic frame printers are less sturdy, steppers are powerful and do not skip, I've seen this happen on my first printer.

There is something fundamentally wrong with your z-motor drive if both screws are dropping the gantry at all.
Try a couple experiments.
 Write a quick script to move the head somewhere up high, then terminate without the X-homing command.  See if the z-axis moves.  Ditto for X-home but not motor disable.
Write any script, and while the gantry is up high, pull power and see what happens.
That will at least help narrow down the list of possible problems.   In the meantime, please post your printer, the motors, and the driver board/firmware in use.

"There is something fundamentally wrong with your z-motor drive if both screws are dropping the gantry at all" - Only if this was happening with idle hold ON.  Without it, it may just be the sign of a nearly frictionless Z-axis mechanical system.  Just to name a printer with such a build: the Cetus, with a common problem on their first batch being that on power-off the nozzle would come down crashing on the building plate (see https://youtu.be/D_i3vAV7EJ4?t=42s).

I will check on the next prints if is a common movement since m84 is active to disable motors.

I´ve printed several parts and the problem is no appearing again, I thought that could be  a large printing than the other one and I waited 3.5 hours and nothing. However just for printer's safety I will use G91 G1 Z5. Mechanically I think that is not possible that extruder can fall easily like cetus printer since mi printer is like Prusa i3 (screw support). But any overheat, magnetic field, Electrostatic interference, or a ghost could affect on that time; I will monitor all possible issues.

After two years I never had the same problem, but still I wondering why happened and remembered this issue yesterday while I was using the printer as  plotter.


text:
Is there any setting that could allow me to print this overhang without support?
I've been asked to print a set of this:

https://www.thingiverse.com/thing:2200026
I used Slicer with my default settings for my FLSun printer which includes support and 0.2mm layer height and that rail was printed as whole block with some excess which would allow me to remove the support, but that didn't work because the support simply melted with the top part of the rail.
Tried again with no support and the first layer of the top part of the rail simply felt because there was nothing there to support it.
Is there any configuration that would allow me to print this bridge overhang correctly? Maybe printing the rail diagonally?!
Any help will be appreciated.

What orientation are you printing? I would orient it as though it were an ice skate blade  and print without support.  At worst you might have to clean out the "lower" channel slightly after printing.

First of all a minor correction: the feature you are trying to print is not a bridge (which is an unsupported length of filament between two parts of the print) but rather a overhang (which is an unsupported length of filament supported only at one end).
The reason why your overhang is impossible to print without support is that slicers create a shell first or - in other words - trace the perimeter of the layer you are printing.  This feature, combined with the fact that your overhang is perpendicular to the part it originates from, causes the printer to try to extrude into thin air the perimeter of your rail, like this (the yellow lines are the shell, the red ones the infill):

In the image above, also the infill is extruded into thin air, but this is actually something that you can change in most slicers (look for "infill pattern orientation" or something similar).
One option you have is to tweak the support parameters to make it unobtrusive and easy to remove, like for example this:

(The above was done in Cura, with infill pattern "lines", spaced 5mm apart and no support interface or other additional structures).
Since your parts won't be subject to a great deal of mechanical stress another solution could be to change their printing orientation.  In the following example, the overhangs do actually become bridges and as such should print without problems:

Just consider it will take considerably longer to print.

I don't think I could print it without support on my setup (Simplify3D + DeltaRocket). The first thing I'd try is to print it vertically.

Hey, that's what I said in my comment!  :-)  .   Well explained.


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Inductive kickback protection?
Is there an integrated kickback protection in stepper motor drivers or should I make my own?
I am afraid the steppers might fry the driver or the arduino when i turn off the power for them.
I do that by turning off the power supply.
I haven't had an issue yet but it still bothers me.

What's this have to do with 3D printing?

Kinda, sort of, but not really. I'll look at the A4988 (datasheet).
The motor pins are connected by diodes to ground and Vbb (the motor suppply voltage). Essentially, they act as a bridge rectifier making any back EMF or inductive spikes appear (rectified) on Vbb. If you were to suddenly power down the driver this could cause a rather large spike on Vbb.
According to the datasheet, there is a 40 V Zener on Vbb which will clamp the voltage to that level. (Another popular stepper driver, the DRV8825, does not appear to have this Zener - always check your datasheet!)
So, yes, there is inductive kickback protection. However, it only clamps the voltage to 40 V. Depending on the rest of your circuit, this could be quite damaging.
The datasheet recommends that a 100 μF capacitor be placed on Vbb. If you are driving a typical stepper motor with 2 A and 4 mH coil inductance, the energy stored in the coil is 8 mJ. This energy is only enough to take the capacitor up from 12 V to ~17.5 V, so if you have a large enough capacitor on your stepper driver (as you should!) then you're protected against inductive kickback.
Note that if you move the motors by hand then you can still build up a higher voltage on Vbb. I've heard anecdotes of people who damaged their printers like that.

"Inductive kickback" from motor coils is caused by the inductance of the coils and the wiring.  It is not some strange effect.  Inductance is charged with current, just as capacitance is changed with voltage.  Most bipolar motor drivers use an H-bridge on the output.  By driving the H-bridge correctly, the driver can continue to provide a path for the motor current when it is no longer applying voltage, such as by connecting both wires of a motor to ground.
Although some may find it counter-intuitive, connecting the Vmot side of the motor to Gmot, while the other side remains at Gmot, keeps current flowing in the coil more smoothly and with lower losses.  The voltage across the motor coil is near zero, so there is little voltage trying to change the motor current.  If the coil is undriven and subject to the clamping diodes, the voltage across the motor will me much higher, and the current will stop faster.
The higher ripple current in the motor increases the coil heating, may increase audible noise, and decreases the efficiency of the drive.


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Proper way to power down a FDM printer
I just got my first 3D printer today, QIDI X-ONE[2], and so far so good with the setup and getting my 1st print. I wanted to power off the printer, but I don't see any instructions on how to properly power off the machine.
Does anyone know how long I should wait, or what the minimum temperature would be safe to power down the machine?

[TL:DR] - If you can comfortably hold the nozzle with your fingers, you are good to go

In order to understand how long one should wait, it is important to understand why one has to wait.
All modern consumer-grade FDM printers have their printing head made of two assemblies: the cold end, where the extruder stepper motor is located and the filament must be in solid state, and the hot end, where the filament is actually melted and pushed through the nozzle.
Between the two there is a thin-walled length of pipe called heat break, whose purpose is to keep the two separate and make difficult for heat to reach the cold end by conduction.
However, the heat break is not "watertight", and heat also transmits via the convecting motion of air and IR radiation, so the cold end is actively cooled (most commonly with a fan).
The reason you want to wait before switching off the printer is that you want to keep that fan spinning until there is no chance for the heat to creep up and melt the filament in the cold end.
If the filament were to melt in the cold end, the extruder would clog and you would probably need to disassemble it.
In order to make sure the cooling happens, you have to make sure that your G-code tells the printer to stop heating the nozzle, after the print is done.
All slicers that I know of have a specific configuration setting called "end G-code" or something similar where you can manually insert the code you want to execute at the end of each print.  The part relevant to your question could look like this:
M104 S0 ; turn off heating block

If you want to get fancy and your hardware has a beeper you may also try:
M109 S60 ; wait for nozzle temp to drop to 60 °C
M300 S300 P1000 ; make a beep sound

Typically "end G-code" has other stuff too (move the head out of the way, switch off the heated bed, disable the idle hold of the steppers...)
Just make sure to move the nozzle away from the printer as your first action: you don't want the hot nozzle to linger idle above the print and ruin its top layer!

Wow @mac thanks a lot! Now I'm wondering if  that "M104 S0" code is a default setting or not. I finally printed my own design, but I knew nothing about these parameters.

@1QuickQuestion Somewhere there's likely a file with *.gcode extension. You can open this file in any text editor and look at the very bottom to see what codes where included.

According to the M109 G-code the documentation, the printer will wait to reach temperature given with S only when heating. With R, the printer will wait also when cooling down.
So if the answer of mac fails to work, try:
M109 R60 ; wait for nozzle temp to drop to 60 °C

Welcome to 3DPrinting! Good catch!


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What is the power consumption of the heatbed and hotend?
What is the power consumption of your heatbed (size) and hotend (model)?
I want to verify that it is possible to use a battery to power them.

At the very least, identify your printer, your intended bed temperature, extruder temperature, and length of print time.  A big enough battery can power an entire town; a small one can't keep a LED lit.

With a sufficiently large battery you can power anything! :)

I have printed using a massive car battery when my original PSU blew. I wanted to print so bad so I just connected it and went with it. It worked fine but do keep a charger on it because it drains rather quickly.

I have a Kill-A-Watt meter so I got a pretty good measurement for you with my Anet A6. Like Petar said each model is different but this should give you a idea. When heating both the nozzle and heat bed the printer consumes 160 W of power, once to temp it backs down to 9 W (it also uses 9 W when just "sitting doing nothing and is on"). When the nozzle and bed get down in temp it hits back up to 160 W. Basically it is never a consistent heating, it is on and off. Like a refrigerator.
When it comes to heating only the nozzle the printer uses 60 W (so 51 W is going to the nozzle for heating).
When it comes to heating only the bed the printer uses 142 W (133 W to the bed).
This is interesting because it would make sense the printer needs more than 160 W when 51 W is going for the nozzle and 142 W going to the bed, that makes 193 W. I make mention of this because that may suggest my power supply is not big enough and the printer could really use around 200 W.
As a little bonus when the printer is moving around (stepper motors are active) I find it using 35-40 W (or 26-31 W) to power the steppers.
So with all the said, is it possible to use a battery? Yes, you could. And to give a example a car battery should have 80 Amp-hours (or something like that, but we will go with it). With that battery you can get 960 Wh (Watt-hours) from the battery before it dies. Going with my printer using 160 W I will get 6 hours of printing time. But keep in mind as the battery is used the voltage will drop, so in the end the printer will be getting something like 10 V which I am sure will affect heating and overall performance.
Last thing I feel that needs to be said. If using a inverter to convert the 12 V battery to 110 V (or whatever voltage you use) a cheap one will not be healthy for the printer. Cheap inverters put out square waves instead of sines waves. Basically it will hurt the printer. You can learn more at this WEBSITE
"Update" on March 4
I read a comment that mentioned running right off the battery without a battery and then I thought of something that I did not think of before. And that would be protecting the battery itself
So I said you can run the printer off the battery. There was one issue that I had not thought of. And that was the voltage drop and the battery discharged. A battery usually does not have voltage-cut off to keep the battery from being overly discharged, and a printer does not have anything to measure voltage (why should it). So a simple hook up of a 3D printer to a battery is prone to drain the battery much lower than 10 V, which will greatly shorten a battery life-span. This can be prevented two ways.
A circuit between battery and 3D printer. There is plenty of circuits that can be bought as long as they cut power to printer at 10 V or something (for lead acid anyway) and can handle the amperage draw.
An inverter can also be used because this voltage cut off is already in them. But remember that square waves are bad for the printer.

At least for Cura output and my kit's firmware, the bed and the hotend are never both in the "full heating" mode.  This limits the max current draw for teh system as a whole, which I see as a good thing.

@CarlWitthoft I use Craftware and it does heat the bed and nozzle at the same time (but can be disabled). I have noticed it simply takes longer when doing both. But once one is done, being the nozzle or bed, it focuses all the power to the other component that needs to heat. And I do agree that it is good to limit the max draw to the printer, I will should disable the heat simultaneously option.

I really want to take a printer out to my off-the-grid shed and see if I can sustain it. If I assume a 50% duty cycle of heat on/off, that'd be about 8-10 amps/hour. Hmmm. (no inverter necessary)

@tedder42 You are correct with 8-10 amps per hour. And I recommended a inverted because the printer does not know when to cut off, so the battery voltage will go well below what is recommended, which is around 10v or something. A inverted does have a voltage cut off and will stop the printer from 'wrecking' or shorting the life span of the battery.  But because the person was asking if he could run it off a battery that is why I answer "yes". I should has put more detail about why a inverter is recommended, which I may do yet.

thanks. Seems it'd be a lot more efficient to do a low voltage switch/sag protector than to invert. Depends on the circumstance, though.

@tedder42 It would be. But I honestly didn't put time into thinking of the best way to protect the battery. It will be interesting how it goes running the printer off-grid.

Note that "watt" is a measure of "energy per second" and "amp" is a measure of "charge per second". Saying "amps/hour" makes no sense, because "amp", in and of itself, already contains the notion of "per time unit". The printer simply draws 8-10 Amps (not "per hour" or anything like that). Battery capacity is measured in Amp-hours (an 80 Amp-hour battery can supply 80A for 1 hour, or 40A for 2, or 1260A for 30 minutes), and the total amount of energy a battery can deliver is measured in Watt-hours.

@TomvanderZanden Thank you for the correction, I should have been thinking about that when I was adding but that slipped through my mind. But it is a really good thing you noticed :)

To answer the underlying (X-Y) question, yes it is possible to power a small 3D printer from a battery pack. This Article describes a printer built by Naomi Wu, mounted on a frame to carry around whilst printing, as a 'novel' style of sponsored video. The printer here is a BIQU Delta printer, and the power supply is 2x 3Ah batteries (guessing this is @12V, but it's not clear). Presumably there is no heated bed, but still the run-time will be quite limited.
The important part for working out battery life is the duty cycle of the hot-end, not the load required to get it up to temperature. This probably comes to something like 15-30 watts on average, provided you can live without a heated bed.
Of course, if you have 10-15v batteries, the printer will probably run off these directly, no need to waste energy converting up to 110/220V and back again.


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Under-extrusion in vase mode
So I found a vase on thingiverse and I wanted to print it, so obviously I did. I used craft ware to slice the model using there 'vase mode', and sent the Gcode to my Anet A6 printer. In the end I found weird underextrusion (I think that is what happened) at the starting points that seem to have appeared. I don't know what to think of this and I don't know what happened or how to fix it.

Your question is rather like the " My car doesn't work. Fix it" command to a repair shop.     We're not mind readers:  tell us your printer model, the software you're using to slice,    Try also to edit your post so it's in temporal order. As it stands it's impossible to tell what worked and what didn't.

@CarlWitthoft I changed it, sorry for not making sense, hopefully it is better now! Thank you for pointing that out

This sort of failure is best diagnosed by observing the failure. It probably isn't underextrusion, there is no reason to get variation in extrusion just along one edge.
Did you really get a proper vase-mode? You can check in your slicer, or with gcode.ws and make sure that each layer only occupies a fraction of the part, with many small steps (rather than one step after printing a slice of the whole part)
It seems the failure is close to a sharp transition in the wall. Have you got enough cooling, or a low enough extrusion temperature? It could be that the plastic viscosity and surface tension are conspiring against the shape. Printing slower might possibly help too (both on the failure, and to allow the part to cool between layers).
Finally, you might have a mechanical problem which is interfering with the print just at this point, and that might include the extruder binding in some way. This could be hard to spot during the print, so check over all the moving parts, and all the fixings.


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Heat block design without cartridge heater
Is it possible to design a heat block without cartridge heater?
My idea is to build a very small heat block to increase/decrease the heat as fast as possible. The resistance of the heat block will be used. The current to this block is 500mA and is set constant with a circuit. The voltage will be set with pwm. Is this possible with 500mA and 5V (2,5W)?

By the tone of your comments to the replies given insofar, is unclear what you are after: if the question is merely "is it possible to heat a piece of metal by passing current through it?" then the answer is "yes" (duh!). If the question is: "is it a design that makes sense on a FDM printer?" then the answer is "no". Yours seems like a bad solution looking for a non-existent problem. If this is not the case, please provide more context on why you would need a heat block that warms and cools faster. :)

I want to make a usb powered printer. The power of usb is not much because of this i want it very small. I want only use 500mA and 5V for the heatblock. This is for me a existent problem. To heat a piece of metal fast enough to a given temperature with less power. Is this enough information?

I think a question on the lines of "Is it possible to use USB as a power source for the hot-end" could have been a better one than the one you asked, then. :)   Anyway: I think you should go in the opposite direction than the one you chose: what you are after with a low-power source is an extremely well insulated hot-end with enough mass to hold the temperature ~steady when the extrusion speed spikes (as for example during infill).  Up to a point, you can also compensate the limitations of such a low-power source by reducing drastically the print speed.

The current to this block is 500mA and is set constant with a circuit. The voltage will be set with pwm. Is this possible with 500mA and 5V (2,5W)?

This means that the resistance of the heat block would have to be, by Ohm's law, 10 Ohms. You can't set voltage and current independently of each other, which it sounds like you're attempting to do.
2.5W is also rather low power, considering typical heating elements are 25W or even 40W. ABS plastic has a specific heat of ~1300 J/(kg K). Typical printing speeds are 20 grams/hour, so if you have to heat up the filament by 200 degrees C, you need a minimum of 1.44W. 2.5W leaves awfully little room (~1W) for losses due to convection or radiation.

The resistance is not important. The circuit (current source) will set the current to 500mA and the voltage is set with pwm to change the power. What do you think is it possible?

@user8886193 Unless I am misunderstanding your proposal, that is not how electricity works. You can't "fool" Ohm's law by combining a constant current source with PWM.

Fow example line Regulation (Variable Line Voltage) and before that a pwm and capacitor.

I'm afraid the idea itself is questionable. :)
Part of the reason for having a heat block in the first place is to leverage the volumetric heat capacity of the block to maintain the temperature constant even thought the extrusion speed (and thus the rate at which energy is used to make plastic warm and change state) is not.
A smaller block would probably:

require a lot more power to operate in order to compensate for the missing thermal inertia (most PSUs are already "stretched" when it comes to power requirements)
cause the temperature to fluctuate, with negative effects on the print quality

A second problem I see is that you would most probably electrify the whole printer:

creating a hazard
affecting the ground level and thus - potentially - the proper functioning of all electronics

There will be no connection (metal to metal). The heat block will have no connection. I will use a part in between to protect against voltage and heat. I think i will not need somethink to cool.

2.5W of electrical energy defines the heating rate for a specific mass (and thermal capacity of the material).  It also determines the highest attainable temperature for a specific emissivity (clue, it won't get hot).
Any switching circuit to match the resistance of a block of metal to a 2.5W power source is a switch mode power supply in disguise. Yes, you can generate 150mV at 16A, but you need very thick wires to avoid loosing most of your generated power in the circuit.

If i transform the given 5V and 500mA to 150mV at 16A is the current the cause for the heat? Then it will be possible to just increase the current and set the voltage down to set the speed of heat generation and the opposite way.

no. it doesn't work how you want it to.

Did you calculate it? My idea was to make the heatblock as small as possible (Alumimium) to save power because of less power and to indrease the temp as fast as possible.

@user8886193 An aluminium heat block will not have enough electrical resistance to make a practical heater. You can't control voltage and current independently - it's all determined by the resistance of the heat block and Ohm's Law. It simply will not work. If the heat block has the same resistance as the wires connecting it to the power supply, then those wires will heat up just as much as the heat block itself no matter what voltage and current you use. The resistance of the heater needs to be (much) higher than that of the wires.


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STL to STP CAD Conversion
Does anyone know of a good way to convert a 3D print file, like STL, to STEP - a useable file format for plastic injection molding companies?
I have tried to convert the files through a couple of programs without success. The most requested file is a STP or STEP file.  If there’s no easy way to convert it, which I don’t think there is, does anyone know someone good at re-creating CAD files?

a good way to convert a 3D print file like STL to STEP a useable file format for plastic injection molding companies

I don't know much about plastic injection molding companies, but I do manipulate a lot STEP, STL files and I do know that it is possible to achieve "a good way to convert […] STL to STEP file format […]". For the record, the manufacturing process isn't recorded within these files format (at least not yet) so you don't have to specify the final use.
However, this is a delicate process which isn't easy for beginners in CAD engineering.
As said before, the STL files is a tessellation of a surface with triangles, while STEP defines precisely the surface with curves. It's basically the difference between raster graphics and vector graphics: most fully automatic reconversions programs (such as Inkscape in case of images), would create something quite approximate to the real shape. Manual programs would require time and knowledge of the needed tools (Inkscape can do it too, in case of images).
For the record, asking for a STEP file to be a STL file is as easy as transforming a vector graphic to a raster graphic, it's a one-click transformation. What you are asking, the reversed, is complicated.
What will be done if you import a STL file to a standard CAD program, it will consider each triangle as a defined unique surface, and in most cases, the standard CAD program will have a lot of difficulties to handle the STL. It could then export it to a STEP file, but this will make a huge, incredibly heavy file difficult to handle (I've seen STEP files over 300 MB while the STL was less than 10 MB).
The good way to do so, is to go through a reverse engineering program that handles better these troubles. I don't know any being free, and they all require extensive experience, expansive licenses and a bunch of time generally. For instance, I know that Catia, SpaceClaim or 3-Matic are programs that work very well for your issue, but they are both very far from affordable or easy to handle if you aren't a CAD designer.
Another bad way would be to pass through a 100% automatic reconstruction/conversion to STEP, but it would make something not exactly accurate to the original part, and may not be of any use depending of your application.
My best advice for this would be to find someone or some enterprise that can practice the good way from your STL to have the STEP file you want. You should also very much specify for what use your file is, because as a design engineer I wouldn't generate the same STEP file depending of the use of each surface.
I hope this answer isn't too much a disappointment for you, I know it won't solve your problem but it can help you understand why it is such a hard problem.

I've been able to manipulate an STL file using the hobbyist version (free) of Fusion 360. There's a series of steps involved that may require some research and experimentation, at least it did in my case.
One loads the STL file into Fusion 360 by using Insert, Mesh.
Once loaded, turn off history.
The next step is to convert the mesh file to BREP.
In that form, the surfaces can be edited and the model can be modified if necessary.
I have not exported to STEP, but have confirmed that Fusion 360 supports STEP as a valid export file format.
Both links provide additional information that may be of value to your project.
Consider also to double check your STL file to ensure it is manifold. Meshmixer is useful for such purposes. One model imported into Fusion 360 had entire faces removed due to a manifold error in the original model.

The fact you may be able to produce a STP file is no guarantee the company will be able to injection mold it.
You should ask the intended recipient of the file what are the actual requirements they need for making the injection mold.
STEP and STL are not two different ways to store the same information.  They are two different standards with different goals.  Both can describe the geometry of a solid shape, but STEP has plenty more of functionality designed to store information about the manufacturing process of the part.
For example, while most CAD software deals with the STEP substandard AP 203 "configuration controlled 3D design" it may be that the company you are trying to work with requires information about the injection molding process itself, that would probably be regulated by the AP 223 part of the standard ("exchange of design and manufacturing product information for cast parts").
If that is the case, I strongly doubt any CAD software will be able to automagically create that information out of thin air.
With an analogy: it is like you were dealing with a TXT file and the publishing company asked for a DOCX one.  You may easily save the TXT as a DOCX, but what the publisher is really after is a document with a hierarchy of titles, font information, formatting, etc... and just saving the TXT as DOCX won't automatically generate those.

It depends very much on the molding company, and how much engineering service you can afford to buy from them.
Some will remodel your entire part anyway, to make it suitable for molding. Others will only accept specific formats and parts that are engineered 100 % ready to be molded.
So talk to them first, if they only use your file as a template, it won't matter what format it is in.
To answer the question:
I believe FreeCad can load STL, and export STP but, like Mac said, it may not be the result you need.
STL = Surface Tessellation Language. This stores the geometry as approximated by a mesh of triangles. It is incapable of perfect curves, so there is some information lost when the model was exported to STL.
STP or STEP can represent surfaces correctly, but only if that information is present in the model. Put in a tessellated model and it will still be tessellated.

I found a website, CadMesh, to convert the file for me. So far they are a free platform. I recommend to give it a shot.
Doing some research on internet I also found this good tutorial:
Bantam Tools Blog - Convert STL to STEP
But the FreeCAD software seems to have some limitation on handling complex shapes. It may work for you.

Step 1: Download a Conversion Tool
Our conversion tool of choice is FreeCAD because it’s free, relatively
simple to use, and does a good job of converting STL files to usable
solid models. Download it here.
Step 2: Import Your STL File

Open FreeCAD.
Create a new file (File menu > New).
Import your STL file (File menu > Import > select your STL file).
From the dropdown menu in the top toolbar, choose Mesh design (see screenshot).

(Credit: OpenSCAD Chess by Tim Edwards)
Step 3: Repair the Mesh

Open the Evaluate & Repair mesh tool (Meshes menu > Analyze > Evaluate & Repair mesh).
Select the mesh from the dropdown at the top of the Evaluate & Repair pane.
One by one, go down the list, clicking Analyze and then Repair if the analysis finds any problems.
If clicking the Repair button for "Folds on Surface" makes your mesh look terrible, you can skip that one.
If clicking the Repair button for any other option makes your mesh look terrible, you’re likely out of luck. However, you should
still try the next steps in case you get lucky.

Step 4: Convert Your Mesh to a Shape

From the toolbar dropdown menu, choose Part.
Select your mesh in the left pane.
From the Part menu, choose "Convert to shape."
Leave the Sewing Tolerance at 0.10 and click OK.

Step 5: Convert the Shape to a Solid
This is the moment of truth! If FreeCAD is able to convert the shape
to a solid, you’ll be able to save it as a STEP file. If you get a red
error message in the bottom left corner of the screen, you’re out of
luck.

Select the newly created shape.
From the Part menu, choose "Convert to solid."
If it works, you’ll see a new item in the list in the left pane that ends in "(Solid)."

Step 6: Export Your Solid to a STEP File

Select your newly created solid file in the left pane.
From the File menu, choose Export.
From the Export dialog, choose "STEP with colors (*.step *.stp)".
Save your file.

You're done!

Welcome to the stack.

Please refrain from link-only answers, they might not work tomorrow or in the future due to link rot. explain what is in the links.

I have updated your answer for you, with the relevant info from the link. Next time please include the information yourself. As has been stated already, links tend to die and when they do, your answer would not be much use. Thanks.

Converting mesh files to solid formats is a complex task.
While converting files from mesh to solid you should look for accuracy, number of patches, nurbs pattern, file size and many other variables that should be taken in consideration based on the use you will give for the solid file.
I have compiled some thoughts as a starting point for your research. Make sure your STL/OBJ/PLY (mesh) file has a decent quality. You can use free software to validate your file such as Meshmixer and MeshLab.
You will CONSIDERABLY increase your chances by having a watertight model. If the model does not have a closed mesh, you will most likely have a hard time/fail converting it.
There are 4 ways to do it:
1 – Using a free software
This is a valid solution for a simple shape models.
The best tutorials are posted here on GrabCAD.
Here are some tutorials available on internet:
https://grabcad.com/tutorials/how-do-i-convert-stl-graphics-to-a-solid-model
Convert STL (or OBJ) Mesh to SOLIDWORKS Model (NURBS)
How to convert STL to STEP using FreeCAD
https://blog.bantamtools.com/convert-stl-to-step
2 - Professional software solution
This is probably the best solution for companies with a high conversion volume on CAD/CAM demand.
Some of these companies offer a free software version for students.
The best solutions I have found:
- 3D Systems Geomagic Wrap
- Fusion 360
- Power Surfacing (SolidWorks plugin)
- TransMagic
3 - Hiring a professional freelancer
This is the best option for a one-time project, higher chance to get a decent converted file for an affordable price. Try to look for the feedback/customer review before hiring someone.
I have seen professionals charging as cheap as US$25 per model/conversion.
You can check on these options (there are many others):
https://www.upwork.com
https://www.fiverr.com
https://www.freelancer.com
4 - Online conversion platform
There are solutions with instant delivery/conversion, and others that take some hours to send you the file. I found solutions varying from free online conversion to pricy service.
There are prices as low as US$1 per model/conversion.
You may need to do some touch up on the files converted from automated platform before you send it to a CNC or other CAD/CAM machine.
You can check on these platforms:
http://cadmesh.com
https://www.convertcadfiles.com/
Have in mind that, the higher is the model complexity (shape) the harder is to convert the model.
If trying to convert a 3D scanned model, make sure to have a closed mesh and a high-density mesh definition.
During your Google research, you can also use the term “model surfacing”.
Good luck!


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Square and parallel infill patterns
I don't know how to word this right now but I am going to try my best... moving on!
So I was playing with my slicing software (Craftware) and I was looking at two infill patterns, Square and Parallel. When looking at strength, print quality, and time does Square really benefit a whole lot over parallel? I ask because Parallel does not use near the filament and has less contact points on the model. I provided pictures of both to give a visual. Can I use parallel and still get super strong and good looking parts?

Parallel infill pattern

Square infill pattern
If I didn't include something or not making sense ask in the comments and I will answer/edit as needed. Thank you!

... does Square really benefit a whole lot over parallel?

That would depend by the definition of "a whole lot", of course! :)
Strength
Generally speaking, the variable you want to operate to tweak the overall sturdiness of your part is not the type of infill, but rather its density.  According to the literature I have access to, sturdiness grow fast until about 60 % infill, then the gains become progressively more marginal.
Different types of infill modify the way the part reacts to stresses.  The two you showcased, for example, are strongly anisotropic: a part with those infill will resist a lot more to stresses along the Z axis than along either the X or Y ones.
Also, relative to the squared infill pattern, my experience is that parts with a parallel infill pattern typically have a bit more give when squashed.
In case you wonder: cubic, cubic subdivision (and solid) infills are those regarded as offering the most equal resistance along all axis.
However, the way the infill will affect rigidity and sturdiness of a part is as much dependent from the type of filament and the shape of the part as much as from the infill settings, so - if you are after precise numbers - you should most definitely run some tests.
Time
That depends entirely from the part shape and size.
Typically, a printer will spend most of its time printing the shell. This is due both to the settings (you want to go slow on the shell to increase quality) and to physics, the shell typically requiring many more changes of direction (and thus accelerations and decelerations) than the infill.
So, even if the parallel infill requires about half the work of the squared one (50 % faster), in a small print with a sparse infill, the total time spent doing infill may be 10 %, thus the net gain would be only 5 % of the total printing time.
Quality
This is very printer-dependent. For me, when printing with two shells, I can't tell the difference on any infill. For the top layer, the quality is affected more by infill density than type (with the filament sagging slightly between walls if the infill is very sparse).

I was re-reading your answer and you said you read some of this information, is it a online page that you could share a link? I would be interested to read about other infills and stuff like that. Thanks!

@Ljk2000 - No, is this excellent concise book: https://books.google.ee/books/about/Functional_Design_for_3D_Printing_2nd_Ed.html?id=o43BsgEACAAJ&redir_esc=y&hl=et


text:
MOSFET as a safety feature
When going through printer reviews, I often see the presence of a MOSFET listed as an important safety feature.
I understand the MOSFET to be a transistor, but I haven't understood how it is used in the circuitry of a printer, and - above all - why it increases the overall operating safety of the printer (nor what the less safe option would be).

It would be good to include one or two examples for where you read about a "MOSFET in the PSU" being a safety feature.

@TomvanderZanden - I will try, but because a great deal of information I consume is via Youtube, it's not as easy as "find in page" for me to recover that information!  You put the emphasis in "in".  Can you clarify why?  Maybe I expressed myself poorly and we are misunderstanding each other?

@TomvanderZanden - I was able to retrieve this review on the CR-10 safety: https://youtu.be/6s_UJ9I0fQo shortly after the minute mark is when it mention the mofset, albeit it seems he's impying the mofset is between PSU and motherboard, in this case.

"in the PSU" means physically inside of the PSU - I thought this was a bit strange so that's why I put the emphasis there.

In the world of (cheap) printers, "MOSFET" has taken on a meaning of its own.
For a long time, 3D printers have had MOSFETs on board of their motherboards to switch the heated bed. In the past two years or so, we've seen a surge of (mainly) Chinese printers where the on-board MOSFETs (or, more often, the terminal blocks) weren't rated for the high current for the heated bed and would melt down or catch fire.
People then started recommending fixes to these issues, such as using a relay, soldering wires directly to the board (to bypass the terminal blocks) or using an external (better) MOSFET. Eventually, manufacturers caught on and started offering "MOSFET boards" which basically consist of a high-power MOSFET, high-current rated terminal blocks and (often) an optocoupler to isolate the drive signal from the bed power (but this doesn't really do anything; there's no need for this isolation). These boards are meant to be used to switch the high current to the bed directly, without it passing through the main board (and instead, the bed output of the main board is used as a control signal for the MOSFET board).
People often refer to these pre-made "MOSFET boards" simply as "MOSFETs" but there is more to them than just a single transistor.

why it increases the overall operating safety of the printer

Using an external MOSFET board does not increase the safety of the printer at all, unless the main board of the printer is badly designed. There's no reason the MOSFET needs to be external and can't be integrated on the main board. Essentially, any company that is offering a printer "with a MOSFET (board)" is saying that their main board is poorly designed and that they've included a band-aid fix. Or, perhaps, because installing an external MOSFET is such a common "mod" nowadays, they're advertising an external MOSFET because it is what people want to see (even if the main board might have a perfectly capable MOSFET already...).

Thank you Tom, very helpful.  The only thing that is unclear to me in your answer is what an "optical isolation circuitry" is.  I also removed the "it the PSU" bit from my original question, so not to make the question to others.


text:
How to increase bed temperature over 103 degrees
I am having problems with my tevo tarantula large bed 12Volt power supply, I am getting the thermal protection message when heating my bed with target temperature set to 115 degrees.
The process slows down after reaching 90.
I changed merlin settings to trigger thermal shutdown after 5minutes/2degrees and added a cover to the printer, so getting now 103 degrees (usually shutdown was at 100/101).
link to a video showing panel: https://photos.app.goo.gl/jiW9NE7wEB4H0mOy1

I'm unable to parse your question. Where do 115 and 300 affect your ability to heat above 100?

question rephrased thanks for comment @SeanHoulihane

You need to increase the power of the heated bed. With a given amount of power, there is an upper limit to the maximum temperature you can reach because at a given point losses due to conduction, convection and radiation will balance out the heating power and the temperature will not increase any more.
Sometimes, inability of the bed to heat up is due to the supply voltage sagging under load. First, measure the supply voltage with and without the bed turned on. If you find the supply drops significantly when the bed is turned on, you need a new power supply.
Otherwise, you will need to either:

Get a new, higher-power heated bed. Make sure that it is compatible with your electronics, or upgrade them as needed.
Increase the supply voltage so that the bed you already have will give more power. Some power supplies have a small adjustment potentiometer that lets you adjust the output voltage. Be careful when doing this. Even a small change in voltage gives a big increase in power. For a heated bed with resistance R at voltage U, the power dissipation is U2/R. Going from 12V to 13.5V already gives 26% more power.

will check above and give a ticket to TEVO as per specification the set shall go to 110 degrees.

As the voltage drop with bed heater enabled was low, then decided to raise the voltage on the PSU and that did the job. Thank you.

Some simple steps that may help to reach higher temperature:

Check if you can use heated bed insulation of any kind - the most common approach is to use cork sheet
Protect heated bed and printer from any possible air movements - arrange a set of walls around printer or just simply put it in the cardboard box large enough
Cover heated bed with cloth or cork sheet until it reaches desired temperature
Replace wires from heated bed to the power supply with thicker ones (2.mm2 / AWG14 should be fine)


text:
What's a good way to secure bushings in a 3D printed part?
I'd like to secure bushings in 3D printed parts. They would be used for a drilling jig. I've seen heat-set inserts, but they've all had threaded interiors. The best idea I can come up with is printing the plastic hole several thousandths of an inch larger than the bushing and applying a lot of epoxy to the OD of the bearing and inserting it. Is there a better way?
As an aside, I had a hard time finding proper tags.

If the outside of the bushing will bond well to the epoxy, your method is simple and likely to be effective.
You could use the same method used for threaded inserts by roughing the exterior of the bushing, heating it and forcing it into a correctly sized hole printed in the model.
The threaded inserts are knurled or otherwise textured to provide stronger bond with the melted plastic. Knurling your bushing is more complex than a good epoxy bond.
I've discovered a product called "castable bushings" which would appear to meet the above requirements for heated inserts:

The product listing indicates that these are used for drilling jigs.
It might be less messy but more expensive to purchase and use these as opposed to epoxy and a bit of sanding.


text:
Z axis Control of Prusa i3
I have modified my Prusa i3 MK2 printer so that the existing extruder motor has now been attached to a 5mm lead screw with a 1mm pitch. What is the easiest way to control the extruding of the printer now.
For example is it possible to change the settings in slic3er at all for the extruder? or would I have to download and edit the marlin firmware?

Do you mean 'Z' azis, or extruder, which would be E? It doesn't affect the answer, but makes your question look weird.

@marc-mckee both cases needs to edit your firmware to keep the right parameters, For Extruder to feed the exactly amount of filament, And for Z axis to get the correct height if is this the case you will have printings with a 1/3 of normal height or less.

@FernandoBaltazar You do NOT need to edit the firmware. M92, G500.

Sorry i mean the extruder motor (E), i have used Pusa's online calculator and it has suggest this G code: "M92 Z3200.00" but i'm not sure where this needs to be added to?

@MarcMcKee Sean is right, just connect your printer to a Gcode sender in your PC and type M92 Z3200.00 to enter the new values.

The firmware of the printer reads the g-code, in this instance, for z-axis movement. The g-code provides only (primarily) millimeters of movement and direction, along with speed.
The firmware reads those figures, figuratively speaking, and knows from the values stored in the firmware, how many steps to rotate the motor, in what direction and at what rate.
I suppose if you were a glutton for punishment, you could write some code to convert the existing measurements to ones that are adjusted for the new screw, but that's just crazy. Imagine that your new screw provides for 3.729 times the movement that the old screw did per unit of rotation. You'd have to find all the z-movements in the code and apply that factor to those numbers. I suspect rounding errors might make for a less-than-satisfactory print.
As you've mentioned in your question about editing the firmware, one may expect that you have an idea what is involved. If not, that may be the topic of another post.

You can set the 'steps per mm' for the extruder (and the other axes) by sending GCODE to the printer, and store this in the internal memory. Re-flashing the firmware only affects the 'factory reset' configuration of the printer parameters.
To see how to calibrate your extruder, you're probably best looking for videos since although the process is just a few GCODE commands, the whole process is not easy to understand.


text:
Heated bed for the XYZprinting da Vinci mini w
Anybody ever tried to retrofit a heatbed to the da Vinci mini w with the proper dimensions (165 mm x 165 mm or 6.5" x 6.5").
Where can I find a heatbed that fits and a corresponding power supply / PID controller?

Is there a specific reason you are looking for a heated bed?  Are you having print adhesion or curling issues; or, are you wanting to try a different material that requires a heated bed?

I've severe warping and therefore adhesion issues too, even with PLA. Of course, I am also interested in printing other materials, if the manufacturer finally provides them or if I decide to replace the controller board (so I can print unchiped material).

Instead of replacing the bed, you could invest in a silicone heating element and top it off with a piece of (Borosilicate) glass.

If the printer board has exposed headers to attach a heated bed, which is possible, but not certain, you could use an SSR (solid state relay) to power the bed using the signal from the board to set the temperature. Alternatively use a thermostat for an incubator to create the signal for the SSR. Note that all these parts can be sourced from those typical online websites.
In case the wires of the silicone heater stick out, use a layer of cork where you cut out space for the cables and thermistor.

I mounted four 10 W resistors under the bed and connected them in parallel to the SKR1.4 board, I installed in the mini.
If you still have the original board, you can connect the resistors to any power source with enough power to drive the load, preferably 24 V.

I decided to go the way of a silicon heat pad (12V/24V) 200 W.  I got the unit and a 3 mm glass bed. Clipped it to the aluminum, and promptly the head crashed into the side of the bed!
Lesson learned. The Mini in order to go home transitions to a spot at the front of the bed and actually lower than the bed.  This is so that you can level the bed manually by adjusting 4 screws on the gantry. The gantry sits on the bed thus leveling it to the bed.  Because of this, there is only about 4 mm of height available.
One individual who added a heated placed a riser under the z-axis to overcome this limitation. My other thought is to replace the aluminum bed with a glass bed and have the heater on either side of the bottom gantry as there is about 2 mm space there. Since there is an end stop the unit is using others have simply moved this up to match the new height of the bed.
I am assuming [HOW TO] Da Vinci Mini Heatbed Conversion would have attempted a software patch before doing a physical riser.  While in some ways I would feel better raising the riser, I decided to extend the tab on the extruder head to intercept the sensor instead.


text:
Flat heated bed replacement for uneven bed
So the heated bed I got with my anet a8 is not entirely even. The middle of the bed is lower than the outer edges of the bed, which always causes issues with the first layer, especially with a larger print.
I know I could do mesh bed leveling but I don't want to have to do that every time before I print.
So my question is, where do I find a heated bed that I can be sure of will be even and not have dents anywhere?

If your bed is aluminium, it should be rather easy to reduce the dipping by bending the bed the other way around (after having removed it from the carriage). Try to apply pressure with the palms of your hands (as to spread the force on a larger surface) and use a ruler to verify the effect after every push. I did not manage to completely flatten my bed, but I manage to get rid of all adhesion issues at least.

Several things to consider:

Nothing is perfectly flat.  It is flat within a tolerance.  The bed you have now is flat to within a tolerance.  If you want a flatter bed, you are going to have to specify how flat.
As @mac mentioned, aluminum is bendable; so, what once was flat can be made un-flat and the other way around.  Note: Your problem may not be your bed, it may be that the bed mounting frame has introduced stress that is bending the bed.
Because the heating element is applied to one side of the bed, the differential heating (between the top and the bottom) can cause the bed to bend at temperature; so, flatness could vary with temperature.

What to purchase:

The Anet A8 has a 220x220 bed.  A very popular size.  You can get replacements heated beds for as little as $20 from a lot of sources.
Because of the considerations above, rather than replacing the bed, you may want to consider attaching a 220mm x 220mm Borosilicate Glass Plate to the top of the bed.  These are also readily available (even from Amazon) for less than $20.  That is what I did.  The glass makes for a very flat surface and a great printing surface.  I attach mine with small binder clips.  That makes it easy to remove to take the print off or to clean when needed.

How do you keep the glass from deforming if the high point of the Al bed is anywhere near the center?  Put another way, have you ever seen the glass "hold off" from the metal bed at the binder clips, leaving a gap at the edges?

I personally haven't heard of a problem with the glass bending; but if the middle is high, that needs to be considered.  In the specific issue the OP described, the middle was low.