Why does my X/Y axis occasionally loose there positions ?

Hello

I have no idea where to even start with this. It's not the first time this happens to me, the printer will get part way through a print and its almost as if the origin shifts and the layers become offset from the base. Generally both the X and Y will be affected at the same time.

See picture

[postimage.org]

Edited 1 time(s). Last edit at 01/19/2013 02:34PM by flying freak.

a few different possibilities.

Your stepper drivers might be overheating. Your pulleys could be slipping on your stepper motor shafts.

Check your stepper driver voltages: you usually want a reference voltage of around 0.4v (the cheap Chinese versions use a Vref of 0.1).

Hello.

Dont think my pulley are slipping as iv made a line that transfers from the shaft to the pulley and it still lined up (like a scribe mark).
The motors are cool to the touch. Is it possible that the internals are over heating while the outside is at room temperature?


How does one check stepper driver voltage?

If you are sure your pulleys aren't slipping, and your motors are cool as you say, chances are your pots are adjusted too low, resulting in skipped steps. You can turn them up a little most likely.

See how to check and adjust your pots here

I agree. Try bumping up your reference voltage a tiny bit.

What electronics are you using?

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There's a bit of an art to this. If your pots are set low and you're trying to drive the printer fast in software, the motors will skip steps trying to reach that speed, in which case you can turn up the pots, or turn down the speed. But if you turn the voltage up too high, the drivers may overheat and briefly shut off, resulting in the same thing--skipped steps. Also, higher voltages will make the motors hotter, and a really really hot motor can cause a PLA motor mount or bracket to warp.

Ideally, you'd have your pots turned up reasonably high with a fan blowing on them, good quality high-torque motors that don't need full voltage to run at a reasonable speed, and ABS motor mounts for extra safety. It also helps if you have pulleys with a smaller number of teeth, since that increases the effective torque that your motors are able to achieve at any given voltage level.

what king of loading mechanism do you have for feedstock? this plays an issue as well, because of feedstock is not restricted in its motion when loading thru the extruder, at some point it will be a point of strain on the x axis.


do you have gears that are bolted to the shaft, and have a dab of lock tight? motion of gears moving free of the shaft happen a lot as well especially on y axis with weight of the table to move.

are you using proper current settings for motors to push them correctly. and in firmware is x-y jerk no higher than 15-20?

stepper driver voltage can be checked similar to these instructions. [reprap.org]

and do you have belt tensioners in place? these minimize backlash but also provide enough strain to ensure there is no slack around the gears and allow for a consistent grip to the belts.