1 of Z step motors looseing steps?

Hi. I have a prusa I3. Everything seems to be working ok, but yesterday I print a tall piece (185mm tall, like a tower). Actually the piece is even taller, 30cms tall, so I split the piece in 2 for gluing them later.
At them moment of joining both pice they didnt match... Looking for the problem, the tallest piece, the 185mm tall piece, seemed to be like "twisted" : one side of the piece was taller than the other side, like about 0.9 mm of difference.
I have been looking for the problem, I couldnt find anything but this: it appears than the Z axis step motors don move the same steps? I mean: measureing the extremes X rod bars distance in eacho side to the ground there is a difference. So I leveled , useing a digital caliper. After a long tall print, the difference appears again.

So my guess is that 1 of the step motors is looseing steps. And this can couse a tall piece to have this difference of size?

Is this normal or shuld I adjust may be the pololu power to the step motors? I have been trying to "listen" when the Z axis moves but I cant hears them looseing steps.

The config I have for Z movements is: 2mm/s speed (for printing and homeing) and 100 mm/s acceleration.

Thanks innadvance for the help you can provide me

Chances are you have your Z motors connected in parallel and they are not getting enough current. Most motors used in 3D printers are much better connected in series instead.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks for the help. I googled it. I really dont know if they are in series or parallel... Anyway, I looked infor how to set it up in seris: I found this:

[www.instructables.com]

The problem is that I really dont know much about electronics...

If they are in paralel and they are lack of power, can I solve it by increasing a little power from the pololu?
I will see if I can find somebody who can tell me if they are now in parallel or series and if so if they can do the work of changeing them .

So for the moment , can I increase the pololu output a little?

Quote
Tinchus
If they are in paralel and they are lack of power, can I solve it by increasing a little power from the pololu?

You can try, but you risk overheating the driver.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I recently had this problem... My power supply died a few days after it happened. I can only assume their was a lack of power from the slowly dying PSU. Replaced the PSU and hey! its fine now. The heavier side of my x axis is the motor which skipped the steps, sometimes it would skip by as much as 2mm.

I'm soon going to switch to a single motor Z axis (upgrade has been in the works for far too long) using a strong nema 17 motor. So no need for re-wiring electronics, no misaligned axis from skipped steps, and no chance of lop sided / failed prints.