Z axis movement problem

Hello all,

I just got a mendel, with gen6 electronics. Supposed to be plug and play but not even close to it!

After installing firmware to the electronics and managing to connect to it with the software, i was able to move the X and the Y axis.

The Z axis however has a problem. It seems that the motor cannot turn the pulleys. It's like the pulleys are too tight for the motor. I tried to remove the belt and run the motor to make sure it was spinning properly, that worked. But when I attach the belt back on, the lead screws budge a little bit, then the belt starts skipping. I removed the belt from the motor only and tried spinning and it was really hard.

It is almost like the lead screws don't want to turn. So i checked if they turn freely on their own, and that seems to be fine too.

Does anybody have any suggestions?

Thanks in advance.

Cu.

This sounds like a Botmill. Is it?

Did you try adjusting the trimpot on the Pololu for the z?

Botmill it is.

I don't know what the rest of your message means so I can confidently say no

I'll research and try doing as you suggested.

Cu

3d systems claim to have improved the quality of botmill according to their own post in this forum.

Your experience seem to contradict their claims. Have you tried contacting them for help?

let me put it this way; the machine that was to be plug and play came with missing firmware, the software USB flash drive was empty, the extruder motor does not turn, it just wiggles back and forth (could be the trimpot adjustment as you suggested, but I plugged it to the X, Y an Z ports on the electronics and had the same problem) the z axis gets stuck. So obviously no one did any calibration and/or quality control on this assembly. why would I expect anything better now?

anyway, i'm past that now. I'll try and troubleshoot and learn a few things on the way. Like what trimpots are and what they do. And thank you for that.

Cu

My mistake. Gen 6 doesn't use Pololu carriers for the stepper controller chips. The reprap wiki on Gen 6 should have the information you need. The stepper current adjustment is described here.

If you look at the picture of the board here, you will see a chips below each stepper motor connector. The trimpots to adjust the current are right below each one and the test pads next to them are labelled TP1-TP4. If you don't have a multimeter, you can mark the current location or take a picture, then turn the trimpot for the z fully counterclockwise (minumum) and the slowly turn it clockwise until the motor moves.

Edited 1 time(s). Last edit at 11/30/2011 07:03AM by brnrd.

Hi ,

I also have the botmill. And had to replace the vertical threaded-bars for Z-axis because they were bend
making a lot of noise when turning.

Then after replacing them I turned the potentiometer for the Z-axis by little increments to increase current.
Because I also had the problem of not moving/skipping.
Make sure the belt is not to TIGHT or you'll break the pulley on the stepper-motor after increasing the current. That's what happened to me.

Also try greasing the threaded/smooth bars along all axis with machine-oil.

I also recommend placing cooling fan's on the stepper-motors when increasing current cause they'll get pretty hot !

I'm designing a special bracket to place the fan's on top of the motors without getting in the way of the movement. When I'm done you can get it at thingiverse if you're interested.