Run out of ideas about motor skipping solutions. Request for more ideas...

Hi,

I'm having trouble with stepper motor skipping and have exhausted my list of 'what to do about it'. So, I'm looking for any ideas

I'm printing a long thin plate (100mm by 30mm - 5mm high) - if I print it long on x-axis then I get layer shift on every layer (x-axis shift only) . However, if I print it long on the y-axis it's perfect (i.e. no layer shift on x or y-axis). So, I believe my printer is skipping steps on the x-axis (only) when that axis is 'under load'. Printing small (e.g. 20mm square ish) objects works fine too.

I've tried
- turning the x-axis trim pot up and down (motor got hotter or cooler but but layer shift still occurred in both cases)
- adding fans to cool my GEN6 board (heat sinks now cooler throughout print but layer shift still occurs)
- adding fans to cool the x-axis motor and extruder motor (motors now cooler throughout print but layer shift still occurs)

(I also checked the x-axis belt pulley to check it wasn't slipping and causing backlash - though I believe I'd get layer shift when printing long on y -axis then too)

Any ideas what to try next?

Many Thanks

Pete

What type of x axis carriage do you have? It could be that as you get close to one side of your printer the x axis smooth rods go out of parallel and become harder for the motor to move the print head causing skipped steps.

Have you tried printing the object at different spots on the bed? Maybe you will see that as you move it far enough one way the motor doesn't skip any more.

Tell us more about the x axis framework too.

I don't know if you managed to solve the problem in the meantime, but I'm experiencing something similar and in my case I noticed that is related to the RAMPS, when it gets hotter, the X and Y axis start to skip steps. Only today I managed to realise that when I did few tests with 1 layer gcode, by replacing the hotend with a pen, and a piece of paper on the hotbed. And the results indicated that after a period when the motors were off, the steppers were working fine, the more I was continuing to use them and the more evident were the skipped steps. I'll try to install some fan on the RAMPS on see if anything change.
Just thought to share it, while I was looking for someone who experiences my same problem.

It's quite possible your stepper driver chips overheat. Add a heatsink, direct a fan to it or reduce stepper current.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

I'm experiencing the same problem and was about to try the things the OP suggests. Can anyone think of a way to narrow down if it's the stepper driver or the motor itself that is overheating?

If the stepper driver overheats you should miss multiple steps (large shift). The stepper won't skip steps due to overheating. It will go to 80 or 100 C before it starts to degrade. If it doesn't burn you it's OK. The other causes of skipped steps are too much friction or too much acceleration. So try lowering acceleration settings.

Also check for friction and stiction. Uncouple the belt and run the axis back and forth by hand. You shouldn't feel any friction or grabbing. If you do then rethink your bearings/bushings.