Y-axis skipping steps?

[johan]

Hi there,

I've noticed during jobs, I'm gradually losing the correct position off the Y-axis. (X-axis is fine.)
All on original hardware.

I started troubleshooting and when I give a jog command on the Y-axis and then an equal but opposite jog command the nozzle doesn't end up at exactly the same place.
It is not a slack issue as by repeating this, the nozzle seems to gradually move more and more in the positive Y-direction.

It is very quiet subtle and after about 5-6 iterations of 300mm Y-axis travel, the nozzle is of by ~1mm (always in the possitive Y direction).
I've measured this by placing a ruler under the down camera and giving both positive and negative jog commands.

I'm not 100% sure, however it seems positive Y travel is fine, negative Y travel is a little short.
To me it looks like the stepper motor is skipping steps, but I can't get rid of it.

The Y-axis moves freely, and my normal speed settings in Liteplacer software are 3000 for acceleration and 10 000 for speed.
The stepper motor doesn't get hot (only slightly warm) and also doesn't make a lot of noise. (Not when only powered on, nor when moving.)

What I've done so far to no avail:

- Decreased acceleration and speed. Even when very slow I still experience this issue. Very slow is: Acceleration down to 150, speed down to 500.
- Decreased stepper motor current on TinyG (Obviously the Y-axis stalls when current is too low, this occurs at around 40% power.)
- Increased stepper motor current on TinyG (100% power works, but is noisy. Normally, I operate at 60-70% as this seems to run the stepper the most smoothly by ear.)

Is there anything I still can try to debug/solve this?
Could this be a hardware issue with the controller or stepper motor?

Thanks in advance for any hints and tips!

[JuKu]

This doesn’t sound like missing steps, especially since you have tried different speeds and currents. Do try:

-even out the tensions of the belts: Loosen the set screws of the pulleys. Make the belts tightness even. Move the bar back and front a few times to balance the tension on both sides on the belts. Tighten the set screws.

-Check that the set screws on the coupler are tight.

[johan]

-Check that the set screws on the coupler are tight.

It turns out it was indeed the coupler!
Tightening it a bit further seems to have solved the issue and Y-axis travel is now spot on again in both directions!

Thank you for the suggestion!