Y stepper "jerking"  

Re: Y stepper "jerking"

1. When you remove the belt, Y-carriage should move absolutely freely within all range. Freely means with almost no force used by hand.

2. Y-motor pulley, Y-idler and Y-belt-holder (on the bottom of bed) should be precisely aligned both horizontally and vertically, so the belt can't bend or twist at end positions of the bed.

Re: Y stepper "jerking"

3. Y carriage should move all the way back and trigger the end-stop (you should be able to hear a "click".

Peter

Re: Y stepper "jerking"

Thanks for the tips to look out for guys, I'll report my findings this evening. Seems unusual a printer fresh out of the box could have a misaligned Y beltholder/motor/pulley, but I'll make sure to check.

I recall the Y motor felt warm, but I believe so did the Z motors so I suppose that's normal during operation?

Re: Y stepper "jerking"

Yes, the motors do get wam in use and the Z motors are kept on even when not printing to maintain X axis alignment.

Peter

Re: Y stepper "jerking"

Evening guys,

Remember those zipties I mentioned in my opening post? While checking under the Y carriage for the umpteenth time I noticed a bearing held in place by one of the stock zipties appeared to have moved from its position. I now replaced it and am letting the X/Y calibration sing me the song of the i3 mk2's people.

If the ziptie really was the culprit, I guess this experience will be a reminder for me to hate zipties for everything (instead of only for cable management )

I'll keep you posted.

Re: Y stepper "jerking"

If you don't like zipties (who does?) and want to keep the rest of the design unchanged, something like this http://www.thingiverse.com/thing:477845 should work.

Re: Y stepper "jerking"

Thanks for the link David. Sadly, zipties appear not to be the culprit after all. The "jerking" problem continues.

Made observations:

I made two quick videos with my smartphone to demonstrate what's going on. Do note the lousy microphone somewhat alters what you hear. Lower your speaker or headphone volume before hitting play.

In the second video I also give a few taps on the belt to try and demonstrate the tightness.
In both vids, I'm trying to move the Y axis in either direction by rotating the control dial (CW or CCW) in Settings -> Move Axis -> Move Y

Could it be the timing belt is too tight and this causes the Y stepper motor to struggle like that?

Re: Y stepper "jerking"

Second video is marked as "Private"...

Peter

Re: Y stepper "jerking"

Woops, should just be "unlisted" now. Sorry for that.

Re: Y stepper "jerking"

Remove the belt, put a piece of coloured tape on the pulley (like a flag) and try doing the same again. Upload the video.

It looks like either a faulty motor or a connection problem.

Peter

Re: Y stepper "jerking"

Thanks for the suggestion Peter, will make sure to do that tomorrow and report back.

Re: Y stepper "jerking"

I think this is a step-by-step process to find the problem.

If the motor turns OK, without the belt/carriage, then we know the problem is with the belt or carriage.

If it does not, then we have to check the controller by swapping the X and Y motor connections at the RAMBo. Re-test the Y motor by moving the X axis. If the motor is OK, then see what happens to the X motor when you move the Y axis. If the X motor behaves badly, then the fault is most likely in the RAMBo.

Hope you follow the logic there. End result will either be a solution or you will have to contact support...

Peter

Re: Y stepper "jerking"

Could it be the timing belt is too tight and this causes the Y stepper motor to struggle like that?
It could. Sometimes the provided motor pulley is a little bit asymmetric, which causes fluctuating belt tension. Try to losen the belt by one tooth.

Re: Y stepper "jerking"

The plot thickens! It took a while for the symptom to show its ugly face again (it's like the offending part knew I was breaking out the good stuff camera-wise), but then it happened:

The intervals of rattling you hear in the background is me rotating the control dial in either direction until the electronics determine the limit reached.
Next step for me is to plug the Y stepper to the X headers on the rambo to see if it's a bad driver or bad motor.

Re: Y stepper "jerking"

So I swapped the X and Y motors on the rambo and could no longer reproduce the issue, even with the belt attached to the Y stepper pretending to be X. After reassembling everything (with the wire bundles in their proper slots), I could do a full X+Y calibration and Z calibration.

Right now, I'm inclined to suspect a bad connection combined with thermal expansion from the electronics warming up.

Re: Y stepper "jerking"

Great; most likely a poor connection. The pins inside the connector can come loose occasionally.

Question: the pulley looks very close to the stepper body. It's not rubbing on the body is it?

I have about a 4mm gap between end of pulley and motor body.

Peter

Re: Y stepper "jerking"

Hi Peter,

The pulley does not appear to be rubbing against the body, but I'll make a note of it to shift it a millimeter, just to be on the safe side.

Currently doing a testprint to validate the axis are now working as they should.

Re: Y stepper "jerking"

If you move the pulley one way, you will have to move the motor the other and that may affect the end stop.

Peter

Re: Y stepper "jerking"

While printing I took another look at the pulley and it seems there's about 1mm of play between the pulley and the motor. So far, (after replugging the wires) the printer has been behaving very solid. Currently doing my second testprint (first was the prusa logo and it came out great), if that one comes out well I suspect I can move on to printing spare parts.

Thanks Peter and David, you've been a great help in troubleshooting, I was at a loss.