Hey Bar,
installed the new board you sent me. However, the pulsing is still there in the left motor.
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Darn! Well at least now we know itās not a hardware issue.
@krkeegan do you have any thoughts on what could be causing this?
Wow, sorry I missed all of this. Based on all of the facts I am pretty confident we are looking at a PID setting issue.
Try decreasing Kp on the Velocity controller to 6 or maybe even 5. So enable custom settings for the velocity PID and the values should be
Kp = 6
Ki = 0
Kd =.28
I suspect the Kd will have to be adjusted if this helps.
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Tuning down the kp velocity to 5 and the pulsing is gone! There was still some pulsing when kp is set to 6.
Thanks !!
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phew glad to hear that.
Let me test the values on my machine sometime this weekend. I may have a more complete list of settings for you to try.
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After changing the Kp value, i have notice the print is not straight anymore. It slope down while moving right.
The black marker line is parallel to the edge of the 4x8.
Do i have to re calibrate the machine?
Yeah, the PID shouldnāt cause this. I suspect something in the calibration isnāt quite right.
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Did this issue go away, did messing with the calibration or PID controls help? I donāt want us to forget about it just because weāre stumped.
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I also had the jerky left motor issue, and when I changed the PID value to @krkeegan values then down to 5 as stated by @Johnny5, mine now works great with very smooth operation. Thanks guys!
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Sorry, didnāt have a change to update the result.
Its printing very smoothly after tuning the PID value.
However, I still have an issue trying to figure it out, not sure if its all related.
It seems like the right motor is not catching up when i move the sled to the right, especially when the sled is at the top part of the sheet. Its hard to describe what im seeing, but when looking at the plot in GC, the white cross and the red cross move apart from each other when the sled traveling to the right. Then at the end they merge back together (only right motor is moving during the merge). This only happen moving to the right, not to the left.
It seems like it doesnāt happen when its printing tho, maybe its because due to slower moving speed.
I didnāt have much time to play with it over the holidays. Also, I can take a video if you donāt know what Iām talking about 
Thanks
johnny
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This could certainly be an issue. We can dial back your max speed and see if that solves you problem. If you update to the master version of Firmware and GC you can change one of your macros to be
$15=900
Run that once. It will persist through restarts of GC and the firmware. This bumps you maximum speed down to 900mm/min.
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Great! So it sounds like we just need to step back a little bit on the PID values? Letās try to do this in the next version which comes out one Wednesday?
I know exactly what you mean by taking a second to catch up, and I think @krkeeganās suggestion to lower the max feedrate is spot on. I didnāt even realize we had a command to adjust that (another of @krkeeganās fantastic contributions). It makes sense to me that it would be noticeable at the top of the sheet where the motors are under the most stress, but it seems strange to me that it would only be in one direction.
Iām starting to wish for a command-line popup accessible in GC for things like this. Would this be useful?
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IIRC the two motors are managed by different clocks driving the PWMs, one of
which has a substantially higher clock rate than the other. That could be
contributing to this sort of difference.
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