G320 and jerky movement

[Ed Williams]

I built a new table using belt drives, it is 4'x4' and the movement is 15mm per rev on my motor with 250 encoders. I have not completely tried to hold it back but it will give you a good tug holding on to it. The table moves very smooth when moving it manually. But when running code or jogging I can feel a small jerk. I can verily see it but it’s there. I’m using Mac3 and have the steps at 1693.33333. I was wondering if this low of steps mite be the problem or would larger motors hold it steadier. This is on my X axes and I have change the wiring to use my Y and it is still there. I know my X is much heavier than the other axes so that’s why I was thinking larger motor. Any input would be appreciated.

Thanks Ed

[MattTheNoob]

You'll definitely want some feedback from more experienced folks here, but you could be experiencing inertial coupling, where under certain conditions, the weights, inertia, stretch in the belts and other components can create vibration.

Try running the axis at different speeds... that might lead to some clues.

Also, you may want to look for any eccentricity or mounting problems with your motor or pulleys. (i.e. are you getting one jerk per revolution of any component?)

Maybe try a heavier belt (too stretchy) or look at your tensioning mechanism.

Just some thoughts. Good luck and let us know what you are finding.

[MattTheNoob]

Oooo... one more thing to try. If you want to take the G320 out of the equation, hook a low voltage dc supply directly to your motor and see if it is still jerky. Maybe wire a pot into the system so you can try different speeds.

If it runs smoooooth then you know you have something with your encoder or drive.

If it is still jerky, they you probably have something mechanical, or with the motor itself.

[Ed Williams]

I think I have found the problem. It is inertia since I am having to use such high gearing the 23 nema's are not big enough. It seems strange because I have a lot of torq. I have 25mm with wire in belts. They are very strong and no stretch in them.

Thanks Ed

[ArtCNC]

I have looked & learned over the years on this great community & now signed up.
May I start with a problem with a G320. Bought two, first worked just fine,
second (I'm using SEM Servo MT30 bench test) tuned in not too bad but
further tuning with Gain & Damp do nothing when turning screws ...careful not to over tighten them.

Is the G320 at fault or me?
P.S Using AMT 102 ENCODER

Thanks.