Mb2hal speed irregular timing of reversing of spindle

Glad to hear you were able to sort it out. I wish simply running a shielded cable and grounding it on one end had fixed my com errors, but no luck for me.

Could try a diffrent 485 converter. I grounded my sheilding to my converter ground terminal.

Do you get comm errors with the vfd not puting out any frequency. I could see more errors increasing as inverter turned on.

You can decrease carrier frequency of inverter also to limit the emf from the vfd.

I've tried at least 3 different ones with varying results from almost usable to totally useless. I get com errors regardless of the running state of the motors. The error rate is arround 40-60% and it bogs things down tremendously.
And it doesn't help matters that I'm trying to control 8 VFDs.

Ohh 8 vfds! It seems like everything has to be perfect for modbus to run error free. Have you tried an ociliscope to check the signal.

No, but I'm not sure how I'd need to hook it up, or exactly what I'd be looking for when it is hooked up. Although I think we might have gotten a new scope at work since the last time I messed with this. (The old scope was an ancient single trace POS. just this side of useless.) This would give me a good excuse to check it out and play with it a bit.