VFD interference problem

[routercnc]

Hi G,

Here are some thoughts on interference in general. My machine was playing up recently with 'external e-stop requests' stopping the machine at random. Strangely the e-stop circuit (24V relay) had not tripped so all the drives were still powered etc. Basically either the BoB or PC/Mach3 had decided it had seen an e-stop signal from somewhere, or some noise, which it decided was an e-stop. This was a pain if you were cutting as it meant homing and 'start from here' messing about.

It could occur during cutting or even just jogging with the spindle on. I fitted an EMI filter in the invertor mains supply, but no difference. I then fitted a MeanWell mains powered DIN rail 5V supply to supply the BoB instead of a 5V feed from the PC, but no difference. I then used an extension cable reel to plug the invertor into a socket on the other end of the garage and then cut out a part without a problem. All the sockets in the garage are on the same ring back to the consumer unit but having some distance between the plugs seems to have helped. There were some unintended heavy cuts in there (including an accidental ~8mm DOC which snapped the 6mm carbide) and it still did not trip.

Going back to your BoB these are about £8 from China. I had one a year ago and it would not give out step/dir signals so in the end I swapped it out for a different make of board and all was well. You could buy one or two more cheap BoBs and give them a go before a major upgrade. They seem to be variable based on reading around and at that price you can see why.

Looking at your signal cables between the drives and step/dir on the BoB - you've used shielded cable, but I can't see if they are earthed?

[eurikain]

Hello routercnc,

Thanks for your message. It is very interesting what you are explaining. It's something I haven't tried yet, plugging the VFD into a complete different socket out of my room. As you can see on the pictures, the room is pretty small, so there might be something there.

You are right about the BOB's signal cables. STEP and DIR are CY-2 0.5mm^2. The shield is not earthed. I know I should, this was just really me trying to get minimal connections.

I think you're right with the process, as others have suggested. So here's what I think I'll do:
1. try power the VFD from a socket located in another "block" of my house (one that's on a different breaker circuit).
2. If the above doesn't work, I'll put an EMI filter on the mains of the VFD (or inverter as you call it)
3. If that doesn't help, I'll buy spare BOBs from China.