Thread: VFD interference problem
15-03-2016 #61It takes all sorts to make a world, I am just glad I am not one of them.
Rob is correct that you shoudln't be spending money without sorting the problem. While the Cslabs are good with noise this doesn't mean it will cure your problem. The noise could be being picked up in number of places, the signal cables to drives for instance which are between Cslabs and Drives.
You NEED to find and remove the noise at the SOURCE. Buy mains Filter for both the Control box and the VFD before buying anything else.
Yes, the building earth goes to the electric company I believe. Standard setup here. I am actually not using any box anymore, it's all out of the box, screwed on a fireproof plate (not metal). I am sorry I haven't posted pictures. Here it is:
The X motor plates have been unmounted to prevent the gantry from twisting. The fireproof board is out of the box for easy access and testing.
All relays are not wired, there is no e-stop, no reset button, no contactor, not fans, no switches (only a switch on the power cord extension), no 24V power supply (Earth and Neutral are daisy chained with the 5V PSU, but there is no Load going to it as you can see).
So, here is what happens:
1. drivers powered, Mach3 in reset mode, motors disabled, VFD powered, spindle off
2. click reset in mach3, motors are powered, enabled and locked
3. I can jog fine on each axis
4. press RUN on the VFD, spindle starts spinning right away. half a second after pressing RUN, I can feel (with my hand) and hear the motors move a few steps (ike 2-5 I would judge by feeling). Obviously I can't put my hands on all motors simultaneously, so I try one by one (the VFD is wired separately so I can carry it around with me).
5. press STOP on the VFD, same thing, right before the spindle stops spinning (so I would say in the lower frequency, around 500/1000 RPM), the motors move a few steps.
There are two parameters to the noise:
1. the time offset between the moment I press RUN or STOP. I guess this depends on the time it takes to get to the problematic frequency.
2. the number of uncommanded steps the motors move
If I press RUN, then wait until the spindle reaches the desired speed (100Hz), then press STOP, wait until it stops, and repeat this process a few times, I would say the problem occurs 7 times out of 10. The number of uncommanded steps and the time offset are always random.
Hope you can see things better now :)
Last edited by eurikain; 15-03-2016 at 08:16 PM.
I can see one problem straight away. You have no main power to the BoB. In the (invisible) picture below the two middle connectors on the right are the main power (12 - 24v) for the BoB electronics. Without that you will get all sorts of random effects.
I tried to copy and paste from the pdf of the BoB manual, but it didnt work - anyway OP has BoB manual.
Last edited by cropwell; 15-03-2016 at 08:41 PM.It takes all sorts to make a world, I am just glad I am not one of them.
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?
I seem to remember that you can also power it through the USB socket. You could try this from the PC, if this works then longer term use a USB plug and lead but cut the cables, identify the power supply cable and wire it to an external 5V supply.
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.
15-03-2016 #70It takes all sorts to make a world, I am just glad I am not one of them.
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