Help please. Dip switches and mach 3 settings

[Radu_Andrei]

Hi again.

I wired the switches and e stop did the setup as cropwell said. All fine until I power up the steppers, and then I get noise problems again, limit switches triggered, external estop requested message which sometime does not reset.
I disconnected the vfd and still no good.

As adviced by Clive S, I did more research on this topic, and ironically, that raised more questions.
1. is it a bad grounding practice to pigtail for example the stepper shieldings, and then run a ground wire to the mains earth, or should I run a separate ground wire from each shield to the earth. Does it make a difference?
2. as the spindle is set on conductive material, it.s ground wire becomes the framework.s ground as well, and running another ground for the frame will only create a ground loop. is that correct?
3. does the fact that having all components in one enclosure, raise this kind of problems, even if all wiring and grounding is done correct? should I have 3 separate ones, pc, stepper control, and vfd?
4. all wires run in the cable drag chain, meaning I have low and high voltage right next to each other. so from all I found online, the easiest way in my opinion is to add a relay next to the breakout board, and have the limit switch wires at 12 or 24 v. or should i physically separate them a couple inches apart, or improvise a separate carrier for the low voltage wires?
5. for estops and limits, I have an "hardware" and a "software" estop, one to a contactor, one to mach3, is it useful or necessary to approach the limit switches in a mechanical way? (like some relay which kills the power to the driver, or source)
6. in the vfd manual it says that you should not use a contactor as a switch for the vfd. So i use a cam switch to turn it on, but wired after the contactor, so hitting the "hardware" estop, will kill power to everything, turning just in this cases the contactor into a switch. The I reset the cam switch to zero, power up the contactor again, and turn on and off the vfd from this cam switch. Is there any problem in this wiring method?
7. except the vfd main, where else should ferrite accessories be used? sources mains, between sourced and drivers, breakout board 5v wires.
8. does the breakout board, being close to the drivers and/or vfd, can cause noise issues?


I.m considering taking all the electronics apart and start from scratch, a better cleaner design, easier to troubleshoot, and would appreciate very much an advice on how you would do it. Assuming you have in front of you all the parts involved, how would you design it, in order to never, or at least most of the time, not encounter this kind of problems.

[cropwell]

Hi,

Having typed a long and laborious answer to some of your points, I then lost it all because this forum software is crap.

Here we go again :-----

1. a: Pigtailing - no problem, just remember shields should only be earthed at one end or you may get earth currents to make your shield as the primary in a transformer with the secondaries as your signal wires.

1. b: Single earth point in control box, all earths and shields and mains earth to it. Topographically, earth connections are a star, however spur connection is allowed as long as it is a single line spur chain earthed at one end only at the star point.



2. Yes.

3. The VFD is usually the main culprit in creating electrical noise and it is common practice to keep it out of the main enclosure (which should be an earthed, shielded box I.E. not plastic).

4. DC voltage supply lines are normally no problem in a steady state, switching transients can be a nuisance, but these would only be when there is an inductive load, like a pump motor, so these are best shielded. Homes and limit switches are normally in a steady state, but it wouldn't hurt to shield them against stray EM crap.

5 and 6 - whatever !

7. I hate ferrites and their nasty little cousins - slugs. Design out the problem if you can.

8. Noise from the BoB, not usually (only when it gets drunk on a Saturday night) but seriously - I refer you back to 3 above.

You should test each earth connection by continuity checking from the central earth point to the earthed appliance. Disconnect the appliance earth and check that the continuity between the earth point and the appliance then disappears. If it doesn't - you had a loop.

Hope this helps !

[Clive S]

As Rob said. But I hate timber boxes and think of the fire hazard. If you can go with a metal box with the VFD external to it.

edit: something like this could help https://www.jaycar.com.au/iec-emi-po...6-amp/p/MS4003

[cropwell]

As Rod said.

Hi Clyde, who's Rod?

Cheers,

Rob

[Clive S]

Well spotted now edited.

[Radu_Andrei]

Thank you Rob for the detailed answer.

Got it. Metal box at least for the vfd, ideally for everything else.
By shielded box, do you mean just an earthed metal enclosure, or aluminium foil :P or like a faraday cage with chicken wire?

Out of curiosity, Clive, about the fire hazard, how hot do this components get?
I did it from particle board cause it.s easy and fast, and I put all components on a metal plate, actually on the side panels of the pc enclosure, as I dismanteled it. All panels beeing raised half an inch from the wood.s surface. I could not wait to have the cnc running, and was planning to upgrade after a few months of use, and yes, I.m aware it.s a crap and unprofessional design, but it seemed to me a resonable prop at the time.

And should I add an enclosure fan to the drivers as well, as I already have 2 for the vfd enclosure.

[cropwell]

Hi,

If you don't want to replace the control box with a metal one, you could line it with aluminium foil (https://en.wikipedia.org/wiki/Tin_foil_hat) but to be any use it would need to be earthed. I don't think the guy in the wiki is grounded (I apologise if you don't get that joke straight away, it is a little play on the vernacular - in this instance 'grounded' means connected to reality).

LIDL sells adhesive backed foil tape, when they have it.