Help with interference/UCCNC

[NiklasJ]

Hi everyone

Im new to CNC world and could use some help with a problem I'm having. I've recently built my own plasma table and I'm having some problems with what I'm guessing is eletrical interference. The machine runs great most of the time and everything "works" as intended. The problem is that sometimes when the plasma torch is being turned on, the breakout board stops communicating with my computer and pretty much just dies; I have to restart the breakout board and restart the whole cutting process.

Most of the time it's not that big of a problem; If it gets "running" it usually works fine, even when cutting with some fairly high amperages. However on certain parts with lead-ins and small pieces, the torch easily "sputters"/"spits" when trying to start up. If that happens, the breakout board "dies" for a lack of a better word, immediatley and i have to start over from the beginning again.

Im using the UCCNC software with their UC100 USB-Printer port adapter. The error message that I get when this happens is something akin to "The UC100 adapter has stopped responding/communicating. The program is now closing." I do NOT get any weird movements from the gantry, nor any signs of interference on/with the computer in general, only the breakout board/UC100 adapter error.

The CNC electrical system is housed in a steel box, seperate from the PC and plasma cutter. The plasma cutter is roughly 1.5m away from the CNC eletrical system. Everything should be grounded correctly. The ground clamp for the plasma cutter is always grounded in the material being cut with a welding clamp. All wires in the CNC electrial system are shielded.

The following objects are grounded on the star ground point inside the CNC electrial system steel housing:

• Gantry/Table
  All motors
  All drivers
  All cable shielding
  The breakout board
  The 24v powersupply for the CNC system

The manufacturer of the gantry could not offer much help since their gantry is mostly used as routers, thus they have limited support and experience in this matter. How can resolve this problem? Any tips or suggestions is greatly appricated.

Some information on my CNC system:
Plasma cutter: CUT-120 IGBT Inverter (Chinese origin probably, 4-5 years old)
CNC-System: Raw CNC 1.5 Extended XL
Table size: 1.8m x 1.3m
Motors: Nema 23
Motion controllers: DQ542MA
Breakout Board (See picture):

[djreiswig]

Not familiar with this system, but just a thought...Is your USB cable shielded?

[robertspark]

USB is never a good choice with plasma in my opinion..... but it can be made to work (I got the troublesome USB Smooth Stepper to work for a while before I wanted THC and it was not available with the plugin at that time)

CUT-120 IGBT Inverter is not a very good plasma cutter..... bear with me I am not rubbishing it.... but for CNC it uses a high frequency start and this HF start will create stray electrical fields that may affect the USB communication

Once the PC looses communication with the UC100 the game is lost and the controller does not know where the machine should be and just gives up....

If you really want to try to get it working with your setup....

As said in the previous post.... check your USB lead.....

Another option.... (which is what suffered with with the USB Smooth Stepper at the start)..... check your connection between the PC and the UC100 and the breakout board..... you want to make sure that at no point is the UC100, or the breakout board or any intermediate USB connectors are connected to chassis earth of the casing of the cnc controller cabinet.

USB suffers badly from ground loops.... you could try to install a USB filter .... search google the audio guys use them.... I have not tried one but they "may" work or be worth a try on noise sensitive USB communication.

[NiklasJ]

Thanks for you suggestions. I assume you both think that the USB-cords might be the source of the problem?

Yeah I agree that the CUT-120 IGBT Inverter might not be the most suitable plasma cutter for this application. I want to rule out everything else before I invest in a new plasma cutter though. Im not sure, but I think that the USB-cables are unshielded. They do have ferrite beads on both ends though, but I assume that's not the same thing?

[robertspark]

another usb lead is an easy fix.. or test.. if the lead came with the uc100, cncdrive say they are quality leads... so it should be ruled out.

the ferrite cores / beads kind of only filter out the signals after they have been distorted.... scielding stops the signals being distorted in the first place..... the ferrite cores work in a certain spectrum / waveband..... if you can put the fences up first it's probably better than learning how to lasso horses once they've left...

[NiklasJ]

I understand. I've ordered some new premium USB cables that are shielded and supposed to be using 100% pure copper leads/wire. I'll test them as soon as i get them. In the meantime, If you guys have any other suggestions than the USB cables, I'm happy to hear them as well.

[robertspark]

I would suggest that you check your wiring and power supply arrangement..... a common error is to join the zero volt connections to chassis earth