CNC / TIG Welding Problems

[mnajork]

It seems that the RF produced by our TIG welder interferes with our Tormach PCNC mill, causing the spindle to erroneously spin up even with the e-stop on, as wells as causing flickers on the screen attached to the computer and various random programs opening up. Obviously, this is a problem when trying to machine something. And suggestions to solve the problem? A faraday cage around the electronics box of the Tormach possibly?

[JamesCH95]

Are you doing AC tig welding? That's usually the culprit... see if you have a high-frequency adjustment on the welder and turn it down. Or try welding with a "soft" AC arc, not a square wave of anything fancy. It's the high-frequency waves used to make square and triangle welding waveforms that screw up electronics.

[DonRotolo]

Or give Tormach a call, perhaps they know of a way to help avoid that.

Also, as James notes, square waves produce RF energy well into the several MHz range. If you can avoid them, do.

Distance helps, as field strength decreases by a cube law.

Make sure both the TIG and the Tormach are well-grounded, ideally with an RF ground in addition to the safety ground (which may be useless at RF)

[Gdeaver]

I had a conversation with another of our mentors on Thursday kind of talking about this kind of problem. It may have more to do with the way the machine is grounded. You may want to look at the CNC's installation and wiring diagrams. Many manufactures want a dedicated earth ground right at the machine. This seams to really bother electricians and and many times problems like this happen because of grounding issues.

[eugenebrooks]

Maximize the distance between the TIG welder and the CNC equipment.

Connect the work piece directly to a good earth ground near the location
where the welder "ground clamp" is connected to the work.

Try and line up the welder ground cable with the torch cable to minimize RF radiation.

On the CNC equipment, encase all cabling in grounded shielding to minimize RF pickup from the welder and install a choke on the power input of the CNC electronics.

Adjust the spark gap on the welder to produce the minimum voltage needed to stabilize the arc.

Ultimately, if you can't provide the needed isolation you have to power down the CNC equipment when running the welder. These two pieces of equipment are not very compatible.

Eugene

[Dick Linn]

"...spin up even with the e-stop on..."

That is very scary. What else on the Tormach can be turned off during normal operation? What do you do when changing tools?

[Al Skierkiewicz]

I have to back up Gdeaver on this. In general, electricians do not see a need for signal ground when a safety ground is in place. The welding machine can develop signal across the ground line that may be common to both machines.

[Dick Linn]

The manual for our old Syncrowave 250 has a whole section on special grounding for HF for anything in a 50 foot radius, including these items:

welding table
work lead
welder case
disconnect box
metal garage door tracks
cover all windows and doorways with grounded copper mesh
water pipes
electrical conduit
metal building panels