How to sheild a HF arc ignition cutter?

[chinamill5]

Hello everyone.

I wonder which is the best way to shield a HF arc ignition cutter? (So it won't transmit noise to the PC and the drivers.)

I guess the most important part to ground shield (beside the cutter chassis) is the torch hose and the torch (somehow). Do I need to make any special arrangements for the torch? Or is it possible to get away with grounding everything and put a ground shield on the torch hose?

I have seen a Esab machine with a nitted metallic hose around the torch hose.
Where is it possible to buy shielding material? (Like a metallic hose etc.)

/ chinamill5

[Al_The_Man]

I believe you are talking about copper braid shield? I believe some of the wire manufacturers make it like Belden or Alpha. There should be a European source.
It is a pain in the neck to feed it over the torch and high freq./pilot arc wire etc.
Also make sure all the power and table etc all go to a common ground connection and also it does not hurt to sink a ground rod at the common ground point.
Al.

[Torchhead]

Sheilding an HF start plasma can be a challenge. The secret is galvanic isolation (big word for the PC side does not share the same ground as the plasma side). You want the entire plasma table and everything attached to it ground to a very good earth ground close to the table. The chassis of the plasma needs to be grounded to the same nearby earth ground. All table connections (home swtiches, limits, etc) that talk back to the PC have to be isolated. Opto inputs on a breakout are the best way to get that. Most noise is not transmitted through the air but is conducted through the grounds and nearby wiring. Put your plasma on the opposite side of the table (and close to the earth ground) as the PC. Unplug your PC from the AC and with an ohmmeter, measure between the table ground that PC chassis. There should be an open circuit. All shielded cables should be grounded on one end only.

For a suggestion and drawing on plasma grounding with PC's, go to our website at http://www.CandCNC.com and to the Manuals and download the manual for the MP1000-THC.