Hypertherm Cutting Expanded Metals/Grills/Grating

[Sunmixed]

I have seen certain recent models of Hypertherm Plasma cutters do allow continuous arc pilot, where even if the arc does not sense the presence of metal plate, the pilot arc does not shut by itself.

This is very important for cutting expanded metal, grills, and grating. Attached are the photos of the grating I would like to cut. I would like to assume the CNC is performing profile cut, so there will be no machine pauses while cutting the grating. Which Hypertherm model is capable of cutting such grating?

Grating Per whole width and length is 30mm x 50mm.
Cut Thickness: 1 inch.

[jimcolt]

Almost all of the Hypertherm Powermax systems have a selectable automatic pilot arc restart.....this allows you to cut across holes without the arc extinguishing. The circuitry rapidly allows the plasma system to change from cutting current to pilot current....minimizing damage to the consumables...and then when metal is again under the torch...allows for the current to ramp up rapidly to resume cutting.

This process works well for expanded metals and materials with voids or holes....but cann ot be expected to work well on the grating material that is shown in the pics on this post. To do this type of material you would need a complex motion control system that would slow down to cut through the upright material....which appears to be an inch or more in thickness. Not a good application for plasma!


Jim Colt Hypertherm

[plasmamatt]

If the slat spacing is consistent why not just write a program to cut at each slat and rapid traverse between the slats.

[Sunmixed]

Originally Posted by plasmamatt If the slat spacing is consistent why not just write a program to cut at each slat and rapid traverse between the slats.

ive thought of it that way - measured the slats, they are inconsistent.

[Stout]

You throw a piece of 20 gauge, or lighter, on top of the slats and then cut through it and the slats at the same time? That way the torch stays on and just blows through the lighter material until it gets to the slats..

I used to use this approach on my old Esab machine when I had to stop and restart it. Because the restart was on the hole that had been cut, the high frequency arc would not transfer. So I'd throw some scrap material under the torch to get it started and then remove it quickly.

[jimcolt]

If the slats are 3/16" thick....and 1" tall......to the plasma torch you are cutting 1" thick material. You will need an 85 amp plasma to cut 1" thick material at about a 15 inch per minute cut speed. If you go faster than this....the bottom of the arc will tail back at 30 to 45 degrees.....and will cut through the top of the slat.....but not the bottom.

To maintain an 85 amp arc on 20 ga. material.....you would probably have to travel at 300 or more inches per minute. Any slower...and the plasma will burn a wide kerf...the arc voltage will rise past the capability of the plasma power supply....and the arc will shut off.

There is a large discrepancy in speed ranges an power levels between 20 ga. and 1" thick material....trust me....this will not work for the same reasons that the slats on a cnc plasma cutting machine do not get cut all the way through.....the plasma arc tails back and skips over the slats leaving a notch in the slats.

Writing a program to slow down when the arc attached to the slats would work better....but the cuts would be a pretty ugly melted mess at best....as the top of the cut would get through the slat first with the bottom trailing behind. Very difficult for a plasma. As a Hypertherm guy I'd love to tell you it would work well......but it won't!



Jim Colt Hypertherm

[walkcw]

ESAB makes a machine based off of the oxy fuel process to do just this application. It allows you to maintain motion through via continuously feeding welding wire into the oxy fuel stream so the molten metal acts as the preheating agent to cut through the thick portions. If you would like more information I would be glad to help.