Plasma cutter question

Date 08-29-2003 13:05

I'm seriously considering buying a 35 amp plasma cutter with a 40% duty cycle. It's an inverter-based model, but I won't mention the brand since I don't want to start a brand-war :-P

Anyway, what should be my realistic expectations for it's cutting capability? The specs say 35 amps will clean-cut up to 3/8" thick mild steel. Should I expect that to be accurate? Will it cut 3/8" thick without needing any cleanup of the cut edges? If not, what's the likely max that I can cut cleanly enough to not require any grinding? I've read on plasmacam's web-site (www.plasmacam.com, a small CNC plasma cutter table) to expect to need 25 amps for every 1/4" to cut cleanly. Does that sound accurate?

Also, assuming 35 amps will cleanly cut 3/8" thick steel, is this starting from an edge, or starting somewhere in the middle of the plate? In other words, can I only cleanly cut 3/8" thick starting from an edge? If so, what's the max I should expect that I can cleanly cut if starting from the middle of the sheet or plate?

And, at a 40% duty cycle, should I expect that to seldom kick off on me? Seriously, I intend to cut shapes out of reasonably thick sheetmetal (up to 1/16" most of the time), but if it cuts fast enough, I could certainly see using the plasma cutter rather than bandsaw to cut out small things like mounting plates, or for quickly cutting 3/16" by 1/2" flat stock into exact lengths (I'm using this size mainly for forming scrolls).

What is the max size that I can sever? I've seen other 35 amp units that say you can sever up to 1/2" thick. Should I assume that's true of this unit even though the specs don't mention it?

This unit doesn't have a "stand-off" nozzle (meaning you have to use your human dexterity to keep the plasma torch the right distance from the workpiece), but I can't see why I couldn't bend some round stock into a simple "stand-off"...or would that cause the arc to jump to the stand-off rather than the workpiece?

Any advice much appreciated!
Dave

By stever

Date 08-29-2003 15:29

Get as much duty cycle as you can afford. I've attempted to cut out a mountain scene with *lots* of other shapes added to it. It will go belly up in the overheating area. Hopefully the plate will not move while the plasma machine cools off. Then let's hope that the machine that you have will have an instant start so that it doesn't start the air purge for 15 seconds and then start cutting after the plasma-cam started tracing. This allows for a clean restart where the duty cycle died. Oh the things that can be found out after acquisition. You're asking some good questions. Keep asking before you purchase.

This will not answer your question, but you may consider that the thicker the metal the slower the travel speed. This is proportional to the size machine that you have and the max thickness that you plan to cut.

Be sure to understand that cutting and severing are not the same and have two different definitions.