Recommendation on Plasma cutters

Date 04-03-2001 16:02

I am looking to buy a plasma cutter for a small job shop. I deal with various mat'ls Car Stl, St Stl, Aluminum. I would like to know what equipment has a good reputation and is user freindly. Material thickness would range up to 1" thk in Alum on rare occasions, would I need something that would cut through that or could I get away with a smaller unit? Also I know of some used equipment around or would this be a waste of money?
I have not had any experience with plasma cutting in the and your help would be appreciated

Thanks

By Ti double-G er (*)

Date 04-04-2001 11:13

Hardfacer
We use a spectrum 700 in the shipbuilding company i work in. It gets moved between two divisions and has endured years of hard use and abuse. It uses a fairly common electrode assembly so consumables are readily available. It is designed to run on shop air but for really thick aluminium +- 1" or fine work where a high degree of edge finish is required we use a proprietary plasma gas. My only caution to you would be not to buy an underpowered machine for aluminium work.

Sincerely......Sean

By hardfacer (*)

Date 04-04-2001 17:30

Thanks Sean
Would regular shop air work or must it be specially filtered? What about the machines with their own compressor. or what type of gas would be used? I was told that to cut 1" Aluminum you need a machine that is rated to cut 2" steel.
Thanks for your input
Dave

By Ti double-G er (*)

Date 04-05-2001 02:44

Dave
. The people who sell these machines do make some distinction on thickness of cut and thickness of shear with thickness of shear being about 40% higher than cut. Miller says that my Spectrum 700 (50A) will cut 5/8" of aluminium but we do routinely cut 1" of aluminium, But the cut is not pretty on this thickness of material. If I was cutting 1" thick all day I would look at a 70A machine. As for air we use plain shop air running through a common water separater, it leave the compressor at 125 psi and we regulate it to 80-90 psi at the plasma unit using the built in regulator. The gases used tend to follow the same lines as those used for gmaw on a similar material. The gas for aluminium is a helium/argon blend (75/25)-(90/10). The higher the percentage of helium the deeper the cut or higher argon for cleaner edge. C steel uses CO2 or more rarely a CO2/argon blend and once again the percentage of argon controls the cleanliness of the edge but limits the cut depth.
As for the machines with a piggy back compressor I have never used one, but I would assume that they work fineand are oriented toward users who want an all-in-one package such as rebar tie'rs.
Oh, and one other thing is that a decent sized plasma can be used to cut all sorts of odd stuff on ocassion such as concrete
I hope this helps you out
......Sean