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Plasma doesn't cut square

chassis_builder

Aluminum
Joined
Dec 25, 2009
Location
TX USA
Can anything be done to make a plasma torch cut square? The one in the shop where I work has both a hand held torch and one mounted on a CNC table. Neither will cut square in anything over about 1/4 inch thick. Even with a new tip and electrode they cut at an angle. Sometimes it actually cuts better after the tip and electrode have been used for a while. It is not always consistent as to what way it will cut at an angel or how much of an angle it will be. I have to cut 3/4 and 1 inch plate with it and getting a good cut is hard. Any suggestions or is this just the way plasma torches are?
 
To a degree all plasma cut edges have some angle to em, its the nature of the beast. But torch and especially consumables can do one hell of a lot to reduce it. Hypertherm is good - great stuff, but some of the others are on a par, then there’s some real crap. Plasma has come a long way in the last few decades, thats very visible in the cut quality. Equally visible in the consumable life span too.
 
Can anything be done to make a plasma torch cut square? The one in the shop where I work has both a hand held torch and one mounted on a CNC table. Neither will cut square in anything over about 1/4 inch thick. Even with a new tip and electrode they cut at an angle. Sometimes it actually cuts better after the tip and electrode have been used for a while. It is not always consistent as to what way it will cut at an angel or how much of an angle it will be. I have to cut 3/4 and 1 inch plate with it and getting a good cut is hard. Any suggestions or is this just the way plasma torches are?

Have to assume you are cutting carbon steel? We are facing the same situation and after many months of digging we came up with two solutions. Upgrade to a new Hypertherm Tru-hole system (with table retrofit) or stop using Plasma for accurate cuts. The upgrade is too costly for our budget so we just had to change our procedure.

When we have to make an accurate and square cut we always switch to our Propane/Oxygen torch with appropriate tip size. The Koike D7 tips do a great job.

I cut and sell Lathe Spanners on this forum and all are torch cut. It's the only way I can get straight, square sides and clean corners.

Walter
 
Basically the only thing that can be done with a normal plasma torch is to angle the nozzle to compensate. With the proper angle you can get a straight edge on the work with an even worse angle on the scrap, which requires not sharing cut lines on multiple parts,
 
Thank you for the replies. The machine is a Thermal Dynamics Professional 152 Cutmaster. I have worked at this shop for a year and a half and it was upgraded sometime before I stated but I don't know how long. I am cutting 1 inch mild steel. I can get a pretty good cut on a straight cut with a guide by tilting the torch but when cutting a hole, 1 5/8 diameter, with a guide it doesn't work so well. I have to go back and recut part of the hole without the guide where the side slopes into the hole. Fortunately precision is not needed on this job. I guess I will just have to live with it.
 
Thank you for the replies. The machine is a Thermal Dynamics Professional 152 Cutmaster. I have worked at this shop for a year and a half and it was upgraded sometime before I stated but I don't know how long. I am cutting 1 inch mild steel. I can get a pretty good cut on a straight cut with a guide by tilting the torch but when cutting a hole, 1 5/8 diameter, with a guide it doesn't work so well. I have to go back and recut part of the hole without the guide where the side slopes into the hole. Fortunately precision is not needed on this job. I guess I will just have to live with it.
What Walter said....and if this is a hand operated torch, go with propane/oxy
(or acetylene/oxy) as well.

I retrofitted my C.N.C. machine with a inexpensive machine torch from e-bay,
for $50 plus shipping, came with a 3 hose manifold( with remote valves), and 3 tips, all interchangeable with Airco/Concoa.
 

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Plasma torches cut more square on one side of the kerf than the other. It has to do with the rotational direction of the vortex. For that reason tables will only run around an object in one direction to get the most square cut. Some manufacturers actually supply cones that spin the air in the opposite direction and they can be special ordered. Make a straight cut and determine which side give the more perpendicular cut.
 








 
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