problem with peircing steel (oxy-acet)
problem with peircing steel (oxy-acet)
(OP)
not really a mechanical eng problem, but i figured someone here might be familiar with burning tables. Anyways the table i program is capable up to 12" plate, but we rarely run anything over 2-3". The machine is wonderful it can cut any shape to perfection, but it seems to be limited to peircing, Whenever a production run is done, the tips get dirty after just a few peirces, taking time and adding frustration. Also with heavy plate, say 2" its almost impossible to peirce without messing up the tip. (the molten steel has nowhere to go but up, into the tip). I know theres shops that can easily peirce 3-4 inch plate all day long but how? I am stumped on how to do it, ive tried progressing forward slowly as the peirce begins but no luck. Pre-drilling is also not an option as it add tremendous amounts of labour, especially when runs of 200+ parts is common. Is anyone familiar with this, or has anyone seen it done?





RE: problem with peircing steel (oxy-acet)
Mike Halloran
Pembroke Pines, FL, USA
RE: problem with peircing steel (oxy-acet)
RE: problem with peircing steel (oxy-acet)
Mike Halloran
Pembroke Pines, FL, USA
RE: problem with peircing steel (oxy-acet)
http://www.torchmate.com/qa.htm
Another page I found suggested cutting squares or polygons, fast, instead of circles, but suggested that it might be hard on your gantry.
Mike Halloran
Pembroke Pines, FL, USA
RE: problem with peircing steel (oxy-acet)
A bit more on the subject of plasma vs. oxy-fuel: When you mount a plasma torch in a machine, the piercing capacity is reduced by about 50%, because you can't tilt the torch head. You just have to blast your way straight through. If the plasma cutter doesn't have the amperage to do this, molten metal splashes up and fouls your electrode and nozzle. Starting at a drilled hole or an edge allows you to pierce at full capacity.
RE: problem with peircing steel (oxy-acet)
RE: problem with peircing steel (oxy-acet)
You need to select the proper torch tip size for cutting. The cutting tip provides for preheat and a jet stream for pure oxygen to cut. Preheat the spot, angle the torch, add oxygen to blow the metal out of the hole.
RE: problem with peircing steel (oxy-acet)
IFR, you are right, we also have a plasma head mounted, and when you mess those up, the arc ruins the consumables and in the garbage they go. But if you cut only what your amperage can handle, they work great and can peirce all day long, and they never get dirty from general use. MAybe its the 85 psi of air running through it keeping all that popping scale away?
Also as you mention edge starting eliminates a lot of problems, but again in multiple runs of the same part its not always possible. With larger parts, leaving an open edge also creates a stress releif point were the part is no longer contained and can move a large amount during the cut.
Mike, thanks for the link,and your time. I'll check it out.
RE: problem with peircing steel (oxy-acet)
I do not know if this is a practical solution for your problem.
Years ago I worked for a company that used a three head oxy fuel profile cutter (magnetic follower type), when they needed to do piercing, a hand torch was used to blow a 1" dia hole through at three points on the plate. The cuts were then edge started from there. The operator hand guided the cutters back to the profile then let the machine run.
The operator also had a handful of metal strips the thickness of the cut, which he inserted into the kerf as the cut progressed, this reduced the distortion of the part.
B.E.
RE: problem with peircing steel (oxy-acet)
Marmon,
Check to see if you can control the initial pierce height. If the torch is too close while piercing, it would also cause slag to go back on the tip.
Depending on the quantity of parts and size, you could set them up to edge pierce. That way the slag is blown down instead of back up into the tip.
The parts could also be gang cut, reducing the quantity of pierces. This will only help with your external cuts.
Regards
RE: problem with peircing steel (oxy-acet)
Some companies have tips just for piercing plate over 6” thick.
RE: problem with peircing steel (oxy-acet)
EdDanzer i can honestly say i have never pre-heated that long, usually after say 20 seconds on 1" plate the material starts to turn molten on the surface, then thats when we pierce, i will try a slower longer pre-heat and see if that helps.
Thanks for everybodies suggestions so far
RE: problem with peircing steel (oxy-acet)
RE: problem with peircing steel (oxy-acet)
Bob
RE: problem with peircing steel (oxy-acet)
RE: problem with peircing steel (oxy-acet)
RE: problem with peircing steel (oxy-acet)