Mike,
As a long time veteran with Hypertherm....we take exception to your statement below regarding that AVHC (automatic torch height control) is not needed in some plasma cutting applications.
In order to get acceptable life and good cut quality...today's plasma torches require that torch to work distance is controlled to within plus or minus .020" of the recomended standoff height from the plate during the cut. (With our industrial class high definition systems, height must be controlled to within plus or minus .004") In many cases...the recomended standoff is .060" to .080" off the plate while cutting. There really are not any large plates of steel....that will stay flat within .020" over their entire area, and further, as the cutting bed slats get used..the variation in torch to work distance can vary quite dramatically over the perimeter of a plate. Add normal heat induced warpage caused by plate stress to the equation....and expect height variations that must be corrected on all plasma cut plates.....without this correction you can surely expect collisions with the plate which will damage consumables and torch as well as situations where the torch is too far from the plate...which will cause extreme cut edge bevels and dross.
As important as accurate control of height whicle cutting....is the need to sense the surface of the plate before every cut , then retract to the manufacturers recomended pierce height. This function is called IHS (initial height sensing). One pierce too close to the plate will destroy the nozzle and shield on a plasma torch.
Torch height control should be installed on every plasma cutting application for acceptable ct angularity and for the best consumable life....as well as for better productivity. With a good THC you can push the start button and walk away from the cutting machine....without it, you need to stay at the machine and tweak the torch height every few seconds!
Jim Colt Hypertherm
This is an option on our tables, and if the material remains flat (say a heavier gauge plate) then an AVHC is not needed.
-Mike[/QUOTE]  |