Going Crazy...heh kinda

[ColdCnc]

Hello everyone

First off a little bio about myself, I have recently changed careers and started my apprenticeship as a sheet metal worker. The company I work for has a G5 fabricator from fastcutcnc http://www.fastcutcnc.com/g5-fabricator.php,
And I was promptly introduced to cnc plasma cutting (this is where my sanity starts to sip). I was given a basic run through of the system and operation, my instructor did not even know what THC button did, so you can guess that I've had a steep learning curve. I have brought the machine up from an poor cut quality consumable gobbling monster to a nice cutting consumable friendly something. Now here's where the stress comes in the boss has noticed that we are now cutting better faster and now have the ability to cut out very nice intricate designs. but theres still some work that needs to be done. The most pressing matter is cutting the hvac parts the torch has a nasty habit of diving into the material I'm cutting (usually 26-24 gauge galvanized) and offseting the torch or in the worst case dragging so hard it will snap the retaining cap of the torch, the other problem I'm having is cutting off the cut path example say I'm cutting a rectangle 12"*20" with a 1" by 1" notches out of each corner the machine will cut three corners perfectly then will go around
the fourth to fast seems like the proportional slow down setting in the software completely ignores that theres 2 90 degree cuts that need to be made. I've contacted the company and I am still waiting on two emails an a phone call
(I'm not very happy with fast cuts customer support)

If anyone could help me I would really appreciate it
Thx

[Torchhead]

Not knowing what kind of THC that unit has, it's difficult to offer an idea about the head diving. Here are some simple physics: On tight turns the machine has to slow down (part of the toolpath control in the controller software). When a plasma slows down (especially on thin material) the tip starts cutting more air and the voltage shoots up. When the voltage shoots up it causes the THC to over correct and drive the head down. If the THC is integrated with the control software (i.e. the control software is in charge of the Z position just like the X & Y) it can sense the slowdown and tell the THC to ignore the voltage spike. Stand alone THC units do not have that capability.

The control software should use Constant Velocity (CV) so that changes in direction are handled gracefully. I am not sure what you mean by proportional slowdown is unless it's actually a form of CV. It needs to have "look ahead" toolpath capability (like you do driving your car) and anticipate a sudden change in direction and adjust the speed.

The last thing is that the THC may be getting noise into the controls and moving when it should not. If it (rather than the control software) is in charge of Z position then it's like a Dr. Strangelove arm....it does what it wants.

Tom Caudle
www.CandCNC.com