How do you set the initial Z Height?

[Normsthename]

I am converting my homebuilt CNC Wood Router into a Plasma.
I have a Campbell THC-300 and a Cutmaster 81 arriving very shortly
I am running MACH3 as my controller.
When I cut with the CNC router, I touch the tool point and then zero the DRO and then load the program and start cutting.

What is the procedure when using the Plasma?
I know the THC will automatically keep the plasma tip at the optimum cutting height while cutting.
Do you need to set the Z Axis height before starting???
Can someone please explain the startup procedure to plasma cut a part.
I will be using Sheetcam for the Plasma Software.

Thanks

Andy

[Torchhead]

Join my CandCNCSupport Site (where we also support the THC300) and go to the files section for a "floating head". Also some pictures of mine and others in the photos section.

You need to do more than just zero the Z at the first cut. Plasma cutting is one of the few processes where the top (surface) of the material changes due to warping from heat. If all you cut is 1/4" and up then it's minimal. I have watched (yesterday) 14ga warp up almost an inch along an edge. You since piercing is done at about .125 and cutting is done at .063 there is not a lot of room for variance. Get a 1/8" bow in the material from the initial reference and you get a bad pierce (or worse ruined consummables)

You need to build a torch holder that will allow you to "touch off" as often as you think necessary. SheetCAM has a post that actually keeps track of XY cut distance and will automatically insert a Z reference (touch off) before the next pierce. You can change the distance it uses so it does it more often or even every pierce.

If you have the floating head attachment (that you build) you never have to worry about setting the height. The SheetCAM post will automatically touch off before the first cut and reset Z zero.

The Arc Good is another important concept to grasp. It let's you run without having to change the pierce delay in the code for different material and tip size. If you don't have Arc Good (aka "Arc Xfr", "Okay to Move" ,etc) signals in your plasma you should get a Current Transformer with the THC300 that will provide the same function for any plasma.

There is a lot more to plasma cutting than meets the eye. It's actually harder in my estimation than doing router cutting since there are a lot more variables you have to control.

TOM CAUDLE
www.CANDCNC.COM

[Normsthename]

Thanks for the input Tom
I am already a member of the CandCNCSupport forum, I have been lurking there for quite a while!
I have a load of questions to ask, and I am compiling a list so I can ask all the questions in one go!
Most of them I am sure are very easy to answer, but they are gaps in the knowledge I need!

I have watched (yesterday) 14ga warp up almost an inch along an edge.

I am very familar with Laser machines, and I have seen 8' x 4' sheet edges lift as much as 4" when the program has not been optimized on thin sheets!

Andy