Re: cnc plasma gizmo

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Raymond Heckert" <jnr@a...>
wrote:

> Myself, I'd just make a little macro that would 'spiral-out' a

little hole

> as the arc was igniting, and use that as a 'lead-in' for each cut

that

> can't be started at the edge of the sheet. For a plasma-punch

machine that

> I operated, we'd always punch a starting hole, and start our arc on

the

> edge of that hole.
>
>

If you guys are interested on how I do it on a daily basis with cuts
that have lots of piercing then read on:

The plasma mfg's will tell you to "pierce high, cut low". Since
there are advantages using a controlled Z axis for the torch head,
especially with the THC and MACH2, you can preprogram your g-code to
move to the pierce point, strike an arc at say .2" above the work,
then lower itself down to something like .125 as the first move after
being released by the Arc Good signal. You avoid a lot of the
backsplash of molten metal that clogs the tip. If you have CAM
software that will let you do lead-ins then you can get some good
cuts.

I have started to use a specialized CAM software called SheetCAM
(www.sheetcam.com). Les is the same kind of innovator as Art and is
writing a low cost CAM program for the hobby market. It already has
a lot of special plasma options that will give you control over the
cutting functions. If I were to do a head tilt thing I would
probably build it as a solinoid operated mechanism and assign an M
code to it and make that part of my piercing proceedure. Sheetcam
supports lead-ins and will let you insert code snips in the process
list to automate virtually anything you want that can be done with g-
code.

I have setup g-code "snips" (canned g-code units) for homing X & Y,
doing a Z reference (surface touch and zero) using the floating head
design, and a material load that moves the gantry out of the way plus
many other setps I find myself repeating on jobs. My goal is to build
a load-n-go machine that does not require a skilled operator.

I have to confess that I am not totally unbiased in my approach since
the MACH2/THC project was my idea and I have been working with Les to
put features into SheetCAM that makes it plasma friendly. The entire
process has been one of trying to help develop low cost solutions for
professional plasma cutting for myself but the side benefit is that
it will be available for all you "Torchheads".