Re: [CAD_CAM_EDM_DRO] HPGL ...

Hi Tom,

Sorry for the delay. Since there were so many layered questions
and responses and broken lines, I'll try to start fresh.

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So there isn't a group called torchheads, you must have meant
the torchheads in the group. Now I get it.

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The problems in Corel aren't all Corel's fault. The standards
for DXF (and EPS) are so loose and loosly adhered to that it's
got to be awful to figure out how to parse a generic file
created by another program. But the basic geometry in Corel is
flawed, so I don't think I'd what to use it where accuracy is
important.

The path closing and dupliction problems you mentioned are
infuriating, but sometimes you can trick it into playing nice by
filling the objects with a color, and then seeing if one or the
other is usable after it's imported into Corel. Oh, and this is
because Corel turns the path and the fill into two separate
objects. And they're not always built the same.

But here's a basic trick. In Corel (at least in V.8), create a
circle that's a specific size. Rotate it 40 degrees. Check the
size again. It seems to have shrunk by about .4 percent? Now
I'll grant you that it's not much to worry about given plasma's
inherent inaccuracies, but it just makes me distrust the whole
thing. I have a sneaking suspicion that both the minor
inaccuracies and the weird path duplication problems are due to
one thing: that Corel mostly cares about drawing on paper, not
producing unified paths.

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Please elaborate on "proper grounding, isolation and modern
electronics". I've tried lots of schemes which all turned out to
be useless when I have copper going straight from the motors to
the bus. The table is earth grounded, but nothing fancy.

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It's really good to hear that you're running without trouble on
the Xylotex hardware. I've asked numerous vendors about plasma
noise, and I didn't get any promising feedback. I'm tired of
pulling my hair out that there isn't enough left anyway.

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You mention a fast computer. Is this because the steps are
generated from software? I haven't tried anything speedier than
a souped-up 486, partly because it wasn't necessary for DOS, and
partly because I was worried about the plasma noise issues and
more modern hardware.

Are there timing issues to worry about under Windows? There's
also the issue that being a blacksmith, there are lots of big
hammers in my shop. Big hammers, pricy computer, Windows. Could
get expensive if I don't watch myself. ;)

I've dabbled with EMC, and it looks promising. But I'm not sure
I'm enough of an ubergeek to run it day to day.

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I'm very interested to see your THC circuit. Not having one
frequently causes trouble with uneven sheet. If I can solve the
noise issue, I might play with the spark gap and see if I can
get a little more length out of my machine (an ESAB 875). I saw
a demonstrated CNC machine that used a Hypertherm (I think)
torch which they fired at about 3/8" to save on nozzle wear and
then dropped down to keep cutting. It would be really sweet to
combine that idea with a floating torch.

Is there any other way to see the design? M5 hasn't approved my
membership yet. Maybe I should have been a little less flip
about the "why do you want to join" question. It does seem
pretty odd though.

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You mentioned Rhino in passing. I'll admit that it's not as easy
as 2d, but it's about as easy as it gets. It has a nicely
configurable DXF export and opens almost anything. And a great
free demo. Even if you've run out the demo, you can always print
to file and import the result. But the most interesting thing is
that it can extract the 2d faces of a faceted object; even faces
that are curved (in one direction). I tried writing up one
project a year or so back at:
www.casaforge.com/gallery/the_big_roof/construction_story/

I managed to draw an object in Rhino in 2 hours (never having
used it before) that I couldn't draw in AutoCad in a week. And
extracting the faces was another 2K plugin.

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And to drag this back to the starting point, sort of... I've
never really had any trouble with getting HPGL into the
Microkinetics software (aside from using a floppy disk in a
filthy environment). I like the extremely basic HPGL that Corel
spits out. You can just look at the file and figure out what's
going on. And if you use a decent text editor, it's simple
enough to edit. Even doing things like duplicating objects and
generating code automatically is about as straighforward as it
could be, in almost any scripting language. You can keep
accuracy to about .001", and even more if you cheat.

Hal Eckhart - Casa Forge - Minneapolis MN - http://www.casaforge.com