What's that Lassie? You say that David Billington fell down the old
rec.crafts.metalworking mine and will die if we don't mount a rescue
by Tue, 09 Dec 2008 00:18:26 +0000:

dan wrote:
What's that Lassie? You say that Joseph Gwinn fell down the old
rec.crafts.metalworking mine and will die if we don't mount a rescue
by Mon, 08 Dec 2008 11:03:32 -0500:


That gets displacement error signals for X and Y, but provides no
motion in the direction of the line, only correction for offsets
perpendicular to it.

I think there must be some means for maintaining set speed in a
direction parallel to the line. This could be done with a form of
difference engine, or it might use more straighforward computation of
Vx^2 + Vy^2 and Vy/Vx. The difference engine might require a start
at known speed and known direction. Could have been analog or
digital. Microprocessors have been around since the mid-'70's, CNC
since the late '50s, and electronic, mechanical and even pneumatic
ways of doing such computations have been known since World War II.

You are right that the above mechanism would not move unless propelled
somehow.

As others have mentioned, the operator sets up and starts the cut. The
controller is programmed to move at a constant linear speed, and the
servo keeps the head on the line as the curve is followed.

Joe Gwinn


I can live with the idea of the rotating head to track the line, with
the four cell arraignment to move the axes in the right direction.

I'm almost tempted to try to cobble one up. But I don't think I could
make one that could do more than prove the concept.

I think I might keep an eye out on e-bay.

Thanks all for your replies

Maybe this type of thing would be simpler to cobble up
http://www.lowbucktools.com/flamecut.html

I saw that, and did consider it. But the kerf of my plasma cutter is
so narrow that it would need to have a magnetic spindle that is .060
dia. Or make the patterns undersize. Not worth the effort for 1-2
pieces.

I may make a space frame style arm that can be attached to the table
of one of the milling centers(cnc) at work. It would hold the torch
out side of the enclosure, over a scrap barrel. I wouldn't be able to
tie in to the control to start/stop the cutter, but that's OK.

Or could I. There is an interface for a Hass rotary table. I could
use that to press a switch and start cutting. Hmmm.




--

Dan H.