Re: Plasma tube notcher

>
> From: Joe Vicars <jvicars@...>
>
> What I call the R-theta tubing notcher is more accurately described
> as a rotary x-y plasma cutter. The machine control thinks it is
> controlling a regular x-y coordinate system except that x is really the
> circumference of a cylinder.
> This machine was designed to make tubular space frames like race car
> chassis and such. Using a solid modeling package (Solid Edge in this
> case) You can make intersecting cuts of almost any shape (as long as
> one of them is a cylinder). Then you can "unfold" the curve and tell
> the machine to cut in x-y coordinates.
> A company in texas makes a machine that does the same thing as mine
> except it costs about 10 grand and doesn't have bar feed. Check out
>
> http://www.cypressweld.com/saddle.htm
>
>
> One of the serious challenges I have faced is the ability to chuck
> different size tube. Right now I have bushings of different I.D.'s to
> accommodate different diameter tubes, and a different config. file in
> the controller (note that steps per inch changes with tube diameter)
> You will see from the above web site that a chuck with a 4" thru
> hole is a monster. I tried collets but ran into the same thru hole
> problem. 5C is limited to about 1", and larger collets are very costly,
> and hard to come by.
> I would like to build a chuck as is found in new pipe threading
> machines. Run forward and it tightens, reverse, loosens. Can anyone
> give me insight as to how these chucks are designed?

A machine like this, is another one of many unstarted projects.

Why "Chuck" it at all?

I figured a couple of sets of rollers the pipe sat on/between with
idler/hold-down rollers on top would do it, and easily accept many
different sizes of pipe.

Ugly ASCII Art: O <-hold-down
O <-pipe
O O <-rollers

This presumes 2 things the pipe is straight and that it is not fixed,
as in already welded to something else.

This is also presumed with the other system.

If this is not the case you could always build the system with the
rollers close together, and of light enough materials to allow the
machine to clamp on and rotate around the pipe instead.


Aren't there standard formulas for most pipe intersection
configurations?

Marc