plasma tube coping machine

Hello!

After building a laser engraver I'm thinking about a simple plasma tube notcher. The idea is to cut notches, specific holes and shapes out of stainless round tube.

But I've got a few questions.

when using a lathe chuck, how do you program the system that it knows the diameter? 1 inch is a big difference with a 3 inch tube. For 1 project one full turn is 150 mm and the next project it is (lets say) 300 mm. That is quite a difference in cutting speed. Simply lowering the cutting speed would not work because your cutting in 2 axis, also along the tube.

Why not use a rubbercoated wheel attached to a steppingmotor and rest the piece of tubing on that wheel. Then you automatically fix the diameter problem and you could simply make a 2d dfx drawing to send to mach3.

Example: Cutting a notch or shape on a 100 mm tube? simply draw a flat CAD drawing 314 mm (diameter*pi) high and that would be 1 full turn of the tube. Just scale the coping shape to the right hight and your done. Would it be that simple? This sound to me like a easy, understandable and easy to work with system.

I hope this is understandable, my English is not bad but the technical explanation is quite difficult. If not clear, I'll make a drawing.

What do you guys think?

I was drawing and working with large tubes is difficult with a wheel, unstable etc.

So my preference would be using a lathe chuck like this:
https://www.youtube.com/watch?v=Dp0s6QqVCIk

could i use mach3 or something for this machine and how would i program it? Make a 2d dfx file and use that to create the cutpath? Thats no problem with solidworks. But how can mach work with different tube diameters?

A day later: Tought about it and is this gonna work?:

Program Mach3 as a router, count the number of passes to the stepper that rotates the tube 360 degrees. lets say 500 steps for 1 full circle.

So for a tube with a circumference of 98 mm you program mach 3 as 500 steps = 98 mm. (a full circle)

The next project with a bigger tube you program mach 3 as 500 step = 150 mm (a full circle)

Than you would just load 2d images of the cut patch an mach would "think" that is is a plasma router.

In my head this could work but I'm not hold back by anny kind of cnc mach 3 knowlegde.

Is this possible?

I would love it!

Check out Tom's stuff over at http://www.candcnc.com/ he has a rotary tube slicer program that use's mach 3....this all can be done easily!

also check this out http://www.cnczone.com/forums/plasma...r_project.html

Hello!

I've been reading and watched the mach tutorial on youtube. What a nice program btw.

By adjusting the steps per mm in the motor tuning part of Mach it would be very easy. (correct me if i'm wrong)

Once i know the number of steps for one 360 degree circle i can use excel to make a simple calculation program that gives me the right number of steps with each tube radius. Then a 2d drawing of the right size will wrap nicely around a tube.

Then again, is this correct?

As far as I know all you have to do in mach is enter tube OD and load your g-code and your off

But how does mach know what one rotation is? Do you program that first?

Ya you program how many steps under motor tuning in mach and that's it