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Author Topic: arcs with a linear and rotational axis  (Read 2754 times)

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arcs with a linear and rotational axis
« on: June 01, 2016, 05:33:04 PM »
We are trying to set up a system as a tubing plasma cutter. The first set of parts that we want to do are 6"x6.5"rectangular holes with .5" radius corners in both 8" and 10" diameter tubes.

We have the system set up like a lathe. Z is our long linear axis with a C axis rotating about Z and an X axis is our radius/diameter.

Can someone please give me some direction on how to do an arc with the Z and C axes. It doesn't appear like Mach supports G07.1/G107 (cylindrical interpolation). I've considered setting up the C axis like a Y (linear axis) but then it seems that my cutting feedrates would be wrong when I switch diameters. Or am I thinking about that wrong?

Hopefully someone has some answers, we can't be the first ones to run into this.

Thank you,
Joel
Re: arcs with a linear and rotational axis
« Reply #1 on: June 01, 2016, 06:21:54 PM »
In Mach3 we used the A axis as the rotational axis.  In General Config we set the A axis as angular.  Once you do that G1 A1 would rotate the A axis 1 degree.  You're CAM software has to be capable of producing rotational code though.  The other way to do it is to move the rotational axis using linear moves, which means you have to scale the Y axis steps per unit based on the tube diameter...and when you do that, it affects you acceleration on the axis as well.

The easiest way is to set your rotational axis to angular in Mach and use a good tube CAM software, like Hypertherm's Rotary Tube Pro.  When you set the steps per unit on the rotational axis, it will be the number of steps to rotate 1 degree. 
Re: arcs with a linear and rotational axis
« Reply #2 on: June 03, 2016, 11:12:17 AM »
OK so if the C axis is angular, how does the CAM software write an arc in the Z and C axis to work with Mach? Mine outputs a G107 for that type of move.

Offline RDR

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Re: arcs with a linear and rotational axis
« Reply #3 on: June 03, 2016, 08:02:59 PM »
I don't think you can do arc codes (j, I) unless you use an x and or y letters.  Also there is a software called cncwrapper that will maybe do what you want.  

http://www.machsupport.com/wp-content/uploads/2014/05/Lathe%20GCode%20Programming.pdf

Check out page 9 with the link above
« Last Edit: June 03, 2016, 08:07:28 PM by RDR »
Re: arcs with a linear and rotational axis
« Reply #4 on: June 04, 2016, 08:14:02 AM »
Correct. If memory serves, Mach...or Mach3.... Can't do an IJ arc in rotational mode.  To do arcs you would need to treat the rotational axis as a linear axis.  To run it as a rotational axis, you would need ca, softaware capable of producing that code.  The cam software would output something like G01 X1 A1, which would move the X 1" and rotate the tube 1 degree. 

It usually takes a specialized software for working with tube.
Re: arcs with a linear and rotational axis
« Reply #5 on: June 10, 2016, 12:18:04 PM »
We have done a few plasma pipe cutter in Mach3.  The best way to do it is use the attached Mcode to re-calibrate the Steps Per Unit so that the circumference of the pipe is 1 pipe turn.  You will need to edit the Mcode and put in the number of Steps per pipe rotation.  After you set this up you will need to re-run M500 everytime you change your pipe diameter. If you do it this way you can use normal X and Y gcode like you would on the table and it will work.

Working with the pipe like it is flat is the best way, all your feeds and speeds are normal.

You can rewrite this and do the same thing in Mach4.

Thanks,
Andrew
« Last Edit: June 10, 2016, 12:28:52 PM by MachMotion Development Team »
Andrew
MachMotion
Re: arcs with a linear and rotational axis
« Reply #6 on: June 10, 2016, 12:42:22 PM »
Andrew,

This looks awesome! Do you know if this will work with Mach4?

Thanks,
Joel
Re: arcs with a linear and rotational axis
« Reply #7 on: June 10, 2016, 12:44:28 PM »
You can rewrite this and do the same thing in Mach4.

Sorry, just saw the last line.
Re: arcs with a linear and rotational axis
« Reply #8 on: June 10, 2016, 04:26:33 PM »
I'm very inexperienced with LUA, does anybody think that they would be able to rewrite this for Mach4 and post it?

Thanks!