Convert X axis to A axis?

Hi everyone,

I have a 4 axis engraver/router and I want to engrave my logo on a piece of tubing. I have successfully done that by swapping the X and A axis wires and changing the setup. What I would really like to do is to change the G code to support the A axis. I tried simple edits but that didn't work at all. I am guessing 2 things: 1) that the wrong coordinate system is selected and that's why linuxcnc is unhappy, and 2) several people have solved this in a much better way than I can.

If anyone has any pointers on how I might get unstuck on this, I would appreciate hearing about it.

Thanks,
Chuck Tilbury

There are several ways of dealing with that, depending on your setup, but some of the easier and usable solutions is to make another config for your machine and just change the output pins from X to A axis, so when you need normal machine start the normal config, when you need the rotary just start the other config. The best thing is : it takes all of 5 seconds to switch from one to another ! the bad thing is you have to always calculate the radius of the part you are using so you the dimensions for the X and ultimately for A axis. Example: you have a bottle with a 10 cm diameter so that is 314 mm of surface that you can use for whatever.
The other way of doing it is editing gcode and changing X with A in it, again easy and works and same math.
You can also configure the rotary as a rotary ( available in the stepconf wizard), but you would need a 4 axis CAM software to do the math, since rotary axis use degrees not mm.
I always use the first option, at least until i need some actual 4 axis stuff.

I tried just changing all of the X's to A's, but I get errors in the I's and J's. I have attached an example file that I want to cut on a piece of tube.


I switch between round and flat fairly often. I am a pretty fair hand with Python, so I could write a post processor pretty easily if I could find out what is really needed to do it. There is a bunch of other stuff I want to do on round tubing, such as cut accurate holes in it.

Forgot to mention, changing the X to A axis in gcode will not work for radii, just straight lines.
That was the main reason i do not use it, but i could not remember at the time of post. I make another config and in it i change the X with A axis, so i do not have to do anything to gcode. Linuxcnc thinks it is a linear joint and works it's magic, the only magic i have to do is calculate the radius ( actual length of the surface of the round object ) during drawing.
Give it a try, you'll be surprised at how simple and easy it is.
Regards

Ya, That's how I do it now. I tune the radius by specifying the "lead screw pitch" in the config. It does work very well.

I would still like to know how to post-process for stuff like this. I suspect that it's simple with no math. Or maybe I just don't understand. Either way I would like to know.

nononononooooooo !!! :laugh: :laugh:


Nothing like it, just make another SAME config, and just change the output pins for X and A axis.