How to Use Macro Variables to Cut a Corner Radius

Same part, new technique. Last week Matt covered how to cut a radius on the corner of a part using an interpolation technique (not the fastest route). Here's a new technique that will speed up the process.

Instead of interpolating the radius in the Y and Z axis and looping across the length of the part, Matt will traverse across the part and reposition in the Y and Z and traverse back to the other side, reposition and then enter a looping motion. This will allow more time to be spent cutting as opposed to travelling.

Matt is able to reconfigure the program without having to completely re write it by using global variables.

Drop any comments or questions down below in the comments section and don't forget to subscribe!

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Matt Schmelzer is the CNC instructor at Northeast Wisconsin Technical College. To learn more about the manufacturing programs at Northeast Wisconsin Technical College visit

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[brentbarnes]

Very clever program. Good to have something like that
in the arsenal.

[frankknorr]

It would be nice to see a picture of the machine control screen to see what the program looks like all typed up. Thanks for the video.

[Goff]

I have wanted to learn macros for a while. You gave a clear presentation.
Unless I am way off base, I think the Y step over should = sin (angle) * radius and Z step over = cos(angle) * radius.
If I am wrong would someone explain it to me.
Thank you.

[steelwheelsminnesota]

Not a bad idea. If I were cutting corner radii I would take this a step further and make it a G65 macro subprogram. Use the A-Z arguments to pass the data. Have it smart so it knows which direction it's cutting by the XZ or YZ center you give it. It could get it's start points by current position at call, and a letter I or J for incremental distance.
Use R for corner radius, and D for tool radius.
The radial positioning moves can be in absolute, and the feed moves in incremental.
Further, by adding the radius center point in the radial move commands, the radius can be divorced from tangency with origin surface, no need to shift offset either.
Last but not least, before doing anything log the relevant modal commands so they can be recalled when the cycle is done, making it "canned"
And if I really used it often, I would assign it a unique G code instead of using G65.