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# Math Question : Writing Machine Macro

## Math Question : Writing Machine Macro

(OP)
I'm not sure how well versed people are here with machine process, etc. My question is basically a trigonometry problem and I will try and lay it out as easy as I can..

I am machining a part that rotates (not on center) about a fixed rotary point. I know where the machine center of rotation is . Now what I need to do is track an offset that I will set, off my part when I rotate to 25 degrees.

This needs to be able to be done mathematically (I can use sine, cos, tangent etc) functions in the machine, the thing is the part is not always in the same location.

Basically I will probe the part to find the 0 offset, then I can populate some fields, and I need to calculate the offset when it rotates 25 degrees, based on the initial offset (should be able to since I know this point obviously, and where it is relative to the point of rotation.) I am just not sure the required trig functions to do so, since the distance from the actual rotation center will change part to part...

Thanks

### RE: Math Question : Writing Machine Macro

If it is just 4 axis horizontal machine, and you wish to use the same zero point that you find on the setup position
then of course just X and Z are the calculated axis. First you would calculate where that point is in the zero tombstone face position of setup, and then you will know the Z dimension from center of rotation and X location from center point then calculate using the rotation angles for the other positions. I really thought that some of the better programming software did all that for you. Personally I'd rather be using work offsets for adjustability.

### RE: Math Question : Writing Machine Macro

Use a G92 position preset in your program and change the preset as the part moves. You may have to put a program stop at your expected preset location and indicate the part location. When I programmed the locations of rotation points and part location was known and taken into account when it was programmed. I did a great deal of programming prior to having CNC with the functionality they have today. The whole program was written and calculated manually. I even punched paper/mylar tape. I have seen programs for machines without circular interpolation (point to point) using chatter routines cutting short point to point cutting steps to cut circular sections.

Bill

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