# Thread: co-ordinate rotation on a tombstone?

1. ## co-ordinate rotation on a tombstone?

I need a macro to rotate the co-ordinate system as I rotate a tombstone on a 4th axis vmc. I thought it would be farly straightforward but now I,m ready to throw nyself down the stairs!! I did'nt take into account quite what was involved, if the part is not exactly over the center of rotation this affects the output and how in the world do I deal with negative rotational positions?

2. K&T Gemini controls had an "implied offset" where you could pick up the offset at one index position & the control would compensate X, Y, and Z as the B indexed.
I have yet to see this option available on another control.
You could probably do it with a macro depending on what control you have. I know Kurt does this on their vise bodies as I had to incorporate the macro calls into the programs I wrote for them. Frankly I thought it was huge waste of time as the bodies were all machined on dedicated fixtures and the macro does NOT compensate for machine geometry error.

3. you need to set your macro to use the offset position of the x and z from the center of rotation , program header is the best place to add these variables ,
eg:
o00023
#101= 1.025 (Y offset A0)
#102= -.5 (Z distance between tool probe and part z zero @ A0)
#103= 0 (ANGLE)
#120= -2.525 (SHIFT FROM TOOL PROBE T0 Z0 AT A0 center of rotation)

#103= 90. (rotation)
M97 P8989 (macro sub call)
G52 X-6. Y#109 Z#110
g0 a#103
main program
if your qualifying tools from the top of the part then scratch the toolprobe and set z variable(eg #102) as the distance from the center of rotation
,then you'll need to do some addition , subtraction and a bit of trig in your macro in order to calculate the new rotated position , its not too bad once you get your head wrapped around it

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