Question about move time and inverse kinematics

[kmonroe023]

I work with a Pmac application that runs a 2D profile using a Cartesian gantry.

Part of the kinematic equation is an offset value that allows the operator to increase or decrease the size of the shape by the same amount on all sides, for example, to add 0.5mm to account for material ground off in a subsequent process.

The procedure itself works fine in that the part shrinks or grows as desired, but since the offset operation effectively makes arcs (circle moves) longer or shorter, I notice that the velocity increases or decreases as required to maintain the original move time.

Our application is particularly sensitive to changes in the programmed feed-rate.

Is there a way to have the Pmac recalculate the block move time after the inverse kinematic equation does its thing?

(I think I know what the answer will be, but I wanted to ask anyway...just in case).

Thanks,
Kmonroe

[curtwilson]

I'm curious as to why you are not using our 2D tool (cutter) radius compensation functionality for this. Lots of people just modify the declared radius offset value (ccr{data}) to do this. The program does not need any other changes, and the declared feedrate is maintained.

[kmonroe023]

That's a good question Curt, I don't know why we're not using it. We've done it for so long this way that I didn't even think about cutter compensation as a possible solution. I guess that's why it's good to ask questions sometimes.

I'll look into 2D cutter compensation and see if that will work for our application.

Thanks for the input.
kmonroe