4th Axis Slave driven by Equation?

[will_eng]

I am wondering if there is a good software for driving a stepper motor by an equation of variables provided by other motor positions.

I want to make a bevel head for a plasma cutter that will have a fixed angle of bevel but allow the head to "caster" (the 4th axis) to follow the tangency of the curve created by the x and y steeper motors.

I think this can be done by counting the steps of other motors and creating logic using another programmable controller but i am looking for a software first. I have Mach software which does do equations but its basically to scale what you are inputting.

[keebler303]

Research "tangential knife control" Mach is supposed to do it, I'm not sure how well it works.

Matt