Re: Question about angular and linear feedrates

What the control really requires is the relative position of the zero
point to the centre of rotation of the A-axis so it can calculate the
actual coordinates and distances travelled by the toolpoint for all
subsequent movements.
If the zero point is directly above the centre of rotation and almost
touching the work surface of a cylynder then that of course is the
radius. I've termed this Initial Tool Offset around A-axis (ITOA) to
hopefully save confusion unless anyone has a better term.
I assume that the zero point for 4-axis work is normally set at or
above the centre of rotation of the A-axis. Is it likely that the
zero point would ever be offset in the Y-axis ?

> If you have to do this in the CAD or postprocessor stage, you will

have feedrates

> varying in each block. I don't know whether any particular CNC

control program

> will give smooth motion when the feedrate is going up and down with

every block.

>
> Jon

Jon,

I've only tested this approach with Mach1 which works well, I'd be
interested in how it works out with other contollers.

Rab