Re: [CAD_CAM_EDM_DRO] Re: EMC Contouring Settings/ downloading BDI

Art Fenerty wrote:

> Hi Jon:
>
> The specification may say what it wants, but it is not unusual to have
> some people useing A to drive a linear rod or actuator or some such thing.
> It may be rare, but CNC is growing so fast that the way its being used is
> changing. It just didn't seem right to me, that the planner could allow an
> axis A move to be pulses at that rate. The software should do a square sum
> as Dave says, otherwise the A axis feedrate has to be factored into the
> small X axis move as a percentage of that axis's move. Try to do the G0X .1
> A 180 move under EMC and I suspect you'll get a servo fault or lost pulses
> unless the feedrate is very low on the X axis. This should at least be
> autocorrecting to the maximum frequency of the A axis just in case.

The problem is the trajectory planner actually computes feedrate at the
cutting surface, and it has no way to know that when a rotary axis is
added. A definite deficiency. So, I guess it assumed that the A axis
was always at a radius zero, therefore it could move at max speed
(or maybe infinite speed) and still be OK. It gets VERY tricky when
cutter radius compensation is on, because the feedrate is based on the
moving tangent where the tool touches the work, not the centerline
of the tool, which is easier to compute.

Jon