Re: [CAD_CAM_EDM_DRO] EMC and rotary axis

vavaroutsos wrote:

>I have heard some rumors that EMC had/has some problems with rotary
>axis operation. Can anyone confirm that this is or isn't the case?
>
>

The problem that I am aware of is that the feedrate of the rotary axis
is computed as if it was user units (inches or mm) instead of being
left out of the calculation or processed assuming some radius.

So, if you program a 360 degree move, and the feedrate is 10 IPM, it
will take 36 minutes to make one full turn! On the other hand,
if it didn't make some assumption of possible feedrates, it could ask
the rotary axis to move faster than it was capable of. The later
BDI releases now have a separate max velocity for each axis, which is
a first step in solving the problem.

My personal preference (which was overruled) was to infer a radius in
the following manner. Say that this is an A axis - that will be parallel
to the X axis. Assume that Y=0, Z=0 puts the tool tip on the center
of the rotary axis. If Y=1, Z=1, then the radius is now 1.414, and
we can actually calculate the feedrates of all axes to deliver the
toolpath feed rate specified.

There is another way to do this, which is inverse feedrate, where you
specify the time required to complete the move. You do this with the
G93 command. I'm told this works. I still don't have a rotary axis
on my machine.

Jon