Re: [CAD_CAM_EDM_DRO] Re: controller inputs

On March 6, 2007 05:07 pm, Alan KM6VV wrote:

> After a clue from Bob, I found "E-Stop/Hold Line" in CNCpro that gives
> me a clue.
>
> ". On the other hand, when used as a Hold Line, CNC Pro will temporarily
> pause program
> execution and allow for user recovery. Consider these options carefully
> when deciding on the
> purpose of this switch control. "

Doug added that feature several years ago at, I think, my request.

At that time, I was trying to "electronically eliminate lash" on my ACME lead
screws.

I programmed up a PIC (for each axis), to which was connected

a. some DRO quadrature outputs
b. the Step and Direction inputs (for one axis) from the PC
c. Step and Direction outputs to the controller

The PIC would read the step/dir inputs and echo them right back out again,
while also watching the quadrature input.

If things got too far out of sync ( a few counts), typically as a result of
backlash during a direction change, I would pause CNCPro, issue some
"phantom" steps, and when the table was where it was supposed to be, release
the line and allow CNCPro to continue.

This seemed to work as well as could be expected (given that the table was
free to move all on it's lonesome when the thread of the screw was not
contacting any part of the nut) although testing was minimal, ballscrews
arriving within days of the DRO being installed.


Alan

--
Alan Rothenbush
Academic Computing Services
Simon Fraser University
Burnaby, B.C., Canada


The Spartans do not ask the number of the enemy, only where they are.

Agix of Sparta