RE: [CAD_CAM_EDM_DRO] Re: controller inputs

If someone else wants to follow this Alan, you need to tell them the DRO
signal is from a linear slide mounted on the table. NOT the lead screw
encoder.

Otherwise someone is going to try and add it to their screw encoder, and the
get upset when they look at the prices of linear scales.

Yours is a crude active methods that works, what's really good is it
corrects for both directions correctly. Software anti backlash control needs
to know whether you are climb or conventional milling, since compensation is
require at the start of the stroke with one, and end of stroke with the
other since it sucks the work under the cutter. You method closes the loop
to take care of this.



Dr. Mark Vaughan Ph'D. B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd, reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
Phone/Fax 44 1872 561288

RSGB DRM111(Cornwall)

_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Alan Rothenbush
Sent: 22 March 2007 00:54
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: 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





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