Re: EMC and lead screw compensation

Wally wrote:

>3 more questions.
>1st do you or anyone else know what a reasonable measurement step
>would be for the leadscrew compensation file.

Wally,

"classic" leadscrew compensation uses 256 values spread evenly across
the screw. So, a 25 inch travel might have comp values every .100
Most controls "interpolate" a value(derive an assumed value) FROM the
value in the table FOR the comp, IF the desired position is NOT IN
the table of values.

>2nd, is it ok to have different step sizes in the file. Example,
>you measure every inch of the leadscrew and find a spot were it has
>greater error than the rest of the screw. Can you enter in
>measurements closer together in this region of the screw.

GOOD question. The commercial controls I have used work as described
(in my answer to #1) above. So the answer would be No. Additionally,
the factory usually sets the comp values (at mfr.) and
sez, "Leave 'em be!!!".

I have not yet used the EMC compensation (like Jon E, I NEED my
control to be reliable, so I don't jump to the newest release of EMC
as soon as it becomes available). Fred Proctor at NIST wrote
the "release notes" Ray referenced in his answer to you. Fred is a
helpful, friendly fellow who will answer your questions by email or
phone. Address/number at the NIST MEL ISD website.

>3rd question, isn't forward and reverse direction relative. How can
>we be sure we are putting the measured numbers in the correct
>direction column.

Assumed directions are specified in the .ini file(s) for each
machine. Yes, You would need to be sure these correlate.

>> It looks to me like it would not only take care of rolled screw
>>error but might take care of some variable slop (backlash) as well.
>> Ray

Sure looks that way to me, too!

Hope this helps.

Ballendo