CAD CAM EDM DRO - Yahoo Group Archive

Re: [CAD_CAM_EDM_DRO] Re: PIC Based DRO

Posted by james owens
on 2000-04-05 15:08:55 UTC
Seeing as you have been there and done that would you release the information to the rest of us on the list or is it for sale.

Regards,

Terry.


----- Original Message -----
From: beer@...
To: CAD_CAM_EDM_DRO@egroups.com
Sent: Wednesday, April 05, 2000 8:00 PM
Subject: [CAD_CAM_EDM_DRO] Re: PIC Based DRO



>> It seems like the problem will be how to couple to everyone's shafts.
>> What would you use for a shaft encoder that would be somewhat
>> universal? There may be no way to fit full size machines as well as
>> tabletop machines.

>> Also, a shaft encoder cannot manage the backlash,
>> so your resolution will be no better than the current lash in the
>> lead screw, right?

Exactly, a shaft mounted encoder cannot measure backlash - or wear - or
misadjusted gibs - or lack or parallelism in the ways - or racking of
the table - or any of a number of other sources of positional error.

An encoder placed on the leadscrew IS a DRO, but what it is Digitally
Reading Out is NOT the POSITION of the table. What IS being read out,
even with the best of leadscrews, is the number of turns of the crank
and an APPROXIMATE table position. I guess that's better than just
counting the turns manually, but it hardly seems worth the trouble.

Capturing the actual motion of the table is a whole lot more difficult,
but also, a whole lot more useful.

A DRO is a pretty simple thing to code, for the basic functions; that
is, everything except bolt holes ) Been there, done that, works fine.

( My code, with error checking, LCD display, lathe mode, and
simultaneous absolute and incremental fits in a 1k PIC. Metric
functions run JUST over 1k, although it could probably be squeezed
into 1K too with a bit of work.)

BUT, getting ACCURATE table position information at reasonably high
resolutions is still proving troublesome.

Alan

--

Alan Rothenbush | The Spartans do not ask the number of the
Academic Computing Services | enemy, only where they are.
Simon Fraser University |
Burnaby, B.C., Canada | Agix of Sparta


------------------------------------------------------------------------------



------------------------------------------------------------------------------
Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the discussion of shop built systems in the above catagories.
To Unsubscribe, read archives, change to or from digest.
Go to: http://www.onelist.com/isregistered.cgi
Log on, and you will go to Member Center, and you can make changes there.
For the FAQ, go to http://www.ktmarketing.com/faq.html
bill,
List Manager



[Non-text portions of this message have been removed]

Discussion Thread

beer@s... 2000-04-05 11:59:59 UTC Re: PIC Based DRO jguenthe 2000-04-05 12:48:38 UTC RE: [CAD_CAM_EDM_DRO] Re: PIC Based DRO A. G. Eckstein 2000-04-05 14:42:23 UTC RE: [CAD_CAM_EDM_DRO] Re: PIC Based DRO james owens 2000-04-05 15:08:55 UTC Re: [CAD_CAM_EDM_DRO] Re: PIC Based DRO james owens 2000-04-05 15:09:04 UTC Re: [CAD_CAM_EDM_DRO] Re: PIC Based DRO ptengin@a... 2000-04-05 20:33:38 UTC Re: [CAD_CAM_EDM_DRO] Re: PIC Based DRO Tim Barnard 2000-04-05 20:38:22 UTC RE: [CAD_CAM_EDM_DRO] Re: PIC Based DRO