Re: [CAD_CAM_EDM_DRO] Re: 3D Contouring - Loss of Accuracy - Follow-Up

Hi Fred,

Your suggestion is one that only quite recently occurred to me, too. I
normally run in mm and usually run with 3 decimal places which gives me
0.001mm or 0.00004" resolution. I did try with 6 decimal places and
unfortunately got exactly the same error result. I agree with you
completely - experience often shows the problem is lurking somewhere
where we're not always looking. I'm totally open to suggestions and
constructive criticism if they help the cause.

I did spend quite a bit of time on the phone today with Art Volta at
Ability Systems (Indexer LPT/G-Code Controller) and he very patiently
went through a checklist of questions - and gave me some homework - some
additional tests for me to run. In his experience and based on my
description etc. he still suspects that it could either be noise related
or an incorrect or marginal timing problem in the step & direction
lines. Over the next couple of days, I will implement his suggested
circuit mods and see what happens. Be assured I will report my findings
- good or bad.

Cheers, Peter


Fred Smith wrote:

>--- In CAD_CAM_EDM_DRO@yahoogroups.com, Peter <prenolds@s...> wrote:
>
>>Hi Fred,
>>
>>I haven't backplotted the file because I'm posting files using G90 -
>>
>
>
>>absolute mode. But I'll send a file over just to be sure. Thx.
>>
>
>Boy do I wish we could view this thread all as a single conversation
>instead of all spread out. ;-)
>
>I got your file. It's about 20,000 lines of code. Can you process
>the program at 5 decimals in stead of 4? Do you get the same error
>at the end of the run?
>
>My thought is that instead of a control system problem, it may be a
>simple problem of truncating instead of rounding. Running an extra
>decimal might improve the result. If I missed that you already tried
>this, let me know & I will crawl back into my cave with the other
>bears. Something else you might try, if the controller won't run
>more than 4 decimals, scale the CNC file by 10 times and descale it
>in the controller. If the post processor is truncating, but the
>controller is not, you should see an improvement in accuracy with
>this method.
>
>This kind of problem along with the mechanical are the ones that we
>never expect and it is very easy to start problem solving by looking
>for an electronic or system software problem first and waste a lot of
>time trying to solve the wrong problem. This is the voice of
>experience, not the voice of criticism, having solved the wrong
>problems many times myself.
>
>Best regards and good luck,
>
>Fred Smith - IMService
>
>Names:26-27 April, 2003 Southgate, MI, USA CUthere
>
>
>Addresses:
>FAQ: http://www.ktmarketing.com/faq.html
>FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
>Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com
>
>Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
>Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
>List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
>Moderator: jmelson@... timg@... [Moderator]
>URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
>
>OFF Topic POSTS: General Machining
>If you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble.
>http://www.metalworking.com/news_servers.html
>
>http://groups.yahoo.com/group/jobshophomeshop I consider this to be a sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list.
>
>NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
>bill
>List Mom
>List Owner
>
>
>
>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>