> Send Emc-users mailing list submissions to > emc-users@lists.sourceforge.net > > To subscribe or unsubscribe via the World Wide Web, visit > https://lists.sourceforge.net/lists/listinfo/emc-users > or, via email, send a message with subject or body 'help' to > [EMAIL PROTECTED] > > You can reach the person managing the list at > [EMAIL PROTECTED] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Emc-users digest..." > > > Today's Topics: > > 1. Re: DRO input? (John Thornton) > 2. Re: Emc-users DRO input? (Kirk Wallace) > 3. Re: DRO input? (Jon Elson) > 4. Re: DRO Input? (Jon Elson) > 5. Re: DRO Input? (Jon Elson) > 6. Re: DRO Input? (Jon Elson) > 7. Re: DRO input? ([EMAIL PROTECTED]) > 8. Re: DRO Input? (Anders Blix) > 9. Re: DRO Input? (Kirk Wallace) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Fri, 01 Feb 2008 06:24:24 -0600 > From: "John Thornton" <[EMAIL PROTECTED]> > Subject: Re: [Emc-users] DRO input?
> > That would depend on the accuracy of your scales... .00004" precision > (.001mm)is > not cheap... > > In my case mine are not nearly that accurate... > > I guess it depends on how much accuracy is needed and the future of the > machine. > > EMC does have screw mapping... The cheapo (relatively) DRO I'm looking at is accurate to 0.005 mm / 0.00019" which is good enough to be getting into the realms of temperature compensation for thermal expansion of the work. I accept the comments about DROs generally not liking "rapids", but it has to be said "rapid" is a relative term, the rapid on my mill isn't going to be that rapid. I accept the points about home made DRO with the chinese non glass scales, just not robust enough, scale reader wise, against contaminants, and just not accurate enough, for what I want. I also accept the comments about modern NC servo systems never being at rest, this is a "feature" that I would always program out, WAIT 100 style, in g-code, I understand the benefits of this in a cut throat commercial production environment, but again, my mill won't be operating in one, so adding a whole 0.5 seconds here and there isn't going to have any downsides and will have plenty of upsides. I also accept the comments such as those above about screw mapping, but again, this is all adding an extra layer of fudge tables, whereas the DRO is measuring ACTUAL X Y Z positions. I also have to convert my mill to NC, it is currently all manual. SO it looks like (please comment) the story so far is... a/ DRO (with pukka glass scales) is a huge boon to any manual mill. b/ A DRO could almost pay for itself in calibrating the screw etc mapping in emc, both initial set up and then monthly re-calibration, unless of course your time is valueless. c/ A DRO beats EMC as a fake dro ONLY, sans servo/steppers, see point b/ re time. d/ a DRO can enhance the functionality of EMC considerably, injecting trustworthy positioning data into EMC to re-calibrate screw etc mapping on the fly. e/ For NC then EMC is obviously the answer, since EMC is likely to be part of a DIY installation, a DRO makes making all those NC conversion parts that much easier and faster... the rule of thumb is between 50% for simple parts and 90% for complex parts, for time setting up vs actual making chips time, see point b/ re time again. f/ A DRO + EMC / NC system means redundancy, *lots* of things have to go wrong before you're knocked back to a pure manual machine. g/ So the trick here is getting that electronic feedback loop, either from the DRO or from the glass scales themselves, into EMC, lacking that electronic feedback loop, putting operator pauses into the gcode of a dual system still allows periodic operator visual checking of agreement on position. h/ lacking a DRO, the answer is to retrofit my machine with precision ballscrews and to scrape the ways etc, a prospect that will take about ten time the time of fitting a DRO and cost at least five times as much in money. i/ I guess this is going to come down to a philosophical choice, do you pursue the DRO first, or the EMC + NC first? vi vs emacs anyone? cheers ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
