RE: [CAD_CAM_EDM_DRO] Positioning

> made to measure less than that. Yes, even under a micron (and mostly

> electronics, btw).
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> If you have a source for their inaccuracy (apart from your rather fertile
> imagination) let's see it. 0.04mm? Hah.
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> Capacitive scales have two drawbacks - they're affected by oil & crud

> have slow-ish data rates (50 readings per second?). Doesn't stop people
> using them though. The 'jitter' people find with those scales is power
> supply problems, usually caused when powered from a DRO rather than
> battery.
> Or RF, but that happens to everything.
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> If you bothered to calculate the thermal coefficient of your 600mm screw,
> you'd find for every degree (Celcius) change in temperature it will expand
> by that micron you claim to machine all of your parts to (including those
> "high-precision" spanners you were going to make - your funniest

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> Unless you have a temperature controlled room (to a degree!) AND are
> keeping
> every part of your machine at that temperature, your parts are not the

> you imagine they are. And don't forget your scales are change shape at a
> different rate. Oh, and of course your screws are liquid cooled as well.
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> Sure, add scales. In theory they should tell you where everything thing is
> (you believe the brochure?), in practice close enough. I realise that's
> unsuitable for the fantasy-land you do your machining in, but anyway.
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> Machines with backlash shake themselves apart? Lol.
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> You really should do some machining one day, you might learn something.
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> Tony
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> From: CAD_CAM_EDM_DRO@yahoogroups.com
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com]
> Sent: Tuesday, 3 June 2014 6:10 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] Positioning
>
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> The specs on the screw accuracy are irrelevant.
> What IS relevant is that there be no slop, as a machine with

> ie glass scales, will shake itself to pieces is it has backlash.
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> Thats why you cannot use the crap chinese scales, because they are off, ie
> inaccurate, by upto 0.00" or 0.04 mm, in short distance, and the

> varies.
> So using such, would make the machine jitter (sometimes, in some places).
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> This causing back-and forth motion, upto hundreds of times a second,
> depending on how fast the secondary positoning error-correction mechanism
> is.
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> It is impossible to make a (working) secondary-feedback mechanism if you
> have backlash in the system.
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>
> Tony..
> Unlike some people here, I try to be factual and polite.
> Grin.
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> Re: screw accuracy.
> Everything is inaccurate. Its just a question of how much.
> One good part about glass scales, is that they are usually accurate (to 1
> micron, or down to 0.01 micron with some Mori Seiki machines).
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> Sure, when you read the specs on the average screw, and that "Dummies

> To Fantasy Machining" you've got.
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> Do you know what a drunken thread is?
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> Do you know what a temperature coefficient is? (Go work out the expansion

> a 600mm steel screw for a 1 degree delta.)
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> Tony
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> (You and your microns, lol)
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> --
> -hanermo (cnc designs)
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> [Non-text portions of this message have been removed]
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> ------------------------------------
> Posted by: "Tony Smith" <ajsmith1968@...>
> ------------------------------------
>
>
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> OFF Topic POSTS: General Machining
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> ------------------------------------
> Posted by: "Christopher Erickson"

> ------------------------------------
>
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>
> 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

> you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a

> 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
>
> Yahoo Groups Links
>
>
>