I seem to unable to operate a simple calculator these days.
You are correct, My math was way off.
Sorry about that.
I do wonder how accurate the positioning is for a 50 foot table
and how repeatable the positioning would be after a long move.
That would still be one impressive machine.
Jim Combs (Lexington, Ky)
Jon Elson
<[EMAIL PROTECTED]
ms.com> To
Sent by: "Enhanced Machine Controller (EMC)"
emc-users-bounces <emc-users@lists.sourceforge.net>
@lists.sourceforg cc
e.net
Subject
Re: [Emc-users] DRO input?
02/01/2008 11:12
PM
Please respond to
"Enhanced Machine
Controller (EMC)"
<[EMAIL PROTECTED]
sourceforge.net>
[EMAIL PROTECTED] wrote:
>>>Yep! Wilson machine bought a 50' x 4' CMM at a Boeing auction. Got it
>>>cheap and spent a million moving it and
>>>getting it set up again. And that was only a few miles.
>>
>>Holy COW! a 50 FOOT CMM? There must only be 2 or 3 in the
>>entire US that big. (I can understand why Boeing would need
>>such a machine.)
>
>
>
> 50 foot at .0001 / Inch resolution would almost be at the limit for a 32
> bit unsigned integer! I could see some
> really strange software bugs begin to show up. (Signed vs unsigned
> integers). Would a double precision
> float handle that?
That's a good point. I vaguely seem to recall the OLD EMC(1)
overflowed the 32-bit raw encoder count into a double float.
The current version just goes to a 32-bit signed value (unless
this has been changed recently). I was wondering if that would
ever be a problem.
Hmm, calculating it, I get 50 * 12 * 10000 = 6 million, which is
not anywhere near 4 billion, or even +/- 2 billion, which is
what the numerical limits of a 32-bit integer are.
I calculate that 2^31 / ( 10000 * 12) = 17896.xxx FEET, which
sounds like it is a lot less of a problem.
Jon
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