Re: Real-Time measurement

Lee,

You are asking how to get and maintain accuracy quickly, easily, and
inexpensively... (pick any two? <G>)

This is the touchstone of everyone in the metalworking industry. The
adaptive machining efforts I posted about recently is one area where
the idea is being worked on. Suffice to say if the metalworking
machinery industry is any indicator, we are not quite there yet. At
least not at anything remotely near "home shop" levels...

One thing which WOULD help the home shop crowd, IMO; is a truly
inexpensive source of LINEAR encoders. At Westec I spent some time
looking at the cutaway model of the spherosyn and microsyn variety.
Ever since I first saw these years back, they seem to me to be the
most "home shop" possible. I've mentioned them here before. They are
based on precision ball bearings in a tube. I asked a few questions
which made the rep look at me funny<G>

Hey Elliot B, what would be the "sag" of a .032 wall aluminum (6061)
tube, .250 ID, 96 inces long, filled with .250 diameter steel ball
bearings? How about 72 inches long? What about .375 balls and an
appropriate tube? Same lengths. (If you want to, of course) TIA

Hope this helps,

Ballendo

P.S. Doug (or Tim?) presented an idea that seemed interesting awhile
back. It used the measurement of a "string" fastened to the spindle.
It unwound from an encoder, AIRC. Although intended for setup and
checking rather than in-process measurement; its use with a few
(3?) "strings" might be worth some investigation? (for in-process
tho', I'm not sure this would be much better than simply using rotary
encoders) Of course the orig. idea was NOT for in-process, but for
machine setup/verification; where the measurement TO the spindle
WOULD reduce some types of errors; whilst introducing others... Hey,
if it were simple we'd all already be doing it!

--- In CAD_CAM_EDM_DRO@y..., "Lee Wenger" <wenger2k@y...> wrote:
> I like tossing out an idea every now and then so I can get battered
and
> bruised by the list members :) I guess I just like the abuse.
>
> So here is the idea or really more of a question.
>
> Is there any (Cost Effective?) way to measure the current location
of the
> cutter? By this I'm thinking of something like a laser based
triangulated
> 3d location sensing system that could very accurately determine the
location
> of the machine (and or the cutter). A system based on this concept
could
> accurately adjust for inaccuracies in the location in real-time.
It seems
> that an incredible amount of time and effort is put into building
machines
> that have the precision built in at the component level, but as
several
> others have pointed out this is something of a pipe dream as the
machines
> will automatically lose accuracy as they wear and subtle
differences like
> air pressure and temperature can effect both the machines as well
as the
> material being cut. This real time measurement seems much more
feasible and
> would allow you to build machines of substantially lower cost parts
but
> still have the accuracy of a far more expensive machine. Can this
be done?
>
> thks,
>
> lw
>
>
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