Re: Re: Scratch-built CNC mill

Years ago I worked at a place that machined to 50 millionths, long before
it was done any way except by grinding. It was necessary to machine and
anneal a number of times to get down to the final dimension. A longer time
had to elapse between machining passes to allow the part to reach the
control temperature as the final size was approached. Feedback was based
on the temperature of the machine so the part had to be at the machine
temperature. Correcting equations won't work well because the heat is spot
heat, not even heat.

At 07:53 PM 8/26/99 +0100, you wrote:

>From: "Ian W. Wright" <ian@...>
>
>CG wrote:
>> Why don't we just use glass scales??
>
>The question really should be - why *do* people use glass scales. Close
>contacts with a company which made precision measuring products taught
>me that the material which machine scales are made from should match
>either that of the machine itself or the material being processed. In
>this way, its not necessary to take any account of changes in
>temperature. That is - a steel scale on a steel machine will remain
>proportional at all temperatures. If you are working hard on a large
>metal part it gets hot and will consequently expand, so, logically, if
>you are relying on a scale which does not expand as much or is in a
>position where it is not affected by the heat of the work, the work will
>finish up undersize when it cools down. opinions anyone??
>
>Best wishes
>
>Ian
>
>--
>
>Ian W. Wright LBHI
>Sheffield Branch Chairman of the British Horological Institute.
>Bandmaster and Euphonium player of the Hathersage Brass Band. UK.
>See our homepage at:- http://www.iw63.freeserve.co.uk or
>http://www.iw63.demon.co.uk/ or
>http://www.GeoCities.com/Hollywood/6067/index.html
>
>'Music is the filling of regular time intervals with harmonious
>oscillations.'
>
>
>
>--------------------------- ONElist Sponsor ----------------------------
>
>ATTENTION ONElist MEMBERS! Are you getting your ONElist news?
>If not, join our MEMBER NEWSLETTER here:
><a href=" http://clickme.onelist.com/ad/newsletter1 ">Click Here</a>
>
>------------------------------------------------------------------------
>Welcome to CAD_CAM_EDM_DRO@...,an unmodulated list for the

discussion of shop built systems in the above catagories.

>To Unsubscribe, read archives, change to or from digest.
>Go to: http://www.onelist.com/isregistered.cgi
>Log on, and you will go to Member Center, and you can make changes there.
>For the FAQ, go to http://www.ktmarketing.com/faq.html
>bill,
>List Manager
>