Re: Fwd: RP versus CNC

From: Tom Mueller (
Date: Mon Feb 22 1999 - 06:46:29 EET

I think that the CNC machined parts were supplied by Light Machines and were
machined on one of their tabletop CNC systems. The parts were measured by
Dupont on their CMM system. It would be very interesting to see how the accuracy
of a part machined on a high end CNC machine would compare.

The old timers like Elaine and I will remember that Dupont would measure the
test part developed by the SLA user group free of charge and would periodically
report the results(provided the owner of the part allowed the results to be
shared). By providing an unbiased measurement service and a standard
measurement technique, Ed Garguilo and Dupont provided an extremely valuable
service to the RP community and were the only unbiased source of accuracy
information available. Further, the attention focused on the topic by Paul
Jacobs while he was at 3D Systems did a lot to improve accuracy throughout the

Unfortunately, both Ed and Paul are in different positions, and the division of
Dupont that owned the CMM machine has since been sold. It is no longer possible
to have SLA user group parts measured accurately at no charge, nor is there
anyone collecting information on accuracy in the way that Ed did in the past.
To my recollection, the only accuracy data published in the last few years was a
paper I presented last year at the RPA conference.

I think it is increasingly important that accuracy studies continue. As RP
moves into more demanding applications, in particular rapid tooling, the
viability of the application becomes increasingly dependent on the accuracy of
RP systems used. I believe it is important that unbiased information be
available to the RP community.

I would suggest that one or more universities active in the RP community might
like to step up and fill the role played by Dupont in the past. Providing free
measurement of standard test parts and periodically presenting results could be
extremely valuable.

Tom Mueller
TJ Mueller & Company
2314 Magnolia Court East
Buffalo Grove, IL 60089
(847) 821-8809
(847) 821-1634 fax

Elaine Hunt wrote:

> >Several different RP systems have been used to make the standard user
> >part. Has anyone made this part with a CNC machine and measured the
> >results against the STL file to determine the accuracy of the NC machine
> >on on absolute basis and relative to several RP processes?
> I believe that Ed Garguilo's report included an CNC'ed user part out of
> Aluminum. I'll hunt around for the paper and see if I can find it. The
> initial study was WAY back in the early 90s and using the ole 5180 stuff.
> This study has not been repeated using any of the newer resins. As far as
> relative to several RP processes... the standard user part was 9.5x9.5x 1.5
> so it would not fit in some machines..also I think that maybe 2 machines
> were commercial when the first report was done. Heavens do I feel old.
> Elaine
> *******************************************************************
> Opinions, suggestions, and other controversial matter VOID where prohibited.
> ******************************************************************
> Elaine T. Hunt, Director
> Clemson University Laboratory to Advance Industrial Prototyping
> 206 Fluor Daniel Bldg. Clemson, SC 29643-0925
> 864-656-0321 (voice) 864-656-4435 (fax)
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