Re: question of RP accuracy

From: Steve_Farentinos (
Date: Wed Aug 13 1997 - 03:01:19 EEST

Michael Raphael wrote:

> We are going to embark on a some accuracy testing and would like to get any
> response on recommendations for procedures, methods, etc. on the
> measurement and analysis techniques, preferably specifics. Our desire is
> that the test methods be statistically valid. I suspect (hope) that there
> are some web-accessable repositories of such information, possibly previous
> test data, results, methods, etc. If you could point me such a direction
> or provide any information to help us we would be grateful. Our desire is
> to continue existing research and to publish our results for the benefit of
> the RP community.


I look forward to seeing the results of you study. Our company started out as
a dimensional inspection service bureau and we have been measuring RP parts
for about 6 years. In that time, I can't think of a single instance where a
part met all the dimensional specifications of the RP machine manufacturer.
Some parts come very close, but these tend to be "test" parts that were built
under carefully controlled conditions and sometimes built several times to
achieve the best possible results. In a production environment, this is not

It is understandable that manufacturers tend to exaggerate the dimensional
capabilities of their equipment in order to sell machines. But I believe the
record needs to be set straight. There are many people out there who have
purchased equipment based on manufacturer's spec's. and been disappointed by
machine accuracy. It would be nice to know what these machines are capable of
under the best possible conditions and also under "real world" conditions.


Steve Farentinos
PML, Inc.
201 W. Beach Ave.
Inglewood, CA  90302
310 671-4345
310 671-0858 Fax
310 671-1862 BBS

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