Re: Improved Accuracy Tools

Date: Wed Apr 14 1999 - 21:49:31 EEST


Why not go one step further?

The mold was designed to make a plastic part, right? The mold design
involved several assumptions about shrinkage, etc. (and these assumptions
are only nominally correct.)

Why not prototype,
Build the tool,
Mold parts,
Measure the parts,
Correct the CAD file,
and iterate.

We did some work with this concept for soft foam tooling in a vaccuum
bagging application.



>-- [ From: Al Hastbacka * EMC.Ver #2.5.3 ] --
>When making injection molding tools, one of Sanders customers has found
>a way to improve on the very high accuracy of the Sanders Model Maker II
>(best accuracy of the commercially available US RP systems).
>This is how it was done..
>1. Fabricate the tool pattern on the ModelMaker II
>2.Send it to NDM for fabrication of the tool
>3. Measure the resulting tool
>4. Resize the CAD file to compensate for the measured errors
>5. Fabricate the second tool pattern on the ModelMaker II keeping all of
>the configuration files as they were in step 1.
>6. Send the second tool pattern to NDM for fabricating the tool in
>stainless steel
>7. Measure the second version of the tool
>The measurements of the second tool were found to track within 1/2 to
>one mil of the original CAD file.
>Al Hastbacka
>For more information about the rp-ml, see

Charles L. Thomas
Assistant Professor
Department of Mechanical Engineering
University of Utah
50 South Central Campus Drive
Salt Lake City, Utah 84112
FAX (801) 585-9826

For more information about the rp-ml, see

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