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MarkRafn1-Visitor
1-Visitor
September 11, 2008
Question

To shrink or not to shrink... (was to draft or not to draft..)

  • September 11, 2008
  • 3 replies
  • 810 views
ok, we've answered the draft or not to draft question... what about
adding the shrinkage?
tia
-mark

    3 replies

    B
    BobSchwerdlin1-Visitor
    1-Visitor
    September 11, 2008
    NEVER !

    Let the tool maker take that into account in their CAM software. That's their area of expertise.
    They can control the X,Y,Z shrinkage properly as long as they know that material being molded.

    Bob
    D
    dgschaefer21-Topaz II
    21-Topaz II
    September 11, 2008
    No. You give them the exact data you want. They are responsible fro
    the shrink factor based on the material chosen.

    Doug Schaefer
    T
    TrainStopper12-Amethyst
    12-Amethyst
    September 11, 2008
    Go wild, as long as you are ready to take responsibility for the end
    result.

    The master is not black magic, it's simply shrinkage factors.

    I have done it and it has worked out great, but make sure you understand
    the whole process and have folks you can work with.



    We have saved a decent amount on tooling by using Pro to make the
    complete drafted solid model, a CAM package to mill the master, a local
    shop to make the pattern, the foundry concentrated on the mold -
    everybody working within their areas of knowledge.

    You have to account for all the shrinkages involved in the process -
    work closely with a good foundry and a good pattern maker, let them tell
    you the shrinkages to apply.



    I modeled the part to finished dimensions, then added a Warp feature
    (easy and powerful) driven by a relation to account for the shrinkage.

    Then I made it a family table so I could have both states with minimal
    pain.



    Bear in mind the design of the part, inconsistent wall thicknesses, poor
    symmetries around the CG all have an adverse effect the end result.

    If you deal with a metal that needs tempering, have fun!

    For really complex or tight tolerance stuff, you may need more than Warp
    to account for local distortions, etc.



    The mold would be another thing entirely, and that I would not recommend
    if you wanted to get it right your first time out.



    Regards,

    Walt Weiss




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