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Investment casting of complex shapes

  1. Nov 22, 2016 #1
    Hi guys,

    I am learning about investment casting at the moment and have a question I would love someone to answer.

    In investment casting a wax pattern needs to be created. How would that be made for a complex shape like an impeller? I've heard that lots of impellers are created using investment casting but can't work out how an impeller pattern could be economically (both time and money) in wax.

    Could anyone shed some light on it?

  2. jcsd
  3. Nov 22, 2016 #2


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    Complex wax patterns were traditionally made from separate components melt welded together .

    Individual components would be made in moulds . Usually metal moulds for precision engineering work and rubber moulds for lower precision and ornamental work .

    In case of an impellor advantage would be taken of the radial symmetry of the design and the separate components would be made identical so only one or a small number of moulds would be needed .

    In modern times complex patterns are often 3D printed in one piece .
    Last edited: Nov 22, 2016
  4. Nov 22, 2016 #3

    Hi Nidum,

    Thanks for your reply! That's very helpful. For the 3D printing of patterns, would that not give a fairly poor surface finish which would need to be smoothed before casting? Also what sort of materials are used in printing? Do people print patterns in wax?

    Thanks very much
  5. Nov 22, 2016 #4
    There is a huge range of quality in 3D printing - and they do make wax filament for exactly this purpose. Still - for high quality finish the critical dimensions are probably machined. Impellers and also be sintered metal or forged - depending on the application.

    Funny story - I had a client when I was in robotics that had a foundry. The owner could not use email, but his foundry was using robots - old ones that needed cool, clean air for the robot controllers. He had this foundry air conditioned to keep the robots runnng- cracked me up every time I went there,....
  6. Nov 22, 2016 #5


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  7. Nov 25, 2016 #6


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    For each casting made, a wax model must be destroyed.
    The wax models can be injection molded in a many-part mold that can be quickly cooled.
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