Re: Wax casting

From: Martin Koch (mkoch@calpoly.edu)
Date: Fri Sep 11 1998 - 19:30:21 EEST


S.A.D.P.Susantha wrote:
>
> Dear list,
>
> I used LOM tool (mold) to cast wax patterns for investment casting. I used
> lacquer and sand paper to polish the mold. Due to the un proper seating and
> gating system I couldn't cast the wax pattern correctly. The cavity is not
> filled by the wax completely. Is there any one has experience regarding
> that kind work. Is there another method to finish the mold? I appreciate
> your kind suggestion and the experience.
>
> Kind regards
>
> Susantha
>
> ************************************************************************
> S.A.D.P.SUSANTHA
> MAIL BOX NO 294 SCHOOL OF ADVANCED TECHNOLOGY
> ASIAN INSTITUTE OF TECHNOLOGY DIVISION OF MANUFACTURING SYSTEM
> P.O. BOX NO 4 ENGINEERING
> KLONG LUANG - 12120
> PATHUMTHANI, THAILAND
> E-MAIL: msa78492@ait.ac.th
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> **************************************************************************
>
> For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/
Susantha, John,

I think that heating the LOM tool will result in problems, especially
if there is any mositure still in the tool. If you heat the wax to a
higher
temperature it might help but could also result in greater shrinkage.
This could
be balanced by using chill balls (specially shaped wax pieces used to
reduce the
amount of molten wax need to fill a volume).

The misfill could be due to several reasons such as inproper gating
where thin sections are used to fill thick sections and are freezing off
before
enough wax is shot into the tool, or entrapped air is stopping the
filling
process.

I'm not sure what you mean by "unproper seating": are you getting a
parting line
flash from where the tool mates together?

What you might try is to cut thin bleed/vent lines from the nonfilled
areas to
allow the air to escape. These thin vents would then freeze off when
the wax gets
to them giving you small spikes of wax to be cleaned off the wax
pattern.

Also, you might try different waxes.

What temperatures, pressures and injection methods are you using?

have fun

martin

For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/



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