Advice on Patternmaking & Sandcasting

[BoxsterGT]

This may be OT but its for a 911 so I will ask.

Is there anyone out there familiar with patternmaking and sandcasting?

I want to have some aluminum parts cast at a local foundry. They are for a 911 project and if it works out I would likely offer it to the Porsche community.

Each time I go there to ask questions they seem to come up with additional or hidden costs not originally quoted.

I need some advice.

Please reply by email.

Thanks in advance for your help.

Len at autosportengineering dot com

[tctnd]

These are both pretty specialized skills that have long, long histories involving both art and science. You might have better luck just googling the topics to see what comes up but if you want top quality there is no substitute for the the help of a professional with a lot of experience.
regards,
Phil

[aadrew10]

If it's a small part and not too complicated I'll machine it for you for free.

- Andrew

[cashflyer]

My personal suggestion is to speak with Pat Tafta of Tafta Inc in Donalds SC.
Pat does some low volume casting, usually willing to share his wisdom, and is a VW fanatic. (Google his name)

Pat@Taftainc.com



IIRC, the mold has to be slightly oversized in all areas due to the aluminum contracting as it cools.

The thickness of each area will affect the amount of contraction in those areas, so making the mold involves a lot of math, skill, and art. The mold is usually a large expense and must be amortized over a large volume of parts to be cost effective.

[Flieger]

You can use strategically placed "risers" that are reserved of metal to account for cooling shrinkage. The gating system must be engineered so that these are the last places to cool.

A cool technique is "lost foam". You make a pattern for the part and gating system out of foam, coat it with some special, permiable refractory coating, and stick the whole thing in sand. Then pour the metal right into the foam. It is much quicker than lost wax and does not need so much special equipment for the sand mold making since the sand is just loose and supporting the shell around the foam. You can make much more intricate details that way, too.

[BoxsterGT]

Thanks guys.

I am looking into getting it scanned onto a 3D drawing at a local Technical school.

Then its back to the foundry for more quotes.

Its a lot more difficult than first thought.

Len

[ghost1001]

Can you post a drawing or sketch...there may be a better/cheaper process for you prototype...3d printing comes to mind, or do you have a proto/sample?…very hard to cost without.

I have a background in product development….usually once you have a 100% accurate, physical prototype, the costing/production issues will be much easier to address.
Also, others may have suggestions for fabrication once we have an idea of the part.

Kevin