Subject: Re: Foam patterns?

From: [email-masked] (Patton M Turner)
Date: Sun, 15 Jan 1995 21:15:50 GMT

[email-masked] (BrnzCaster) writes:

>1. Thoroughly vent the cope and drag or the mold may explode during
>pour.

Thats why EPC (Lost Foam) is done with unbonded sand.

>2. Pour with a full-choke or you'll have a flame thrower shooting
>out of the sprue.
Industrial EPC relies on the peramability of the pattern coating to 
control pour rate, even so a few will blow back.  I used to have a real 
problem getting people to pour R&D buckets, until I started standing 
right next to them (wearing full safety gear of course).

>3. Have LOTS of ventilation ... toxic fumes.
Yes, there is styrene gas Co, CO2, benzene and a lot of other pyrolysis 
products.

>I use a sodium silicate-carbon dioxide system for making my cores.
>I now use this sand binder when working with expendable foam patterns.
>I make the foam pattern as a split-pattern. After "investing" the
>foam in the hardened sand, I part the flask halves and dig out most
>of the foam. Surface finish of the castings is greatly improved and
>I don't have to deal with the vaporized foam problems as much.

We used sodium silicate and sand to seal arround pouring basins back when 
we used a EPS sprue.  Latter we switched to a cermaic sprue and pouring 
basin.

Pat