Rubber Mold Making For Investment Casting

Hosted by Bill VanOrden

November 14th, 2004

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We would like to mention our two new members, Gene Lucas and Paul Lind.  Gene is a member of the Saguaro Astronomy Club of Phoenix. Paul is also a SAC member as well as EVAC (East Valley Astronomy Club), as is the Host of the demo Bill VanOrden.  If you are interested in telescopes you might contact one these fellows.

Beevo (aka Bill VanOrden) starts out the demonstration amid boxes of doughnuts and mold making supplies.  From left to right in the image attendees are: Larry Carter, Dave Batten, Bob Harbour, Marty Escarcega, Lee Studley, Paul Lind?, Jerry Hine, Randy Sanders and Bob Sanders.  

New member Gene Lucas (grey jacket) has already been put in charge of the burnout oven's temperature meter. Dean Quackenbush assists.  A flask invested earlier in the morning is being heated in preparation for casting after the mold demo ends.  Sara Quackenbush  is asking Beevo about the molding process.  A lot of good questions were put forth by the attendees.  

On the table in front of Beevo is a home made wax injection pump made from a thrift store Fry Baby and home cast parts.  In front of the vacuum pump is the base part of the vacuum chamber that uses a Tilia Food Saver Storage container (under the table) for a bell jar.  Sitting on top of the base are 4 rubber molds that will be cut apart later in the demo.  The wax pump is all warmed up and pattern casting is being discussed in this shot.  Sitting next to the 4 rubber mold is the frame used to cast them.  Two larger frames are sitting in the foreground.  The toothpaste is there for a reason, it is used to seal the mold frames.

Cutting the rubber is being demonstrated.  The beer can opener (hard to find) is used to hold the mold while pulling it open as it is cut with the surgical knife.

Close up of the cutting process as it begins.

Farther into the cutting process.  Note the blue sprue and black part being cast starting to show inside the rubber.  The rubber is incredibly tough and can be stretched without damage.  Irregular cuts are desirable as they help locate the two halves of the mold when injecting the wax.

The part being molded, a plastic knob, now removed from the rubber molding compound.

Measuring the pink rubber molding compound in preparation of casting.  The mold frame with side plates installed is in the lower left of the image.  A scale MUST be used to measure the two parts of the rubber!

With the rubber mold part of the demo over a short silver casting demo commenced. 

Marty mans the torch while Beevo supervises...

Here the silver is being heated in the hand crucible, note the lump of silver.

The silver is getting more fluid, note the slag on the metal.  The shiny appearance of the crucible is from the borax that has bonded to the ceramic bowl.

Here the metal is almost ready to pour.  The skin of slag will be removed by putting a tiny pinch of Borax Flux into the crucible.  Note the red color of the molten metal.  The carbon rod is being used to pick out the larger parts of the slag.

The silver is ready to cast, note the very shiny look and red color.  The yellow flame is from the Borax Flux.

A handout on rubber mold making was handed out at the meeting.  You may download a copy here.

Photo credits:  Unless noted all images are courtesy of Neil Butterfield.