2.2 – Mold Making: Process

Milled Mold

Material – 1.5″ foam

CNC – Shopbot

Roughing Pass: NA

Finishing Pass:

Endmill – 0.25″ Ballnose

Spindle RPM – 9000

Pass Speed – 10 inches/sec

Plunge Speed – 6 inches/sec

Step Over – 25%

Traverse: Along Y

Flexible Mold

Material – Smooth On: Mold Star 15

Mix Ratio – 1:1

Pot Life – 50 mins

Cure Time – 4 hrs

Notes:

It was necessary to cut a much large sprue because of the material’s viscosity.  Original sprue diameter was 0.25″, however, a sprue roughly the size of a square inch was more appropriate.  The amount of material necessary was not taken into account when initially designing the mold.  As a result much more Mold Star 15 was required to fill the molds.  Approximately 56 fl oz was used.  Caution when mixing large volumes of the product because the bottom portion has a tendency to require extra mixing despite what appears to be an even mixture throughout the material.

Casting

Material – Smooth On:

Mix Ratio – 1:1

Pot Life – 7 mins

Cure Time – 15mins

Notes:

Although the product’s information sheet states that the cure time was 15 mins it required at least 30 mins before it could be removed from the mold without altering the product’s shape.  Possible reasons: cooler room temperature, improper mixing of materials.