Monday, June 10, 2013

To Mold and Cast a Rubber Ducky into a Plastic Duck using ProtoCast and ComposiCast Urethane Resin

This is a simple one part mold of a rubber duck. To stop the rubber duck from floating when the ComposiMold is poured over it, clay and sand was put inside the rubber duck. It also could have been glued down with hot glue to the bottom of the container.

The part was then coated with Bubble Buster to reduce bubbles from adhering to the part. We dip it into the Bubble Buster, but we could also have sprayed it on. Be sure to get it into any crevices.
The duck is placed inside a mold box. We used a PVC pipe, but any container that can handle a little heat will do. You can also use legos to build a box or aluminum foil that has been sprayed with a mold release also works well.

Melt the ComposiMold and pour over your part. To melt the ComposiMold, follow the direction on the label. Melt in short intervals until you are comfortable with how it melts in your microwave. You can also use a double boiler or a chocolate melter.

A toothpick or paperclip can be used to pull bubbles away from any areas where bubbles may stay such as in undercuts or sharp corners. In this case, we expect bubbles to adhere to the neck area and below the beak.

We don’t show it in this video, but the ComposiMold is cooled rapidly by placing it in the freezer. It took approximately 30 minutes to cool, but to ensure it was very cold before pouring in the urethane resin, we left the mold in the freezer for 2 hours.

You then remove the duck from the mold and spray the inside of the mold with a mold release that is designed for urethane resin.

The ProtoCast urethane resin is a bright white plastic with a demold time of 15 to 20 minutes.
While the mold is still cold, pour in a PrototCast Urethane resin. The urethane is mixed 1:1 by volume.

If necessary, place ComposiMold back into the freezer to keep the mold cold while the urethane is curing. This helps reduce any melting of the ComposiMold from the exothermic reaction from the Urethane. Longer cure time resins have less of this heat.

At this time, the plastic duck is made. You can remelt the mold to make a new mold, or you can make another casting with the ComposiMold mold.

Here we also show the plastic duck made with ComposiCast urethane resin. It works the same way. Be sure to keep the mold cool if necessary throughout the process.
  • The keys to success for a urethane casting is to use Bubble Buster when making your mold
  • Keep the ComposiMold cold throughout the process
  • Use a mold release designed for urethane resin and make sure it is completely dry.
  • And if possible, use longer cure time resin systems.

Thank you!

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