Part 1 – Making the Mold
In this article, we show you step by step, how to duplicate a complex pattern using Hapco’s high performance materials and equipment.
After taking measurements of the pattern and creating a drawing to outline our plan, we constructed a mold box using medium density overlay.
Orient the pattern inside the mold frame in a manner that will maximize the flow of material and minimize the amount of air that could get trapped. The paper represents cutouts that will reduce waste and save on material costs.
Pieces of cardboard were cut and layered to follow the shape and contours of the unicorn. This creates a foundation for a layer of clay that will represent the parting line for the two mold halves.
The clay is carefully smoothed out up to the halfway point to raise the part from the board and create a parting line along the middle.
Hapsil™ 360 is mixed thoroughly and degassed in an X-Vac™ Chamber to remove any trapped air before pouring.
Hapsil™ 360 is slowly poured over the pattern until it reaches the top of the mold box.
The silicone is left to cure overnight at room temperature.
Once the silicone has cured, the cardboard and clay are removed. The cured silicone mold half is temporarily removed from the frame for easier cleaning.
The pattern is temporarily removed allowing the mold to be cleaned thoroughly with isopropyl alcohol. Grease-It™ 5 release agent is also sprayed on the mold.
Once the unicorn pattern and mold are placed back in the frame, a final coat of Grease-It™ 5 is evenly applied over the surface.
Step 5 is repeated and the Hapsil™ 360 is poured evenly over the part in a thin, steady stream. It is best to pour from one side to allow the air to escape as it’s filling.
The uncured silicone is allowed to cure at room temperature overnight.
The silicone is removed from the frame and separated. Once the pattern is demolded, the silicone is cleaned thoroughly with isopropyl alcohol.
It is important to understand how the mold will be oriented and to consider where air may get trapped. Vents are carved out of one mold half to give air bubbles a path to escape.
The two mold halves are separated and placed in an oven at 125°F for 8 hrs. It is important to separate the mold halves to allow any oils or
residue to flash off.
A hole is cut where the material will be poured into. This represents the top of the mold.
The silicone rubber is completely supported by the wooden box. The two side pieces are screwed into place and the mold is rotated so that the hole is on the top. It is now ready for casting.
To learn how we cast a clear part using Ultraclear™ 480N-40, view Part 2- Casting the Unicorn.