After 2 coats of lacquer, it is time to try to make the mold. Our chemically bonded sand is a phenolic urethane coldbox system. In the picture below the Tinker Omega system is shown which has a supersack capacity of sand. The sand is fed by gravity to an auger where the sand is mixed with the 2 part binder contained in the drums pictured in the lower right of the image.
The mixed sand with binder is roughly about 2% binder by weight and hardens in about 10-15 minutes after mixing. Therefore, we run the sand through the system, pack it into the mold box, scrape the top surface to make it level, and set it aside until we are ready to extract the hardened sand mixture.
At the end of this time we can extract the sand by setting the mold box on some 2×4 to support the edges and rap the back of the pattern with a hammer. If everything lines up well then the sand will fall out in one piece. If there are undercuts or if the sand twists then the mold can get locked up and can be difficult to extract.
After both sand mold sides are extracted, the mold lock can finally be put to the test in the assembly. Pictured below is the two mold halves before putting them together.
Finally the mold is assembled and I’m going to let them rest because the sand is not quite set up until about 24 hours or so. By setting them on top of each other, and relaxing and dimensional changes will help them match the other side. Before we melt metal and pour, it is required to cut the spruce and gating system which I’m still considering the best size and direction to add them. We are planning to try to pour these with cast iron because of some testing we are doing on Friday this week.
Hopefully the alignment and parting line works as well as the mold assembly went today.
Dr Monroe Thoughts 