Shell molding casting

Shell molding is also similar to sand molding except that a mixture of sand and 3-6% resin holds the grains together. Shell molding also uses sand with a much smaller grain than green-sand. Set-up and production of shell mold patterns takes weeks, after which an output of 5-50 pieces/hr-mold is attainable. Aluminium and magnesium products average about 13.5 kg as a normal limit, but it is possible to cast items in the 45-90 kg range. Shell mold walling varies from 3-10 mm thick, depending on the forming time of the resin.
Shell molding is used for small parts that require high precision. Some examples include gear housings, cylinder heads and connecting rods. It is also used to make high-precision molding cores. This process makes it so complex parts can be cast with less labor.
There are a dozen different stages in shell mold processing that include:
Initially preparing a metal-matched plate Mixing resin and sand Heating pattern, usually to between 505-550 K Inverting the pattern (the sand is at one end of a box and the pattern at the other, and the box is inverted for a time determined by the desired thickness of the mill) Curing shell and baking it Removing investment Inserting cores Repeating for other half Assembling mold Pouring mold Removing casting Cleaning and trimming. The sand-resin mix can be recycled by burning off the resin at high temperatures.