The surface finish of a casting will vary greatly depending on the process being used. An investment cast part will yield about a 125 μinch RMS surface, a die cast part about a 64 μinch RMS surface while a sand casting will be around 500 μinch RMS.
The surface finish will be modified in areas where a gate or riser has been removed. This can be a broken area where the gate was snapped off or a ground/cut surface where the gate was removed.
The surface finish in all casting processes can be modified through out the part by shot or bead blasting if needed but adds cost to the final part.
Parameters Affecting Sealing: