Casting Competition: Sand Castings vs. Permanent Mold Castings

Sand castings or permanent mold castings? Since we offer both casting processes here at Hengchang Foundry, we often get posed this question. What is the difference between these two casting processes and which one is better suited for your application? Let’s clear up the casting confusion with a cursory overview.

Sand Castings: A one-time sand mold is produced, which may contain one or more impressions of the part. Molten metal is poured into the sand mold, then following solidification and cooling, the sand is broken away and the casting is removed. In most cases, the sand is recycled and reused. So when is sand casting the appropriate method? When the production is suited for low and high volumes, the process is driven by material and mechanical casting property requirements, only moderate surface finishes and dimensional tolerances are needed, low tooling costs are needed, and when size and configurations dictate that the part can only be made as a sand casting. There are additional considerations that may have to be taken into account, and it is recommended that the user consult with the foundry prior to finalizing part design.

Permanent Mold Castings: Unlike a sand casting, the mold is made from cast iron or steel, allowing for one or more cavities depending on the geometry of the part. The process is best suited for mid to higher volumes, when the part configuration dictates this type of casting, or the process is best suited for the application of the casting. The molds are in, most cases, fully CNC machined with the parting surfaces aligned with a locking system that provides good repeatable casting dimension conditions. When compared to sand castings, permanent mold castings have improved surface finishes, less machining allowances required, and closer net shaped profiles which are made possible by the metal mold configurations. Unlike sand castings, however, permanent mold castings are limited in size and the tooling proves to be more expensive (though part price tends to be lower!). Again, consult with a foundry to determine the right process for your needs!

Do you better understand the difference between sand castings and permanent mold castings? Have you decided which is better for your specific applications? See our website for more information on.