The Sand Casting Process

In this casting process a  pattern is made in the shape of the desired part. This pattern is made out wood, plastic or metal. Simple designs can be made in a single piece or solid pattern. More complex designs are made in two parts, called split patterns. A split pattern has a top or upper section, called a cope, and a bottom or lower section called a drag. Both solid and split patterns can have cores inserted to complete the final part shape. Where the cope and drag separates is called the parting line. When making a pattern it is best to taper the edges so that the pattern can be removed without breaking the mold.

The patterns are then packed in sand with a binder, which helps to harden the sand into a semi-permanent shape. Once the Sand mold is cured, the pattern is removed leaving a hollow space in the sand in the shape of the desired part. The pattern is intentionally made larger than the cast part to allow for shrinkage during cooling. Sand cores can then be inserted in the mold to create holes and improve the casting's net shape. Simple patterns are normally open on top and melted metal poured into them. Two piece molds are clamped together and melted metal is then poured in to an opening, called a gate. If necessary, vent holes will be created to allow hot gases to to escape during the pour. The pouring temperature of the metal should be a few hundred degrees higher than the melting point to assure good fluidity, thereby avoiding prematurely cooling, which will cause voids and porosity. When the metal cools, the sand mold is removed and the metal part is ready for secondary operations, such as machining & plating. Sand casting is the least expensive of all of the casting processes.

    * Sand Castings
          o Suitable for all types of alloy and applications.
          o For small or large production runs
          o Produces small and large castings...up to 500 lbs.
          o Fast turnaround times.
          o Design changes usually easy to make during production.
          o Material cost are relatively low.
          o Stable wall thicknesses greater than 0.125.

            SAND CASTING ADVANTAGES

            *Least Expensive Casting Process

            *Castings can be up to Several Tons

            *Less Expensive than Machining Shapes from Bar Stock

            *Can Cast Intricate Shapes

            *Can be Used with Most Pourable Metals and Alloys

            To view Machining Considerations for Castings Click HERE.

             
    * Permanent Mold Castings
          o Ideal for high volume runs with consistent repeatability.
          o Makes sound castings with excellent mechanical properties
          o Excellent density, detail and dimensional accuracy.
          o Suitable for castings up to 80 lbs..
          o For close tolerance castings with high metallurgical properties.
          o Dimensionally stable to .060 wall thickness.
          o Castings for a wide range of industries.

            
    * Precision Dry Sand Castings
          o Reproduces intricate detail.
          o Dimensional accuracy piece after piece
          o Stable over long production runs.
          o Excellent metallurgical integrity...a high X-ray premium casting
          o Dimensionally stable to 0.100" wall thickness.
          o For all types of commercial, automotive and aerospace applications.