Sand Casting Process

BENEFITS OF SAND CASTING

All ferrous and non ferrous alloys can be cast using the sand cast method. Aluminum, brass, bronze, carbon steel, stainless steel, and irons both gray and ductile to name a few.
Casting weight can vary from ounces to 50,000 pounds or more.
Pattern costs are the most economic compared to other casting processes. Sand casting is usually the least expensive of all casting production processes.
Quantities of parts produced can range from a prototype of one to thousands.
Surface finishes of 250 RMS.
Painting, plating, anodizing and hard coat finishes can be applied to sand castings. The finish will vary according to the cast material.
Cast letters, numbers and logos are possible with sand castings.

Sand combined with a suitable binder can be packed or rammed rigidly about a pattern. When the pattern is removed, a cavity corresponding to the shape of the part remains. The upper half of the pattern is called the cope and the bottom, the drag. Each half is formed separately then, the cope is placed on top of the drag portion. A metal jacket or flask is placed around the mold which holds the four sides in place. (This is done so the sand mold will not come apart while pouring metal into the mold.) Metal is poured into the mold and the metal fills the cavity area that represents the shape of a part. To allow for adequate solidification time of the metal, the mold will cool for 20 minutes to one hour. Following the cooling period, the sand molds are broken open to remove the part with its metal feed system, gates and risers. The parts are removed from the gating system with a band saw or cutting abrasive wheel. The cast components are then sand blasted or, a wheel-a-brater is used for cleaning them. The castings are now ready for machining and any other secondary requirements. Sand cast parts can have undercuts, formed by cores to produce intricate features. Cores can also be used to make square, round or D-holes in a casting There are several types of patterns used to produce sand castings; wood, match plate metal pattern, cast urethane resins are the most common types of patterns. The sand cast process can be used from prototypes to high volume quantities. Higher quantity parts may have multiple cavities in the mold to reduce casting costs.