Casting is a 7,000-year-old process. There are many types of casting and the oldest surviving casting is a copper frog from 3200 BC. The process of casting is one that foundries use to manufacture differently shaped parts that are needed for a variety of reasons.
When casting, the liquid material is poured into molds that contain a cavity or negative space in the shape of the part the foundry has been tasked to create. The mold is then set aside allowing the material to cool and solidify. The solidified part is the casting. The casting is then broken out of the mold and, voila… the part is made.
What materials are used in casting?
Usually metals or various materials that meld together (cure) after mixing two or more materials together. Some of those include concrete, clay, plaster, and epoxy. Complex or difficult shapes to make can be made more economically by using casting methods.
Are there different types of casting processes?
Yes. The different types of casting processes. Here are three common casting types:
– Investment casting
– Sand casting
5000 years ago, Investment casting used beeswax to create the patterns that were needed. This is one of the oldest casting processes and today high technology waxes, refractory materials, and specialist alloys are used to create these castings for greater accuracy, versatility, and integrity.
The name, Investment casting, comes from the fact that the pattern is invested, or surrounded, with a refractory material. The wax can be reused in investment casting, so this process makes it easier to repeat production.
This is generally used for small intricate castings and is generally more expensive than die or sand casting but can be useful when casting intricate contours and can be used to cast near perfect shapes requiring little or no reworking once cast.
Applications: turbine blades, armament parts, pipe fittings, lock parts, hand tools, jewelry
Permanent mold casting:
When creating permanent mold castings, steel cavities are coated with a refractory wash of acetylene soot before processing to allow easy removal of the casting. Permanent molds will eventually wear out and require either refinishing or replacement, however, these parts generally show a 20% increase in tensile strength and 30% increase in elongation as compared to the products of sand casting.
Permanent mold casting is generally used when forming iron, aluminum, magnesium, and copper-based alloys and is a highly automated process.
Applications: gears, wheels, engine components, and housings
Sand casting has been used for centuries and is one of the most popular and simplest types of casting processes. Sand casting allows for smaller batches to be made compared to permanent mold casting and often at more reasonable costs. Another benefit to sand casting is the fact that there are little to no size limitations. Castings can be so small that they fit in the palm of your hand or can accommodate large parts needed for many applications. Sand casting also allows for most metals to be cast depending on the type of sand used for the molds. Materials for sand casting generally include – aluminum, carbon steel, copper alloys, gray/ductile/ malleable iron.
When creating molds with sand casting, the sand is bonded together using clays, as in green sand, polymerized oils like motor oil, or chemical binders. Another bonus is that sand can be recycled many times in most operations sand casting requires little additional input.
Sand casting is unsurpassed for large-part production but can require a lead time of days for production at high output rates (1-20 pieces/hr-mold). Green, moist sand has almost no part weight limit, but dry sand has a practical part mass limit of 2300-2700 kg. The minimum part weight ranges from 0.075-0.1 kg.
Applications: Smaller sand cast parts include gears, pulleys, crankshafts, connecting rods, and propellers. Larger applications include housings for large equipment and heavy machine bases. Sand casting is also common in producing automobile components, such as engine blocks, engine manifolds, cylinder heads, and transmission cases.
When seeking a foundry to cast parts for your next project, consider Faircast Inc. Our engineers will work with you to determine the best path to fulfilling your needs.