Low-pressure casting is a type of ______.

Explanation:

Casting:

Casting is one of the oldest manufacturing processes. It is the first step in making most of the products. A cast product or casting is produced by the pouring of molten metal into a mold where it then solidifies into a geometric shape. In other instances, molten metal is injected into a die having a cavity in the desired shape of the part.

Types of casting processes:

The three primary casting processes are:

1. Expendable mold/reusable pattern
2. Expendable mold/expendable pattern
3. Permanent mold/no pattern

1) Expendable mold/reusable pattern:

The expendable mold/reusable pattern method includes the sand mold, plaster mold, and ceramic mold casting. Sand mold casting is the most common with virtually no limit to the size of casting that can be made. Though not very precise in dimension or detail, sand mold casting is the least expensive.

2) Expendable mold/expendable pattern:

The expendable mold/expendable pattern method includes investment casting and evaporative foam casting. Investment casting is also known as the “lost-wax process” because the pattern material, wax, is consumed during the mold-making process. Some plastics may also be substituted for the more commonly used wax.

3) Permanent mold/no pattern:

Permanent mold/no pattern casting is initially very expensive in producing the mold, but such molds, machined out of metal or graphite, can be reused thousands of times.

Cores are also made of metal, but if sand is used then called semi-permanent mold casting.

Three variations of this method include

• Permanent-mold casting
• Die casting
• Centrifugal casting

The permanent mold method, because of the chilling effects of the molds, produces parts of superior mechanical properties, close tolerances, and smooth finishes. The method is well suited for casting nonferrous materials. 

Low-pressure casting:

In the earlier casting process, metal flow in the mold cavity is by gravity pull, but in low-pressure casting, liquid metal is forced into the cavity under low pressure, app. 0.1 MPa, from beneath the surface so that metal flow is upward.