After taken out any remaining sand still attached to the casting is removed by shot blasting
Unit 22 casting and moulding
Pass 2
There are 4 different types of casting
Sand casting
Investment casting
High pressure casting
Gravity die casting
Sand Casting
A sand casting is a cast part produced by forming a mold from a sand mixture and pouring molten liquid metal into the cavity in the mold. The mold is then cooled until the metal has solidified. In the last stage the casting is separated from the mold. The process stages are:
- Place a pattern in sand to create a mold.
- Incorporate a gating system.
- Remove the pattern.
- Fill the mold cavity with molten metal.
- Allow the metal to cool.
- Break away the sand mold and remove the casting.
Investment casting
Investment casting is when beeswax formed the pattern, to today’s high-technology waxes, refractory materials and specialist alloys, the castings allow the production of components with accuracy, repeatability, versatility and integrity in a variety of metals and high-performance alloys
Unit - 22 casting and moulding
Pass 4 - describe the process of investing casting when used safely to manufacture a given component
Investment casting is an industrial process based on and also called lost wax casting, one of the oldest known metal-forming techniques.
Casts can be made of the wax model itself, the direct method; or of a wax copy of a model that need not be of wax, the indirect method. The following steps are for the indirect process, which, in total, can take two days to one week to complete.
An investment cast turbocharger turbine.
The process is generally used for small castings, but has produced complete aircraft door frames, steel castings of up to 300 kg and aluminum castings of up to 30 kg. It is generally more expensive per unit than die casting or sand casting but with lower equipment cost. It can produce complicated shapes that would be difficult or impossible with die casting, yet like that process, it requires little surface finishing and only minor machining
Produce a master pattern: An artist or mold-maker creates an original pattern from wax, clay, wood, plastic, steel, or another material.
Mold making: A mold, known as the master die, is made of the master pattern. The master pattern may be made from a low-melting-point metal, steel or wood. If a steel pattern was created then a low-melting-point metal may be cast directly from the master pattern. Rubber molds can also be cast directly from the master pattern. The first step may also be skipped if the master die is machined directly into steel.
