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Manufacture of Sand Castings

Manufacture of Sand Castings

Engineers have required metal castings for over 5000 years.

As the technical ability of man has progressed, so have the techniques for making a Sand Casting.

Before a foundry can start producing Sand Castings, a number of decisions has to be made regards the Sand Casting Process :

a ) Metal Type

b) Contraction Rate. Ex if the finished product is to be 48″ long, then the pattern / mould cavity, will be approx. 49″long

c) Quality of the finished product, ie manhole cover or Nuclear Submarine part

1)    A pattern is required; this can be made from a cheap timber for single items, or metal for very large quantities.

2)     Cores will be required, if the casting is to have any internal shape

3)    A Foundry Engineer will determine how to ensure the casting is sound.

4)    His final determination is called the Runner System / Method

5)     To form the bottom half of the Mould, sand is now compacted around the bottom half of the pattern.

6)    A joint line is made between the top and bottom half of the mould. 3 dowels or pins are used to ensure the 2 halves of the mould can be put together exactly in the correct position.

7)    Sand is then compacted around the top half of the pattern.

8)    Split the 2 halves of the mould

9)    Carefully take the Pattern out of the sand.

Place any Cores in the mould.

10)   The top and bottom half moulds are clamped or  weighted down

leaving a cavity inside the mould

11) Molten metal is poured down the runner until the mould is full.

12) When cool the casting can be taken out of the mould

For further information on Sand Castings Tolerances please visit jade-trading.com

Introduction for Sand Casting Process with Philip White and Jenny Dunseath in the foundry at Camberwell college of Art London. Video by Chris Follows part of the Process Arts Project – process.arts.ac.uk NOTE: Because the sand is used in a damp condition there is minimal sand dust,and this occurs at the mould face immediately arround the hot metal casting ,clearly visible when the casting is knocked out. At this stage a small watering can or spray will help to stableize this dry material.A standard dust mask could be worn.It is always worth taking sensible precautions with all processes.With sand casting on the scale immagined here keep a water spray handy and use it when cleanig away any dry material. Text Information supplied by Jenny Dunseath: Pattern Making: The Pattern is a full size model of the part that makes an impression in the sand mold, with dimensional allocation for shrinkage and finishing. If the casting is hollow, additional patterns called cores are used to create these cavities in the finished product. Patterns are usually made of wood, plastic, metal, or plaster; however, other materials or combinations of materials are used if there are additional specific properties required of the pattern. Every Pattern must have a draft angle of approximately 2° – 3° to all walls parallel to the parting direction to facilitate removing the part from the mold. Paint the surface of the Pattern with Varnish or Shellac to make it water tight and to ensure that the sand …
Video Rating: 4 / 5

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