Monday, February 7, 2011

rotational moulding -1

Definition: When finely ground powders (Usually thermoplstics) are heated in a rotating mould until it is melted or fused, the molten resin will form a uniform coating or lining on the inner surface of the mould, which when allowed to cool, is removed as a finished part.
1. The tooling required is usually very simple and relatively inexpensive.
2. The process is well suited for making very large and/or very complex parts with single or double walls.
3. Strain free parts are produced.
4. Parts with square corners are thicker at corners.
5. Parts are usually made with very uniform wall thickness except at the square corners.
6. The parts re free of weld lines, sprue marks, ejection marks etc.
7. Very little or no scrap is produced.
8. Hollow parts are easily produced with simple tooling.
9. Usually no secondary operations are required.
10. Changes in wall thickness can be easily made without employing new tooling or modification of the starting raw material.
11. Relatively unskilled labours can be employed.
1. Material costs are relatively high because most materials are produced as pallets and then reduced to fine powder.
2. The process is not suitable for production of parts with wall thickness less than 0.03”.
3. Large production runs of small parts are not suitable.
Rotoforming offers a different technique for producing large complex plastic parts. It is well suited for prototype production of large parts like boats (length up to 12ft. approximately), missile containers, gasoline tanks, toys, artificial flowers, water tanks.

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