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MANUFACTURING THE POLYPROPCHAIR - INJECTION MOULDING
 
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One reason why the Polyprop Chair can be regarded as innovative, is the use of the injection moulding process, for the manufacture of the one piece seat and back rest. This means that the chair can be mass produced relatively cheaply and with consistent quality. The most expensive aspect of the manufacture is the production of precise moulds for the injection moulding machines. However, the cost of each chair, is low due to the volume of chairs manufactured. The more chairs manufactured, the cheaper it becomes.
 
 
 

1. Granules of polypropylene are added to the hopper.

2. The granules fall on to the archimedean screw which pushes them through the heater.

3. The granules melt and become mouldable.

4. As the molten polypropylene is forced into the mould, a ‘jet’ of compressed air forces it to the outside wall of the mould, forming the body of the chair.

5. When the polypropylene cools, it can be removed from the mould.

 
 
 
SKETCHED VERSION
 
 
The sketched version above, shows a simplified sketch of the injection moulding process. In an examination you may need to sketch a diagram in similar detail. Practice sketching!
 
 
 
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