The figure below shows the method of direct injection moulding. For running shoes this method is widely used. The granules of the sole material is directly injected onto a last upper.

The method of melting granules of sole material and harden the sole, need a feed hopper (1.), a barrel with heating bands and screw (2) and a mould (3). The mould needs to be relatively cold to ensure a good form of the sole and a good attachment onto an upper. The materials that can be used for this method are PVC, TR and TPU. Thermoplastic polyurethane (TPU ) is a hard soling material and basically used on soccer boot stud plates and ski boot shells.

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