How Injection Molding Works

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The plastic injection molding process produces large numbers of parts of high quality with great accuracy, very quickly.

Plastic material in the form of granules is melted until soft enough to be injected under pressure to fill a mold. The result is that the shape is exactly copied. Once the plastic molding has cooled sufficiently to harden, the mold opens, releasing the part. The whole injection molding process then repeats.

CLAMPING:

The moving and fixed plates of the injection molding machine hold the mold tool together under pressure.

INJECTION

The molten plastic that has been melted from its pellet form in the barrel of the molding machine is injected under pressure into the mold.

DWELLING

After the molten plastic has been injected into the mold, pressure is applied to ensure that all cavities are filled.

COOLING

The plastic parts are then allowed to solidify in the mold.

OPENING

The moving plate moves away from the fixed plate, separating the mold tool.

EJECTION

Ejection of the completed plastic molding from the tool is aided by use of rods, a plate, or air blasts.

-- http://www.rutlandplastics.co.uk/advice/moulding_process.html