Interval injection moulding

If FEA shows that some ribs buckle, the product can be redesigned with thicker or shorter ribs. The latter can be achieved by having crossribs at closer intervals. These add to mould construction costs, but add very little to the materials costs or the process cycle time. The productivity of an injection mould for the ribbed plate will be controlled by the solidification time given by Eq. (5.4). It will be 3 s for the ribbed plate and 19 s for the 5 mm thick original design. The increase in mould productivity is usually more important than the materials saving from product mass reduction. 

Hydropneumatic receivers have the task of collecting and storing hydraulic energy, and then releasing it on demand. This type of receiver is used in conjimction with injection moulding machines with very rapid injection (with accumulator). Here, a high volume flow which can be partially accessed from the receiver is required periodically for brief intervals. The benefits in the application of a hydropneumatic receiver are in the use of relatively small pumps, drive motors and oil reservoirs. 

In this process, it is possible to work with the nozzle open at intervals. The mould material is completely injected. No material cushion is left behind. 

Basically, the process involves the injection under pressure of a predetermined quantity of heated and plasticised material into a relatively cold mould (Fig. 1). After the material solidifies it is allowed a further interval to cool... 

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