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Regulation of Injection Process

The design purpose of injection process regulation is to make these negative influences ineffective, and thus to attain an even higher reproducibility of the parts.

The dicisive factor for all quality features that are concerned with dimension and weight is the internal pressure of the mould. Constant maintenance of this pressure curve in every cycle guarantees uniformity of the quality of injection moulded parts. If the mould internal pressure curve is maintained at a constant, all of the negative factors mentioned above are compensated.

During plastic injection moulding without injection process regulation, a specified pressure curve is established for injection and holding pressure, which can also be maintained with assurance with a regulated machine. However, the mould internal pressure curve that arises can only be assumed. Pressure losses through the runner manifold as well as the mould specific filling behavior cannot be identified.

With the application of injection process regulation, the mould internal pressure is first measured and compared with a nominal value. If there is a deviation, a hydraulic valve that applies pressure to the injection cylinder is actuated. It is thus possible to follow the nominal value precisely and independently of negative factors. The switch over from injection to holding pressure also occurs as a function of internal pressure. Thus, no pressure spikes can occur since the switch over takes place when a specified threshold value is reached.


Major Purposes of Injection Mould Tools

An injection mould tool has two major purposes:

1. It is the cavity into which the molten plastic is injected.

2. The surface of the tool acts as a heat exchanger, as the injected material solidifies with contact.

Injection mould designs differ depending on the type of material and component being moulded. Mould tool design and component design are equally important considerations for success. Component design is beyond the scope of this book but the various tooling, gating, temperature control and ejection systems that make up the mould tool will be considered here. After parts are injection moulded they must be ejected. A variety of mechanisms can be employed such as ejector pins, sleeves, plates or rings.

injection mould
injection mould