The open/close mould got its name from its easy movement and function when the  injection mould for machining of the plastic parts is clamped onto an injection  moulding machine. The injection mould or the injection moulding machine opens  and closes without any further necessary movement taking place in the injection  mould. The entire motion sequence is called an injection cycle or just cycle. It begins with  a closing of the injection mould. When it is closed, a liquid, hot plastic mass is  injected into the injection mould under pressure. Now a certain amount of time  must pass before the liquid plastic has cooled and solidified and the plastic part in  the injection mould reaches a certain stability. The injection mould opens and the  finished, still-warm plastic parts are ejected from the injection mould. When all of  the movements are finished, the process starts again. For the outside observer, the  machine opens and closes again and again. The direction in which the injection mould or the injection moulding machine  opens and closes is called the main demoulding direction. All movements of  the injection moulding machine, the injection moulds and the moving parts in the  injection mould run in this axial direction. Depending on the component there can  be additional demoulding directions. This is described in Section 2.2. The open/close mould is the simplest of all injection moulds. As a result it is often  the cheapest. Already in the planning and designing of plastic parts, efforts are  made so that the plastic piece can be produced with this type of injection mould. Figure 2.1 shows the demoulding direction of a simple open/close mould. Both  upper part (fixed half) and lower part (moving half) open and close in an axial  direction. The plastic part has been designed for being produced with this specific  mould in such a way that when opening the mould on the injection moulding  machine it is not damaged or destroyed.

Figure 2.1 Demoulding direction

The plastic parts which are to be produced with such an injection mould have no  structural elements which deviate from the main demoulding direction. Cupshaped or flat parts, for example, are manufactured with this type of mould. A plastic part can have elements such as side openings, latches and clips, laterally protruding edges or pipes. For the demoulding of these elements, moving  components—called slides or inserts—are designed for the mould. In a secondary  demoulding direction, these elements called undercuts can be removed from the  mould without damage. More on this in Section 2.2. The previously mentioned “expanding” parts container and cover is shown in Figure 2.2 to illustrate how such plastic parts produced in an open/close mould can  look. Here already is the first addition to container and cover. To connect the two and be  able to close the container, a sleeve is introduced in every corner of the container  and, aligning to the sleeve, a stepped bore is introduced in the cover. Now you can  screw down the cover on the container with four screws. Both the size of the injection mould as well as the open and close technique do not  change despite these additions to the plastic parts. The additional elements are  also in the demoulding direction.

Figure 2.2 Parts for an open/close mould

In Figure 2.3, the additional sleeves in the container and the stepped bores in the  cover are shown. The demoulding direction remains the same.

The upper part (fixed half) and the lower part (moving half) are made up of several  plates and risers. Via the integrated guides, that is, bolts in the fixed half and the  bushes in the moving half, the mould closes precisely. The fixed half consists of the clamping plate and the cavity plate. The guide bolts  are installed in the cavity plate. The guide bolts are provided at the back end with  a collar, which is embedded in the cavity plate. Against the slip out of the guide  bolts the clamping plate is screwed tightly with the cavity plate. The cavity plate is  fixed to the mould plate via another fitting diameter at the guide bolt. The moving half of a classic open/close mould is made up of the mould plate,  possibly a backing plate, the risers and the lower cavity plate. The ejector set is  between the risers. The guide bushes are also provided with a collar here and  mounted in the cavity plate. They are secured in the moving half through the  risers, which are attached, like the fixed half, via the back fitting diameter of the  guide bush. The risers are again installed with the clamping plate and with the  additional guide sleeves. Everything is screwed tightly together with long screws  from the clamping plate through to the mould plate. This guarantees that all components are aligned and tightly connected. Ejectors are the moving parts in the  injection mould that eject or expel the plastic part after opening the mould. Ejectors are usually round pins which are installed in the ejector set. The small rings  mentioned at the beginning which are usually visible on the plastic part are the  imprints of these ejectors. In Figure 2.4 several longitudinal and cross sections through an injection mould  are represented so that the classic structure of an open/close mould can be seen.