Two-plate mould

Standard SMC moulding equipment is used by Bifort Engineering to mould the cab panels. That is, large platen area hydraulic presses, with heated platens, and simple two-plate moulds. 

A stripper mould is very similar to the standard two-plate mould except for the ejection system. This design has a stripper plate for ejection, whereas the standard one has pins or sleeve as the ejectors. This is illustrated in Figure 4.2. The advantage of a stripper plate is the increased surface area for ejection that it offers. 

Like the two previous designs, this is also a two-plate mould. However it has slides and earn pins for additional lateral movement as shown in Figure 4.3. This type of design is suitable for produeing parts with undereuts or external threads. 

Multi-plate moulds are usually more expensive than two-plate moulds and can be slower in production if an operator has to remove the sprue and runner system when the mould is open. This can usually be avoided by providing automatic ejection of sprue and runner. The distance travelled by the plates is governed by the length of the chain or the length of the bolts used to separate them. 

The choice of runner section is also infinenced by the question of whether positive ejection of the ruimer system is possible. In simple two-plate moulds this generally does not pose any problems. 

The one-impression mould was made by Penton Tools Ltd of High Wycombe (part of the Guinness group). It is a conventional two-plate injection mould incorporating a side core to produce the front sliding cover channel. The mould was made from mild steel with hardened-steel cavity inserts. 

The design standard for injection mould tools is the two-plate design. 

Table 2,1 provides some information on the two polymers that are supposed to be free of chemical crosslinks. Phenoxy PKHJ is a product of Union Carbide Corporation. Plates were produced by injection moulding after drying of the granulate. On the other hand, polymer E was prepared by casting as were the other experimental polymers but without adding PGCBA to the mixture. 

An injection machine can be equipped with a two-sided shuttle table using either 1 or 2 complete moulds. Applications are in production using a common top mould plate and two identical lower plates. Products with metal inserts or which require unloading and mould cleaning times as long as cure times are best suited to this process. 

For applications requiring two different compounds, such as a double hardness sealing ring or a two colour rubber shoe sole, some machines have two injection units. One injects into the bottom/centre mould plate and the other into the parting line. Two injection units on a singlestation vertical press are used in combination with twin rotating cavity plates. 

Composites containing 0-50 vol% glass were prepared by milling at 170°C for 15 min on an open two-roll mill and compression moulding at 190°C into 3 mm thick plates. The cooling rate was approximately 40°C/min. The samples were stored at room temperature for several years before the measurements. 

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