Injection-compression moulding

The injection-compression moulding process combines elements of both the injection monlding process and the compression moulding process. 

Compared with injection moulding, there is a big reduction in the filling pressnres reqnired. There is also less orientation of the material, which can improve properties and rednce anisotropy. This can be of special importance in moulding thin-walled components where dimensional stability is important, and with transparent mouldings where good optical properties are required. 

It can be seen that injection-compression is a variation of the injection moulding process. Other variations on the injeetion moulding process such as this will be discussed in Chapter 10. 

Other proeesses for thermoset and thermoplastics also exist which are not discussed here. The suggested reading at the end of this chapter provides sources of further information. 

This chapter has briefly introduced the fascinating subject of injection moulding. A comparison with the various processing methods also diseussed in this chapter is given in Table 1.1. For some components, there may be more than one suitable proeess route. The final ehoiee of process will depend on both economics and the component design. For the rest of this book however, only the injection moulding process will be discussed. 

---

Injection/compression moulding - Thermoplastics and thermosets Blow moulding - Thermoplastics Rotational moulding - Thermoplastics... 

Note The injection/compression moulding process capability maps 1, 2 and 3 are used for large parts with a major dimension greater than 50 mm typically and/or for large production volumes. Map 4 is for injection moulded parts that have a major dimension less than 150 mm and which are produced in small volumes. 

Processing LFRT or LFT injection, compression moulding, extrusion-compression, composite insert moulding... 

This process—injection compression moulding—offers other advantages besides lower clamping forces compression of the hot melt gives excellent surface finish and lower pressure at injection reduces orientation in the melt, so improving dimensional stability. The method is used currently to make compact discs of high quality from polycarbonate. 

Soft Touch with Injection Compression Moulding, Polymotive, Feb. 2003. 

During the most frequently used processing procedures i.e. injection/compression moulding, the polymer is first completely fused. That implies for PK copolymer that the B-crystalline phase first completely is destroyed, before development of any a-crystallinity due to certain annealing conditions can be expected. 

CIRTM This process allows two or more resins to be simultaneously injected into the mould. Advantages include the ability to create multi-layer and multi-resin structures. CRTM Also known as injection compression moulding, the process involves a gap between the mould surface and the fibre perform (Figure 3.10). Resin is injected into the gap and the mould closed to compress the resin into the fibre preform. This reduces the injection pressure and fill time required in RTM. 

Several other carbon products are now becoming established in the plastics industry. Weidmann Plastics Technology is manufacturing the bipolar plates for fuel cells by injection-compression moulding of thermoplastics filled with over 80% of graphite. A single fuel cell requires about a thousand bipolar plates. 

Michaeli, W. and Brockmann, C. (1977) Injection Compression Moulding - A Low Pressure Process for Manufacturing Textile-Covered Mouldings. Proceedings of the SPE Annual Technical Conference of Plastic Engineers (ANTEC), Toronto. 

Bickerton, S. and Abdullah, M. Z., 2003. ModeUing and evaluation of the filling stage of injection/compression moulding . Composites Science and Technology, 63, 1359-1375. 

Na, S., 2008. Global optimisation of mould fiUing parameters during the constant speed injection compression moulding process . Master s of Engineering thesis. University of Auckland. 

Injection- compression moulding Complex Thin walled mouldings Compression Closed... 

---