Moulding at Mazda

As part of its efforts to reduce vehicle weight, Mazda Motor Corporation has developed a plastic moulding technique that enables the weight of plastic parts used in vehicles to be reduced.

The company claims that the manufacturing technique cuts the consumption of plastic resins used as raw material by approximately 20 to 30 per cent, with associated reductions in weight.

The most common manufacturing method for producing automobile plastic parts is injection moulding. Mazda’s improved injection moulding process involves mixing supercritical fluids (SCF) made from common inert gases such as nitrogen or carbon dioxide with the plastic resin raw material.

The process raises the fluidity of the liquid plastic resin and causes it to expand rapidly when injected into a mould. As a result, smaller amounts of raw material resin are needed to fill moulds.

Furthermore, by using a core back expansion moulding process, substantially less material is needed to manufacture plastic parts that are lighter and have equal or greater strength and rigidity characteristics compared to conventional, non-foamed parts.

In the core back process, once the foamed resin has filled up the mould, the volume of the mould is increased, causing the foam to expand. This means that larger plastic parts, with low density and good rigidity, can be made from the same volume of plastic resin.

The company says that the plastic foam moulding technology can potentially be applied to nearly all plastic parts used in vehicles.

Because the core back moulding process also enables the structure of the foam to be controlled, it is possible to enhance the heat insulation and acoustic characteristics plastic parts made using the process.

Multi-layer structure of foamed resin

Liquid resin infused with                                    After a certain period of time, the back of the mould is
the supercritical fluid                                           partially extracted (core back) to form the
foaming agent is injected                                   multi-layer structure
into a thin mould where it
expands quickly to fill the
space