Introduction to Micromoulding

Activities in MEMS and biomedical applications are placing increasing demands on industry for product miniaturisation. In turn, this is leading to exciting developments in materials and processing technology. Over the last decade, research has been performed to investigate injection moulding of very small components which has usually involved the adaption of conventional injection moulding equipment. Unfortunately there are a number of reasons why these machines are unsuitable for manufacture of parts below a certain shot weight: -

The plasticising screws are unsuitable for the production of micro-parts because the shot to screw volume ratio is so low that residence time of material in the screw can become a problem and may result in injection of degraded material.

The positional control of the machines does not have the resolution to accurately deliver the small melt dose required during micromoulding.

A huge percentage of the shot is wasted due to the volume of material required to fill the sprue and runners guiding the material to the cavity(ies).

Handling of very small parts is a problem when removed from the machine.

In 1998 Battenfeld released a dedicated micromoulding machine - the Microsystem50, which offered a number of innovations which addressed the problems described above. The machine is discussed in greater technical detail here.

The Microsystem has since become an industry leader for the production of micro-scale parts, able to manufacture products with incredible surface detail with masses down to less than a millgram. Other firms are now also introducing their own micromoulding machines and a lot of research is being performed to explore the limits of this technology.

Example of one of the most detailed micromoulded components - a gear wheel with a mass of 0.0008g

Micromoulding technology poses challenges to a number of different fields. Accurate process control, tool manufacture and material selection are all areas of great interest and have led to the adoption of technologies not usually seen in conventional injection moulding, such as lithographic techniques for tool making which are normally associated with the fabrication of silcon computer chips!

Recent years have seen an exponential rise in interest in the technology, particularly in the medical and micro electro-mechanical systems sectors, as industry becomes aware of the ability of to process to manufacture highly complex, 3-dimensional microscale devices in high volumes at a fraction of the cost of that using current techniques.