1) Size, it is said isn’t everything, and that is certainly true in the case of the latest developments in injection moulding. The emerging micro moulding is taking injection moulding technology down to a new scale and a new level of intricacy and accuracy that has simply not been possible until now. Parts weighing no more than a few thousandths of a gram and with details measuring only a few microns thick are being to be produced commercially by companies pioneering the new technology. This ‘next big thing’ in injection moulding needs a microscope for closer inspection.

But what exactly are micro-mouldings? How does the new technology differ from making very small or ‘mini’ injection mouldings? It is not just a case of scaling everything down. You have to look at everything from scratch, including tooling, moulding materials, as well as parts handling and inspection equipment.’ In other words micro moulding should be seen as a specialist technique in its own right, with a different set of challenges to standard injection moulding. Micro moulding is a separate entity.

2) The most obvious difference between micro moulding and injection moulding is the size of the components and the accuracy with which they are produced. a system has a maximum shot volume of approximately one cubic centimetre of plastic and can produce components weighing as little as 0.0008g with dimensional tolerances of as little as a few microns. The system is specifically designed to work with such a small amount of material, offering for example a large reduction in sprue weight. Tool design is another area in which micromoulding has its own set of demands. Part of the investment programme is to re-equip the toolroom to make moulds for micromoulding,We still need to understand the concepts of toolmaking for micromoulding and have appointed a specific tool designer to become a specialist in this area.

Another important area of production in making micromouldings is the inspection and handling of he finished components. Errors that might be spotted with the naked eye on regular injection mouldings can easily go undetected on micromouldings, such as a missing tooth on a gear wheel. Careful handling of micromouldings is also important to prevent the miniature details of the parts jamming or linking together when packaged. Now the system can overcome this problem with an automatic handling system that deposits individual parts, each oriented in the same direction, in a kind of blister pack roll. This could then be used for automatic delivery of parts during downstream assembly.

At first glance, the material used for micro mouldings might seem like the least significant part of the technology, with processing, tooling and inspection all more specific to this new field. Certainly the cost of the material is insignificant, given the amount used. The maximum shot on the machine is 1cc, so a 25kg bag of plastic goes an awful long way, For this reason, we use mainly relatively expensive engineering polymers such as LCPs, PPS, PS and so on at the moment.

There are no commodity polymers being used, There are lots of good thermoplastics around that produce very good regular products. The company hasn’t experienced any problems with the plastics, it has used so far. That’s not to say that micro mouldings couldn’t throw up some problems owing to their small size. There aren’t any specifications or data sheets available for materials when used in components with the tiny dimensions of micromouldings, and it might be that the physical properties of the plastics are somewhat different.

3) The tiny quantities of material used in micro mouldings also raises another conundrum for this new branch of injection moulding – how do you determine the price? You can’t use a quick rule-of-thumb anymore,such as doubling the weight of material in the component to get the selling price. For a start, tooling costs are disproportionately high for the size of the mould being produced, simply owing to the specialist expertise involved in making them.

Micro moulding is still obviously very much in its infancy as a new branch of injection moulding. It will take a while for designers, manufacturers and users to cotton on to the benefits and capabilities of the technology. It will also take a while for new tooling methods to be developed, which could both bring down the costs involved and also expand the range of possible component shapes and sizes.