34 MATERIALS/PROCESSES/FINISHES
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Moulded component weights range from 0.01 g to 15 g and multi-cavity tooling can be accommodated when production volumes warrant it. If necessary, micro- injection moulded parts can be produced with inserts. In contrast to most conventional injection moulding
machines, the Babyplast plastification system uses spheres; the temperature of the plastification cylinder is homogenous and each granule of plastic is melted by contact with hot metal. In this way, the resin is not overheated by friction. Furthermore, the compact dimensions of the plastification chamber (15 cm3) ensure that the material remains at the melting temperature for only a short duration. Such measures help to ensure the material is not degraded during moulding. While the Babyplast uses hydraulics, the Battenfeld Microsystem 50 is all-electric. This machine can mould parts with single-digit milligram weights and is available with various options to extend its functionality, such as a removal and handling module and a clean room module (Fig. 1). A further module, which is of particular interest in the production of components for the electrical and electronics industries, enables inserts to be used (Fig. 2). One company that uses a Microsystem 50 is
Micro Systems (UK), which offers mould design and production, as well as micro-injection moulding and micro-machining services to the medical, pharmaceutical and optical markets. An example of the type of work the company handles is the fully automated moulding and de-gating of 2.5 mm diameter Fresnel lenses with a 6.5 s cycle time. The lenses are moulded in a four-cavity tool and have surface features that are between 450 and 910 nm deep – though Micro Systems says it can mould smaller features if required. For organisations that need to buy-in design
expertise, Micro Engineering Solutions, which is based in the USA, offers design as well as manufacturing and assembly services (Fig. 3). In addition to micro-injection
moulding plastics, the company also undertakes micro-EDM, micro-machining, ceramic injection moulding and metal injection moulding.
Laser processing
A process that has not been discussed so far is laser cutting, or laser microstructuring, as it is sometimes known. Metafab, which is part of Cardiff University in Wales, operates a dual-beam, 157 nm, 193 nm excimer and a 795 nm femtosecond laser, which is said to be particularly suitable for industrial microfluidic and photonic applications. Most commonly processed in this Xtreme Laser Facility (XLF) are PEEK, Teflon PTFE (polytetrafluoroethylene), Teflon AF (amorphous fluoropolymer), cyclic olefin copolymer (COC), fused silica and stainless steel. Other materials that benefit from the laser microstructuring technology include biodegradable polymers, quartz and sapphire, though Metafab claims that the XLF can machine any material. Metafab produces a wide variety of components for micro-electro-mechanical systems (MEMS), optics, microfluidics, micro-reactors and shadow masks (Fig. 4). Laser Micromachining Limited (LML), as its name
suggests, offers laser micro-machining services, and Dr Nadeem Rizvi, the company’s co-founder and general manager, also teaches a training course at FSRM (the Swiss Foundation for Research in Microtechnology) for engineers, managers and others interested in improving their understanding of laser micro-machining systems, techniques and applications. In addition to cutting and profiling, LML can also trim machined and pre-assembled devices without damaging adjacent components, micro-drill and micro-mill blind holes and pockets, and laser-mark micro-components or micro- mark conventional components. Based in France, Steec manufactures products for applications within analytical equipment used in particle accelerators or for taking physical measurements on a molecular level, as well as components for wave guides used to capture low-level electro-magnetic energy coming from the cosmos. Interestingly, Steec uses a Yag laser for processing thin foils, tubes and micro-tubes of 3 microns thickness with an accuracy of ±5 microns. Another service available from Steec is micro-EDM
using wire diameters of 30 to 100 microns for profiling, or spark erosion can be used for creating complex three-dimensional cavities. Steec offers a variety of technologies for micro-drilling holes from 20 microns to 3 mm in diameter: micro-EDM for diameters from 40 microns; micro-laser machining for diameters from 30 microns; conventional micro-drilling for diameters from 60 microns; and micro-punching for diameters from 20 microns. Of course, manufacturing a micro-sized component
Fig. 3. Micro Engineering Solutions offers design, manufacturing and assembly services.
only solves half the problem; assembling such components presents a challenge that is at least as hard to address. Usually the sizes involved mean that manual assembly is impossible, hence many micro-assemblies
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