MICRO MOULDING | NEWS
AFTER SMALL AND MINI, Silicone Now Goes Micro
<< Figure 1: A 1-cent piece is much bigger than a micro moulding part from starlim//sterner. >>
innovation — the micro injection moulding. T
By 1838, it was discovered that apart from the basic nickel plating, the surface was also reproduced extremely accurately. This was how electroforming came into being and it found an increasing number of uses in the replication of complex and micro structured surfaces.
This consists of micro components weighing less than 10 mg, which are manufactured in serial production quality using a special injection moulding machine. Indeed, the micro moulding of LSR components constitutes a new development.
With the naked eye it is almost impossible to recognise the fact that a part with dimensions of just a few millimeters has high- precision recesses or undercuts that are identical to those familiar from large components. What is more, such micro components, which are used for example in watches, electrical micro housings, insulin pumps, hearing aids and other medical devices, can even be produced using two-component technology, either in thermoplastic LSR, or in an LSR-LSR combination.
Micro moulding is known in the branch and thermoplastic parts with micro structured surfaces, micro precision moulded parts with tolerances in the micrometer range, as well as injection moulded, mass produced micro components with a minimal weight of 10 mg, are already being manufactured. However, silicone components are subject to other laws and starlim//sterner is reportedly the first company to have succeeded in producing LSR micro components with a weight of less than 10 mg in large runs. In addition, all the LSR hardness degrees from 20-80 Shore-A can be employed.
he starlim//sterner Group, which is based in Marchtrenk, Austria, leads the way with regard to the processing of liquid silicone, as impressively demonstrated by its latest
The limits of physical production have been exceeded
As Project Manager, Roland Pirsic, explained: “It is no easy task to manufacture such small parts on an injection moulding machine and in the final analysis it was necessary to go beyond the physical limits to production, as in this case scaling from large to small was impossible.” Nonetheless, starlim//sterner has succeeded as a result of both its enormous experience in the production of LSR injection moulded parts and almost 40 years of in-house mould making expertise. The company’s experts have found a method of combining quantity dosing, the injection moulding machine, moulds, the take-off unit and packaging in a harmonious interplay. Roland Pirsic: “With our new technology we occupy a unique position in the market. In fact the micro moulding of LSR constitutes a stand-alone feature.”
starlim//sterner employs a small injection moulding machine with a clamping force of 10 kN for the production of LSR micro components. The machine is fitted with two injection units, one for thermoplastic and the other for LSR components. The precise mixing ratio of the basic components and additives is secured and the maximum shot volume of both components amounts to 150 mm3
. Direct feeding takes place using an open die concept,
the available mould area in the die amounting to 17 mm in diameter, while the maximum cavity depth divided between the feed and discharge side totals 12 mm. In order to prevent component damage, the clamping unit is subject to extremely exact control.
A handling unit removes the micro components and lays them aside while a camera and an image processing system monitors the part geometry. As an option, the injection moulding machine can be employed with cleanroom module, in order that medical components can also be manufactured with the required cleanliness.
www.starlim-sterner.com 8| commercial micro manufacturing international Vol 7 No.1
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