Responding the rising demand for micro parts made of silicone, WITTMANN’s MicroPower injection molding machines are installed at the Austria headquarters of starlim, the world’s largest silicone processor.

WITTMANN’s MicroPower as the standard equipment in starlim’s area of silicone micro molding. (Source: starlim)

starlim produces micro parts, including O-ring and hearing aid component, with WITTMANN’s machines. The O-ring is with measurement of 0.7 x 0.4 mm and the hearing aid component is with measurement of 6 x 5 x 1 mm.

Micro-molded hearing aid component is too small for quality inspection with magnifier. Often, it has to be done under microscope.

The hearing aid component is a two-component part. At its center, there is a membrane consisting of blue-colored liquid silicone (LSR), which is surrounded by a robust thermoplastic frame made of PBT, facilitating the assembly inside the hearing device.

The two-component part of the hearing aid component.

High control accuracy for precision demanding applications

The hearing aid component was produced inside a single-cavity mold on an all-electric MicroPower injection molding machine. The main challenge in producing the hearing aid components are the narrow tolerances in the area of the corrugation on the membrane body.

This relies on the control accuracy of injection molding machine. MicroPower machines stand out in their extraordinary precision in the execution of all parameter settings. “This extremely sensitive dynamism combined with absolutely stable and accurate regulation is setting new benchmarks,” commented Dominik Kreuzmayr, marketing team leader in starlim.

In the case of these hearing aid components, the high impression accuracy is not only decisive for efficient assembly. In this application, high precision is much more important for accurate sound reproduction.

Compact design leading to high processing efficiency

MicroPower only takes a floor space of two square meters, the all-electric work cell fits in the entire equipment, including the clamping unit with a rotary plate, the patented two-step injection system, plus materials handling, automation, temperature controller, the quality control system and further process units.

MicroPower as a complete production cell, accommodating all process components within a compact space.

MicroPower offer ample room for automation, including vertically integrated robot.

With these, the machine’s mold space is still able to keep with a 400 mm distance between platens easily accessible. Linear guides ensure highly sensitive mold protection, and thanks to a high-precision 5-point toggle lever system, the clamping force is very evenly distributed across the mold parting line.

This machine design enables starlim to move the injection plunger right up to the mold parting line, which contributes to high processing efficiency. It significantly reduces the sprue in size or even eliminates it altogether. Since fully vulcanized LSR cannot be recycled, silicone injection molding reaps the greatest benefit from this material-saving process.