Hochdorf, Germany-based Leonhardt e.K. is using a compound made from up to 95 percent tungsten metal powder and a polyether ether ketone (PEEK) binder for metal injection molding (MIM) of collimator lenses.

These have precise 0.1-0.15-millimeter-thin walls and 460 conical openings, and are used to guide beams and also shield computer tomography equipment against X-rays.

The company tried using selective laser sintering to make the prototypes. Although those prototypes had the required precise dimensions, surface roughness was too high and could not be overcome by electro-chemical polishing sintered parts.

So it was decided to injection mold the parts, using filigree mold inserts, to achieve the necessary finished surface. Company owner Wolfgang Leonhardt said the PEEK binder was essential to provide the abrasive metal powder with the required high degree of flowability to make it at all possible to injection mold.

Leonhardt said his company is presently the only one with capability of processing tungsten metal powder in this way.

While the collimator project is presently on hold, the company's experience with tungsten/PEEK molding has benefited a project at Stuttgart University.

That project addresses challenges of molding and bonding together of different ceramic materials via injection molding to join structural, high-temperature-resistant and conductive parts. Such components are required in high-frequency surgery.

Obtaining high bond strength between materials is one issue. Another is to apply mold tool construction features and appropriate additives to condition the materials in such a way that they shrink synchronously under the heat while the delicate components are sintered.

Leonhardt said the multi-component molded ceramic parts in medical equipment "not only combine the properties of the individual components, but are also easy to disinfect, due to high heat, acid and abrasion resistance."

Using its three Arburg injection molding machines, Leonhardt has also started work in Hochdorf with molding tungsten/PEEK compound into fuel cell membrane plates.

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