Outstanding innovation: On the first day of the K trade fair (8–15 October 2025, Düsseldorf), Michael Weigelt, Managing Director of the TecPart Association, presented two of the coveted TecPart awards to Axel Zuleeg, CEO and to Thomas Ruff, Head of Technical Sales.

Form-fitting and without bonding

The best of three material worlds: the optical lens made of sapphire glass, a robust thread made of stainless steel and plastic (POM), which connects everything with its geometric flexibility – form-fitting and without the bonding that was previously standard. The eyepiece funnel, which is used in optical instruments for laboratories and medical applications, was to be manufactured in a fully automated production process and withstand the conditions of steam sterilisation in an autoclave.

Position accuracy is crucial

To achieve this, the glass lens (diameter 8 mm, thickness 1.8 mm) and the threaded metal insert are inserted into the injection molding tool fully automatically in series. The precision of the insertion process and position accuracy are particularly important here: The lens must be positioned absolutely flat so that there is no optical distortion when the eye funnel is later used. To achieve this, it is held in position by vacuum, while the threaded insert is fixed by two pins that are later retracted. Both inserts must withstand the injection molding process on a machine with a clamping force of 500 kN without changing their spatial position and without damage. When designing the process, particular attention had to be paid to the shrinkage of the plastic in order to achieve a secure connection without exerting too much pressure on the glass, which could impair the optics. The injection moulding tool is designed in such a way that thread inserts of different dimensions can be used without modification.

Capacitive operation despite metal layer

The automotive component was designed to replicate the look of BMW's real crystal interior (with Svarovski) – at a lower cost, but with capacitive operation. This meant that only the In-Mold labelling process could be considered. Indium offers a chrome sheen and, like all metals, is inherently shielding. However, the molecular density can be designed in such a way that it is suitable for capacitive operation and enables exciting optical effects through colour printing on the back (Deep Metal). However, it was questionable whether the indium PVC-coated film (melting temperature indium 140 °C) could be coated with a 5 mm thick PC layer (processing temperature 300 °C). The film specialists at KH mastered the challenge. To do this, the highly sensitive film (indium 1 to 2 µm, colour layer 3 to 4 µm) is decorated using a screen printing process, shaped, cut and processed using an injection molding process.

Trace-free further processing

A laser then removes the entire coating of paint and indium along a defined path so that the transparent PC film is not damaged. The tolerance here is in the micrometre range. The symbols created in this way, which must not have any laser markings, are screen-printed directly onto the component in white (translucent) and the sprue is milled away without any run-off and visible traces, following the contour. The front is coated with a UV scratch-resistant lacquer. Due to its mirrored surface, the film must be processed without leaving any traces, which required special painting fixtures, among other things. But now the way is clear to move away from the previous purely black control elements to ones with more pizzazz.