Films provide toughness and clarity for rugged keypads

Vending machines must be easy to operate, hard-wearing and have clear, user-friendly selection pads. Richard Wöhr GmbH, a German company specialising in data entry systems and industrial housings, has recently launched an innovative keypad system for vending machines that uses the latest film technology from MacDermid Autotype.

Richard Wöhr's innovative membrane keypad is intended for vending machines dispensing coffee, snacks, cans and bottles. It features commands for variable coffee strengths and automatic cup recognition and has been designed to offer maximum reliability, exceeding current market requirements in every way.

The sealed and easy-to-clean membrane touch-keypad measures 837 x 204mm and is designed to withstand continual service by a variety of users. The selection pad also makes it possible to label each beverage with individual lettering or numbering on inserted strips, for further customisation at the point of sale.

Eighteen 16mm gold-plated snap domes encase electrical switching and form the tactile response keys, which are then embossed for better performance. These keys are printed with conductive silver and carbon inks on Autostat AHU-5 polyester film from MacDermid Autotype. Autostat is a high-quality, heat-stabilised polyester film that is distinguished by its excellent lay-flat characteristics. It is suitable for manufacturing circuitry in membrane touch keypads and as a contact film for conventional switches.

Tough and attractive

For the graphics overlay, Richard Wöhr used Autotex V200 film from MacDermid Autotype. This is a high-quality textured film consisting of a polyester base and a flexible, chemically bonded, UV-cured textured coating. The film has excellent mechanical properties for unsurpassed switch life, is resistant to chemicals and household cleaning agents, has a uniformly textured surface and an attractive appearance. Windowed areas in the display system were created using Windotex Gloss, a UV-curable, windowing lacquer designed to produce clear windows in Autotex film. This method of production offers a simple and cost-effective means of producing high-quality windows without the need for die-cutting or selective printing using a texturing lacquer. A further benefit offered by Autotex and Autostat is the optical clarity of the films that significantly reduces light loss and diffusion. The lacquers and printed images on the reverse or the insert strips therefore retain the correct colour saturation, luminosity and contrast.

Stefan Wöhr, a member of the management board of Richard Wöhr, explains: "Since our foundation in 1967, companies from a wide variety of sectors, from advanced electronics to mechanical engineering, have relied on our expertise. We offer products for every imaginable type of component for user interface systems and displays and our customers rightly expect us to cater for trends and present innovations. Vending machines are an ongoing requirement and the market expects a constant supply of improved, maintenance-free and easy-to-use data entry systems. Conventional polycarbonate films are out of the question for applications like these. That is why we turned to MacDermid Autotype to provide this solution.

"We have used Autotex and Autostat regularly and have found these two materials to be simple to handle and process, especially for tactile or domed switches, where they offer a constant service life of more than five million switch actuations (tested to the DIN 42 115 standard). What is perhaps equally important is the fact that they offer extremely high chemical and mechanical strength and are therefore perfect for keypads that have to withstand constant use in demanding conditions. The stringent demands made on our products by their challenging fields of application call for the highest precision. Given our high quality standards, we needed a supplier with a similar approach to quality and reliability. With its industrial films, MacDermid Autotype is the market leader in the field of polyester overlay films and MTS films, and is therefore the ideal partner for us because we can count on their unrivalled strengths of quality, consistency, reliability and product availability."