Cherry Electrical Corp started manufacturing computer keyboards in the 1980s. The individual keys, however, originally injection-molded in 2 colors, proved to be too expensive for the emerging mass PC market. In an effort to reduce manufacturing costs, the sublimation labeling method was introduced. This process, however, brought its own problems due to the ever increasing number of country and function variants, as special sublimation paper had to be kept for the labeling of each individual character. These problems prompted a search for alternative production methods that would provide a more flexible and cost effective way of labeling the keyboard keys. It was during this review of alternative technologies that the Rofin and Cherry relationship blossomed.

Using the correct parameters, Nd:YAG solid-state lasers generate a high-contrast marking through a color change in the material on a number of plastics. In contrast to printing, laser marking is indelible and antiabrasive, even in cases of intensive use. With this process, the flexible deflection of the laser beam by galvo scanner heads provides every conceivable option of form and marking content. The target cycle time together with the size of the marking area, however, created a headache for Cherry. The processing area of a scanner head only covered half the width of the keyboard, and mechanical repositioning of the keyboard or laser head was not possible due to the short 20 sec time available for each marking cycle.

No Room for Downtime
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Laser specialists Rofin-Sinar considered the application requirements closely before suggesting a solution based upon a laser, a beam splitter, and 2 deflection heads. The beam splitter would guide the laser beam through the scanner heads sequentially. Each head would then each mark half the keyboard in turn, within 10 sec. Rofin was completely confident that it would be able to configure this sophisticated system to provide reliable and consistent operation. With the Cherry plant running a 3-shift operation, 7 days a week, there was no room for downtime due to teething problems with a new technology.

The prototype system delivered by Rofin fulfilled all expectations. Cherry then further optimized the composition of the plastics used in the manufacturing process to obtain the best possible marking results. Cherry, therefore, became one of the first suppliers to the world market able to offer the new, flexible, high-quality marking method for keyboards. Subsequently, laser marking has become established as the standard method for the production of keyboards.

Today at Cherry, up to 3 lasers mark a keyboard at once—2 at the top and one at the bottom. In this way, the complicated adhesion of a label to the bottom of the keyboard is no longer necessary. If desired, monochrome manufacturer logos or text can also be generated at the same time. If necessary, the complete marking procedure can be completed in less than 5 sec.

On some of its 5 assembly lines, the company is producing value-added keyboards incorporating integrated bar code or chip card readers and fingerprint or RFID sensors. A number of Rofin-Sinar second-generation diode-pumped lasers also permit bright white marking of black keyboards.The lasers run reliably and malfunction-free around the clock as a key part in the production of the 10,000 keyboards that leave the factory each day.