24 June 2008

Laser Marking Silicone Rubber Keypads

Silicone rubber, or elastomeric, keypads are being introduced in a variety of devices in consumer, medical, industrial, and automotive markets. These silicone rubber keypads are replacing keypads and keyboards based on mechanical switches in part because silicone rubber moulding technology allows the manufacturer to easily create custom keypads or individual key shapes. In addition, the durability of modern silicon rubber formulations means that elastomeric keypads have operating lifetimes that now rival those of keyboards manufactured with traditional mechanical switches.

This application demonstrates the feasibility of marking symbols and text by ablating an existing inked coating. The marking set-up consisted of an FH Flyer marking head, a Synrad 10-watt CO2 laser, and a copy of Synrad’s WinMark Pro laser marking software. The Flyer head was fitted with a 200 mm focusing lens that provides a 290-micron (0.011") diameter spot with a 5 mm (0.196") depth of focus.

A five-character text object was created using a filled TrueType® font, Arial Black. A  Text Height was set at 2.54 mm (0.10"), a Text Width at 1.143 mm (0.045"), and added 0.38 mm (0.015") of Extra Character Spacing. To create a smooth fill, a Filled Font Resolution value of 600 was entered and then set Text Curve Detail to 600.

To mark the ink-coated silicone keys, a Power (duty cycle percentage) was set equal to 10 watts at a Velocity of 2,032 millimetres per second (80 inches/second) with two Mark Passes. These parameters allowed individual keys to be marked in a cycle time of 0.77 seconds.

This silicone rubber keypad was marked  by ablating the ink coating from the top of the key.  The "Power" legend was marked using 10 watts of power at a rate of 80 inches per second using two passes. Total cycle time for the operation was 0.77 seconds.

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