4 December 2008

Marking Polyacetal (Delrin) Components

Polyacetal, also called POM or polyoxymethylene, and widely known under the trade name Delrin® is often used for manufacturing lightweight parts to replace heavier metal components. Polyacetal is an engineered thermoplastic polymer that features high wear resistance, high flexure fatigue strength, and excellent dimensional stability. It is easily formed by various moulding processes including injection, compression, or blow moulding, by extrusion, or by rotational casting.

The requirement for this application is to mark a moulded valve body. Because polyacetal produces a slightly contrasting, engraved mark, the identification information is not readily visible (or distracting) to the consumer, but is easily seen on close inspection. The engraved mark is permanent and will not wipe off or smear if exposed to chemicals or cleaners.

To create the 13-character text string shown in the photograph, a Synrad sealed CO2 laser was used with an FH Series marking head driven by Synrad’s WinMark Pro laser marking software. The FH head was equipped with a 125 mm lens that provides a 180-micron (0.007”) focused spot with a 3 mm (0.118”) depth of focus spanning a maximum mark area of 85 mm × 105 mm (3.4” × 4.2”).

In WinMark Pro, a text object was created with the desired Text Caption, selected an outlined TrueType® font (Arial) for clarity and set a Text Height of 4.43 mm (0.1745”). On the Marking tab, a Velocity of 381 millimetres per second (15 inches/second) was set and a Power, PWM duty cycle percentage, corresponding to 10 watts. With these parameters, the 13-character, two-line text string was marked in a cycle time of 0.70 seconds per piece.

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