Synrad laser used to mark acetal resin

A Synrad 48 Series 10W sealed CO2 laser and a Synrad FH Series marking head from Laser Lines are being used to mark Delrin, an acetal resin, which is shaped to encase a light-emitting diode (LED).

Polyoxymethylene, an acetal resin sold under the trade name Delrin, can be moulded to form a variety of products.

In this example, the injection-moulded Delrin is shaped to encase an LED.

The marking requirement is a four-digit code, readable under a microscope, to aid product traceability.

This is a relatively easy task as CO2 lasers produce engraved marks on most plastics; however, as the customer uses a swatch of green ink to mark the cathode (negative side) of each LED case, highly contrasting text marks were obtained that are readable by the naked eye.

A very small character height of only 0.51mm (0.020in) is required in order to fit the four-digit text string onto the 2.7mm-wide LED body.

To accomplish this task, a Synrad 48 Series 10W sealed CO2 laser was set up and a Synrad FH Series marking head has been fitted with an 80mm focusing lens.

The 80mm lens provides a 116-micron (0.005in) spot size with a 0.8mm (0.032in) depth of focus.

Using Synrad's Winmark Pro laser marking software, one of Winmark Pro's built-in stroke fonts was chosen and a four-digit text object created.

The cycle time for this very small mark is 60ms.

Although the 0.020in-high characters are just legible without the aid of a loupe or magnifier (and readable under magnification), this text size is about the minimum obtainable with an 80mm lens.

The minimum text height should be approximately four to seven times the spot size of the lens.

This ratio ensures that the beam diameter is not large enough that it fills the space between the strokes that form each individual character.

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