Marking Oil Seals

Oil seals, commonly used in automotive and industrial machinery applications, are instrumental for sealing rotary shafts and serve a dual purpose—to retain lubricants (such as oil or grease) and to exclude dirt, dust, and other abrasives from bearings and wear surfaces. Oil seals are manufactured primarily from nitrile, silicone, and EPDM rubber. Nitrile rubber is the most widely used elastomer because of its wear resistance and ambient operating temperature range.

For this customer application, we were asked to mark a 10-character code on the outer ring of an oil seal. At the 10.6 micron CO2 wavelength, rubber materials mark very well, but the unusual aspect of this mark was the size of the mark area on the outer ring—it measures only 1.25 mm (0.049”) high!

Our marking setup consisted of a Synrad laser, FH Series Flyer marking head, and our WinMark Pro laser marking software. The Flyer head was equipped with an 80 mm focusing lens that provides a 116-micron (0.005”) spot with a 0.8 mm (0.032”) depth of field. To create legible text marks, our rule of thumb is that character height should be a minimum of seven to ten times the focused spot size. For this application, the character code was 1 mm (0.039”) high, which is on the low-end of the range for an 80 mm lens.

To create this mark we started with the ‘Simple’ stroke font, set a Text Height of 1 mm (0.039”), added 0.15 mm (0.006”) of Extra Character Spacing, and entered a Text Radius of 54 mm (2.125”) to match the curvature of the seal. On the Marking tab, we set a Power, duty cycle percentage, equal to 10 watts, entered a Velocity of 1016 millimeters per second (40 inches/sec), and set the Mark Passes property to 4.

Although this engraved, contrasting mark
measures only 1 mm high, it is easily
readable without magnification.








It took only 0.13 seconds to produce this
10-character text with four Mark Passes using
10 watts at a speed of 40 inches per second.

Using 100 watts of power, we cut these custom gaskets from a sheet of 0.256” thick EVA foam
at a linear cut speed of 275 inches per minute in
a cycle time of 4.84 seconds per part.

Marking Polyethylene Dip Tubes

Virtually every trigger or pump sprayer on the market today uses a dip tube to transfer the container contents up to, and out of the nozzle. Dip tubes are manufactured by extruding molten plastic through a die, cooling the newly formed tubing, and then trimming to length using mechanical cutters or lasers. The application presented here is unique because a requirement exists to mark a 10-character manufacturing code along the length of the tube during the assembly process.

The marking setup consists of a Synrad CO2 laser, an FH Series marking head, and WinMark Pro software. To focus the beam on the dip tube, a 200 mm lens was installed to provide a 290-micron (0.011”) spot with a 5 mm (0.196”) depth of focus over a mark field measuring 165 mm by 134 mm (6.5” x 5.3”). We created the mark file using one of WinMark Pro’s twelve built-in stroke fonts (Simple) arranged vertically along the length of the tubing. The text, consisting of 3.8 mm high by 1.3 mm wide (0.149” x 0.052”) characters, was marked using 20 watts of power at a velocity of 508 millimeters per second (20 inches/sec).

Polyethylene is one of a few plastics to exhibit a raised, contrasting mark caused by an interaction between the CO2 beam and the material surface.
This 10-character text string was marked using
20 watts of power at a speed of 20 inches per
second in a cycle time of 0.16 seconds per part.