Small tubing is a key component in many common medical devices such as catheters. A frequent application is marking manufacturing and personal ID information on them. Due to the life-and-death nature of the medical industry, having clearly visible, permanent marks is essential. This makes laser marking an attractive option as it provides a permanent mark unlike various ink printing methods that can eventually rub away, causing the loss of critical data and the potential for leaving contaminants.

A CO2 laser mark, however, will permanently change the physical structure of the tubing surface in the mark region. Thus, an important factor to consider is whether the laser marking process will damage the tubing. The CO2 laser mark is typically engraved slightly into the plastic. As a result, care must be taken to not go too deep as this could weaken the tube wall. In addition, the plastic must not melt very much during the marking process or the mark will be unreadable especially when the text size is very small.

For this particular application, our requirement was to mark very small text on a proprietary composite thermoplastic tube, with an outside diameter of 1.4 mm (0.054"). The marking setup consisted of an FH Flyer marking head and a 48-1 (10 W) laser controlled by our WinMark Pro laser marking software. The Flyer head was equipped with an 80 mm focal length lens that provides a 116-µm (0.005") spot size. This small spot size is critical to marking very small text, especially when marking plastics where any slight meltback might compromise the "crispness" of the characters. For this reason, we generally recommend specifying a Text Height value that is between 7 to 10 times the focused spot size.

In this example, we used WinMark Pro'’s Simple stroke font and set a Text Height of 1.3 mm (0.05") in the mark file. The mark Velocity was set to 889 millimeters per second (35 inches/sec) and the Power was set to provide 5 W. This very low power setting helped ensure that the mark was not engraved too deeply. The resulting white, semi-transparent mark did not weaken the tubing and our six-character text string was completed in a cycle time of 0.13 seconds per mark.

This engraved mark exhibits excellent contrast and the 0.05" high text is easily read under normal lighting.

 

A close-up photo shows some meltback; however, the 5W mark did not penetrate or weaken the tubing.

 

 

This polyester mesh filter media is an excellent candidate for CO2 laser cutting, as it exhibits cleanly cut edges at very high line speeds. Polyester filter media is used in residential, commercial, and industrial HVAC applications, and is a common filtration method for keeping dust particles out of fan-cooled industrial equipment.

For this application trial, our cutting setup consisted of a Firestar laser and an XY "flying optics" table. Beam delivery through the cutting head was focused by a 63.5 mm (2.5") positive meniscus lens that provides a 100-micron (0.004") diameter spot with a 1.8 mm (0.07") depth of focus. For gas assist, we chose nitrogen at a delivery pressure of 0.7 bar (10 PSI).

 

A close-up view of 0.072"-thick polyester filter media that was cut at a speed of 750 IPM using only 25 watts of power.

The cut edge of this opaque red stained glass shows a brittle, underside dross that removes easily to expose a cleanly cut edge.

 

These small 1.375" diameter circles were cut out of translucent yellow stained glass using 400W at a speed of 50 IPM.