Laser Marking on PE sheeth

Hello,

Does anyone have experience with lasermarking on HDPE ?
The result very much depends on the PE color and the type of laser and power used. It would be interesting to hear if anyone has done tests or is even having an operational solution.

speed up to 30m/min
character hight 4-8 mm
every 50 cm a text of around 50 characters.

We do have working solution for PVC already for many years but for PE its much more difficult.

Hello again Jan,

The information I am going to give you is very old and my memory of this may not be as accurate as I would like to believe it still is.

Conventional UV laser marking works via the absorption of the directed laser radiation (heat) on the surface of the cable insulation or sheath as it moves by the laser marking head. This changes the sheath color by surface burning it without significant damage to the material itself. This is why you see that gold-brown color on PVC insulation. Polyethylene to be used for outdoor sheaths of course is however another matter as you have already well stated. This is because polyethylene destined to become a sheath on outdoor cable is UV stabilized to protect it from the sun's ultraviolet rays by blending it with a very dark color concentrate such as black.

If you use laser marking for identification on a black polyethylene sheath you have to think outside the box as ATT Lucent did some 15 or 20 years ago. They used an excimer (pulsed) laser system to micro-machine the moving surface of the polyethylene sheath. This was possible because an excimer laser doesn't remove material by burning or vaporising it as the other types of laser do.

The theory is that the polyethylene, upon absorption of the high photon energy from the excimer laser, results in photochemical disassociation of the polymer into monomer fragments. Because the monomer fragments occupy a volume larger than the original polymer, the material is quickly ejected from the irradiated region. Thus you can think of it more like an ablative process. Because the duration of the laser pulse is so short, there is no time for heat transfer to the surrounding region. As a result, the ablated material is ejected layer-by-layer on a pulse-by-pulse basis with little if any distortion to the surrounding material.

In practice however, the ablative process was found to be considerably more complex than the theory above as the absorbed photons could lead to color change in the material rather than the ejection of material. Thus experimentation is important.

ATT Lucent filled the resulting machined recesses with some kind of white or light yellow glue-wax in stick form that was mechanically rubbed into the shallow engravings and the excess wiped off. I also believe the glue wax was permanently bonded to the polyethylene under gas flame, infrared light or UV light.

I believe ATT Lucent had good success with this process initially but the breakup of the wire and cable group changed everything and I have no idea of what became of this no doubt patented process.

To follow up, you are going to have to do some research on this yourself. I do recall however that the excimer laser marking machinery was manufactured in California.

See the WAI Virtual Trade Show at www.wirenet.org/vts/vts_search.cfm and search for Marking Machines - Laser

Likewise you might also want to talk this over with Tri-Star Technologies at www.tri-star-technologies.com/

Hopefully others can contribute to this thread and correct any errors I have inadvertently created.

Please let us all know what you find out.

Sincerely,

Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com