UV Laser Wire Marking: Explaining Our Technology

UV laser wire marking was originally developed in 1987 by Spectrum researchers to meet the needs of the international aerospace industry for a means of safely applying permanent identity codes to non-stick PTFE/Teflon and similar wire insulations, as well as fibre optics.

The UV laser marking process, pioneered by Spectrum, causes no damage and no change to the mechanical or electrical properties of the wire.

In direct contrast, the old hot stamp method, is views as an aggressive and potentially damaging process; as a result it is banned under SAE AS50881 (previously MIL 5088L) and similar specifications.

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Above left: Spectrum UV laser marked wire section with mark penetration hardly visible. Mark depth is typically 10 – 20 microns (less than 0.001 inch). The integrity of the wire is unaffected.
Above right: Hot stamp marked wire section illustrates significant deformation and potential for damage to the wire insulation.

Ultra violet (UV) laser wire marking is now well accepted as a manufacturing process within the international aerospace industry. It is currently employed in the initial stages of electrical systems manufacture on virtually all leading edge commercial and military aerospace programmes in North America and Europe.

Lasers have been around since 1960 and are now widely used in a variety of applications from the ubiquitous bar code reader at the supermarket check out to the “read” head in CD players at home, to laser welding and cutting equipment on the auto production line. Yet many people still view lasers as remote “star wars” technology.

In reality laser beams are composed of light, one of the many forms of energy. However, unlike “normal” light sources, they have some very special characteristics. While everyday light sources, from the sun to a light bulb, radiate in all directions and over a wide wavelength range, lasers have narrow directional pencil like beams and operate at precise and narrow wavelengths (single colour). This key difference gives lasers a big plus when using them for material processing of whatever nature, namely precision and control.

It is of paramount importance to note that not all lasers are the same. In fact there are many hundred different types. Generalizing, however, we can split them into two groups:

  1. Shorter wavelength ultra violet (UV) and visible lasers: Enable materials to be “cold” processed – they create little or no significant heat effect in the work piece whether it be marking, cutting or some other process.
  2. Longer wavelength infra-red (IR) lasers: Interact with, or process materials primarily by thermal means, i.e. by direct heating – perfect for welding and cutting metals and other materials which are non-heat sensitive or where thermal side effects are acceptable to the user.

Selection of the right laser and wavelength for a particular process is therefore of key importance.Spec Tech laser marked wire

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The precision of UV lasers is graphically illustrated in the photograph on the right. This shows a 26 AWG single core wire with a diameter of 0.8mm (0.031 inch), laser marked on the fly on a Spectrum UV laser wire marker.

The “cold” UV laser wire marking process developed by Spectrum Technologies is quite different and is based upon a change in colour of titanium dioxide (TiO2) pigment brought about by the laser. This normally white pigment was already used in aerospace wire insulations for other purposes.

In the wire marking application, the UV laser beam changes the color of the TiO2 particles already contained within the wire insulation by rearranging their crystalline structure on a microscopic scale. The rearrangement is permanent for all practical purposes. This gives the TiO2, and thereby the insulation, a blackish color, hence creating a colored or marked wire surface. According to tests carried out by a variety of end users, there is no burning, no significant material removal or change in the wire’s mechanical or electrical properties. The mark is embedded to a depth typically of the order of 20 micron (0.0008 inch) thereby providing permanence against abrasion and fluids.

Permanence against perhaps less obvious factors has been tested by plunging wire samples into liquid nitrogen to test the effect of low temperatures (-196°C) and holding wires for several hundred hours at or above their maximum rated temperature.

Samples have been tested at up to 310°C without ill effect. Samples have also been exposed to intense ultra violet to simulate the long term effect of sunlight.

Virtually every test carried out on properly composed and marked wire shows that there is no material change in the mark.

Perhaps the best demonstration of this is to place laser marked wires in hot hydraulic fluid, such as Skydrol, and leave them to soak for 24 hours. On removal, samples have been given a “real life” test and the marked wire has been immediately rubbed, while still wet. A UV laser marked wire sample has never failed this test.

The result graphically illustrates the permanence of Spectrum’s laser mark compared to typical ink marks.

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The results from the Skydrol Test: Spectrum Laser Marking Vs Ink Based Marking before and after soaking in Skydrol.