Pulsed Semiconductor Diode Lasers as an Efficient and Affordable Decoating Method for Automotive Plastics, Composites and Metallic Surfaces 2002-01-0292

The removal of paint from advanced materials such as composites and plastic automobile fascias and parts has been difficult to do with present media and chemical stripping technologies. For example, currently for production parts, discrepant plastic parts are decoated by conventional means that damage the surface, and subsequently cannot be re-painted. To minimize the waste stream, the parts are decoated, ground into small particles and a percentage of the material is fed back into virgin TPO (thermoplastic olefin) for remolding. This has been the accepted practice since effective ways to decoat without doing surface damage have not been found. Subsequently in the aftermarket, repair shops must replace TPO parts when they are damaged to the substrate, as marks cannot be flared out. The same is true with composite and fiberglass structures for aircraft, which undergo regular, depaint cycles and are either hand sanded or use a light media blast that are slow and can be add further damage. One method tested in the early 1990's to decoat plastic, fiberglass and composite that proved to work better than any other method were pulsed lasers, such as Nd:YAG and Carbon Dioxide lasers. But the drawback on these lasers is that they are expensive, expensive to operate, bulky, approximately 10% energy efficient, cannot be used in all environments and require specialized laser technicians. While the method was sound, the equipment was not well suited for the application.

A new high power laser was developed in the late 90's, the semiconductor diode laser, the larger version of the low power semiconductor diode lasers used everyday in market scanners and compact disk players. This allowed for a lasing source that was compact yet powerful, approximately 50% efficient on energy, and robust enough to be used in industrial environments and most importantly, affordable. Semiconductor diode laser decoating has proven to be able to remove coatings from plastics, fiberglass, and composites, leaving the surface in a condition to repaint, a time, labor, and waste savings over the current method.

The semi-conductor diode laser de-coating is a non-intrusive, non-kinetic energy process that has successfully removed coatings from a variety of substrates such as: composites, fiberglass, metal, and plastics, very rapidly (up to 210 sq/ft per hour) and with only a minimal increase in temperature (100-150F), since the energy is mostly absorbed and utilized in coating decomposition (i.e., instant pyrolization and evaporation). The only waste associated with this process is the ablated coating that is vacuumed from the surface and captured in particle filters, leaving a minimal amount of waste.

The objective of this paper is to show how LANCORP ASI has developed pulsed diode laser technology into a formidable decoating system, and will show data from testing validating its process to remove organic coatings from a variety of advanced materials without damage using feedback control systems and improved beam stability systems to ensure predictable cleaning and coatings removal. The advantage is that diode lasers are 50% efficient costing only $4/hour to operate and about 1/8^th the size of other lasers and ¼ the cost.

LANCORP ASI will show that pulsed high-energy diode laser decoating technology has now progressed to the commercial and economic level of availability necessary to be implemented into industry for automotives, parts and fascias as well as for powdercoat removal, and for aircraft maintenance.