POLYGON SCANNER FOR LASER PAINT STRIPPING

Not only is the effluent removal highly manageablewith the EWI scanner, but the resulting solids in theeffluent stream appear to be completely “dry” ratherthan the sticky agglomeration that others havereported. Much study remains to be performed in theoverall effluent management area, but it is reasonableto conclude that this version of laser paint strippingproduces a near minimum of solid waste.On the other hand the efficiency and manageability ofeffluent removal comes with a challenge.Measurements of the flow volume and exit temperatureof the effluent stream (during 10 kW paint stripping)suggest that as much as 50 to 60 kW of thermal poweris being successfully removed from the laserinte raction region. This net combustion power must bemanaged, primarily through “dilution” with additionalpost-combustion air, in order that conventional exhausttube materials can be utilized. Fortunately, closeobservation of the flame inside the exhaust nozzlesuggests that combustion is substantially completewithin a few inches of the part surface. Thisobservation greatly simplifies the solution to this ratherlarge power management challenge.Summary AccomplishmentsThe benefits and advantages of the EWI polygonscanner technology for large area laser paint strippingare numerous and are summarized briefly below.• Highest paint stripping power capability• Available for multiple laser wavelengths• More robust than other scanners• Light weight for easier manipulation byrobots and other motion systems• Aero window eliminates need for consumabletransmitting windows• Highest reported laser paint stripping processefficiency• Highest reported laser paint removal rates• Facilitates efficient, complete, effluentremovalIn the overall scheme of a potential laser paintstripping system or facility, the scanner itself would bea fairly small and relatively low cost component. Still,the above advancements in the core laser paintstrippin g process technology are essential for thecreation of stronger business cases for specificapplications.For instance, the higher strippingefficiency and the lighter weight of the polygonscanner mean that the motion systems required forlarge paint stripping jobs (airplanes, ships, etc.) can befaster and lower cost. And, given the higher effectivepaint stripping rates of the polygon scanner, the overallproductivity of the paint stripping facility can behigher. For these and other reasons, this enablingpiece o f laser paint stripping technology substantiallyenhances the business cases for a multitude of potentialapplications.Future WorkAs encouraging as these results are, several areas ofrequired, additional development remain to besatisfied. Most important among them is the need fordevelopment of a process control technology.Specifically, it is essential that the overall laser scanner“system” be capable of monitoring and controlling thelaser paint stripping process so that the correct amountof paint is removed from the intended location. Manysolutions for this control requirement have beenconceived; some have been patented; and, some havebeen applied. Candidate control solutions forapplication to EWI’s polygon scanner technology areunder investigation, and success in this area isconsidered to be attainable in the near future.Continuing advancements in sensors, cameras, andcomputing power make this essential task muchsimpler and more af fordable than in the past.In conclusion it is reasonable to state that all therequired elements for successful, industrial, laser paintstripping application have been developed or arewithin our reach. Much work remains to be done, butthe path forward is clearer today than ever before.AcknowledgmentsEWI gratefully acknowledges the contributions andcollaboration with the following individuals andorganizations:• Dr. Craig Walters, co-developer of the EWIpolygon scanner and widely-recognizedleading expert in laser paint strippingtechnology.• II-VI Incorporated and specifically GaryHerrit, for his essential contribution to thefocusing optic figure solution.• Wayne Trail Technology for their precisionmachining of all the components in theprototype fabrication.• Air Force Research Laboratory and TomNaguy specifically for his support (throughCTC) of the initial demonstration of EWI’spolygon scanner technology.449