CTMA Project #: 140347
Problem: Due to operational requirements, NADEP Cherry Point must refurbish on average, approximately 150 main rotor blades each month. Sikorsky refurbishes approximately 80 additional blades per month. To refurbish each blade, workers must remove at least the topcoat (paint) from each blade. Because these blades use lightweight fiberglass composite substrates, coatings must be removed manually using air-driven orbital sanders. The process requires an extensive amount of tedious labor in a dusty, uncomfortable environment. Workers complain of repetitive stress injuries and fatigue. Lost time is significant. Because coatings contain toxic chemicals, personnel must wear extensive personal protection equipment to avoid dust inhalation. Conventional paint removal techniques, such as chemicals, plastic media blasting, or glass (sand) blasting, are known to damage the substrate and, therefore, are not viable. In many cases, this media will become contaminated with lead and chromates found in the coatings, thus producing secondary hazardous waste streams that require costly disposal. Hand sanding with air-driven orbital sanders can also cause damage to the substrate resulting in delays due the additional rework operations required. This manually-controlled sanding method is, however, the only coating removal method currently approved for blade refurbishment operations at NADEP Cherry Point.
Many other applications throughout the DOD complex face similar depainting issues during refurbishment activities. NUWC Keyport, involved in the refurbishment of torpedo components, anticipates significant secondary benefit through the technology evolution anticipated during this program. Hill Air Force Base, involved in the refurbishment of radomes and other aerospace components, can expect to benefit from lessons learned as well.
Benefit: The benefits of the project to stakeholders and participants are considerable.
- CTMA provides NCMS members with a test bed and access to an innovative maintenance activity technology that cost‑effectively solves environmental, health and safety problems.
- NADEP Cherry Point receives a cost-effective coating remover for test, evaluation, and eventual production use years ahead of the normal schedule for an innovative capital equipment item.
- Sikorsky gains a technological advantage and ensures that they remain the leaders in commercial maintenance service for helicopter blade refurbishment.
- NAVAIR, NAVSEA, AFRL and other interested DoD stakeholders will have operation and maintenance information to assess performance, feasibility, and cost effectiveness for related maintenance requirements.
- REPTECH/ARL Penn State meets its goal of improving the quality and cost-effectiveness of maintenance efforts through alternative technology implementation at NADEP Cherry Point
- GLC obtains valuable information on laser technology applications and market needs.
- NUWC Keyport, Corpus Christi Army Depot, Hill Air Force Base, and other DOD Depots will benefit from the evolution of the laser depainting technology that the program promises.
Solution/Approach: Several DoD technology development projects, including Navy REPTECH/ARL Penn State and AFRL efforts, have demonstrated that, in many cases, laser-based coating removal is a viable alternative to conventional depainting techniques. Furthermore, comparative investigations of technology alternatives have shown that laser-based coating removal is the optimum, cost-effective technology for numerous applications.
Many other coating removal techniques are not well suited to helicopter blade refurbishment. Chemical-based techniques are undesirable due the use of hazardous chemicals and solvents, which are costly to store and dispose. Plastic media blasting and pressurized water techniques are undesirable due to the generation of secondary hazardous waste, potential damage to the substrate, and invasion of foreign material into the composite sandwich. FlashJet is undesirable in this application because of the high heat input, difficulty in integrating real-time feedback to protect the substrate, and ineffectiveness in removal around sharp radii and edges. Laser-based coating removal techniques mitigate many of these concerns.
Laser-based coating removal technology does not produce any secondary waste, and, in many cases, actually produces less waste than the mass of the original coating (through volatilization of chemical compounds). The laser technique is highly controllable, and parameters can be chosen to remove very thin layers at each pass. Coupled with the ability to incorporate real-time sensing and control, this will ensure protection of the substrate. Fiber delivered lasers offer great flexibility in manipulating the beam, and well-designed robotics will permit processing of sharp radii and edges.
Recently, GLC used newly developed solid-state COTS lasers to build user-friendly systems for localized cleaning and depainting. The implementation of the technology at a Navy Depot as a cost-avoidance measure appears feasible, and could occur when integration and scale-up issues are resolved.
DOD Participation:
- NAVAIR – NADEP Cherry Point
- NAVAIR – NADEP Jacksonville
- NAVAIRSYSCOM, HQ
- NAVSEA
- Corpus Christi Army Depot
- Air Force Research Laboratory (AFRL)
Industry Participation:
- General Lasertronics Corporation
- Sikorsky Aircraft Company
- REPTECH/ARL Penn State
- NCMS
