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Some early evaluations of plastic media resulted in adverse test data conclusions. These conclusions ranged from excess surface roughness and metal loss to decreased fatigue life and on to damage of composite surfaces. Fortunately, contaminated media and uncontrolled blast parameters were later recognized as being the basic cause of negative test results. Tests were rerun to confirm the existence of acceptable test data provided clean media was utilized. Efforts were directed towards assuring the user that recycled media had been efficiently cleaned. Existing equipment was not adequate for the separation of dense non-magnetic particles like sand. In this paper, we outline our development of a high volume dense particle separator. Use of this equipment will enable the operator to be assured of using only clean media.

On May 3, 1985, Republic Airlines (now Northwest Airlines) dry stripped with plastic media blast (PMB) their first DC-9 aircraft in Atlanta, Georgia. Four days later, Hill Air Force Base began production in their new facility designed to dry strip F-4 fighter aircraft in Ogden, Utah. These two important steps initiated the first generation of airline and military production PMB dry stripping. After this inception of the PMB process, numberable questions were raised pertaining to structural safety after being subjected to dry stripping. In the intervening four years, process improvements have been made and test data accumulated to verify safety of the PMB process. Boeing, with approval by the Federal Aviation Administration (FAA), has issued their specification for plastic media (PMB) dry stripping of airframes, Document D6-54705, PLASTIC MEDIA ABRASIVE STRIPPING OF ORGANIC FINISHES. We consider this to be the start of the second generation airliner dry stripping program.

Conventional paint strippers cannot be used on composite surfaces without damage to the substrate. Current practice is the use of hand sanding for paint removal from these surfaces. Plastic Media Blast (PMB) offers a more economical means of paint removal. In this paper, it is our intent to provide data supporting PMB as a viable process for paint removal from composite surfaces. The PMB process eliminates health hazards associated with chemical stripping and reduces hazardous waste. Plastic media dust is classified as a hazardous waste only if the paint system being removed contains sufficient quantities of hazardous ingredients.

In April, 1986, the U.S. Air Force selected Ogden ALC (Air Logistics Center) to investigate automated/robotic capability for U.S. Air Force Logistics Aircraft Maintenance Divisions to plastic media blast (PMB) F-4 and F-16 aircraft. This paper discusses the three phases of the contract: *Phase I - Process Selection and Optimization (completed July 1987). Different stripping methods were evaluated before selecting plastic media blast (PMB) as the most viable process. Design configuration mandated incorporation into existing facility. *Phase II -System Fabrication, Test and Validation (estimated completion by April 1989). Southwest Research Institute in San Antonio was awarded contract for design of bench model. Design requirements to include a one time strip clean operation. The U.S. Air Force will review vision system translation by the robot and give final “buy off” of the operation. *Phase III - Installation and Verification (estimated completion date is December 1989).

Many topics are covered in this discussion of the ninth year since production dry stripping began in May 1985. Chemical strippers continue to be heavily regulated or banned. All other alternate coating removal processes are still in developmental stages, have not shown viability for production use and have not been accepted by maintenance operations or received manufacturer approvals. Dry media stripping continues to expand and to produce a very successful record--particularly wheat starch media. In a no technical objection letter dated April 30, 1993, America West Airlines, Phoenix, Arizona, received authorization for five time stripping of Boeing airframes utilizing wheat starch media. Additional approvals for graphite-epoxy and fiberglass composite dry paint stripping were recently published by Boeing. Hill Air Force Base, Utah, generates zero hazardous waste from its dry stripping operation.