14
A lighter alternative
The replacement of metal components with engineered plastics offers huge advantages, especially in the aircraft industry
Replacement for a stainless steel surgical device
Candidate to replace a forged aluminium luggage rack bracket
Moulded aircraft fairing Replacement for multipart steel bearing cage
With oil prices driving up fuel costs, weight- savings are on everyone’s mind. Besides significant weight reduction, plastics offer additional key features: corrosion resistance, potential for reduced part count, moulded-in rather than machined features, greater design freedom, moulded in colours and textures, and a naturally electrically insulating material. Plastics also free manufacturers from the long lead times that have plagued some aircraft materials, like titanium. The questions have been, “Is it practical? Is it safe? Is it cost-effective?” Vaupell’s many experiences with successful metal replacement programs demonstrate that the answer is often “Yes”. A growing number of plastics approach or even exceed the stiffness and strength of aircraft aluminium, magnesium and even titanium. Vaupell has helped with a number of successful metal replacement projects, from medical products like hip and bone repair components, to a relatively high-volume glass- filled nylon product that replaces the previously steel bearing cage for railway roller bearings. And, of course, innovative designers in the aircraft industry have come to us with many candidates from metal replacement. Some of these plastic parts are flying today, including PEEK brackets for ESD detectors in fuel tanks, glass-filled nylon cable brackets, fairings, clips, and a wide variety of other applications with structural and cosmetic requirements, using a full range of aerospace engineering materials, from PEIs to polysulfones, and various glass- filled polyamides. One recent example is the conversion of a
previously die-cast aluminium drain mast to moulded PEEK, with the advantage of significant weight reduction, elimination of corrosion issues
and much extended tooling life. Because of significant potential stresses on the part, the mounting holes are drilled after moulding, to eliminate the problem of potential weaknesses on the weld lines that would have been created by material flow around core pins in the mould. Besides the potential for fuel savings from
reduced weight, savings can be obtained on the parts themselves through elimination of painting or secondary coating, elimination of secondary machining operations, and the addition of moulded in graphics. Depending on the application, several metal parts can often be combined into one plastic part, eliminating welding and/or assembly.
The key to success is to work with moulding and material specialists to ensure that the part design and material selection are appropriate to the challenge. Some of the most exciting opportunities at present are in seating, cabin interiors, luggage rack systems, and cable and hydraulic routing.
A key aspect of the design challenge is to
ensure that the plastic parts are fully engineered for manufacturability. Moulded in stresses resulting from poor part design, inappropriately placed weld lines, thick/thin section transitions, and improper wall thicknesses are all issues that can dramatically effect the strength and utility of the part. It is important to partner with experienced plastics engineers and moulders to ensure that the plastic material is being used to maximum advantage. But with the appropriate engineering input, many metal components in aircraft today should be candidates for replacement with strong, corrosion resistant plastics, most of which are roughly half the weight of aluminium.
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