Will the well-known success of composite materials in aircraft construction be continued in the automobile field? There are good reasons to think so. Large automobile companies are at present planning to make even load-bearing car components out of composite materials, and to employ them for regular production. The fact that this will also – most particularly – present challenges to tool manufacturers, is already being made clear by a number of applications in the automobile field, for instance in the USA: tools from LMT ONSRUD are being used to machine a front spoiler for racing cars.
The properties of these materials have been valued in the car racing field for decades. They are lighter than aluminum, and at the same time just as strong as the metal. In an accident, composite materials can in fact absorb more impact energy than metals. In this context, the research body Automotive Composites Consortium states that composite materials can absorb approximately 100 kilojoules of impact energy per kilogram, whereas steel can only absorb 25 kilojoules. The design of the formula one chassis, which was made for the first time of carbon composite material as early as the 1980s, is a significant demonstration that the careful use of composite materials in automobile construction is no compromise to safety.
Machining special materials
An example from Piedmont Plastics in North Carolina indicates the kind of special challenges that can occur when machining these materials. Amongst the materials used for fabrication by this American company is a special composite, characterized by high specific stiffness and unusual toughness. "On the other hand, the composite material is made of polypropylene tape yarn (PP). The low melting point means that it tends to fray when it is machined. Users are therefore looking for tools that yield a perfect cut edge", explains Scott Feimster from LMT ONSRUD.
Optimized chip flow
For machining the front spoiler, the solution turns out to be the "Onsrud 52-702". Feimster explains that "The solid carbide tool for machining plastic and composite materials has a cutting edge geometry that is ideally suited to polypropylene". The high effective cutting angle generated with this tool plays a large part in this. It helps to ensure that clean cut edges are created. Chip removal flow is optimized at the same time. "The finishing is finally carried out at Piedmont Plastics using the 52-702 tool. The result is so good that we can omit any other machining stages", concludes Feimster.
Background: Composites know how
For decades, LMT BELIN and LMT ONSRUD have been developing new tools designed specifically for machining composite materials: The coating geometry, the coating and the tools substrate all contribute to cut edges that are smooth, straight and free from burrs. They allow high feed rates and longer tool lifetimes. Production using these tools is therefore also more profitable.