AMB exhibition will take place from 16 to 20 September 2014 in Stuttgart, Germany. This edition will focus, as usual, on “Key to markets”, specially on composites and composite materials, in the area “Competence in composites”, where exhibitors display their special skills.
“The particular challenge in the machining of composites lies in the reliable and efficient machining, particularly the drilling of so-called stack materials”, explains Dr. Peter Müller-Hummel, Head of the Business Division Aerospace & Composites, at Mapal Dr. Kress KG in Aalen. To date, sometimes composite materials, made from composites and metal materials such as titanium or aluminium, still have to be bored out in several steps. “In the future these bore holes are to be completed in a single work process.” Under no circumstances, however, should this affect the quality. Whereas up to now the bore hole diameter changes over the service life of the drilling tool, today Mapal can achieve a constant diameter in all stacks by using a new type of technology. Dr. Müller-Hummel: “With this technology bore holes can be reliably produced in the H8 tolerance range with a process capability index of over 1.4.” Nevertheless, an important prerequisite is that the environment and the machine satisfy this quality standard.
The trend is heading towards significantly higher quality, but more durable tools, in order to reduce the price per bore hole. An example of such a tool, which can be seen at the Mapal Stand 5D32 within the framework of the PTW special show in Hall 5, is the Tritan Drill for difficult drilling situations. Mapal promises reliable machining and sig-nificantly better performance in comparison to conventional solid carbide drills. Three blades and an aggressively designed, self-centring cross-cutter should lead to maximum position precision upon initial contact with the workpiece – particularly important for difficult boring situations such as drilling through material or entering cross holes. The special sanding pad should keep the cutting pressure and blade temperature low, the point discharges the swarf without friction via three clamping slots.
Martin Heckel, Head of Product Management at LMT Tool Systems GmbH in Oberko-chen, sees the aerospace and automotive industries as the trendsetters for composites. But several new industries such as wind energy are now also pushing the use of compos-ites. Depending on the requirement of the component, diverse lightweight materials such as titanium, aluminium, CFRP, glass fibre reinforced plastic, CFRP-metal layered compound structures and honeycomb structures, are also being used, whose reliable machining poses huge challenges. “What is characteristic of these technologies is that they not only substitute materials, but also demand a separate process chain from the component design to the manufacture of the raw materials and semi-finished products, the shaping through to the realisation of the final contour and surface of the compo-nent.” For machining processes an optimal surface quality and high tolerance precision has to be combined with tools boasting an extremely long life. This is why the LMT Group is developing customised solutions for its customers which are specific to the applications and materials.
For instance, at its AMB Stand 1F52 in the L-Bank Forum (Hall 1) LMT showcases the DFC Compression Mill, a drill with a counter-rotating twist and a defined compression point. “Below this point it has an ascending twist, above it pushes the swarf downwards. In an optimal situation, the pull and push are at equilibrium, the laminated workpiece is properly compressed”, explains Martin Heckel. For processing so-called “honeycombs”, LMT Onsrud developed special slot millers and milling cutters with variable cutting heights and replaceable cutting parts. These structural and inner panels are used in aero-planes. The slot millers can cut the top layer and undercut the honeycomb structure in just one step. Using a PKD 2 tool the top layer and honeycomb structure are then cut. The “One-Shot-Drill” from LMT Belin thus combines three work steps in a single tool. It can drill, ream and bevel stacks made from CFRP and aluminium, in order to prepare then for riveting.