Development of Hole Making Apparatus based on Double Eccentric Mechanism and its Capability in the case of Bi-Layer Composite Materials consisting of CFRP Laminates and Titanium Alloys

摘要

Construction parts consisting of 2-layer composite materials made of carbon fiber reinforced plastic (CFRP) laminates and TiAl6V4 still need to be machined, whereby drill holes are frequently manufactured. Special attention has to be paid to the machining quality, which implies dimensional accuracy as well as a defect-free peripheral zone. Machining defects often occur as a consequence of excessive mechanical and thermal loads, which are often caused by wrong process conditions or by the wrong choice of machining process itself. With respect to widely used state-of-the-art machine tools providing high performance and equipped with potent control unit, for the comparatively large drill hole, circular milling gains interest as an alternative to the drilling operation [1]. As a result of comparing drilling and circular milling for hole making of 6 mm diameter to carbon fiber reinforced plastic (CFRP) laminates and also 2-layer composite materials consisting of CFRP laminates and Titanium Alloys (TiAl6V4) using a vertical milling machine with CNC control, the author ascertained that circular milling is superior to drilling concerning not only dimensional accuracy but also defects on peripheral zone [2], [3]. The author devised a new spindle applying double eccentric mechanism so that a cutting tool can rotate on its axis with high speed at clockwise simultaneously revolve on eccentric axis with low speed at counter-clockwise. The new apparatus, which has the double eccentric spindle driven by an air motor, designed and manufactured, and also hole making tests were executed to 2-layer composite materials consisting of CFRP laminates and TiAl6V4 with cemented carbide end mill.