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)rnlaminates and TiAl6V4 still need to be machined, whereby drill holes are frequently manufactured. Specialrnattention has to be paid to the machining quality, which implies dimensional accuracy as well as a defect-freernperipheral zone. Machining defects often occur as a consequence of excessive mechanical and thermal loads,rnwhich are often caused by wrong process conditions or by the wrong choice of machining process itself. Withrnrespect to widely used state-of-the-art machine tools providing high performance and equipped with potentrncontrol unit, for the comparatively large drill hole, circular milling gains interest as an alternative to the drillingrnoperation [1].rnAs a result of comparing drilling and circular milling for hole making of 6 mm diameter to carbon fiberrnreinforced plastic (CFRP) laminates and also 2-layer composite materials consisting of CFRP laminates andrnTitanium Alloys (TiAl6V4) using a vertical milling machine with CNC control, the author ascertained thatrncircular milling is superior to drilling concerning not only dimensional accuracy but also defects onrnperipheral zone [2], [3].rnThe author devised a new spindle applying double eccentric mechanism so that a cutting tool can rotate onrnits axis with high speed at clockwise simultaneously revolve on eccentric axis with low speed atrncounter-clockwise. The new apparatus, which has the double eccentric spindle driven by an air motor, designedrnand manufactured, and also hole making tests were executed to 2-layer composite materials consisting ofrnCFRP laminates and TiAl6V4 with cemented carbide end mill.