Key Engineering Materials Vols. 447-448

Abstract: Surface integrity is particularly important for the aerospace industry components in order to permit longer service life and maximized its reliability. This present work compares the performance of palm oil and synthetic ester on surface roughness, surface defect, microhardness and subsurface deformation when high speed drilling of Ti-6Al-4V under MQL condition. The drilling tests were conducted with AlTiN coated carbide tool. The surface roughness decreased with increasing in cutting speed and thicker subsurface deformation was formed underneath the machined surface. Grooves, cavities, pit holes, microcracks and material smearing were the dominant surface damages thus deteriorated the machined surface. For both lubricants, the machined surface experienced from thermal softening and work hardening effect thus gave a variation in microhardness values. The results indicated the substantial benefit of MQL by palm oil on surface integrity.

Abstract: In the recent years, the current technology enables only the molten iron base alloys, sprayed on the aluminum alloy engine block thus it can function as a cylinder bore. However, the machinability performance of plasma spray coated cylinder bore in boring process is poor because of severe tool wear compared with the previous cast iron cylinder bore. This paper deals with the results obtained at boring process of plasma sprayed iron base alloys coating to clarify the root cause of tool wear. Preliminary fine boring and turning experiments are conducted on the plasma sprayed cylinder bore, and tool wear, tool failure modes and cutting force were also investigated. The result shows plasma spray coated cylinder bore recorded larger cutting force than the cast iron cylinder bore. Also, this work shows that abrasive effect by the hard oxide particles on the cross-sectioned of machined layer is superior when fine boring plasma spraying iron base alloys coating.

Abstract: Parallel mechanism has many advantages, such as high stiffness, high accuracy, high degree of freedom (DOF), etc. These fine features are suitable for work table of machine tools for production of recent complicated designs. In this study, six axes linear-actuated parallel mechanism was chosen as the basic design for work table. First, geometrical parameters of the table were designed to satisfy the required movable range with minimum cutting load. Then, the work table was actually constructed and its performance was evaluated. From positioning accuracy measurement, it was found that the table is suitable to be used for machining of complicated products. On the other hand, from actual cutting tests of primitive shapes using chemical wood and measurement of the machined shapes, potential of the table for real cutting application was confirmed.

Abstract: Open architecture NC orienting MEDM application was studied and the “IPC + UMAC motion controller” architecture was presented. And then, the integration method and principle, that the motion system, WEDG (Wire Electrical Discharge Grinding) system, coolant system, visual supervising and measuring system, micro-energy pulse Generator with NC, were investigated. Based on the PComm32, control software with general NC machine tool HMI style, was developed and whole machine tool was integrated successfully. At last, a lot of experiments were carried out, and the results demonstrated that the MEDM machine tool has the capabilities of manufacturing micro- electrode, micro hole, complex 2D micro workpiece and milling 3D model.

Abstract: A drilling technique using micro-drills of 0.2 mm or less in diameter and a super-high-speed spindle of 160000 rpm or more has been developed for drilling ultra-micro holes in printed wiring boards (PWBs). The drilling process requires higher reliability and quality to maintain the reliability of the electrical connection between circuit layers. On the other hand, higher processing efficiency is also required in PWBs manufacturing. To maintain high productivity, drilling is normally performed using a non-step method, but heat damage called B-RING occurs around the drilled holes with this method. To solve these problems without the loss of processing efficiency, we applied the rapid-feed step-drilling cycle method. We investigated the B-RING for drilling quality and evaluated the drilling time for processing efficiency under various drilling conditions. We found that using a rapid-feed step-drilling cycle with an appropriate number of steps and feed rates ensures a higher level of hole quality and processing efficiency compared with the conventional non-step drilling.