This study was performed to investigate a method of fabricating WC-Co alloy cavity inserts for polymer aspherical lens molds using ELID grinding. First, we ground the cavity insert using a cast iron bonded wheel and then carried out injection molding of the lens using the cavity insert. The grinding marks and tool marks on the grinding surface of the cavity insert were faithfully transcribed onto the molded product, indicating that these marks cause external defects. To resolve this problem, we attempted finish-grinding of the cavity insert using a conductive rubber bonded wheel and successfully obtained high-quality ground surface properties with no grinding and tool marks.

View full abstract

Studies of surface grinding indicated that shape changes occur at both sides of a work piece where the grinding process begins and ends. This study was performed to analyze the emergence of these shape changes. Focusing on the grinding volume per unit time and the normal grinding force, a theoretical formula for calculating the shape-generating process in surface grinding was derived. By setting the appropriate calculation conditions, it was possible to nearly reproduce the shape changes near both ends of the work piece that appeared in the grinding experiment characterized by differences in the processing conditions.

View full abstract

In the polishing process, the removal rate is strongly dependent on the pad surface asperity. We have developed a quantitative evaluation method based on contact image analysis using an image rotation prism. This paper discusses the effects of pad surface asperity on removal rate for Si wafers based on various polishing tests. The results indicated a high removal rate for the following case: number of contact points, 30/mm²; contact ratio, 0.8%; maximum value of the minimum spacing of contact points, 450 μm; and half-width of the peak of spatial FFT, 100 μm. Furthermore, the maximum value of the minimum spacing of contact points was the most effective parameter as determined by multiple correlation analysis for four evaluation parameters.

View full abstract

To machine 3D micro-geometric features with a high-quality surface in ductile mode on fused silica using micro-PCD end mills, a study was performed to understand the micro-milling process of fused silica and to determine the factors influencing machining quality. The results of this experiment indicated that the most important influencing factor for machining of a ductile mode surface was the cutting force in the Z direction applied to the machining surface. Under the conditions used in this experiment, when the cutting force per unit area of Z direction was less than 2500 N/mm², a ductile mode machining process was always generated, and the average surface roughness was typically 5 nm with maximum surface roughness of 40 nm. Detailed observations of the bottom of the tool by atomic force microscopy were conducted from a morphological viewpoint. It was concluded that the existence of favorable PCD micro-diamond grains and voids distributed over the surface may act to create a micro-grinding effect. Using the obtained cutting conditions, the micro-well was machined and high-quality surface on the bottom of well was successfully generated.

View full abstract

This study was performed to develop high-performance honing for finishing the inner surface of machine parts holes. This new honing method converts the emitted axial ultrasonic vibration of the transducer into radial vibration and uses this radial vibration for in-feed motion of the honing stone. In the honing of hardened steel, the size generation rate changed in response to changes in the radial vibration amplitude of the honing stone. In addition, the honing method improved the honed surface quality.

View full abstract