Toshio Kasai

Improvement of Parallelism in Lapping or Polishing using Eccentrically Distributed Loading

Eccentrically distributed loading for the improvement of parallelism in lapping and polishing is proposed. The typical additional weights used for a circular plate work are made by cutting a column at an angle. The centers of gravity of these are at one quarter of the distance from their geometrical center to the foot of the maximum height. Therefore, it is unnecessary to calculate the loading position taking into account the weights of the work and the eccentric load, contrary to a conventional concentrated loading. In lapping, three kinds of eccentrically distributed weights were used, and the deterioration and the improvement of parallelism were repeated by replacing their maximum height positions in 180° direction at 5minutes intervals. This procedure is found to be simpler and more reproducible. In polishing, parallelism was improved better than 1 second without any deterioration of flatness as polishing advances. Moreover, the parallelism of the individual small bits of work fixed on a plate jig using two kinds of waxing methods were compared after lapping and polishing.

Deformation of Magnetic Disks made of Aluminum Alloy Plate and Electroless Deposited Nickel Films

Magnetic disks made of aluminum alloy and electroless deposited nickel film have residual stresses due to lapping and plating. This paper reports on theoretical analysis for deformation of disks due to residual stresses. Numerical values calculated by induced equations are in good agreement with flatness values on model disks, which are lapped after electroless nickel plating on one side of the aluminum alloy. Experimental results show that plating stresses and residual stresses by lapping on deposited films depend on the respective values of pH in plating bath and grain size. Depth of worked_ layers on deposited films is extremely small, compared with the case of aluminum alloy. Simulation results on the deformation of 360 mm.diameter plated magnetic disks show that the amont of deformation is 140-200 μm for 50% unbalanced ratio of plating thickness and depth of worked layers on both surfaces.

Kinematical Analysis on Newly Designed Machine for Magnetic Memory Disk

Kinematical analysis on lapping a ring shaped plate with a circular tool is carried out and numerical equations on stock removal are obtained, taking into account distributed pressure due to the moment of inertia of the area contacted for both work and tool and due to the eccentric load. A newly designed machine, in which distributed presssure is able to be adjusted with eccentric load due to tool weight, was also built. Experimental stock removal, flatness and parallelism values on 360 mm diameter - 2 mm thick aluminum plates for magnetic memory disk, made by the machine, are in agreement with calculated values. In consequence. procedure deducing the equations is found to be satisfactory. The machine obtained here are not only applied to lapping, but are capable of being applied to mirror-polish the surfaces, plated electroless deposited nickel on an aluminum disk.

Deformation of Aluminum Alloy Plates for Magnetic Disks

It is difficult to obtain a high degree of flatness on thin aluminum alloy plates because of residual stress by lapping. This paper reports on theoretical analysis of deformation of disks at various thicknesses. The residual stress is seperated into original stress due to lapping and secondary stress caused by deformation depending on thickness. Equations calculating the amount of deformation of circular plates using the former stress are then induced. Experimental results determined by measurements made while removing successive uniform thin layers in various lapping conditions show that depth of worked layers and distribution of residual stresses depend on grain size. Numerical values calculated by the above equations are in good agreement with flatness values on 70 mm diameter lapped model disks.

On the Effect of Polishing Liquid in the Glass Polishing Operation:On the Polishing of Glass (III)

Various kinds of liquid were applied as polishing liquid in the glass polishing operation, using acrylic resin as polishing plate and cerium oxide as polishing powder. Then, it was found that glass is able to be polished satisfactorily without water, and that liquid with smaller viscosity has larger efficiency at the same conditions for polishing of glass.