Research On The Technology Of High Efficiency Lapping Method Of Hard Material Sphere

Hardness material (such as silicon nitride ceramics and sintered-carbide ) sphere is considered as one of the most important element for high precision bearing, roundness measuring equipment, top and other high precision machine tool and apparatus because of its desirable properties. They have been successfully used in many fields such as precision machine, aerospace and military instrument, especially in hybrid bearings (ceramic balls and steel races).In this paper, a new type of high efficiency lapping method for high precision hardness material sphere is developed to overcome limitations in traditional lapping process, such as low precision and efficiency, low uniformity and stability of process. Fixed abrasive lapping technology is adopted to lap hardness material sphere in rough-machining stage; Rotated Dual-Plates (RDP) lapping technology is employed to improve hardness material sphere precision and consistency in semi-finishing stage and CMP (Chemical Mechanical Polishing) technology is used to improve high surface quality in finishing stage. The above new style lapping machines have been designed and being manufactured in Ningbo Fenghua Xikou Kaitai Precision Machinery Factory.Lapping trace distribution on ball surface is studied with observing the marked points on the ball surface and 3D simulation of lapping trace. The influence of loading system, lapping parameters and lapping tools on sphere-shaping process is discussed with experiments and theory analysis to study the mechanisms of sphere error correction. The wear mode of hardness material sphere involved in the lapping process is also investigated in this paper. Abrasion tests are performed with different grit size, loads and slurry concentrations on a ball-plate wear test apparatus.In the final part of this paper, silicon nitride ceramics balls are taken as object of a high efficiency lapping experiment .As a result of the experiment, fine sphericity (0.05μm), surface finish (Ra 5nm) and batch diameter variance (0.10μm) are obtained with the total lapping time reduced to about 1/2 of traditional lapping process.