The Influence of the Temperature of the Elements of the Lapping Machine Executory System on the Results of the Lapping Process

Abstract

Commonly used as a finishing operation, lapping has been applied for achieving ultra-high finishes and close tolerances between mating pieces. It can be carried out by applying loose abrasive grains between work and lap surfaces, and causing relative motion between them resulting in the finish of a multi-directional lay.The activity of grains (sliding and rolling) in the working gap causes not only the removal of the material but also a rise in the temperature of the lap plate. The authors of this work analyse the influence of the temperature of the elements of the lapping machine executory system on the results of the lapping process stimulated applying ABRALAP 380 lapping machine the executory system of which consisted of three working conditioning rings. The temperature of the elements of the executory system was measured employing Thermo Gear G100 infrared camera. The workpieces were ceramic (Al2O3) valve sealing parts. After grinding, they were being lapped during 15 and 20 minutes. Machining was started following 10, 140, and 270 minutes of the working time of the machine (tp). The abrasive mixture was boron carbide powder with grain number F400/17, mixed with kerosene and machine oil with grain concentration equal to m = 0.25. Two sets of lapping parameters were executed:lapping pressure p = 0.051 MPa, and lapping speed v = 27 m/min;lapping pressure p = 0.03 MPa, and lapping speed v = 38 m/min.The rate of material removal in g and mm and roughness parameters Raand Rkof the surface were analysed.The conducted studies showed that the temperature of the elements of the machine executory system affected only parameter Rawhich is higher for the surfaces that were processed starting from the 270thminute of the working time of the machine. Only a slight increase in the values of parameter Rawas observed. It can be caused by a change in conditions for the process of material removal due to different properties of grain carrier under a higher temperature. Its viscosity decreases with an increase in temperature, which implies direct interactions between the plate and workpiece surface. Normally those two surfaces interact indirectly via abrasive grains. The rest of the tested lapping results were independent of the temperature of the elements of the lapping machine executory system. The values obtained under different temperatures were almost the same.