Precision Point Grinding Technology For Steel Bonded Carbide Axles And On-Machine Conditioning Of Grinding Wheel

GT35 steel bonded carbide is widely used in many fields, like tools, dies, precision astronautic parts, etc. This material is a kind of typical material that is difficult to machine, because it is hard and brittle. The components need a high precision when used in these fields. Precision grinding needs high precision tools and proper grinding technologies. Therefore the conditioning of diamond grinding wheels and the study of grinding technologies are very important to the components precision. To fulfill the requirements, the property of GT35 is studied, and some principles are found. These principles are used to guide the grinding experiments. Cup wheel conditioner is designed to condition the diamond grinding wheel, which got high precision thin diamond grinding wheel and fine conditioning technology. The high precision diamond grinding wheel is used to grind GT35 axles, which got high precision.MT/NT indentation experiments are done for studying the mechanical property of GT35. The property of GT35 is studied, which revealed removal mechanism of GT35. In this study, GT35 is divided into hard phase and binding phase. Several indentation experiments are done. It is found that the hardness of hard phase and binding phase can be influenced by each other, the larger influence with the larger indentation size. The critical grinding depth for ductile grinding is got. The grinding cracks are observed, by which the critical ductile grinding depth is found.An on-machine cup wheel conditioner for diamond grinding wheel in cylindrical grinder is developed based on cup-wheel conditioning. This conditioner is controlled by PLC. Cup conditioning wheel is powered by DC motor. Besides it can move along the tangential of the diamond grinding wheel at a constant speed and it has a high precision feed along the radial direction. The feed precision can reach 1μm. This conditioner fit the grinder, and has a good working state.The form accuracy of diamond grinding wheel is in-process measured by laser displacement sensor. The microstructure of diamond grinding wheel is indirect measured by silica gel. Evaluating methods of diamond grinding wheel is developed. The conditioning technical parameters are obtained by conditioning experiments. Orthogonal experiments are done on 120-grits diamond wheel conditioning, by which good conditioning technical parameters are obtained. The parameters are used to condition the 600-grits diamond wheel. Finally, the circular run-out of the 600-grits wheel is 0.55μm, the straightness is 4μm.Conditioned thin diamond grinding wheel with a high precision is used to grind the GT35 axles, which get high precision workpieces. These experiments made a comparison of workpiece speed, feed rate and depth of cut. The influence of the three factors on workpiece is analyzed. The principles are obtained, by which the good grinding technical parameters are obtained. Meanwhile, a high precision workpiece is obtained which cylindricity is 0.34μm, roundness is 0.11 μm, Ra is 0.040μm. In the meantime, the material removal mechanism is analyzed. The bonded phase is mainly removed in ductile mode. Nevertheless, hard phase is removed in ductile mode and brittle mode. The predicting surface roughness function of GT35 is proposed and verified.