(1) Form grinding. In form grinding, the main cause of burn is the annealing burn caused by the accumulation of grinding heat and the inability of coolant to enter. The annealing burn causes the hardness of the thrust surface of the crankshaft to decrease, the surface to produce annealing structure, and the wear resistance of the thrust surface to deteriorate, which seriously affects the operation stability of the engine. According to the main factors that cause burns, we start from three aspects: choosing the right grinding wheel, choosing a reasonable grinding allowance and improving the cooling conditions.
① Choose the right grinding wheel. The hardening steel crankshaft thrust surface has high hardness and large area, and the sand is easy to dull. In order to avoid a large amount of grinding heat caused by dull sand, the hardness of the grinding wheel should be soft, so that the dull sand can fall off in time and maintain the self-sharpness of the grinding wheel. A wheel with a softer texture has more pores, which can contain chips, avoid clogging of the wheel, and can bring coolant or air into the grinding area, thereby reducing the temperature of the grinding area.
On the premise of ensuring the roughness of the thrust surface of the crankshaft, it is appropriate to choose a coarse-grained grinding wheel to achieve a higher removal ratio. In addition, the grinding wheel must be finely balanced so that the grinding wheel is in a good balance when working; The grinding wheel must be trimmed in time to maintain its sharpness; There are many factors that affect the dressing frequency of grinding wheel, including the purity and type of grinding material, the clarity of coolant, etc. The diamond support of the dressing wheel must be firm, if there is a wear amount of 0.5~0.6mm on the diamond surface, indicating that the diamond has been blunted, should be replaced in time; Strictly control the clearance of wheel drive system and wheel mandrel; Wheel belt tightness adjustment is appropriate.
② Select reasonable grinding allowance and grinding parameters. In production practice, it is often used to increase workpiece speed and reduce radial feed to reduce workpiece surface burns and cracks. One experience is the 0.1mm grinding method, that is, in the 0.1mm margin of the final processing, the feed amount is gradually reduced, and the surface damage layer generated in the first two grinding strokes can be removed to reduce grinding burns.