Robert Babiarz

Traverse grinding of low-stiffness shafts with the use of a grinding wheel’s path correction

This paper presents a method of increasing the shape and dimensional accuracy of low-stiffness shafts manufactured in traverse grinding process. In order to achieve that, grinding force measurement was used. It allowed to calculate such a correction of a grinding wheel’s path, that allowed to decrease dimensional and shape errors of grinded workpieces.

Cylindricity error measurement and compensation in traverse grinding of low-stiffness shafts

Axio-symmetric parts account for nearly half of the parts manufactured for the needs of the engineering industry. Among them, about 12% are shafts with low stiffness, i.e. those in which the length-to-diameter ratio l/d is greater than 10. They are used in many industries, including in the aviation industry (turbine shafts, spring shafts, elastic and torsional shafts), tool (drills, reamers, special tools), machine tools (rotor, pumps and generators shafts, guides) or automotive (driveshafts, axle-shafts) [1, 2]. Shafts with low stiffness are usually made of highstrength alloy steels. Typical methods of their machining include external turning and grinding. Turning machining should provide 8÷11. tolerance class and roughness Ra = 0.63÷2.5 μm, while grinding operation 5th or 6th tolerance class for roughness Ra < 0.63 μm [3]. The low stiffness of parts causes problems with achieving the required shape and dimensional accuracy. During grinding of such parts, elastic deformation occurs, resulting in errors in the cylindricity and dimension of the parts being made [4]. Many studies show that the pliability of the tailstock and headstock centers and the workpiece whose length / diameter ratio is greater than 10 is about 90% of the total machine tool – tool workpiece systems pliability [5]. Fig. 1 shows the elastic displacements of these elements. The elastic displacement of the workpiece x1, resulting from the displacements of the headstock center xw and the tailstock center xk can be calculated from the following equation: