Precision slender shaft parts play an important role in precision machining, and the accuracy of cylindrical is usually guaranteed by cylindrical grinder. Due to the large difference between the length and the diameter of the shaft. And in the grinding process, slender shaft precision parts are prone to bending, waist drum shape, polygonal, conical, elliptical and spiral ripple defects. The quality requirements of grinding usually directly determine the success or failure of the whole product. Due to the poor rigidity of the slender shaft, the deformation should be avoided as far as possible in the grinding process.
Slender shaft usually refers to the shaft parts whose ratio of length and diameter is greater than 20. It is widely used, such as the pull rod, screw, piston rod in the injection molding machine. The precision machining process of shaft directly affects the product quality of the whole machine. Therefore, it is of great significance to study the machining of this kind of precision parts. Due to the poor rigidity of the slender shaft, 3-5 center frames must be evenly distributed in the symmetrical position when grinding the slender shaft. Because the size of the workpiece will change every time the precision parts are processed by longitudinal grinding, the top holding of the center frame must be adjusted accordingly. Therefore, it is necessary to pay attention to the change of the top holding of the supporting claw of the center frame to the workpiece at all times. If necessary, it is even necessary to use the V-shaped wooden hammer handle to follow the grinding wheel for longitudinal grinding, that is, the tracking top holding method.
Before finishing grinding of precision mechanical parts, the grinding wheel must be finished for the last time. It should be fed from the right side of the grinding wheel to make the left corner of the grinding wheel sharp and sharp. The periphery of the grinding wheel can be modified into a concave shape to reduce the radial force. The size of each center frame part should be finely ground to meet the tolerance requirements, and the outer circle should be finely ground. At this time, we still need to pay attention to the top holding of the center frame. If necessary, we even need to use the V-shaped wooden hammer handle to follow the grinding wheel for longitudinal grinding. Measure with a micrometer, adjust the clamping force of the center frame repeatedly and grind the outer circle of the shaft to meet the tolerance requirements of the workpiece. Finally, it is necessary to pay attention to non feed grinding for several times to reduce the surface roughness of precision machining.
Grinding is a process of using grinding wheel to remove fine chips on the surface of workpiece at high linear speed. The main reasons are as follows: first, the cutting force factor, that is, the vibration caused by the bending of slender shaft due to the poor rigidity of cutting force, which affects the machining accuracy and surface roughness of precision mechanical parts. The second reason is the deformation of grinding center before and after quenching and tempering. The third is the cutting vibration factor, that is, the centrifugal force generated by the high-speed rotation of the workpiece will aggravate the bending and vibration. Therefore, the key technology of grinding slender shaft is to improve the supporting rigidity of precision parts and reduce the grinding force and grinding heat. The operation skills of grinding on the ordinary cylindrical grinder and the reasonable use of multiple center frames to track and hold to control the deformation can better improve the deformation and defects that are easy to appear in grinding and improve the production efficiency.