In the process of machining precision mechanical parts, we are obviously more concerned about the accuracy. There is a kind of parts whose ratio of length to diameter is greater than 20. We call this kind of parts slender shaft. When turning precision slender shaft, under the action of cutting force and cutting heat, due to its poor rigidity, this kind of parts are easy to produce bending deformation. The middle of the slender shaft is thick and the two ends are thin, which affects the precision of precision mechanical parts.
At the same time, the bending deformation of the precision slender shaft will cause vibration, which will affect the surface roughness of the parts. When we process this type of parts, we need to take some measures to reduce this kind of deformation. When the clamping mode of one clip and one top is adopted, the elastic movable tip should be adopted to make the slender shaft stretch freely after being heated, so as to reduce its bending deformation when being heated.
At the same time, an open steel ring can be padded between the claw and the slender shaft, so as to reduce the axial contact length between the claw and the slender shaft, eliminate over positioning during installation, and reduce bending deformation. In order to reduce the influence of radial cutting force on the bending deformation of slender shaft, the clamping mode of one clamp and one top is adopted. Traditionally, the heel rest and center rest are used, which is equivalent to adding a support on the slender shaft and increasing the stiffness of the slender shaft, which can effectively reduce the influence of radial cutting force on the slender shaft.
But this method can't solve the problem that the workpiece is bent by the axial cutting force, so the axial pull clamp method can be used to turn the slender shaft. Specific operation: when turning a slender shaft, one end of the slender shaft is clamped by a chuck, and the other end is clamped by a specially designed clamping and pulling head, which applies axial tension to the slender shaft.
In the turning process, the slender shaft is always subject to the axial tension, which solves the problem of bending the slender shaft by the axial cutting force. At the same time, under the action of the axial tension, the bending deformation degree of the slender shaft caused by the radial cutting force is reduced, which compensates the axial elongation caused by the cutting heat, and improves the rigidity and machining accuracy of the slender shaft.
The reverse cutting method is used to turn the fine long shaft. The turning tool starts to feed from the spindle chuck to the tailstock direction. In this way, the axial cutting force generated in the processing process makes the slender shaft pull, eliminating the bending deformation caused by the axial cutting force. At the same time, the elastic tailstock tip can effectively compensate the compression deformation and thermal elongation of the workpiece from the tool to the tailstock, so as to avoid the deformation of the workpiece Bending deformation.
