The accuracy of the horizontal spindle and vertical spindle on the base of CNC lathe plus Machine Tool Headstock decide the accuracy of the processed screw. At the same time, when the screw rotates at a high speed of several thousand revolutions in the shrinking machine, the screw with poor accuracy will cause the shrinking machine to have fever, vibration, low efficiency, fast wear and other phenomena. At present, there are two plans for the spindle structure of single screw machining machine in China.
1: The main shaft structure with non adjustable bearing radial clearance
The front bearing of the main shaft is composed of one double row cylindrical roller bearing and two thrust ball bearings. The main shaft uses the double row cylindrical roller bearing to receive the radial cutting force and two thrust ball bearings to receive the axial cutting force. The rear bearing of the main shaft usually adopts one double row cylindrical roller bearing or one centripetal ball bearing. The advantages of the spindle structure: the processing and equipping of the spindle are simple and the cost is low.
2: Spindle structure with adjustable bearing radial clearance
The front bearing of the main shaft is composed of a P4 level tapered double row cylindrical roller bearing and a P4 level double row radial thrust ball bearing. The spindle receives the radial cutting force by using the double row cylindrical roller bearing with tapered hole and the axial cutting force and partial radial cutting force by using the double row radial thrust ball bearing. The main shaft rear bearing is usually a P5 level tapered double row cylindrical roller bearing.
The inner ring and matching shaft diameter of tapered bore double row cylindrical roller bearing are both 1:12 tapered. If the bearing is locked with a round nut, a displacement will occur in the axial direction of the bearing and the inner ring of the bearing will expand, so as to reduce or eliminate the radial clearance of the bearing.
The advantage of this spindle structure: high spindle accuracy. Measure the end face runout of the spindle on the diameter of φ 230mm of the front end face of the spindle to be 0.010mm. Measure the radial run out value of the spindle on the outer circle of φ 230mm at the front end of the spindle to be 0.005mm. The accuracy of the second structure is 50% higher than that of the first one.
