The accuracy of the horizontal axis of the CNC lathe processing machine tool spindle box and the vertical axis on the base determines the accuracy of the screw to be processed. At the same time, when the screw rotates at a high speed of several thousand revolutions in the compressor, the screw with low accuracy will cause compression. Machine heat, vibration, low efficiency, fast wear and so on. At present, my country's existing single-screw processing machine tool spindle structure roughly has the following two schemes.
Spindle structure with unadjustable bearing radial clearance
The double cylindrical roller bearing is combined with a pair of thrust ball bearings. The double cylindrical roller bearing is used to bear the radial cutting force, and two thrust ball bearings are used to bear the axial cutting force. A pair of double row cylindrical roller bearings or a pair of radial ball bearings, usually a pair of rear bearings. The advantages of this spindle structure: easy processing and assembly, and low cost.
Spindle structure with adjustable bearing radial clearance
The front bearing of the main shaft adopts a combination of double-row cylindrical roller bearings with P4 grade tapered bore and a P4 double-row radial thrust ball bearing. This paper proposes a double-row cylindrical roller bearing with tapered bore to withstand the radial cutting force, so as to withstand the axial cutting force and part of the radial cutting force. Usually, the rear bearing of the main shaft is a double cylindrical roller bearing with a P5 tapered bore.
The inner ring and the matching shaft diameter of the two-row cylindrical roller bearings are both 1:12 tapered. Locking the bearing with a round nut can cause the bearing to shift in the axial direction and expand the inner ring of the bearing to reduce or eliminate the bearing diameter. To the purpose of clearance.
The advantage of the spindle structure: high spindle accuracy. The measured runout value of the spindle end face is 0.010mm measured on the φ230mm diameter in front of the spindle. The radial jump value of the outer circle is 0.005mm, and the front end of the main shaft is φ230m. The spindle accuracy of this structure is about 50% higher than the former.
