1、 When finishing turning the outer circle, there are chaotic ripples on the circumferential surface
Cause:
1. The raceway of the main shaft rolling bearing is worn.
2. The axial clearance of the main shaft is too large.
3. When the tailstock is used to support the workpiece cutting, the center sleeve is unstable.
4. When the chuck is used to clamp the workpiece for cutting, the internal thread of the chuck flange hole and the thread of the centering journal at the front end of the main shaft are loose, which causes the workpiece to be unstable, or the jaw is in the shape of a horn hole, which causes the workpiece to be clamped unstable.
5. The square tool rest is deformed due to clamping the tool, resulting in poor contact between the ground and the bottom plate of the upper tool rest.
6. The clearance between the sliding surfaces of the upper and lower tool holders (including the carriage) is too large.
7. The three support shafts of the tool box and the carriage box bracket are different, and the rotation is restrained (jamming phenomenon).
resolvent:
1. Replace the rolling bearing of the main shaft.
2. Adjust the clearance of the thrust ball bearing at the rear end of the main shaft.
3. Check the tailstock center sleeve, shaft hole and clamping device. If it fails to work, repair the shaft hole first.
4. Change the clamping method of the workpiece and use the tailstock to support cutting.
5. Scrape and repair the joint surface of the base plate of the square tool rest to achieve uniform and comprehensive contact.
6. Adjust the iron stopper pressing plates of all guide rail pairs to make them fit evenly and shake smoothly and easily.
7. Check the supports and remove and reassemble them if necessary.
2、 Finish turning the outer circular surface, with repeated corrugations every certain length
Cause:
1. The longitudinal cutter pinion of the carriage box is not meshed with the rack normally.
2. The smooth rod is bent or the mounting holes of the smooth rod, screw rod and tool walking rod are not on the same plane.
3. One of the transmission gears in the carriage box may be damaged, or the kneading caused by pitch diameter vibration is incorrect.
4. The shaft in the headstock and tool box is bent or the gear is damaged.
Solution:
1. Adjust the meshing clearance and make the gear rack mesh on the full width of the tooth surface.
2. The polished rod shall be removed and straightened; During assembly, keep the three holes coaxial and on the same plane.
3. Check and correct the transmission gear in the carriage box, and replace it if damaged.
4. Check the transmission shaft and gear, straighten the transmission shaft and replace the damaged gear.
3、 The outer diameter taper of cylindrical workpiece after machining is out of tolerance
Cause:
1. The unevenness of the headstock main shaft centerline to the moving guide rail of the slide plate is out of tolerance.
2. The inclination of the bed guide rail is out of tolerance or deformed after assembly.
3. The guide rail surface of the bed is seriously worn, and the straightness in the horizontal plane when the slide plate moves and the inclination when the slide plate moves are out of tolerance.
4. Because the center line of the spindle taper hole and the center line of the tailstock center sleeve taper hole are not on the same straight line.
5. The blade is not wear-resistant.
6. The temperature rise of the headstock is too high, causing the thermal deformation of the machine tool: the friction heat generated by the movement is absorbed by the lubricating oil and becomes a large secondary heat source. The heat is transmitted from the bottom of the headstock to the bed and the headstock, causing the temperature of the joint part of the bed to rise and expand, causing the thermal deformation of the machine tool.
resolvent:
1. Re calibrate the installation position of the headstock spindle center line to make the workpiece within the allowable error range.
2. Readjust the inclination of the bed guide rail with the adjusting shim.
3. If the straightness of the slide plate moving in the horizontal plane and the inclination of the slide plate moving are small, the guide rail surface is free of large-area scratches and can be repaired by scraping the guide rail.
4. Adjust the screws on both sides of the tailstock to eliminate the taper.
5. Trim the tool and select the spindle speed and feed rate correctly.
6. Properly adjust the oil supply quantity of the lubricating oil of the front bearing of the main shaft, replace the appropriate lubricating oil, and check whether the oil supply quantity of the oil pump is blocked.
4、 After finishing turning, the end face of the workpiece is convex
Cause:
1. The non parallelism of the center line of the headstock spindle caused by the movement of the slide plate is poor.
2. The upper and lower guide rails of the slide are not vertical.
resolvent:
1. Correct the position of the spindle center line of the headstock. On the premise of ensuring that the positive cone of the workpiece is qualified, the spindle center line will deviate forward, that is, to the tool rest.
2. Scrape and grind the guide rail surface of the slide plate, and make the outer end of the upper guide rail of the slide plate deviate to the headbox.
5、 When turning thread, the pitch is uneven and the thread is disordered
Cause:
1. The screw rod of the machine tool is worn and bent, the opening and closing nut is worn and the screw rod is different from the shaft, and the engagement is poor. The clearance is too large, and the opening and closing nut is unstable when it is closed due to the wear of the dovetail guide rail.
2. The clearance of the transmission chain from the main shaft through the change gear is too large.
3. The axial clearance of the screw rod is too large.
4. The male and British system handles are wrong, the fork position is wrong, or the change gear on the change gear frame is wrong.
resolvent:
1. Straighten the screw rod, adjust the clearance between the screw rod and the split nut pair, and scrape the dovetail guide rail to ensure the stability of the split nut when it is closed.
2. Check the meshing clearance of all transmission parts, and adjust all adjustable ones, such as change gears.
3. Adjust the axial clearance and play of the screw rod.
4. Check whether the handle, fork and change wheel are correct, and correct them if wrong.
6、 Ellipse or edge circle produced by workpiece
Cause:
1. The clearance of main shaft bearing is too large.
2. The ellipse of the main shaft journal is too large.
3. The main shaft bearing is worn, or the accuracy of the final gear of the main shaft is out of tolerance, and there is vibration during rotation.
4. The outer diameter of the main shaft bearing sleeve is elliptical or the shaft hole of the headstock box is elliptical, or the fitting clearance between the two is too large.
5. The thimble tip of the machine tool is worn off, or the thimble hole of the workpiece is not round.
Solution:
1. Adjust the clearance of main shaft bearing; If the lathe works at high speed, the adjusted clearance should be slightly larger; if it works at low speed, the clearance should be smaller. If the spindle clearance is adjusted according to the low speed, the phenomenon of holding the spindle may occur in the high-speed operation. Therefore, the speed range shall be adjusted according to the daily use specification of the lathe, and the general clearance shall be between 0.02 and 0.04 mm.
2. The Journal of the main shaft is polished to meet the requirements of roundness.
3. Scrape the bearing and replace the rolling bearing or the final gear.
4. If the out of roundness of the shaft hole is particularly poor, it shall be scraped round and straight first, and then repaired by "local nickel plating"; If it is a sliding bearing, it must be replaced with a new bearing sleeve.
5. Repair the ejector pin or workpiece ejector pin hole.
