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 workpiece cutting, the center sleeve is unstable.
4. When the workpiece is clamped by the chuck for cutting, the workpiece is unstable due to the loose fit between the internal thread of the chuck flange hole and the centring journal thread at the front end of the main shaft, or the jaw forms a horn hole shape, which makes the workpiece clamped unstable.
5. The square tool rest is deformed due to clamping the tool, causing poor contact between its ground and the surface of the upper tool rest base plate.
6. The gap between the sliding surfaces of the upper and lower tool holders (including the slide carriage) is too large.
7. The three supporting shafts of the carriage of the knife box and the chute box are different, and the rotation is stifled (jamming phenomenon).
resolvent:
1. Replace the rolling bearing of the main shaft.
2. Adjust the clearance of the thrust ball bearing at the rear of the main shaft.
3. Check the tailstock center sleeve, shaft hole and clamping device. If it fails, repair the shaft hole first.
4. Change the clamping method of the workpiece and use the tailstock to support it for cutting.
5. Scrape and repair the joint surface of the square tool rest base plate to achieve uniform and comprehensive contact.
6. Adjust the plug iron pressing plates of all guide rail pairs to make them fit evenly and shake smoothly and easily.
7. Check the supports and disassemble and reassemble them if necessary.
2、 Finish turning the outer circle surface, and the ripples appear repeatedly every certain length
Cause:
1. The longitudinal knife pinion of the chute box is not meshed properly with the rack.
2. The polished rod is bent or the mounting holes of the polished rod, screw rod and knife walking rod are not on the same plane.
3. A transmission gear in the chute box may be damaged, or the kneading caused by pitch diameter swing is incorrect.
4. The shaft in the headstock and tool box is bent or the gear is damaged.
Solutions:
1. Adjust the meshing clearance and make the gear rack mesh on the full width of the tooth surface.
2. Remove and straighten the polished rod; Keep the three holes coaxial and on the same plane during assembly.
3. Check and correct the transmission gear in the chute box. If it is damaged, it must be replaced.
4. Check the transmission shaft and gear, straighten the transmission shaft, and replace the damaged gear.
3、 The outer diameter taper of cylindrical workpiece is out of tolerance after machining
Cause:
1. The unevenness of the moving guide rail of the headbox spindle to the slide 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 taper hole of the main shaft and the center line of the taper hole of the tailstock center sleeve are not in the same line.
5. The impact caused by the non wear resistance of the blade.
6. The temperature rise of the headbox is too high, causing the thermal deformation of the machine tool: friction heat is generated due to movement, and its heat is absorbed by the lubricating oil, becoming a larger secondary heat source. The heat is transferred from the bottom of the headbox to the bed and the head of the bed, so that the temperature of the joint part of the bed rises and expands, causing the thermal deformation of the machine tool.
resolvent:
1. Recalibrate the installation position of the headstock spindle center line to make the workpiece within the allowable error range.
2. Use the adjusting sizing block to recalibrate the inclination of the bed guide rail.
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 has no large area of scratches, which can be repaired by scraping and grinding the guide rail.
4. Adjust the screws on both sides of the tailstock to eliminate the taper.
5. Trim the tool, and correctly select the spindle speed and feed rate.
6. Properly adjust the oil supply of the lubricating oil of the front bearing of the main shaft, replace the appropriate lubricating oil, and check whether the oil inlet 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 spindle centerline of the headstock caused by the movement of the slide is poor.
2. The verticality of the upper and lower guide rails of the slide is poor.
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 deviates forward, that is, to the tool holder.
2. Scrape and grind the guide rail surface of the slide board, and make the outer end of the upper guide rail of the slide board lean towards the headbox.
5、 Uneven pitch and disordered lines when turning threads
Cause:
1. The lead screw of the machine tool is worn and bent, the opening and closing nut is worn, and the engagement is poor due to different shafts from the lead screw. The clearance is too large, and the opening and closing nut is unstable 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 English handles are hung incorrectly, the shift fork is in the wrong position, or the change gear on the change gear rack is hung incorrectly.
resolvent:
1. Straighten the screw rod, adjust the gap between the screw rod and the split nut pair, and repair 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 everything that can be adjusted, such as change gears.
3. Adjust the axial clearance and movement of screw rod.
4. Check whether the handle, fork and change gear are correct. If it is wrong, correct it.
6、 Workpiece produces ellipse or edge circle
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 fit 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.
Solutions:
1. Adjust the clearance of the 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 at low speed, the phenomenon of holding the spindle may occur in high-speed work. Therefore, the speed range should be adjusted according to the daily use specifications of the lathe, and the general gap should be between 0.02~0.04 mm.
2. Grind the Journal of the main shaft 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, scrape it round and straight first, and then repair it by "local nickel plating" and other methods; 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.