Roll grinding vibration defects cause analysis and countermeasures

The production of cold rolled strip steel with high surface quality depends largely on rolls with high surface grinding quality.A cold rolling mill in the roll grinding process, the roll surface frequently appeared straight stripe vibration pattern defects, rolling process, the defects are further transferred to the strip surface, seriously affecting the product surface quality.

1 The causes of grinding vibration pattern
Grinding vibration pattern is generally in the low-speed rotation of the roll, side light observation is clearly visible, the reason is that in the grinding process, the grinding wheel relative to the roll there is a certain frequency of vibration. Caused by this vibration factors are more, grinding machine, workpiece, grinding wheel and grinding parameters are closely related to it, because the plant grinding parameters have been curing the use of many years, so mainly from the grinding machine, workpiece and grinding wheel several aspects of the reason to find.
2 Analysis of the causes of the grinding machine
2.1 Tile, bracket
(1) The bracket fixing bolts must be tightened;
(2) The upper (side) tile must be repaired to avoid contact between the curved surface and the roll neck, resulting in roll rotation instability;
(3) The lower tile is slightly curved, the outer side is high, the inner side is low, and keep the outer 2/3 for the roll contact center position;
(4) scrape off the black spots on the tile, black spots for the contact high point, high temperature oxidation caused by;
(5) Check whether the contact surface between the tiles and the tiles adjusting device is good (with red Dan powder), and grind the high point with sandpaper.
2.2 Grinding wheel spindle
(1) The radial and axial runout of the grinding wheel spindle and the concentricity of the spindle taper should be less than 0.005mm;
(2) Check the taper surface of the grinding wheel spindle for high spots and corrosion, and use metallurgical sandpaper to smooth it out;
(3) Check the tightness of the grinding wheel spindle belt, should not be too tight, too loose.
2.3 head frame
(1) Auscultate the headstock bearings to run without abnormal noise, and check the headstock belt tightness;
(2) Check the head frame dial and dial claw contact, dial contact surface is best wrapped with a certain thickness of rubber, to ensure the stability of the transmission.
2.4 Tailstock
During the grinding process, the contact between the tailstock and the roll should be loose and tight, too loose to cause axial runout of the roll, too tight to release the rotational force of the roll, which is prone to vibration.
2.5 Guide rail
(1) According to the guide rail grinding pattern state check the guide rail wear;
(2) The level meter detects the longitudinal level and transverse level of the guide rail, which is required to be less than ± 0.01mm;
(3) Check the cleanliness and level of the guide rail oil: v-rail guide rail oil level control in the v surface of 2/3 height; flat rail guide rail oil level high out of the rail surface of about 5mm, the middle of the screw guide lubrication rail oil level control in about half of the observation window.
2.6 Screw, silk mother
(1) Check the surface wear of the screw;
(2) Check the level of the screw, requiring less than 0.05mm;
(3) back and forth to open the grinding wheel tool holder, measuring the vibration of the screw, requiring less than 0.5mm tremor;
(4) Check the silk mother belt tightness;
(5) Check the cleanliness of the guide oil, focus on checking the oil with or without metal chips and water.
3 Analysis of the causes of workpiece
The influence factor of workpiece is mainly the round runout tolerance of the roll neck, which is less than 0.005mm and not more than 0.01mm, and excessive runout will easily cause grinding vibration.
4 grinding wheel analysis
(1) Check the grinding wheel material and hardness of any changes in the grinding wheel is too hard to cause grinding vibration.
(2) Check the static balance of the grinding wheel, dynamic balance characteristics. The centrifugal force generated by wheel imbalance makes the grinding wheel vibrate, and the frequency of vibration is equal to the rotating frequency of the grinding wheel, and the vibration acts directly on the workpiece, generating vibration patterns equal to the rotating frequency of the grinding wheel.
(3) Check the wheel flange. When the grinding wheel flange and the grinding wheel spindle taper contact is not
When the contact between the flange of the grinding wheel and the taper of the grinding wheel spindle is not good, the grinding process will make the grinding wheel oscillate irregularly, resulting in wheel runout.
5 Optimize the grinding process to improve the grinding surface quality
Through the detailed inspection of the above factors, it is found that the grinding machine of this factory has 0.5mm concave in the screw, serious chattering, and the amplitude of vibration is up to 5mm; the surface of the screw has obvious traces of abrasion, and a large number of metal shavings are found in the guide oil; the partial abrasion of the grinding wheel frame guideway is more obvious, and the track surface pattern is partially smoothed out, so it is judged that the vibration pattern is mainly caused by the wear and tear of the screw and the guideway. Since the replacement of the screw and guide rail scraping need to be dealt with during the overhaul of the grinding machine, in order to ensure the quality of roll grinding, the roll grinding parameters were optimized, basically eliminating the grinding vibration pattern and meeting the production needs.
(1) Reduce the grinding current and traverse speed of the drag plate at each stage of rough, medium and fine grinding.
(2) Add a few trips to the polishing program, and carry out grinding wheel fine dressing grinding before polishing, dressing feed 0.03mm, dressing 8 to 10 times.
(3) Set the grinding wheel rotational speed and roll rotational speed to change periodically during the grinding process, with the change amplitude set at 8 to 10% and the change cycle at about 60S, so as to change the regularity of vibration with obvious effect.

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