Grinding process improvement of CNC roll grinding machine
The CNC roll grinding machine is an important supporting equipment for the production of plate rolling, and its grinding accuracy and grinding efficiency directly affect the quality of plate rolling and production efficiency. The grinding mechanism has the characteristics of a large cylindrical grinding machine, but is much more complex than the movement of a cylindrical grinding machine, which requires relative longitudinal movement of the grinding wheel and workpiece in addition to the relative rotary movement of the grinding wheel and workpiece. In order to meet the process requirements for plate shape control, the roll surface bus needs to be processed into various special high-squares curves (such as CVC curves) in accordance with different process requirements. This requires the grinding wheel of the CNC roll grinding machine, the workpiece for the relative longitudinal movement of the two for a certain radial relative displacement. The requirements for the transmission mechanism of CNC roll grinding machines are therefore very high, as are the requirements for the working accuracy of the machine tool. At the same time, good grinding process parameters as well as grinding wheels and coolant is also an important guarantee of roll grinding accuracy and surface quality.
(1) Improve guideway precision.
According to the accuracy requirements of the bed V-guide, bed flat guide, drag plate seat V-guide and drag plate seat flat guide, scraping and grinding of the guide is carried out to improve its contact accuracy.
(2) Improve the transmission accuracy of the screw by adjusting the preload and axial clearance of the ball screw For CNC grinding machines, ball screws are commonly used for transmission. Therefore, the transmission accuracy of the ball screw has a great impact on the machining accuracy. Taking the double nut adjustment method as an example, the mechanical adjustment aspect can adjust the clearance of the individual nut mounted to the screw, and the axial clearance is generally adjusted to about 0.005 mm. After the nut clearance has been adjusted, the shims are fitted. If the torque is within the required range of the drawing, the shim is ground according to the size of the block; if the torque is not within the required range of the drawing, the block is replaced and the torque is measured again until it meets the requirements. In addition, the backlash compensation parameters of the CNC system can be used to compensate for the clearance of the screw, thus improving the transmission accuracy of the ball screw.
(3) Improve the accuracy of the grinding wheel spindle bearing.
For the dynamic pressure bearing, the shaft tile is repaired and scraped, so that the contact point reaches 12~14 points/25mm×25mm, thus ensuring that the clearance between the grinding wheel spindle and the shaft tile is adjusted to 0.0025~0.005 mm. while for the static pressure bearing, the front and rear bearing oil cavity pressure is checked to ensure that the clearance reaches 0.0025~0.005 mm. Radial runout is 0.001~0.002mm.
(4) Balance the grinding wheel to improve the machining accuracy static balance: after the grinding wheel piece is installed on the flange, the grinding wheel is installed on the grinding wheel spindle and after diamond pen dressing, the grinding wheel is taken off and put on the balance frame for static balance. The method is to adjust the three adjustment blocks in the direction of the flange circumference so that the grinding wheel can be stopped in the four 90° positions of the circumference on the balancing frame. Through good static balancing, reduce the impact of grinding wheel imbalance on machining accuracy. Dynamic balancing can also be carried out if necessary: after the grinding wheel is installed to the grinding wheel spindle, a dynamic balancing device is installed on the flange so that the centre of gravity of the grinding wheel is offset by ≤0.2μm.
(5)Reasonable choice of lubricating oil for the guide rail to improve the lubrication of the guide rail and avoid crawling phenomenon.
(6) Reduce heat generation and improve machining accuracy through the use of live centres.