Bearing grinding machine stepper motor and its control system
China in bearing grinding machine adopts stepper motor and its control system began from the ninety s, more than a decade, the stepper motor control technology of bearing grinding machine development soon, at present, wuxi, shijiazhuang, chengdu and henan bearing equipment manufacturing factory of the few cities in the mass production of bearing grinding machine of stepper motor control. With large quantities of stepper motor control of the bearing grinding machine to the market, step motor system control problems are more and more surfaced, problems of single axis stepper motor control system is less, but more than two axis stepper motor system, often appear, such as the two systems are not synchronized, dimensions such as poor dispersion unstable failure. Stepping motor system there are many problems.
We worked in the ball bearing inner ring groove grinding machine analysis and study, I tried the domestic several brands of stepper motor, found that the two systems are not synchronized phenomenon is serious. Sync error test from PLC, a control module, stepper motor drive and stepper motor. Ball screw lead 4 mm, harmonic reducer reducer ratio of 1:8 0, step torque Angle is 0.9 °, pulse equivalent of 0.125 microns. Stepper motor repetitive positioning error is more than three times as many machine tool precision inspection standards. According to the pulse equivalent to 0.125 mu m, workbench cumulative repeat positioning error in 20 times has reached 0.003. The data of table 1 shows that not only is the error of the stepper motor, the error of the mechanical system more obvious. We analyzed this machine tool feed mechanism and compensation mechanism, found that the mechanical problems are more serious. First, the ball screw small nominal diameter (Φ 20), precision grade 3 level is low, and feels the crawling phenomenon is relatively serious; Second, feed jump oil cylinder and ball screw design positioning, cannot eliminate assembly location deviation; Third, harmonic gear reducer and ball screw only screw locking no key connection or pin link; Fourth, there is no ball screw bearing and so on.
And then we analyzed the electrical system of the machine tool, found the inverter, transformer and stepper motor controller put nearly circular, PLC output cable, cable shielding, not PeiPan high voltage and low voltage cable, orange, and so on. These problems are factors influencing the stepping motor system is not stable. Because at present our country the anti-interference ability of the step motor system is poorer, the electrical design layout of the unreasonable directly produces contingency and error compensation system, feed system and mechanical system, the systematic error of machine tool is in unstable working condition. Is not to say that as long as the machine tool hydraulic feed compensation system into a stepping motor feed compensation system, the comprehensive performance of machine tool will be improved significantly. Stepper motor to replace the original complex hydraulic feed compensation system, the original hydraulic pressure fluctuations and eliminates the mechanical parts processing of transmission chain error, and feeding process of step motor can is divided into several stages, each stage can choose different pulse frequency control of feed speed, can use the pulse number to control the machine tool working platform, diligence to it than the original hydraulic system of bearing grinder progress a big step.
But, it followed the other related machine parts also need to follow to update design, to satisfy the requirement of the machine tool grinding technology. Both the design of the mechanical structure and electrical system design should not ignore the stepper motor system characteristics of the anti-interference ability is weak. If we were more than the solution of the problem is not properly solved, if the overall machine tool parts, especially the key parts or the original mechanical hydraulic system of machine tool of standard, adopt stepper motor control system of bearing grinder will not fundamentally improved. Of course, the most thorough way is to adopt the most advanced servo motor control system. Adopt servo motor control system of bearing grinder, will jump oil cylinder and harmonic reducer is removed, the ball screw and servo motor structure, makes the minimum error of mechanical system. Although our country still adopt servo motor control system of bearing grinder pulse control, but the servo motor drive ability, comprehensive repositioning precision and anti-jamming ability, than of the stepper motor bearing grinding machine and a huge step forward.
Due to the characteristics of step motor system and many BUG, it's just a mechanical hydraulic control progress to the servo system control in the middle of a transitional product, now rarely see abroad adopt stepper motor control system of the precision grinding machine, our country is in the numerical control machine tools on the application of step motor system time longest countries. With China's bearing industry technological upgrading can speed up, as more and more processing high quality bearing enterprise's development, the stepper motor control of bearing grinding machine will eventually be replaced by servo motor.
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