The research of technology of numerical control of grinding of stator curve nicety
- source:WILK CNC Machining
The control of 1 motion precision is politic to achieve taller athletic precision, use strategy of full closed-loop control. Principle block diagram is shown 2 times like the graph, the sharp movement that deputy changeover of nut of guide screw of electric machinery of driver of card of control of sport of control instruction classics, electric machinery, servo, ball is workbench. The athletic precision of workbench is controlled nut of guide screw of guide screw of electric machinery of card, driver, servo, ball, stretch shaft coupling, ball by motion deputy the combined influence that reachs a machine tool to the structure is designed and make precision, in working process, athletic precision is out of shape again further by oscillatory, heat, slideway and nut of ball guide screw wear away deputily the influence that reachs control component character to change. Use grating feet to feedback displacement signal to the input to carry, with the input signal undertakes comparative, implementation is controlled to athletic feedback. Graph block diagram of 2 full closed-loop control the real time position to obtain workbench (the position of real profile contrail nods) , the system used grating feet to undertake to X axis, Y axis real time is measured, have measured value and theoretical value comparative, obtain the error of integrated fixed position of fixed position workbench thereby. This testing system forms motion of a complete closed circuit to control a system. Contrail of Nextpage workpiece outline gives out by equation, the biggest interval that allows according to machining error undertakes to academic outline disperse is changed, get the interpolation of machine program is nodded. The coordinate value Xir that measures actually what nod according to every interpolation, Yir and academic coordinate are worth Xi, Yi, computation gives athletic error E, namely Ex=Xi-Xir, ey=Yi-Yir (1) goes to overlay of athletic error photograph the next interpolation of photograph adjacent chooses the place (Xi+1, yi+1) , generate new control to dictate (Xnew, ynew) , cut the accumulation besides fixed position thereby error. Xnew=Xi+1+ex, ynew=Yi+1+ey (2) wears away when emery wheel hind, undertake emery wheel radius is compensated even. About compensation of emery wheel radius, detailed introduction will have below. 2.
The 2 control strategy that wait for linear velocity grinding are in grinding process, the career that grinding chooses suffers the effect of the speed volume of emery wheel linear velocity and workbench, and the effect that emery wheel linear velocity suffers size of emery wheel radius. To assure grinding speed constant, use technology of communication frequency control, undertake compensating to emery wheel radius at the same time. Sketch map of process of grinding of the surface inside emery wheel and workpiece is shown 3 times like the graph. Graph the speed of 3 emery wheel and workbench of sketch map of workpiece grinding process is synthesized by the speed of X axis and Y axis workbench, namely in type of V my =Vx+Vy (3) , vx shows the rate of workbench X direction, vy shows the rate of workbench Y direction. Emery wheel rotate speed is controlled by electric main shaft, the linear velocity Vt of emery wheel by (4) type represents. In type, rt is emery wheel radius (Mm) , the rotate speed that Nt is emery wheel (R ／ Min) . In grinding process, workbench motion uses the interpolation method that waits for a pace to grow, the speed of workbench can consider as changeless, because the speed of this grinding dot suffers the effect of emery wheel linear velocity only. As a result of emery wheel wear away ceaselessly, of emery wheel radius reduce gradually, if the rotate speed of emery wheel is changeless, the linear velocity of emery wheel will be reduced gradually. To make sure grinding aspect rate is fixed, radius of emery wheel of statistical cipher out is fastened after nap emery wheel every time, the wear rate according to emery wheel comes to the actual radius of estimation emery wheel in the meantime, change the frequency that communicates transducer in real time thereby, adjust the rotate speed Nt of emery wheel, achieve the goal with emery wheel constant linear velocity thereby. 2.
Compensation of radius of 3 emery wheel because of emery wheel wear away, radius taper, influence by the outline appearance of grinding workpiece, accordingly, must undertake compensating to emery wheel radius. When the machine tool works actually, workbench makes planar motion, position of emery wheel center is not moved. According to the principle of opposite motion, below when the relation between center of derivation emery wheel and workpiece outline contrail, assume workbench is not moved, emery wheel center moves, if pursue,3 are shown. (Emery wheel of the Rti in 7) type is actual radius, rt0 does not have the radius when wearing away for emery wheel, d is the emery wheel wear extent of actual measurement, n is check the number of interpolation of workpiece outline contrail. Assume of emery wheel wearing away is even, by (7) type is calculable the actual radius that gives emery wheel to be nodded in each grinding. By type (5)-(7) but the central course after radius of cipher out emery wheel is compensated 4 mark. In machining a process actually, because emery wheel center is secured,do not move, workpiece is fixed go up in workbench, by (of 5) type turn over direction to move can. 3 conclusion used system of full closed-loop control to come true to have control and compensation to the athletic error of workbench, make athletic error control is inside permission range. Use transducer to come true to undertake adjustment to emery wheel rotate speed, those who make sure grinding nods linear velocity is constant, through emery wheel radius real time compensation reduces the error of outline contrail, assured the stability of grinding quality and consistency thereby. Precision of outline of workpiece grinding rear wheel and exterior surface roughness all achieve a design to ask, making clear this control strategy is feasible and effective. CNC Milling