The Research On Mechanism And Technology For Laser Truing And Dressing Of Bronze-bonded Diamond Grinding Wheels By Acoustic-optic Q-switched Nd: YAG Pulsed Laser

With excellent grinding performance, the Bronze-bonded diamond wheels have a wide application prospect in the field of precision, ultra-precision, high efficiency grinding, grinding automation and difficult processing material forming. In recent years, Because of the breaking through of the grinding wheels manufacture question and the Increasing application to difficult processing materials such as ceramics, glasses and so on, Bronze-bonded diamond wheel's application growth sharply. Because of the ultrahigh hardness of diamond, It's difficultly for traditional truing and dressing method which was based on the interacton of force to promot.which really affects the grinding performance of Bronze-bonded diamond wheels, and also is the key problem which up to now not solved completely in the accurate numerical controlling grinding machines. A new method which to solve Bronze-bonded diamond wheel's truing and dressing problems fundamentally truing has attracted much attention all over the world .This article summarized the present research situation on domestic and foreign countries. Embark on the essence of Bronze-bonded diamond wheel's truing and dressing,to pointed out the key question: found methods to remove micron level diamond directly and effectively; and also can removed selectively, enhanced the precision effectively; simultaneously can break through the tradition concept. The traditional methods which based on strength and electricity cannot remove the diamond effective directly. The ideal method is which item was based on the accurate laser machining with little heat effec.The author has carried out the research comprehensively from the theory and the experiment.Fist, with high peak power, low duty ratio, short pulse duration, high repetition frequency and controllable feature, the acoustic-optic Q-switched pulsed laser is considered to be suitable for truing and dressing Bronze-bonded diamond wheels. An acoustic-optic Q-switched Nd:YAG laser has be developed and tested independently. Through measured the maximum average power is 100W; the minimum pulse duration is 170ns; the repetition frequency is 0.5~50kHz.Next, in order to seek the appropriate laser ablation parameters of bonds and abrasives, this causes the abrasives to have not micro crack after ablation, to get shallow deterioration level, to have good grinding performance under ablation, and also to obtain Better surface topography after truing and dressing. Theory and experiment study has separately carried on bonds and abrasives and Bronze-bonded diamond wheels with single pulse laser ablation. The single pulsed laser ablation power density threshold value of bonds and abrasives has determined through theoretical calculation. Indicated that the acoustic-optic Q-switched laser can be possible to remove diamond and bronze in effectively. The mathematical model of the unit crystal diamond pulse laser ablation has been established. Through analog computation, obtained the result those pulse duration and duty ratios are the most primary factor for the deterioration level thickness and the superficial micro crack. And through experimental confirmation, the appropriate laser ablation parameter had been found. The actual process of pulsed laser ablation on a bronze bonded diamond wheel is extremely complex. Just for wheel (but is not alone aims at bonds or abrasives) the two-dimensional geometry model and mathematical model both has been established to simulate the ablation situation. Meanwhile, through experiments can determine that when the laser average power density is lower than 30×107 W/cm2, only dressing can be carried on. But after the laser average power density achieved 30×107 W/cm2, truing and dressing both be realized at the same time.Analyzed the mechanism of laser truing and dressing bronze diamond grinding wheel under the short pulse duration,high power density laser function, the majority energies were used to remove the material in gasify, ablation material which to be removed was mainly realized through the mechanism of shallow layer gasification Afterwards, the method which to corrected the circle beats erroneous of bronze-bonded diamond grinding wheel in highly effective was still not existence at present .this article based on optics triangulation method with laser exposure in wheels radial direction has development the closed-loop electric circuit to control pulse laser and obtained the output signal of great pulse laser controlled by closed-loop circuit. An accurate online machining system to measured the laser's emission was designed, the pulsed laser was controlled to ablate the wheels, solved the problem which can't control the precision of direction optical axis of laser ablation and obtain the satisfactory result. Further more, we found that the truing and dressing can carry out at the same time ,which changed the tradition that truing and dressing must be carried out by two steps.The precisely truing and dressing technology of laser-machinery which was suitable to truing and dressing bronze-boned diamond wheels with bigger abrasives in size, has been studied in further, Finally, in order to examine the effect of truing and dressing and the influence rule caused by laser parameters, the survey experiment of grinding force and surface roughness of work piece of aluminum oxide ceramics which grinded by the bronze-bonded diamond wheels was studied. Indicated that the wheels could be carry on grinding effectively after truing and dressing with appropriate laser parameters, and the effect of truing and dressing with laser was surpass to silicon carbide hoop.This article's main innovation achievements as follows:1.The first time to use the acoustic-optic Q-switched Nd:YAG laser to ablation bronzed-bonded diamond wheel in radial direction, the realization of non-damage abrasive's micro removes lays the foundation for precisely truing and dressing to realize2. Further more, we found that the truing and dressing can carry out at the same time ,which changed the tradition that truing and dressing must be carried out by two steps.3. Creatively makes top observable and controllable system.4. Through studying in theory and experimental,choosing reasonable laser process parameters, the precisely truing and dressing of bronze-bonded diamond wheels was realized and the grinding performance after truing and dressing by laser was confirmed.