The Research On Mechanism For Laser Truing And Dressing Of Bronze-bonded Diamond Grinding Wheels By Pulse Optical Fiber Laser

The diamond grinding wheel is a kind of superabrasive grinding wheel. The advantages of diamond grinding wheel which compared to the Cubic Boron Nitride (CBN) superabrasive grinding wheel is low manufacturing cost and good economic benefit. Precisely truing and dressing of bronze-bonded diamond grinding wheels is difficult which really affects the grinding performance of bronze-bonded diamond wheels. Because of the ultrahigh hardness of diamond, the traditional truing and dressing method which was based on the interaction of force to promote is not used for the bronze diamond grinding wheel.Laser dressing technology is an organic whole related to laser technology, materials processing technology, sensor technology, precision grinding technology and computer technology. It is the new multidisciplinary cross edge subject and emerging advanced dressing technology which has a wide application. The essence of the technique is based on the mechanism of pulsed laser ablation. High energy pulsed laser beam is focused and then irradiated onto the outer surface of the grinding wheel which is uniform rotation. It can merge the truing and dressing on a bronze-bonded diamond grinding wheel, but there are still many problems need to be resolved.This article was based on the domestic and foreign research and combined with the characteristics of the bronze diamond grinding wheel. The pulse fiber laser was used for the truing and dressing on a bronze-bonded diamond grinding wheel, and the mechanism was deeply studying. In the processing of laser dressing, the physical phenomena including phase explosion effect, evaporation effect, plasma characteristics and heat transfer effect were analyzed theoretically. On the basis of the research, a new type technique of single tangential flow by using pulse fiber laser dressing was put forward. It provided theoretical guidance and process optimization for laser ablation of bronze bonded diamond grinding wheels.First, on the basis of the existing laser dressing system, using the pulsed fiber laser as the heating light in the process of dressing, we built this experimental dressing platform for bronze-bonded diamond wheels eroded by pulsed fiber laser and described the pulse fiber laser dressing grinding wheel system as well as its workflow. The dressing system mainly includes pulse fiber laser, external optical transmission device, laser controller, and two-dimensional moving platform.Secondly, pulsed fiber laser has the characteristics of short pulse duration and strong energy and there are some new phenomena in the erosion of the bronze-bonded diamond grinding wheels with pulsed fiber laser, including evaporation effect, plasma shielding effect and phase explosion. We analyzed the adverse effects of the phase explosion on the generation of bronze-bonded diamond grinding wheels with pulsed fiber laser and do some theoretical research on it as well. We carried out a theoretical analysis of the mechanism of plasma formation on the surface of bronze bonded diamond grinding wheel and proposed the probability models of plasma thermal ionization and the collision ionization mechanism using multi-pulse fiber laser ablation of bronze material surface and thus gained the plasma population formed by the two kinds of ionization mechanism. The numerical results showed that collision ionization is the main mechanism formed by the erosion of bronze-bonded diamond grinding wheel with multi-pulse fiber laser. In this process, the ionized copper ions would change into black oxide particles and cover the surface of the bronze wheel. Using equation model of plasma gas and numerical value, we analyzed the plasma expansion velocity and linear degree, absorption effect and the recoil pressure effect. The results showed the low absorption effect and recoil effect so we can ignore them when using the laser erosion. Those can also provide theoretical guidance for the erosion of bronze-bonded diamond grinding wheels with pulsed fiber laser.Then, according to the actual process for laser ablation of bronze-bonded diamond grinding wheel, the heat transfer equation which was established by multi-pulse laser ablation of bronze bonded diamond grinding wheel is essentially different from that of single pulse, and the heat transfer equations for multi-pulse fiber laser ablation of bronze-bonded diamond grinding wheel was built. The model was applied for numerical simulation of the heat transfer characteristics in the multi-pulse fiber laser ablation of bronze and diamond, and under relevant conditions, the laser power range of dressing bronze and truing diamond was solved. Based on the numerical results, experiments were conducted to observe the topography of a bronze-bonded diamond grinding wheel after multi-pulse laser ablation and measure the surface pit depth of the ablated bronze-bonded wheel. The theoretical analysis and experimental results showed that multi-pulse fiber laser can merge the truing and dressing on a bronze-bonded diamond grinding wheel. This study provides theoretical guidance for optimising the process parameters in the laser ablation of a bronze-bonded diamond grinding wheel.Finally, the surface temperature evolution curves of different laser power and a bronze-bonded diamond grinding wheel were analysed using the physical heat transfer model of multi-pulsed fiber laser ablation of bronze-bonded diamond grinding wheels. Experiments were conducted to observe the topography of the ablated bronze-bonded diamond grinding wheel. In addition, the brazed diamond surface was subjected to raman spectral analysis. The numerical analysis and the test results consistently demonstrated that defects, such as graphitized deterioration layers, were formed after the pulsed laser was used to ablate the bronze-bonded diamond grinding wheel surface. To overcome the shortcomings and defects of the laser truing and dressing technique for bronze-bonded grinding wheels, a new method involving the use of a single tangent liquid column flow to assist multi-pulsed fiber laser truing and dressing of bronze-bonded diamond grinding was proposed. The cooling effect of liquid flows was used for the first time in truing and dressing of grinding wheels. The single tangent liquid column flow method was employed to avoid the formation of defects, such as graphitized deterioration layers, due to the heat transfer that occurred in the diamond during the truing and dressing process using the high-power pulsed laser. After the truing and dressing process, the grinding wheel surface had good quality and topography, and graphitized deterioration layers were formed in the diamond, to a lesser degree. The present study provides guidance and a basis for the optimization of the process of using multi-pulsed fiber lasers to true and dress bronze-bonded diamond grinding wheels.