Papers by Keyword: Laser Milling

Abstract: Regional-input high-power laser beam inevitably leads to inhomogeneous and instable temperature distribution of laser milling(LM) process. Knowledge of thermal of multi-track LM is critical to understand the interaction of different milling tracks. Taking into account temperature-dependent thermal conduction and heat capacity, a three-dimensional transient thermal finite element model has been developed. The moving laser beam is simulated with the employment of ANSYS parametric design language and latent heat is considered by using enthalpy. Several conclusions according to the simulation results were produced, comparing with the previous track, the latter one has larger heat affected region and larger in homogeneous temperature distribution; the greatest temperature gradient takes place near the edges of milling part where the scanning direction changes.

Abstract: Based on the artificial neural network (ANN), a model is established to describe the relation of the laser milling quality of the Al₂O₃ ceramics with the ceramics parameters. The milling quality of Al₂O₃ ceramics are predicted with the model in which the input parameters consist of laser power, scanning speed and defocus amount and the output parameters include the milling depth and width. The results show that the mean error is small, and the model has good verifying precision and excellent ability of predicting. The laser process parameters can be chosen easily and accurately to improve the processing quality of laser milling.

Abstract: Milling of Al₂O₃ ceramic is affected by various factors. Combination of laser milling parameters was optimized based on orthogonal experiment in this study. The affect degree of the parameters on the milling depth was obtained by range analysis ,based on which process parameters were optimized and laser milling experiment was taken on circular cavity using optimized parameters. The results indicated that the sequence of the factors affecting on the milling depth was laser power,scanning speed, overlap amount,defocused quantity successively. By using optimized parameters,milling depth of 0.4mm was obtained for single layer experiment,and milling result was satisfactory. The roughness was increased because the molten on the specimen surface failed to be removed,thus the pressure of the assist huff gas should be increased to improve the surface quality.

Abstract: Artificial neural networks were introduced in the area of laser milling. The prediction model of surface quality in laser milling parts, including the width, depth of cladding layer, was proposed based on the back propagation (BP) neural networks. The model combined the global optimization searching performance of the genetic algorithm and the localization of the back propagation (BP) neural networks. Five technical parameters were selected to test the reliability of the model. The simulation and experimental results show that the evolutionary neural network based on genetic algorithm can effectively overcome the problem of falling into local minimum point. This method can get higher accuracy of prediction. It improves the measurement precision with the maximum relative error 2. 21% between the predicted content and the real value.

Abstract: Abrasion resistant (AR) steels offer excellent hardness and strength properties in applications as mining and earth moving machines. As an outcome of high hardness AR steels can be used to produce durable, light-weight and energy saving products. However, their mechanical processing can be challenging as the hardness of the material approaches the hardness of the tooling used. This places high forces on cutting tools and machines, which, in turn, increases wear and causes early breakdown. This research examines whether the laser treatment of AR steels can be used to aid guillotine shearing. The tested material was abrasion resistant steel with hardness of 400 HBW. Two different laser treatments were examined: local laser heat treatment and laser milling. The aim of laser heat treatment was to change the original martensitic microstructure locally into weaker structure, beneficially for shearing. Narrow grooves were made along the cut line by laser milling, and then the plate cut along them. The effect of local laser heat treatment and the fracture initiating effect of the groove was evaluated from the cutting force. Microhardness tests and micro photos were taken after laser heat treatments. The results indicated that the shearing force of AR steels can be reduced up to 25% with the aid of laser heat treatments. Laser milling had only a slight effect to the shearing force of up to about 8%. In addition, the relative depth of the laser milled groove is estimated at the same range, thus force reduction is mainly due to reduction of material thickness.

Abstract: An experimental study of the pulsed laser milling process for a sintered polycrystalline diamond is presented. The characteristics and quality of the cavities machined with a Yd laser under different pulse energies, pulse overlaps, scan overlaps and numbers of passes are discussed, together with the effects of these parameters on the cavity profile, depth of cut and surface roughness. A statistical analysis is also presented to study the relationship between the process parameters and surface roughness. It shows that the optimum pulse overlap and pulse energy may be used to achieve good surface finish, whereas scan overlap and number of passes can be selected to improve the depth of cut without much effect on the surface finish.

Abstract: A new method for laser milling of Al2O3 ceramic based on deteriorative layer controlled is presented in which no assistant gas was used during the laser milling. The new milling technology is developed by means of laser scanning of ceramic surface and forming a deteriorative layer directly. Laser milling parameters are determined through crystal phase’s analysis of the deteriorative layer. The laser milling depth, surface quality, and milling mechanism with different milling parameters were studied systematically on an Nd: YAG CNC laser and multi-layer laser milling experiments were also conducted with optimized processes on the surface of Al2O3 ceramic workpiece. Therefore, the practical experimental results are that each depth of layer milling is between 0.35-0.5 mm and the surface roughness of laser milling reaches to Ra 2-3.2μm. The experimental study has thus provided deeper understanding on laser milling technology for Al2O3 ceramic both in theory and application.