Theoretical And Experimental Research On Grinding Of High Performance Drill Point With Biglide Parallel Machine

With the development of science and technology and the increasing needs for the manufacturing industry,in particular,the development of modern automotive and aviation industries,the requirements have been increasing significantly for the quantity and quality in drilling process.In addition,a variety of the new hard-to-cut materials,such as the composite materials,have been widely used in machinery manufacturing,which have put forward the higher requirements for drills than ever.In order to develop the new types of drill point corresponding to this requirement,it is needed to develop the new economical and efficient grinding structure and appropriate grinding model.Moreover,the drilling thrust force and torque should be deeply investigated during drilling process so as to grind out the optimized drill point to improve the drilling precision and efficiency,considering the material of work piece and cutting condition.This paper is faced to grinding of the twist drill point,and the research were carried out for grinding technology based on biglide parallel machine tool and the influences of the drill point angles on the drilling forces.Our major contributions are summarized as follows:1,Analysis has been taken seriously for grinding technology and drilling forces of twist drill,in which the history and current situation have been reviewed for modeling of twist drill,modeling of drilling forces and genetic programming.The necessity and feasibility were proposed for grinding of twist drill point based on biglide parallel machine.2,By analyzing the kinematics of biglide parallel grinder,the grinding trajectory and its impact on grinding of drill point and grinding condition were surveyed.Aim to the biglide parallel grinder,the stiffness modeling and performance analysis were conducted using virtual spring method.In accordance with the relationship between the coordinate system of machine and drill,the grinding principle was proposed and the mathematical model of the flank and flute face and cutting edge in the twist drill were derived on the machine coordinate system.3,Based on the mathematical model of twist drill,the relationship equations were given for the drill point geometry parameters and the grinding parameters in biglide parallel grinder.Moreover,the optimization of the grinding parameters was formulated mathematically for grinding of the custom-oriented twist drill,which was performed using genetic algorithm.Lastly,the computer simulation was conducted for the helical drill point model.4,Aiming to the genetic programming,the evolutionary computation and its overview and basic technology were analysed,in which modeling method based on multi-gene genetic programming was proposed.And then,using the published data,the predicting model of the drilling force was obtained of which the accuracy was verified comparing the result..5,Through grinding experiments on biglide parallel grinder and drilling tests with the work piece made in carbon fiber reinforced plastics(CFRP),the accuracy of the mathematical model was verified and the training data were taken for predicting model of drilling force using drill point geometry parameters.Based on multi-gene genetic programming,the experimental prediction model of drilling force was established using drill point geometry of which the accuracy and the generalized behavior were verified.Moreover,the optimized geometric parameters were obtained to reduce the drilling forces under the given cutting condition.