Research And Experiment On A Deep-hole Twist Drill With Variable Parameter Spiral Groove

Deep-hole machining has been widely used in various areas such as aerospace,automobile manufacturing, national defense, general machinery, petroleum, miningenterprises, agricultural machinery and engineering machinery. Deep hole drillingprocess is conducted in closed or semi-closed situations, which brings about the mostdifficult problems of metal cutting, such as difficulty in scattering the heat in metalcutting and clearing the cutting chips, poor rigidity of the metal cutting operation system,and unsatisfactory cutting effects. Due to technical difficulties of deep-hole drilling, inthe low-end market, domestic users generally use parabolic type deep-hole drill, andapply the graded feeding mode, so the drilling efficiency is very low; while the high-endmarket has been occupied by foreign firms. With the continuous development of thedomestic machinery manufacturing and tool technology, the voice of independentlydeveloping home-made high-grade deep hole twist drill is louder and louder, in the keyareas of pillar of the national economy, especially in the automobile manufacturingindustry.In this dissertation, optimization of the spiral groove and the forms of drill pointwas carried out, and a structural design method for the new type of deep-hole twist drillwith variable parameters spiral groove and plane flank was put forward by means oftheoretical research, numerical simulation and experimental research. Then the failuremechanism and the cutting force model of deep hole drilling were studied. The mainwork is as follows:(1) The mathematical model of a new type of deep hole twist drill with variableparameters spiral groove and precise3D modeling method were studied. Through theinvestigation of cutting mechanism of the deep hole drilling, the structure of variableparameters spiral groove was designed. Application of non-instantaneous pole envelopeprinciple, the movement process of the grinding wheels’ processing variable parameterspiral groove was analyzed, and the mathematic model of the deep-hole twist drill withvariable parameters spiral groove was set up. And then the structural characteristics ofthe new type of deep hole twist drill was theoretically proved. Based on the algorithm ofB spline surface interpolation, the method of establishing the3-D solid model of thevariable parameter spiral groove was found by applying UG, and the accuracy of3-Dmodel was verified. (2) Optimization for the structure of a new type of deep hole twist drill withvariable parameters spiral groove was carried out. Based on the characteristics ofvariable parameters spiral groove, the shape of cross section of the spiral groove wasdesigned. Through combining the orthogonal test design method with numericalsimulation method, key structure parameters of drill point were optimized and improved,and the best design was verified and determined by experiment.(3) The deep hole drilling mechanism was discussed from the aspects of drillingforce, the machining quality of hole surface and tool failure type. Firstly，by contrastexperiments, that variable parameters spiral groove structure of the new type ofdeep-hole twist drill could decrease cutting force and improve drilling stability wereproved. Secondly, through the hole roughness and aperture expansion test, the influenceof cutting parameters and the core thickness increment on the two was discussed. Thirdly,through the experimental research on the wear resistance of the new type of deep-holetwist drill in machining gray cast iron, nodular cast iron and alloy steel and othermaterials, the failure mechanism was preliminarily studied.(4) By using the method of orthogonal experiment, and using the cutting force datacollected in different drilling experiment scheme, the drilling force mathematical modelof the new type of deep-hole twist drill with variable parameters spiral groove cutting45steel and LC4aluminum alloy was established, and then its reliability was verified. Bythe methods of correction coefficient, the cutting force mathematical model of LC4basedon the cutting force of45steel was established and then verified, which proved thereliability of the method of correction coefficient. Through the same methods, the cuttingforce mathematical models of HT300and42CrMo were obtained, and the differencebetween cutting force in drilling different materials and that in drilling45steel wasanalysed.