Research On Motion Control Of High-performance Surface Grinding For Knifes-scissors

The spatial surface grinding is the most complex and typical grinding process inknife-scissors process, which has an important influence on the surface quality ofknife-scissors product. However, the knife-scissors is conventionally grinded by means of2-axis hydraulic surface grinder or2-axis NC surface grinder in our country, which can onlygrind simple knife-scissors product and can’t produce complex knife-scissors product, and thegrinding machine of which need grinding test and adjustment. This backward grinding waycould not meet the quality and machining efficiency demand of new knife-scissors products.Although the4-axis or5-axis surface grinders for the knifes-scissors are available in theforeign countries, the cost is high and their critical technologies are kept secret, about whichthere is hardly any substantial open thesis and information. Therefore, independent researchand development of multi-axis knifes-scissors surface grinder has important economic and socialbenefits to develop high-end knifes-scissors equipment and manufacturing industry in ourcountry. The key techniques of high-performance knifes-scissors surface grinding motioncontrol are studied detailedly and systematically in this thesis. An applied integrity method isdeveloped to realize interpolation and control function of knifes-scissors surface grinding, andit has been applied to the self-made CNC system. Main research contents and research resultsare as follows:(1) Motion control method of2-axis knifes-scissors surface grinding is developed forthe process requirement of simple knifes-scissors. Combined with the projection rules, thefunctional relationship between the angle of rotation and grinding parameters is given. Toimplement high-speed and high-accuracy elliptic interpolation, together with parametricelliptic expression and step angle formulation, elliptic interpolation algorithm with easycalculation and controllable error is realized. In curve machining, the theoretic trajectorylength does not equal to the actual machining length exactly. If the theoretic trajectory lengthis used as the length of the acceleration/deceleration control compulsively, the machiningquality may be debased remarkably. Therefore, a new acceleration-deceleration lengthcalculating method based on the dichotomy is presented in this thesis, by which the velocitycurve is more smooth and difficulty in calculating elliptic length can be resolved.(2) In order to implement surface grinding of the complicated and specially shapedknifes-scissors, motion control method of3-axis knifes-scissors surface grinding is developed.Based on the characteristics of surface grinding and the horizontal surface grinder, thefunctional relationship between the set of machining parameters and the set of the process parameters is established. The set of machining parameters involves the radial feed, the axialfeed and the angle of rotation, and the set of the process parameters involves the grindingdepth of the top surface, the grinding depth of the bottom surface and the grinding width.And combined with the projection rules, the jointly control of a rotational axis and twotranslational axes is implemented.(3) Taken the problem of error compensation of2-axis and3-axis control method intoaccount, motion control method of4-axis knifes-scissors surface grinding is developed. Firstly,mathematical model error of3-axis knifes-scissors surface grinding is analyzed and studied indetail. The Z direction error is identified and formulated with respect to the wheel diameter,the edge contour, and the angle of rotation. Subsequently, an error compensation method ofthe interpolation error is proposed. However, it need not only meet machining precisiondemand of the blade thickness, but also meet appearance and quality demand for theknifes-scissors products. The error compensation method can improve machining precision,but it makes the Surface roughness enlarged and makes the grinding lines uneven. So, themotion control model of4-axis knifes-scissors surface grinding is developed.(4) Based on2-axis,3-axis and4-axis surface grinding motion control method,high-performance numerical control system and surface grinder prototype are developed. Thesystem supports mixed programming between the two-dimensional graph and the parameter.The experimental results indicate that the surface grinder is able to machine various kinds ofknifes-scissors, and that the proposed algorithm is effective.