New Mathematical Models of Axial Cutting Force and Torque in Drilling 20MoCr130 Stainless Steel MIHAIELA ILIESCU, AURELIAN VLASE Manufacturing Department “POLITEHNICA” University of Bucharest Splaiul Independentei no. 313 Street, District no. 6, zip code 060042 ROMANIA Abstract: - Stainless steels represent materials which have known a continuous extend into various and interesting industrial fields application. Most of the time they needs machining and, one important procedure is drilling. The paper present aspects of the experimental research developed in the purpose of determining new and, more adequate, mathematical models of the cutting force and torque, in drilling 20MoCr130 stainless steel. Graphs, as well as further application of the obtained relationships are also, mentioned. Key-Words: - axial cutting force, torque, drilling, stainless steel, mathematical model 1 Introduction There are, almost, 100 years since stainless steels have been “discovered” and, nowadays, their application fields are various and challenging. That is because of their important physical and mechanical characteristics, most of all, their high corrosion resistance to various chemical agents and, why not, because of their impressive good look [2]. Usually, after obtaining, as rough material, machining is necessary, so as to obtain the shape, dimensions and surface roughness of the stainless steel part. These steels are very tough, with low thermal conductivity and, while machining, determines sever wear of the cutting tool, as well as, high value cutting forces [6]. Because of their high prices, researches on their machinability are necessary, in order to optimize the machining process, meaning, having high productivity and low costs of stainless steel parts. One important aspect of material’s machinability is represented by the values of the cutting force and torque, meaning the higher the values, the lower machinability is so, resulting a low energy efficiency use [3]. Specific literature presents some relationships regarding variables of the machining process – involving force and torque but, when experimentally checking them, one can notice, relative high difference (of the modeled ones) from the real obtained values [5]. So, it has been considered useful to determine adequate models of some machining process parameters, regarding one widely used Romanian stainless steel – 20MoCr130. Obtaining holes, in stainless steel parts, of various dimensions and precisions, is done by drilling. Cutting force, specially axial one, and cutting torque, are important parameters (output variables) of the drilling process and, can be often used for its optimization. Based on the above, this paper presents the experimental steps carried out in order to determine some mathematical models of axial cutting and torque in drilling 20MoCr130 stainless steel. 2 Research Methodology In order to experimentally determine a mathematical relationship of variables specific to a machining process, there has to be mentioned, both the independent and the dependent ones [1]. After doing that, the dependence relation type must be settled and, correspondingly, the appropriate experiments design established. The mathematical relations, regarding axial cutting force, in drilling stainless steel materials, presented by most of the articles and books dealing with this problem, are of the type: F F y f x F a D C F = [N] (1) M M y f x M a D C M = [Nm] (2) where: F is the axial component of the cutting force; M – the drilling torque; D – the diameter of the drilling tool, [mm]; a f – cutting feed, of the drilling tool, [mm/rot]; F x , F y , M x , M y - polytropic exponents; F C , M C - constants. Proceedings of the 10th WSEAS International Conference on MATHEMATICAL and COMPUTATIONAL METHODS in SCIENCE and ENGINEERING (MACMESE'08) ISSN: 1790-2769 210 ISBN: 978-960-474-019-2