Precision Machining IX

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Authors: János Kundrák, Tamás Makkai, István Deszpoth
Abstract: In producing parts, besides increasing accuracy and maintaining/improving the cut surface quality, the main effort of the manufacturers is to improve the productivity/profit. In face milling this aim can be achieved first of all by increasing cutting speed and feed. The importance of feed impact analysis is justified by the general effort to prefabricate parts near net shape, if possible by one pass material removal. If the manufacturing is done by one pass, the surface rate (Aw, mm2/min) can be increased by the increase of feed. It fz feed is increased, the feed per tooth (keeping ap at constant value) ap/fz ratio is changed and as a consequence also the load on cutting edges and the character of chip deformation. The increase in the feed and the change in the chip cross section shape influence the cutting forces and the efficiency. In this paper, the changes in the cutting force components with different feed rates are demonstrated, while the value of the feed is increased 16-fold.
Authors: Steven Y. Liang, Zhi Peng Pan
Abstract: On process mechanics, the mechanical and thermal stresses and their distributions within the material as imposed by machining is essential, and on materials mechanics, the crystal plasticity and microstructural dynamics of recrystallization, texture evolution, phase field variation, as well as constitutive of flow stress and other properties play pivotal roles. Furthermore, mechanical, thermal, and even chemical stresses imposed by machining effect the evolution of part microstructure and bulk properties, but on the other hand the materials microstructure can also change the flow stress characteristics and heat generation mechanics of machining. This process-materials interaction of bilateral nature is not clearly understood in the current literature. This paper outlines an iterative blending scheme to factor in both the process mechanics and materials mechanics in one analysis platform to facilitate the predictive modeling and planning of precision machining. The integration of the two mechanics domains combines macroscopic analysis of contact plasticity and moving heat source with the microscopic analysis of constitutive and homogenization modeling, to achieve a holistic descript of precision machining thus supporting process design and optimization. Steels, and titanium alloys are discussed as example material families in machining.
Authors: Ildikó Maňková, Marek Vrabel', Daniel Kottfer, Mária Franková, Miroslav Paľo
Abstract: In terms of machinability are titanium alloys classified in the group of difficult to cut materials. The main factors determining this status are limited tool life, high generated cutting forces (torque) and temperature in cutting zone caused by low thermal conductivity as well as chemical reactivity with cutting tool. Solid carbide drills still remain as preferred choice in hole making process when machining Ti6Al4V alloy. Besides cutting conditions, tool and cutting edge geometry significantly affect the value of torque. Reduction of process energy requirements can be achieved by appropriate optimization of these parameters. Mathematical model describing influence of cutting speed, feed rate, clearance angle and cutting edge radius on investigated variable with high reliability coefficient (R2=96.72%) was found. Drilling experiments were designed and carried out using Taguchi orthogonal array L16.
Authors: Andrzej Matras, Wojciech Zębala
Abstract: Paper presents some investigations, concerning simulation of the nickel based alloy machining. The aim of the research was an optimization of the cutting data for the purpose to increase the machining efficiency and stabilization of the tangential component of the total cutting force at the assumed level. A dedicated physical material model was built and then included to the simulation strategy. Authors demonstrated the influence of the feed rate optimization on the tangential component of the total cutting force value changes and the chip area and in this way the improvement of the cutting process.
Authors: Raul Turmanidze, Giorgi Popkhadze
Abstract: In view of the fact that the endo-prosthesis heads of human hip-joint are operated in extreme conditions, in respect of load, the selection of corresponding material and also increase of precision and quality of machining of spherical surfaces is rather topical task.In the submitted work are reviewed the problems connected with definition of the influence degree of orientation of the sapphire crystal on its workability during diamond grinding with a butt of the ring and elaboration of the perspective, original scheme of formation of the incomplete spherical surface, particularly, of the sapphire head of endo-prosthesis of the human hip-joint.
Authors: Jan Řehoř, Jaroslava Fulemová, Alena Vagaská, Miroslav Gombár, Katarina Monkova
Abstract: The article deals with the experimental investigation of cutting conditions from the view of force load during machining high alloyed tool steel EŠ 419556 (standard by Škoda a.s. Pilsen, based on DIN 1.2326) at high speed milling. The aim of presented research is investigation of the most favourable contact and cutting conditions to minimize the power load of the cutting edge. Processing of measurement results within presented investigation was focused only on the components of cutting force FC (tangent) and FCN (normal) that adequately characterize the cutting process. The experiments were also carried out at cutting depth (ap) changing during high speed milling. The obtained results are presented in the paper by means of graphs that clearly show the behaviour of cutting force components at given conditions.
Authors: Grzegorz Struzikiewicz, Ksenia Rumian
Abstract: This paper presents the results of the experiments which aimed to determine the value of the specific cutting force (SCF) during longitudinal turning of sintered alloy Inconel PWA. The analysis of the influence of cutting speed on the value of SCF was carried out. Taguchi L9 (2)3 orthogonal array has been applied for experimental design. S/N ratio and ANOVA analyses were performed to identify significant parameters influencing specific cutting force. The analysis presents the method that reduces the cutting power during turning of sintered nickel alloy.
Authors: Joanna Krajewska-Śpiewak, Józef Gawlik
Abstract: Under the influence of the pressure caused by the application of the cutting edge on the surface of the workpiece elastic waves are generated. Waves propagate in the material in every possible direction and can be identify by specialized measuring equipment. Acoustic emission phenomenon was used to determine the beginning of decohesion process. The article presents a new method for determination of the decohesion process during peripheral milling performed with the indexable cutting tools on samples made out of titanium based alloy and nickel based alloy.
Authors: Łukasz Ślusarczyk
Abstract: The paper presents the results of laboratory measurement of temperature in the machining zone during the straight turning of a shaft made of the AMS 5643 steel. The machining trials were recorded using the FLIR 620 thermographic camera, and the ThermaCam Researcher software was used to archive and analyse the measurement results. The experimental test plan for varying machining parameters (vc, ap, f) was developed using the Taguchi method, and the ANOVA was used for statistical processing of results. The experiment involved nine trials with a coated insert and nine trials with an uncoated insert. The obtained results will be used to improve the cutting process simulation model.

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