Precision Machining VIII

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Authors: János Kundrák, Angelos P. Markopoulos, Tamás Makkai
Abstract: One of the most important issues to be addressed in hard cutting pertains to the evaluation of tool life as it is closely connected to machining quality and overall process cost. The attributes of tool life can be mathematically calculated based on machining conditions and other characteristics of the cutting process. In this paper the formulation developed for CBN tools, applied for the machining of 100Cr6 bearing steel is presented. Experiments were carried out for the validation of the theoretical approach. Additionally, a novel indicator, namely wear intensity, is analyzed and discussed, based on experimental results. Wear intensity is calculated as the ratio of flank wear to cutting length. From the analysis it can be concluded that the prognosis of tool life can be accurate with the proposed method. Furthermore, interesting and useful results are reported in connection to wear intensity and cutting speed in hard cutting.
Authors: Angelos P. Markopoulos, Nikolaos E. Karkalos, Dimitrios E. Manolakos
Abstract: A simulation of the material removal by a single abrasive grain in nanometric grinding is presented in this paper. Molecular Dynamics method is used for modeling the diamond grain and the copper workpiece. The Morse potential function is used to simulate the interactions between the atoms involved in the procedure. The abrasive grain follows a trajectory with decreasing depth of cut within the workpiece to simulate the interaction of the grain with the workpiece. The influence of the grain shape, being either square or rectangular, and of the orientation of the grain, where the grain has rake angle 10o, -10o and-20o, are studied. From the analysis it is apparent that both grain morphology and orientation play a significant role on chip formation, grinding forces and temperatures. With the appropriate modifications, the proposed model can be used for the simulation of various nanomachining processes and operations, in which continuum mechanics cannot be applied or experimental techniques are subjected to limitations.
Authors: Pavel Kovač, Vladimir Pucovsky, Marin Gostimirović, Borislav Savković, Ľubomír Šooš, Dušan Ješić
Abstract: This paper presents an investigation of possibilities of using regression analysis and genetic algorithms in modelling the cutting force values in cylindrical grinding. The process included measurement of cutting forces during cylindrical grinding and later calculating their values using abovementioned techniques. It was concluded that both techniques can be used for cutting forces modelling with genetic algorithms having a slight advantage.
Authors: Ildikó Maňková, Marek Vrabeľ, Jozef Beňo, Mária Franková
Abstract: Experimental research and modeling in the field of turning hardened bearing steel with hardness of 62 HRC using TiN coated mixed oxide ceramic inserts is presented. The main objective of the article is investigation the relationship between cutting parameters (cutting speed and feed rate) and output machining variables (surface roughness and cutting force components) through the response surface methodology (RSM). The mathematical model of the effect of process parameters on the cutting force components and surface roughness is presented. Moreover, the influence of TiN coating on above mentioned variables was monitored. The design of experiment according to Taguchi L9 orthogonal matrix (32) was applied for trials. Pearson´s correlation matrix was used to examine the dependence between the factors (f, vc) and the machining variables (surface roughness and cutting force components). The results show how much surface roughness and cutting force components is influenced by cutting speed and feed in hard turning with coated ceramics.
Authors: Danijel Djurica, Milenko Sekulić, Davorin Kramar, Pavel Kovač, Marin Gostimirović
Abstract: Goal of this paper highlight characteristics and spectrum of machining cutting sequences that programming system SolidCAM support. The practical goal of this paper is defining post-processor and machine simulation for 3-axis CNC machine like a tool for verification modern tool-path and generation G-code that will be used for cutting real part.
Authors: Tadeusz Otko, Wojciech Zębala
Abstract: Semi-manufactured parts dedicated for precise machining often have internal stresses which have remained after previous cutting and plastic processing. These stresses reside in a fixed state of balance over the entire volume of the workpiece. Removal of the machining allowance is associated with a change in the state of balance and deformation of the workpiece, which affect its dimensional and shape accuracy. The study, involving non-stress removal of precisely defined volume of the machining allowance and determination of the impact of this treatment on the deformation of the workpiece surface is presented. It is important from the point of view of dimensional tolerance of the axially symmetrical workpiece, finally processed by turning.
Authors: Józef Gawlik, Joanna Krajewska-Śpiewak, Wojciech Zębala
Abstract: The chip-forming precision machining process plays a significant role in the mechanical technology. In planning of machining operation, it is crucial to supply the information about the possible minimal value of the machining allowance. For the technologist, when planning the machining operation, it is important to define the minimal thickness of cutting layer correctly. This article presents a new method of describing the start of decohesion process in a workpiece, meaning the determination of the minimal thickness of cutting layer based on the AE signal generated in the cutting zone. The research conducted on the turning of an alloy steel and the analysis of the AE signal strength confirmed that the proposed method opens new possibilities in quickening the identification of the minimal thickness of cutting layer under normal machining conditions.
Authors: Jan Řehoř, Jaroslava Fulemová, Katarína Monková, Peter Monka
Abstract: High-speed cutting (HSC) or high-speed machining (HSM) is an issue that the scientists deals with in long-term. To demonstrate the explicitness, that a full HSC machining process is considered, it is necessary to monitor the series of factors. In particular, the process of chip formation, cutting forces, cutting temperature, vibration, tool life and surface finish quality in relation to the method of machining, machined material and its properties. The article deals with the detailed analysis and evaluation of the chip formation in order to determine the hard area, transition area and veritable HSC machining. The evaluation process is based on the proposed experimental model, which is confronted with the measurement results.
Authors: Jozef Beňo, Ildikó Maňková, Dagmar Draganovská, Peter Ižol
Abstract: In this paper, author introduce common needs of increasing surface quality in tool making, a sort of products manufactured by free form milling technology. Principles of the free-form surface decomposition into measurable samples are presented and that is a method of combining CAD modeling with design of sampling objects. Sampling objects are classed both according to their measurability and applied milling strategy. Authors verify experimentally their sampling approach for three milling strategies applied in surface finishing operations while free-form surfaces are investigated in terms of their signed radii. Verification of proposed approach is based on statistical distribution of the measured surface roughness data.

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