Abstract: Professor Oprean dedicated his life and work to the school and science. During the nearly 90 years of life he passed by majority hypostasis, statutes and social functions: peasant, worker, student, engineer, professor, employee, enterprise manager, researcher, designer, etc. and perhaps for this reason he managed to do well in the most complex and delicate situations, to find a common language with people from various professions and social statuses, from ordinary people to ministers or even heads of governments or states, from factory workers to executives, writers and readers or editors. He formed generations of students, many PhDs, he published or supported more than 250 scientific papers (treaties, monographs, books, scientific papers and communications) in the country and abroad.

pp. 59-64 View full text

SURFACE ROUGHNESS MONITORING IN CUTTING FORCE CONTROL SYSTEM

Uros ZUPERL^1,*, Tomaz IRGOLIC², Franc CUS³

¹⁾ Assist. Prof., researcher, University of Maribor, Faculty of mechanical engineering, Maribor, Slovenia

²⁾ B.Sc., researcher, University of Maribor, Faculty of mechanical engineering, Maribor, Slovenia

³⁾ Full. Prof., University of Maribor, Faculty of mechanical engineering, Maribor, Slovenia

Abstract: The aim of this contribution is to present a reliable cutting force control system in end milling with the main focus on the integrated surface roughness prediction model. In this control system, cutting force sensor is used to control the milling process by digital adaptation of cutting parameters. The main goal of this paper is to present a new method for surface roughness (Ra) prediction by using measured maximum cutting forces signals and initial cutting parameters. End milling machining process of hardened die steel with carbide end mill was modeled using the adaptive neuro-fuzzy inference system (ANFIS). The purpose of ANFIS model is to predict the effect of machining variables and maximal cutting force on surface roughness during machining. The surface roughness tester is used to observe the actual surface roughness of the machined surface after the machining tests. The comparison between the predicted surface roughness values determined by ANFIS and experimental measurements indicates that the performance of this method turned out to be satisfactory for evaluating Ra, within a 3% mean percentage error and 96% accuracy rate. The developed model is used to monitor milling operations and provide warnings to the operator. The ANFIS model can also stop the machining process for tool change based on a pre-set surface roughness limits.

Key words: force control, prediction, surface roughness, milling, ANFIS.

pp. 65-70 View full text

COMPARATIVE STUDY OF THE BALL NOSE END MILL MACHINED SURFACE QUALITY

Vlad DICIUC^1,*, Mircea LOBONŢIU²

¹⁾ Lecturer, PhD, IMTech Department, Technical University of Cluj Napoca, North University Center of Baia Mare, Baia Mare, Romania

²⁾ Prof., PhD, IMTech Department, Technical University of Cluj Napoca, North University Center of Baia Mare, Baia Mare, Romania

Abstract: Ball nose end mills are highly used for 3-5 axes milling operations. The current paper presents a package of experiments for ball nose end milling, considering two cases: machining with the tool in a vertical position and machining with the tool in a tilted position compared to the machined surface. In comparison to the experiments presented so far in the known literature, the tool is tilted on two directions thus providing specific data. The results cover surface profile, texture and surface roughness measured on two perpendicular directions. References with similar data obtained by other researchers are also made.

Key words: ball nose end mill, 5 axes milling, surface profile, surface roughness.

pp. 71-76 View full text

ANALYTICAL METHOD TO PROFILE the HOB MILL Generating an Ordinate Whirl of Surfaces with Non-Involute ProfilE

Virgil TEODOR¹, Gabriel FRUMUŞANU^2,*, Nicolae OANCEA³, Silviu BERBINSCHI⁴

¹⁾Assoc. Prof., PhD, Manufacturing Engineering Department, Dunărea de Jos University of Galaţi, Romania

^{2, 3)} Prof., PhD, Manufacturing Engineering Department, Dunărea de Jos University of Galaţi, Romania

⁴⁾Lecturer, PhD, Mechanical Engineering Department, Dunărea de Jos University of Galaţi, Romania

Abstract: The ordinate whirls of surfaces, cylindrical or helical, are generated by enwrapping with worm type tools. A particular aspect of this problem is to profile the tool primary peripheral surface. The classical solution is offered by Olivier second theorem, referring to a couple of reciprocal enwrapped surfaces, which depend on two independent parameters. We should notice that analytically solving such a problem could involve serious difficulties in calculus and, further, in results numerical analysis A newly developed analytical method to profile the primary peripheral surface of the hob mill used for generating the slitting saw cutter teeth with non-involute profile, used in the iron & steel industry, is presented in this paper. The method was conceived grounded on the helical motion de-composing principle and it works in two steps. The profile of the rack-gear conjugated to the generated profile is firstly determined, according to Intermediary surface method, and then, on this base, the hob mill primary peripheral surface is found. A specific profiling algorithm is suggested, followed by a numerical application, in the case of a slitting saw cutter with triangular tooth profile and having the diameter of 1600 millimeters.

Key words: Hob mill profiling, analytical method, helical motion de-composition, Disc-tool, Triangular tooth.

pp. 77-82 View full text

EFFECTS OF LASER CLADDING PARAMETERS ON MICROSTRUCTURE PROPERTIES AND SURFACE ROUGHNESS OF GRADED MATERIAL

Franc CUS^1,*, Uros ZUPERL², Tomaz IRGOLIC³

¹⁾ Prof., PhD, Head of Production Engineering Institute, Faculty of Mechanical Engineering, University of Maribor, Maribor, Slovenia

²⁾ Assist. Prof., PhD, Production Engineering Institute, Faculty of Mechanical Engineering, University of Maribor, Maribor, Slovenia

³⁾ Assist. Production Engineering Institute, Faculty of Mechanical Engineering, University of Maribor, Maribor, Slovenia

Abstract: This paper shows the general properties of laser cladding that have recently added new possibilities for the local surface repairing of metal mechanical elements. Despite the fact that the technology for laser cladding is highly developed any obtained surface roughness cannot not be predicted and usually additional grinding or milling process are needed to obtain the required surface roughness. Bad surface roughness is undesirable and additional machining is needed for improving surface quality. Milling was chosen in order to improve roughness. The basic idea of the research was to measure the cutting forces under different cutting conditions and produce a model that would be able to predict cutting forces by milling layers of functionally graded material at different cutting parameters. The first basic prediction model was obtained by measuring the cutting forces in the three main directions of the coordinate system by milling clad layer and changing the cutting parameters.

Key words: milling, functionally-graded material, laser cladding, artificial neural network.

pp. 83-88 View full text

EVALUATION OF MACHINABILITY BY HIGH SPEED MILLING OF TWO STEELS

BY MEANS OF CUTTING FORCES

Irina BEŞLIU¹, Margareta COTEAŢĂ^2,*, Laurenţiu SLĂTINEANU³

¹⁾ Lecturer, PhD, Department of Mechanics and Technologies, “Ştefan cel Mare” University of Suceava, Romania

²⁾ Lecturer, PhD, Department of Machine Manufacturing Technology, “Gheorghe Asachi” Technical University of Iaşi, Romania

³⁾ Professor, PhD, Department of Machine Manufacturing Technology, “Gheorghe Asachi” Technical University of Iaşi, Romania

Abstract: One of the criteria used in order to evaluate the materials machinability by milling is the size of mechanical solicitation of the milling technological system. Usually, this mechanical solicitation is evaluated by means of cutting forces and moment. By knowing the sizes of milling forces and moments, one can adequately establish the values of milling process parameters and design or test the behavior of distinct components of the technological system under the action of the milling forces and moment. A systemic analysis of the end milling process highlighted the main groups of factors able to exert influence on the sizes of milling force components and moments. Taking into consideration the available conditions, an experimental plan was elaborated and materialized, in order to establish mathematical empirical models which could highlight the influence exerted by the workpiece material hardness and the parameters of milling process on the sizes of milling force components. Power type empirical models were determined by mathematical processing of the experimental results. The empirical models allowed the highlighting of the influence order of the considered factors. A more suggestive illustration of the influence exerted by the input factors on the sizes of the end milling force components was obtained by means of some graphical representations.

Key words: end milling process, milling force components, influence factors, milling parameters, workpiece material hardness, empirical mathematical models.

pp. 89-94 View full text

MULTIDIRECTIONAL FORGING AND IMPROVEMENT OF HYDRAULIC FORGING PRESS USING ADDITIONAL DEVICES

Karel RAZ^1,*

¹⁾ Lecturer, Ph.D., Eng., Regional Technological Institute, University of West Bohemia, Czech Republic

Abstract: This paper deals with possibility of multidirectional forming. During design process of new device for multidirectional forming it is necessary to consider optimal usage of material and resistance against loading during technological operation. Design of new equipment for multidirectional forging is here performed. It is designed starting from idea of using standard hydraulic free forging press with upper drive as additional device. Forming with increased accuracy is nowadays highly requested by all companies and producers have to improve design of forging machines. These better forged parts can be produced with lower cost as normal parts. It is caused by fewer machining operations. New design of multidirectional forming has better dynamic resistance. It is suitable for dynamic and shock loading. The solution is done by using finite element method in all simulations. Also all simulations are validated by comparing with real measurement during forging operation. The paper presents the basic design of multidirectional forging device and also the main parts that are checked in terms of strength and displacement. Also, the whole device had undergone dynamic analysis. This analysis shows suitability for high-speed forging with frequency up to 100 strokes per minute.

Key words: Multidirectional forging, simulation, measurement, hydraulic press, modal analysis, mechanical stress, multiway.

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