Department of Manufacturing Science and Engineering

The determination of the cutting force coefficients is a critical point in the case of using the mechanistic cutting force model for predicting the forces during milling processes. The main reason is that the computations require a series of experiments with special geometrical conditions, and the validity of the results is limited. In this paper a cutting force predicting method, based on the mechanistic cutting force model will be introduced, together with an algorithm for determining the cutting force coefficients in the course of a single experiment without restrictions in regard to the cutting geometry. Besides the fact that the proposed method lifts the geometrical restrictions of the previously published solutions, it makes it possible to calculate the coefficients just when they are needed for force prediction right at the machining process, to avoid the problem of the limited validity of the coefficients. In this case the real-time measuring of the cutting forces is needed, while the forthcoming forces can be predicted with an appropriate look-forward algorithm, which is also presented.

The evolution of GPUs (graphics processing units) has been enormous in the past few years. Their calculation power has improved exponentially, while the range of the tasks computable on GPUs has got significantly wider. The milestone of GPU development of the recent years is the appearance of the unified architecture-based devices. These GPUs implement a massively parallel design, which led them be capable not only of processing the common computer graphics tasks, but qualifies them for performing highly parallel mathematical algorithms effectively. Recognizing this availability GPU providers have issued developer platforms, which let the programmers manage computations on the GPU as a data-parallel computing device without the need of mapping them to a graphics API. Researchers salute this initiative, and the application of the new technology is quickly spreading in various branches of science

The introduced cutting model uses the widely applied mechanical-dynamical differential Lagrange model together with one of the most popular experimental force model (Kienzle-Victor model) in order to provide the more accurate demonstration and simulation of cutting processes. To increase the reliability of the results the authors considered as much parameters and as complex chip geometry as the calculations and processing made it possible. In this paper the sophisticated model of milling operation was the aim of the authors. The simulation results show good equivalency with the measured real cutting experiments. In spite of the complexity of the equations the rapid development in the informatics (hardware and software tools) helped the handling and quick calculation of the equations in this type of models.

Importance of telepresence application increases in the field of manufacturing. In production the main activities are divided; the locations of management, design, manufacturing and services are separated sometimes to diverse countries or continents. The development of information technologies and telecommunication made possible the sense of presence from a remote location. In this paper authors introduce a set of information processing methods that was developed to answer the new challenges of telepresence application in manufacturing. Process signals, such as cutting force or acoustic emission, were processed using linear prediction method. Due to this transformation of process signals not only the amount of the relevant information was reduced but we also gain an expressive form to distinguish the deviated states of machining processes. The developed monitoring method was used successfully for experimental monitoring of different machining operation in the case of highly differing signal types. As another type of data processing for telepresence applications, data based visualization method was suggested instead of direct broadcasting video information. The simulated virtual environment, the generated diagrams, the properly selected information may help in telediagnostics of complex manufacturing environment. As an experimental demonstration the monitoring of robotized manufacturing was investigated.

When the mechanistic cutting force model is applied for cutting force prediction during multi-axis milling, the accurate determination of the contact area between the cutter and the workpiece and the fast processing of the gained geometry data play an important role. During the evolution of the material removal simulation techniques the discrete z-map method has become the most widespread in this field, although it does not cover the whole cutter surface and its use requires the rearranging of the geometry data before the cutting force estimation. In this paper the reconstruction of the cutting force equations of the mechanistic model is proposed for the purpose of the direct consuming of the geometry data. To this end the multi-dexel based material removal simulation method is applied which provides general solution for the contact area determination on the whole cutter surface and gives more accurate result as opposed to the z-map method. The form of the introduced algorithms lets them being executed in a highly parallelized manner by general-purpose graphics processing units (GPGPUs), thereby increasing dramatically the performance of the simulation and the cutting force estimation as compared to the existing solutions.

This research paper aims to investigate the drilling capabilities of the sintered powder metallurgy parts. Due to their special properties, these materials Exploiting said properties enables us to create selflubricant bushing as well as special alloys. In order to evaluate the investigated parameters, comparative experiments were conducted. Both the tool materials and the application of cooling varied in the experiments, in the framework of which cutting force, drilling torque and tool wear were measured. The hole geometry (diameter accuracy and circularity) was also checked. Owing to the environmentally friendly machining conditions, the experiments can be carried out by means of dry machining, air cooling and minimal quantity lubrication. According to our results, it was the cutting force and the tool wear that the cooling of the tool had the greatest effect on in the case of powder metallurgy materials.

Machining and more specifically face milling are productive ways of material shaping. Predictive models are very important for effective: quick, easy-to-use and accurate process planning. There are many industrial and scientific researches about modelling the prominent process parameters of machining, notably the machining forces. The main cutting force is one of the most important indicators as it is a primary output parameter of the chip-removing process. The specific cutting force is long time used, traditional type of modelling the main cutting force but still there are missing or difficult-to-find numerical information about the effect of some of the input machining parameters such as cutting speed. In this research, the effects of the theoretical chip-section geometry and the cutting speed were examined through face milling experiments of the S960QL high strength structural steel.

Rad prikazuje cjelokupni proces izrade prekretača paleta. Opisan je proces modeliranja, pripreme i proces proizvodnje. Dijelovi su pripremani za obradu na strojevima upotrebom softvera CAD/CAM prateći pravila tehnologije obrade deformiranjem. Prikazanim postupkom proizvodnja se optimizirala, ubrzala, te je proces proizvodnje kontroliran u svim koracima. Modeliranje i simulacija izvršeni su pomoću softvera SolidWorks, a zatim je model rastavljen na dijelove koji su prebačeni u softver ToPs 300, gdje se izvršilo optimalno planiranje i iskorištenje ploče lima. U ovome radu definirana su osnovna pravila modeliranja i prikazana neka tehnološka rješenja prilikom sklapanja prekretača palete.

Rad prikazuje cjelokupni proces izrade prekretača paleta. Opisan je proces modeliranja, pripreme i proces proizvodnje. Dijelovi su pripremani za obradu na strojevima upotrebom softvera CAD/CAM prateći pravila tehnologije obrade deformiranjem. Prikazanim postupkom proizvodnja se optimizirala, ubrzala, te je proces proizvodnje kontroliran u svim koracima. Modeliranje i simulacija izvršeni su pomoću softvera SolidWorks, a zatim je model rastavljen na dijelove koji su prebačeni u softver ToPs 300, gdje se izvršilo optimalno planiranje i iskorištenje ploče lima. U ovome radu definirana su osnovna pravila modeliranja i prikazana neka tehnološka rješenja prilikom sklapanja prekretača palete.

Condition monitoring of metal cutting procedure has always been of primary importance. In this paper the research project about vibration behaviour of the micro drilling has been described. The rectangular workpiece was made of 1.2345 steel. Altogether more, than 1 type accelerometer during the drilling procedure has been tested. For the first part of the measurements an SKF made vibration analyser has been used. For the second part of the tests National Instruments made equipment has been used. The sensor was a Brüel & Kjaer made 4318 accelerometer. The results have been interpreted as frequency-amplitude diagrams. A conclusion was drawn, that there is strong correlation between the wear of the drilling tool and the vibration severity.

The typical histological pattern of alcoholic liver disease is a steatohepatitis. Non-alcoholic fatty liver disease is a common condition frequently found in healthy subjects not affected by any other liver disease and not drinking alcohol. The spectrum of Non-alcoholic fatty liver disease ranges from asymptomatic steatosis to nonalcoholic steatohepatitis and cirrhosis. Although risk factors modification remains the cornerstone of therapy for fatty liver disease, there is, in recent years, a growing evidence of usefulness of alternative medicine. Silybum marianum (milk thistle or silymarin) is currently the most well researched plant in the treatment of liver disease, especially in those caused by oxidative stress (alcoholic and non-alcoholic fatty liver and steatohepatitis, drug and compound induced liver toxicity). The main effects of silymarin are the membrane stabilizing and antioxidant effects, it is able to help the liver cell regeneration; it can decrease the inflammatory reaction and inhibit the fibrogenesis in the liver. These results have been established by experimental and clinical trials. According to open studies, the long administration of silymarin significantly increased the survival time of patients with alcohol-induced liver cirrhosis. There is limited evidence of alpha lipoic acid (thioctic acid), and selenium in the treatment of fatty liver disease.

The research described in this article was carried out for the purpose of developing a quantitative marker for defining the average edge chipping rate of milled granite surfaces and for testing and proving whether this quantitative marker can effectively be applied. Another aim of the research was to test the applicability of the developed measurement method and the precision of the body representing the volume loss caused by chipping. The surface edges of the milled specimens were digitised using a laser scanner and chipped volumes were defined on the basis of a body generated with the help of a point cloud, and then the errors of the volumes produced by the evaluation-purpose software were examined using a digital microscope. The investigations proved that the proposed measurement method is accurate and that the replacement body defined through measurements appropriately approximates the volume of chippings in the case of milled granite surfaces.

Specific cutting force is a frequently used parameter to classify and describe the energetic environment of mechanical machining operations. It defines the ratio of cutting forces and theoretical chip section during machining. This definition makes it possible to create general technological models for precise process planning. Classical models of cutting forces already indicate that specific cutting force cannot be modelled using a single low-level analytical function due to the marked presence of size effect. The problem is amplified in the case of micro-chip forming, where the relative scale of elastic and plastic deformations in the machined material differ from those experienced in conventional cutting conditions. Previous research proved that boundaries of specific cutting forces can be defined by values of exact uncut chip thicknesses, in which case the sections of specific cutting force may indicate different types of material deforming processes. The aim of current research presented in this paper is to extend the empirical model of specific cutting force for fine chip-removing cutting processes by identifying a new boundary section of uncut chip thickness. Therefore, a new boundary chip thickness was defined based on data obtained with reference to experimental cutting force. New boundary chip thickness follows the so-far proven tendencies of already known section borders and this enables the extension of the validity range of classical approaches presented by specific cutting force models beyond macro-scaled chip forming to micro-scaled chip forming processes. The extension of the model considers the effect of cutting parameters, primarily that of feed rate.

Production features of micromachining ceramic workpieces using electrical-discharge machining are studied. The effect of pulse duration, breakdown voltage, voltage gain factor, peak current strength, and working voltage for electrical-discharge machining of VOK71 ceramic workpieces on roughness at the bottom of a channel and electrode-tool end wear are established. A mechanism is proposed for surface formation with electrical-discharge machining of current-conducting ceramic and recommendations are formulated for improving micromachining efficiency for components of this material.

 Hole numbers represent drill wear stages well.  Prediction of hole number gives tool wear status of the micro-drill.  Higher feed and lower cutting speed values improve tool life.  Artificial neural network accurately predicts hole number from thrust force.  The prediction values are in good agreement with experimental values.

Original scientific paper Powder metallurgy is one of the possible competitive options among those up-to-date replication technologies that are able to produce final shapes with no need for subsequent machining. However, there are some special geometries which require the subsequent machining of certain parts produced by powder metallurgy. These include grooves, threads and cross bores. The goal of the research discussed in this paper is to determine the effect of the material composition changes on the secondary machining properties of powder metallurgy steels (PMS). Varying the carbon and the copper content of the powder mix cutting force measurement was carried out during face grooving tests in turning. Using the ranking number of the measured characters, the machinability of samples was evaluated with each powder mixes. The optimal percentages of the copper and the carbon content were determined based on the results of the experimental measurements.

Tool condition monitoring systems are essential in micromilling applications. A tool's slenderness requires high-precision monitoring systems for online measurements. In most cases, tool health is indirectly estimated by processing and analyzing the cutting process parameters. In that sense, the main challenge lies in the proper selection of the process parameters and their processing techniques, so that a robust and accurate assessment of the tool's health is obtained. This paper proposes a frequency-and time-frequency-based analysis of cutting force and vibration signals for estimating the tool condition of a high-speed micromilling process. Measurements obtained from different cutting conditions were utilized in the analysis. The results indicate variations in the dominant frequencies, which result from tool wear. Furthermore, it is important to note that the analysis results obtained from the two process signals provide more reliable results and improve the sensing bandwidth. INDEX TERMS Condition monitoring, cutting tools, fault detection, micromachining.

Many applications are available for the syntactic and semantic verification of NC milling tool paths in simulation environments. However, these solutions – similar to the conventional tool path generation methods – are generally based on geometric considerations, and for that reason they cannot address varying cutting conditions. This paper introduces a new application of a simulation algorithm that is capable of producing all the necessary geometric information about the machining process in question for the purpose of further technological analysis. For performing such an analysis, an image space-based NC simulation algorithm is recommended, since in the case of complex tool paths it is impossible to provide an analytical description of the process of material removal. The information obtained from the simulation can be used not only for simple analyses, but also for optimisation purposes with a view to increasing machining efficiency.

Automated stone manufacturing has undergone considerable development in recent years. Thanks to international research dealing with the cutting, sawing and grinding of different natural stones, processing time shortens and tool-life lengthens. However, the process of stone milling has not been extensively examined yet, primarily because of the novelty of this technology. The aim of the research described in this article is to examine how variable cutting speed affects the quality of workpiece edges while milling granite materials. For the research, sample surfaces were formed on five granite slabs with different average grain sizes using five cutting speed values. Afterwards, changes in the average surface roughness and average edge chipping rate were examined. From the research results, it can be concluded that, due to an increase in cutting speed, the average edge chipping rate will decrease until reaching a borderline speed. In the case of a higher cutting speed, the referent ten...