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Uspješnost provedbe ultrazvučnog ispitivanja ovisi o odabranim parametrima ultrazvučnih elemenata i geometriji komponente, a posebno o kvaliteti kontaktne/reflektirane površine. Na kontaktnoj površini ostvaruje se akustički kontakt ultrazvučne sonde s površinom ispitnog materijala. U slučaju da je kontaktna površina valovita i/ili različitih hrapavosti, unos energije ultrazvučnog vala u volumen ispitnog materijala biti će različit. U radu želi obraditi utjecaj različitih vrijednosti površinske hrapavosti kontaktne površine, dobivenih određenim postupcima mehaničke obrade kontaktne površine, na amplitudu ultrazvučnog signala.

Strict fire safety regulations increase the application of products that can ensure integrity and insulation of protected objects for certain period of time. Today, most commonly used material for that purpose is calcium silicate – Ca2SiO4. Calcium silicate raw material is usually manufactured in the form of boards, which are then further processed mainly by circular saw cutting, drilling and milling before being assembled into the finished product. The main production requirement is to increase the autonomy of machining systems and productivity with minimum downtime and operator intervention. Due to the high concentration of abrasive particles in the calcium silicate material, process automation represents a demanding task. One of the most important features which need to be automated is a tool wear monitoring. Having in mind that the dynamics of the tool wear is highly non-linear and complex, construction of the reliable and precise tool wear monitoring system is quite a challenging task.

In development of new metal forming procedures it is important to know process parameters such as forming force, deformation work, stress scheme etc. Theoretical analysis is usually not enough accurate method because of numerous simplifications and assumed boundary conditions that cannot accurately describe the real situation. Beside numerical simulations, the only better method is real physical modelling by scaling down (or up) real dimensions. Similarity theory connects model, real product and process parameters. This paper associates finite element modelling and similarity theory, in order to easily and quickly determines the forming force level for the real product. Model is numerically created and its adequacy is tested by both – similarity theory and finite element modelling.

Numerous researches, made to improve mechanical properties of materials with plastic deformation, have brought scientist to discover and develop severe plastic deformation (SPD) technologies. The usage of SPD technologies result in getting ultrafine-graind microstructures of materials. Reduction of the grain size is the way to change many mechanical and physical properties of materials. One of the most important and oftenly used procedure is equal channel angular pressing/extrusion (ECAP/ECAE). The main characteristic of ECAP is that mechanical properties are significantly improved, whether subjected materials were metals, alloys or composites. Extreme reduction of crystal grain size is achievable in ECAP procedure. Not any other conventional technology of plastic deformation or heat treatment shows such good results as ECAP in improving mechanical properties of subjected materials. The most commonly used materials are aluminum and copper alloys (materials with FCC crystal grid). Because of improved mechanical properties and very low density of workpieces, ECAP procedure is used in aeronautical and space industry, medicine, automotive industry, energetics and sport. In this work is given review of ECAP procedures characteristics and tools.

In development of new metal form ing procedures it is important to be familiar with process parameters such as forming force, deformation wo rk, stress scheme etc. during design period. Theoretical analysis is usually not enough accurate method because of numerous simplifications and assumed boundary conditions that cannot accurately describe the real situation. Beside numerical simulations, the only better method is real physical modelling by scaling down (or up) real dimensions. In that way, model gives the best picture of the real production situation. When creating a model, an engineer uses similarity theory, which connects model, real product and process parameters. This paper associates finite element modelling and similarity theory, in order to avoid physical modelling. Model is numerically created and its adequacy is tested by both – similarity theory and finite element modelling.

Ceramic parts are generally produced by combination of compaction and sintering. In this paper, cold isostatic pressing (CIP) for compaction and shaping of alumina ceramics was used. This method provides green compacts of uniformly distributed high density with the absence of large pores. Prepared green bodies were sintered at the temperature of 1650°C. Influence of different particle size distribution of alumina powders and compaction pressure on green and sintered density was investigated. It was found that green, as well as sintered density slightly increased with increasing compaction pressure and decreasing alumina particle size powders. The linear shrinkage of ceramic samples during sintering was 20 to 22 %.

This paper presents the main characteristics of the 3-axis milling machine retrofitted with the Linux-based CNC open architecture control system. It is developed on the basis of a technologically outdated industrial planing machine, which was redesigned for the purpose of the technological project “Intelligent Monitoring of a Machine Tool Main Spindle”. The new machine is intended to be used for industrial, research and educational purposes, specifically, in the design and analysis of machining process monitoring and control algorithms.

Successful production is achieved by continuously improving the manufacturing process, while maintaining or increasing the quality and accuracy of product. Very important factor to achieve such goal is more extensive and deeper technical preparation of necessary technical analyses. For some of those the numerical Finite Element Method (FEM) is used. This paper shows examples where FEM was applied, as integral part of technical analysis. The first example relates to the reconditioning of a turbine vane carrier (TVC) oval deformed. TVC is brought to cylindrical shape using special tool and afterwards heated in an oven (both, TVC and tool) in order to become relaxed from residual stresses. To bring a TVC in cylindrical shape, a very small amount of plastic deformation is allowed. By application of FEM analysis a correlation between split flange displacements and stresses in the TVC was obtained. The next example of FEM application is labyrinth sealing strips reparation process of a damaged turbine rotor. Machining is done at the site in condition of disassembled turbine upper casings. Turning slide with turning tool is fixed to the turbine casing with a special device, while the rotor is rotating in the turbine bearings. Correlation between stability and stiffness of special turning device, diameter of labyrinth sealing strips and the cutting forces, was analyzed with FEM.

Today’s fast expansion of new products on the market results in increasing the need for simulation of manufacturing processes. The most common method used by computer simulation is the finite element method. This work compares the cutting force measured by turning on the lathe machining center SBL 500 with the one obtained by software package Deform 3D version 6. The goal is to explore the effectiveness of buying a software package considering the accuracy of its results.

New materials and geometry of cutting tools, as well as the new concepts of machine tools, change machinability indicators or machinability functions, which implies their continued research. One of the machinability functions are cutting forces, and their experimental study and modeling, and also optimizing of cutting parameters, will lead to increase productivity and quality, reduce production costs and increase competitiveness of company. Obtained knowledge and validity would enable the wider application of high speed turning, dry turning and turning of hard materials. To enable the measurement of turning forces with three-component measuring device « ; ; ; ; ; Kistler» ; ; ; ; ; on the turning machining center TOS SBL 500, which is installed in the Laboratory for machine tools, the work is a presentation of construction of auxiliary device for it attach on the turret head. The paper also gives testing results of auxiliary device in the turning process of hardened material.

The demands for micro- and nanometrology result primarily from the development of micro and nano technologies for the industrial areas of precision engineering, micro and nano electronics and optoelectronics, molecular technology, etc. In this work, the possibilities of micro and nano metrology of lengths in the field of precision engineering will be presented, reflected in the development of precise and ultra-precise treatments as consequence of increased requirements for miniaturization of products and the complexity of forms, and by narrowing the limits of allowed deviations with the increased requirements on the surface quality. The response from the aspect of metrology is the development of new methods and instruments whose capabilities, advantages and limitations are presented in this paper with special focus on the problem of insuring traceability and calibration. Since the Laboratory for precise measurement of length at the Faculty of Mechanical Engineering and Naval Architecture has been carrying out for a number of years intensive research in the area of micro and nano metrology in the development of measuring methods and ensuring traceability and calibration, the paper will present the results obtained at the Laboratory.

The basis has been given for the application of CAD and CAM in the process of the design and production of the concave and convex milling cutters. By applying the numerically controlled machine tools the necessity of milling cutters producing by special machine tools for reliving is avoided. By means of mathematical modelling of the form and edge geometry of cutters - backed off one can derive basis for optimization parameters of form and dimension influencing to the tools cutting characteristics, as well as the durability or the tools service-life and the quality of the of those tools.

Aluminium foams are low density materials due to the aluminium, with high strength and rigidity as well as good damping capacity due to the cell structure. Therefore, their application in the modern lightweight structures is the object of intensive research. It is possible to join such structures by welding or by screw fastening. Paper presents the results of experimental investigation of axial forces in drilling aluminium foam on drilling parameters - feedrate per tooth and drill tip angle. Samples of aluminium foam with mean closed cell size of 0.5-1.5mm, manufactured with indirect foaming by precursors AlSi12, are used as a workpiece material. Experiments are carried out at the Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb.

Alatni strojevi se još uvijek vrlo često projektiraju tako da cijeli životni vijek zadržavaju istu strukturu pa i karakteristike, a današnji trendovi na tržištu i tehnološki razvitak zahtijevaju sve veću njihovu prilagodljivost. Prilagodba alatnog stroja čestim promjenama proizvoda je zahtjevna i više puta ne rezultira željenom produktivnošću, kvalitetom i troškovima proizvodnje. Bez potpunog usvajanja koncepta modularne gradnje i rekonfigurabilnosti pri projektiranju alatnog stroja, gotovo je nemoguće osigurati brzu prilagodbu čestim promjenama na tržištu. Jedna od mogućnosti kojima se, posebno u području velikih alatnih strojeva, nastoji produljiti životni vijek alatnog stroja je "retrofiting", pri kojem se ugradnjom modernijih rješenja za pojedine funkcije stroja (posmični prigoni, glavni prigoni, mjerni sustavi, nova upravljačka računala i sl.) diže tehnološka razina i zadržava konkurentnost. U radu se obrađuje problematika modernizacije alatnih strojeva, pri čemu su u prvom dijelu prikazani trendovi gradnje alatnih strojeva, a u drugom dijelu je prezentiran postupak "produljenja životnog vijeka alatnog stroja" modernizacijom, odnosno retrofitingom. Postupak retrofitinga je prikazan na primjeru modernizacije obradnog centra, projekta provedenog u sklopu tvrtke „ 3. Maj MID d.o.o.“ Rezultati modernizacije verificirani su komparativnom analizom učinaka ostvarenih primjenom stare i nove tehnologije pri obradi poklopca cilindra.

Bez industrijske proizvodnje nema napredka i boljitka društva. Industrijska proizvodnja ostvaruje profit i zato ona mora biti suvremena, kvalitetna, ekonomična i nadasve konkurentna. Sigurno je da obradni sustavi čine temelj industrijske proizvodnje i moraju biti prilagodljivi da bi uspješno rješavali zahtjeve sve kraćeg vremena isporuke složenih proizvoda koji se na njima izrađuju. Na tržištu danas postoje različiti alatni strojevi, kao dio obradnog sustava, i njihov pravilan izbor kod nabave je ključan za njihovu daljnju eksploataciju i iskoristivost. Ovaj članak daje pregled trendova razvoja suvremenih alatnih strojeva i njihovih osnovnih modula i može pomoći pri njihovom pravilnom izboru. Without industrial production there is no progress and prosperity of society. Industrial production make the profit and therefore it must be modern, high quality, cost effective and extremely competitive. It is certain that the manufacturing systems are the basis of industrial production and they must be flexible in order to successfully solve all the requirements of shorter time delivery of complex products that are made on them. In the market today, there are various machine tools, as part of the machining system, and their proper selection in purchasing is critical for their further exploitation and utilization. This article gives an overview of trends in the development of modern machine tools and their basic modules and can assist in their proper choice.

Although the manual mode of stone carving is still quite frequent, modern world's need faster and more precise production of engraving and stone surfaces. Today, the stone market has become more selective and demand for special product and service is greater. Big problem in stone branches is large surface area, large dimension and weight of the stone workpiece that can't be produced by typical machine for stone engraving. In these situations portable stone carving machine can solve that problems, because the machine has less mass and easier to put the machine on the workpiece than the workpiece on the machine. It will also greatly reduce work time and increase productivity. This paper gives the design of portable carving machine which can be used for machining the engravings on large and non movable stone surfaces.

A synthetic liquid (5 % water solution) was used during the fine grinding of alumina (Al2O3) ceramics. In order to characterize the synthetic liquid, its physical and chemical properties, corrosion protection, foaming, coolant and lubricant properties were determined. These parameters were determined before machining and after fine grinding. The liquid contains particles of the treated material after fine grinding. Therefore, the particle size distribution was determined in order to select a method for removing solid particles before the liquid is reused. Results of investigation indicated that the physical and chemical properties of the used synthetic liquid did not change after machining, which means that the liquid can be reused after an adequate solid-liquid separation method has been applied.

Zbog velike konkurencije, industrijska poduzeća širom svijeta prisiljena su smanjiti troškove proizvodnje i proizvoditi kvalitetnije i ekonomičnije. To znači da je i cilj modernih postupaka brušenja ostvariti maksimalnu proizvodnost i time učiniti postupak brušenja optimalnijim. Želja za što većom proizvodnošću postupka brušenja, prikazane pomoću reduciranog učina brušenja, može neželjeno dovesti do prekoračenja graničnih uvjeta brušenja, a time i do neispravnosti postupka. To se očituje u spaljivanju brušene površine i pojavi ostalih pogrešaka brušenja. U radu su prikazani rezultati istraživanja i određivanja vrijednosti granične proizvodnosti postupka brušenja za konkretni materijal, a u ovisnosti o promjeni parametara brušenja.

Cutting tool wear is a consequence of a normal wearing process, which is considerably slow, or of a chipping process, which happens instantly and could often lead to tool breakage. The paper presents a methodology for monitoring the tool chipping process. The reliability of monitoring the tool chipping, in particular its initialization, depends on the sensor signal acquisition, processing, and interpretation. Tool chipping is a very fast nonlinear process, and too complex to be described by deterministic models. Not only the cutting process itself, but also the mechanical link (from motors to tool-workpiece interface) is a significant cause of signal deviation and noise. Therefore, knowing the signal power spectra and analyzing them are of great importance for the monitoring of stochastic processes. This paper presents an analysis of the tool chipping process by means of a nonparametric method for the spectral analysis of force, current, and acoustic signals.

Because of its significant advantages of low thermal influence on workpiece and possibility of cutting different type of materials, the abrasive water jet cutting is more and more present in industry. One of the bigger costs during abrasive water jet cutting is the cost of abrasives. Recommended and required abrasive flow rate is mostly determined by type of workpiece material and its thickness and pump pressure. In intent to reduce the abrasive mass consumption in cutting, some experiments were done and the paper presents the results of changing the abrasive flow rate (mass flow) and its influence on surface cut quality in abrasive water jet cutting. Abrasive saving possibility and also the influence of cutting nozzle distance from workpiece surface on surface cut quality in abrasive water jet cutting are discussed in this paper.

Za uspješno poslovanje na sve zahtjevnijem globalnom tržištu, potrebno je zadovoljiti zahtjeve kupaca, rješavajući njihove potrebe i/ili probleme. Od proizvoda se zahtijeva sve veća mogućnost izmjena, sve veća kompleksnost, sve kraće vrijeme isporuke, a njihov životni vijek na tržištu je također sve kraći. Stoga se proizvodne tvrtke vrlo često suočavaju s potrebom uvođenja novih proizvoda i inovacijama postojećih, promjenjivim količinama i kombinacijama proizvoda, novim materijalima, novim zakonskim regulativama i novim tehnologijama. Kako bi ostale, ili postale, kompetitivne na globalnom tržištu moraju primjenjivati suvremene proizvodne sustave i tehnologije koje mogu ispuniti takve zahtjeve.

Machinability is assessed by a set of criteria or machinability functions, the knowledge of which is needed in optimising the machining process. New cutting tool materials and new concepts of the machine tools provide new possibilities and cause quantitative changes in machinability functions. This research has studied the cutting forces function, as one of the crucial machinability functions. The research was done at longitudinal turning of steel 16MnCr5. Coated carbide inserts for roughing and finishing with different inclination angles were used, and tool clamping system has enabled the changes of entry angle. Obtained results confirm that entry angle and geometry of cutting insert significantly influence cutting forces especially thrust cutting force. Obdelovalnost lahko ocenimo z nizom kriterijev oz. obdelovalnih funkcij, poznavanje katerih je nujno za optimizacijo obdelovalnega postopka. Novi materiali rezalnih orodij in nove zasnove obdelovalnih orodij zagotavljajo nove možnosti in omogočajo količinske spremembe obdelovalnih funkcij. V tej raziskavi smo raziskali funkcijo rezalnih sil, kot eno izmed bistvenih obdelovalnih funkcij. Raziskavo smo opravili pri vzdolžnem struženju jekla 16MnCr5. Uporabili smo oplaščene karbidne ploščice za grobo in končno obdelavo z različnimi koti. Vstopne kote smo spreminjali s sistemom za vpenjanje orodja. Dobljeni rezultati so potrdili. da vstopni kot in geometrijska oblika ploščic zelo vplivata na rezalne sile, se posebej na potisno rezalno silo.

Open structure of modern digital controls open up new possibilities and prospects in monitoring of machining systems and processes. In many cases, the combination of digital plant signals and internal data of the machine control system, along with advanced methods of signal analysis can replace the external control systems. The integration of process control software module into the machine control system allows fast reactions should there be any process disturbances, without any additional hardware expansion. This paper studies the sensitivity of signals contained in the control system to the cutting tools wear processes in face turning.

Due to its advantages over turning noted so far, the process of orthogonal turn-milling deserves a systematic research and analysis in order to give incentive to its wider application. This paper gives an analysis of the suitability of this machining process. For the purpose of a comparative estimation of the process, a set of criteria (functions) and methods are proposed and defined. On the basis of the defined set, the suitability of orthogonal turn-milling is studied and compared with turning, with special attention given to the conditions of high-speed machining.

Plastic deformation and chip formation machanisms form the basis of material removal processes and according to that all materials can be separated into two groups. The first group encompasses materials with plastic properties (metals, plastic materials, composites, etc.) and the second group consists of hard and brittle materials, i.e. materials with low plasticity (glass, ceramics, stone, etc.). Due to their low plasticity, machining of brittle materials has some specific characteristics. Considering that data on the machining of these materials can be rarely found in literature, this paper gives some investigation results in the machining of glass as a representative of hard and brittle materials. Glass is primarily a decorative material and its purpose depends on the visual effect of machined surface. A comparison of the surface quality obtained by different material removal processes is presented using the example of glass machining. The paper also presents the investigation of the influence of cutting parameters (cutting speed and feedrate) on surface quality in final machining phase, i.e. the polishing of glass.

Manufacturing of foot orthotics is typical example of custom made production. As it possess a characteristic of mass production (it is evident that same concept could be applied in shoe production industry), manufacturing of foot orthotics could be considered as an example of mass customization concept. This work describes prototype of automated system for manufacturing of accommodative custom foot orthotics, and it is developed on Faculty of Mechanical Engineering and Naval Architecture University of Zagreb. System encompasses component for foot scanning, CNC machine tool with subsystem for chip suction, subsystem for workpiece and insole handling, and software. Foot scanning is done by laser and digital camera ; machining is done with 4-axis milling machine tool with two coaxial, opposite milling spindles, each one machining different surface ; workpiece handling is done by pneumatic cylinders ; software is developed using visual studio package. System is automated and autonomous when applied for accommodative insoles but it could be also applied for other type of insoles and other products.

Tool path generation for NC machine tools is one of the basic tasks in NC modules of CAD/CAM systems. In the conditions of global market and application of newer technologies of material removal, such as high speed machining and hard machining, tool path shape gains multiple significance. Aside necessity to generate geometrically correct tool path, collision free even for the most complex multiaxes machining, tool path should be also optimized considering machining time and constant chip cross-section in order to avoid vibration by having constant cutting forces. The majority of CAD/CAM systems, while calculating machining time, do not consider acceleration and deceleration time or adaptation of contouring speed in general, what could result in significant differences between calculated machining time and effectively used time for machining. The paper presents the results of experimental investigation of influence of tool path shape on the machining time while keeping constant value of toll path length. The results proved significant influence of tool path shape and programmed contour speed on the machining time. All experiments showed that exact machining time was longer then calculated machining time, and differences in machining time reached as high as 50%.

This paper presents a novel method for the computational balancing of the rotor wheels. The method is based on a CAD modelling of the element (rotor wheel or a similar machine part) and subsequent calculation of the task-specified correction values, using the self-developed macros-based software. After the correction values have been read into the CAD model, the model can easily be modified by mouse-clicking only. The model and workshop drawings of the updated model, as well as the APT source which gives an NC-program by postprocessing, are then generated automatic ally. The complete procedure can be incorporated into the CATIA environment which enables fast and comprehensive solution process.

In the case of fracture or crack of human bones, a surgery method gives the best healing results because a traumatologist drills the bone, sets the immobilization screws and plates and with that procedure achieves an optimal immobilisation. A problem occurs if during the bone drilling, the maximal temperature of the bone tissue around the hole increases above some critical limit. This may result in thermal necrosis, which means the irreversible death of the bone cells around the drilled hole and the consequence is that immobilisation screw joint comes loose over time. In order to find a solution to the problem of reducing maximal bone drilling temperature, this paper studies the problem and presents the results of measuring the maximal bone drilling temperature in a high-speed drilling process with a step drill and a classic surgical type of the drill.

Lightweight structure concepts play an important role both in automobile and transport industries and in the manufacture of modern machine tool parts as well. Modern high dynamic machine tools use feed drives capable of high speeds, acceleration and deceleration. It is also important to damp potential vibrations that may occur during the machining in order to obtain high quality workpiece surface. One of recent solutions in the construction of high dynamic machine tool parts is the use of metal foams as materials for fast-moving elements. Metal foams are low density materials with high strength and rigidity as well as good damping capacity. Therefore, their application in the manufacture of modern dynamic machine tool parts is the object of intensive research. This paper presents the results of researches into the production technology of profiles filled with aluminium foam carried out at the Foundry Chair at the Faculty of Mechanical Engineering and Naval Architecture in Zagreb.

Machinability is assessed by a set of criteria or machinability functions, the knowledge of which is necessary in optimising the machining process. New cutting tool materials and new concepts of the machine tools provide new possibilities and cause quantitative changes in machinability functions. This work has studied the cutting forces function, as one of the crucial machinability function. The research was done at longitudinal turning of steel 16MnCr. Coated carbide inserts for roughing and finishing were used, and tool clamping system has enabled the changes of entry angle.Obtained results confirm that entry angle and geometry of cutting insert significantly influence cutting forces especially thrust cutting force.

In case of fracture or crack of human bones, the most important is to return the bone parts as precisely as possible into their previous positions. The operative or surgery method in that case is the best. During the surgery traumatologist drill the bone in order to set the immobilization screws and plates and the goal is to insure maximum avoidance of motion of the fracture bone parts i. e. to achieve optimal immobilisation. During bone drilling, the surrounding tissue is heated and if the maximal temperature of the bone tissue around the bore increases above some critical limit, this may result in thermal necrosis (death of the bond cells around the drilled bore). The consequence of thermal necrosis is that immobilisation screw joint loose over time. This paper presents the results of research realised in measuring the maximal bone drilling temperature depending on some technological parameters and type of the drill.

Bone drilling is a frequent procedure applied as a first step for immobilisation of bone fracture. The next step is insertion of immobilization screws and plates. The drilling is performed with surgical drills. If the amount of heat, generated by drilling process, increases the temperature of the bone tissue above the critical limit, possible outcome (it may result in) is thermal necrosis. This paper presents the results of research conducted in order to establish a distribution of temperature fields in the region around drilled bore .Obtained results confirm the ranking of different drill types established by comparing cutting forces and maximal bone drilling temperature.

Machinability is assessed by a set of criteria or machinability functions, the knowledge of which is necessary in optimising the machining process. New materials of the cutting tools and new concepts of the machine tools provide new possibilities and cause quantitative changes in machinability functions. This work has studied the cutting forces function, as one of the crucial functions of machinability. The research was done by longitudinal turning the steel 16MnCr5, using the tools made of coated carbides, without the usage of coolants. Obtained results confirm that entry angle significantly influence thrust cutting force, Fp, and therefore is one of the key factors when turning workpieces with high ratio l/d.

Metal foams belong to the group of materials with low density and very good combination of mechanical, electrical, thermal and acoustic properties. Using all the advantages they have regarding homogeneous materials, they can be used for ultra-light structures, energy absorption and for the fabrication of heat exchangers. The development of techniques for the production of metal foams began in the 50s of the last century. The reason for their not having been implemented in practice until today lies in the expensive and complex equipment and in the complexity of the foaming process. [1, 2, 3, 4 and 5]

Specific main grinding force in machining by means of defined geometry cutting tools, such as e.g. turning operation, milling, drilling, has been studied for various workpiece materials and chip cross-sections. The previous testing has shown such dependence of the specific main cutting force on the chip cross-section , that the increase in the chip cross-section reduces the value of the specific main cutting force. Although this field has not been sufficiently studied in grinding processes, similar dependence of the specific main grinding force is expected on the equivalent grinding thickness. With adequate conditions of grinding and dressing of the grinding wheel cutting surface this paper measures the reduced main grinding force, and calculates the specific main grinding force and the equivalent grinding thickness, thus determining their interdependence.

Surgery in case of bone fractures can be performed in two basic ways. The first method is conservative, without direct action on the bone, whereas the other, operative method is more advanced but requires direct contact with the bone. In the latter case, the traumatologist uses various tools and equipment in order to re-establish the primary physiological position of the fractured parts. One of the operative procedures includes also bone drilling in order to set the immobilization screws and plates. During bone drilling, the surrounding tissue is heated. If the amount of developed heat near the bore is high enough to increase the temperature of the bone tissue above the critical limit, this may result in thermal necrosis. The death of the cells due to the thermal necrosis around the drilled bore causes them to lose their adequate properties, and the screw joint gets loose over time. This work studies the influence of some of the technological parameters on the bone drilling temperature increase and recommends improvements in the selection of the technological parameters and geometry of the drill.

Orthogonal turn-milling is replacing turning because of its advantages such as: higher productivity of the procedure, shape of chip, and longer tool life. By using high speeds the centrifugal forces of workpiece clamping devices during turning represent a significant limitation, thus rendering turn-milling an even greater importance. Therefore, the procedure deserves to be systemically analysed and compared to turning. The theoretical analysis and comparison of the geometry of the machined surfaces also gives advantage to orthogonal turn-milling. This provides knowledge and guidelines for further experimental research.

Orthogonal turn milling is used in the production of rotating and curved surfaces. This means that both the workpiece and the tool rotate with perpendicularly set axes. This results in a complex kinematics of the process as a significant feature stipulating a whole series of strict requirements, especially regarding the cutting tools. The cutting tools have to comply with high quality requirements of the machined surface, reduce the possibility of vibrations and meet high-speed machining requirements. This is the topic of the paper.

With high speed cutting, in particular high speed milling, it is possible to obtain the machined surfaces of a such quality that is, with classical approach, obtained by grinding. This paper presents the results of comparison of characteristics of machined surfaces belonging to the same surface roughness category, but obtained by two different machining processes, grinding and high speed milling. By comparing a number of parameters defining surface roughness and waviness, it is possible to answer if there are the differences in topography characteristics of the surfaces obtained by grinding and high speed milling that could influence tribological behavior of the surface.

The grinding wheel cutting surface consists of undefined and unevenly distributed edges, space between them, as well as the pores. The value of the chips space on the grinding wheel cutting surface depends on the wheel specification , the method and conditions of dressing. In order to carry out the grinding process well, free of grinding defects on the ground surface, the possible loading of the grinding wheel cutting surface should be studied. This paper considers the equivalent grinding thickness parameter as load criterion of the grinding wheel cutting surface. It also provides an analysis of the influence of the grinding conditions, methods and dressing conditions of the grinding wheel cutting surface on its value.

The quality of the grinding process depends among other things also on the load exerted on the grinding wheel cutting surface, influenced to a great extent by the value of the equivalent grinding thickness. The grinding wheel cutting surface with its edges and the space between them, as well as the pores, has the task to bring grinding fluid into the grinding zone and to position and remove chips from the grinding contact. The grinding wheel cutting surface represents thus the grinding cutting tool, which obtains its initial characteristics by dressing the grinding wheel cutting surface and these characteristics in turn influence the loading possibility. This paper considers the equivalent grinding thickness as load criterion of the grinding wheel cutting surface. It also provides an analysis of the influence of the grinding regime, method and dressing conditions of the grinding wheel cutting surface and the processing material on its value.

The burn or surface oxidation of ground surface is one of the first indicators of incorrect grinding process. Burning can be smaller or greater, so it is possible to talk about the burn intensity of the ground surface. In this paper the burn intensity has been determined and presented by means of the surface lightness interval, which has lower and upper value, and measurements were carried out on the Image Analysis System LECO2001. The lower value of the surface lightness interval describes the darker colour of ground workpiece or analysed image, and the upper value is the lighter colour. The lower value of the surface lightness interval SVd , is more relevant for determination of the burn intensity, since it describes greater burned ground surface of the workpiece. The paper represents some results of investigation of dependence of lower value of the surface lightness interval on dressing and grinding conditions.

Tendency towards bigger production of grinding process can undesirably lead to exceeding of critical grinding conditions and incorrect grinding process. The consequences are grinding defects in the subsurface layer. The work investigate dependence of burn intensity and other grinding defects on reduced material removal rate value Qbr , which represents productivity. The burn intensity of the ground surface is determined by surface lightness interval, which has upper and lower value, and measuring were done by Image Analysis System LECO 2001. The results have shown that by exceeding the reduced limited material removal rate value, all samples have greater burn intensity, darker colour of surface and the lightness interval is lower. Besides that, the other grinding defects occur at the ground surface. These confirmed that with lightness interval of ground surface it is possible to determine the critical burn intensity of ground surface, which estimates limited grinding productivity value. In this work the critical burn intensity is determined by parameter named critical grinding surface lightness, SVg-br , which estimate the reduced limited material removal rate i.e. limited grinding productivity value, for each workpiece material.

The increase of grinding productivity can results in incorrect grinding and the consequence is the occurrence of grinding defects on the ground surface. The work investigate the grinding burn intensity, the change of surface layer hardness and the layer depth of variable workpiece hardness, on increasing of grinding productivity. Experiment was done for different workpeace materials and for different grinding wheel topography. The results have shown that the increase in grinding productivity results in an increase of burn intensity, reduction of the surface lightness interval value, and an increase in the change of surface layer hardness and the layer depth of variable workpiece hardness.

The productivity increase of the grinding process expressed by reduced material removal rate can result in incorrect grinding and the consequence is the ground surface burn and occurrence of other grinding defects on the ground surface. The paper studies the burn intensity of the ground surface and other grinding defects in different material samples, depending on the increase of grinding productivity. The ground surface burn intensity has been determined by means of the surface lightness interval, with the upper and lower value, and measurements were carried out on the Image Analysis System LECO2001. The results have shown that the increase in grinding productivity on all the ground material specimens results in an increase of burn intensity, reduction of the surface lightness interval value, and an increase in the change of surface layer hardness and the layer depth of variable workpiece hardness. Therefore, the surface lightness interval values, i.e. the burn intensity of the ground surface can determine the correctness of the grinding process and approximate limited productivity.