Jan Burek

Traverse grinding of low-stiffness shafts with the use of a grinding wheel’s path correction

This paper presents a method of increasing the shape and dimensional accuracy of low-stiffness shafts manufactured in traverse grinding process. In order to achieve that, grinding force measurement was used. It allowed to calculate such a correction of a grinding wheel’s path, that allowed to decrease dimensional and shape errors of grinded workpieces.

Analysis of the geometry reconstruction accuracy of the anatomical structure using industrial tomography and laser head

Reverse engineering is a process that allows to recreate the geometry of an existing object [1,2]. It is used in many fields, including in medicine. The geometry of the anatomical structure model can be reconstructed in two ways in which the measurements are performed on the living body or outside it. Using the medical path, it is possible to reconstruct the geometry of anatomical structures [3,4] and to make surgical templates [5] and ready implants [6]. The nonmedical path is mainly a supplement to the medical path. Coordinated measuring systems used in this path are mainly used to verify the accuracy of models used in the medical industry [7], as well as to design orthoses stabilizing joints [8]. Each stage of the medical and non-medical path influences the accuracy of the reconstruction of the models geometry. One of the key steps is the acquisition of data the appropriate selection of the system, parameters and measurement strategy determines the quality of the obtained data [9,10]. The stage of data processing usually starts with the process of digital filtration, consisting in removing the noise found in 2D images (in the case of a medical path) and point clouds (in the case of a non-medical path). After filtration, a full model geometry is obtained, however, in the case of a medical path, the segmentation process is additionally performed. It is used to isolate the anatomical structure from 2D images through the use of various methods, based mainly on edge detection and identification of image areas that are characterized by some common features [11]. In both reconstruction methods, the reconstructed geometry is usually triangulated, leading to a faceted surface that requires additional editing, including the reversal of normal vectors and the removal of holes between triangles [11]. The finished model, represented by the faceted surface, can be manufactured using various additive techniques [12, 13]. Further modeling is also possible, consisting in covering the polygonal mesh with elementary surfaces [14]. The obtained model can be exported using various CAD data exchange formats, such as *.iges or *.step, or it can be used to execute a machining program on computer numerical controlled machines [15].

Simulation tests of the cutting force in the process of machining of ruled surfaces with a conical mill

Five-axis milling technologies are now used to produce geometrically complex parts for the aerospace industry, such as turbine blades and rotors, and compressors. However, processing such complex elements is still a technological problem. On the one hand, this results from the required dimensional and shape accuracy as well as high surface quality, on the other hand from the desire to maximize the efficiency of the process [6-8, 10]. Most often machining of complex surfaces is used in the rounding with the ball nose end mill strategy. It allows to make surfaces of any shape. The disadvantage of this strategy is that it has very low efficiency. In the case of machining of ruled surfaces, it is possible to use conical tool for flank milling (fig. 1) and obtain much higher machining efficiency compared to the possibilities offered by common strategy [8, 10]. a) b)

Cylindricity error measurement and compensation in traverse grinding of low-stiffness shafts

Axio-symmetric parts account for nearly half of the parts manufactured for the needs of the engineering industry. Among them, about 12% are shafts with low stiffness, i.e. those in which the length-to-diameter ratio l/d is greater than 10. They are used in many industries, including in the aviation industry (turbine shafts, spring shafts, elastic and torsional shafts), tool (drills, reamers, special tools), machine tools (rotor, pumps and generators shafts, guides) or automotive (driveshafts, axle-shafts) [1, 2]. Shafts with low stiffness are usually made of highstrength alloy steels. Typical methods of their machining include external turning and grinding. Turning machining should provide 8÷11. tolerance class and roughness Ra = 0.63÷2.5 μm, while grinding operation 5th or 6th tolerance class for roughness Ra < 0.63 μm [3]. The low stiffness of parts causes problems with achieving the required shape and dimensional accuracy. During grinding of such parts, elastic deformation occurs, resulting in errors in the cylindricity and dimension of the parts being made [4]. Many studies show that the pliability of the tailstock and headstock centers and the workpiece whose length / diameter ratio is greater than 10 is about 90% of the total machine tool – tool workpiece systems pliability [5]. Fig. 1 shows the elastic displacements of these elements. The elastic displacement of the workpiece x1, resulting from the displacements of the headstock center xw and the tailstock center xk can be calculated from the following equation:

The influence of the cooling method on high performance cutting of the AlZn5.5MgCu alloy

Aluminum parts with complex shapes are usually produced in small series. For complex aluminum structures, thin-walledness and a large number of closed areas of relatively high depth are characteristic. The implementation of a single aerial support structure sometimes requires removing more than 90% of the material from the semifinished product. For economic reasons, it is necessary to abandon production methods that are difficult to automate, such as work and time-consuming riveting of the wing construction elements or the fuselage of the aircraft. The production efficiency is increased by increasing the machining parameters, such as axial infeed ap, radial ae, cutting speed vc and feed per tooth fz [1, 4-6, 8]. For these reasons, new machining methods have emerged, such as machining with high cutting speeds HSC (high speed cutting) and high-performance machining HPC (high performance cutting). HSC machining is mainly used at the finishing stage, and its advantages include increased productivity, reduced energy impact of the tool on the workpiece and improved quality of the work surface. In contrast to the HSC treatment, the HPC method is mainly used in the roughing stage. It ensures a significant reduction of production time and costs. However, both methods also have some practical limitations [1, 4, 6, 8]. They mainly result from high values of machining parameters such as ap, ae and fz, and large crosssections of the cutting layer, which in turn affect the increase of the values of the cutting force components. An equally big problem is the need to quickly evacuate a significant amount of chips, which results from the difficult access of cooling-

Zastosowanie systemu Omative w obróbce łopatki turbiny ze stopu Inconel 718

The modern aviation industry is increasingly demanding its components, while striving for maximum efficiency and maximum profit. New construction solutions make it necessary to use special materials such as heatresistant super alloys. These are alloys based on nickel, cobalt or iron. Of these, one of the best properties is Inconel 718 [1, 2]. The advantages of this alloy are particularly important in those engine points that are subjected to the largest loads. The turbine blades work in the most difficult temperature and load conditions. The blade end speed reaches 390 m/s, the gas temperature is even 1200 °C and their speed is 600 m/s. The turbine blade material, in addition to high strength, must be characterized by high heat resistance, high temperature creep resistance, corrosion and oxidation resistance and high hardness. Density of the alloy, which affects the weight of the engine, is also important in generating centrifugal forces [3, 4]. Inconel 718 is one of the hardest materials to work on. Blade locks are currently being successfully developed in the Creep-Feed Grinding (CFG) process. This method allows for efficient machining of elements made of super alloys and other hard-working materials. It allows the parts to be polished after heat treatment and ensures high surface quality [5]. On the other hand, in the case of free surfaces of the blades, the method of their execution is simultaneous process of five-axes milling. Due to the complexity of this machining, the presence of high milling strength components and the high cost of the workpiece and tooling, it is legitimate to use a system that monitors the correctness of the cutting process. They are based on the measurement of selected physical quantities, such as: cutting force, vibration, power and engine torque, sound emission or coolant flow. Measured signals (after processing) serve to obtain process measures

Programowanie obróbki wiertła stopniowego pełnowęglikowego z wykorzystaniem systemu MTS

In the aerospace and automotive industries, progressive carbide step drills are commonly used. Appropriate tool geometry including the shape of the flute, the number of teeth and their type, and especially variant of the drill correction used has a significant influence on the drilling parameters. These parameters determine the drilling power, temperature, chip evacuation and tool life. Therefore, to obtain the right drill geometry is so important at the design stage. For this reason, we are constantly looking for the right macro and microgeometry of the drill, adapted to the required machining conditions. The paper presents the process of programming the exemplary step drill geometry and its machining process using the MTS system [1, 2, 3, 4, 5].

Cutting layer and cutting forces in a 5-axis milling of sculptured surfaces using the toroidal cutter

The purpose of this article was to evaluate the significance of the influence of fiveaxis orientation parameters of a toroidal cutter axis and the geometrical parameters of the machined sculptured surface on the intersection of the cut layer in a 5-axis machining. An impact assessment was performed by simulating concave-convex and convex-concave surfaces using a discrete method of direct transformation in a CAD environment. It was shown that only the radius of curvature of the surface in the feed direction and the angle of the tool axis affected the change in the intersection of the cutting layer. Subsequently, experimental tests were conducted that aimed at determining the mathematical models of the influence of these important parameters on the components of the cutting force. The object of the experimental studies was a convex and concave surface of a turbine blade of Inconel 718 alloy. The R300-016B20L-08L Sandvik Coromant toroid cutter was used for the tests. Based on the results of the study it was found that the lead angle in the machining of the convex surface and concave turbine blade should be continuously varied with the change of radius of curvature in the direction of the machined surface profile.

The influence of the cutting edge shape on high performance cutting

Purpose The purpose of this paper is to determine the influence of the shape of a cutting edge on high-performance milling high-performance cutting. The main purpose of the test was to determine the possibility of increasing the efficiency of machining AlZn5.5CuMg alloy, which is used mainly for the thin-walled structural aerospace components. Design/methodology/approach In all, eight cutters for machining aluminum alloys with different shape of the cutting edge (1 – continuous, 4 – interrupted, 3 – wavy) were tested. The influence of different shapes of a cutting edge on cutting force components and vibration amplitude was analyzed. Furthermore, the impact of a chip breaker on the form of a chip was determined. Findings The conducted test shows that using discontinuous shapes of a cutting edge has impact on the reduction of the cutting force components and, in most cases, on the increase of vibration amplitude. Moreover, using a chip breaker caused significant chip dispersion. The optimal shape of a cutting edge for cutting AlZn5.5CuMg alloy is fine wavy shape. Practical implications Potential practical application of the research is high-performance milling of AlZn5.5CuMg alloy, for example, production of thin-walled aerospace structural components. Originality/value Different shapes of a cutting edge during high-performance milling of aluminum alloy were tested. The influence of tested geometries on HPC process was determined. The most favourable shape of a cutting edge for high-performance cutting of AlZn5.5CuMg alloy was determined.

Five-axis milling of sculptured surfaces of the turbine blade

Purpose The purpose of this paper is to determine the influence of a toroidal cutter axis orientation and a variable radius of curvature of the machined contour of sculptured surface on the five-axes milling process. Simulation and experimental research performed in this work are aimed to determine the relationship between the parameters of five-axes milling process and the shape and dimensional accuracy of curved outline of Inconel 718 alloy workpiece. Design/methodology/approach A subject of research are sculptured surfaces of the turbine blade. Simulation research was performed using the method of direct mapping tools in the CAD environment. The machining research was carried out with the use of multi-axis machining center DMU 100 monoBLOCK DMG, equipped with rotating dynamometer to measure the components of the cutting force. To control the shape and dimensional accuracy, the coordinate measuring machine ZEISS ACCURA II was used. Findings In this paper, the effect of the toroidal cutter axis orientation and the variable radius of curvature of the machined contour on the parameters of five-axes milling process and the accuracy of the sculptured surfaces was determined. Practical implications Five-axes milling with the use of a toroidal cutter is found in the aviation industry, where sculptured surfaces of the turbine blades are machined. The results of the research allow more precise planning of five-axes milling and increase of the turbine blades accuracy. Originality/value This paper significantly complements the current state of knowledge in the field of five-axes milling of turbine blades in terms of their accuracy.