Vibration surveillance for efficient milling of flexible details fixed in adjustable stiffness holder

The paper presents the results of research related to the possibility of using an intelligent workpiece holder with adjustable stiffness, during end milling process. Machining a one side supported flexible workpiece will be performed with constant spindle speed and feed speed. In order to avoid hazardous vibration, stiffness of the especially designed spring (mounted in a workpiece holder) will be modified off-line. In order to predict the accuracy of the proposed method, appropriate simulations were performed. As a simplified model of the flat workpiece it was applied the Euler-Bernoulli bar with possibility of identifying the two lowest normal modes. On this basis and for approaching optimal spindle speeds, the mean of adjusting relevant stiffness of the holder is invented

Engineering and Management of Space Systems (EMSS) - an international joint Master's double-degree program

Dynamic development of the space sector of European, and especially of Polish and German economies results in a necessity for suitable Higher Education Institution graduates. The increasing digitization, distribution and networking of technical systems leads to the necessity of a degree programme teaching “the systems view” and “interdisciplinarity” methods and skills. Furthermore, it is necessary to consider the entire life cycle of the systems starting with the analysis of the requirements, through design, integration, verification, to operation and maintenance, with supplementation of management, social and intercultural skills. Since interdisciplinarity and internationality are essential for engineering and management of space systems, the international project was launched early last year by two universities – Hochschule Bremen (Bremen City University of Applied Sciences, HSB, Germany) and Politechnika Gdańska (Gdańsk University of Technology, Gdańsk Tech, Poland) establishing an international interdisciplinary joint Master's double-degree program - Engineering and Management of Space Systems (EMSS). It consists of three different fixed three- or four- semester study paths of several mobility schemes, though individual educational pathways adjusted to students' preference are also allowed. Each path includesa joint academic year – first semester is conducted in Gdańsk, the second in Bremen. The remaining semesters can be studied at either of the universities. All of the EMSS curricula meet the highest education standards of both countries. Several mandatory modules and many elective courses are included in the EMSS curricula. Upon graduation, students of the program are awarded two Master’s degrees - in Space and Satellite Technologies, issued by Gdańsk Tech, and, depending on the chosen study path, in Aerospace Technologies, Computer Science, or Electronics Engineering issued by HSB. Work on the establishment of a new, international, joint field of study - Engineering and Management of Space Systems, run by both universities is currently in progress. The curriculum of the new study programme will be based on the recommendations of the International Council On Systems Engineering (INCOSE) and its German Chapter, Gesellschaft für Systems Engineering (GfSE), and will offer the possibility of certification as a Systems Engineering Professional, Associate Level. This paper includes the lecturers’ and students’ perspective on the program and its future development

Modelling and Simulation of a New Variable Stiffness Holder for Milling of Flexible Details

Modern industry expectations in terms of milling operations often demand the milling of the flexible details by using slender ball-end tools. This is a difficult task because of possible vibration occurrence. Due to existence of certain conditions (small depths of cutting, regeneration phenomena), cutting process may become unstable and self-excited chatter vibration may appear. Frequency of the chatter vibration is close to dominant natural frequency of the workpiece or the tool. One of the methods of chatter vibration avoidance is matching the spindle speed to the optimum phase shift between subsequent cutting edges passes (i.e. the Liao-Young condition). However, the set of optimum spindle speeds from the point of view of vibration reduction may be not optimum one from other points of view. For example milling efficiency or machine tool capabilities cannot be assured. This article presents the idea of a workpiece holder with adjustable stiffness and discusses a new variant of its realization. In the holder, milling process is performed at constant spindle speed and feed speed. In order to avoid vibration the holder stiffness is modified. Stiffness changes modify natural frequencies of the workpiece and thus it is possible to modify dynamic properties of the workpiece in such a way that arbitrary chosen, constant spindle speed will be optimum, due to the Liao-Young condition performance. Calculation of the optimum stiffness is performed before milling, based on the workpieces modal identification results and the finite element model simulations

Engineering and Management of Space Systems (EMSS) - an international joint Master's double-degree program

Dynamic development of the space sector of European, and especially of Polish and German economies results in anecessity for suitable Higher Education Institution graduates.The increasing digitization, distribution and networking of technical systems leads to the necessity of a degree programme teaching “the systems view” and “interdisciplinarity” methods and skills. Furthermore, it is necessary to consider the entire life cycle of the systems starting with the analysis of the requirements, through design, integration, verification, to operation and maintenance, with supplementation of management, social and intercultural skills. Since interdisciplinarity and internationality are essential for engineering and management of space systems, the international project was launched earlylast year by two universities – Hochschule Bremen (Bremen City University of Applied Sciences, HSB, Germany) and Politechnika Gdańska (Gdańsk University of Technology, Gdańsk Tech, Poland) establishing an international interdisciplinary joint Master's double-degree program - Engineering and Management of Space Systems (EMSS). It consists of three different fixed three- or four-semester study paths of several mobility schemes, though individual educational pathways adjusted to students' preference are also allowed. Each path includesa joint academic year – first semester is conducted in Gdańsk, the second in Bremen. The remaining semesters can be studied at either of the universities. All of the EMSS curricula meet the highest education standards of both countries. Several mandatory modules and many elective courses are included in the EMSS curricula. Upon graduation, students of the program are awarded two Master’s degrees - in Space and Satellite Technologies, issued by Gdańsk Tech, and, depending on the chosen study path, in Aerospace Technologies, Computer Science, or Electronics Engineering issued by HSB. Work on the establishment of a new, international, joint field of study -Engineering and Management of Space Systems,run by both universitiesis currently in progress.The curriculum of the new study programme will be based on the recommendations of the International Council On Systems Engineering (INCOSE) and its German Chapter, Gesellschaft für Systems Engineering (GfSE), and will offer the possibility of certification as a Systems Engineering Professional, Associate Level. This paper includes the lecturers’ and students’ perspective on the program and its future development.75576

Selected Aspects of 3D Printing for Emergency Replacement of Structural Elements

The paper presents a synthetic characterization of modern methods of manufacturing or regenerating machine elements. Considered methods are machining and additive methods, in particular 3D printing in the FDM/FFF technique. For the study, the authors made samples of the holder bracket using selected methods. Samples made by machining operations, 3D printing with various filling were tested. The paper contains a technical and economic analysis of the production of a holder bracket using the discussed methods. The dynamics of steel and FDM/FFF printed samples were also assessed by determining their resonance curves. The vibration magnification fac-tors were analyzed - the quotient of the vibration amplitudes in the resonance to the static deformations that occurred under the influence of the constant force and the location of the vibration resonances - the natural frequencies for individual vibration modes. The study's main objective is to assess the possibility of emergency changing the manufacturing technology of selected machine components. The authors were interested in partially replacing costly and not environmentally friendly milling with 3D printing. Machine elements can be manufactured by printing in classical machine building and emergency conditions to replace a damaged component temporarily (e.g., on a ship, for the time of arrival at a port or shipyard). The main assumption guiding the authors during the preparation of this publication was the analysis of the possibility of using the production of "ad hoc" prepared spare parts and their use in the event of a lack of access to parts made of the intended materials

Modelling and Simulation of a New Variable Stiffness Holder for Milling of Flexible Details

Modern industry expectations in terms of milling operations often demand the milling of the flexible details by using slender ball-end tools. This is a difficult task because of possible vibration occurrence. Due to existence of certain conditions (small depths of cutting, regeneration phenomena), cutting process may become unstable and self-excited chatter vibration may appear. Frequency of the chatter vibration is close to dominant natural frequency of the workpiece or the tool. One of the methods of chatter vibration avoidance is matching the spindle speed to the optimum phase shift between subsequent cutting edges passes (i.e. the Liao-Young condition). However, the set of optimum spindle speeds from the point of view of vibration reduction may be not optimum one from other points of view. For example milling efficiency or machine tool capabilities cannot be assured. This article presents the idea of a workpiece holder with adjustable stiffness and discusses a new variant of its realization. In the holder, milling process is performed at constant spindle speed and feed speed. In order to avoid vibration the holder stiffness is modified. Stiffness changes modify natural frequencies of the workpiece and thus it is possible to modify dynamic properties of the workpiece in such a way that arbitrary chosen, constant spindle speed will be optimum, due to the Liao-Young condition performance. Calculation of the optimum stiffness is performed before milling, based on the workpieces modal identification results and the finite element model simulations