THE SHAPE ACCURACY ANALYSIS OF MACHINE PARTS PRODUCED BY METAL SPINNING

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1 KOMISJA BUDOWY MASZYN PAN ODDZIAŁ W POZNANIU Vol. 28 nr 1 Archiwum Technologii Maszyn i Automatyzacji 2008 PETER ŠUGÁR, JANA ŠUGÁROVÁ, LADISLAV MOROVIČ THE SHAPE ACCURACY ANALYSIS OF MACHINE PARTS PRODUCED BY METAL SPINNING Metal spinning is old method reshaping materials, derived from the ancient Egyptian art of potting on a wheel. Today, it is high-tech computerized manufacturing technology, which produces axisymmetric hollow parts with advantageous surface layer properties. Different spinning methods result in different qualitative parameters of spun parts. The paper presents the partial results of the experimental study, focused on the analysis of the shape accuracy of parts (samples) produced by multi-pass metal spinning. For the experimental study thin sheets with 1 mm thickness were used. The shape accuracy of the parts was analysed by the optical 3D measuring machine based on the principle of triangulation (3D coordinates for each camera pixel are calculated with high precision and a polygon mesh of the object s surface is generated). The 3D digitilizing with the mobile GOM ATOS I 350 system was used. For the visualization of shape deviations of real forming parts compared to nominal shape was realised using color plots. Key words: spinning, shape, accuracy 1. INTRODUCTION Forming is a manufacturing process, which plays the dominant role in the nowadays competitive industry. One of the relatively old, but now high-tech computerized forming technology is metal spinning, which produces axisymmetric hollow parts with advantageous surface layer properties (conventional spinning, shear spinning or tube spinning). The process can produce a wide variety of shapes, providing unlimited opportunities for part designers as well as for new applications. Spinning, compared with deep drawing, involves lower forming forces and less power. As a result, equipment is cost-effective engineered and process is very flexible. Other benefits are: increased level of automation, high mechanical Assoc. Prof. PhD. MSc. Department of Manufacturing Technology and Material Science, PhD. MSc. Technical University in Zvolen. PhD. MSc. Institute of Manufacturing Technologies, Slovak University of Technology in Bratislava.

2 138 P. Šugár, J. Šugárová, L. Morovič strength and hardness of part material, cost reduction by high material yield and favorable cycle time. These benefits apply to production of one-offs and prototypes as well as to small to medium runs. Nowadays the process is getting increasing importance in many fields of industrial applications, as for example in the manufacturing of process equipment such as centrifuges, funnels, tanks, medical and gastronomy equipments as well as drive technologies. It also has the possibility of producing parts that could not be deep drawn [3]. Benefits available for users of the spinning technology include: high flexibility, increase level of automation, very low risk of crack propagation, high mechanical strenght and hardness of spun parts, cost reduction through high material yield, variety of operations possible in one setup and favorable cycle time. Principle of the conventional metal spinning proces shows Fig. 1. Fig. 1. Principle of the metal spinning process: 1 mandrel, 2 follow block, 3 blank, 4 spinning tool, 5 tailstock centre Rys. 1. Zasada procesu wyoblania drykowania metali: 1 wzornik (model), 2 tarcza dociskowa, 3 półwyrób (blacha), 4 rolka do wyoblania, 5 kieł mocujący The experimental investigation of spinning parameters on the shape accuracy of part formed by conventional (multi-pass) spinning technology was realised at the Department of Manufacturing technology and Material Science, Faculty of Environmental and Manufacturing Technology, Technical University in Zvolen [1], [4], [5], [6]. The methodology and results of the spun parts shape accuracy measure by optical 3D measuring machine, are presented in the paper.

3 The shape accuracy analysis of machine parts produced by metal spinning SHAPE ACCURACY MEASUREMENT METHODOLOGY OF EXPERIMENTS A spherical shape of radius 107,5 mm blending via a 25 mm radius into a 168 mm diameter cylinder was used for these experiments (Fig. 2 and Table 1). Part was made from thin steel sheet STN (EN 30-69) and STN (EN 10088/1-3-95), thickness s = 1 mm. The manual spinning lathe was used. Variable parameters were spindle revolution (n = 315, 490 a 890 min 1 ) and number of passes of spinning tool (spinning without sizing p = 3 and with sizing p = 4). Mandrel s dimensions Rozmiary wzornika Table 1 D h 1 h 2 r 1 r ± 0, ,5 25 Fig. 2. Mandrel Rys. 2. Wzornik (model) The experimental samples were analysed from the shape accuracy point of view. 3D digitalization of the metal spinning part shape was realized by the system of optical scanning GOM ATOS I 350 (Advanced Topometric Sensor), consisting of two CCD cameras (they are located in the way that objective lens form an angle of 29 degrees) and projector (Fig. 3). The evaluation of computer models was realized by using of software GOM ATOS v , which allows dimensional and shape deviations analysis of scanned forms in relation to nominal data [2]. The basic aim of the experimental works was to consider the possibilities of the 3D optical scanning application to handle the shape accuracy analysis of the manufactured parts. The results of these works were processed in the visualization form of the part shape deviation and in the form of graphical surface deviation plots in a 3D presentation.

4 140 P. Šugár, J. Šugárová, L. Morovič Fig. 3. GOM ATOS I 350 optical measuring system Rys. 3. GOM ATOS I 350 optyczny system pomiarowy The Fig. 4 and Fig. 5 present the result of shape accuracy measurement of parts made from material STN (EN /1-3-95), thickness of sheet was 1 mm, spindle revolution n = 890 min 1, number of passes p = 3 (multi-pass spinning without sizing). The comparison of surface deviations to the reference data for spinning with and without sizing, for material STN (EN 30-69), are summarized in Table 2. Material: STN , EN 10088/ s = 1mm, n = 890 min -1, p = 3 Profil of spun part Nominal profil z x Fig. 4. Vizualization of real and nominal profile of spun part Rys. 4. Wizualizacja rzeczywistego i nominalnego profilu elementu wyprodukowanego metodą wyoblania

5 The shape accuracy analysis of machine parts produced by metal spinning 141 Material: STN , EN 10088/ s = 1mm, n = 890 min -1, p = 3 Real shape of spun part y z x Nominal shape of spun part Fig. 5. Vizualization of real and nominal 3D shape of spun part Rys. 5. Trójwymiarowa wizualizacja rzeczywistego i nominalnego kształtu elementu wyprodukowanego metodą wyoblania Table 2 Comparison of surface deviations for spinning with and without sizing (material STN (EN 30-69), n = 890 min -1 ) Porównywanie odchyłek kształtu elementu wyprodukowanego metodą wyoblania z następującym potem kalibrowaniem oraz bez kalibrowania Position of measure [mm] Number of passes p = 3 (spinning without sizing) Surface deviation [mm] Number of passes p = 4 (spinning with sizing) Point 1 ( 86,7; 6,4; 60,1) + 2,97 + 1,81 Point 2 ( 79,7; 2,9; 34,9) + 0,53 + 0,30 Point 3 ( 68,9; 4,9; 24,3) + 0,62 + 0,53 Point 4 ( 51,2; 6,4; 12,5) + 0,58 + 0,25 Point 5 ( 1,7; 11,7; 0,62) + 0,03 + 0,00 3. CONCLUSIONS Presented methodology and results are partial task of the research aimed at complex evaluation of qualitative parameters of parts manufactured by the metal spinning. The results of the shape accuracy analysis, obtained by 3D optical

6 142 P. Šugár, J. Šugárová, L. Morovič scanning method, show the factuality of the monitoring of selected process parameters impact (e.g. springback error) on the final shape accuracy. Graphical outputs show a high degree of shape deviation in the places, which are the furthest from the symmetry axis. In this case, the resulted state was caused by the material properties and by the fact, that the manufacturing of the parts was manual. By the using of a spinning roller operated by a hydraulic feeding mechanism, there is not expected such a wide difference between real and nominal shape of the manufactured part. REFERENCES [1] Gašparová, J., Šugárová, J., Kalincová, D. Study of microstructure and formed part wall thickness changes after metal spinning. In Development of Mechanical Engineering as a Tool for Enterprise Logistic Progress. Poznan : ZPW M-DRUK, 2006, s [2] GOM ATOS v. 5 User Manual. Braunschweig, [3] Palten H., Palten, D. Metal spinning From Ancient Art to High-Tech Industry. In Metal forming, 36, 2002, No. 9, pp [4] Šugár, P., Šugárová, J. Analýza silového pôsobenia tlačného nástroja pri operácii ohýbania materiálu za rotácie. In ITC Zlín : UTB Zlín, s [5] Šugárová, J. Technologická dedičnosť materiálu tenkostenných rotačných súčiastok. In Trendy lesníckej, drevárskej a environmentálnej techniky a jej aplikácii vo výrobnom procese. Zvolen : TU Zvolen, s [6] Šugárová, J., Šugár, P. Research study of strain distribution throughout the part after metal spinning operations. In DAAAM 2002, Vienna : VUT Vienna, p ACKNOWLEDGMENT The results presented in the paper are based on investigation of research project Expert system for technological parameters optimization of metal spinning process project No. 1/4097/07, funded by the Slovak Ministry of Education. Praca wpłynęła do Redakcji Recenzent: dr hab. inż. Jan Materniak ANALIZA DOKŁADNOŚCI KSZTAŁTU ELEMENTÓW PRODUKOWANYCH PRZEZ WYOBLANIE S t r e s z c z e n i e Wyoblanie drykowanie jest starą metodą kształtowania materiału, wywodzącą się z metody kół garncarskich, znanej już w starożytnym Egipcie. W chwili obecnej jest to najnowsze, zaawansowane technicznie rozwiązanie (high-tech) oparte na technice komputerowej technologii produkcji osiowosymetrycznych, wydrążonych (pustych w środku) elementów z cienkich blach

7 The shape accuracy analysis of machine parts produced by metal spinning 143 o określonych właściwościach warstw powierzchniowych. Jakość produkowanych elementów zależy przede wszystkim od przyjętego procesu wyoblania. W artykule zaprezentowano cząstkowe wyniki badań eksperymentalnych dotyczących analizy dokładności kształtu elementów (próbek) produkowanych zgodnie z konwencjonalnym wyoblaniem metali z wielokrotnym przejściem narzędzia. Do celów badań eksperymentalnych stosowano blachę o grubości 1 mm. Dokładność kształtowania była analizowana za pomocą trójwymiarowego optycznego systemu pomiarowego, pracującego na zasadzie triangulacji (każdemu zarejestrowanemu punktowi przyporządkowuje się z dużą dokładnością trójwymiarowe współrzędne, a następnie tworzona jest sieć poligonowa powierzchni). W celu digitalizacji zastosowano trójwymiarowy mobilny system optyczny GOM ATOS I 350. Do wizualizacji odchyłek kształtowania wykorzystano kolorowe pola. Słowa kluczowe: wyoblanie, kształt, dokładność