COMPUTER SIMULATIONS OF THE HOLES STRAIN BEHAVIOR IN BODIES DURING MACHINING

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1 A R C H I V E S O F M E C H A N I C A L T E C H N O L O G Y A N D A U T O M A T I O N Vol. 34 no RYSZARD WÓJCIK, NORBERT K PCZAK COMPUTER SIMULATIONS OF THE HOLES STRAIN BEHAVIOR IN BODIES DURING MACHINING In the construction and technology studies there is a need to simulate the behavior of body components during machining. For this purpose, theoretical studies have been conducted. They show the influence of determining and mounting the body of A reducer on its deformation. The ability to simulate and visualize the deformation of holes obtained by the machining allows to limit the number of construction errors at the design stage and develop adequate tooling for the machining process. Analyses and simulations were performed for the body of a bevel gear. Key words: computer simulations, aided design, static analysis, elements of the bodies 1. INTRODUCTION Modern engineering programs offer simulation modules which allow to predict the behavior of the physical model under, for example, static or dynamic loads [1, 3, 5]. Their application is intended to limit the risk of error at the design stage. Consequently it creates an opportunity to choose the appropriate wall thickness of the designed element, dimensional-shape tolerances, etc. Simulation process also presents a possibility of stiffening places susceptible to various types of forces, which occur during the determining and mounting, as well as the forces induced by treatment and operating. Furthermore, there is a possibility to elaborate an instrumentation which allows to maintain the appropriate tolerances of the holes. They determine the correct work of the entire gear and thus the operational strength [2, 4, 7, 8, 11]. For the simulation and experimental process, a bevel gear reducer s body was selected. The aim of the analysis was to determine the state of the holes, their shape and to validate the selection of tolerances. Dr hab. in. Mgr in. Institute of Machine Tools and Production Engineering, Lodz University of Technology.

42 R. Wójcik, N. K pczak 2. RANGE OF THE ANALYSIS AND SIMULATION For the simulation, a 10.01 MB body of MOBEX company was used.

2 42 R. Wójcik, N. K pczak 2. RANGE OF THE ANALYSIS AND SIMULATION For the simulation, a MB body of MOBEX company was used. The theoretical maximum size of the cutting forces occurring during processing, but such which do not cause displacements (deformations) exceeding the minimum tolerance of machined holes were studied. For the MB 10.0, with a small body of dimensions of mm, height of 255 mm. The dimension of the holes equalled to 190 mm and 110 mm. For the smaller hole, the tolerance was established at mm. Iron cast as a body material used in the simulations had the following mechanical properties: Density g/cm 3, Tensile strength 200 MPa, Poisson s ratio 0.3, Young s modulus 90 GPa. Different variants of fixings and mountings were considered. Finally, for the analysis, three different constructions were selected: 1. Using bolts and dowel pins, 2. In a certain clamping device, 3. With an expanding mandrel. During the analysis, the following machining operations were simulated: planning and turning of the large hole, as well as planning and turning of the small hole. For the mounting with an expanding mandrel, only planning and turning the smaller hole were simulated. Figure 1 presents the body of the bevel gear which was used for the simulations. Figure 1. View on the MB body

3 Computer simulations of the holes strain behavior in bodies during machining 43 BOLTS AND DOWELS CLAMPING DEVICE EXPANDING MANDREL Figure 2. Methods of determinings and mountings of the body a) b) c) d) Figure 3. Operations of the holes: a) facing of the large hole, b) boring of the large hole, c) facing of the small hole, d) boring of the small hole Figure 2 shows the method of mounting during processing it is an information for the constructor, determining maintaining the appropriate parameters of the hole. In addition, methods of determining and mounting without an adequate

4 44 R. Wójcik, N. K pczak stiffness of bodies, they may determine susceptibility to the forces encountered during the cutting process. They could introduce vibrations affecting the parameters of the cylindrical bearings surfaces. Fragments used to determine and mount the body are marked blue in the pictures below. The following operations were simulated: facing of the large hole (Figure 3a), boring of the large hole (Figure 3b), facing of the small hole (Figure 3c) and boring of the small hole (Figure 3d). In all the figures, direction of force acting on the surface of the workpiece in the cutting process was marked. 3. RESULTS OF THE SIMULATIONS The results of the simulations are summarized in Table 1. Figures 4 and 5 present views of the deformed body, which were obtained after applying cutting forces during facing larger hole for the first method of mounting (using screws and dowels), and second method (using clamping device). The result of the simulations Table 1 Maximum cutting force Bolts and dowels Clamping device Expanding mandrel Facing a large hole 4505 N N Boring a large hole 4538 N N Facing a small hole 7726 N N N Boring a small hole 7126 N N N Figure 4. View of the deformed body during facing of the larger hole for the first method of mounting

5 Computer simulations of the holes strain behavior in bodies during machining 45 Figure 5. View of the deformed body during facing of the larger hole for the second method of mounting Figures 6, 7 and 8 present views of the deformed body obtained after applying cutting forces during facing of the small hole for all the methods of mounting. Figure 6. View of the deformed body during facing of the small hole for the first method of mounting

6 46 R. Wójcik, N. K pczak Figure 7. View of the deformed body during facing of the small hole for the second method of mounting Figure 8. View of the deformed body during facing of the small hole for the third method of mounting For a more detailed view into the results of the deformation, depending on the impact of the cutting forces and the method of mounting, Figure 9 summarizes the various images in a 2D format.

Computer simulations of the holes strain behavior in bodies during machining 47 a) b) c) d) Figure 9.

b) deformation for the second method of mounting during facing of the large hole and the cutting force equal to F = 37360 N, c) deformation for the first method of mounting during facing of the

CONCLUSIONS Computer simulations were performed to determine the maximum cutting force at a different method of mounting, which is helpful for the technologist in the selection of cutting

7 Computer simulations of the holes strain behavior in bodies during machining 47 a) b) c) d) Figure 9. Selection of the deformation depending on the size of the cutting forces: a) deformation for the first method of mounting during facing of the large hole and the cutting force equal to F = = 4505 N, b) deformation for the second method of mounting during facing of the large hole and the cutting force equal to F = N, c) deformation for the first method of mounting during facing of the small hole and the cutting force equal to F = 7726 N, d) deformation for the second method of mounting during facing of the small hole and the cutting force equal to F = N 4. CONCLUSIONS Computer simulations were performed to determine the maximum cutting force at a different method of mounting, which is helpful for the technologist in the selection of cutting parameters, as well as the development of production jigs for bodies having holes exceeding 100 mm. As is apparent from the table and drawings, the lowest cutting forces occur in first method of mounting, using screws and dowels (during processing of the large and the small hole). For the second method of mounting in a clamping

8 48 R. Wójcik, N. K pczak device the value of the cutting force increases from three to eight times, depending on the type of treatment and the dimension of the machined hole. However, for the smaller hole only, the most preferred option for mounting is an expanding mandrel. In this case, cutting forces increase from six to approximately ten times comparing to the first method of mounting. Theoretically, the cutting forces obtained in the simulations were very high and it could be said that in standard cutting conditions, such forces will never be found. However, if the boundary condition would be a constant cutting force for different methods of mounting, and the value of the deformation parameter would be searched for, the greatest deformation would occur for the first method of mounting, and the smallest for the third method. The order of conducted operations is a very important element of the simulation and experimental work, as well as for construction work of adequate instrumentations, which allow to obtain the proposed tolerances of individual holes. This section determines the proper operation of the gear its life. REREFERENCES [1] Korcz A., Komputerowe wspomaganie procesów wytwarzania CAM, Scientific Bulletin of Che m, Section of Mathematics and Computer Science, 2009, no. 1, p [2] McMahon Ch., Browne J., CAD/CAM principles, practice & management, Addison Wesley 1998 [3] Paj k E., Wieczorowski K., Podstawy optymalizacji operacji technologicznych w przyk adach, Warszawa Pozna, PWN [4] Piko A., AutoCAD 2000 PL, Gliwice, Helion [5] Tarnowski W., Kiczkowiak T., Komputerowe wspomaganie projektowania, Koszalin, Wydawnictwo Wy szej Szko y In ynierskiej [6] [7] [8] [9] [10] [11] Younis W., Up and running with Autodesk Inventor Simulation A step-by-step guide to engineering design solutions, second edition, Elsevier KOMPUTEROWE SYMULCJE ODKSZTA CE OTWORÓW KORPUSÓW PODCZAS OBRÓBKI SKRAWANIEM S t r e s z c z e n i e W opracowaniach konstrukcyjno-technologicznych istnieje potrzeba przeprowadzenia symulacji zachowania elementów korpusowych podczas obróbki skrawaniem. W tym celu przebadano wp yw sposobu ustalenia i zamocowania korpusu reduktora na jego odkszta calno. Mo liwo

9 Computer simulations of the holes strain behavior in bodies during machining 49 symulacji, a nast pnie wizualizacji odkszta ce otworów otrzymanych w wyniku obróbki skrawaniem pozwala ograniczy ilo b dów konstrukcyjnych ju na etapie projektowania, a tak e opracowa odpowiednie oprzyrz dowanie do obróbki skrawaniem. Analizom i symulacjom poddano korpus przek adni k towej. S owa kluczowe: symulacje komputerowe, wspomaganie projektowania, analiza statyczna, elementy korpusowe

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