Computer Aided Bus Skeleton Design (BUS-CAD) - IJENS

International Journal of Engineering & Technology IJET-IJENS Vol:12 No:04

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Computer Aided Bus Skeleton Design (BUS-CAD) H. M. A. Hussein and Alexander Harrich Abstract— The designing and manufacturing of a new bus is a process which need of a large number of technical labors and a great consumption time, starting from designing operation until full production process. Bus Industry in the Arab region realized some success and is equivalent to their counterparts in Europe and America. This makes the interest in reducing the time and efforts spent in the design, planning and production processes in the bus industry is an added value. The bus steel structure (skeleton) building process is the starting base for all the following manufacturing processes. Planning Department -based on it – start writing the operating pages and determine the required raw materials for the bus manufacture. The logistic department starts to provide the necessary raw materials for the bus construction. Tool department starts to design and manufacture of production facilities, and main fixtures (drilling and welding) for constructing the bus skeleton. The administration department collects all the information’s to estimate the bus cost and expect the profit from the implementation of this product. The virtual world created by the computer in nowadays our life puts a strong chance to simulate many of the manufacturing processes before they occur, and this was not available before. Bus skeleton design, planning and manufacturing operation represent a good example can be implemented entirely by using computer simulations. The present paper discuss the basic lines for construction a program to reduce the design, planning and manufacturing processes of the bus structure. Objective of this proposed work is designing a parametric program for the bus skeleton design (all types) with a possibility in parametric design modification in the bus skeleton – Automatic creation of technical documents – Bus welding assembly fixture construction - determine the initial cost estimation of the bus. Index Term— Parametric design, Bus skeleton, CAD, Concurrent engineering, Process Planning

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INTRODUCTION

Bus and mini-bus in any country is a kind of industry which is connected directly to the prosperity and the stability of this state. It starts after two years of completion of the security and sociality stability of the welfare state, but stopped immediately in case of any defect in this stability. Begins, when the industrial company owner demand for buses to transport his H. M. A. Hussein, Author is with the Advanced Manufacturing Institute, King Saud University, Riyadh, KSA., phone: 00966568775127 hhussein@ ksu.edu.sa Alexander Heririch, Author is with Institute of Automotive Engineering, Graz University of Technology, Inffeldgasse 11/1, A-8010 Graz, Austria [email protected]

workers from and to his factories. When, Tourist company owner demand for buses for tourist’s trip transport around the country. When requested by state agencies for the buses, minibuses inside and outside of cities to transport citizens here and there. The design of the internal bus skeleton structure is the basis of typical bus development of the bus industry. It contains of framework of tubes with different cross sections, which arranged in specified shapes based on the design philosophy. This arrangement is used to be safe for occupants and to sustain the extreme conditions can be matched on the road. For this reason, several tests are made on the bus structure to measure the durability. The most important is the impact and the Roll-Over Tests. Time expected to complete the bus structure design is more than 3 months and then followed by a group of related industrial processes, such as; (1) covering the bus body structure by panels, ―Sheeting‖. (2) Manufacture the bus front and rear from fibreglass. (3) Process planning for each bus components. (4) Cost Estimation for the complete bus skeleton, which is a decision making support for the bus company owner. (5) provide all the production facilities requirements to complete the bus body. (6) Design and manufacturing aspects of the assembly welding fixtures for the six sub-assembly fixtures and finally the main Merry Jig. In some industrial facilities, there is interest in the FEA simulation programs to predict the durability of the structure and the extent of its ability to withstand the shocks and the coup. As well as simulate the thermal analysis of the body structural related to the welding fixture to determine which places may be exposed to the greatest welding deformation operations. Then, consolidate and treatment of these regions by more clamps. The means of installation that will maintain the structure dimensions intact to ensure the safety of the next related operations. Unfortunately, in many bus factories in the Arab region neglects of the body skeleton FEA simulation and depend only the on the past designer experience for added more bus structure tubes, which increases the weight and cost of the bus. The bus or minibus body skeleton design represent the bottleneck stage within the industrial facility, which once completed successfully, the other company sectors starts to work either parallel or sequential. Thus, an acceleration of this process leads to a reduction of development time, which can be consequently transferred into money. In this way the industrial partner enhances its efficiency."

1213604-8585-IJET-IJENS © August 2012 IJENS

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International Journal of Engineering & Technology IJET-IJENS Vol:12 No:04 II. LITERATURE REVIEW Process to accelerate of the bus structure completion design is an urgent need within the industrial factories working in the bus industry. The giant companies working in this area are expecting to have their own programs for the bus structure design. The information’s about this programs not reach us except very little of these experiments are either considered secrets of the industry or because they are completed within companies so may not be publishing for research purposes in this case. From past experiences that have reached us is the experience of El-Nasr for the cars manufacturer of in Egypt,‖NASCO‖ which carried out through The ―Automated Integrated System‖ (1 and 2), through which the completion of the program to build the structure of bus public transport (within cities) using the AutoCAD program and AutoLISP language linked to MS-Excel program. The coordinates were extracted from a real bus skeleton from the former company products called N966. It’s collected point by point from the blue printed pages. The coordinate’s value then stored in Excel file. An AutoLISP program constructed to build each layer of the pipe through the pipe skeleton. The AutoCAD program also has been linked to DCL, Dialogic Dialogue Box. Hundreds of equations, computational relations and engineering rules which related on the bus skeleton design have been used. All those data are extracted from the company experts in bus design. This expert rules data are stored into excel file to construct the Knowledge Based Design. After full success of Bus Skeleton design model, a Finite Element ―COSMOS‖ program is used to analyze the stresses on the structure and to predict the extent of safety design structure. This work took nearly 6 years starting in 1990. American University in Cairo ―AUC‖ and Azhar University are participated in the model preparing project. The Mechanical Design Department in Cairo University was participating in the stage of skeleton stress analysis. Researcher Majid Rasmy of Cairo University, progress of his Master degree 2003 in reach an optimal design of the movable tubes structure. This study was implemented in cooperation with Ghabbour bus industry in Egypt. In this study, a movable tube structure is simulated by computer and the stress analysis is done using ―COSMOS‖ finite element program. Researcher U.C. Tapici from Istanbul Technical University, Turkey, 2006 (3 and 4) study the impact of appropriate clamp selection in the process of tube welding used for bus structure to reduce the dimensions distortions resulting from the arising thermal stresses based on the welding operation. A Programmable arc welding robot is used in this operation. Researchers Lan, Chen, Lin (5) in Automotive Engineering School in both of Jilin University in China and Birmingham University in 2004 have a weight-loss study of the bus structure to the permissible limit with using a stress analysis program ―ANSYS‖. The study applied on 2 models, one of those models before decreasing the weight, and the other after decreasing the weight on the bus side wall. A comparison is done between the 2 models to get ride off the unnecessary

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tubes which have not a significant impact in the durability of the structure. The Researcher Vikas Yadav (6) in 2006 has studied the impact action on the lower part of the bus by using the stress analysis software, and similarly, the researcher Ganesh R. Panneer (7) from the University of West Virginia in 1998 to study the impact of trauma on the schools bus side. The researcher PankajChandna et al, (8), as well as Rahul Mahajan et al (9) have studied stress analysis on the bus structure using Hypermesh and NASTRAN programs, the bus structure model is build using the CATIA program. In the current paper, a new parametric bus skeleton model will build on both AutoCAD and CATIA program using tailor made macros. The both macros controlled using visual basic program, which connected with MS-Excel to extract the coordinates for constructing the bus skeleton model. The program is build to construct all the busses family groups, such as mini_buses, city_buses, inter_city_buses, high deck, super_high_deck. For each family of busses, the proposed program will help in the Body skeleton model construction module, bus skeleton modifier module, components process planning module, cost estimations module, bus body sheeting module, and Fixture design module. In the first stage, the research work will focus on extracting the co-ordinate data from the mini-bus crouser, which is one of the Ghabbour-Egypt company products, as shown in Figure 1, to build the program main base. The co-ordinate data will extract from a ready –made AutoCAD file for body drawing. The extracting operation will need another tailor made AutoLISP and VBA codes for this very long operation, but in the same time it still need for extensive setup work and dataentry work. The first stage work for constructing the bus body model, will not focus on the design quality, but will focus only on the time duration measurement in constructing the model.

Fig.1. Mini-bus crouser

III. RESEARCH OBJECTIVE The main goal of this project is to introduce integrated software in bus and mini-bus industry called BUSCAD. BusCAD Program is to solve all the problems related to the all types of buses in the bus industry. The types of busses could be classified into MiniBus, CityBus, Intercity Bus, High Dick, Super high Deck, School bus, ... etc as shown in Figure 2, which shows the proposed program main menu. Each button allows the user to access the selected type of buses. These


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International Journal of Engineering & Technology IJET-IJENS Vol:12 No:04 problems such as designing and building the bus skeleton structure with the ability to re-design or modification in the structure if necessary. The covering or sheeting of the desired bus structure location. Designing and drafting of the interior accessories bus design such as chairs, dashboard, the upper shelves.... etc... Producing the full detailed process sheet for every part of the bus components. Welding fixture design for each assembly and sub-assembly of the bus skeleton. The flexibility of selecting between different techniques in bus welding fixtures designs, which suitable to the factory planning and capabilities. Identifying initial cost estimation for the bus projected. For the implementation of such a design, which is determined by the expected profit and speed of decision-making for the implementation of the product or not and is determined by the price of the integral relationship between the programs of CATIA and MS-Access avoiding thus to deal with external programs such as the Oracle, Sap or Paan. Finally, stresses analysis of through advanced technologies provided through the fifth edition of the CATIA program compared with the previous versions. Stress analysis in the bus project includes two important issues here. The first topic is to dynamic analyze the stresses on the bus skeleton of the bus to check the bus structure durability and its ability to protect the passengers lives inside in case of collisions with moving or fixed objects, as well as in cases of Bus Roll-Over Test. The second theme is to analyze the thermal stresses on the body skeleton structural bus resulting from the welding operations. This analysis is important. To determine the most important points on the bus skeleton structure that should be clamped to avoid distortions. The analysis will provide us with the necessary force required at which point to overcome the tube distortion based on thermal stresses.

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and without this model we cannot move to any of the following related steps. Whenever, the rapid construction of the computer 3D model, the rapid speed related steps could be done, the rapid speedily access to the optimum design, and then the fastest decision making could be done. The target of this project proposal in the first stage is to construct the bus skeleton 3D model via CATIA or AutoCAD programs. The first program stage focuses on achieving this goal in a very short duration, without taking the optimum design into consideration. The optimum design will be care in the following program stages. III. THE USED PROGRAMS Program - at the first stage - is an interactive language between CATIA and AutoCAD programming, and Excel Programming. The coordinated stored in Excel file will arranged in the suitable manner that can be read in the CATIA or AutoCAD programs. The Excel coordinate sheet will be controlled through another set of Excel sheets, which work as a translator from Excel sheet to other to simplify the arrangement problem. This technique for this reason becomes easier for the programmer to read, follow and control the data. All the cells in each sheet are connected together with a sum of relations and equations to simplify the full excel file control. In case of the CATIA programming, the CATscript file is divided into a number of divisions. The first part is responsible in connecting the CATIA program with the MS-Excel file. The second part is responsible in receiving data from the Excel coordinate sheet, and store them into variables inside the CATIA macro, ―The stored coordinate variables in the case of minibus is more than 3000 items‖. The third part, receiving the stored coordinates items from the second part of the program, and then converted into points. The fourth part of the program connecting between points to construct lines and Splines, the fifth program part prints the lines and splines on the CATIA screen. The dealing with AutoCAD program is nearly the same steps with little bit minor modifications. The whole programs items are controlled using the visual basic program. PROGRAM OPERATION PROCEDURE. Once running the program, the dialogue box in Figure 17 appears to select the vehicle type that will be working on it, as example for the first stage "MiniBus". The dialogue Figure 18 shows the selection of the operation type, as example "Bus Skeleton Design".

Fig. 2. The program main menu

Fig. 3. The proposed operations on the bus skeleton.

Figure 3 illustrates the most important operations to be performed on the bus skeleton structure. In each of those applications we need first to construct a computer 3D model, 1213604-8585-IJET-IJENS © August 2012 IJENS

Fig.17. Bus side curve control screen

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Fig.18. The Bus Roof Curve ontrol Screen

To design the skeleton structure for a new minibus, the side curve must be firstly select, and for this purpose the dialogue box in figure 17 is designed to control the bus side curve. The curve is controlled by adjusting its coordinates. Whenever the curve contains more points, whenever the smooth curve can we obtain. Figure 17 shows, the curve coordinates of the mini-bus Cruiser, which by changing these coordinates especially in ―Y‖ and ―Z‖ directions and kind, the side of the screen shows the shape of the curve representative of the new curve and the coordinates directly relate to the page program Excel cells for control, which in turn relate to the program page of the Excel program which integrated with CATIA, and contains the software on 25 points for the curve representative side in order to give you the maximum degree of flexibility in the extraction by a new curve. The next step for the mini-bus structure design is the roof curve design, and for this purpose, a dialogue box is designed as shown in Figure 18, as the same technique used in the side curve. Through the powers of 26 control points, any roof curve can be design easily, as possible to the roof to reach the optimal design and is worth mentioning that must be adhered to the limits of certain in this drawing curves whether abroad or to the inside - and that these limits are subject to either previous experience in the BB design or the limitations posed by each country in its own designs, such as the maximum width and height of the top of the vehicle so as not to conflict with the heights of bridges or display methods provided for in the design codes used in this state. CATIA and AutoCAD aided Bus Industry The next step is to run the CATIA or AutoCAD program to start the macro directly from the Desktop or to run it through the pull-down menus from within a program CATIA or AutoCAD Tools. The program draws the proposed bus or minibus components design through the graphical media even in CATIA or AutoCAD. The components for the minibus are about the 350 part, each representing a tube or section in the bus structure. The software synthesis of Relations between CATIA or AutoCAD as a graphical media and the MS-Excel program automatically and then, extracts these values to put them in a Parameters, and then re-called again for the printing this data on the graphical media program screen. Figure 19 shows part of the CATIA product tree.

Fig. 19. The CATIA Product Tree

Figure 20 shows the full mini bus skeleton mini bus for the crouser product. Using a tailor made AutoLISP code, all the model tube converted into wire frame (lines and splines) in the middle centre of the buss tubes as in figure 21. In the second level, another AutoLISP code runs to search the entire drawing data base and select all the lines and splines coordinates and extract their first and end points co-ordinates and store into excel file as a database. These two codes save a lot of time of the data entry work. Figure 22 shows the re-build of the buss wire frame into CATIA graphical environment.

Fig. 20. The Bus Skeleton model on the AutoCAD Environment

Fig. 21. The Bus skeleton wire Frame on the AutoCAD Environment


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Fig. 22. The Bus skeleton wire Frame on the CATIA Environment

CONCLUSIONS Computer aided bus skeleton design, is a powerful tool to support bus building companies, The work in this project must be done in steps, The first step which in this paper focus in how to rapid build the bus skeleton.

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