SIMULATION OF WORK OF THE VIRTUAL WELDING CELL WITH ROBOT

Transcription

1 International conference on Computer Aided Design and Manufacturing SIMULATION OF WORK OF THE VIRTUAL WELDING CELL WITH ROBOT Topčić, A.; Kudumović, Dž. & Butković S. CADAM'04. Abstract: One of the most important directions of future development of welding processes is applying of robots in this segment of producing technologies. It usage is enable with strong progress on information technologies area and that was allow development of numerous simulation models of welding processes. Those models are can be used for optimisation of utilization's degree of whole system according to predetermine criteria. Key words: Welding, modelling, simulation, optimisation, utilization degree, CIM 1. INTRODUCTION Usage of information technologies is enabled significant prosperity in all manufacturing areas and like that it has influence on welding area too. As a consequence of those activities on world market development of many softwares for application in welding are is happened. Those softwares can be sort in several groups: - Information technologies used in construction, manufacturing and research of welded constructions; - Information technologies used for deposition and generation of data for adequate welding process; - Research and development of welded constructions. Besides of that improvement of information technologies is widely open the door for further development to one of significant segment of welding processes robotisation of welding process. Current direction in development of robots usage in welding process is occur in continuous increase of complexity of those devices and that is consequence of demands for increase of flexibility and multi-functionality, for reprogramming capability during working-welding process. All those demands have for goal maximal usage of system in whole and its components too. Figure 2 Review of different configurations of robots There are many factors which had influence on installation of robots in all manufacturing systems and among them in welding process too. Some f those factors are: increase of productivity, improve of quality, increase of security, fitting in already automated production, esthetical reasons, etc. It is important to notice robotisation of welding process must necessarily be followed with development of whole manufacturing

2 system because robot alone will not improve business of that system essentially. So it is necessary to perform all sets of changes: arrangement and reorganisation of production, different kind of rationalizations and optimisations, education of workers and many other elements which will give meaning to robotization of welding process. Figure 1 View of working encirclement of welding module for RoboCell software Industrial robots can be define like programming controlled mechanical device which use sensors for guiding of one or several executive mechanisms according to forward determinate trajectory in working envelope with the aim to manipulate with physical objects. Therefore, industrial robots presented complex system built-up form mechanical parts, actuation sensors and controlling system. 2. MODELLING AND SIMULATION Designing of any manufacturing system is characterized with continuously development of hardware and software components, which require permanent engagement as far as wonted to accomplish maximal utilization of available potentials. Consequently, during design of certain production system or by selecting of some system devices there are often a lot of alternative solutions, which are technically possible. From those numerous possible solutions it is necessary to choose the best according to the technical and economic conditions settled by design task. Modeling and simulation processes can significantly accelerate that choice. In wilder meaning, modeling represents pay off (according to expenses) usage something (model) instead of something else (real system) with the aim to get certain cognitions. A result of modeling is model who present abstract of reality by meaning there are not include all real aspects. In other words model is description of real system with all those characteristics which are relevant from our point of view. The aim of model is to present on visible and often on formal manner that what is vital for understanding of some aspects of system structure and behavior. It is very

3 important for model usability to define on practical manner: analytical, numerical or experimental its behavior for limited set of their descriptive variables where are for certain mostly accidental input data are observed adequate outputs. Those last processes are called simulation. Figure 3 Dialogical frame for adjustment of welding parameters The word simulation in daily usage can characterize large number of different activities but in mechanical practice the word simulation presents process of building adequate model for some system or its part in real world and carry out of many experiments over it. With development of information technologies begin wider appliance of computers at execution of simulation experiments. 3. SELECTION OF WELDING PARAMETERS As it mention before during simulation process is presented welding of both side T joint using by MAG method and CO 2 as shielding gas. T part is made from two steel pieces with following dimensions [mm]. According to that is done choice of working welding parameters (figure 3, table 1). Figure 4. Review of welded joints which are possible to make in simulation module of RoboCell software 4. SIMULATION OF WORK OF WELDING CELL In this paper is presented simulation of virtual welding cell work consist from robot settled on working table, CO 2 welding machine, gravity feeder for semi products, rotation table for shelf of finished parts, optical sensor, welding T mold and computer for process control. For definition and running of simulation is used software RoboCell v.4.9 for robot SCORBOT-ER 4u and within them are integrated four segments:

4 - SCORBASE - a full-featured robotics control software package, which provides a user-friendly tool for robot programming and operation; - A Graphic Display module that provides 3D simulation of the robot and other devices in a virtual workcell (welding station, sensors, storages, conveyors); - CellSetup, which allows a user to create a new virtual 3D robotic workcell with all connections between components included in workcell or modify an existing workcell, - 3D Simulation Software for demonstration of RoboCell capabilities and for running of programming code written in Scorbase software. Figure 5 Trajectory of executorial apparatus of robots during simulation process and review of welding process itself Whit this software is possible to make simulation of welding process for T and butt welded joints and for them are proper molds available. Those molds have adherence function but enable manipulation with working parts by robot too (figure 4). Respecting to fact that is fully automated welded process work of welding devices is controlled by PLC controller which is configured in CellSetup completely. Parameters for welding process are adjusted in separate dialogical frame and consist: wire speed, shielding gas, welding wire diameter, gripper speed and electric welding parameters (figure 3). It is important to notice that in simulation case value of electrical welding parameters is referent number which is choose on the basis of several parameters like as: speed of robot gripper, wire speed and thickness of material.

5 RESULTS OF SIMULATION On the basis of probationary simulation and refitting of base simulation model according to the settled claims, determination of minimal time necessary for performance of assign task with maximal utilization degree of robot, is get optimal model of virtual welding cell for T joint (table 1). Table 1 Input parameters of welding process and utilization degree of working devices [%] [s] Robot in operation state 98, Robot in rest state 1,63 9 Welding process of T profile 16,82 93 Gripper in operational state 31, Piece in working position 16,64 92 Total time of piece in working position 66, Total time of working cycle 553 Total length of weld by one working piece [mm] 160 Diameter of welding wire [mm] 0,6 Shielding gas CO 2 Electric welding parameters 2 Wire speed [mm/s] 40 Gripper speed [mm/s] 7 Besides, on the basis of carry out simulation is construct the time diagram of whole process (figure 6), which enables insight in work of all systems parts and on the end for each welded joint quality report is got (figure 7). Piece 1 Piece 2 Piece 3 Piece 4 Welding Robots work Gripper Time [s] Figure 6 Time diagram of observed process get according to simulation of welding working cycle for T profile CONCLUSION Development of information technologies and more and more capabilities that they allowing are widely open the door to usage of these technologies in projecting, development, modelling and simulation of robotic welding systems. One on those

6 informatics solutions is simulation software RoboCell with its module for welding processes presented in this paper. As it is possible to see from presented results of simulation process this software enabling: 3D interactive simulation of robotic welding and effective control with appropriate routine code (software SCORBASE) by adequate number of sensors (digital input-output). Additionally, following of time parameters for all working segments of welding cell is allowed. Those characteristics of simulation software RoboCell enabling modelling, simulation and selection of optimal working parameters for all elements of welding cell in virtual environment as well its optimisation according to wanted criteria of optimisation. Figure 7 Quality report for finished welding process and time schedule for executed operations References: [1] Kudumović Dž.: "Zavarivanje i termička obrada", Tuzla, god. [2] Banks Jerry, Gibson R. Randall: " Getting started in Simulation Modeling ", IIE Solutions, Novembar. [3] Gumaer R., (1996), Beyond ERP and MRP II, Solutions, No. 9, [4] Zrnić Đ., Savić D.: " Simulacija procesa unutrašnjeg transporta ", Mašinski fakultet Beograd, [5] Kelton W. David, Sadowski P.Randall, Sadowski A. Deborah: " Simulation with Arena ", WCB McGraw-Hill, New York, NY., [6] Radenković B., Stanojević M., Marković A.: " Računarska simulacija ", Fakultet organizacionih nauka, Beograd., [7] User manual, RoboCell version 4.9 for SCORBOT-4u Alan Topčić, MSc (mechanical engineer), Senior Assistant, University of Tuzla, Faculty of Mechanical Engineering Tuzla, Univerzitetska 4, Tuzla, Bosnia and Herzegovina, Phone\Fax: (0) , alan.topcic@untz.ba, alantopcic@hotmail.com Džafer Kudumović, PhD (mechanical engineer), Associate Professor, Faculty of Mechanical Engineering Tuzla, Univerzitetska 4, Tuzla, Bosnia and Herzegovina, Phone\Fax: (0) Samir Butković, mechanical graduate engineer, Assistant, University of Tuzla, Faculty of Mechanical Engineering Tuzla, Univerzitetska 4, Tuzla, Bosnia and Herzegovina, Phone\Fax: (0) , samir.butkovic@untz.ba