on the implementation of a robotic welding process using 3d
TRANSCRIPT
On the Implementation of a Robotic Welding Process
Using 3D Simulation Environment
Ignacio Davila-Rıos∗
Luıs M. Torres-Trevino†
I. Lopez-Juarez‡
April 18, 2008
AbstractThis paper presents the simulation of an au-
tomated welding process based on an industrialRobot KUKA KR16. The main objective is tointegrate all devices needed to perform the sim-ulation using Delmia V5 Robotics and to avoidany possible mistake when implementing of thereal workcell; for example, with physical dimen-sions, possible collisions, path planning, etc. Thefeasibility in the implementation can be deter-mined trough 3D simulation of a manufacturingworkcell to perform tasks type MIG welding.
1 Introduction
Nowadays we can find many production pro-cess, in which the manufacturer makes an ef-fort to obtain a better an stronger process toincrease the quality; the welding process is notthe exception, there are many welding processesfrom fusion welding (gas) to laser welding.[8]The application of welding can be use in twoways: 1) Manual or conventional welding, whichis made by people with tools like a welding gun;and 2)Automated welding that is composed byrobots called “Welding Robots”.
∗Doctoral Student programme PICyT with terminaloption Eng. Industrial and Manufacturing.
†Research Professor at the Centre for ResearchCOMIMSA.
‡Robotics and Advanced Manufacturing ResearchGroup CINVESTAV-Saltillo.
The use of Robots with welding tasks, are notsimple as they have to suffer different changesthrough time. That is one of the reasons whypeople produce many parts where welding is veryuseful for assembly.[7]
Fast development software and graphic sys-tems have been possible to create virtual de-sign, at the same time benefits and realism haveevolved. The CAD platform such as CATIA andDelmia tools allow to design and to simulated3D process, introducing models robots. The ad-vantage to use this tools are: it allows to ver-ify the conformity before their implementation,verify use of norm applied, to practice alterna-tives in order to search for the better option andto explode results, to make economic change ina flexible way, to make sure in the system de-sign to avoid unexpected cost and to save in thedesign.[2]
The designers in the field of engineering designand automation are able to easily understandthe state of the art technologies of robotic work-cell simulation, and integrate these technolo-gies with their knowledge and experience aboutCAD, robotics, and robotic workcell design.[3]The use of advanced technology simulation suchas related with virtual reality (VR), open newalternatives and give a huge field to develop newapplications.[6]
The simulation is used for the identification ofdesign problems in an early phase, for an itera-tive focus of resolution of problems, integrationof the designers work and simulation engineers,
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from the design until the finished product.[4]
The users of dynamic simulations 3D consti-tute an advanced methodology for the analysisof the risks associated to the installation of thesystems and solutions to robotics. The advan-tages of these techniques become evident whenfacilitating, among other things, to analyze andto determine from a precise and previous wayto the installation, some of the risks more com-mon of the industrial robots, like they have therisks for impacts (collisions) of the robot’s partin the tasks during assembly, ergonomics of theposition, demarcation of the environment of therobot’s work and the reach regions for impact,etc.[3]
In the following sections it is proposed the in-tegration through a simulation (Delmia Robotics3D) of a robotics manufacturing workcell, whichhas the task to carry out welding processes usinga KUKA KR16 industrial robot.
Some cases of automated simulations are inthe automotive industries, due that they havegreat quantity of automated welding process,such as DaimlerChrysler for which companiessuch as Kuka and Delmia have worked together.Experts of the two companies created a solutionof second generation with Robots of SimulationRealists (RRS), a graphic environment providedfor Delmia, in which the information of Kukais connected in real time on their own Mani-pulator’s movements Virtual Robotic (VCR),to reach a higher level of sensibility simula-tion and to demonstrate the real robot inte-gration. The aerospace company, Airbus hasalso requested service from KUKA and DelmiaRobotics V5, obtaining very good results in theirapplications.[10]
The development of this simulation follows aninitiative from our corporation to start a newresearch area looking to solve the inherent prob-lems involved in Robot welding.
2 Enviroment in 3D Simulator
The simulator in which this work is develo-ped is conformed by the software Delmia V5Robotics 3D together with the design softwareSolid Works. This tool (Robotics 3D) allows tobe carried out simulations of automated manu-facturing processes, specifically with robots, thissoftware has a great variety of robots models, aswell as of different brands. Delmia V5 Roboticsoffers an easy and flexible use of solutions forthe definition of tools and simulation cell. Itprovides all the necessary tools to define andto analyze the behaviors and the necessary re-sources to apply the process plan. Also it helpsto describe exactly how parts are loaded and un-loaded, fixtures, and welding processes. It can becarried out easy and with accuracy the validationand analysis of the production processes throughsimulations based physically on the resources.[9]
The Robotics V5 environment is composed fora great variety of tools called “toolbars”, whichare presented as icons around the main screen,inside it, they are two very important functions,the compass and the tree PPR (Product, processand resource). The compass is used to changeposition and to move the elements to use, andthe tree PPR is used to show the products, re-sources and how it is carrying out the processinside the simulator, as well as to take a relationamong them because they work together. Fig-ure 1 shows the main screen.
PPR TreeCompass
Toolbars
PPR TreeCompass
Toolbars
Figure 1: Main screen of the Robotics V5
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For the design of specific components the SolidWorks was used, due to the compatibility thatit has with the Robotics V5 when exporting thepieces and also it allows to work in 3D. This soft-ware was used to consider all the components toscale. Once all the designs of the workcell areready, then the following step is to integrate ev-erything in the simulator, to carry out the weld-ing tasks with the Robot KR16.
3 Virtual Development of aRobotic Workcell
For the workcell simulation, some of the com-ponents that are not designed have to be de-signed separately. For instance, a welding ta-ble, a conveyor, and the KRC2 robot controller.These components are designed in the softwareSolid Works and exported to Robotics V5.
3.1 Design in solid works
Once one has the real measures of the com-ponents, they are designed in the software SolidWorks, or in any other design software in 3D thatallows exports to the Robotics, as it is the casewith CATIA, NX (before Unigraphics) amongothers. To design in Solid Works. First the mea-sures of the real components are taken, the soft-ware opens in the “piece” function, this func-tion allows to create a piece, which has to bedrawn first on a plane inside a function called“croquis ”, these designs have to be carried outon a plane, which can be of raised type, plants orlateral view; once obtained the drawings of thecomponent the following step is to carry out op-erations. Among the most usual is “out extru-sion” that is to transform the two dimensionaldrawing to a piece in 3D. See Figure 2.
Once the components are designed, the nextstep is to export them to the software Robotics3D, so that they can be used in the robotics weld-ing process simulation.
Figure 2: Solid Works environment
3.2 Layout Construction in theRobotics V5
Industrial robot generally work with others de-vices such as conveyors, production machines,holding fixtures and tools. The robot and theequipment form a workcell. Also you can use theterm work station, but this term is generally usedto identify 1) One workcell with only one robotor 2) a work position along of a line productionof some station of robots work. Two problems inapplications of robots engineering are, the phys-ical design of the work cell and the design ofthe control system that it will coordinate theactivities among the diverse components of theworkcell.[5] For the construction of the layout inthe simulation software Robotics V5, is it neces-sary to open a document in “process” mode, thisto be able to work in the simulation environmentand it can open the “PPR tree”, it is necessary toprogram in the beginning mode and simulationresource the option of “Device task definition”.To create the layout in the beginning screen it isnecessary, to insert the products and resources;the insert of the products and resources will de-pend in the way it wants them to use in theirprocess.[9] Through the “toolbars” in the optionof insert, it is inserted as product a Body SideAssembly Part and such resources Robot KukaKR16, the table of welding, the torch, the work-cell and a riser (platform for the Robot), once all
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the components are on the screen PPR, the fol-lowing step is to carry out a “Snap and attach”that serves to unite the riser with the robot. Formounted of the torch in the robot the toolbar“Robot management” is used; when oppressingthe icon Set tool immediately appear a dialoguebox called “Robot Dress up”, here only it is nec-essary to select inside the tree PPR the Robotand the torch so that it is attached in the Robot.See Figure 3
Torch
Mounted
Torch
Figure 3: Mounted torch to the Robot KR16
The following step is to accommodate theother resources and the product such they arewanted to place physically, this operation can becarried out by the compass which has a func-tion called “Snap automatically to Select Ob-ject”. See Figure 4.
Controller
Cylinder of gas
Workcell
Conveyor
Robot KR16
Body side Outer onthe work table
Weld
ing
machin
e
Figure 4: Layout of the complete workcell
4 Simulation process
Usually, the programming of robots is carriedout using a computer system for the developmentof programs. In the most simple case an editor ofprograms and a translator are presented. Never-theless in many systems, purification proceduresand treatment programs of execution errors areincluded. Then, if the program originates thatthe movement among a point and other, one ar-ticulation reaches a superior value to its limit,the robot generates an error that could be readby the operator. This simulator, carries outsomething similar, shows when it has a crashor collision, or when it exceeds those articula-tion limits. It also provides the correspondinglanguage of the robot programming.[1]
For the simulation process it is necessary tocreate the tags and those Robot task associatedto them, the tags are those points for which therobot will carry out the welding operations. In-side the bar, Tag toolbar selected the icon withthe name of New tag group and immediately ap-pear the PPR tree with the name of TagList. Inthe same bar of tools exist a function to create anew Tag, to oppress it a new tag is believed thatit is necessary to relate it with its correspond-ing group later to capture the tag in the placethat wants to carry out the Robot operation. Inthe bar of Sequence toolbar New tag Robot isselected and is assigned this task to the robotKR16, so that the Robot can to carry out thewelding tasks is necessary to add the tags to theRobot tasks for which the tool is used with thename of Add tags. The Robot type selected isKR16 and the Weld path with this the Robotoperations are set automatically. To completethe programming process, the Robot only haveto adjust the movement trajectories. This canbe carried out with the help of the Teach pen-dant and moving the compass to determine therobot movement or also whit a function insidethe Teach Pendant called Jog, which manipu-lates the Robot movement through each one oftheir degrees of freedom.
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4.1 Some Simulation
In this part of the simulation it is very impor-tant to restore the initial state, with the objec-tive of maintaining the positions of all the intactcomponents, this can be carried out with thetoolbar Simulation and the icon “Save the ini-tial state”, once carried out this, the followingstep is to select inside the same toolbar the iconcalled “Robot task simulation”, the Robot KR16is selected and automatically appears the toolbarcalled “Process simulation” for which it is neces-sary to select the play button and it begins theprocess of simulation of the Robot KR16. SeeFigure 5
Tags
Figure 5: Simulation process of the workcell
Once the welding process is simulated, it isnecessary to revise its results to have an analysisof the Robot tasks, possible collisions, creationof the welding, among others.
4.2 Results
From the simulations we can observe that atfirst sight the work cell is well distributed, butcarrying out a study of contacts and collisionsamong those components, the software providesthe following results in a matrix of contacts orclashes, the figure 6 shows the results of theclashes that cause bigger relevance due to a col-lision detected between the torch and the worktable, besides small contacts among robot artic-ulations. See Figure 6
Figure 6: Matrix simulation results
The figure 6 shows on the left side a graphof the area affected by the collision between theRobot and the torch with one product named“Body Side Outer”. On the right side, it showsthe relation matrix of collisions and contacts,among all the devices, having as results a total of19 interferences, from which 9 are collisions and10 contacts. In these results those collisions arethe most important since this damag the devicesand even the Robot.
Implementing some of the results of this work,our Corporation was given the task of buildinga robotic welding workcell, taking it the samefeatures that are proposed in the simulation. Itis contemplated both the size of the working areaof the robot as the different components of theworkcell. Moreover since our Corporation onlyworked with manual welding, now in a certainway is to train welders in a virtual environment,to provide basic knowledge and then train themin the real workcell. See Figure 7.
5 Conclusions
The Robotic manufacturing workcell integra-tion is of very high cost, for this reason it isvery important to carry out virtual prototypesto provide information that help to prevent er-rors, from the construction of the layout to thesame tasks of the process. With this work wecan observe the importance that the simulationhas when simulating a robotized welding process.
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Robot Kuka KR16
Robot Controller
Welding machine
Welding Torch
Robot Kuka KR16
Robot Controller
Welding machine
Welding Torch
Figure 7: Laboratory of welding robotics
The configuration of the cell is very important,since it avoids to problems of security danger andoffers a better visualization of the work environ-ment. It is also necessary to mention that it isof great utility to work with CAD tools, sincethe simulation can be approached more to thereality. Currently, the robot workcell it is beingimplemented in our Corporation taking into ac-count all the considerations and results from thesimulation work.
References
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[2] Jim Caie. Discrete manufacturers drivingresults with delmia v5 automation platform.ARC Advisory Group, 2008.
[3] Frank S. Cheng. A methodology for devel-oping robotic workcell simulation models.Proceedings of the 2000 Winter SimulationConference, 2000.
[4] Magnus Olsson Mikael Fridenfalk and Gun-nar Bolmsjo. Simulation based design of arobotic welding system. Div. of Robotics,Dept. of Mechanical Engineering, LundUniversity, 2000.
[5] Roger N. Nagel Mikell P. Groover,Mitchel Weiss. Robotica Industrial. Mc-Graw Hill, 1995.
[6] Antonio Lopez Pelaez. Prospectiva,robotica avanzada y salud laboral. Pre-vencion, Trabajo y Salud, 10(6-2000):14–21,2000.
[7] Norberto Pires. Welding Robots Technology,System Issues and Applications. Springer,2006.
[8] American Welding Society. CerificationManual for Welding Inspectors. AWS, 4th.edition, 2000.
[9] Enterprise Engineering Solutions. V5Robotics Training Manual. Delmia Educa-tion Services Enterprice, 2006.
[10] Nick Woodruff. Airbus aims high. IET Theknowledge Network Manufacturing, 2007.
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