A CERTIFIED AUTOMATED WELDI�G PROCESS USI�G 3D

SIMULATIO� E�VIRO�ME�T

Ignacio Dávila-Ríos

1, Luís M. Torres-Treviño

1, I. López-Juárez

2

1 Department of Industrial Engineering and Manufacturing

Corporación Mexicana de Investigación en Materiales S.A. de C.V. Ciencia y Tecnología # 790

Col. Saltillo 400 Saltillo, Coahuila 25290

Corresponding author’s e-mail: idavila@comimsa.com; ltorres@comimsa.com.mx

2Robotics and Advanced Manufacturing Research Group CINVESTAV-Saltillo

Carretera Saltillo-Monterrey, Km. 13 Ramos Arizpe, Coahuila 25900 ismael.lopez@cinvestav.edu.mx

Abstract: The welding process certification is a very important activity in industry, for that reason this paper presents the integration and development of a virtual automated welding process, based on the specifications and requirement of the rule CRAW-OT (Certified Robotic Arc Welding Operator and Technician) of the AWS (American Welding Society) using a

software simulation (Robotics 3D) to create a virtual test environment. Additionally this paper shows how the user can

test its knowledge requirements for the certification in the simulator such as programming the robot and its logic , the integration of the components of the workcell, robot security to avoid collisions and clashes, planning of welding trajectories and analysis efforts without the use of a real workcell.

1. I�TRODUCTIO�

Nowadays welders operators must be prevented before any changes in production lines, therefore proposes the integration of a robotic welding workcell inside a virtual environment in which the welders are trained based on some requirements that marks the standard CRAW-OT (Certified Robotic Arc Welding Operator and Technician)(AWS, 2004) by the American Welding Society, and turn him into a future serve as preparation for obtain such certification. The use of Robots with welding tasks, are not simple as they have to suffer different changes through time. That is one of the reasons why people produce many parts where welding is very useful for assembly (Pires, 2006). The operator usually performs the programming of the robot manually, by jogging the robot arm to each coordinate pose in space. Programming can, however, be made more accurate by the use of simulation, using so called Computer Aided Robotics. Simulation can also be a powerful tool to evaluate the skill of the welder and control some robot parameters (Ericcson, 2003). The idea of making this work stems from an application very similar carried out by the NASA with its drivers of airplanes (Norlin, 1995). Automation simulation is the process of modeling, evaluating, optimizing, and validating controls systems for automation equipment and systems in a virtual environment. This technology provides manufacturing and controls engineers an opportunity to ensure controls designs work before production starts (Caie, 2008). The use of advanced technology simulation such as related with virtual reality (VR), open new alternatives and give a huge field to develop new applications (López, 2000). Some cases of automated simulations are in the automotive industries, due that they have great quantity of automated welding process, such as DaimlerChrysler for which companies such as Kuka and Delmia have worked together. Experts of the two companies created a solution of second generation with Robots of Simulation Realists (RRS), a graphic environment provided for Delmia, in which the information of Kuka is connected in real time on their own Manipulator's movements Virtual Robotic (VCR), to reach a higher level of sensibility simulation and to demonstrate the real robot integration. The aerospace company, Airbus has also requested service from KUKA and Delmia Robotics V5, obtaining very good results in their applications (Woodruff, 2007). Some methods involve the simulation modeling graphics on a CAD / CAM system. The simulation-based computer graphics can be used not only to analyze the cycle times, but also to design their own workcell (Groover, 1995).

2. VIRTUAL E�VIRO�ME�T

To perform the tests is necessary to have a virtual environment; it is proposed the use of software Delmia Robotics 3D

simulation in which there is a wide variety of models of robots and welding torches, as well as the use of CAD software

through Solid Works® to create an atmosphere similar to a real workcell. This workcell need to be based on a laboratory

whose characteristics are the closest to a workcell welding robot, in this case was used as the reference laboratory of our

Corporation. Delmia V5 Robotics offers an easy and flexible use of solutions for the definition of tools and simulation

workcell. It provides all the necessary tools to define and to analyze the behaviors and the necessary resources to apply the process plan. Also it helps to describe exactly how parts are loaded and unloaded, fixtures, and welding processes. It can be carried out easy and with accuracy the validation and analysis of the production processes through simulations based physically on the resources. Below presents the atmosphere of the simulator as well as different brands of robots that can be used. See figure1.

MOTOMAN Panasonic FANUC

KAWASAKIYAMAHAKUKA

ABB

Toolbars

PPR Tree

Compass

Figure 1. Main screen of the Robotics V5

For the design of specific components the Solid Works® was used, due to the compatibility that it has with the Robotics

V5® when exporting the pieces and also it allows working in 3D. This software was used to consider all the components to

scale. Once all the designs of the workcell are ready, then the following step is to integrate everything in the simulator, to carry out the welding tasks with the Robot.

3. VIRTUAL DEVELOPME�T OF A ROBOTIC WORKCELL

For the workcell simulation, some of the components that are not designed have to be designed separately. For instance, a welding table, a welding machine, conveyor and the KRC2 robot controller. These components are designed in the software

Solid Works® and exported to Robotics V5

®.

3.1 Designs in Solid Works®

Once one has the real measures of the components, they are designed in the software Solid Works®, or in any other design

software in 3D that allows exports to the Robotics, as it is the case with CATIA®, NX

® (before Unigraphics) among others.

To design in Solid Works®. First the measures of the real components are taken, the software opens in the “piece” function,

this function allows to create a piece, which has to be drawn first on a plane inside a function called “croquis”, these designs have to be carried out on a plane, which can be of raised type, plants or lateral view; once obtained the drawings of the component the following step is to carry out operations. Among the most usual is “out extrusion” that is to transform

the two dimensional drawing to a piece in 3D. See Figure 2. Once the components are designed, the next step is to export

them to the software Robotics 3D®, so that they can be used in the robotics welding process simulation.

Figure 2. Workcell in Solid Works® environment

3.2 Welder training on Virtual Environment

For the welder training in the Delmia Robotics 3D® is necessary to provide the following basic simulator knowledge: of the

layout in the simulation software Robotics V5®, is it necessary to open a document in “process” mode, this to be able to

work in the simulation environment and it can open the “PPR tree”, it is necessary to program in the beginning mode and simulation resource the option of “Device task definition”. To create the layout in the beginning screen it is necessary, to insert the products and resources; the insert of the products and resources will depend in the way it wants them to use in their process. Through the “toolbars” in the option of insert, it is inserted as product a Body Side Assembly Part and such resources Robot Kuka KR16, the table of welding, the torch, the workcell and a riser (platform for the Robot), once all the components are on the screen PPR, the following step is to carry out a “Snap and attach” that serves to unite the riser with the robot. For mounted of the torch in the robot the toolbar “Robot management” is used; when oppressing the icon “Set tool” immediately appear a dialogue box called “Robot Dress up”, here only it is necessary to select inside the tree PPR the Robot and the torch so that it is attached in the Robot.

The following step is to accommodate the other resources and the product such they are wanted to place physically, this operation can be carried out by the compass which has a function called “Snap automatically to Select Object”.

4. TESTS I� SIMULATIO� E�VIRO�ME�T

This section shows how the welder performed some test on the simulator for which it its necessary to create the tags and those Robot task associated to them, the tags are those points for which the robot will carry out the welding operations. Inside the bar, “Tag toolbar” selected the icon with the name of “New tag group” and immediately appear the PPR tree with the name of “Tag List”. In the same bar of tools exist a function to create a new tag, to oppress it a new one is believed that it is necessary to relate it with its corresponding group later to capture the tag in the place that wants to carry out the Robot operation. In the bar of “Sequence toolbar” “new tag Robot” is selected and is assigned this task to the robot KR16, so that the Robot can to carry out the welding tasks is necessary to add the tags to the Robot tasks for which the tool is used with the name of “Add tags”. The Robot type selected is KR16 and the Weld path with this the Robot operations are set automatically. To complete the programming process, the Robot only has to adjust the movement trajectories. This can be carried out with the help of the “Teach Pendant” and moving the compass to determine the robot movement or also whit a function inside the “Teach Pendant” called “Jog”, which manipulates the Robot movement through each one of their degrees of freedom.

4.1 Some Simulation

In this part of the simulation it is very important to restore the initial state, with the objective of maintaining the positions of all the intact components, this can be carried out with the toolbar simulation and the icon “Save the initial state”, once carried out this, the following step is to select inside the same toolbar the icon called “Robot task simulation”, the Robot KR16 is selected and automatically appears the toolbar called “Process simulation” for which it is necessary to select the play button and it begins the process of simulation of the Robot KR16. The welder must be able to mount the torch in the Robot; this can also be simulated in this software. See Figure 3

TagsTorch

MountedTorch

Figure 3. Mounted torch and Simulation process of the workcell

All this steps should be followed by the welder and once the welding process is simulated, it is necessary to revise the results to have an analysis of the Robot tasks, possible collisions, and creation of the welding trajectories, among others.

4.2 Results

The welder must be able to interpret all the results of this simulator, the examination of the standard CRAW-OT (Certified Robotic Arc Welding, Operator and Technician) by the AWS is designed to test the knowledge of welding fundamentals and robotics arc welding systems, in the following table presents the subjects of the standard and they can be evaluated in the simulator. See Table 1.

Table 1. Comparison between Real Workcell and Virtual Simulator

Subject Real Workcell Virtual Simulator

Weld Equipment Setup �

Welding Processes � �

Weld Examination �

Definitions and Terminology � �

Symbols �

Safety � �

Destructive Testing �

Conversion and Calculation � �

Robot Programming � �

Welding Procedures � �

Programming Logic � �

Kinematics Concepts � �

Robot Arc Weld Cell Components � �

One of the most important parts is programming the robot, which is considered very difficult to evaluate because each brand has its own robot programming code, which is something easy to evaluate in the simulator since it provides us with the conversion of program between the different brands that exist in the market. We made a simulation of trajectories in the software and can be evaluated according to the welder robot using this, next shows the program code of a welding trajectory with different kind of welding robots. See Table 2.

Table 2. Examples program code of three different brands of robot

Robot KUKA Robot FANUC Robot RAPID

&ACCESS RVP &REL 1 &PARAM EDITMASK = * DEF Welding_Task( ) ;FOLD PTP ViaPoint2 Vel= 50 % PDAT1 Tool[1]:cell2-torch.1. ToolFrame Base[0];%{PE} %R 4.1.5,%MKUKATPBASIS, %CMOVE,%VPTP,%P 1:PTP, 2:ViaPoint2, 3:, 5:50, 7:PDAT1 $BWDSTART=FALSE PDAT_ACT=PPDAT1 BAS(#PTP_DAT) ;ENDFOLD END

/PROG Welding_Task /ATTR OWNER = MNEDITOR; PROG_SIZE = 0; FILE_NAME = ; VERSION = 0; LINE_COUNT = 0; MEMORY_SIZE = 0; PROTECT = READ_WRITE; TCD: STACK_SIZE = 0, TASK_PRIORITY = 50, TIME_SLICE = 0, BUSY_LAMP_OFF = 0, ABORT_REQUEST = 0, PAUSE_REQUEST = 0; DEFAULT_GROUP = 1,1,1,*,*; /POS P[1]{ GP1: UF : 1, UT : 2, CONFIG: 'S 2 , 0, 0, 0', X = 1157.208 mm, Y = 212.886 mm, Z = 1002.855 mm, W = 136.239 deg, P = 11.951 deg, R = 103.725 deg

};

%%% VERSION:1 LANGUAGE:ENGLISH %%% MODULE Welding_Task_mod PERS robtarget ViaPoint2:= [[1157.208,212.886,1002.8551,0,0,0 PERS robtarget Tag1:=[[938.236,285.366,460.429], [0.111893,0.51089,0.851944,0.025754] ,[,0,0,0],[9E+09,9E+09,9E+09,9E+09,9E+09,9E+09]]; PERS robtarget PROC Welding_Task() MoveJ ViaPoint2,Default,Default,cell2-torch_1_ToolFrame; MoveJ Tag1,Default,Default,cell2-torch_1_ToolFrame; ENDPROC ENDMODULE

Finally it is shown the integration as a result to scale of the virtual workcell of welding robotics in which will be able to be carried out a test to the operator before involving in a real environment. See Figure 4.

Figure 4 Virtual Robotic Welding Workcell

5. CO�CLUSIO�S

This paper shows the importance of simulation by using both virtual environments and prototypes, before the welders involving on the real robotic welding workcell. It also highlights the usefulness of CAD tools to get more real simulations. The Robotic manufacturing workcell integration is a very high cost, for this reason it is very important to carry out virtual prototypes to provide information that help to prevent human errors, like a collisions, clashes, etc. The configuration of the workcell is very important, since it avoids to problems of security danger and offers a better visualization of the work environment. It is also necessary to mention that it is of great utility to work with CAD tools, since the simulation can be approached more to the reality. Currently, the robot workcell it is being implemented in our Corporation taking into account all the considerations and results from the simulation work. For conventional welders, working in a virtual environment, is very important, since they are expected to definitions and basic knowledge on welding robot, this work shows an exact replica of a robotics welding laboratory in which to develop tests both in a real environment as a virtual, intends to the welders to be involved in a virtual environment before carrying out tasks in an automated welding process.

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