Modular Welding Fixtures for Robotic Cells Jan Semjon 1, a, Mikulas Hajduk 1,b, Rudolf Janos 1,c, Marek Vagas 1,d

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1 Applied Mechanics and Materials Online: ISSN: , Vol. 309, pp doi: / Trans Tech Publications, Switzerland Modular Welding Fixtures for Robotic Cells Jan Semjon 1, a, Mikulas Hajduk 1,b, Rudolf Janos 1,c, Marek Vagas 1,d 1 Technical university of Kosice, Faculty of Mechanical Engineering, Letna 9, Kosice , Slovakia a jan.semjon@tuke.sk, b mikulas.hajduk@tuke.sk, c rudolf.janos@tuke.sk, d marek.vagas@tuke.sk Keywords: Robot, Welding fixtures, Modules. Abstract. This paper describes the proposal of welding fixtures which achieves pre -arrangement of individual parts of fixture based on suitable modules. Also is focused on methodological process of their design using modularity principle and reconfigurability. Describe procedure of designing fixture with emphasis to specific requirements for welding fixtures in robotic welding. Take advantages of simple substitution of individual modules welding fixtures by database compatible with modules in 3D environment. Optimization and control of collision status is realized in simulation environment ABB Robot Studio. Introduction Basic functions of welding fixtures are: accurate positioning and clamping (fixating) of welded parts, and also ensured their mutual position from accuracy point of view: possibility to fast inserting and removing parts and ensuring optimization accessibility of welding tong welding pliers to welded points. Fast inserting and removing parts either manually or automatically is very important mainly for spot welding, where in some cases is welding time less as handling time with welds. Present time pushes to companies which used welding fixtures to adapted still more and more challenging requirements from clients and pushes to innovation their manufacturing process. Achievements of high accessibility to innovative parts are not possible through dedicated fixtures. This requirement is suitable to achieve through various functional modules clamped, located with variable dimension (high setting) which are classified to individual types. Modular principle based on functional compatibility units allows us to reconfiguring of fixtures for very shortly time. Basic Parts of Welding Fixtures Welding fixtures are peripheral devices of robotized workplace, see figure 1, determined to accurate positioning of welded parts toward to robot. It s controlled by control system of robot or superior system. Welding fixture of robotized workplace should have attached fixed or through suitable type of positioner equipped with holder for fixture with one or more axes. Due to this is possible to attach better accessibility to welding points. Basic parts of welding fixtures include: Basic frames, plates, Horizontal and vertical structural elements, Locating elements, Clamping equipment, Connecting elements, consoles, Sensor, energy distribution. Variety of products requires also various solutions of fixture. This variety raises high requirement to flexibility of fixture i.e. fast pre sorting to new type of weld. Constructional arrangement of welding fixtures depends from many factors. Important includes: number, size and weight of welded parts, type of used robot work envelope, type of welding (spot, arc, laser), speed of welding, tact of workplace, method of inserting and removing welded parts, financial possibilities and etc. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-11/05/16,20:39:42)

2 Applied Mechanics and Materials Vol Fig.1. Model of welding fixture Common problem with proposal of modular fixtures is designing of basic concept type and dimensional type for individual parts of fixture. Approach to this solution is based on modular principle i.e. determination of dimensional line at individual parts of fixtures and method their fast connection and disconnection in their mutual compatibility. Proposal Succession of Fixture for Robotized Workplace Proposal succession of welding fixtures for robotized workplace, figure 2 is developed from basic requirement, including: Shape of welded parts dimensions, Material of welded parts, Process of their mutual connection to resultant assembly, Method of inserting and removing parts, Tact of manufacturing, Type of welding method, dimensions and technological parameters of spot welding pliers (welding tongs), Type and keeping method of necessary energy distribution (air supply, electricity, suction, etc.), Security requirements to operation, methods of approaches to operators and maintenance for fixture. Based on analysis of boundary criteria is for proposal of welding fixture possible to determine following steps: Determining of mutual position of parts and determining process their inserting, Choice from database modules, preliminary conception of fixture in 3D, Choice of locating and clamp points, Testing availability of robot to welded points (places), Constructional design of fixture, Creating of program for robot through off-line programming in simulation program due to testing of accession to welds and also due to monitoring of collision status, Debugging of program directly at real robotized workplace.

3 82 III Central European Conference on Logistics Fig.2. Methodological progression at designing of welding fixture 1. Determination of mutual position parts and determination of sequence their inserting (Position of parts in fixture) Based on the individual input parameters of welded components and technological sequence are determined succession of their placing, positioning and orientation in space before welding. The output from this analysis is definition of the dimensional characteristics of the fixture (maximal length, minimal height of welded parts etc.) like also selection suitable approach of end effector to welded parts, figure. 3.

4 Applied Mechanics and Materials Vol Fig.3. Sequence of connecting individual parts at welded assembly and orientation of welded parts in space 2. Selection of location and clamping points (Selection of location and clamping points (surfaces)) In this step, preliminary are determined possible points or surfaces for the setting and positioning and their shape as well, see figure 4. Further, determined are also the possible clamping points, necessary clamping force (surfaces) and possible positions of the clamps, sensors and energy. Fig.4. Selection of location and clamping points 3. Selection of individual modules from database (Modules selection, preliminary proposal of fixture Outputs from the first and second step define the requirements placed on the selection of the individual modules of fixture. The selection is created from the formed database of the individual modules applying the interactive method. In table 1 is shown selection of some types in individual database of modules. Chosen modules must be mutually compatibility and also must be secured through suitable links and relations. The result is a set of the suitable modules, which can be used for constructing of fixture. Table.1. Modules for construction of fixture

5 84 III Central European Conference on Logistics Next step is calculating respectively selection of necessary clamping forces, which holds part in defined position without surface damage. Based on tests realized at sheets used in automotive industry is possible to say, that clamping force grows at least twice near to increasing of sheet thickness about 0,5 mm (in case of distance putting at two support each other about value 200 mm). 4. Design assembly of fixture (Constructional design of fixture) Design of the assembly of the fixture is conducted in CAD system applying 3D modelling and when selected the modules, decision is made based on the mutual dimensional and functional compatibility. The assembly of the fixture is in this step tested with the objective to assume requested accuracy, in 3D is tested the accessibility to the welded points and determined are the possible positions of welding tongs or determined is their optimum position. Figure 5 shows a view at designed welding fixture before inserting of welding parts. There are placed points of weld n. 1 and 2, clamping consoles of welds n. 3 and n. 4 and pneumatic clamps to adherence of welds n. 5 and n. 6. Fixtures with consoles are placed in opened status due to simply inserting parts. Also must be maintained correct sequence of inserting individual parts (from welds n. 1 till n. 5). Figure 6 shows a view to designed welding fixture. There are shown all welding parts in correct position held by consoles which is placed on pneumatic fixtures. In this point of proposal for welding fixture suitable at robotized welding is possible verification and test functionality of fixture. For verification of functionality welding fixture is suitable to check some basic points, especially: correct location of welding parts checking their position at space, stability of individual parts in fixture, quality location of individual parts, accessibility of welding pliers (welding torch) to welding positions, correct down force of individual consoles in point for connection with weld, contact force of fixtures, simply inserting of individual parts and simply removing done weld. Fig.5. Assembly of welding fixture without welding parts

6 Applied Mechanics and Materials Vol Fig.6. The assembly of welding fixture prepared for welding In consideration of previous requirements follows checking all parameters of robot and end effector. The checking of dead position at robot arms and maximum movements of all axes is checked on 3D model of robot. In necessary case is chosen and designed suitable base under robot. All this steps are necessary for achievement of suitable robot accessibility to all points for welding. In last step is defined a base position of robot at space because this is the way to simply and safe inserting and removing all of welding parts. 5. Off-line preparing of program for robot (Off-line programming, generating of program for robot) If all previous requirements are preserved is possible access to creating of program for robot. The program of robot can be created at any simulating program environment, which must by compatible with chosen robot and must preserved work with imported folders. Within this environment as RobCAD, ABB Robot studio and similar is possible to path simulation of all robot axis, testing of collision relationships, and also movements optimizing for decreasing of secondary times. After successful ending of all previous steps is necessary generating program for robot, figure 7. Fig.7. Off-line program for robot

7 86 III Central European Conference on Logistics 6. Debugging of robot program on real workplace (Debugging of program at workplace) Generated program is inserted to control system of robot, where continues its ongoing testing and debugging, figure 8. Operator of robot workplace, in necessary case fine tunes movements of robot directly on real workplace and supervises accessibility, accuracy and quality of welding. In case of hardly repairable error must operator of robot analyzed reasons and applies suitable countermeasures. Conclusions Fig.8. Robotic workstation for spot welding The target of paper was to design a modular welding fixture, which is suitable for using in automotive industry. The fixture must accomplish requirements of modularity. This is important for reconfigurable and remodel from one type of fixture to another for simply and time-saving at operators. Next aim at proposal of modular welding fixture is ability to simplify a design process for welding fixtures to designers. This leads to an effective usage of designer s work as well as to decrease of costs at fixture manufacturing. Acknowledgments This contribution is the result of the project implementation: VEGA 1/0810/11 Principles of profiling and cooperation multirobotic systems. References [1] Bi Z.M, Zhang W.J. Flexible fixture and future direction. International Journal of production Research. v.39, (2007). [2] Chan K, Banhabit B, Dai M. Reconfigurable Fixturing System for Robotic assembly, Of Manufacturing Systems, No. 3 (1992). [3] Hajduk M, Semjon J, Vagas M. Design of the welding fixture for the robotic station for spot welding based on the modular concept, Acta Mechanica Slovaca, 4, (2009) [4] Hajduk M, Tolnay M, Groholova M, Vojtech D. Methodological frame of reconfigurable manufacturing systems design, Acta Mechanica Slovaca, 2-A (2008), [5] Nieszporek T, Szymanski W, Rygallo A. A new control system of the industrial manipulator RIMP-401, Acta Mechanica Slovaca 2-A (2008).

8 Applied Mechanics and Materials Vol [6] Rares P, Macedon G, Constantin B. Constructive solutions at the modular fixtute of the workingpart at the flexibile manufacturing cell TMA-AL-550: IMT Oradea, (2010). [7] Semjon J, Janos R, Varchola M, Vagas M, Balaz, V. Moduľnyj princip projektirovanija svaročnych prisposoblenij dľa robotizirovannych jačejek, ATM Kijev, (2012) [8] Svetlik J, Semjon J. Workspace analysis of a homogenous modular kinematical structure build on the principle of connecting rotary modules, International Scientific Herald, (2012) [9] Stas O, Tolnay M, Magdolen L. Application of artificial intelligence in manufacturing systems, ICMEE 2009 : Singapore, (2009), [10] Tolnay M, Bednar T, Bachraty M. Motion model application in manipulation device design, OPTIROB Romania (2008) [11] Vagas M, Hajduk M, Semjon J, Pachnikova L, Janos R. The view to the current state of robotics, Advanced Materials Research, Vol (2012) [12] Velisek K, Pastierovic M. Intelligent fixtures Ingredients production proces, MtF STU, Trnava, (2010).

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