| 1. |
- Carlson, Johan, 1972, et al.
(författare)
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Minimizing Dimensional Variation and Robot Traveling Time in Welding Stations
- 2014
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Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 23:C, s. 77-82
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Konferensbidrag (refereegranskat)abstract
- Complex assembled products as an automotive car body consist of about 300 sheet metal parts joined by up to 4000 spot welds. In the body factory, there are several hundred robots organized into lines of welding stations. The distribution of welds between robots and the welding sequences have a significant influence on both dimensional quality and throughput. Therefore, this paper proposes a novel method for quality and throughput optimization based on a systematic search algorithm which exploits properties of the welding process. It uses approximated lower bounds to speed up the search and to estimate the quality of the solution. The method is successfully tested on reference assemblies, including detailed fixtures, welding robots and guns.
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| 2. |
- Jareteg, Cornelia, 1986, et al.
(författare)
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Geometry Assurance Integrating Process Variation with Simulation of Spring-in for Composite Parts and Assemblies
- 2014
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Ingår i: Proc. of ASME 2014 International Mechanical Engineering Congress & Exposition. - 9780791846438 ; 2A
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Konferensbidrag (refereegranskat)abstract
- Geometrical variation and deviation in all manufacturing processes affect quality of the final product. Therefore geometry assurance is an important tool in the design phase of a new product. In the automotive and aviation industries where the use of composite parts is increasing drastically, new tools within variation simulations are needed. Composite parts tend to deviate more from nominal specification compared to metal parts. Methods to simulate the manufacturing process of composites have been developed before. In this paper we present how to combine the process variation simulation of composites with traditional variation simulations. The proposed method is demonstrated on a real complex subassembly, representing part of an aircraft wing-box. Since traditional variation simulation methods are not able to capture the spring-in and the special deviation behavior of composites,the proposed method adds a new feature and reliability to the geometry assurance process of composite assemblies.
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| 3. |
- Jareteg, Cornelia, 1986, et al.
(författare)
-
Geometry Assurance Integrating Process Variation with Simulation of Spring-In for Composite Parts and Assemblies
- 2016
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Ingår i: Journal of Computing and Information Science in Engineering. - : ASME International. - 1530-9827 .- 1944-7078. ; 16:3
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Tidskriftsartikel (refereegranskat)abstract
- Copyright © 2016 by ASME.Geometrical variation and deviation in all the manufacturing processes affect the quality of the final product. Therefore, geometry assurance is an important tool in the design phase of a new product. In the automotive and aviation industries where the use of composite parts is increasing drastically, new tools within variation simulations are needed. Composite parts tend to deviate more from nominal specification compared to metal parts. Methods to simulate the manufacturing process of composites have been developed before. In this paper, we present how to combine the process variation simulation of composites with traditional variation simulations. The proposed method is demonstrated on a real complex subassembly, representing part of an aircraft wing-box. Since traditional variation simulation methods are not able to capture the spring-in and the special deviation behavior of composites, the proposed method adds a new feature and reliability to the geometry assurance process of composite assemblies.
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| 4. |
- Jareteg, Cornelia, 1986, et al.
(författare)
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Variation simulation for composite parts and assemblies including variation in fiber orientation and thickness
- 2014
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Ingår i: Procedia CIRP CATS 2014. 5th CATS 2014 - CIRP Conference on Assembly Technologies and Systems. - : Elsevier BV. - 2212-8271. ; 23
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Konferensbidrag (refereegranskat)abstract
- All manufacturing processes are afflicted by geometrical variation, which can lead to defect products. A simulation tool for geometry assurance analysis is therefore important in the design process. The use of composites has recently increased drastically, but there is still a lack of understanding about the effects of variation in such parts. A method for predicting variation in subassemblies, including variation in fiber orientation and ply thickness for composites is presented. The approach is demonstrated on an industrial case and finite element analysis is used to calculate the deformation. In particular, contribution from variation in material properties to the variation in critical points is analyzed. The results indicate that material uncertainties have a small impact on the geometric variation for the test case.
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| 5. |
- Landahl, Jonas, 1986, et al.
(författare)
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Using product and manufacturing system platforms to generate producible product variants
- 2016
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Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 44, s. 61-66
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Konferensbidrag (refereegranskat)abstract
- Product platforms have proven efficient as a means to reduce lead-time and increase product quality simultaneously. When using platforms to generate a family of products, the number of variants that need to be managed in manufacturing increases. To succeed with this, the manufacturing system needs to be maintained in a similar level of flexibility as the product platform. However, there is seldom a joint decision behind each and every conceptual product variant during development, regarding capability in manufacturing. For example, when considering producibility, some product variants require better tolerances than what the manufacturing processes can deliver. This uncertainty can be reduced, by making producibility analyses of a set of conceptual product variants. By performing several different analyses, knowledge can be gained, and joint decisions can be made about cross product-manufacturing aspects. The activities can be systematically arranged to gradually eliminate unfeasible conceptual product variants. In this paper we show how an integrated PLM architecture can be used to create sufficient knowledge as a basis for joint product and manufacturing decisions. The utmost company benefit of this is to reduce lead-time by taking manufacturing capability into account when developing product families.
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| 6. |
- Segeborn, Johan, 1972, et al.
(författare)
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Evaluating genetic algorithms on Welding sequence optimization with respect to dimensional variation and cycle time
- 2011
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Ingår i: Proceedings of the ASME 2011 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2011 August 29-31, 2011, Washington, DC, USA (Volume 5: 37th Design Automation Conference, Parts A and B ). - 9780791854822 ; :Paper no. DETC2011-48393, s. 697-704
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Konferensbidrag (refereegranskat)abstract
- Spot welding is the predominant joining method in car body assembly. Spot welding sequences have a significant influence on the dimensional variation of resulting assemblies and ultimately on overall product quality. It also has a significant influence on welding robot cycle time and thus ultimately on manufacturing cost. In this work we evaluate the performance of Genetic Algorithms, GAs, on multi-criteria optimization of welding sequence with respect to dimensional assembly variation and welding robot cycle time. Reference assemblies are fully modelled in 3D including detailed fixtures, welding robots and weld guns. Dimensional variation is obtained using variation simulation and part measurement data. Cycle time is obtained using automatic robot path planning. GAs are not guaranteed to find the global optimum. Besides exhaustive calculations, there is no way to determine how close to the actual optimum a GA trial has reached. Furthermore, sequence fitness evaluations constitute the absolute majority of optimization computation running time and do thus need to be kept to a minimum. Therefore, for two industrial reference assemblies we investigate the number of fitness evaluations that is required to find a sequence that is optimal or a near-optimal with respect to the fitness function. The fitness function in this work is a single criterion based on a weighted and normalized combination of dimensional variation and cycle time. Both reference assemblies involves 7 spot welds which entails 7!=5040 possible welding sequences. For both reference assemblies, dimensional variation and cycle time is exhaustively calculated for all 5040 possible sequences, determining the optimal sequence, with respect to the fitness function, for a fact. Then a GA that utilizes Random Key Encoding is applied on both cases and the performance is recorded.It is found that in searching through about 1% of the possible sequences, optimum is reached in about half of the trials and 80-90% of the trials reach the ten best sequences. Furthermore the optimum of the single criterion fitness function entails dimensional variation and cycle time fairly close to their respective optimum. In conclusion, this work indicates that genetic algorithms are highly effective in optimizing welding sequence with respect to dimensional variation and cycle time.
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| 7. |
- Söderberg, Rikard, 1963, et al.
(författare)
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Toward a Digital Twin for real-time geometry assurance in individualized production
- 2017
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Ingår i: CIRP Annals - Manufacturing Technology. - : Elsevier BV. - 1726-0604 .- 0007-8506. ; 66:1, s. 137-140
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Tidskriftsartikel (refereegranskat)abstract
- Simulations of products and production processes are extensively used in the engineering phase. To secure good geometrical quality in the final product, tolerances, locator positions, clamping strategies, welding sequence, etc. are optimized during design and pre-production. Faster optimization algorithms, increased computer power and amount of available data, can leverage the area of simulation toward real-time control and optimization of products and production systems - a concept often referred to as a Digital Twin. This paper specifies and highlights functionality and data models necessary for real-time geometry assurance and how this concept allows moving from mass production to more individualized production.
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| 8. |
- Söderberg, Rikard, 1963, et al.
(författare)
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Virtual Geometry Assurance Process and Toolbox
- 2016
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Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 43, s. 3-12
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Konferensbidrag (refereegranskat)abstract
- Geometrical variation in individual manufacturing and assembly processes often propagates and accumulates, resulting in products that do not fulfil functional, esthetical or assembly conditions. Geometrical quality problems are often discovered late with huge cost for changes and delays as a consequence. The ability to simulate and foresee geometry problems early, allows robust concepts to be developed, tolerances and assembly sequences to be optimized and key inspection features to be selected.This paper presents a comprehensive geometry assurance process with an efficient set of tools that supports the geometry assurance process from early concept phases, through verification and pre-production and finally during production.
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| 9. |
- Wärmefjord, Kristina, 1976, et al.
(författare)
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A Fixture Failure Control Chart For Variation Caused By Assembly Fixtures
- 2012
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Ingår i: roceedings of the ASME 2012 International Mechanical Engineering Congress & Exposition, IMECE2012, Houston, Texas, USA. - 9780791845196 ; :PARTS A, B, AND C, s. 1807-1814
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Konferensbidrag (refereegranskat)abstract
- In the auto body assembly process, fixtures are used to position parts during assembly and inspection. If there is variation in the positioning process, this will propagate to the final assembly. There are also other sources of variation in the final assembly, such as variation in parts due to previous manufacturing steps. To facilitate the separation of the different sources of variation, and thereby also improve fault diagnosis, a fixture failure subspace control chart is proposed. This control chart is based on a multivariate T2-chart, but only variations in the fixture failure subspace are considered. The method is applied to two industrial case studies with satisfying results.
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| 10. |
- Wärmefjord, Kristina, 1976, et al.
(författare)
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A Measure of the Information Loss for Inspection Point Reduction
- 2008
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Ingår i: ASME 2008 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, IDETC/CIE2008; Brooklyn, NY; United States; 3 August 2008 through 6 August 2008. - 9780791843253 ; :PARTS A AND B, s. 693-700
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Konferensbidrag (refereegranskat)abstract
- Since the vehicle program in automotive industry gets more and more extensive, the costs related to inspection increase. Therefore, there are needs for more effective inspection preparation. In many situations, a large number of inspection points are measured, despite the fact that only a small subset of points is needed. A method, based on cluster analysis, for identifying redundant inspection points has earlier been successfully tested on industrial cases. Cluster analysis is used for grouping the variables into clusters, where the points in each cluster are highly correlated. From every cluster only one representing point is selected for inspection. In this paper the method is further developed and multiple linear regression is used for evaluating how much of the information that is lost when discarding an inspection point. The information loss can be quantified using an efficiency measure based on linear multiple regression, where the part of the variation in the discarded variables that can be explained by the remaining variables is calculated. This measure can be illustrated graphically and that helps to decide how many clusters that should be formed, i.e. how many inspection points that can be discarded.
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