One of the first questions to consider when designing a new roll forming line is the number of forming steps required to produce a profile. The number depends on material properties, the cross-section geometry and tolerance requirements, but the tool designer also wants to minimize the number of forming steps in order to reduce the investment costs for the customer. There are several computer aided engineering systems on the market that can assist the tool designing process. These include more or less simple formulas to predict deformation during forming as well as the number of forming steps. In recent years it has also become possible to use finite element analysis for the design of roll forming processes. The objective of the work presented in this thesis was to answer the following question: How should the roll forming process be designed for complex geometries and/or high strength steels? The work approach included both literature studies as well as experimental and modelling work. The experimental part gave direct insight into the process and was also used to develop and validate models of the process. Starting with simple geometries and standard steels the work progressed to more complex profiles of variable depth and width, made of high strength steels. The results obtained are published in seven papers appended to this thesis. In the first study (see paper 1) a finite element model for investigating the roll forming of a U-profile was built. It was used to investigate the effect on longitudinal peak membrane strain and deformation length when yield strength increases, see paper 2 and 3. The simulations showed that the peak strain decreases whereas the deformation length increases when the yield strength increases. The studies described in paper 4 and 5 measured roll load, roll torque, springback and strain history during the U-profile forming process. The measurement results were used to validate the finite element model in paper 1. The results presented in paper 6 shows that the formability of stainless steel (e.g. AISI 301), that in the cold rolled condition has a large martensite fraction, can be substantially increased by heating the bending zone. The heated area will then become austenitic and ductile before the roll forming. Thanks to the phenomenon of strain induced martensite formation, the steel will regain the martensite content and its strength during the subsequent plastic straining. Finally, a new tooling concept for profiles with variable cross-sections is presented in paper 7. The overall conclusions of the present work are that today, it is possible to successfully develop profiles of complex geometries (3D roll forming) in high strength steels and that finite element simulation can be a useful tool in the design of the roll forming process.

This thesis project is the final part of the Master of Science degree in Industrial Design Engineering with specialisation in Production Design at Luleå University of Technology. The project was conducted at Scania Ferruform in Luleå through January to June of 2018. Ferruform currently produces the side members to Scania’s trucks in a traditional roll forming machine. The technology of roll forming has developed and today there is a new version of the technology called 3D roll forming, which allows for forming beams with variable cross sections. Forming side members with variable web dimensions would make it possible to produce side members that have optimised form, which allows for a weight reduction in the trucks and an increase in the customers payload. The objective of this project was to identify the benefits and the limitations of investing in 3D roll forming at Ferruform’s side member production and to investigate how the technology should be implemented. The study had two aims. The first aim was to present a proposal for the implementation of 3D roll forming in the side member production at Ferruform. The second aim was to design a project plan for Ferruform’s eventual further work of implementing 3D roll forming. A literature study was performed and resulted in a theoretical framework consisting of relevant theories regarding industrial design engineering, roll forming, organisational changes and sustainability. A description and analysis of the current state was made and included the side member production, the side member paint shop and the chassis line at Scania Södertälje. The current state was mainly described through conducting interviews and performing observations. Process flow analysis was then done to visualise and analyse the current state. The next step was to describe and analyse the future state, this was done taking advantage of the available knowledge at Ferruform and analysing the material from a benchmark performed before this thesis project started. The description and analysis of the current and future state resulted in a specification of requirements. Four concepts for the future side member production were designed and evaluated with a Pugh matrix. The evaluation resulted in choosing one of the concepts for further development. The final concept for the implementation consists of keeping the traditional roll forming machine and building a new production line for 3D roll forming. The 3D roll forming machine consists of a one-part machine which requires the side members to pass through the machine twice. The results of the thesis showed that the amount of side members that would enable profit by being produced with 3D roll forming, was lower than expected. The results of the thesis also show that there are many considerations and further investigations that need to be conducted before starting an implementation could be started. However, as relevant theories propose, it is concluded that 3D roll forming is a flexible production method which would make it possible for Scania to satisfy individual customer needs and also provide the company with a long-term solution for future customer needs. / Det här examensarbetet är den sista delen för en civilingenjörsexamen inom Teknisk design med inriktning mot Produktionsdesign vid Luleå tekniska universitet. Projektet utfördes på Scania Ferruform i Luleå under januari till juni 2018. Ferruform producerar sidobalkar till Scanias lastbilar i en traditionell rullformningsmaskin. Rullformningstekniken har dock utvecklats och idag finns det en ny version av tekniken som kallas 3D-rullformning och som möjliggör formning av balkar med variabla tvärsnitt. Genom att forma sidobalkar med variabla livbredder skulle det vara möjligt att producera balkar med optimerad form, vilket innebär en viktminskning av lastbilarna och en ökning i kundernas nyttolast. Syftet med projektet var att identifiera fördelar och nackdelar med att investera i 3D-rullformning i Ferruforms sidobalkstillverkning och undersöka hur tekniken borde implementeras. Studien hade två olika mål. Det första målet var att presentera ett förslag för implementeringen av 3D-rullformning i sidobalktillverkningen på Ferruform. Det andra var att ta fram en projektplan för Ferruforms eventuella fortsatta arbete med att implementera 3D-rullformning. En litteraturstudie utfördes för att ta fram en teoretisk referensram bestående av relevanta teorier inom teknisk design, rullformning, organisationsförändringar och hållbarhet. En beskrivning och analys av nuläget genomfördes och inkluderade sidobalkstillverkningen, sidobalksmåleriet och chassimonteringen på Scania Södertälje. Nuläget undersöktes främst genom intervjuer och observationer. Processflödesanalys användes för att visualisera och analysera nuläget. Nästa steg i projektet var att beskriva och analysera det framtida läget, detta gjordes genom att ta tillvara på den tillgängliga kunskapen hos personalen på Ferruform och genom att analysera det benchmarkingbesök som gjordes innan detta projekt påbörjades. Undersökningarna av nuläge och framtid resulterade i kravspecifikation. Fyra koncept för den framtida sidobalkstillverkningen togs fram och utvärderades med hjälp av metoden Pughs matris. Utvärderingen resulterade i att ett koncept valdes ut för att utvecklas ytterligare. Det slutliga konceptet för implementeringen består av den nuvarande, traditionella rullformningsmaskinen och uppbyggnaden av en ny produktionslina för 3D-rullformning. 3D-rullformningsmaskinen består av en maskindel, vilket kräver att sidobalkarna går igenom maskinen två gånger. Projektets resultat visade att mängden sidobalkar som skulle möjliggöra vinst genom att tillverkas med 3D-rullformning, var lägre än väntat. Resultaten visar också att det är många överväganden och vidare utredningar som krävs innan en implementering kan påbörjas. Dock har jag, precis som relevant teori föreslår, också dragit slutsatsen att 3D-rullformning är en flexibel produktionsmetod som skulle göra det möjligt för Scania att tillfredsställa individuella kundbehov och även förse företaget med en långsiktig lösning för framtida kundbehov.

<p>A finite element model has been developed to simulate the forming of a channel section profile with the roll forming method. The model has been optimized to experimental results with respect to strains at the edge of the sheet and spring back of the sides of the profile. Finite element models with a coarse mesh have been compared to models with a finer mesh. The models with to fine mesh become instable and a model with a rather coarse mesh was finally chosen.</p><p>Both the models with shell elements and the models with solid elements have been used in the simulations. The simulations with shell elements gave very good results both for the geometry shape and the strains at the edge of the sheet. The reaction forces at the tools found in the simulations was only half of the reaction forces fond in the experiments.</p><p>The simulations with the solid element model showed very good results for the reaction forces while the geometry shape of the sheet was really bad. The spring back was much larger in the simulations than in the experiments.</p><p>The shell element model was chosen because of the excessive spring back with the solid element model. The spring back of the sides of the sheet differs only a few percent between the simulation and the experiment results when using the shell element model. The reaction forces at the tools in the simulation are only half of the reaction forces measured in the experiments but the results from the simulations are linearly proportional to the results in the experiments. The model that finally was chosen describe both the spring back and the strains at the edge of the sheet very well. Like in the experiments there were no signs of wrinkles at the sheet in any of the simulations.</p>

A finite element model has been developed to simulate the forming of a channel section profile with the roll forming method. The model has been optimized to experimental results with respect to strains at the edge of the sheet and spring back of the sides of the profile. Finite element models with a coarse mesh have been compared to models with a finer mesh. The models with to fine mesh become instable and a model with a rather coarse mesh was finally chosen. Both the models with shell elements and the models with solid elements have been used in the simulations. The simulations with shell elements gave very good results both for the geometry shape and the strains at the edge of the sheet. The reaction forces at the tools found in the simulations was only half of the reaction forces fond in the experiments. The simulations with the solid element model showed very good results for the reaction forces while the geometry shape of the sheet was really bad. The spring back was much larger in the simulations than in the experiments. The shell element model was chosen because of the excessive spring back with the solid element model. The spring back of the sides of the sheet differs only a few percent between the simulation and the experiment results when using the shell element model. The reaction forces at the tools in the simulation are only half of the reaction forces measured in the experiments but the results from the simulations are linearly proportional to the results in the experiments. The model that finally was chosen describe both the spring back and the strains at the edge of the sheet very well. Like in the experiments there were no signs of wrinkles at the sheet in any of the simulations.