Simulation of the Robot Roller Hemming process

Jonkers, B. (2006) Simulation of the Robot Roller Hemming process.

Abstract:At Voestalpine Polynorm, hemming is used as an assembly method for closures (i.e. doors, hoods, tailgates and trunklids) in automotive bodies. Hemming is a process by which a metal sheet edge of an outer part is bent around an inner part. Robot roller hemming is a relatively new process. The process will be applied more and more in the future due to market demands and process development. Too little fundamental process knowhow is available. Achieving and maintaining the right product quality is therefore a trial-and-error process. Finite element analysis of the robot roller hemming process helps reducing this try-out phase. Goals are to create a more stable process and achieving the right product quality. The main targets are to create process setting guidelines which control the dimensional and surface quality and reduce the overall process time. The simulations are performed with the finite element package Abaqus®. The development of a 3D robot roller hemming simulation model is described in this report. The work presented in this report concentrates mainly on predicting the reduction in size of the outer part, called roll-in. The dimensions of the outer part have to be compensated for this roll-in, to obtain a finished product with the right dimensions. Started is with a simple 2D simulation model which can simulate the die and tabletop hemming process. The use of implicit and explicit solution methods is investigated. Both solution methods can be applied in (quasi-static) hemming simulations. An element-type comparison is performed with a small 3D tabletop model. In this implicit simulation model both solid and shell elements are used in the simulations. This way an accurate and economical element is chosen for the 3D robot roller hemming model. The continuum shell element is the most suitable element-type for large 3D robot roller hemming models. This element-type showed a realistic roll-in behaviour (roll-in after prehemming and this amount of roll-in was reduced during final hemming) during the simulation, with the smallest amount of simulation time. The differences between shell and solid elements were smaller after prehemming than after final hemming. A parameter study of the prehemming step is performed on straight flat-surface parts based on a ‘Design of Experiments’. Parameters which have a big influence on the roll-in of the process are identified with this set of simulations. After this, a response surface model is created, from the roll-in response of the simulation model on the two most important process parameters. This can be used by process engineers and robot programmers to create a stable process window by choosing the optimal process setting ranges. Furthermore, guidelines are given to prevent the forming of wave patterns along the flange which disturb the quality of finished products.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
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