Visualizing the Effects of Geometrical Variation on Perceived Quality in Early Phases

Doctoral thesis, 2013

In a perfect world, geometrical variation in a manufacturing process would not exist. Every component produced in a series would have the exact same dimensions and, when observed by a trained eye, look exactly identical. However, the world is not perfect and neither are manufacturing processes. When developing new products, this fact must be considered since a product, in most cases, consists of several components that are assembled together. The geometrical variation may impact the function of the product, the ability to assemble the product and the aesthetics of the product. Geometrical variation may thereby affect the customer’s perception of the overall quality of the product. That is the reason why the visual appearance of the relationships between components, also defined as split-lines, in many cases is of exceptional importance in the automotive industry. Perceived quality of split-lines is one of several aspects of perceived quality, which is an overall quality as perceived through the human senses. This thesis is concerned with methods for simulating and evaluating perceived quality in early phases of the product development process. Early simulation and evaluation of perceived quality can minimize the number of corrections in late phases, increase quality and save both time and money. The potential for savings is of substantial importance as projects in the automotive industry are conducted with consistently decreasing budgets and tighter time plans. The thesis elaborates on methods for performing non-rigid variation simulation in early phases when data maturity is low. These are placed in a proposed framework for managing and supporting evaluation of perceived quality in general during the development process based on the maturity of the data available. Some activities in the framework are widely used in the automotive industry while others are based on recent research in the area. The thesis reports on several case studies that highlight different aspects in the framework. It shows how mesh morphing can be used to predict component variation and component stiffness in very early phases by using historical inspection data and design solutions as input. This facilitates a way of visualizing the effects of geometrical variation on perceived quality in very early phases by utilizing reference data linked from previous projects. Another study was performed to investigate the applicability of non-FEA-based deformation methods for simulation and visualization of effects of geometrical variation on perceived quality. Results showed that many of the involved engineers and managers endorsed the alternative of taking decisions based on simulated results from the method. They also emphasized the advantage of having the possibility to visualize expected scenarios early on in the development phase. Based on results from this study, a follow-up study was performed to show how the method could be applied in industry. Also included in this thesis is a study showing that evaluators perceive rigid and non-rigid visualizations differently. This further supports the need of non-rigid simulations and visualizations for correct judgments of the virtual models. Unfortunately, most non-rigid simulation models are more time demanding to build, compared to rigid ones, and may consequently not be applied in all cases. Therefore, a study has been conducted to investigate in which vehicle areas non-rigid variation simulations are recommended. These results are expected to support and improve the work with perceived quality in the industrial development process, and they expand the body of scientific knowledge in the research field.