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This paper presents a measurement case study of an automotive stamped sheet metal sub-assembly, in order to build a better understanding of flexible component tolerance stack-up in a physical production line assembly. Here, corresponding points are measured before and after assembly to capture changes in variation. Variation levels, variation stack-up, and positional shifts were investigated. It was found that that in terms of a Process Potential Index (Pp), the assembly was dimensionally better than its components. In some regions variation levels were found to be higher after assembly compared to before: in other regions, variation levels were found to be lower after assembly than before. Observation of positional shifts of features over the assembly process revealed consistent directional changes. Suspected causes are datum-shifts between assembly stations and measurement gauges, and assembly processes deforming/shifting the components in a consistent manner.

This paper identifies the need for AI based tools to supplement CAD/FEA methods. The approach discussed focuses on the capture and feedback of part based case lessons or issues that form a knowledge base for future use. Key aspects of a system to achieve this are presented. These include: Issue or problem data to be collected at source, the system to be visually based, enhance current job function, integrated with existing IT systems and work procedures, data to be readily accessible and consistent, modular approach functional access to data. The elements of a knowledge capture system for the stamping industry based on the above is discussed.

The springback of simple geometries can be predicted through theoretical analysis, however problems arise when transferring this analysis to the manufacturing environment. To determine why this is the case, a study of small curvature free bending through theoretical analysis, manufacturing data and Finite Element (FE) simulation was completed. The theoretical analysis provided an understanding of the behavior of springback and gave accurate predictions in a controlled environment. The manufacturing and Finite Element data verified the trends predicted by theory, but lacked in accuracy. The paper concludes by proposing a prediction method based solely on the geometry that is well defined in both environments.

A discrete event model was used to examine the effect of machine downtime and operating policy on the long-run average cost of an automotive stamping line. Operating policy refers to the selection of a target batch size and the circumstances under which a line stoppage will lead to the current batch being abandoned. It is assumed that the abandon/resume decision is based solely on the severity of the problem (ie repair cost) and the fraction of the batch completed. A method of identifying low cost operating policies is presented using data obtained from a real stamping plant. It is found that, within a single part framework, this approach results in significantly lower average costs than are currently achieved. It is also demonstrated that by varying the model parameters it is possible to measure the potential benefits arising from process modifications (eg decreased die-set times).

This work investigates the effect of elastic deformation of the press and die in a double action press on system performance during draw die forming. A simple linear elastic model of the complete press system was developed to show that the relative stiffness of system components controls blankholder force variation during the stroke. Calibration of the analytical model with data taken from a production press shows that the simple model explains real global system behaviour very well; and that varying system compliances can desensitise the press system to changes affecting the binder gap during the stroke. The experimental data suggests that real press and tool systems do not have an appropriate combination of system compliance, which causes large variations in blankholder force during the stroke. This model will be a useful tool for die designers and process engineers for assessing the potential impact of blankholder force variation during die design.