Design and evaluation of in-line product repair strategies for defect reduction in the production of electric drives

Manufacturing companies are continuously facing the challenge of operating their manufacturing processes and systems in order to deliver the required production rates of high quality products of increasing complexity, with limited use and waste of resources. This aspect is particularly critical in emerging sectors, such as the e-mobility industry, where state of the art quality and process control technologies show strong limitations. This paper proposes new solutions for implementing in-line product repair strategies in the production of electric drives for the automotive industry. Moreover, it develops an innovative quantitative tool to estimate the impact of the proposed strategies on the overall process-chain performance. The benefits of the approach are validated within a real industrial context

Proactive quality control system for defect reduction in the production of electric drives

State of the art in multi-stage production systems is End-Of-Line (EOL) quality control. The main drawback of EOL inspection is the off-line inspection at the final stage of the manufacturing chain, where already all possible defects of the production chain have been accumulated. Thus, a defective workpiece is machined wasting time, money and energy resources for creating a final product, which is out of tolerances and has to be recycled or scrapped. To overcome this drawback it is necessary to create solutions to reduce either defect generation or defect propagation. This paper focusses on the second approach, which aims at repairing defective workpieces by adapting consecutive process parameters in a multi-stage production system (downstream repair). By applying this concept to the production of electrical drives for power train applications, the effort needed for EOL testing can be reduced by shifting testing steps into the previous process chain. The currently used total flux measurement of laminated steel stacks is replaced by a space-resolved measurement. This permits the identification and local allocation of deviations in the magnetic field due to defective or weak magnets. The downstream repair strategy solves an optimization problem in order to compensate deviations in the magnetic field of single laminated steel stacks by adapting the assembly stage. Two repair strategies are discussed within this paper, namely sequential and selective assembly. In the proper assembling sequence, the laminated steel stacks are then assembled on the rotor according to the optimal assembling policy. Thus deviations of the laminated steel stacks are compensated. © 2013 IEEE

A cyber-physical system for quality-oriented assembly of automotive electric motors

The production of motors for the electric vehicles requires innovative and systematic quality control approaches to boost efficiency while moving from low volume towards mass production. In this context, end-of-line quality testing methods are usually applied to assess the product functionality at the end of the process chain. However, this approach does not allow process monitoring and the in-line prevention and correction of defects, leading to significant scrap rates and value losses. This paper presents a new system-level strategy for the in-line quality-oriented assembly of rotors in the production of automotive electric drives. The new strategy is based on a new cyber-physical system that optimizes the assembly strategy depending on the quality of magnetized stacks, monitored with data gathered by in-line inspection. For each batch, the magnetic stacks to be assembled and their orientation is selected according to an optimization algorithm, aiming at minimizing the deviation from the target total integral magnetic flux and maximizing the field uniformity in the magnetized rotor. The impact of the proposed strategy on the quality and productivity related performance measures are predicted by analytical methods. Experimental results based on an industrial case study are reported, showing that the application of the proposed strategy yields a significant increase in the production rate of conforming engines. The proposed approach paves the way to innovative zero-defect manufacturing strategies at system level in emerging, high-tech, manufacturing sectors