Efficiency Deficits and Solution Principles of Requirements Management for Hairpin Stator Production Ramp-up by Early Prototypes

Today the automotive market is at a turning point, where the transition from combustion engines to electric drives has become inevitable. The increasing demand for the electric vehicles is leading to an increased demand in electric drive production systems. The disruptive hairpin technology is one solution to meet the rising demand that uses solid copper bars instead of flexible round wires for the stator. This provides advantages of high fill factors and thus improved product efficiency. However, current hairpin productions face major inefficiencies in the ramp-up phase. In the first part of this paper the efficiency deficits of the industrialization process, that lead to negative effects on the later production ramp-up are analyzed and the inherent root causes to the requirements management and process development are traced. It is presented that especially missing requirements, which specify interdependency-related quality aspects, inline quality gates and interlinking concepts are the major causes for the current deficits. To overcome these root causes, it is necessary to identify the unknown requirements that are crucial for ramp-up. Construction of production equipment prototypes is one method to obtain such required information in advance. However, due to high costs and long lead times, it is not possible to construct and modify a high number of production equipment prototypes. In the second part of this paper a structured methodology for selecting the most critical (sub-)processes of the hairpin stator production to be prototyped is presented. Additionally, the priority sequence of these processes based on the previous requirements management analysis is presented.