J. Stoll

Criticality analysis of spare parts management: a multi-criteria classification regarding a cross-plant central warehouse strategy

Abstract Today an efficient warehouse and inventory management of spare parts for production machinery is essential for service organizations. Optimal strategies in procurement, stocking and supply play an important role for serviceability in spare parts management. In this context, individual item criticality should be considered, which describes how crucial a spare part is. This paper presents a three-dimensional classification approach for spare parts regarding a cross-plant central warehouse strategy of a service network. The approach uses two dimensions to estimate value and predictability of spare parts with aid of an ABC and XYZ analysis. The third dimension VED analyses a multi-criteria criticality classification and six feasible criteria are identified to describe item criticality. The methodology of the analysis is based on a decision tree, which represents the defined criteria by nodes. In addition, the analytic hierarchy process is used to solve the multi-criteria decision problems at the different nodes of the decision tree. The approach is developed in a research project and evaluation of spare parts is performed based on real inventory and transaction data in cooperation with an industrial company. As a result 15,000 out of 50,000 items could be classified as suitable for central warehousing.

Assessment of lamination stack production

The economic production of automotive electric drives challenges manufacturers and OEMs. In order to support the cost optimal technology choice, a real lamination stack production is assessed with respect to quantity and variant flexibility. Therefore the process chain of a sample product is analyzed from the coil material to the finished stack. The cost interdependencies are analytically modeled in order to calculate the production costs from a bottom-up perspective. The cost calculation is done for a punching as well as a laser-cutting line. Based on this evaluation manufacturing processes can be chosen and volume-flexible series production lines can be designed. Furthermore, the achievable quality is a key aspect in the production of electric drives. The geometric features of the single sheet and the lamination stack, respectively, influence the performance of the electric drive significantly. Therefore, the perspective on suitable evaluation criteria for the process-dependent quality characteristics of the individual components is given in this paper.

Analysis of wear behavior of stamping tools in the production of electrical steel sheets

Rotor and stator stacks consist of laminated electrical steel sheets and represent the essential core components of an electric drive. These sheets are frequently made of non-grain-oriented electrical steel, fully finished, and produced by means of stamping. A cost efficient production requires prolonging tool life by reducing tool wear. Hence, the presented work aims at analyzing wear behavior of stamping tools in the process of stamping electrical steel sheets with baked varnish insulating coating. Based on stamping tests, a series of long-term experiments with initially sharp cutting elements made of hardened tool steel was conducted over a period of several hundred thousand punching strokes. The number of strokes was analyzed with regard to its effects upon defined abrasion parameters at the cutting edges as well as upon burr and cut surface at the produced electrical sheet.

Flexible production lines for series production of automotive electric drives

The economic production of drive components is a major condition for the market success of electric vehicles. To deal with the high number of variants in the automotive industry, market uncertainties and to ensure an economic production, it is necessary to develop flexible production lines which meet the requirements of automotive series production. Based on the development of a production-oriented component design, manufacturing and different measurement methods have to be examined and enabled to readiness. Moreover, simulation-based classification models will be used for the final design of the production lines.

Throughput analysis and simulation-based improvement of baked varnish stacking for automotive electric drives

A critical part in the process chain of manufacturing electric drives is the production of laminated stacks. Due to their excellent isolating characteristics, electrical sheets that are coated with baked varnish are often considered to be electric benchmarks. Besides a pure loss evaluation of the laminated stacks, a cost reduction of the overall system should also be aimed for. This paper deals with the optimization of a real production line and focuses on the process chain: stamping with subsequent baking of single-tooth stator stacks for automotive application. The main focus of the improvement potential lies on the baking process, including the necessary pre- and post-processing. In order to optimize the existing line, the simulation software Tecnomatix Plant Simulation was used. Through bottleneck analyses of the modeled system, targeted improvements were derived to achieve a significant increase of the output. Those simulation studies enable virtual adjustments to the running system and a quantification of the expected effects. In the context of a real example, quantitative improvement potentials are presented and the limitations of the process chain baked varnish stacking are shown.

Technology Selection for Electric Drive Production with a Game Theoretic Approach

To solve the supply chain decision problem of technology selection for electric drive production, the authors chose a game theoretic approach to model and solve the bargaining situation of manufacturer (OEM) and supplier. The OEM can decide between a same part strategy and a differentiating strategy with increasing sales potential as well as higher complexity and production costs. The supplier has to choose a production technology and can decide between a specialized technology (e.g. punching) and a flexible technology (e.g. laser). Using the specialized technology the variable costs per piece are lower but every additional variant causes additional tool investments (e.g. punching dies). The interdependence of a supplier’s choice of production technology and its customer’s decision, regarding the number of different product variants that he wishes to source, is modeled as a non-cooperative game in strategic form. The resulting Nash equilibriums in pure and mixed strategies are determined with respect to the investment costs faced by the supplier, the target market conditions and the cost share passed on to the supplier’s customer.