Production Engineering

The seizure resistance in ironing of ferritic stainless steel drawn cups using a die having lubricant pockets was improved by roughening the sidewall of the cups. The effect of the surface roughness of the cup on the seizure resistance in ironing was investigated. The seizure resistance using the die having lubricant pockets was higher than that of a polished die, and was heightened by the surface roughness of the cup in the axial direction. To increase the surface roughness of the cup, deep drawing processes with a large clearance and a two-stage deep drawing process were developed. The ironing limits for the roughened cups by the two deep drawing processes were higher than that of the conventionally drawn cup. The thickness of the remaining lubricant film in the sidewall of the ironed cup increased with increasing surface roughness of the cup. It was found that the seizure resistance in ironing was improved by roughening the sidewall of the cup.

Scheduling problems have been studied extensively over the years. Broad ranges of focus areas exist, from optimization to heuristics, production planning to production sequencing, customized algorithms to general-purpose algorithms, and from simple machines to complex environments. In this research, a heuristic approach has been proposed to overcome the scheduling problem on a complex job shop found at a manufacturer of commercial building products. The research is aimed at sequencing production orders in near-real-time, primarily to minimize total tardiness, but also to reduce total setup time. A layered Shifting Bottleneck Procedure is employed, with the top layer determining release dates and due dates for individual jobs, and the bottom layer applying algorithms to individual work centers. The outcome of this research is a better production schedule than current methods with minimal computation cost. The proposed framework performs well and could be applied to other production areas.

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.

A significant driver in research activities of manufacturers and university institutions is the improvement of tool life for cutting tools. Recent publications have shown that the substrate pre-treatment prior to coating as well as defined rounding of cutting edges are key factors for cutting tool life. Different technologies are used for substrate pre-treatment, depending on the machining task, flexibility of the process and economic aspects. However regarding the surface quality two opposing requirements come into conflict. While high surface quality supports the chip removal during machining, the film adhesion between substrate and coating is greater on rough surfaces. This paper presents a comparison of the abrasive flow machining (AFM) and laser ablation technologies as pre-treatment processes for cemented carbides. With respect to the relevant processing parameters, the effects of a pre-treatment using AFM and laser ablation on roughness, surface topography, mechanical activation and chemical composition have been determined.

Inkjet printing represents a disruptive additive manufacturing technology that has emerged as an innovative approach to generate customized lithium-ion batteries by tailored dispersions. However, electrode dispersions cause a complex non-Newtonian behavior which hampers the processability. This paper demonstrates a novel procedure for an a priori evaluation of the printability of aqueous graphite dispersions. Therefore, dispersions with a varying active material content were prepared and the printability was examined through a characterization of the drop formation and the drop deposition behavior. While the drop formation was observed by in-situ monitoring, the drop deposition was analyzed in ex-situ test setups. The rheological properties were systematically determined to calculate nondimensional numbers that describe the dispensing behavior. Consequently, their capability to predict the stability of the drop formation was evaluated. The results revealed that a graphite dispersion with a content of 2 m% allowed for a stable drop formation. No splashing occurred on the substrate during the drop deposition and sufficient wetting can be assumed due to a contact angle of below 90 $$^\circ$$ . Conclusions were drawn to further enhance the active material content. Due to the universality of the proposed approach, it is expected to be applicable to different dispersion systems.

Remote laser beam welding and cutting can be applied to a wide range of applications within the manufacturing technology domain. With high process rates, consistent high quality welding seams and cutting edges at various contours these technologies offer an increased flexibility to process a wide variety of work pieces. To take advantage of the process the laser beam must be positioned precisely on the work piece. Programming a system of an industrial robot combined with a laser beam deflecting scanner manually is a very time consuming job. Programming any “on the fly” movements, a synchronously movement of the scanner and the robot, is even more difficult. This paper describes challenges and a concept for the automated programming of the two devices to apply the advantages of remote laser beam welding and cutting.

This paper presents an approach combining additive manufacturing (AM) with carbon fiber reinforced polymers (CFRP) in an autoclave prepreg process for the development of complex-shaped hybrid AM-CFRP structures with the potential for individualization. The goal of this paper is to investigate the processing route in the context of low volume industrial applications and to assess the mechanical performance of hybrid AM-CFRP structures in ultimate strength and fatigue. The approach was applied to lower-limb prostheses using dissolvable in-autoclave tooling made of ST-130 by fused deposition modeling, two load introduction elements made of titanium by selective laser melting, and pre-impregnated carbon fiber reinforcements. The parts were cured in an autoclave at a pressure of 3 bar and a temperature of 110 °C. The inner toolings were dissolved in a basic solution after curing. The prostheses were subjected to ultimate strength and fatigue tests to assess the mechanical performance of the structures. Results show that the target load of 5474 N was exceeded by 40% and that no fatigue failure occurred for the given loading. Weight savings of 28% compared to a state-of-the-art aluminum reference part were achieved. Results demonstrate that the combination of technologies could be appropriate for high-performance lightweight components with complex geometries.