Kirsten Tracht

Process Chains in Microforming Technology Using Scaling Effects

Cold formed micro parts with dimensions <1 mm show in some aspects characteristics due to scaling effects that can be positively used in process chains. Whereas aspect ratios in upsetting processes are limited to l0/d0<2 in the macro scale, a laser induced free‐forming process generates droplet shaped pre‐forms for consecutive calibrating processes, i.e. micro rotary swaging. Scale effects on establishing and shortening of process chains like free‐form heading/rotary swaging/heat treatment are discussed. On the other hand a geometric scale‐up approach in the macro range is described to overcome the specific handling problems of miniature parts. This is achieved by leaving the parts in a physical linkage during the processing steps. An effective application of linked micro parts requires intensive modeling and simulation work.

Impact of Parameter Changes in a Service Provider Closed-Loop Supply Chain with Customer-Owned-Stock

Spare part supply for aircraft must be quick and reliable. To reduce costs for spare part supply and aircraft life-cycle costs, broken parts are repaired and put back into stock. Airlines outsource the spare parts provisioning to maintenance, repair, and overhaul providers (MRO) because common spare part pooling saves costs. At their hub, airlines keep one piece of a crucial spare part for immediate replacement of failed parts. Up to now MRO-providers do not take into account the customer-owned stock, when planning their inventory levels. This causes over-stocking at the central warehouse.

Queueing of Seasonally Demanded Spare Parts in a Repair Shop of a Closed-Loop Supply Chain

Spare parts in the aviation industry are repaired after removal from the aircraft and led back to stock, forming a closed-loop supply chain. Typically the demand of spare parts is assumed to follow a homogeneous Poisson distribution. The repair times in the shop with limited capacity are taken to be exponentially distributed. This paper investigates the effects of non-homogeneous demand and the resulting queue in the repair shop due to limited capacity in periods of high demand.

Change Management as an Enabler of Employee Knowledge Integration into the Design of Planning Procedures

The paper presents an approach for the usage of change management as enabler of employee knowledge integration into the design of planning procedures. While most approaches to change management deal with the introduction of predefined procedures, the approach takes the design of these as starting point for the successful change management considering the knowledge, experience and needs of employees. The paper presents a brief overview of change management concepts and the main influencing factors on resistance against change. In the following sections the approach for employee knowledge integration and its components, including a feedback phase of user integration, are introduced.

Effects of Lateral Transshipments in Multi-Echelon Closed-Loop Supply Chains

Spare part supply for machines is realized with multi-echelon closed-loop supply chains, in which spare parts are repaired and led back to stock after removal from a broken machine. Spare parts have to be provided fast for avoiding revenue loss due to Poisson distributed part failures. This requires distribution warehouses, which are located close to the machines and one central warehouse, replenishing the distribution warehouses. If a spare part is requested, the part is supplied by the central warehouse or the distribution warehouse assigned to the requesting location. Emergency transshipments from distribution warehouses that are not assigned to the requesting location, can improve supply chain performance.

STEP product model for micro formed linked parts

A central challenge of micro forming production is the handling of component parts. The simple transformation from macro to micro scale of the forming and handling processes is complicated due to size effects. One solution for overcoming these effects is to handle the components as linked parts as long as possible. Linked parts are manufactured in multistage processes in which every individual process generates different requirements. Therefore, arrangements have to be adopted to administrate growing amounts of data, for the documented coordination of the processes and also for a reproducible production. A practicable method is the development of product data models. Of major importance is the product data modelling based on ISO 10303, also known as Standard for the Exchange of Product Model Data (STEP). STEP offers extensive possibilities for the application-neutral and unambiguous data exchange. Using STEP a basic product data model for the micro forming technology is designed. It is focussing on the modelling of linked parts production.

Controlling and Assisting Manual Assembly Processes by Automated Progress and Gesture Recognition

The digital progress monitoring of manual assembly processes at goods with huge dimensions is a challenging task. The paper presents an approach using 3D-image sensors for gesture control and progress recognition. The developed system is able to avoid time and effort consuming walks of workers between assembly objects and computer terminals. Progress recognition of assembly processes is realized by interpreting the movements of the workers’ hands and by detecting the passing of defined coordinates within the assembly and warehouse areas.

Cost-optimal spare parts inventory planning for wind energy systems

For safe and reliable machine operation, maintenance, repair and overhaul (MRO) activities are required. Spare parts demand forecasting and inventory planning, which is an important part of MRO activities, must be accurate to avoid costs because of surplus spare parts or machine downtimes. The restriction of reduced accessibility to wind turbines during the winter months also has to be taken into account when planning maintenance activities and spare part inventories for wind farms. The presented model provides the most economic stock quantity under given environmental conditions. It is based on the proportional hazards model, which is extended to calculate the remaining useful component life time and derive required spare parts inventory levels. The presented model is validated, using condition monitoring data and environmental data of an onshore wind farm. Comparison of the spare part inventory prediction to wind farm’s failure data proves the model’s accuracy. Parameter analyses show that the model can be applied for spare parts inventory planning under consideration of environmental conditions.

Design and implementation of multiaxial force sensing gripper fingers

This paper focuses on the integration of elementary force sensors into the fingers of parallel grippers. The theory of the approach of integrating three sensor elements into a gripper finger is described and the results of the practical evaluations are given. Strain gauges are used as elementary sensor elements. Two different design approaches are evaluated. The first one uses H-shaped cut-outs to weaken the structure at designated areas. The measurement accuracy of this system is compared with a second approach without cut-outs, which is easier to manufacture. Finite element analysis is used in both approaches to simulate the behaviour and to determine the best locations for strain gauge application. The performances of both design concepts are experimentally evaluated. It can be seen that the results of the finite-element analysis are correct and that a satisfactory decoupling of the basic sensors can be achieved using a physical or mathematical approach. Both prototypes are able to measure the gripping force with sufficient accuracy.

Statistical Study for Micro Forming Technologies Used for Linked Parts Production

Manufacturing and handling of micro parts is a great challenge due to their small dimensions. Manufacturing processes and the state of knowledge in macro technologies are not smoothly transferable to the micro world. This can be justified, for example, by size effects and the related, changed component behaviour. It is assumed that known statistical distributions from macro range are changed, too, concerning to the changed behaviour and changed physical regularities in micro range. For that reason quality criteria for micro cups are described. By means of these selected criteria, parts are judged. Using the findings, statistical distribution models for the simulation of ladder linked parts production are determined.