Untersuchungen zur externen und internen Belastung bei Pflanzenschutzmittelexponierten im Verlauf von drei Jahren

Ziel der von 1995 bis 1997 durchgeführten Studie war es, die dermale (Pad-Methode, Handabwaschung), die inhalative (Luftproben) und die innere Belastung (Urin-Biomonitoring) von gegenüber Pflanzenschutzmitteln (PSM) exponierten Arbeitern aus Thüringen nach der Pestizidapplikation zu analysieren. Nach analytischer Auswertung der Proben (Dünnschicht- und Gaschromatographie) erfolgte der Vergleich mit tolerierbaren dermalen Expositionen (Dtol) sowie maximalen Arbeitsplatzkonzentrationen (MAK). Bei Beachtung der Arbeitsschutzrichtlinien, Durchführung von Vorsorge-untersuchungen und dem Einsatz von Schutzkleidung ist für den PSM-Exponierten offenbar keine Gefährdung auf Plantagen und im Gewächshaus hinsichtlich der dermalen und inhalativen Belastung zu erwarten

Transfer of Process References between Machine Tools for Online Tool Condition Monitoring

Process and tool condition monitoring systems are a prerequisite for autonomous production. One approach to monitoring individual parts without complex cutting simulations is the transfer of knowledge among similar monitoring scenarios. This paper introduces a novel monitoring method which transfers monitoring limits for process signals between different machine tools. The method calculates monitoring limits statistically from cutting processes carried out on one or more similar machines. The monitoring algorithm aims to detect general process anomalies online. Experiments comprise face‐turning operations at five different lathes, four of which were of the same model. Results include the successful transfer of monitoring limits between machines of the same model for the detection of material anomalies. In comparison to an approach based on dynamic time warping (DTW) and density‐based spatial clustering of applications with noise (DBSCAN), the new method showed fewer false alarms and higher detection rates. However, for the transfer between different models of machines, the successful application of the new method is limited. This is predominantly due to limitations of the employed process component isolation and differences between machine models in terms of signal properties as well as execution speed

Wear curve based online feature assessment for tool condition monitoring

The performance of a process monitoring system is determined by the information available to it. Existing methods for selecting relevant process information (features) work offline with data of faulty processes that is often unavailable or neglect random disturbances. This increases the risk of choosing non-sensitive features. Hence, this paper investigates whether a non-sensitive feature is detectable online in an initial selection of features presumed to be sensitive. A method for quantifying and assessing trends in features online is described. In the validation with turning and drilling processes, a single non-sensitive feature was detected successfully in seven out of eight test cases. © 2020 The Authors

Identical NC-code on Different Machine Tools - Similarities and Differences in Timing and Positioning

Process and tool condition monitoring systems are a prerequisite for autonomous production. For online monitoring, it is the state of the art to use reference signals of correct processes to improve failure sensitivity and reduce false alarms. Transferring these reference signals from other machines economizes on teach-in processes and complex simulations. However, the varying behaviour of the two machines leads to differences that need to be considered for the transfer. This work aims to identify similarities and differences in the timing and positioning of multiple machines when executing identical machining instructions. A comparison of process signals quantifies similarities and differences among machines. Results describe differences between process sequences, rapid traverse speeds, rapid traverse paths, machining feed speeds, machining feed paths, tool engagement time, and the temporal alignment of signals. Differences primarily originated from different control parameters and strategies as well as physical drive limitations. During machining differences occurred most frequently when axes were accelerated. Differences accumulated over prolong periods of machining and eventually became relevant from the perspective of online monitoring

Influence of different Ni coatings on the long-term behavior of ultrasonic welded EN AW 1370 cable/EN CW 004A arrestor dissimilar joints

The increasing demand for energy-efficient vehicles requires suitable methods for cost and weight reduction. This can be achieved by the replacement of copper by aluminum, in particular for the on-board power systems. However, the complete substitution is restricted by the mechanical and physical material properties of aluminum as well as challenges in the aluminum copper interface. The challenges concern the corrosion vulnerability and the occurrence of brittle intermetallic compounds (IMC) which can negatively influence the mechanical properties and the electrical conductivity. Therefore, current investigations focus on the one hand on the realization of dissimilar aluminum copper joints by suitable joining technologies, like ultrasonic welding, and on the other hand on the assurance of a sufficient prevention against harmful corrosion effects. In cases where the joint cannot be protected against corrosion by sealing, nickel coatings can be used to protect the joint. In the present study, the influence of electroless, electroplated, and sulfamate nickel coatings was investigated regarding the long-term stability. The joints were performed as industry-related arrester connections, consisting of EN AW 1370 cables and EN CW 004A terminals. The samples were exposed to corrosive as well as electrical, thermal, and mechanical stress tests according to current standards and regulations

Artificial Wear for the Assessment of Monitoring Performance

Various tool condition monitoring systems exist, that can increase machine availability and process reliability. Assessing and comparing their performance, however, requires high expenditure due to real process failures being scarce, too different or costly to reproduce. Hence, this paper investigates the reproducible simulation of flank wear. It introduces and validates a geometry for indexable inserts that results in process changes similar to those caused by natural flank wear. The validation considers turning processes with different feeds, depth of cut and cutting speeds in steel. Results demonstrate that the proposed geometry for indexable inserts affects process forces similar to natural flank wear

FE-Simulation Based Design of Wear-Optimized Cutting Edge Roundings

The performance of cutting tools can be significantly enhanced by matching the cutting edge rounding to the process and material properties. However, the conventional cutting edge rounding design is characterized by a significant number of experimental machining studies, which involve considerable cost, time, and resources. In this study, a novel approach to cutting edge rounding design using FEM-based chip formation simulations is presented. Based on a parameterized simulation model, tool temperatures, stresses and relative velocities can be calculated as a function of tool microgeometry. It can be shown that the external tool loads can be simulated with high agreement. With the help of these loads and the use of wear models, the resulting tool wear and the optimum cutting edge rounding can be determined. The final experimental investigations show a qualitatively high agreement to the simulation, which will enable a reduced effort design of the cutting edge in the future

Modeling of stresses at the cutting wedge in the interrupted cut for the design of the cutting edge microgeometry

The wear behaviour of cutting tools can be significantly improved by a load-optimized design of the cutting edge microgeometry. Thereby, the knowledge of local mechanical stresses is necessary. The experimental-based modelling of mechanical stresses in the continuous cut was already investigated in previous work. In this paper, this method is adapted to the interrupted cut by considering contact lengths, process forces and process temperatures during tool entry and exit. The identified mechanical stresses and temperatures are used for a tool material specific cutting edge microgeometry design

Approaches to tailor the cooling supply to the grinding process

This study presents original research of the investigation of the coolant supply to the contact area with two different approaches. The cooling and lubrication are key aspects of manufacturing processes such as grinding to achieve a high surface quality at high productivity. The coolant supply to the contact area has a high impact on the performance of the coolant. This paper presents the results from two approaches to tailoring the coolant supply for conventional and high-performance processes. An analytical approach is established to determine the coolant outlet velocity. Afterward, a sensor is developed to measure the coolant velocity at the nozzle. Conclusively, the influence of the coolant velocity on the volume flow through the contact zone is investigated. The results of this study highlight the importance of coolant outlet velocities of at least 60% of the cutting speed. The two approaches outline low impact possibilities to ensure optimal coolant outlet velocities and thus low thermal loads during the grinding process

Modeling of cutting forces in trochoidal milling with respect to wear-dependent topographic changes

The aerospace industry utilizes nickel-based super-alloys due to its high level of strength and corrosion resistance. To evaluate milling strategies regarding tool wear, the prediction of forces during these cutting operations is essential. This comprises the determination of the undeformed chip thickness. Due to the complex interdependencies of tool engagements, the determination of these thicknesses is challenging. A geometric physically-based simulation system was extended by a novel time-discrete envelope model to increase the precision of the calculated undeformed chip thicknesses. In order to take tool wear into account, digitized topographies of cutting inserts in different states of tool wear were modelled