Werkzeugverhalten und -optimierung beim Einlippenbohren

Die Produktivität und die Qualität beim Einlippenbohren ist von einer Vielzahl von Einflußfaktoren abhängig. Die Einflußfaktoren umfassen dabei die verfahrenspezifischen Maschinenvoraussetzungen, die Verwendung geeigneter Kühlschmierstoffe, die Wahl angepaßter Prozeßparameter, das Werkstückmaterial sowie das statische und dynamische Werkzeugverhalten. Die Stabilität des Zerspanungsprozesses als Voraussetzung einer hohen Prozeßsicherheit ist beim Einlippenbohren aufgrund der hohen Werkzeugnachgiebigkeiten in radialer als auch in axialer Richtung im wesentlichen vom Werkzeugverhalten abhängig. Mit dem folgenden Beitrag sollen erste Untersuchungsergebnisse zur Beeinflussung der Zerspanbarkeit durch das Werkzeugverhalten sowie die Vorgehensweise bei der Ermittlung von statischen und dynamischen Kenngrößen für Einlippenwerkzeuge dargestellt werden

Process integrity of deep hole drilling for small diameters

Process-integrity in deep-hole drilling with solid-tungsten-carbide-drills of 1 and 2 millimeter diameter requires chipremoval in the bead by the internal cutting-fluid supply. The flow rate of the cutting fluid depends on the internal profile and the length of the drill-shaft· The cross-sectional area of the shaft also determines its stiffness and breaking strength. Tool wear increases the cutting forces and thereby also the stressing of the drill. Optimisation of the progress-integrity can be achieved by careful selection of the cutting-parameters

Maschinenkonzepte für die Hochgeschwindigkeitsfräsbearbeitung

Die derzeitige Marktsituation im Maschinen- und Anlagenbau ist dadurch gekennzeichnet, daß sowohl Hersteller als auch Lohnfertiger sich gezwungen sehen, dem steigenden Angebots- und Preisdruck durch Senkung ihrer Produktionskosten Rechnung zu tragen und Wettbewerbsvorteile durch Erhöhung der Flexibilität und Qualität ihrer Fertigung zu erzielen. Bei der mechanischen Bearbeitung bietet der Einsatz der Hochgeschwindigkeitszerspanung ein bislang gering genutztes Potential an Rationalisierungsmöglichkeiten. Durch Erhöhung der Vorschub- und Schnittgeschwindigkeiten um den Faktor 5 bis 10 im Vergleich zur konventionellen Zerspanung wird eine erhebliche Reduzierung der Hauptzeitanteile bei zerspanungsintensiven Fertigungsprozessen erreicht. Die wesentlichen Merkmale einer Fräsbearbeitung mit gesteigerten Schnittgeschwindigkeiten sind die sinkenden Schnittkräfte und die hohen erreichbaren Oberflächenqualitäten. Bei konstantem Vorschub pro Zahn können deutlich größere Vorschubgeschwindigkeiten realisiert werden, mit denen sich hohe Zerspanungsvolumina erzielen lassen. Die Haupteinsatzgebiete der HSC-Bearbeitung liegen in der Komplettbearbeitung von Leichtmetall-Legierungen und Kunststoffen sowie beim Schlichten in der Stahl- und Gußbearbeitung, beispielsweise im Werkzeugbau

Einlippentieflochbohren in Holzkonstruktionen

Die gegenwärtige übliche Bohrtechnik mittels Schlangen- bzw. Wendelbohrern gewährleistet nicht immer die notwendige Bohrungsqualität hinsichtlich der Mittenabweichung. Bohrungsmittenabweichungen von 3,5 mm je 100 mm Bohrungslänge sind durchaus üblich, da das verhältnismäßig biegeweiche Bohrwerkzeug sich den Weg des geringsten Widerstandes sucht und harten Stellen im Holz ausweicht . In Holzkonstruktionen ist es häufig erforderlich, präzise Bohrungen großer Länge einzubringen. Beispielsweise erfolgt die Verbindung von Brettbindern in Groß- und Gesellschaftsbauten mittels eingelassener Knotenbleche. Die Kraftübertragung vom Holzträger auf das Metallknotenblech übernehmen in das Holz eingebrachte Stahldübel, die in entsprechenden Bohrungen des Knotenbleches verankert sind. Mit Hilfe einer Tieflochbohreinrichtung können erstmalig systematische Tiefbohrversuche in Holz durchgeführt werden

Simulating the soil phosphorus dynamics of four long‐term field experiments with a novel phosphorus model

Phosphorus is a nonrenewable resource, which is required for crop growth and to maintain high yields. The soil P cycle is very complex, and new model approaches can lead to a better understanding of those processes and further guide to research gaps. The objective of this study was to present a P-submodel, which has been integrated in the existing Carbon Candy Balance (CCB) model that already comprises a C and N module. The P-module is linked to the C mineralization and the associated C-pools via the C/P ratio of fresh organic material. Besides the organic P cycling, the module implies a plant-available P-pool (Pav), which is in a dynamic equilibrium with the nonavailable P-pool (Pna) that comprises the strongly sorbed and occluded P fraction. The model performance was tested and evaluated on four long-term field experiments with mineral P fertilization, farmyard manure as organic fertilizer and control plots without fertilization. The C dynamics and the Pav dynamics were modelled with overall good results. The relative RMSE for the C was below 10% for all treatments, while the relative RMSE for Pav was below 15% for most treatments. To accommodate for the rather small variety of available P-models, the presented CNP-model is designed for agricultural field sites with a relatively low data input, namely air temperature, precipitation, soil properties, yields and management practices. The CNP-model offers a low entry threshold model approach to predict the C-N and now the P dynamics of agricultural soils.Fachagentur Nachwachsende Rohstoffe http://dx.doi.org/10.13039/501100010812Peer Reviewe

Tissue-specific variation in DNA methylation levels along human chromosome 1

<p>Abstract</p> <p>Background</p> <p>DNA methylation is a major epigenetic modification important for regulating gene expression and suppressing spurious transcription. Most methods to scan the genome in different tissues for differentially methylated sites have focused on the methylation of CpGs in CpG islands, which are concentrations of CpGs often associated with gene promoters.</p> <p>Results</p> <p>Here, we use a methylation profiling strategy that is predominantly responsive to methylation differences outside of CpG islands. The method compares the yield from two samples of size-selected fragments generated by a methylation-sensitive restriction enzyme. We then profile nine different normal tissues from two human donors relative to spleen using a custom array of genomic clones covering the euchromatic portion of human chromosome 1 and representing 8% of the human genome. We observe gross regional differences in methylation states across chromosome 1 between tissues from the same individual, with the most striking differences detected in the comparison of cerebellum and spleen. Profiles of the same tissue from different donors are strikingly similar, as are the profiles of different lobes of the brain. Comparing our results with published gene expression levels, we find that clones exhibiting extreme ratios reflecting low relative methylation are statistically enriched for genes with high expression ratios, and <it>vice versa</it>, in most pairs of tissues examined.</p> <p>Conclusion</p> <p>The varied patterns of methylation differences detected between tissues by our methylation profiling method reinforce the potential functional significance of regional differences in methylation levels outside of CpG islands.</p

Handling the phosphorus paradox in agriculture and natural ecosystems: scarcity, necessity, and burden of P

This special issue of Ambio compiles a series of contributions made at the 8th International Phosphorus Workshop (IPW8), held in September 2016 in Rostock, Germany. The introducing overview article summarizes major published scientific findings in the time period from IPW7 (2015) until recently, including presentations from IPW8. The P issue was subdivided into four themes along the logical sequence of P utilization in production, environmental, and societal systems: (1) Sufficiency and efficiency of P utilization, especially in animal husbandry and crop production; (2) P recycling: technologies and product applications; (3) P fluxes and cycling in the environment; and (4) P governance. The latter two themes had separate sessions for the first time in the International Phosphorus Workshops series; thus, this overview presents a scene-setting rather than an overview of the latest research for these themes. In summary, this paper details new findings in agricultural and environmental P research, which indicate reduced P inputs, improved management options, and provide translations into governance options for a more sustainable P use

Generating the Generator: A User-Driven and Template-Based Approach towards Analog Layout Automation

Various analog design automation attempts have addressed the shortcomings of the still largely manual and, thus, inefficient and risky analog design approach. These methods can roughly be divided into synthesis and procedural generation. An important key aspect has, however, rarely been considered: usability. While synthesis requires sophisticated constraints, procedural generators require expert programmers. Both prevent users from adopting the respective method. Thus, we propose a new approach to automatically create procedural generators in a user-driven way. First, analog generators, which also create symbols and layouts, are utilized during schematic entry to encapsulate common analog building blocks. Second, automatic code creation builds a hierarchical generator for all views with the schematic as input. Third, the approach links the building block generators with the layout through an object-oriented template library that is accessible through generator parameters, allowing the user to control the arrangement. No programming is required to reach this state. We believe that our approach will significantly ease the transition of analog designers to procedural generation. At the same time, the templates allow for a “bridge” to open frameworks and synthesis approaches so that the methodologies can be both better spread and combined. This way, comprehensive frameworks of both synthesis-based and procedural-based analog automation methods can be built in a user-driven way, and designers are enabled to gain early layout insight and ease IP reusability

Template-driven analog layout generators for improved technology independence

Analog generators, especially those used for automatic layout creation, are powerful tools to support the still largely manual analog design flow. The effort for generator development, however, is often found to be a bottleneck. Further, verification of generators is usually based on many cycles of generation, each requiring subsequent verification. This is often expensive in terms of computation effort. Up-to-date generators only allow to detect failures using post-layout checks such as DRC and LVS because they describe the designer’s intent implicitly as a sequence of (layout manipulation) commands which cannot be verified directly. Also, sequential code often prevents the description of interdependent layout structures or forces the programmer to include extra code, which can again cause errors. In order to overcome these issues, we introduce a new approach to implement layout generators. In a first step, the layout is described as an abstract template. A second automatic step checks this template for structural errors and schedules the required procedural commands. As the result, layout generators are more compact, easy-to-read, and errors can be detected by formal checks of the template description. The new approach was applied to two technology nodes, 180 nm and 22 nm

Removal of polymer matrix material of fiber-reinforced plastic by laser

The business unit Microtechnology of the Fraunhofer Institute for Material and Beam Technology IWS works on selective matrix ablation of fiber-reinforced plastic (frp). A process is developed, which realizes a fiber-protecting removal of matrix material by laser. With this pretreatment it is possible to apply a rib like reinforcement structure afterwards on consolidated frp components for instance