Thermoplastic high performance composite gears

This paper describes the development and testing of gears based on polyetheretherketone (PEEK) and endless carbon fibers. Behind these results is a research project funded by INNOSUISSE with the aim of developing plastic gears with which much higher strengths than previously available gears can be achieved. In principle, two types of gearwheels are investigated which differ in their manufacturing method: icotec’s injection molding CFM (Composite flow moulding) process and milled gears (GP) made of composite plate materials. The wheels produced in the CFM process have very good static strength. However, the expected performance in the running tests could not be achieved due to insufficient dimensional accuracy from the CFM process. Comparative tests with GP gears were able to confirm the expected service life. For example, the tests with a line load of 60 N/mm were terminated after approximately 106 load cycles, since the wear was limited to the run-in amount and no failure was to be expected. During dry running tests in a range of 105-106 cycles a load > 129 N/mm was run

BICAR : urban light electric vehicle

This paper describes the technical features of the light electric vehicle (L2e-category) named BICAR. This specially designed vehicle is an all-in-one emissions-free micro-mobility solution providing a cost-effective and sustainable mobility system while supporting the transition towards a low carbon society (smart and sustainable city concept). The BICAR represents part of a multimodal system, complementing public transport with comfort and safety, relieving inner-city congestion and solving the “first and last mile” issue. The BICAR is the lightest and smallest three-wheel vehicle with weather protection. Due to the space-saving design, six to nine BICARS will fit into a single standard parking space. Safety is increased by an elevated driving position and a tilting mechanism when cornering. The BICAR achieves a range of 40–60 km depending on the battery package configuration in urban transport at a speed of 45 km/h. It features a luggage storage place and exchangeable, rechargeable batteries. The BICAR can be driven without a helmet thanks to the safety belt system, which is engineered for street approved tests. The BICAR has an integrated telematic box connected to the vehicle electronics and communicating with the dedicated mobile application, through which the BICAR can be geo-localised, reserved, locked/unlocked and remotely maintained

Laser powder bed fusion of 30CrNiMo8 steel for quenching and tempering : examination of the processability and mechanical properties

The layer-by-layer principle of additive manufacturing technology laser powder bed fusion (LPBF) opens up completely new possibilities in the design and manufacturing of lightweight and efficient gear components. For example, integration of contour conform cooling and lubrication channels into gear components can increase their service life and reduce lubricant consumption. Steels for quenching and tempering and case hardening steels are commonly used materials for gear components. However, the availability of these alloys for LPBF processing is still limited. In particular, the 30CrNiMo8 steel for quenching and tempering is frequently used for gear wheels. This specific alloy is largely unknown regarding LPBF processing and remains challenging, because of its susceptibility to cracking and the high temperature gradients that occur during the LPBF process. Therefore, this study focuses on the LPBF processing of 30CrNiMo8 powder material including process parameter evaluation and material characterization. Additionally, effects of the heat treatment on the resulting microstructure and mechanical properties were investigated. Within this study the 30CrNiMo8 has been processed successfully with a density of well above 99.5% leading to promising mechanical properties. A more homogenous microstructure has been achieved with quenching and tempering, compared to the as-build state

Increasing the safety against scuffing of additive manufactured gear wheels by internal cooling channels

Erworben im Rahmen der Schweizer Nationallizenzen (http://www.nationallizenzen.ch)The layer-by-layer principle of the additive manufacturing (AM) technology of Laser-Powder-Bed-Fusion (LPBF) creates new opportunities in the design and manufacturing of efficient gear components. For example, integrating a cooling system can increase the safety against scuffing or reduce the amount of required lubrication and thus the splashing losses. Quenched and tempered steels or case-hardened steels are commonly used in the fabrication of gear components. However, the availability of these alloys for LPBF processing is still limited. The development of suitable LPBF metal gears (with a Gear Research Centre (FZG) type A geometry) out of quenched and tempered 30CrNiMo8 steel with internal cooling channels shows the possibility of significantly increasing the safety factor against scuffing. This work includes the development of a suitable cooling strategy, material development, the setup of a suitable test infrastructure and the analysis of the LPBF gears tested for scuffing

Development of a fast operating brake and clutch for linear movements to prevent overload in machine tools

Große Kollisionskräfte aufgrund eines Bedien- oder Programmierfehlers sind ein zentrales Problem bei der modernen Produktion mit hocheffizienten Werkzeugmaschinen. Dadurch entstehen teure Reparaturen vor allem an der Hauptspindel und den Spindelmutter-Antrieben, was zu langen Ausfallzeiten an der betroffenen Maschine führt. Eine Umfrage bei insgesamt 23 Anwendern und Herstellern von Werkzeugmaschinen ergab, dass die Service- und Ersatzteilkosten durch eine heftige Kollision bis zu 23.000 € betragen können. Verfügbare Überlastsicherungssysteme können derzeit weder die hohen Kollisionsschäden verhindern noch die Auswirkungen eines Schadens gering halten. Es bedarf also neuer Ansätze. Um dies zu ändern, wird eine Lösung verfolgt, die vorsieht, die Vorteile elektronischer und mechanischer Überlastsicherungssysteme zu vereinen. Diese Lösung basiert darauf, dass der erste Kontakt bei einer Kollision beispielsweise zwischen Werkzeug und Werkstück erkannt und über eine nachgeschaltete Entscheidungslogik verarbeitet wird. Durch diesen kontakterkennungsbasierten Ansatz ist es möglich, Kollisionen schneller als bei herkömmlichen Schutzsystemen zu erkennen und Maßnahmen einleiten zu können. Je nach Kollisionshärte muss die Maschine dann möglichst schnell gestoppt werden, wobei abhängig von der Vorschubgeschwindigkeit zwei Strategien zur Verfügung stehen. Im Bereich niedriger Vorschübe kann mittels eines steuerungsinternen Notstopps die Maschine sicher gestoppt werden, ohne dass nennenswerte Schäden auftreten. Im Fall einer Kollision mit höheren Vorschubgeschwindigkeiten reicht der interne Notstopp nicht mehr aus, weshalb die Steuerung ein Signal an eine aktiv geschaltete Sicherheitskupplung/-bremse weitergibt. Das schnell schaltende Bremssystem kann vor allem den Spindelkasten inkl. Hauptspindel schützen, indem die Überlast vom Bremssystem aufgenommen wird und bleibende Verformungen verhindert werden. Dazu muss das Bremssystem mit hoher Kraft schnellstmöglich wirken. Eine Überlastkupplung, die eine hohe Axialsteifigkeit aufweist und direkt an der Schnittstelle zwischen Antriebssystem und Werkzeugschlitten in die Spindelmutter integriert ist, kann den Kraftfluss infolge einer Kollision früh unterbrechen und somit das Antriebssystem schützen. Solche Maschinenelemente zur schnellen Kopplung bzw. Entkopplung von großen Kräften sind nach dem derzeitigen Stand der Technik und Forschung nicht verfügbar. Ziel dieser Arbeit ist somit die Entwicklung einer schnell schaltenden Bremse und Kupplung für Linearbewegungen am Beispiel des beschriebenen Überlastsicherungssystems für Werkzeugmaschinen mit Spindelmutter-Antrieben. Damit erfolgt eine Eingrenzung des Lösungsansatzes auf die mechanischen Komponenten. Die ebenfalls benötigte Steuerungstechnik zur Auslösung von Bremse bzw. Kupplung wird in einer weiteren Arbeit am Werkzeugmaschinenlabor der RWTH Aachen entwickelt. Die Hauptanforderung an die einzelnen Systeme besteht dabei in der Verkürzung der Reaktionszeit. Maßnahmen zur Vermeidung von schwerwiegenden Beschädigungen infolge Kollisionen müssen in den ersten Millisekunden eingeleitet werden. In der vorliegenden Arbeit wird zur Lösung dieser Aufgabe als Vorgehensweise der Produktentwicklungsprozess gemäß VDI2221 gewählt. Dabei wird gezeigt, dass die Anforderungen durch eine hydraulische Betätigung des Brems- bzw. Kupplungssystems erreichbar sind. Das Herzstück bildet daher ein Hydraulikventil, das durch einen extrem schnellen Aktor geöffnet wird. Das zentrale Problem dabei ist die Optimierung der Parameter Kraft, Weg und Zeit. So müssen die eingesetzten Aktorprinzipien hohe Kräfte und Wege innerhalb kürzester Reaktionszeit aufbringen. Das schnell schaltende Bremse-Kupplung-System wird hier exemplarisch für die x-Achse einer Fräsmaschine in Fahrständerbauweise entwickelt. Die Antriebssysteme bestehen dabei aus Kugelgewindetrieben. Es steht jedoch nicht die Werkzeugmaschine im Vordergrund, sondern die Entwicklung des Bremse-Kupplung-Systems, das somit auch in weiteren Anwendungsfeldern ihren Einsatz finden kann. Für die geforderte Aufgabenstellung leiten sich jedoch aus den Eigenschaften von Werkzeugmaschinen wie z. B. Verfahrgeschwindigkeiten, Steifigkeiten etc. verschiedene Anforderungen ab, welche die Basis für die vorliegende Arbeit darstellen.The requirements regarding productivity and quality of highly efficient machine tools are rising continuously. A reliable process safety, along with high machining speeds and accuracy, is an essential property. Thus, collisions between moving and non-moving objects in the workspace are a critical problem. These collisions generally lead to high repair costs up to 23.000 € and long downtimes. Damages of the machine components, such as main spindle and spindle-nut drive-system, are the consequences. A telephone survey with different users and machine tool manufacturers was conducted in summer of 2005 by the Laboratory of Machine Tools and Production Engineering (WZL), RWTH Aachen, and the Institute for Engineering Design and Industrial Design (IKTD), University of Stuttgart. The objective of this survey was to find out the most common reasons for collisions in machine tools. Possible causes mentioned most frequently by the user or the programmer were handling errors, both for hard and for soft collisions. Among these errors, the definition of the zero shift turned out to be the most common source for hard collisions. Powerful influences on the collision forces are the rigidity in the collision point and the feed. An increase in both results in an extreme amplification of the collision force on all relevant components. Available overload fallback systems based on electric and mechanical components are presently too slow to avoid damages. A collision experiment points out that a hard collision has to be detected during the first milliseconds of impact. Taking into consideration the high masses and the inertia of today’s machine tools, an emergency stop may not avoid further damages if it is initiated more than five milliseconds after the first collision contact. To avoid, or at least minimise collision damages, a new approach was analysed which is based on the detection of the first contact at the beginning of a collision. A contact sensor detects the first touch between the tool and another component of the machine. The decision logic immediately receives a signal and analyzes the contact situation with regard to the actual machining situation. If the contact initiates a collision, the machine tool has to be stopped by an internal NC emergency stop. If the current feed rate is too high, so that the internal NC emergency stop cannot prevent damages to the machine components, in particular to the spindle nut, the rotating parts are uncoupled by an electronically activated safety-clutch. Simultaneously, an external brake system decelerates the linear axes. To protect the headstock, including the main spindle, the fast switching brake system absorbs the overload and avoids ductile deformations. To achieve this, the brake system reacts as fast as possible with a high braking force. The overload safety clutch, which applies a high axial rigidity, is integrated in the spindle nut. This setup protects the complete drive system. Suitable components for fast coupling or decoupling of high forces are not available on the market so far. This research outlines the development of this fast switching brake-clutch-system for spindle-nut drives. The numeric control, which is also required to actuate the brake-clutch-system, was developed by the WZL institute. The product development process indicated that a hydraulic system best meets the requirements to avoid damages to the machine tool. The brake system is hydraulically ventilated and based on the well-known friction-locked connection by a reinforcement with wedges. The principle of the clutch is based on a collet which is hydraulically pressed on a counter shell. Thus, the inside diameter of the collet is reduced and a frictional force is induced between the collet and the counter shell. The counter shell is connected with the spindle nut to protect the high-quality running characteristics of the spindle nut balls from the radial forces of the collet. The collet is flanged directly to the centre support. By discharging the hydraulic pressure, the friction is eliminated and the components are decoupled. The main component to trigger the brake-clutch-system is a hydraulically seated valve, opened by a very fast actuator. The main challenge is the optimisation of the actuating force, the adjustment travel and the manipulation time. Contrary to available valves, the presented actuating elements have to switch without feedback control. To achieve this, the operating unit uses an energy storage which is released by a fast activating actuator principle based on piezoactuators

BICAR : neue Dimensionen urbaner Mobilität für die Stadt Winterthur

RECURSOS HUMANOS IMPACTO DEL TELETRABAJO REQUERIMIENTOS DEL TELETRABAJO RESULTADOS TIPOS DE SERVICIOS QUE PUEDEN LLEVARSE A CABO DESDE EL TELETRABAJO IMPACTO DEL TELETRABAJO DISCUSIÓ