Höchste Präzision in kurzer Taktzeit

Highest precision in short cycle time – highly sensitive thin fiim strain gauges produced in an industrial high‐rate‐sputtering system Commonly, sputtered strain gauges are already used for highly precise pressure sensors. By using special highly sensitive piezoresistive nanocomposites consisting of metal nanoparticles embedded in an insulating matrix made from diamond‐like carbon (DLC) the sensitivity to strain can be significantly increased. Essential parameters for the characterization of the thin films used as sensor layer are the strain sensitivity (described by the gauge factor) and the temperature coefficient of resistance (TCR). Conventionally used NiCr alloys have a gauge factor of approximately 2. By using metal‐DLC nanocomposite films a factor 5 to 10 higher strain sensitivity in combination with a TCR close to zero was reached on laboratory scale. At first, the highly sensitive films were produced by static deposition using a box coater which led to quite long process times. By using a dynamic deposition process in the same machine the throughput of samples was slightly increased. But for using these highly sensitive films on industrial scale much higher cost and process efficiency is necessary. Hence, the process was transferred to a highrate sputtering system. A 20 times higher throughput of samples was reached in combination with a higher strain sensitivity compared to the dynamic process in the box coater. The used high‐rate sputtering system is also commercially available with enlarged process chambers which enables for a further up‐scaling for efficiently industrial production.     

Herstellung von Präzisionsschichten mittels Ionenstrahlsputtern

Precise thin film synthesis by ion beam sputter deposition Ion beam sputter deposition (IBSD) is a promising technique for the fabrication of high performance thin films because of the well defined and adjustable particle energies, which are rather high in comparison to other PVD techniques. Recent developments concerning long‐term stability and lateral uniformity of the ion beam sources strengthen the position of the IBSD technique in the field of precise thin film synthesis. Furthermore, IBSD offers a more independent choice of relevant deposition parameters like particle energy and flux, process gas pressure and deposition rate. In this paper we present our currently installed large area IBSD facility “IonSys 1600”, which was developed by Fraunhofer IWS Dresden and Roth & Rau company (Hohenstein‐Ernstthal). Substrate sizes of up to 200 mm (circular) or up to 500 mm length (rectangular) can be coated and multilayer stacks with up to six different materials are possible. Tailored 1‐ or 2‐dimensional film thickness distributions with deviations of < 0.1 % can be fabricated by a relative linear motion of the substrate holder above an aperture. In order to demonstrate the advantages of the IBSD technique especially for sophisticated materials and films with high requirements concerning purity, chemical composition or growth structure, several examples of deposited multilayers for various applications are presented.     

Lebensdauerabschätzung an Kunststoffrohren mittels Zeitstand‐Innendruckversuch

Lifetime Prediction of Plastic Pipes by means of Internal Pressure Creep Test The Lifetime Prediction of plastic pipes is based, according to the current set of relevant technical regulations, mainly on the Internal Creep Rupture Test. In this examination, the test for the pipes performed in an accelerated mode with a defined internal pressure and at increased temperatures. In compliance with the applicable Arrhenius rate law, an extrapolation of the measured values then takes place.     

PVD‐Schutzschichten für Werkzeuge des Präzisionsblankpressens

PVD protective coatings for precision molding tools Precision glass molding (PGM) is a replicative hot forming process for the production of complex optical components, such as aspherical lenses for digital and mobile phone cameras or optical elements for laser systems. The efficiency and thus also the profitability of the PGM depend on the unit price per pressed component, which correlates primarily with the service lifetime of the pressing tools. To increase tool lifetime, the tool surfaces are coated with protective coatings based on precious metals or carbon using physical vapour deposition (PVD). The PVD coating technology enables the deposition of thin coatings, which also follow more complex surface geometries and achieve a high surface quality. PVD coatings are also commonly used to protect tools from wear and corrosion. This paper presents two chromium‐based nitride hard coatings produced by an industrial PVD unit and investigated for their applicability for PGM. Two different coating architectures were implemented, on the one hand a single coating chromium aluminium nitride (Cr,Al)N coating and on the other hand a nanolaminar CrN/AlN coating with alternating layers of chromium nitride and aluminium nitride. The latter is a coating consisting of hundreds of nano‐layers, only a few nanometers thick. Both coatings, (Cr,Al)N and CrN/AlN, each have a thickness of s ～ 300 nm in order to follow the tool contour as closely as possible. The properties of the coating systems, which are of particular relevance for PGM, are considered. These include on the one hand the adhesion of glass, the roughness and topography of the surface and the adhesion between the coating and the tool material. In addition, the barrier effect of the coatings against diffusion of oxygen was investigated. In order to reproduce the thermal boundary conditions of the PGM, thermocyclic aging tests are performed and their influence on the different properties is described.     

Verschleißreduzierung an Matrizen für das Präzisionsschmieden von Zahnrädern durch Mehrlagenhartstoffbeschichtung (TiN‐TiCN‐TiC)

Wear reduction on dies for precision forging of gear wheels by means of multi‐layer coating (TiN‐TiCN‐TiC) Due to high thermal, mechanical and tribological loads the tool life quantity of hot forging dies compared to other manufacturing processes is relatively low. Depending on the number of forged parts the mentioned loads lead to different failure causes of the dies. In this connection wear is the main failure cause of hot forging dies. Especially in the precision forging process of gear wheels with its exacting tolerances the tool life quantity is low, which leads to often interruptions of the production process. Because wear concentrates on the near‐surface die areas, these problems can be reduced by increasing the wear resistance of these areas by the Duplex PACVD‐Method, which means nitriding and multi‐layer coating (TiN‐TiCN‐TiC).     

Inline‐Beschichtung von optischen Substraten. Inline coating of optical substrates

Applications of optical technologies like vision care, digital imaging or data communication play a decisive role in our daily life. Manipulation of light is mainly done using optical lenses. Beside mineral lenses, transparent plastic materials become more and more important. The optical and mechanical properties of lenses are crucially improved by high‐quality coatings. These includes primarily anti‐reflective coatings to enhance light transmission, hard coats to improve scratch resistance of the sensitive plastic substrates and finally clean coats to inhibit dusting of the lenses and to ease cleaning. In the following we present modern vacuum coating technologies for industrial refinement of optical substrates. The focal point is set to the coating of plastic eyeglass lenses using a revolutionary inline technology. On one hand the technology merges all coating steps in a fully automated system and enables on the other hand the flexible combination of different layer stacks necessary for RX‐production of ophthalmic lenses. This inline technology is available by the coating system OPTICUS. The design of the OPTICUS is described in the last chapter.     

Rezyklieren von metallischen Spänen mittels Electro‐Discharge Sintering

Composite material Ferro‐Titanit^® is produced powder‐metallurgical by Deutsche Edelstahlwerke GmbH (DEW) and is commonly used for wear and corrosion resistant component parts. Materials properties can be attributed to the microstructure which consists of a corrosion resistant metallic matrix and a huge amount of approx. 50 vol.% of hard Ti‐monocarbides. Although Ferro‐Titanit^® possesses a high amount of hard particles, the material can be machined by turning and drilling in solution annealed condition. Due to the alloying content (Mo, Cr, TiC) of Ferro‐Titanit^®, there is a high motivation to recover those elements by a recycling process of the chips, thus expensive and limited resources can be saved. On idea of a recycling process can be found in the redensification of those chips by electro discharge sintering (EDS). In this work, chips of the material Ferro‐Titanit^® were densified by EDS technique and the resulting microstructure was investigated by optical and scanning electron microscopy. Furthermore, microstructure and hardness of the EDS densified specimens was discussed with regard to the microstructure of conventionally sintered Ferro‐Titanit^®‐samples in laboratory conditions.     

Holzoberflächenmodifikation mittels Atmosphärendruckplasma

Plasma surface modification of wood and wood‐based materials In this article, plasma technical, analytical and application relevant aspects of the plasma treatment of wood and wood‐based materials are presented. With the help of surface energy determinations and adhesion tests it is shown that the surfaces of wood and wood‐based materials can be changed for specific applications. Surface characteristics, which are application‐technological interesting for a later coating or adhesion, can be specifically generated with the use of air plasma. With surface energy determinations of wood and wood‐based materials, a significantly increased polar part of surface energy could be detected after a plasma treatment. Atomic force microscopy analyses of wood composites show that a plasma treatment with the use of ambient air effects an abrasion and a changed surface roughness. Tensile tests and shear tests of coated or adhered wood‐based materials with a plasma treatment show a clearly increased adherence.     

Präzisionsverschleißmessung an dünnen Schichten als Mittel zur Qualitätssicherung und Schichtcharakterisierung

Unterüberschrift (Übersetzung) Dünne Schichten finden zunehmend Verbreitung in technisch anspruchsvollen Anwendungsgebieten. Die Qualitätssicherung von dünnen Schichten erfordert deshalb hochwertige Prüfverfahren. Das Verfahren sollte zu quantitativen Ergebnissen führen, damit eine objektive Bewertung möglich ist. Am Fraunhofer Institut für Schicht‐ und Oberflächentechnik wurde das Kalottenschliffverfahren (DIN 1071 Teil 2) zu einem Präzisionsverschleißtester für dünne Schichten weiterentwickelt. Diese Methode erlaubt es, aus Werkstoffoberflächen ein definiertes und reproduzierbares Materialvolumen auszureiben. Diese Materialkenngröße (Volumenverschleiß) charakterisiert physikalische und chemische Materialeigenschaften und kann damit zur Qualitätskontrolle und Werkstoffentwicklung herangezogen werden. Der Beitrag zeigt Entwicklungschritte, Ergebnisse und Anwendungen dieser Prüfmethode auf.     

Präventivwartung und Wartungsintervalle von Vakuumpumpen

Preventive Maintenance and Service Intervalls for Vacuum Pumps – Avoidance of Equipment Failure and Production Downtime In the day to day private business certain preventive maintenance work e.g. for cars or motorcycles are necessary to maintain the expected mobility in our work and private life. Preventive maintenance and keeping the service intervals for vacuum pumps in all kind of vacuum systems in the work environment are important tasks for the service personel and the system operators. In this article the author wants to provide an overview with recommendations for preventive maintenance and service/overhaul for the most commonly used vacuum pumps.     

Schichtabscheidung mittels Ionenstrahlzerstäuben

Ion Beam Sputter Deposition – Fundamentals and Application for Tailoring Thin Film Properties Ion beam sputter deposition (IBSD) is a PVD technique, which, in comparison to other PVD techniques, is known to produce thin films with desirable properties, for instance, with improved adhesion, dense film structure, less defects, higher purity, less particle contamination, and better controlled composition. Recent systematic and comprehensive investigations of the fundamentals of the whole IBSD process revealed previously unemployed opportunities for tailoring thin film properties over a wide range. The main process parameters were identified to be the scattering geometry and the ion species, or, to be more precise, the mass of the primary ion relative to the mass of the target particle. By choosing these parameters appropriately, structural, optical or electrical properties, to name but a few, can be adjusted according to the technological requirements. The present contribution aims on illustrating these opportunities by presenting the main fundamentals and selected examples.     

Auslegung keramischer Präzisionsgleitlager mit textiler Verstärkungskomponente

Design of ceramic high‐accuracy bearings containing textile fabrics In order to determine the thermo‐elastic behaviour of slide bearings with a bearing sleeve of textile structured ceramic matrix composites (CMC), a new method for computation of the material properties of the composite material was implemented. Therefore a small cut‐out from the regular fabric structure was discretised with the finite element method (FEM). The woven rowings were thereby regarded as unidirectional long‐fiber‐reinforced composites, for which assured calculation methods are available. Additionally pores can be considered in the model. The computed material properties were examined and used as input data for a further FEM‐Model describing the slide bearing with CMC sleeve. By means of this model the thermo‐elastic behaviour of the bearing is determined. The main problem using CMCs as bearing surface (bearing sleeve) in a steel box are the different thermal coefficients of expansion. During the warm up phase the outline of the bearing surface changes. Applying constructional changes based on the simulation the dissipation loss of the bearing sinks substantially and the bearing is prevented from galling.     

Beschichten,Reparieren und Generieren durch Präzisions‐Auftragschweißen mit Laserstrahlen

Laser beam build‐up welding belongs to the technical group of thermal coating. With a coating thickness between 0.1 and 3 mm it is positioned close to PTA and TIG cladding. The special features consist in the excellent controllability of the cladding process, high precision of the material deposition, low thermal influence on the workpiece and low base material mixing, the absence of mechanical effects on the melt pool as well as the large number of coating and substrate materials available for the manufacturing process. Currently, the most important application is the repair of complex shaped and expensive components and tools. Examples are wear damaged moulds, metal forming dies, or aircraft engine components, which original properties can be completely restored by accurate and local replacement of the lost material. In the field of surface protection, laser technology offers advanced solutions for the surface modification of light alloys. Components of Ti, Al or Mg alloys can be protected effectively against wear and corrosion by laser cladding, alloying, and hard particle dispersing. Generating of metal Prototypes by CNC controlled Direct Metal Deposition is a further application of the laser technique. Using this method, mould inserts, active parts of tools, or engine components can be generated directly from the 3D CAD data.     

Gesteinbearbeitung mittels dünner Kreissägeblätter

Treatment of stones by means of thin circular saw blades Circular saws and/or abrasive machining of granite or marble blocks takes place in the industry by block circular saws with 40 to 80 circular saw blades on a shaft. Each of these tools with a tool diameter of approx. 1,000 mm produces a kerf of approx. 6.5 mm. By use of a case‐hardened quality for the master sheets the master sheet thickness and the kerf can be reduced approx. 1 mm. Related to the block which can be separated substantial material savings result in the case of sawing of high‐quality raw materials. Because the used tools are to finish very difficulty with conventional, mechanical technologies, the laser technology became develops for stretching and arranging the disk‐shaped tools. The Laser application is a requirement for the automizableness these work procedures.     

Dekontamination von Primärverpackungen mittels Atmosphärendruckplasmen

Decontamination of primary packaging by means of atmospheric plasmas The increasing demand of perishable products in urban areas as well as the globalisation of the markets also rises up the requirements for packaging. The storage life of these products is provided by microbial reduction in food and packaging, which is realized by aseptic filling or diffusion barriers. Furthermore, in pharmaceutical products it is recommended that preserving agents should not be added to avoid allergic reactions. Therefore packaging with low microbial load up to sterility is needed. Sterilization in wet (peracetic acid) or dry (hydrogen peroxide) set ups are currently available and used in the beverage industry. Pharmaceutical and food industry would prefer decontamination methods without hazardous substances. The possibility of plasma to generate antimicrobial effective components such as UV light, charged particles (ions, electrons) and reactive radicals offers an alternative to common decontamination methods. Plasmas can be separated in two main groups, the low‐pressure plasma and the atmospheric pressure plasma which have advantages and disadvantages. However, both are expected to require lower total process times than the current chemical methods. The construction for bottle treatment used in this study is based on microwave‐driven self propagating discharge. A careful design of the plasma source by using simulation tools is necessary to avoid hot spots during the bottle treatment. Minimization of process times before and after the decontamination treatment is necessary for industrial processes. The lock in and lock out of the bottles into the microwave area may be a limitative factor. Therefore the development of a barrier‐free transport system for 200 ml PET bottles was realized in this work. Temperature investigations of the material PET showed a critical temperature range above 60 °C at 4 cycles of 1000 W. After an 1 second plasma treatment a maximal reduction rate of 2 log10 was observed. A longer treatment time of 5 minutes led to an inactivation of 4 to 5 log10 for vegetative bacteria and of 2 to 3 log10 for Bacillus spores. Moreover an optimization of plasma generation inside the bottles may increase the microbiological inactivation. An optimization of the antimicrobial efficiency is necessary and detailed investigations of inactivation mechanisms of atmospheric pressure plasma should follow.