Riemer, Oltmann
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Item-typ:Veröffentlichung, Thermo-mechanical tool setting mechanism for ultra-precision milling with multiple cutting edges(2019-01); Ultra-precision milling operations are particularly ineffective machining processes, due to the fact that they are typically operated with a singular cutting edge (fly-cutting). For meeting the tight tolerances of optical and high precision surfaces, a nanometer precision tool setting mechanism is mandatory when adding more cutting edges. On the basis of a theoretical assessment of the surface generation, this paper presents a novel tool setting mechanism based on a thermo-mechanical actuator that has specific advantages compared to electrical or mechanical solutions. The prototype design for a two-tool holder for diamond milling using this actuator is presented and the choice of substrate material is assessed by FEM simulations. It was found that 1.2083 type steel potentially offers a larger stroke and therefore was chosen for the prototype. Next, the requirements for the heat input are discussed and a novel device for quasi-continuous heating during spindle rotation—an IR-LED ring light—is presented. Using the ring light, it is demonstrated that the tool holder can be selectively heated and a localized expansion of up to 1 μm is achievable at a spindle speed of 240 min-1.Wissenschaftlicher ArtikelBand:5580 57 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Development and application of a test rig for tribological investigations under impact loadsThe investigation and the understanding of frictional mechanisms occurring between forming dies and work pieces in tribological contact is the prerequisite for the development of novel, dry bulk metal forming processes such as dry rotary swaging. The capability to conduct tribological investigations within the actual forming processes, however, is strongly limited, e.g. due to the limited accessibility of force measurement equipment. This work presents the development and application of a tribological test rig mimicking typical contact geometries and high impact loads associated with infeed rotary swaging for process-independent tribological investigations. The development comprises the designing process based on rotary swaging process simulations, setup assembly, and calibration procedure. Subsequently, the functionality of the test rig was demonstrated successfully, determining the distinct frictional properties under lubricated and dry conditions of various samples with structured surfaces representative for rotary swaging dies.Wissenschaftlicher ArtikelBand:19118 88 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, An analytical multilayer source stress approach for the modelling of material modifications in machiningIn the research concept of Process Signatures machining induced changes of surface and sub-surface material properties are considered as material modifications caused by the physical conditions the material is exposed to during the process. This paper presents a newly developed multilayer source stress model to analytically describe the material modifications caused by the machining process in multiple passes. The analytical model that needs measured shape deviations as input is validated via finite element simulations. The approach incorporates the effects of machining induced source stresses and the contribution of residual stresses present in the workpiece before machining. Results from milling experiments show a pronounced correlation between the identified workpiece material modifications and the width of cut.Wissenschaftlicher ArtikelBand:66Heft:193 85 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Potentials of Dry Rotary SwagingInfeed rotary swaging is an appropriate cold massive forging technology for the manufacture of cylindrical shaped components made of iron or aluminum base alloys. The process is focused on reducing the cross-section of full profiles or tubes and is e.g. widely used in automotive industry. The design of swaged hollow components can easily be adapted to the external load in such a way, that the wall thickness is partially reduced and the material cross-section is increased where needed. The above-mentioned advantages result in a high potential for light-weight production while the produced components exhibit high geometric accuracy and surface quality. However, an excellent CO2 balance is yet limited due to high demands for lubricants significantly increasing the number of process steps for further component refinement. In order to increase the overall process efficiency, a changeover to a dry process design becomes necessary. A dry processing will cause high die wear and deterioration of workpiece quality. The most important functions of the lubricant have to be substituted by other approaches and strategies. Development and removal of heat, generation and discharge of wear debris and, above all, die wear and the resulting workpiece quality have to be considered. The effective tribological friction conditions have to be adjusted by means of geometric adaptations of the active die surfaces to realize good workpiece qualities at comparable cycle times. This paper gives a review of the state-of-the-art in dry rotary swaging. Extensive experiments in laboratory scale as well as application tests were performed with various die setups. The most important findings regarding wear, wear minimization, process kinematics, workpiece quality, FEM simulation are presented. The overarching goal is to achieve a longterm stability for the successful dry processing.Wissenschaftlicher Artikel738 593