26 research outputs found
Development and Production of Artificial Test Swarf to Examine Wear Behavior of Running Engine Components - Geometrically Derived Designs
Subtractive manufacturing processes are usually accompanied by the occurrence of tiny
flakes and swarf, which later on cause severe wear and damage, especially in moving components
such as rolling or sliding bearings, pistons, etc. However, up until now, such detrimental effects
have hardly been investigated. One reason is the lack of a definition of a typical design of debris
particle. Therefore, the main goal of the project described in this paper was to elaborate a draft that
defines standardized test particles. It had to be evaluated whether test particles could be adequately
reproduced and whether they would reveal significant damage potential. Taking into account future
mass fabrication, Micro Powder Injection Molding (MicroPIM) was chosen as a production method.
Five different 3D designs of geometrically defined test particles were developed. The maximum size
of each design was 1167 mm in green state; however, all samples shrank in size during sintering.
Specially tailored feedstocks containing 42CrMo4 steel powders were used and the related molding,
debinding and sintering procedures were developed. All particle geometries and related mold inserts
were developed using a commercial software routine for the layout of runner systems, gate locations
and ejector positions. The damage potential of the test particles was evaluated based on trials using
journal bearing and shift valve test rigs. Although only a moderate degree of damage potential could
be ascertained up until now, it can be expected that the artificial swarf will enable standardized wear
test procedures to be developed
Toward mass production of microtextured microdevices: linking rapid prototyping with microinjection molding
The possibility of manufacturing textured materials and devices, with surface properties controlled from the design stage, instead of being the result of machining processes
or chemical attacks, is a key factor for the incorporation of advanced functionalities to a wide set of micro and nanosystems. Recently developed high-precision additive manufacturing technologies, together with the use of fractal models linked to computer-aided design tools, allow for a precise definition and control of final surface properties for a wide set of applications, although the production of larger series based on these resources is still an unsolved challenge. However, rapid prototypes, with controlled surface topography, can be used as original masters for obtaining micromold inserts for final large-scale series manufacture of replicas using microinjection molding. In this study, an original procedure is presented, aimed at connecting rapid prototyping with microinjection molding, for the mass production of two different microtextured microsystems, linked to tissue engineering tasks, using different thermoplastics as ultimate materials
Investigation of Feedstock Preparation for Injection Molding of Oxide–Oxide Ceramic Composites
In this fundamental work, a series of experiments were performed to define the optimal amount of dispersant and solid content for feedstock with and without ceramic fibers (Nextel 610). Based on these fixed conditions, investigations were carried out to discover the effects of binder system, fiber sizing, and increasing fiber content on mixing and viscosity. In addition, the effects of kneading temperature and time, fiber sizing, and different binder systems on fiber length were investigated using a measuring mixer, high-pressure capillary rheometer, and microscopy. Stearic acid, as a dispersant, modified the particle surface and improved the rheological properties. Moreover, increasing the solid content in the feedstocks led to an exponential growth of final torque and relative viscosity, because of the increasing friction between particles. Paraffin wax (PW)- and polyethylene glycol (PEG)-based feedstocks showed different mixing behaviors and rheological results with increasing fiber, whereas PEG-based feedstocks had higher final torques and kneading energies without fibers, whilst PEG feedstocks displayed lower viscosities. Consequently, during kneading, the amount of fiber has been predominating over fiber length, and the effect of the binder, the kneading temperature, and time did not cause significant changes