Tuesday afternoon, 12 October

Chairmen:
Dr Frank Petzoldt, Fraunhofer Institut – IFAM
Professor Lars NyborgChalmers University of Technology

Oral

Injection Moulding for the Production of Micro Components
Piotter, V (Karlsruhe Institute of Technology (KIT), Eggentein-Leopoldshafen, Germany)

The global trend of miniaturization demands enhanced manufacturing processes suitable for both micro devices and economic production. With respect to metal and ceramic products micro powder injection moulding is such an option because it combines large-scale series production with a wide range of materials.
The current state of the art will be illustrated by both industrial and laboratory samples and examples for extremely fine structured parts (< 10µm detail dimensions) will be presented. Furthermore, latest developments on MicroPIM, e.g. the tuning of feedstocks by addition of tailored additives improving the powder/binder relationship will be demonstrated.
The dimensional accuracy of the final sintered parts related to the specific process conditions during injection moudling represents a further important R+D topic. An initial approach with a new test tool enabling variable pressure and temperature profils during shaping will be presented.

Micro Metal Injection Moulding by NIL Lost Form Technology and Using Nanopowder
Nishiyabu, K (KINKI UNIVERISTY, Osaka, Japan)

This study aims to develop the manufacturing method of micro-structured parts by the metal powder injection moulding (MIM) inserted micro-sacrificial plastic moulds which were prepared by nano-imprint lithography (NIL) technique. In this process named NIL/ì-SPiMIM, the feedstock composed of nano-sized copper powder and polyacetal-based binder was adequately prepared and moulded into polymethylmethacrylate films with fine line-scan structures, and it was sintered in a reductive gas atmosphere followed by solvent debinding of the films. The filling rate of feedstock into micro-channels and transcriptional property in sintered parts was evaluated by cross-sectional SEM observation. The experimental results revealed reasonable evidences using nanopowder could sinter at very low temperature but was not easily full-filled the feedstock into narrow cavity moulds. It can be concluded that the manufacturing method named NIL/ì-SPiMIM proposed in this study has great potential to produce precisely 3 dimensional complex metallic parts with the micro-structures.

Optimisation of Nanocrystalline Size of Powder Coatings for MicroMIM
Barreiros, F (Polytechnic Institute of Leiria, Leiria, Portugal)

MIM must be optimised concerning 4S powders characteristics: particle size (1S), particle size distribution (2S), shape (3S) and surface (4S) [1, 2]. These aspects have particular relevance in µMIM, originating problems during sintering. Tailoring the surface powders can contribute to a quality improvement of microparts. The modification of the surface properties of the stainless steel (SS) particles by coating them with a thin film of similar material can minimize the depletion of chromium and decrease the kinetics of grain growth [3]. However, the presence of SS nanocrystalline coating on the powders can change the mechanisms of the sintering process, from a solid state to a liquid phase. The formation of a liquid phase corresponding to an early melting of the out layer due to this nanometric character allows a decrease of the sintering temperature. The main objective of the present study is to optimize the grain size of the SS coating of powders in order to form a liquid phase at the lowest temperature.

Investigation of Micro Powder Injection Molding of micro gears with ZrO2 Powders
Yin, H (University of Science and Technology Beijing, Beijing, China)

Fabrication of the micro-sized gears was studied by µCIM with yttrium oxide stabilized tetragonal zirconia powders. The feedstock with a 48%vol ZrO2 powder and the rest of thermoplastic binder mixture was injection molded on the conventional PIM machine at 170°C under the pressure of 90MPa. The cavity temperature was optimized to be 50°C. After debinding and sintering at 1600°C for 2 hrs, micro gears were successfully replicated with good shape. The addendum circle diameter of the smallest one was 139.1µm. The surface roughness on mating flank of the micro gears was 1.6µm and the maximum microhardness reached as high as 7.23GPa.

Poster

Fabrication of Ultraprecision Micropart with Open Microporous by Nano Powder Injection Molding
Baek, E-R (Yeungnam University, Gyeongsang-bukdo, S Korea)

Fabrication of microporous material in complex and ultraprecision structure are challenging since its function in several devices. In this research, fabrication of open microporous with several micron size that formed in ultraprecision micropart by nano powder injection molding were investigated. The micropart itself represented by microbearing shape with 60 µm channel size and thickness up to 1 mm. The process was started by transfered 2.5 dimensional nickel metal pattern produced from X-Ray Lithography process into Polydimethylsiloxane (PDMS) soft mold. The process then followed by Metal Injection Molding (MIM) utilize 17-4 PH nanopowder with average diameter is 100 nm and mixed with binder based on wax. It’s found that composition powder-binder (% powder load), pre-sintering and sintering condition give significant effect to form the size of porous and final size and strength of micropart. This research shows the advanced batch production of micropart with open microporous with relatively easy, economical and fast compared to other processes.

Sintering of MIMed Part with Various Micro Features
Jang, J M (Korea Institute of Industrial Technology, Incheon Metropolitan City, S Korea)

In present work, the 316L green part with micro feature was fabricated by micro metal injection molding (µMIM). The micro features were designed with various width and height in two-dimensional shape. Shrinkage, porosity and distribution of pores depended primarily on debinding and sintering conditions such as pressure and temperature. With decrease of debinding pressure and increase of sintering temperature, shrinkage in width direction was increased while that in height was almost constant. Micro feature with high aspect ratio revealed relatively low sintering density and the increase of hydrogen gas pressure in debinding process improved the sintering density in outmost region, resulting in large difference in porosities of outmost and center regions. As a result, sintering behavior of micro features depends largely on debinding condition, especially hydrogen pressure, and the shape of the features.

Research on the Design of Sinter JoinedConnections for Powder Injection Moulded Components
Klimscha, K (Karlsruhe Institute of Technology, Karlsruhe, Germany)

With regards to powder-injection moulding, an increasing complexity of the component to be moulded results in an increased degree of complexity of the injection moulding tool. Sinter joining represents an alternative as it allows for component assemblies to be moulded as separate low-complexity parts which are then joined by means of sintering to form a component assembly.

Research in the field of sinter joining of µ-PIM components conducted at the wbk is dedicated to the development of a micro check valve. The micro check valve will be used to examine and highlight the possibilities offered by sinter joining. Preliminary tests were performed on sample bodies with shapes similar to that of a valve. The resilience was determined by means of tensile tests and internal pressure tests. Research has shown that the sinter joined connections achieved can bear tensile forces of up to 540N and internal pressures of 700bar.

Effects Of Debinding Atmosphere In Microstructure Of Micro MIMed Part
Ko, S-H (KITECH, Incheon, Korea)

Metal injection moulding(MIM) is a promising method to manufacture the micro metallic parts. Debinding process is one of the most important step to influence the properties of final MIMed parts. The effects of thermal debinding atmosphere of 316L stainless steel feedstocks were studies. The powder size of 316L stainless steel was 4 ìm and 8 ìm, respectively. The debinding atmosphere was changed from 5 torr to 760 torr of hydrogen gas. Although the pores of MIMed part debinded in 760 torr of hydrogen gas were uniformly distributed in the brown part, the pores of MIMed part debinded in 5 torr were concentrated in the surface of brown part. It was also found that the binder removal rate was much higher in 5 torr than in 760 torr. The effect of increasing rate of temperature on the microstructure of MIMed parts was also evaluated.

Evaluation of Particle Size Effect of 17-4 PH Stainless Steel through Powder Injection Moulding
Kwon, Y-S (CetaTech, Kyongnam, Korea)

We investigated the particle size effect of 17-4 PH stainless steel powders through powder injection molding. The used mean particle sizes are 10, 5, and 3 ƒÝm. We investigated solid loading, processing conditions, and mechanical properties in terms of particle size. After basic PIM study, we investigated micro features manufactured by powder injection molding in terms of feature size and dimensional consistency. This study will be applied to micro component of dental devices.

Characterizations of Microbearing Produced by Nanopowder Injection Molding and Soft Lithography Process
Tirta, A (Yeungnam University, Gyeongsang-bukdo, S Korea)

Characterization of Microbearing with channel size 60 µm and thickness up to 1 mm that fabricated by Nanopowder injection Molding and Soft Lithography Process were investigated. The microbearing process was started by transfered 2.5 dimensional nickel metal pattern produced from X-Ray Lithography process into Polydimethylsiloxane (PDMS) soft mold. The process then followed by Metal Injection Molding (MIM) utilize 17-4 PH nanopowder with average diameter is 100 nm and mixed with binder based on wax. The green samples were than debinded in alumina tube furnace with nitrogen atmosphere and followed by sintering in vacuum furnace in 13000C for 2 hours. The characterizations of micro bearing were done for some of mechanical aspects such as: hardness, porosity and density; and also by the real test condition.

Micro Inmould Labelling using PIM-Feedstocks
Vorster, E (Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany)

Two-component micro injection moulding is often considered to become a highly effective process for the series production of micro components from multi-functional materials.

Nevertheless, beneath the common way of two-component injection moulding, i.e. merging two or more resins in one tool, a further method seems to be attractive: Inmould-labelling (IML). By this method a foil or film containing metal or ceramic powders is fixed in an injection mould cavity and, subsequently, a PIM-feedstock is injected backwards. The resulting green bodies have to undergo debinding and sintering procedures appropiate for both materials so that a complex multilayer part is obtained. As the foils might be printed, painted, or stamped before insertion a PIM body with various surface structures and/or functionalities can be achieved. Additionally, the foils might be filled with extremely fine or even nanopowders so that surface qualities and shaping accuracy can be considerably increased.

At present, a few attempts like e.g. the EU-funded “Multilayer” project aim at the development of PIM inmould-labelling. The current status of the R+D activities will be presented.

Related features for download:

• Medical and dental applications for microminiature powder injection moulding (microPIM) – a roadmap for growth
• Micro metal injection moulding for thermal management applications using ultrafine powders
• Accuracy evaluation of ultra-compact gears manufactured by the microMIM process
• Micro powder injection moulding – challenges and opportunities
• Powder injection moulding of cemented carbides for the production of micro parts and micro structure
• Manufacturing and characterisation of isolated microparts made by PIM for a micro annular gear pump