Powder injection molding (PIM) is a net fabrication technique that combines the
complex shape-forming ability of plastic injection molding, the precision of die-casting,
and the material selection flexibility of powder metallurgy. For this
study, the design issues related to PIM for fabrication of thin-walled high-aspect
ratio geometries were investigated. These types of geometries are typical to the
field of microtechnology-based energy and chemical systems (MECS). MECS are
multi-scale (sizes in at least two or more different length scale regimes) fluidic
devices working on the principle of heat and mass transfer through embedded
micro and nanoscale features. Stainless steel was the material chosen for the
investigations because of its high-thermal resistance and chemical inertness
necessary for typical microfluidic applications. The investigations for the study
were performed using the state-of-the-art computer aided engineering (CAE)
design tool, PIMSolver��. The effect of reducing part thickness, on the process
parameters including melt temperature, mold temperature, fill time and switch
over position, during the mold-filling stage of the injection molding cycle were
investigated. The design of experiments was conducted using the Taguchi
method. It was seen that the process variability generally increased with
reduction in thickness. Mold temperature played the most significant role in
controlling the mold filling behavior as the part thickness reduced. The effects of
reducing part thickness, process parameters, microscale surface geometry and
delivery system design on the occurrence of defects like short shots were also
studied. The operating range, in which the mold cavity was completely filled,
was greatly reduced as the part thickness was reduced. The single edge gated
delivery system designs, with single or branched runners, resulted in a
completely formed part. The presence of microchannel features on the part
surface increased the possibility of formation of defects like short shots and
weld-lines when compared to a featureless part. The study explored some typical
micro-fluidic geometries for fabrication using PIM. The final aspect of this study
was the PIM experiments performed using a commercial stainless steel
feedstock. Experiments were performed to study the mold-filling behavior of a
thin, high aspect ratio part and also to study the effect of varying processing
conditions on the mold-filling behavior. These experiments also provided
correspondence to the mold filling behavior simulated using PIMSolver��. The
PIMSolver�� closely predicted the mold-filling patterns as seen in the experiments
performed under similar molding conditions. The study was successful in laying
down a quantitative framework for using PIM to fabricate micro-fluidic devices. / Graduation date: 2005
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/31158 |
| Date | 06 December 2004 |
| Creators | Urval, Roshan |
| Contributors | Atre, Sundar V. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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