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Depowdering Long and Circuitous Internal Channels

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Conference Abstract: Many of us know that when designing parts to be printed via a powder bed fusion (PBF) process, there are limits on the aspect ratio of internal channels. For parts which rely on long circuitous microchannels in materials like AlSi10Mg which create rough internal surfaces, PBF provides technical challenges.
Oscillating Heat Pipes (OHPs) are pressure vessels with complex hermetic internal microchannel arrays that serve as high effective thermal conductivity structures. OHPs are used extensively for thermal management of high heat flux devices like laser diodes and power electronics. OHPs enable significant weight savings and performance gains over constant conductance heat pipes and other state of the art thermal solutions in the aerospace industry. SWaP-c improvements typically come from adding thermal solution to existing complex structural components by drop-in replacement of those components with OHPs. This allows for removal of alternative thermal solution mass (such as a pumped fluid loop). Complexity and part count reduction is a hallmark of additive manufacturing (AM), but several issues must be overcome to create AM OHPs that can match the performance of CNC machined & brazed OHPs (10+ year heritage at ThermAvant Technologies), and hopefully exceed the manufacturing limitations of that subtractive machining methodology.
In this presentation, we will explore the work ThermAvant has done in depowdering long circuitous internal microchannels in a variety of form factors, from coupons to full-size parts. We will also explore how different materials impact depowdering techniques. Feasibility of a variety of acid etching, high frequency vibration, and fluid flushing techniques will also be discussed.