Design of Channels in Complex Additively Manufactured Components

Abstract

Additive manufacturing is an attractive manufacturing method which allows for the easy fabrication of geometries that are difficult or even impossible to produce through traditional manufacturing methods. This is especially true for metal, as additive manufacturing allows for near net shape parts to be manufactured from difficult to machine materials, such as titanium, Nitinol, and nickel based super alloys such as Inconel. One area of interest is the use of additive manufacturing to fabricate infrared (IR) sensor windows for use in hypersonic missiles. IR sensors are used by hypersonic missiles to navigate, particularly during the later stages of flight. However, heat buildup stemming from the flight speeds can distort sensor readings. Current methods of cooling the window involve either spraying a jet of coolant or pumping coolant through drilled straight channels. Additive manufacturing allows for more focused coverage, with varying cross-sections and more complex internal geometries. Additionally, surface roughness can significantly affect the flow of fluid through channels, and some level of surface roughness can be desirable for heat transfer. In addition to determining if the channels can be manufactured, the surface roughness needs to be quantified to allow for more complete design knowledge. Currently, there is not a single suitable design guide for additively manufactured channels. Therefore, this investigation aims to determine the manufacturability of multiple channels via additive manufacturing, with the goal of establishing an initial design guide suitable for the successful manufacturing of a part with internal channels via additive manufacturing. With this goal in mind, this investigation is divided into six distinct studies. The first study of this investigation explores the manufacturability of vertical and horizontal channels additively manufactured from Ti-6Al-4V, with some initial optical microscope inspection of the channel morphology and surface roughness. Study 2 compares the surface roughness measurements of these same specimens across three different techniques, and Study 3 investigates the printability of complex manifold geometries using Ti-6Al-4V. A repeat of the first two studies was conducted for AlSi10Mg in Study 4, while Study 5 explored the design space of different channel angles and overhang sizes, with a particular focus on channels with widths outside of the manufacturer recommended width. Finally, Study 6 applied the information from the previous five studies; the focus was the printing of prototype windows from both Ti-6Al-4V and AlSi10Mg and iterating the design based off nondestructive post-print visual and X-ray investigations.