Page 50 - Spring2022

ADDITIVE MANUFACTURING FOR ACOUSTICS
(Ishiguro and Poupyrev, 2014). These are all examples that can be found in industrial, academic, or hobby applications.
Google searches for AM turn up a variety of applications as wide as one’s imagination, with top “hits” including things like figurines of cartoon characters, cell phone cases, and more. It’s worth pointing out that although most people vaguely familiar with AM imagine desk- top-sized printers that extrude plastics, people have developed printers that can make food (Sun, 2015; see https://bit.ly/3r0Tjli); electronics (Goh, 2021); biological tissue (Mannoor, 2013; see https://bit.ly/3nIKeMd); and even buildings (Paolini, 2019).
AM has seen significant activity in both academic instruc- tion and research. The recent past has seen the emergence of AM graduate certificate or degree programs, and academic
journals are published that focus solely on additive processes, applications, and development. A wide range of conferences, from general to content specific, also exist. Within the
Acoustical Society of America, two special sessions focused on AM have taken place since 2017, and recently a special issue of The Journal of the Acoustical Society of America (see https://bit.ly/3gzUNws) was published highlighting research at the intersection of AM and acoustics.
Given the wide range of potential applications for AM in acoustics, it’s no surprise that acousticians of all types would find uses for a new fabrication approach. This arti- cle introduces AM and its applicability to a wide range of applications in acoustics. We begin by introducing the basic technology, then review some case studies of cur- rent research and educational and industrial uses of AM
related to acoustic applications, and conclude with some perspectives on the future of AM in acoustics.
Overview of Different Additive Manufacturing Techniques
If you wanted to build something like a scale model of a building, you could start with a block of metal, plastic, or wood and cut out the shape of the building using a saw or other standard machining equipment. This approach is known as subtractive manufacturing because you remove, or subtract, the material you don’t want from a large piece of that material.
An alternative approach to building the same model would be to use something like LEGO bricks to create the same shape by adding material point-by-point only where it is needed. Although a rudimentary example, building with LEGO bricks is an example of AM where small pieces are added to make the final object. That object can take almost any shape you can imagine, as is the case with building with LEGO bricks.
The concept of construction by adding material where you want it can be accomplished in a variety of ways. Three of the most common approaches are described here, but we note that this list is far from exhaustive. The key differ- ence between the three methods described here is the base material, in that the material that is added sequentially to additively build up the object. In the example above, the base material is a plastic LEGO brick. The method of joining in that case is snapping the bricks together. Com- mercial additive approaches typically use one of three base material forms, powder, liquid, or thin strips, all of which are joined by adhering a new layer of material to
Figure 2. Three forms of AM. a: Powder-based printing. b: Stereolithography. c: Fused deposition modeling. See text for more details.
50 Acoustics Today • Spring 2022