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3D-printing initiatives span whimsical to practical.

Recent initiatives related to 3D printing run the gamut from practical to whimsical, from the rapid turnaround of optical prototypes based on CAD data to the development by university researchers of a children's toy called a zoolophone--a xylophone with animal shapes. But even the whimsical project turns out to have practical applications, ranging from noise and vibration control to RF filtering.

Practicality was at the forefront of a joint initiative announced last November by OPTIS, a CAD software vendor, and Luxexcel, a 3D-printing service for optical products. They teamed up to provide automotive manufacturers a fast and easy way to go from design to 3D-printed prototype.

Software from OPTIS--a CAD software vendor specializing in the simulation of light, human vision, and physically correct visualization--enables automotive designers and manufacturers to simulate their lighting and optical designs, testing and verifying virtual prototypes within their CAD environment. But the transition to real prototypes traditionally has been time-consuming and expensive, involving, for example, diamond milling and turning or--for elaborate freeform shapes--injection molding.

Luxexcel's Printoptical technology offers an alternative. OPTIS has integrated Luxexcel material within the OPTIS library, providing customers fast access to 3D-printed customized and fully optimized prototypes (Figure 1) within a few days. Commented Paul Comelissen, head of marketing and online business development for Luxexcel, in a press release, "With this digital process, we change a 3,000 years old analog industry and make it future proof."

Whimsical could describe the zoolophone (Figure 2), built by computer scientists at Columbia Engineering, Harvard, and MIT, who used it to demonstrate that sound can be controlled by 3D-printing shapes. They presented their work (1) at SIGGRAPH Asia last November in Kobe, Japan--an event targeting the computer-graphics community, which has long been interested in the simulation of contact sounds as well as computational fabrication techniques such as those the researchers used.

The researchers developed an algorithm that optimized for 3D printing the instrument's keys in the shape of lions, turtles, elephants, giraffes, and more, modeling the geometry to achieve the desired pitch and amplitude of each part. The zoolophone is an idiophone--an instrument that produces sound through its own vibration rather than employing strings (chordophones), columns of air (aerophones), or membranes (membranophones). Most idiophones employ rectangular bars, for which the relationship of sound and geometry is well understood.

In contrast, determining the optimal animal shape that produces the desired amplitude and frequency proved to be computationally challenging. The team spent nearly two years developing computational methods while borrowing concepts from computer graphics, acoustic modeling, and mechanical engineering as well as 3D printing. To increase the chances of finding the optimal shape, the researchers developed a fast stochastic optimization method, which they call Latin Complement Sampling (LCS). LCS requires as input a desired shape as well as frequency and amplitude spectra, and LCS optimizes the shape through deformation and perforation to produce the wanted sounds--including overtones. Previous algorithms had been able to optimize either amplitude or frequency but not both.

"Our zoolophone's keys are automatically tuned to play notes on a scale with overtones and frequency of a professionally produced xylophone," said Changxi Zheng, assistant professor of computer science at Columbia Engineering, who led the research team. (2) "By automatically optimizing the shape of 2D and 3D objects through deformation and perforation, we were able to produce such professional sounds that our technique will enable even novices to design metallophones [metal idiophones] with unique sound and appearance."

More than a toy, the researchers say, the zoolophone represents fundamental research into understanding the complex relationships between an object's geometry and its material properties. "Our discovery could lead to a wealth of possibilities that go well beyond musical instruments," Zheng added. For example, the algorithm could help reduce computer-fan noise, control vibration in bridges, and advance the construction of micro-electro-mechanical resonators. Zheng already has been contacted by researchers interested in applying his approach to MEMS RF filters.

"Acoustic design of objects today remains slow and expensive," Zheng said. "We would like to explore computational design algorithms to improve the process for better controlling an object's acoustic properties, whether to achieve desired sound spectra or to reduce undesired noise. This project underscores our first step toward this exciting direction in helping us design objects in a new way."

By Rick Nelson, Executive Editor


(1.) Zheng, C., et al., "Computational Design of Metallophone Contact Sounds," ACM Transactions on Graphics, November 2015.

(2.) "Change the Shape, Change the Sound," Newswise, Oct. 28, 2015.
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Author:Nelson, Rick
Publication:EE-Evaluation Engineering
Geographic Code:1USA
Date:Mar 1, 2016
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