Manufacturing Bits: Dec. 20

3D printed wind instruments
Autodesk Research and Dartmouth have developed a 3D printing technology that enables novel musical wind instruments in the form of animals, doughnuts and other shapes.

With a 3D printer, researchers devised 16 free-form wind instruments in various shapes, such as a star, bunny, snowman, dragon, horse, pig, cat and sheep. There is even a way to make a doughnut instrument.

A star is born? Here’s a three-dimensional free-form musical wind instrument in action. (Source: Autodesk)

For this, researchers developed a technology called Printone, a tool that turns three-dimensional shapes into a musical instrument with a target set of frequencies.

There are some challenges with this technology. For example, the resonance frequency must be accurate for a given hole in the wind instrument. And it must enable different shapes with various hole configurations.

In the lab, researchers have developed a flow. The first step is to model the wind instruments as a passive resonator. Then, the resonance frequency is estimated using a technique based on a generalized eigenvalue problem. Then, the designs can be fabricated using a 3D printer, resulting in a so-called “printwind instrument.”

“Our tool imports existing polygonal meshes, which specifies the exterior shape of the instrument. The tool automatically hollows out the shape to generate an internal cavity,” according to a paper from Autodesk and Dartmouth. “Then, the user positions the fipple and finger holes by clicking on the object’s surface. The user can also uniformly scale the entire instrument and adjust the orientation of the fipple. The size of the finger holes can be continuously adjusted to manipulate the frequency of the resonance. The user can also specify whether the finger holes are open or closed to test the sounds produced by their instrument design.”

Hexagonal diamonds
The Australian National University (ANU) and others have synthesized perhaps one of the world’s hardest diamond materials.

In the lab, researchers have devised a hexagonal diamond in a nano-crystalline form. Common diamonds have a cubic structure. In contrast, hexagonal diamonds are an allotrope of carbon with a hexagonal lattice, making them up to 58% harder than cubic diamonds.

Researchers synthesized hexagonal diamond using a diamond anvil cell. Two diamonds were inserted in the cell and compressed. Then, the resulting materials were synthesized at low temperatures. The resulting hexagonal diamonds could be used for drills, which are useful for cutting through ultra-solid materials on mining sites.

The work is interesting for other reasons. Typically, hexagonal diamond structures are usually found in meteorites. The most famous one is the Canyon Diablo meteorite in Arizona. In 1967, this meteorite was discovered. The meteorite consisted of a hexagonal diamond, sometimes called Lonsdaleite. The so-called Canyon Diablo meteorite supposedly hit the earth about 50,000 years ago.

ANU, however, developed hexagonal diamonds in the lab. “The hexagonal structure of this diamond’s atoms makes it much harder than regular diamonds, which have a cubic structure. We’ve been able to make it at the nanoscale and this is exciting because often with these materials ‘smaller is stronger,’ ” said ANU Associate Professor Jodie Bradby.