Scientists 3D print transparent glass

MIT researchers have for the first time developed a new high-temperature system that can produce 3D printed transparent glass objects.
Researchers have attempted to 3D print glass objects in the past, but a major obstacle has been the extremely high temperature needed to melt the material.
Some have used tiny particles of glass, melded together at a lower temperature in a technique called sintering. But such objects are structurally weak and optically cloudy.
The high-temperature system developed by the team at Massachusetts Institute of Technology (MIT) retains the strength and transparency of glass.
The new system was developed by Neri Oxman, an associate professor at the MIT Media Lab; Peter Houk, director of the MIT Glass Lab; MIT researchers John Klein and Michael Stern; and six others.

Like other 3D printers now on the market, the device can print designs created in a computer-assisted design programme, producing a finished product with little human intervention.

In the present version, molten glass is loaded into a hopper in the top of the device after being gathered from a conventional glassblowing kiln.
When completed, the finished piece must be cut away from the moving platform on which it is assembled.
In operation, the device's hopper, and a nozzle through which the glass is extruded to form an object, are maintained at temperatures of about 1,037 degrees Celsius, far higher than the temperatures used for other 3D printing.

The stream of glowing molten glass from the nozzle resembles honey as it coils onto a platform, cooling and hardening as it goes.
One challenge the researchers faced was keeping the filament of glass hot enough so the next layer of the structure would adhere to it, but not so hot that the structure would collapse into a shapeless lump.
They ended up producing three separate components that can independently be heated to the required temperatures - the upper reservoir for the stock of molten glass, the nozzle at the bottom of that chamber, and a lower chamber where the printed object is built up.

"Glass is inherently a very difficult material to work with," Klein said.
Its viscosity changes with temperature, requiring precise control of temperature at all stages of the process.
The new process could allow unprecedented control over the glass shapes that can be produced, Oxman said.
"We can design and print components with variable thicknesses and complex inner features - unlike glassblowing, where the inner features reflect the outer shape," Oxman said.
Oxman said that she foresees the process being adapted to create much larger structures.
The study was published in the Journal of 3D Printing and Additive Manufacturing.