3D Printing Brings Sustainability, Accessibility to Glass Manufacturing

Additive manufacturing with materials like polymers, metals and ceramics can be done sustainably — by choosing recyclable materials or those based on renewable resources. But AM thus far has mostly overlooked a material that is, at least in theory, “infinitely recyclable”: glass.

Victoria, Australia, startup Maple Glass Printing was founded to develop a means of more easily manufacturing parts and structures from glass. But the material is expensive, and the founders quickly found themselves reusing scraps of glass to make new filament. Sustainability has been a tenet of the company ever since, along with its mission to lower the barriers to entry in glass manufacturing.

Lowering the Barriers to Glass Manufacturing

Maple Glass Printing was co-founded in 2017 by two materials engineers, Nick Birbilis and Darren Feenstra, who met at Monash University. (Feenstra hails from Canada — hence the use of “maple” in the company’s name.)

The idea behind the startup and its technology was initially to speed the process for manufacturing objects out of glass. Commercially, glass items are made by casting the molten material into molds, which makes it prone to many of the same tooling challenges and geometry restrictions as other processes based on tooling. Glass blowing offers another production method, but is time-consuming, size limited and requires great skill.

“The 3D printing process allows for such a different type of manufacturing,” says Tony Koutsonikolas, research and development mechanical engineer. The company sees their extrusion-style technology as a means to achieve many of the same benefits that FFF and DED have brought to polymers and metals, respectively — in terms of geometric complexity, avoidance of tooling, and the flexibility to iterate designs more rapidly.

It took several years to develop a working glass 3D printer and produce the first test pieces, but these successes allowed the startup to “graduate” from a Monash lab to its own space in 2020. Now in 2023, the company is introducing its first commercial machines for glass 3D printing, the Maple 2 and Maple 3.

How to 3D Print with Glass

Maple Glass Printing’s current platforms use glass rods known as glass “cane” as the feedstock. A stationary nozzle inside the Maple 2 and Maple 3 printers heats the material to 1,000°C, then deposits the molten glass onto a moving build platform. The entire process takes place in a build chamber that is effectively a kiln — and which, in early iterations, literally was a repurposed one.

(In future versions of this machine, Koutsonikolas says, the motion will be reversed with the nozzle moving rather than the plate; the build chamber will stay the same, but the envelope will grow with the nozzle able to access more of the space inside the kiln.)

Even though glass printing requires significantly elevated temperatures compared to other materials, it is actually a fairly energy efficient process. According to advanced manufacturing engineer Dylan Vlahopoulos, the machine uses five times less power than a hair dryer.

“Only a very small area needs to be heated at once,” he says, and each layer of glass is only hot for a short amount of time.

The limited use of heat in the process also brings advantages to the final glass print. Geometric features like overhangs and bridges are possible because of how quickly the material cools and sets into place. Localized heating and cooling also prevents build up of stresses, which can happen in glass blowing and casting where the material is allowed to cool all at once. Effectively, the glass is printed and annealed at the same time; the controlled, localized cooling of the material avoids stresses that can happen when cooling blown or commercially manufactured glass parts that are formed all at once, Vlahopolous says.

Early applications for the platform have mostly centered on artistic projects and demonstration pieces, as well as some lab implements produced for researchers studying neon and fiber optics. And while the glass 3D printer can print parts for use as-is, the company has also experimented with combining printed glass with more conventional glass-making techniques. It is possible, for example, to 3D print essentially a preform structure which a skilled glass artisan can then modify or even augment with manually shaped or blown elements.

A Circular Economy for Glass

Along the way to developing the 3D printing technology, Maple Glass Printing has discovered ways of closing the loop for this material. The expense of the glass cane feedstock as described above led the co-founders to begin recycling scrap to produce test prints early on. In order to re-use that spent glass, they had to come up with a way of turning it back into glass cane.

Today most glass cane is produced manually, by a human technician literally stretching molten glass into fine strands. The process is tedious and even the most practiced glass puller will produce cane that varies in straightness and diameter across its length. The labor-intensive process coupled with the fact that glass cane is made from new materials combines to make this feedstock quite expensive.

Maple Glass Printing either had to become good at drawing glass into cane itself, or come up with another solution. The company ultimately developed another machine alongside the 3D printer platform: the Vitri-Glass.

This piece of equipment features a crucible on the top where glass pieces can be loaded and melted. The machine then extrudes the cane and a technician guides it into an automated pulling system. The speed of the pull can be controlled to produce cane that is thicker or thinner depending on the application. While the process still requires human attention, it results in much more consistent glass cane with less difficulty — and provides an easy way for a glass 3D printing user to recycle prototypes, scraps or spent products into feedstock.

“We don’t live in a perfect world,” Vlahapolous says, “but in theory, glass is infinitely recyclable.”

Glass scraps of different colors must be processed separately (coloring agents can influence properties such as stiffness), and there is a risk of crystallization that could make the recycled cane unusable. However, the benefits from reusing glass far outweigh the risks, and Maple Glass Printing is now leaning into the recyclability of the material as a critical advantage of its technology.

3D Printing Glass Beyond the Kiln

Finding efficient means of recycling glass via the 3D printing process has implications not only for glass printing users who want to reduce their waste, but also for reclaiming glass that is already in the world. Maple Glass Printing sees great potential in recapturing glass that makes up windows and facades, and these architectural applications could become more important for the company in the near future.

While the Maple 2 and 3 machines are confined to the build envelope of the kilns in which they operate, the next generation of glass 3D printers that the company is developing will comprise a printhead on a robot arm to build much larger structures in the open. The company’s learning about how to print glass inside a kiln as well as how to extrude it into a room temperature environment with the Vitri-Glass process are both informing this work. Because only a small amount of glass is molten at a time and rapidly cools, the impacts on material properties should be minimal for this open air, large-format printing. 

One future promise of this LFAM work will be integrating the printed glass with other architectural elements, such as metal frames that could be produced through a processes such as wire arc additive manufacturing (WAAM). While the printed glass will always appear layered, there are plenty of applications where windows don’t need to be perfectly clear, and the bead size can be adjusted to achieve the desired diffusion or other effect.

The large-format solution is still in work, and in the meantime the company is focused on identifying and developing applications for its smaller-sized commercial machines. It’s not yet clear where all the possible opportunities for such a solution will be found, but the company is confident its technology can make a difference not only in how glass is manufactured, but also how it is recaptured and recycled.

“How we treat glass in the future could change quite a lot,” Koutsonikolas says.