Can you 3D print with glass?
3D Printing has shown itself to be a versatile manufacturing method, able to use a wide range of materials. Traditionally, the most common of these have been plastics and metals. However, in the last few years another material has enjoyed …
3D Printing has shown itself to be a versatile manufacturing method, able to use a wide range of materials. Traditionally, the most common of these have been plastics and metals. However, in the last few years another material has enjoyed something of a renaissance – glass! While it has been challenging to work with, there have been a number of innovations demonstrating how viable it really is.
In 2015, two organisations independently demonstrated prototype printers that could work. Israel-based Micron3DP demonstrated a technique that heated glass and extruded it into basic, low resolution forms. Shortly afterwards, the Mediated Matter Group at MIT employed a similar method for their G3DP project.
The 3D printer from the group at MIT had a number of interesting properties, documented in their published paper. Due to the high melting point and brittle nature, melting a room temperature solid filament FDM-style was out of the question. Instead, the printer had to maintain molten glass at key temperatures throughout the printing process in order to achieve FDM levels of print quality. They came up with the following process:
- Firstly,a kiln is heated to over 1000 C. This is the melting temperature of soda-lime, a common form of glass with one of the lowest melting points.
- Its then passed through a heated nozzle held at a similar temperature to the kiln, flowing freely due to gravity. To stop the flow from the nozzle, the team blew compressed air at it to cool it to low enough temperature. Restarting the flow involved blowing a propane torch at the nozzle to heat it back up.
- Finally, the glass was deposited in layers in a heated chamber, held at the annealing point of the glass. For soda-lime glass, this temperature is around at 546 C. This is the temperature at which the glass remains ‘solid’ and retains its form, but microscopically allows for internal strains to relax. Not keeping glass at this temperature for a period, and instead cooling it too quickly, results in glass parts with significant residual stresses and poor mechanical properties.
After significant development, the team presented glass structures manufactured using their printer at an exhibition at the Smithsonian Design Museum. Speaking about the possibilities the printing technique provided, members of the team suggested that it could be used in architectural applications. Additive manufacturing could open up the ways designers could create transparent fixtures, directing light in new and exciting ways. Engineers could also create building-size structures with glass, taking advantage of its compressive strength.
Since this event, the group made further modifications and improvements in a follow-up “G3DP2” project, once again demonstrating that 3D printing with glass is now more feasible than ever.
Fused Silica Resins
These successful demonstrations of FDM-like glass printing have been very exciting for architects and engineers. However, they are limited by the extrusion process, which produces parts with high surface roughness and relatively low resolution. In 2017, the Karlsruhe Institute of Technology (KIT) successfully demonstrated a different method. This could remedy these issues and produce parts with higher precision and better optical properties.
The team suspended fused silica, in a castable polymer resin, and used a desktop SLA printer to shape the resin. Fused silica is a very important type for many reasons. It has superior UV transmission, lower thermal expansion coefficients and higher strength compared to less pure forms of glass. This makes it ideal for lab equipment and precision optics.
Its toughness also makes it very difficult to directly shape using traditional techniques. However, suspending the glass particles in a resin meant that they could print the exact form they wanted by manipulating the more manageable polymer. Then, by firing the print at a high temperature, they burned off the excess resin and densified the glass. Therefore, resulting in a high resolution fused silica part.
This paves the way for further improvements, and could find applications in diagnostic medicine. Printing methods could one day be used to create lab-on-a-chip technologies and micro-optics that could be used to diagnose patients away from a lab.
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