Researchers from the Massachusetts Institute of Technology (MIT) and Evenline have explored the feasibility of using glass 3D printing to produce interlocking masonry units for the construction industry.
Published in Springer Nature, this study examines how glass AM can increase design flexibility and reduce tooling costs when compared to traditional glass casting methods. Although the research shows that glass AM holds potential for creating innovative building components, additional refinement will be needed for large-scale applications.
The study was supported by Open Access funding provided by the MIT Libraries, along with support from the Professor Amar G. Bose Research Grant Program and the MIT Research Support Committee.
Developing interlocking masonry units with glass AM
According to the researchers, the study focused on the development of interlocking masonry units through glass AM, allowing building components to fit together without adhesives. Instead, the components rely on interlocking features for structural stability. This approach aligns with the construction industry’s growing emphasis on circular construction, which aims to minimize waste and enhance material recyclability.
To conduct the study, the researchers used the G3DP3 printer, a glass printing platform, capable of producing objects up to 32.5 x 32.5 x 38 cm in size. Given the size limitations, modular masonry units were designed so that they could be assembled into larger structures.
The study tested three fabrication methods: Fully Hollow (FH), which involved printing hollow units without interlocking features; Print-Cast (PC), which combined printing and casting by pouring molten glass into pre-printed units to create interlocking elements; and Fully Printed (FP), where all components, including the interlocking features, were printed directly.
Each method was evaluated for geometric accuracy, surface roughness, and mechanical strength to assess its viability for producing structurally sound masonry units.
Key findings from testing and analysis
The study tested the strength of each unit, focusing on both initial fracture and ultimate strength. Results varied depending on the manufacturing method. FH units exhibited the highest strength, with initial fracture strengths ranging between 3.64 and 42.3 MPa and ultimate strengths between 64.0 and 118 MPa.
Additionally, PC units showed moderate performance, but some experienced fractures caused by thermal shock during the casting process. FP units had the lowest mechanical strength, but they demonstrated potential for future development as a recyclable, all-glass material.
In addition to strength, geometric accuracy and surface roughness were also assessed. FH units showed the highest accuracy, with dimensional deviations of less than 1 mm and a standard deviation of 0.14–1.6 mm, thanks to post-printing machining that resulted in smoother surfaces and better structural performance.
However, PC units exhibited significant variability in dimensions, due to temperature inconsistencies during the casting process, leading to deformations and cracks. Their rougher surfaces, especially those in contact with graphite molds, led to increased stress concentrations and reduced mechanical strength.
FP units had better precision than PC units but were less accurate than FH units. Surface texture issues from the graphite build plate, particularly the 1 mm x 1 mm grid pattern, caused localized deformation and negatively affected performance.
Overall, smoother surfaces, like those in FH units, improved structural integrity, while rougher surfaces in PC and FP units resulted in premature fractures, highlighting the need for further refinement.
Implications for construction and circular design
Beyond evaluating the structural capacity of each method, the researchers also considered the broader implications of using glass AM for sustainable construction practices. Made entirely of glass, the FP and PC units offer greater potential for recyclability, while FH units present challenges due to the use of separate interlocking components, which complicate their recyclability.
Although FH units show the most immediate potential for practical use in construction, thanks to their strength and faster production time, FP units could serve as a longer-term solution for creating recyclable, all-glass components.
However, the PC method is time-consuming and prone to fractures caused by thermal shock, while FP units exhibit lower mechanical strength due to surface roughness and inconsistencies during the printing process.
As a result, the researchers recommend further studies to improve the FP process, particularly by optimizing surface texture and tool paths to enhance strength and performance. They also suggest exploring a Cast-Print hybrid method, where interlocking components are cast first and the remaining structure is 3D printed on top, to reduce oxidation and improve efficiency.
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Was glass 3D printing used before?
Excluding the construction sector, glass 3D printing has been used previously for different applications.
Working with Nanoscribe, researchers from the University of Freiburg utilized two-photon polymerization for 3D printing glass silica microstructures. Using Glassomer materials, the team succeeded in producing intricate objects with an exceptionally low surface roughness of 6 nanometers, which is considerably smoother compared to the 40-200 nanometers typically observed in other glass components.
Elsewhere, researchers at MIT Lincoln Laboratory developed a novel low-temperature method for 3D printing glass objects, using a custom ink that was curable at 250°C, unlike conventional methods that required temperatures over 1,000°C.
Based on a nanocomposite material, their approach allowed for the creation of glass components with unique characteristics, including capacitors and resistors. Though optical clarity remained a challenge, the team believed their method could enable the production of microsystems and enhance the glass and ceramic industries, offering wide-ranging applications in electronics and microfluidics.
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Featured image shows all manufactured units assembled together in a wall configuration prior to mechanical testing. Photo via MIT.
