As the Earth continues to turn, more people are born, and more things are invented and manufactured, global energy consumption will obviously go up, not down. Burning fossil fuels is the major leading cause of excessive CO2 emissions, which can cause climate change and rising sea level, and despite our best efforts, nearly 85% of the planet’s total energy usage still stems from traditional fossil fuels. Obviously, one of the largest energy consuming sectors is industrial, and according to the 2019 Wohlers Report, the 3D printing sub-sector was showing annual energy consumption growth rates of 24.5%. This is particularly important given the sustainability claims made by many parties in the industry.
While additive manufacturing (AM) is not that high up in the global manufacturing market’s use of energy, industry experts believe the field will continue to grow, and, as such, use more energy. A team of researchers from the University of Central Lancashire’s School of Engineering published a paper on their attempt to, as they wrote, “quantify the energy use of the most common forms of AM technologies.”
“To date, research efforts have focussed on the energy use of industrial AM machines, and little research has been conducted on the numerous low-cost desktop 3D printers. Additionally, there is a gap in our knowledge of how to minimise the energy consumption of desktop 3D printers and how to predict their energy use,” the abstract states. “To fill this gap, high resolution (1 Hz) power measurements were made for a range of low-cost fused filament fabrication and vat polymerisation desktop 3D printers.”
Sales of desktop 3D printers keep going up, and as the researchers explained, it’s important to estimate just how much energy the systems are really using. So they wrote the paper, focusing on the common fused filament fabrication (FFF) and vat polymerization (VP) technologies specifically, in order to “address the current lack of energy data, evidence-based energy reduction strategies, and energy prediction models associated with low-cost desktop 3D printers.”
Their main goals in publishing this paper were:
- Cataloging energy use of common desktop 3D printers for life cycle assessments
- Addressing the effects of different 3D printing parameters on energy consumption
- Identifying good ways to reduce energy consumption
- Developing models that can help predict energy use with simple 3D printing metrics
The two main energy requirements for 3D printing parts with FFF and VP (including SLA and MSLA) technologies are, first, the energy needed to move the material from its “locally stored position” to its place in the final part; this isn’t much, as the distance the feedstock must travel is usually pretty minimal. Second is the energy required to change the chemical or physical state of the polymers.
“All other energy used by the printers, such as that used for heated beds, controllers, fans, overcoming friction and LCD screens should be minimised,” the team wrote.
The researchers calculated that the minimum amount of energy needed to cure a unit mass of photopolymer resin, and thus gauge manufacturing efficiency, is two orders of magnitude lower than what’s needed to melt the same amount of thermoplastic.
For their research, the team designed a custom part—the G-clamp pictured above—and used various geometric complexities so they could work out “a direct comparison of the energy use of a range of 3D printers and print parameters,” as part geometry might play a role in determining how much energy is used to print said part. They also developed a custom power meter/data logger in order to sample power at 1 Hz with a measurement accuracy of ±1.0%, measuring both current and voltage.
Several different desktop 3D printers, materials, and layer heights were used, which you can see in the table below. The room temperature during all the prints ranged from 22 to 25 °C.
“The volumetric specific energy consumption (VSEC) of parts printed on common desktop 3D printers was measured using a range of build parameters. The VSEC range for FFF was 24.8–85.7 kJ/cm3, for SLA it was 10.8–21.5 kJ/cm3 and for MSLA it was 18.4–19.3 kJ/cm3,” the researchers wrote.
They experimented with different materials, strategies, and printer modifications, such as using 100% infill and insulating the heated print bed and hotend, to see if they could decrease energy consumption, and also developed semi-empirical equations that can predict energy consumption, based on 3D printing metrics, for each of the AM technologies they tested, this time printing the 3D Benchy model.
“For FFF printers, most of the energy goes into heating the build surface. This is true even for PLA, which requires lower bed temperatures than most materials. Insulating the heated bed and nozzle, printing with low-temperature materials, and printing with large layer heights are all effective methods of reducing the energy use of FFF printers, assuming the part specifications allow it,” the researchers concluded. “The energy use of SLA printers is almost linearly related to print time. Therefore, any actions that reduce print time, such as increasing layer height or reducing the number of print layers, will reduce energy use. For MSLA printers, the energy use is proportional to the layer exposure time, and the number of layers, not the volume of resin being cured. Therefore to lower the VSEC for MSLA printers, the build volume should be as full as possible.”
It’s important to remember that these equations will only be accurate for the specific 3D printers the researchers worked with, but that they will “provide a reasonable estimate for machines with similar components and machine dimensions.”
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