How a new 3D printer can automatically handle a variety of eco-friendly materials

Scientists have developed a 3D printer that can independently determine the characteristics of an unknown material. This advance could help make 3D printing more sustainable by allowing the use of renewable or recyclable materials that are difficult to characterize.

Although 3D printing has become very popular, many of the plastic materials used by these printers to create objects are difficult to recycle. Despite the emergence of new environmentally friendly materials for use in 3D printing, their implementation remains challenging as 3D printer parameters must be manually adjusted for each material.

To print a new material from scratch, you typically need to adjust up to 100 parameters in the software that controls how the printer extrudes the material when creating the object. For widely used materials such as mass-produced polymers, there are preset parameters that have been optimized through a long and careful process of trial and error.

However, the properties of renewable and recyclable materials can vary significantly depending on their composition, so creating fixed sets of parameters is practically impossible. In this case, users must manually set all these parameters.

Innovative solutions in 3D printing technology

Researchers solved this problem by creating a 3D printer that can automatically determine the parameters of an unknown material.

A joint team from MIT's Center for Bits and Atoms (CBA), the US National Institute of Standards and Technology (NIST), and Greece's National Center for Scientific Research (Demokritos) has upgraded the extruder, the heart of the 3D printer, so it can measure forces and material flow.

This data, collected during the 20-minute test, is fed into a mathematical function that is used to automatically generate print parameters. These parameters can be entered into standard 3D printing software and used to print with the new material.

The scientists demonstrated their method by setting printing parameters for six different machine and material combinations and then printing the different models shown here.

Automation of parameter settings

Automatically generated settings can replace about half of the settings that typically need to be configured manually. In a series of test prints using unique materials, including several renewable resources, the researchers demonstrated that their method was able to consistently generate viable parameters.

This research could help reduce the environmental impact of additive manufacturing, which typically relies on non-recyclable polymers and resins made from fossil sources.

“In this paper, we demonstrate a method that can take all these interesting materials that are bio-based and made from a variety of sustainable sources, and show that the printer can figure out how to print with those materials. The goal is to make 3D printing more sustainable,” says senior author Neil Gershenfeld, who heads the CBA.

Its co-authors include lead author Jake Reed, a CBA graduate student who led the development of the printer; Jonathan Seppala, a chemical engineer in NIST's Division of Materials Science and Engineering; Philippos Tourlomousis, a former CBA postdoc who now heads the Autonomous Science Laboratory at Demokritos; James Warren, who heads the Materials Genome Program at NIST; and Nicole Bakker, CBA Fellow. The study was published in the journal Integrating Materials and Manufacturing Innovation.

Changing Material Properties

In Fused Fused Process (FFF), which is widely used for rapid prototyping, molten polymers are pressed through a heated nozzle layer by layer to create a part. Software called a slicer gives the machine commands, but it must be configured to work with a specific material.

Using renewable or recycled materials in an FFF 3D printer is especially challenging because there are many variables that affect the properties of the material.

For example, a biopolymer or resin may contain different plant components depending on the time of year. The properties of recycled materials also vary significantly depending on what materials are available for recycling.

“In the movie Back to the Future, there's a Mr. Fusion blender where Doc just throws everything he's got into and it works. [как источник энергии для машины времени ДеЛориан]. Same idea here. The ideal thing to do with plastic recycling is to simply shred what you have and print with it. But that doesn't work with current systems because if your filament changes significantly during printing, the whole thing will break,” says Reed.

To overcome these challenges, scientists have created a 3D printer and workflow that can automatically determine the optimal parameters for any unknown material.

They initially used a 3D printer their lab had previously developed that was capable of collecting data and providing real-time feedback. To this printer, the researchers added three extruder devices to measure the parameters needed for their calculations.

The strain gauge records the pressure on the printed material, and the feed rate sensor measures the thickness of the material and the actual speed at which it passes through the printer.

“This integration of measurement, modeling and manufacturing is at the core of the collaboration between NIST and CBA as we develop what we call 'computational metrology,'” Warren says.

This data can be used to calculate two key but difficult to determine printing parameters: feed rate and temperature. Almost half of all printing settings in standard programs are related to these parameters.

Creating a Dataset

After implementing the new instruments, the scientists created a 20-minute test that takes a series of temperature and pressure measurements at different flow rates. The main content of the test is that the printer nozzle is heated to maximum temperature, the material is supplied at a constant speed, after which the heater is turned off.

“It was really difficult to figure out how to make this test work. Trying to find the limits of the extruder means that you will often break the extruder during testing. The concept of turning off the heater and just passively collecting data was that 'aha' moment,” Reed says.

This data is fed into a function that automatically creates precise parameters for the material and device configuration based on the temperature and pressure values ​​entered. The user can then use these parameters in the 3D printing software and generate commands for the printer.
In experiments with six different materials, including some of biological origin, the method automatically generated workable parameters that consistently ensured the successful printing of complex objects.

In the future, the researchers intend to combine this process with 3D printing software to eliminate the need to manually enter parameters. In addition, they aim to improve their workflow by incorporating a thermodynamic model of the printer hot block that melts the filament.

The collaboration is now more intensively developing computational metrology, where the measurement result is a predictive model rather than just a parameter. The researchers plan to use this in other areas of advanced manufacturing, as well as to expand access to metrology.

“By developing a new method to automatically generate process parameters for fused extrusion, this research opens the door to the use of recycled and bio-based filaments with variable and unknown properties. Importantly, this increases the potential of digital manufacturing technology to use local, sustainable materials,” says Alicia Garmulevich, an assistant professor at the Faculty of Management and Economics at the University of Santiago in Chile, who was not involved in this work.