A novel technique has been developed that allows creators to precisely adjust the color, shade, and texture of 3D-printed items using just a single material. This new approach is not only quicker but also requires less material compared to traditional methods.
Multimaterial 3D printing facilitates the creation of uniquely designed items with various colors and textures. However, this process can be tedious and lead to material waste, as current 3D printers often need to switch between multiple nozzles, frequently disposing of one material before starting with another.
Researchers from MIT and Delft University of Technology have introduced a more effective and less wasteful technique that uses heat-sensitive materials to print multicolored and textured objects in a single process.
This technique, known as speed-modulated ironing, employs a dual-nozzle 3D printer. The first nozzle applies a heat-responsive filament, while the second nozzle moves over the printed surface to initiate specific reactions, such as alterations in opacity or surface texture, through applied heat.
By regulating the speed of the second nozzle, the researchers can generate precise temperature adjustments, allowing them to finely alter the color, shade, and texture of the heat-sensitive filaments. Notably, this method does not necessitate any hardware changes.
The research team developed a model that forecasts the amount of heat transferred by the “ironing” nozzle depending on its speed. This model served as the basis for a user interface that automatically produces printing instructions to meet specific color, shade, and texture requirements.
Speed-modulated ironing can be used to create artistic effects by varying colors on a printed item. Additionally, this technique can design textured handles for better grip, especially useful for individuals with weakened hand strength.
“Currently, desktop printers use a clever combination of a few inks to create various shades and textures. We aim to replicate this with a 3D printer by utilizing a limited range of materials to achieve a broader spectrum of features in 3D-printed items,” explains Mustafa Doga Dogan PhD ’24, a co-author of the speed-modulated ironing study.
This project is a collaboration between Zjenja Doubrovski’s research team at TU Delft and Stefanie Mueller’s group at MIT, who serves as the TIBCO Career Development Professor in the Department of Electrical Engineering and Computer Science (EECS) and is also affiliated with the MIT Computer Science and Artificial Intelligence Laboratory (CSAIL). Dogan closely collaborated with lead author Mehmet Ozdemir from TU Delft, along with Marwa AlAlawi, a mechanical engineering graduate student at MIT, and Jose Martinez Castro from TU Delft. The findings will be shared at the ACM Symposium on User Interface Software and Technology.
Adjusting Speed for Temperature Control
The research team initiated the project to discover enhanced methods for achieving multiproperty 3D printing with just one material. While the concept of using heat-responsive filaments showed promise, most conventional techniques rely on a single nozzle for both printing and heating, requiring the nozzle to heat up to the needed temperature before beginning material deposition.
However, the process of heating and cooling the nozzle is time-intensive, and there is a risk that the filament may degrade at elevated temperatures.
To address these issues, the researchers created an ironing technique where the material is printed using one nozzle and then activated with a second, empty nozzle that solely reheats it. Rather than adjusting the temperature to trigger the material’s response, the team maintains a constant temperature for the second nozzle while varying its speed above the printed layer.
In speed-modulated ironing, the primary nozzle of the dual-nozzle 3D printer applies a heat-responsive filament, and the second nozzle lightly moves over the printed area to trigger responses like changes in opacity or texture through heat. “By modulating the speed, we enable the layer being ironed to reach different temperatures. This is akin to moving your finger quickly over a flame; if you go fast, you won’t burn yourself, but if you linger, you’ll get too hot,” AlAlawi explains.
The MIT team collaborated with TU Delft researchers to formulate the theoretical model that predicts the necessary speed of the second nozzle to achieve specific temperature conditions for the material.
This model connects a material’s resulting temperature with its heat-responsive properties, determining the precise nozzle speed required for creating distinct colors, shades, or textures in the finished product.
“Numerous variables can influence the outcomes we achieve. We are modeling a complex system but aspire to ensure the results are finely detailed,” AlAlawi remarks.
The team explored scientific literature to find appropriate heat transfer coefficients for a range of specialized materials, integrating these findings into their model. They also had to navigate an array of unpredictable factors, such as heat dissipated by fans and the ambient temperature in the printing area.
The model was embedded into a user-friendly interface that streamlines the scientific process, transforming the pixels in a designer’s 3D model into machine instructions that regulate the printing and ironing speeds of the dual nozzles.
Rapid, Precise Production
The team tested their technique with three types of heat-responsive filaments. The first was a foaming polymer with particles that expand when heated, leading to various shades, transparencies, and textures. They also experimented with a filament infused with wood fibers and one containing cork fibers, both of which can be charred to create deeper shades.
The researchers showcased how their technique could be used to create partially translucent objects like water bottles. To manufacture these bottles, they controlled the ironing of the foaming polymer at low speeds for opaque areas and at higher speeds for translucent regions. They also used the foaming polymer to design a bike handle with assorted textures for better grip.
In contrast, creating similar items through conventional multimaterial 3D printing took significantly longer, often adding hours to the process while consuming more energy and materials. Moreover, speed-modulated ironing could achieve delicate gradients in shade and texture that other methods couldn’t replicate.
Looking ahead, the researchers intend to explore additional thermally responsive materials, such as plastics. They also aspire to investigate the potential of speed-modulated ironing to alter the mechanical and acoustic properties of certain materials.
