INFORMATION TECHNOLOGY

Spiral volumetric additive manufacturing


Volumetric Additive Manufacturing (VAM) technology can quickly manufacture complex three-dimensional objects at a very low cost, bringing unprecedented development and changes to light-based 3D printing technology, attracting widespread attention in many fields such as aerospace and biomedical.

In the printing process, the use of computational axial lithography (CAL) technology, the target 3D object into a 2D light pattern in different directions, through the digital micromirror device (DMD) dynamic 2D light pattern from multiple angles irradiated liquid photosensitive resin volume, when all the target voxels in the liquid receive an irradiation dose above this threshold. Achieve light curing of the target three-dimensional object.

Recently, Professor Christophe Moser’s team from the Ecole Polytechnique in Lausanne, Switzerland, published a research paper entitled “Volumetric helical additive manufacturing” at Light: Advanced Manufacturing.

In this paper, the researchers proposed a method to realize spiral volume additive fabrication of centimeter-level structure without magnifying the projection pattern, effectively increasing the height of the printable object (3 times), and expanding the horizontal size of the printable object by 2 times by deviating from the design of the center of the projection light pattern, and finally realizing the rapid printing (<10min) of large objects (3cm×3cm×5cm) and fine details (650μm). As shown in Figure 1, the investigators combined rotational and linear translational movements during VAM printing to set glass vials containing photosensitive resin to spiral motion. Unlike conventional VAM printing, which irradiates all resin areas at once, during the printing process of volumetric helical additive manufacturing (VHAM), glass bottles containing photosensitive resin are fully activated after a complete bottom-up and top-down spiral movement. Therefore, there are some overlapping areas between the patterns, which can be fine-tuned by adjusting the rotation speed of the resin bottle to accommodate the vertical movement of the translation phase to ensure the continuity of the printed object.

Figure 1: Schematic diagram of how VHAM works. Source: Light: Advanced Manufacturing 4, 12 (2023)

In chromatographic VAM, the optical resolution determines the size of the printable voxels, which is usually determined by the DMD used to generate the patterned light field. For this work, the team used Texas Instruments’ DLP7000 chip, which has 768×1024 miniature mirrors on its surface, arranged into a rectangular array capable of displaying an 8-bit image. The researchers enlarged the DMD image by a factor of 1.66 and finally obtained a 2D light field pattern with a size of 1.74 cm × 2.33 cm and a resolution of 23 μm on the resin bottle.

Further, the researchers demonstrated the feasibility of using a spiral trajectory to move the sample around the beam through simulations and experiments. In this process, the transverse printable size can be doubled without compromising resolution by centrifuging the optical axis relative to the axis of rotation of the photosensitive resin barrel.

With the above two methods, the number of building blocks for VAM manufacturing in the resin bottle can be increased by up to 12 times, and large objects with a maximum size of 3cm× 3cm× 5cm can be printed in minutes. Figure 2 shows a 3D printed sample that takes only a few minutes to mold.

Figure 2: VHAM printing example. Source: Light: Advanced Manufacturing 4, 12 (2023)

In summary, the team proposed and validated a new spiral volumetric printing technology that can be used to rapidly manufacture centimeter-sized objects. The technique extends on chromatographic VAM to significantly increase the number of printable voxels without significantly affecting the print resolution by centrifuging the optical modulator and continuously translating the resin along the vertical direction of the patterned beam, as shown in Figure 3. At the same time, these simple extensions can be easily compatible with existing chromatography VAM printing equipment, which opens up new possibilities for high-resolution and high-speed fabrication of large structures with centimeter-level dimensions. (Source: Advanced Manufacturing WeChat public account)

Figure 3: Device and print volume comparison of conventional chromatographic VAM and spiral VAM. Source: Light: Advanced Manufacturing 4, 12 (2023)

Related paper information:https://doi.org/10.37188/lam.2023.012

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