A Tomographic Volumetric Additive Manufacturing. b Helical tomographic volumetric additive manufacture. Scale bars: 10 mm.
FAYETTEVILLE, GA, USA, July 26, 2023/EINPresswire.com/ — 3D printing has revolutionized the manufacturing of volumetric components and structures for various fields. Recently, several fully volumetric light based techniques were developed to push the current limits. The proposed method is a volumetric helical additive manufacturing (VHAM), which produces multi-cm-scale structures without magnifying projected patterns. This movement allows to increase the printable object’s height. The object’s lateral dimensions are doubled when the modulator for generating the light patterns is off-centered.
In the past decade, 3D-printing technologies have undergone unprecedented changes and developments. The 3D printers allow for the rapid fabrication of complex objects in three dimensions at very low cost. 3D printers are therefore particularly relevant and attractive for many fields including aerospace or medical devices.
Up until recently, 3D printing using light or additive manufacturing (AM) relied primarily on a vat filled with liquid photopolymer. A UV light beam cures resin in layers, while a platform moves down the object after each layer has hardened.
UV light can either be raster scanned onto the resin to solidify it point-by-point or flashed onto it at the same time. These light-based AM methods are limited by their geometrical constraints and throughput due to the nature of printing, which is layer-by-layer.
In a new paper published in Light: Advanced Manufacturing, a team of scientists led by Professor Christophe Moser from Ecole Polytechnique Fédérale de Lausanne have developed a new technique for improving the quality of 3D-printed items without magnifying the projected patterns.
In the past few years, we have seen several technologies for Volumetric Additive Manufacturing that do not use the layer-bylayer method. The two-photon-photopolymerization is the current state of the art in volumetric light printing. It allows the fabrication microscale objects that have a lateral resolution of 100nm and an axial resolution of 300nm. However, this process is slow, with a printing speed of just 1–20 mm3/h and requires expensive femtosecond laser sources.
In the end, the optical voxel resolution of a printer determines what can be printed. In DLP and VAM tomographic, optical resolution can be determined best by the DMD.
The research team used a DLP7000 chip from Texas Instruments that has on its surface Nx × Ny = 768 × 1024 micro-mirrors arranged in a rectangular array capable of displaying 8-bit images. In the team’s optical setup, the DMD image has been magnified by 1.66. The resulting pattern on the vial is 1.74 cm × 2.33 cm with a resolution of 23 μm.
Only by moving the DMD from the vial, or vice versa, can you increase the print size without compromising on the resolution. The team suggested moving the sample in a helical path around the beam of light. The team demonstrated that the printable lateral size could be increased without compromising the resolution by decentering the optical axis relative to the rotational axis of a photoresin vat.
These two tricks can increase the number in the vial of the building blocks by up to 12 times. The available printed voxels are used to print larger objects up to 3 cm × 3 cm × 5 cm in a few minutes.
The team of researchers has used a combination of a rotating stage and a translation stage to move the vial with the photoresist helical. Researchers pointed out that the entire resin was not lit at once, as it is in tomographic conventional VAM. In VHAM the resin is only fully excited after one cycle.
After a full turn, the upper and lower parts of the pattern will coincide. The size of the overlap is fine-tuned by adjusting the vial’s rotation speed to the vertical movement of the translation stage, which is essential to ensure continuity of the printed objects.
The team presented a proof of concept of a light-based volumetric printing technique that can print objects in multicentimeter size. The technique builds on the tomographic VAM in order to increase the number printable voxels, while maintaining the same projection device and without compromising the printing resolution. This was accomplished by off-centering a light modulator, and translating the resin along the pattern light beam continuously.
These simple modifications can be easily made on existing tomographic printers and opens up new possibilities for high-resolution and high-speed fabrication of objects whose size up to 3 cm × 3 cm × 6 cm. Helical tomographic VAM may be appealing in applications where objects of cm-scale must be individually manufactured, such as the dental industry.
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References
DOI: 10.37188/lam.2023.012
Original Source URL: https://www.light-am.com/article/doi/10.37188/lam.2023.012
Funder
This work was supported by the Swiss National Science Foundation under project number 196971 – “Light-based Volumetric printing in scattering resins” European Union’s Horizon 2020 research and innovation programme under grant agreement No 964497. The authors would like to thank all the open-source and free tools that were used for this project, such as Tinkercad.com. FreeCADweb.org. Inkscape.org. Python.org. PyTorch.org. Thingiverse.co.
Article Publication Date: 16 June 2023
About Light: Advanced Manufacturing (LAM)
Light: Advanced Manufacturing (LAM) is a new, highly selective, open-access, and free of charge international sister journal of the Nature Journal Light: Science & Applications. The journal is dedicated to publishing innovative research in modern areas of light-based preferred manufacturing, including both fundamental and applied research as well as industrial innovations.
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