VOX3:
STEREOLITHOGRAPHIC 3D PRINTER

PROCESS

VOX3 is a stereolithographic 3D printer with a voxel-based workflow. Stereolithography, or SLA, 3D printing uses a photosensitive liquid polymer to create hardened layers of material. Whereas laser SLA exposes each layer by tracing the outline of the part with a laser, projector-based SLA exposes a single layer all at once. This process is most similar to the Formlabs desktop 3D printing process.

WORKFLOW

The unique aspect of the VOX3 is a voxel workflow based on the NVIDIA Jetson TX2. A typical workflow for 3D printing is to model a part with polygons, then load the part on a CPU host which performs voxelization and then generates either G-code or the slice images required for SLA printing.

By running GVDB Voxels on the Jetson TX2, we are able to perform advanced processing in the printer itself. The Jetson TX2 has dual video outputs, enabling it to run the slice projector and a preview monitor. Using 256 parallel CUDA cores, the Jetson TX2 can process polygonal and voxel models on the device. This workflow implies the ability to transmit, process, in-fill and slice volumetric data directly on the 3D printer.

The VOX3 workflow allows for live processing of the part during printing. Although not used in our prototype, feedback from the printer via cameras and sensors could be sent to the Jetson to make live adjustments. Additionally, re-processing can be performed since the VOX3 has full access to the original and voxelized model in printer memory. In our demo the VOX3 takes a polygonal model as input, performs full, high resolution voxelization to a sparse 3D volume, and computes each cross sections on-the-fly as needed for projection while printing.

DESIGN & CONSTRUCTION


Figure 1. Frame assembly

The VOX3 was designed as an experimental prototype. The process of bottom-up SLA printing requires a projector, a built tray, a moving build platform and a mold release mechanism. Figure 1 shows the basic frame assembly. The Z-axis and build platform are controlled with a leadscrew and a 1A stepper motor. The front mounted motor is used to tilt the build tray after each printed layer.


Figure 2. First projection test

With the frame designed as two stacked aluminum cubes, the projector is mounted in the lower cube and points upward at the build tray. Figure 2 shows the first projection test.


Figure 3. Completed VOX3 printer

The completed 3D printer is shown in Figure 3 with the Jetson TX2 (panel top left), and a Smoothieboard (panel bottom left) which controls the two stepper motors. Special UV transparent glass (center) is required so that the projector light has sufficient power density to polymerize the SLA liquid. The build tray holds the liquid, not shown in this photograph.

RESULTS



The VOX3 was exhibit at the 2017 GPU Technology Conference as part of the NVIDIA display on Optimized 3D Printing with the GVDB Voxels software. Since resin printing can be messy and requires refilling, the display was operated in demo mode which shows the moving printer head and 3D slices computed in real-time.


Also exhibit were 3D printed parts made by Voronoi in-filling with GVDB Voxels. The Lucy model was printed as both a solid part and with voronoi filling to demonstrate weight reduction computed interactively and entirely with voxels.

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