SPACECAL Research Project Report

Design for Manufacturing, Taylor Labs, University of California, Berkeley

Authored by Tristan W Schwab, Undergraduate of Mechanical Engineering April 30, 2021

The scope of this report is to discuss the progress of the SpaceCAL Project aimed towards the Zero-Gravity flight test in the Spring of 2022 and my contributions to the project and Design for Manufacturing Group during the Spring semester of 2021.

Figure 1

NASA Tech Flight Proposal

The purpose of SpaceCAL is to develop a compact enclosure containing 5 parallel computed axial lithography (CAL) printers to be tested in suborbital testing with the Zero-Gravity Flight Demonstration. The system is projected to fly in the Spring of 2022 and complete several varying viscosity resin prints.

SpaceCAL is inherently a technology demonstration of the current CAL technology developed at the University of California, Berkeley in microgravity; however, alternative scopes of research may apply. Suggestions have been raised to the enhancement of research in additive manufacturing for in space manufacturing, including: 1) Part strength versus fluid velocity through shadowgraph analysis in resin vials. 2) In situ automated post-processing of CAL prints. 3) Testing of a temperature control system in a space environment for low-gravity resin printing. 4) Tracking low-viscosity polymerization in low-gravity. 5) Performance of CAL for micro-gravity bioprinting.

The SpaceCAL project can ultimately demonstrate not only the unique abilities of CAL AM technology but shows potential to provide invaluable research in the growing field of in-space manufacturing.

As mentioned, the SpaceCAL project is scheduled to fly in the Spring of 2022 (next year). During the launch of the project in January, primary focus has been development of an enclosure to contain the CAL system, electronics, optics, and hardware considerations, and the design of a compact and exchangeable vial stack (fig. 1, right). The planned design has evolved since the initial Flight Tech Proposal. First, original documentation discussed three sets of vial stacks, containing 22 hydrogels, 11 high, medium and low viscosity resins. The current design now contains 5 vial stacks of 5 vials each. Change of the number of vial stacks and vials affects the number of resins which will be used in flight. Second, the project will no longer consider the use of “Schlieren imaging to record video data of the refractive index history”, but rather, Shadowgraph methods due to the high sensitivity of Schlieren imaging.

Current State of SpaceCAL and Contributions

SpaceCAL exists in an early design stage on Solidworks. Full purchase orders for the primary assembly include hardwire, including but not limited to 8020 beams, linear guide rails, projectors, optics, and electronics.

The author was established as the Mechanical sub team lead, tasked with rebuilding the first iteration of the SpaceCAL system on Autodesk Fusion 360. The author rebuilt an 8020 enclosure (Frame Assembly) and performed finite element analysis on Fusion 360 to analyze g-loads on the frame specified by Zero-Gravity.

The author used these analyses to confirm the material selection of the frame assembly and add triangulated supports the frame.

Progress then shifted to rebuilding the SpaceCAL system on Fusion 360 (due to the limited capabilities of Fusion 360 and parametric modeling). The author collaborated with Grad Student Lead, Joe Toombs, to develop a parametric sketch in Solidworks and develop the second version frame assembly. Current focus has now turned to the development of optic setups for particle tracing, continuing summer research positions in the Design for Manufacturing group, assembling the SpaceCAL system, and collaborating with fellow future Cal Grad Student, Taylor Waddel, on mechatronics and software. Future project objectives are expected to shift towards resin formulation and characterization.

The SpaceCAL project certainly arrives at a remarkable time for the College of Engineering at Berkeley to be involved in the growing excitement for exploration and industry in space.

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