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Additive Manufacturing in Space

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Additive Manufacturing in Space

  1. 1. 1 Arvind Srinivasan Karthikeyan Parameters to be considered for in-space manufacturing  Vacuum of space  Zero gravity  Intense thermal fluctuations  Extreme and harsh environmental obstacles  Cost  Human oversight  Consistent production quality  Standardizing design software  Equipment parameters  Testing standard  Understanding of material properties in space and their structural properties Figure 1:Energy Consumption of different AM processes Techniques Sheet Lamination  Possible to work under microgravity.  With the tension from two of rolls on each side of the device.  Does not need human interference to feed the stock. Can be automatically fed.  Limited on type of materials and size of material. Material Extrusion  This method has already been employed for 3D printing in space.  Ease of feeding the stock due to the solid form of filament and the size used was 1.75 mm.  Offers good resolution of up to 40 microns.  It is cheap and the equipment is light weight  It has printing dimensions of 25 x 25 x 25 cm3  Power consumption less than 100 W.  But it has limitations on materials since it cannot print Teflon, PEEK or nanocomposites that are used in space and steps are also taken to improve the layer resolution. Figure 2:Layer thickness of FDMfabricated parts over different gravity
  2. 2. 2 Arvind Srinivasan Karthikeyan VAT Photo polymerization  Can be used for in-space manufacturing by modifying certain parameters to suit the conditions prevalent is space.  Size is not a constraint and this is the preferred method for polymers since the post processing method is relatively simpler and pollution-free.  Polymers could be recycled and used again. Makes a viable resource for repair spare parts.  Only constraint is to hold the liquid under gravity Material Jetting  They can be used for finding a suitable method to hold liquid under gravity. Similar to VAT polymerization and major advantage of this method is producing multiple part materials which are in heavy demand for in-situ fabrication.  However, ability to not produce high strength and durability metal parts might be a constraint so the probability of preferring this type is lower. Powder Bed Fusion  Can be used if a binder can be used to hold the powder together in a sheet and this sheet could be fed continuously after a layer of sheet has already been cured. By doing this, complication of powders spreading everywhere could be avoided.  Implementation the above stated method is a huge challenge Printing Method Plastic or Metal Zero Gravity Capability Vacuum Compatibility Materials Min Layer Thickness BuildVolume Feasibility Sheet Lamination Either High Yes Paper, Plastic, Sheet Metal 100 µ 21 x 25 x 40 cm3 High Material Extrusion Plastics Material Dependent Partial ABS, Polycarbonate, PC- ABS 100 µ 25 x 25 x25 cm3 High VAT Photo- Polymeriza tion Plastics Low Not by conventional methods ABS, Polycarbonate, PC- ABS 50 µ 180 x 160 x 210 cm3 Medium Material Jetting Plastics Material Dependent No Wax and Plastics 16 µ 30 x 18.5 x 20 cm3 Low Powder Bed Fusion Metals and Plastics Low Yes Metals, alloys, polymers. 60-100 µ 55 x 55 x 75 cm3 Low Table 1: Comparison of all method parameters
  3. 3. 3 Arvind Srinivasan Karthikeyan Structural Application We can observe that a major number of failures associated with space travel is with electrical & electronic components and with Plastic and Composite materials. Our choice of application revolves around Plastics and Composites as they make up over a quarter of the total hardware failure; also plastics and composites are recyclable in nature. Since a lot of accessories in a space mission are made of plastic including buckles, clams and containers; it becomes critical to ensure their renewability in-situ. To tackle this, we propose use of VAT Photopolymerization technique with a Two Photon approach for additive manufacturing of these Plastics and Composites. Concept:  The two-photon approach involves intersecting two separate arrays of photons in the VAT filled with polymer. The 3-dimensional vector traced by this point of intersection of the two arrays will form a solid material within the VAT.  This allows us to hold a photopolymer liquid in a sealed transparent chamber without any recoating or surfacing.  The transparent chamber will consist of each an inlet and an outlet and a face plate.  The face plate will be attached to the chamber; the outlet will depressurize the chamber whilst keeping the inlet close. Once vacuum is achieved the inlet will be let open to allow the photopolymer to be sucked inside the chamber.  Two arrays of photon will cure the material as per the CAD file within the VAT.  Once the part is completed the remaining resin is sucked out of the outlet.  The chamber is repressurized and removed from the faceplate to expose the created part.  This part can be further cured in a UV oven to achieve the desired properties. This process is a minor tweak over the conventional process of SLA. The incident lights hold energy lower than the critical energy required for photopolymerization. The intersection where both lasers meet collectively provide energy which exceeds the critical energy and start curing the resin. Figure 3: Representation of total failures in ISS by material type Figure 4: Illustration of the proposed process
  4. 4. 4 Arvind Srinivasan Karthikeyan An alternate approach to SLA in zero gravity could be made by artificially creating the effect of gravitational pull. This is acieved by making the machine experience centripital acceleration. The International space station was intended to contain a Centrifuge Accomodations Module which could provide controlled acceleration rates (artificial gravity) for experiments. Such a Module would allow our SLA machine to function with very little modification to the actual design. This setup however would pose a challenge as the liquid reservoir will not simply lie flat within in its container while it is being spun out, the water surface will for a concentric arc to the path of the spin. This concave shape of the liquid must be controlled, if it is too extreme the printer won't behave correctly. The figure to the right illustrates this situation. We can calculate the difference in the heights of the concave curvature by using trigonometry. ( 𝑅 − ∆ℎ)2 + 𝑋2 = 𝑅2 Which can be rewritten as ∆ℎ = 𝑅 − √ 𝑅2 − 𝑋2 Taking 𝑅 = 1.25 𝑚 (The proposed capsule for ISS was 2.5 m) 𝑋 = 0.0625 𝑚 (The width of Form1 is 12.5cm) From the data obtained in fugure 6 it is reasonable to assume that if the printer is allowed to rotate at a radius of at least 0.7 meters, where the height difference between the fluid is less than 3mm that the printer would be capable of operating in a micro-gravity setting. These measures would allow to manufacturing of certain components in space. However these parts would be subjected to further scrutiny and testing. Figure 5: Schematic representation of Centrifuge Accommodations Module. Figure 6: Fluid Height vs Radius of rotation from the given calculations.
  5. 5. 5 Arvind Srinivasan Karthikeyan References "Centrifuge Accommodations Module". En.wikipedia.org. N.p., 2016. Web. 28 Nov. 2016. https://en.wikipedia.org/wiki/Centrifuge_Accommodations_Module Glenn, Valerie D. "NTRS: NASA Technical Reports Server200695ntrs: NASA Technical Reports Server. Washington, DC: National Aeronautics And Space Administration 1994‐ . Gratis Last Visited July 2005 URL: Http://Ntrs.Nasa.Gov/". Reference Reviews 20.2 (2006): 40-41. Web. Kopchak, Obadiah and View profile. "Can Stereo Lithography Printing Work In A Microgravity Environment". Myspareideas.blogspot.com. N.p., 2016. Web. 23 Nov. 2016. "Projects". Made In Space. N.p., 2016. Web. 22 Nov. 2016. Richards, Louise M. "NASA Technical Reports Server (NTRS)2008364NASA Technical Reports Server (NTRS). Washington, DC: NASA Center For Aerospace Information Last Visited June 2008. Gratis URL: Http://Ntrs.Nasa.Gov/". Reference Reviews 22.8 (2008): 40-41. Web. "Sheet Lamination | Additive Manufacturing Research Group | Loughborough University". Lboro.ac.uk. N.p., 2016. Web. 24 Nov. 2016. Ordway, Frederick I. and R. E. Street. "Advances In Space Science And Technology, Volume 3". Physics Today 15.3 (1962): 60. Web. Lee, Kwang-Sup, et al. "Two-photon stereolithography." Journal of Nonlinear Optical Physics & Materials 16.01 (2007): 59-73. Wong, Julielynn Y., and Andreas C. Pfahnl. "3D printing of surgical instruments for long- duration space missions." Aviation, space, and environmental medicine 85.7 (2014): 758-763. Chandrasekhar, Prasanna, et al. "Variable emittance materials based on conducting polymers for spacecraft thermal control." SPACE TECHNOLOGY AND APPLICATIONS INT. FORUM-STAIF 2003: Conf. on Thermophysics in Microgravity; Commercial/Civil Next Generation Space Transportation; Human Space Exploration; Symps. on Space Nuclear Power and Propulsion (20th); Space Colonization (1st). Vol. 654. No. 1. AIP Publishing, 2003.

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