Present. SOFE '17 China: Talk in SOFE Symp 2017 Prospects for stellarators based on additive manuf

1. 1 Prospects for stellarators based on additive manufacturing Dr. Vicente Queral, S. Cabrera, Dr. E. Rincón, L. Rios National Fusion Laboratory, CIEMAT, Spain 27th IEEE Symposium on Fusion Engineering (SOFE) Shanghai, China 8 June 2017

2. 2 ● Background ● Additive Manufacturing (AM) studies for coil frames ● AM studies for vacuum vessels ● Advantages and drawbacks of AM for stellarators ● Future concepts. Conclusions Outline

3. 3 Background Work performed under grant ENE2015-64981-R, project ‘Study of Additive Manufacturing for the application to high performance fusion devices of stellarator type’, funded by the Spanish ‘Ministry of Economy, Industry and Competitiveness’. One objective of the work is to contribute to the construction problem of stellarators, particularly by Additive Manufacturing (AM). Importance. It may accelerate the production cycle of stellarators and thus, faster advance fusion plasma science.

4. 4 High geometrical complexity of the devices, at high accuracy Casting and milling. NCSX (left), W7-X (right) Problem. Previous solutions Background Stellarator Contorted plasma for advanced stellarators Casting and milling, CTH Other coil disposition [PPP 07] [Har 03] [Ris 03]

5. 5 Geometrical complexity + accuracy Background Toroidal milling machine, UST_1 stellarator • Explosive forming, HSX • Cold forming, NCSX. • Hot forming, W7-X. Vacuum Vessels HSX VV sector SCR-1 stell. Aluminium casting of groove walls from AM patterns V. Queral design Problem. Previous solutions

6. 6 AM of plastics or metals Formwork [Web 15] Combination of both?, What about windings? New fabrication methods for coil supports Casting + machining is reliable, accurate, strong materials, but long production cycle and somewhat expensive Typical traditional method AM + composite casting of short-fibre reinforced resin Potential new methods Kind of AM. Laminated composite with auto- mated placement [Web 17] [Naj 05]

7. 7 SLA Stereo- lithography SLS PolyJet Hints about Additive Manufacturing Some relevant AM types Selective Laser Sintering Fusion Deposition Modelling

8. 8 AM studies for coil frames

9. 9 Methods ▪ Enough accuracy (0.1% accuracy or higher, relative to the major radius) has to be proved by AM parts. It is a critical factor for coil frames. ▪ AM coils frames and casings were produced in different materials and using the four AM techniques. Finally measured by a Coordinate Measuring Machine Coordinate Measuring Machine ▪ Different high quality companies and 3D- printers were selected.

10. 10 Study of dimensional accuracy of AM frames Second assays: FDM (ABS plastic), deviations ~ 0.1% for 68% [Que 16]. PolyJet: Warping First assay: SLS, Polyamide 12, deviation <0.3% for 68% of measures, 1σ SLS FDM Deviation from the measured points to model, for SLS part

11. 11 SLA, resin, Mean deviation ±0.18%, deviation < ±0.27% for 68% of measures. Study of dimensional accuracy of AM frames FDM, ABS, mean deviation ±0.17%, deviation <±0.28% for 68% of measures. PolyJet part: Thermally instable, part was distorted. Third assays: Scaled coils frames 1/2

12. 12 + Short-fibre resin casting in the internal volume. Feasible strength of 100 MPa, right for bulky structures AM hollow shell with internal truss structure (a surface removed for vision) Assay of 3Dformwork fabrication method

13. 13 Shell filled with acrylic resin (3Dformwork), 20–25 MPa, ~ 1000 €, 0.3% 1σ deviations ~ 350 mm

14. 14 Assembly process Vacuum vessel inside half coil frame Two halves of the coil frame Closure with the second half coil frame. Modular vacuum vessel. Satisfactory result

15. 15 Recording of one e-beam experiment (video). Experimental fluorescent points agree with calculations. Satisfactory result. e-beam validation

16. 16 AM studies for vacuum vessels

17. 17 Liner + external claws AM mould for epoxy casting on liner Finished VV sector. Copper liner reinforced by epoxy resin. Study A: Metallic liner reinforced resin ~ 300 mm Plaster Form (SLS mould) for shaping AM mould to apply resin as reinfor-cement of the liner

18. 18 Study B: Thin electroforming & ext. reinforc. 1. Extract mandrel + cleaning 2. Flange attachment 3. External epoxy reinforcement (if thin electroformation) Cu electrodeposition (0.3-0.5 mm thick Cu layer) Conductive paint (graphite and silver) Moulded wax mandrel in an AM mould Electroformation of thin layer on conductive- painted mandrel (not able for 1 bar pressure), externally reinforced by resin ~ 150 mm

19. 19 Assembled sector of VV shell under vacuum test SLA 3D-printed internal surface of shell SLS 3D-printed mould for external resin reinforcement Internal metallic film deposition (PVD, electrodeposition electroless or …) 3D-printed shell and internal metallic film Or Internal metallic film deposition ~ 300 mm Study C: electrodeposition on AM shapes

20. 20 Thin copper electrodeposition ~ 10 – 100 µm. Why such studies and not standard methods? • Facilities for metallisation of large plastic components are scarce and complex steps → expensive. • Facilities for large PVD parts are scarce and thin film → expensive • Thick electroforming is difficult → expensive. Improvements needed for such low cost methods • Roughness of painted surfaces should be improved. • Find simple-fabrication attachment claws/roughness for good metal-resin bonding. ~ 300 mm Study C: electrodeposition on AM shapes

21. 21 Advantages and drawbacks of AM for stellarators

22. 22 • Feasible numerous coils, of small curvature radius, of high complexity. Thus, any magnetic configuration possible, with low magnetic errors. • AM of all the complex elements on a sole part (winding positioning, supports, stops, etc.), thus, agile assembling. • Fast production cycle of devices. • Feasible combination with traditional fabrication methods like fibre-resin casting, laser/water jet cutting. AM advantages for stellarator application

23. 23 AM drawbacks for stellarator application • Low dimensional accuracy. Measured dimensional accuracy (without milling) <±0.17%, still higher than min. required ±0.1% for stellarators. • Low strength of AM plastics (though rather accurate). • AM of metals: Small size of commercial 3D- printers, high price per cm3, currently appears too inaccurate, though high strength. Seems now uncompetitive with metal casting+milling. • Direct AM of windings (high conductivity Cu or Al) still difficult or expensive.

24. 24 Future concepts Conclusions

25. 25 • Large DMLS (Direct melting Laser Sintering) with experimental printers (not commercial yet, accuracy?). • 3Dformwork using liquid metals, Zamak, BiSn,… (issues: deformation, only some materials, large metal printer and supports, etc.). Possibilities for metal parts AM large titanium part. China, [AVI 13] Metal 3Dformwork?

26. 26 Plan, build a stellarator of Vp ~ 2 m3 of features: Application to a future stellarator • High-field ~ 4T • Thick copper. • Variable section coils, small ports. Perhaps automatic laminated composite (>1000 MPa)

27. 27 Conclusions ▪ Additive manufacturing is at the verge of achieving enough accuracy (0.1%) for the main components of stellarators (coil frames). ▪ Engineering designs conceived particularly for AM may give extra advantages (simpler assembling ~ complexity on one piece, ↓ modular ripple ~ many coils, etc.). ▪ Additive manufacturing (combined with other fabrication methods) appears promising to build, already today, certain modest experimental stellarators, quick and at moderate cost. ▪ It may be relevant to accelerate the production and experimental cycles in fusion.

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30. 30 [Alm 98] A. F. Almagri, D. T. Anderson, S. F.B. Anderson, et al., Design and Construction of HSX: a Helically Symmetric Stellarator, Journal of Plasma Fusion Research SERIES 1 422–425, 1998. [AVI 13] AVIC Laser (AVIC Heavy Machinery subsidiary), ‘16th China International High-tech Expo’, Beijing, 21-26 May 2013, web site www.france-metallurgie.com. Also, web site, www.3ders.org/articles/20130529-china-shows-off-world-largest-3d-printed-titanium-fighter- component.html, 2014. [Har 03] G.J. Hartwell, S.F. Knowlton, J. Armstrong, Construction Progress of the Compact Toroidal Hybrid, Web site, http://www.3ders.org/articles/20130529-china-shows-off-world-largest- 3d-printed-titanium-fighter-component.html, 2014. [Naj 05] Farrokh Najmabadi and the ARIES Team, ‘Recent Progress in ARIES Compact Stellarator Study’, Presentation in 15th International Toki Conference 6-9 December 2005, Toki, Japan, 2005. [PPP 07] PPPL Digests, ‘Advanced Technology Essential in NCSX Component Fabrication’, issue February 2007. [Que 16] V. Queral, E. Rincón, V. Mirones, L. Rios, S. Cabrera, Dimensional accuracy of additively manufactured structures formodular coil windings of stellarators, In press, DOI: https://doi.org/10.1016/j.fusengdes.2016.12.014. [Ris 03] K. Risse et al., Fabrication of the superconducting coils for Wendelstein 7-X, Fusion Engineering and Design 66-68 (2003) 965-969. [Web 15] www.peri.es/proyectos.cfm/fuseaction/diashow/reference_ID/459/ referencecategory_ID/25/currentimage/2.cfm, fotograph n. 2, 2015. [Web 17] Manufacturing A Large Composite Rocket Fuel Tank, https://www.youtube.com/watch?v=pi5rxhHBx9o, 2017 References

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Present. SOFE '17 China: Talk in SOFE Symp 2017 Prospects for stellarators based on additive manuf

Present. SOFE '17 China: Talk in SOFE Symp 2017 Prospects for stellarators based on additive manuf

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