MetalicaRap
Release status: Experimental
| Description | Electron beam melting 3D metal printer (EBM)with Scanning electron microscope vision (SEM) & EBM/Vaporizing Z axis correction in a vacuum.(early development phase).
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Contents
MetalicaRap Working Notes
Criteria ; Design a Metal 3D Printer , that produces dimensionally finished parts +- 20 µ m over 20mm, metallurgy equivalent to wrought iron milled metal parts, largely self reproducing, electrical supply limited to single phase ( ie not 3 Phase,), minimum consumables beyond metal powder ( avoiding need for e.g.argon gas ... etc,),cost for parts less than a small car, build-rate can be slow i.e. .2KG per hour, no bigger than a wardrobe.
Due to lack of control in metal powder deposition in conventional ebeam 3D printing (e.g arcam 3d) a tolerance of 300µ in the Z axis is a typical with 10µ powder,( Lower power sizes are prone to magnetic forces and typically unwieldy, though powder demagnetization and non ferrous construction is a possibility ), using 4 pickup Scanning Electron Microscope (SEM) combined with image processing, the pseudo stereo SEM picture data can be converted to true 3D dimensional data (4-source BSE photometric stereo 3D-imaging), Enabling sub µ metal height measurement. Z axis dimensional mistakes in any particular layer can be found and corrected by removal of high points through Electron beam machining / ebeam vaporization of the metal. This brings the XYZ axis to 20µ error over 20mm (IT grade 7 See1.). Future stage in development might include Ion beam etching gun to take dimensions to sub µ level(1µ over 20mmIT grade 0). external links 1.http://www.engineersedge.com/international_tol.htm
Advantages
For most parts builds dimensionally finished parts
Good metallurgy on all common metals
Self measurement of part tolerances
automatic self correction.
Disadvantages
Vacuum chamber needs on going maintenance.
Quantity of metal used in vacuum chamber construction,
Difficultly in managing metal powders, indicated by the need to have layer error correction.
Chamber 1.5 meter cubed rather than desktop size
Main elements
Beyond power supplies, computing power and sensors, MetalicaRap has 5 elements; electron gun, high Vacuum chamber, roughing pump, oil diffusion pump or turbo pump and metal powder dispenser/build platform.
Design Discussion
3KW 100 KV hot cathode gun
High vacuum chamber (initially welded)
Stainless steel High vacuum 10-5 Tor / (mm mercury) NiCr Alloy (10-16) Hexagonalx40 halfhexagonalx16 endpiecesx16 384 bolts copper wire, future ; airlock so print while repump, main door Viton O ring (Euro ).
Vane pump ( initially purchased)
Oil diffusion pump or turbo pump
using existing EBS build design or Turbo pump initially purchased.
metal powder dispenser / build platform
options include ; screw/ trough design; Wiper deposit ; Metal Vapor protection Gun protection disc SEM pickup,& wiper protection
Power Supply Power Supply with Arc sense arc quench arc count.
Back ground Information on Electron beam processes; Scanning electron microscope SEM background(1)(2) , EBM 3D printing(3),
electron beam welding / vaporization EBM(4)
External links
1. http://www.matter.org.uk/tem/sitemap.htm , 2.http://www.uga.edu/caur/semindex.htm
3. http://www.arcam.com/technology/ebm-process.aspx
4. http://www.twi.co.uk/content/spasaug2006.html
self replication
Self-replication of a vacuum chamber runs into the "how to make a match box inside a match box problem". Some say the "lots of small rigid parts joined together" approach -- illustrated on the right -- has "too many joins" for a vacuum chamber. Would a relatively soft material in the gaps between parts -- like the Pb lead between parts of a stained-glass window -- compress enough to make it air-tight? Is there a better approach?
Research Corner Welcoming you
If these knowledge areas are new to you, remember to use your networking skills to talk to others that friend or uncle may be just that expert!
Design Questions
A. Range of achievable spot sizes at target of a Pierce Electron gun running between 100W to 6KW 150KV ? ( given cathode is 1.6m from target max deflection 7 degrees )
B. Possible pit falls of running an SEM at 100W in four-source photometric stereo Ruderford back scatter mode ? ( typical SEM power is 0.1W )
C. Target metal surface temperature measurement would be a big advantage, Do you know of a electron bombardment based remote temperature measurement approach?.
Design question feed back / discussion page here. Add your ideas!
Current status
Based in Copenhagen Denmark Electron gun test repstrap vacuum chamber including pumps and gauges under electrical maintenance.
We are particularly looking out for some Metallurgists, High Voltage Designers and more electron gun designers/support (Electron beam welding/accelerator) .
Current tech team; 5 software developers, 1 Ultra high vacuum metal deposition specialist, 2 High voltage system designer, a theoretical physicist and a electron gun designer.
It would be great for another team to be set up in another part of the world to inspire each other!
Do get in touch!
Related Projects
Specialist Parts Chamber CF flange Electrical connectors, 1x 140KV 2KW , 2x140kV low current, 8x 30A 200V? coils , 8x SEM pickups low current low voltage,
2 windows
3x 12mm Motor shaft Vaccum chamber motion feed through. 10-4 Tor
Future developments
A solar cell production plant design that MetalicaRap will be able to print, that will then utilize MetalicaRap's vacuum chamber to produce Solar cells at under 5cents a Watt peak. An international team has shown interest already!!
Focused ion beam / Ion beam etching gun to take dimensions to sub µ level(1µ over 20mmIT0).
Ion Pump to remove waste vaporized metal.
Files and Parts
Sub Assemblies and Related
EBS=Electron beam sinterer/melting.
sequence - electron gun parts repstrapped EBS. Assembled tested in repstrap vacuum chamber. Metal powder deposition mechanism parts repstraped EBS . Gun depoosition assembled tested. MetalicarapVacuumChamber parts Electron beam sintered by our system. MetalicarapVacuumchamber assembled tested. 5 Elements assembled and tested.
Downloads
Photos and Drawings
More Examples
Practical manufacturing walk through Electricity is 2kwh per hour .5Euro/hr
Part A Stainless size 300x300x200mm 15Kg 10µ Stainless powder (40Euro/kg) melt print 100µ Z layer thickness
1 minute per Z 100µ each layer heated melting-point – 20 0C then printed by beam
3.4 minute per Every 10th layer Z axis correction ; SEM ( part assumed to occupy 1/9 of whole print area; 1/9* 300*300=10 000mm2 measurement at every 10µ, SEM picture 500x500 pixel so 5mmx5mm, So for 10,000mm2 need 400 SEM pictures 10,000/25= 400 4x pictures from 4 picups gives effect of different angles? for 3D picture reconstruction so real distances, 400 5mmx5mm pictures, 250ms a picture ( Risk of underestimate factor x100 ) 1.4min
Remove metal by Vaporization 1ms per 70µ diameter spot area 4000x10-6 mm2 ( 850µs duration & 150µs beam movement) 1/10 of part high(Risk of underestimate factor x2) ( 1/10*10 000mm2/ 4000x10-6 mm2= 1x105 spots 1x105 spots*1ms= 100Sec 2min Time so far 200* Z correction layers 3.4 Min each + 1800 printed layer 1min each = 2480 min ( 1.7 days)
To add a 40mmx4mm = 160mm2 bearing surface by removing up to 40µ to achieve 0.1µ specification Ion beam abrasion 20min per 1mm2 160*20min =3200min
Time total so far 200* Z correction layers 3.4 Min each 1800Min + 1800 printed layer 1min each 1800 = 2480 Min + ion beam bearing surface 3200= 5680( 4 days)
Cost 665 Euro materials 600Euro Electricity 65
Part B Aluminium size 300x300x20mm 1.5Kg
Aluminium 15Euro 10µ powder
Time 20* Z correction layers 3.4 Min each + 180 printed layer 1min each = 248 Min 4 hours No ion beam surfacing Cost 25 Euro materials 22 Euro Electricity 3 Euro
Powder
Stainless steal powder
powder injection moulding
Aluminum powder 15 Euro/Kg 10µ metal injection moulding stainless steel powder, carbon chromium 40Euro a kg. 74µ 200mesh Aluminum powder 15 Euro/Kg 10µ
Useful links
Discussion of Advantages and Disadvantages of different Tool head processes.
