MetalicaRap

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MetalicaRap

Release status: Experimental

Assemble MetalicaRap vers. 2.0.jpg
Description
An Electron Beam 3D Metal and Home Solar cell Printer, including microscope vision system (SEM) & Z axis metal correction in a vacuum.(Design stage).
License
Author
Contributors
Based-on
Categories
EBM,categories =Powder
CAD Models
External Link
please contact us via mail forum below


MetalicaRap is an open 3D metal & home solar cell printer that is currently in the design stage.

The goal is to have affordable home-manufacturing of solar cells, key electrical parts and milled-quality metal parts.


MetalicaRap, An Open 3D Metal & Home Solar Cell Printer

Design criteria

The printer should have the following characteristics:

  • A build volume of about 30cm x 30cm x30cm
  • Produces finished parts +/- 20 µm over 20mm
  • Finished parts should be the metallurgical equivalent to wrought iron milled metal parts (full strength, >98% density)
  • The printer is largely self reproducing (i.e. it can print many of its own parts)
  • Single Phase electrical supply
  • Minimum consumables beyond metal powder (avoiding need for e.g. argon gas would be an advantage for later designs)
  • Cost for parts which it cannot itself print plus the raw material for printable parts is less than the cost of a used car (self replication plus self build kit may reduce the price by approximately 100 times i.e. from the existing price of a metal 3D printer or solar cell plant; 1,000,000 euro price tag, to 10,000 euro self print/kit price. historically the plastic printer went from 30,000 euro commercial price to 500 euro in 2009 via this approach)
  • The build-rate can be slow i.e. 0.2 kg per hour.
  • Max height should be 2.4m so it can fit in a home. ( first / simpler to construct prototype will be taller than this until we know how much we can bend beam while maintaining spot size, the bigger the bend the shorter it will become)
  • Shape and size of vacuum chamber and electron gun power rating should be suitable for Solar Cell Printing.

Initial decision making

An electron beam based printer was chosen due to the ability to print itsself, the power efficiency of an electron gun vs. a powerful laser at fusing metal, and the fact that an electron gun and vacuum chamber are the primary requirements for thin film solar cell printers. It was recognized that the printer did not require a new technological invention, but does require the existing solutions to become publicly accessable through grassroots research and re-engineering, freeing them from current industrial secrecy practices.

Solar Cell Production

One of the goals is a solar cell production plant design that MetalicaRap will be able to print, that will utilize MetalicaRap's vacuum chamber and beam for the solar cell manufacturing processes. For a typical family home electrical system we may bring the solar cell cost down from 10,000 euro to 400 euro by self printing. (solar cell installation, inverter, and other costs would obviously be on top of this price).

It should be possible to use a process that creates thin film solar cells at a vacuum of 10-4 Torr by directly co-evaporating copper, gallium, indium and selenium onto a heated substrate[2]. Other precursor choices should also be possible[3]. The CIGS manufacturing process will consist of electron beam physical vapor deposition[4] (EBPVD summary by material [5]) and DC sputtering in the vacuum chamber(DC sputter animation [6]).

Essential Reading

Existing Commercial Electron Beam 3D printer 2min video introduction click link in square brackets here [7], People locally developing solutions for local problems (while being connected globally[8]) and for those who have everything developing technology for a market of one! personal fabrication as a way to take control and as an aid for identity [9], Factory at home, See [10],A commercially Printed Rocket Engine Takes Flight in USA! See here at 2:40[11] (a stainless steel 3d Print)

Newsletter

We are now 18 months into the development of a printer capable of printing in all common metals, which can largely print itself.

Why an Open Design?

Currently few commercial companies give away the ability to manufacture their own product to the customer(googles "free search" business model comes closest and also Mendel see below). MetalicaRap does through self printing, which is why this project needs volunteers initially giving their time, effort and charitable contributions via crowd funding. This price reduction method and empowerment model has been shown to work with a plastic printer in 2009 bringing the price down by a factor of 60 (30,000 euro to 500 euro kit price Mendel http://reprap.org/ http://en.wikipedia.org/wiki/Adrian_Bowyer award wining inventor).

What are the benefits?

A home solar cell printer will enable a whole set of new possibilities via nearfree electricity including: water supply from air condensing, home tropical greenhouse[12], along with the well known environmental benefits of solar power.

Later MetalicaRap may reduce metal costs by replacing foundary processes by processing its own billet metal in to metal powder through electron beam melting on to a spinning disk within MetalicaRap, an established method. In the special case of Titanium we may bring the powder price down to 6 euro per kilogram (2012) as titanium's last refining step is Electron beam melting "Titanium Sponge" the identical process to MetalicaRap's. Titanium's properties include; Highest strength weight ratio of any pure metal, Corrosion resistance similar to platinum, surface hardness after treatment in MetalicaRap to nearly as hard as diamonds (TiN gives Mohs 9 out of 10) so would enable new technology jumps.

Why should i help?

There is no technological block to the success of this project, but it requires the engineering solutions to happen within an open hardware cultural context to succeed, a group of technical specialists volunteering there time and effort, along with crowd funding. We have had involvement 6 part time specialists based in Copenhagen, Geneva (x-Cern), California (x-stanford), and Toronto volunteering part time in areas including electron gun design, currently we have 2 specialists consulting for us. The more people involved on a non-specialist task level will bring the project forward quicker.

Critically MetalicaRap may offer the ability to largely print the most expensive parts so may enable the price of the solar cell printer to fall by a factor of 100, so to be within the home budgets grasp. (printing the electron gun is equivalent to printing a 600W fiber laser in a Selective Laser Sintering machine, this guns function is to melt metal on a build platform to producing metal thin film solar cells and metal parts)

For now the self replication will not include the vacuum chamber as it will be largely welded and glued from stainless steel 304 14inch pipe. The power supply is under construction from bought in parts. One pump will initially be purchased, and as the design progresses further parts will be self printed.

If you would like to help and knowing that MetalicaRap's design development details do not fit in one persons head, please specialize and take ownership of a specific task from below or contact us via the mail forum.

Towards this aim of reaching further volunteers we would really appreciate the inclusion of the below within your member contact newsletter in a form that suits your organization.

Kind Regards MetalicaRap team

Request for specialists and non specalists

We are looking for further technical people who are committed to empowering themselves and their environment through self motivated practical tasks in the following areas: Stainless steel metal prototype machining, High voltage power supply prototyping (100kV 1KW),   Vacuum instrumentation, mechanical drafting / design, and back end software (specifically in unified accelerator library; a gcode to electron beam deflection coil data application). We are now also looking for more people to chase non specialist tasks as well.

Crowd Funding Support of MetalicaRap

We are currently raising money to make a RepStrap version of MetalicaRap.

We need an estimated 50K euro, and have so far raised over 5000 euro. Donations over 100 euro recieve a MetalicaRap Printing Certificate. We are aiming for a final kit parts price of 11K to 15K euro.

You can donate money:

There are many other ways you can help further the development of MetalicaRap. Please read this page to get an idea of current development status. We can be contacted on the RepRap IRC channel, [email protected], or best at RepRap MetalicaRap forum.

Practical Tasks

Specific's

  • Put this type of vacuum flange [13](dead link) in to freecad[14] and upload the 3D result to the files and parts section on the site, owned by username ;...........likely finish date :.........emotional status..........
  • What motor power for build platform vertical motion see scale diagram below ? owned by username ;...........likely finish date :.........emotional status..........
  • Which diameter for extension rod inside moterdriven sleeve. I.D. & O.D. sleeve diameters, I.D. & O.D for extention shaft? owned by username ;...........likely finish date :.........emotional status..........
  • What motor size & minimum shaft O.D. for hopper X movement/powder deposition ? owned by username ;...........likely finish date :.........emotional status..........

Broader research (this is the difficult stuff) you need plenty of free time to do these

  • We need more hours of CAD input, we could do it much quicker with VacuCAD as all the standard parts are already defined owned by username ;...........likely finish date :.........emotional status..........




Your suggested task here (especially pleased if you are going to do it)

  • ....................................................................................................................................................................................owned by username ;...........likely finish date :.........emotional status..........


None of the processes in themselves are new, they have all been done in other contexts. What is new is that it may offer finished parts requiring no further machining, verification of parts tolerance and bring error correction to metal powder 3D printing for the first time, thus enabling full-strength finished dimensional parts production.

(add your username, your likely Task completion date , and emotional status comment ;(possibles include " its fun" " its challenging" "wow" "----" "I feel like Robinson Crusoe" " I am so alve" "I am going to be wealthy" .... )

Current taken Jobs

  • Calculate the required thickness of the vacuum chamber , in stainless 304 and Aluminum , Further material savings ? File:Assembly1 MetalicaRap V2.04.stl Pre detailing chamber to scale ( upload a file with your calcultions with this file name "MetalicaRap contributor additions to calculator spread sheet Rapatan checks adds002.ods" .owned by username: egoZentric likely finish date : 18/10-2011 emotional status: zenfin-ish.
    • File:Cylindrical_Vacuum_Chamber_deflection.ods [15] Results are unverified as of 20:20, 26 October 2011 (UTC) - 2nd opinion required !
    • /eZ


  • Recalculate powersupply for fullwave cockcroft walton ladder and find suitable isolating transformers 3V 50-60 Hz 10 A 100 Kv insolation, suitable to work with a 100 Kv feedthrough see here [16]owned by username: cclor likely finish date : 28/09-11 emotional status: quick-ish.


Contact: click here [17] Rapatan

File:Gun Coil Pump Cost calculator MetalicaRapReadOnly.ods This is MetalicaRap's master spreadsheet click on to download.

Please add your additional calculations for the above spread sheet by uploading either of the following two files with your fresh calculations in, we will then check and make the addition to the master spreadsheet. (please add to them when they are in the red font state only, to upload select upload from left hand menu, you know you have succeeded when one of the below goes blue)

File:MetalicaRap contributor additions to calculator spread sheet Rapatan checks adds002.ods

File:MetalicaRap contributor additions to calculator spread sheet Rapatan checks adds003.ods

General Design

Philosophy

"Since Jones and Swainson many other techniques for rapid prototyping have been developed. Three of the most significant are selective laser sintering (SLS), filament deposition modeling (FDM), and the MIT powder/ink-jet-glue process.A rapid prototyping machine that can make most of its own component parts will clearly be easier to design if one avoids things like high-powered lasers; having the machine make a laser from scratch would be difficult. More subtly, ink-jet print heads (though cheap) are intrinsically hard to make as they involve micro-fabrication, and so a machine based on them would be unlikely (in the medium term) to be able to liberate itself from that one bought-in part. " [18] Adrian Bowyer

Even though SLS was one of the 3 major contenders for the reprap machine, it was rejected due to the difficulty of self manufacturing the laser. Using an electron beam may offer easier self manufacture, due to it largely consisting of 3 simple elements; a cathode metal ring, an anode metal tube and a hot wire.

Another key issue is producing verified, dimensionally finished parts. Commercial metal powder printers, both laser and electron based, can not measure the individual parts they produce during production, unlike conventional machining methods. MetalicaRap could due to the inclusion of a layer by layer measuring system (stereo, 3d scanning electron microscope).

The challenges of Z axis control is expected to be greatly helped by the vision system and z axis correction method EBM/vaporization (Vision systems are currently in development stage on state of the art commercial machines.)

Its important to point out that this is a complex and in the 1000's of euro price range project. Your largely self producing printer is possible in the commercial setting with either laser or electron beam printing parts (as the commercial machines indicate), but due to the power transfer inefficiency from wall socket to most common metals via lasers being 50 times worse than in electron beams, available home lasers would print too slowly (an exception to this is laser to steel:80%)( typically a CO2 laser in copper 1.6% energy transfer efficiency, So a 400W energy to metal therefore requires a 25000 W laser, current home build lasers are considered large at 30W), therefore lasers would limit achievable part size to 10's of cm3( e.g. 3cm x3cmx3cm) with a 2 day print duration, which makes it impracticably slow for self replicating printers. (For further proof try our Laser 808 Build Speed Calculator get from bottom of this page link here[19] )

So the electron gun is still likely to be quite a bit easier for the same power level, especially as long as complications due to magnetic forces, grounding, X-ray radiation, and calibration do not turn out to be too bad a problem, and I wouldn't expect them to. Also, its likely that subtractive machining is needed. Commercial printers report being able to produce finished parts for jet engines and medical implants etc. without it, but granted maybe there are details the manufacturers don't put on their web sites. ( thanks toGreenAtol for his overview assistance Rapatan.)

Initial technical decisions

Due to lack of control in metal powder deposition & molten metal forming droplet/distortions in conventional ebeam 3D printing (e.g Arcam 3d) a tolerance of 300µ in the Z axis is a typical with 10µ powder, (Finer powders are prone to magnetic forces and typically unwieldy, though powder demagnetization and non ferrous construction is a possibility) this demands an error correction which is based round a Vision system using 4-sector, independent channel axial Back Scatter electron detector (BSE) Scanning Electron Microscope (SEM) combined with image processing. The pseudo stereo SEM picture data can be converted to true 3D dimensional data (asymmetrical 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 of the metal. From discussions with industry experts we may bring the XYZ axis to 20µ error over 20mm (IT grade 7 See IT grade table here [20].

Advantages of current chosen design approach

  • Fully functional parts directly from standard metals
  • For most parts it may offer dimensionally finished metal parts IT grade 7
  • Good metallurgy on all common metals (Melting process rather than sintering process ensures near 100% of solid material)
  • Closed loop system
    • Self measurement of finished part tolerances.
    • May offer automatic self correction (subtractive machining steps during build process and feedback with compensation used in the additive process).

Additional Benefits; Can print thin film CIGS Solar cells in existing 10<math>^-</math><math>^4</math>vacuum chamber with existing electron gun, will be able to self print additional required parts for solar cell printer.Example process[21].

Disadvantages of current chosen design approach

  • Vacuum chamber needs on going maintenance.
  • Given the quantity and quality of metal/materials used in 10-4 torr vacuum chamber construction they may have high cost or be hard to obtain. (Limited outgasing required, more info: [22][23])
  • Difficultly in managing metal powders, indicated by the need to have layer error correction, Problem area's including; powder layer flatness, metal meniscus blob formation, metal powder trapped in work piece (i.e. designed internal closed cavities, designed internal porous or honeycomb structures most likely impossible without additional processing or work on the part after printing).
  • Quality Control may be a hurdle to overcome - on the fly heat treatment process development (to overcome residual stress present in the first few layers) may be desirable but optional. This is a problem in general for additive manufacturing of all sorts at present.
  • Adequate surface finish may require post processing, depending on the purpose of the part (what do commercial EBM machines get?).
  • Non-desktop size wardrobe size, chamber volume approx 1m cubed.

Main elements

MetalicaRap in it's current form has 7 main elements which form the printer hardware proper:

  • Electron gun including deflection assemblies in a 14 inch dia. gun tube 1.6 m long
  • A metal powder dispenser trough hopper, with a cartesian 8cm diameter topological pick up ring. ( in a box created from a single 8 cm thick sheet of aluminum self shaped to box by MetalicaRap subtractive Electron beam cutting)
  • Build platform in a 14 inch dia. build platform tube 1.20 m? long (this first version will be taller)
  • SEM for vision system/feedback regarding the shape of the part and what's going on in the chamber, using the 12kg trough hopper pick up ring.
  • 2 vacuum pump: one roughing pump ( diaphragm pump no oil ) and one Self printed distributed Ion pump with some tantalum, slotted cathode cells for argon gas collection[24] or oil diffusion pump or turbo pump. (prototype uses turbo pump)
  • Power supply with high volage elements vacuum encased - known to be doable, knowledge of how to do it widespread.
  • Optional beam windows; High tech stationary window or Low tech scanning Aluminum foil slot shaped beam window.
A low power gun build example
Low power gun in operation.. See [1]
Electron Gun Elements
Coil wiring diagram

Electron Gun

Static Electron Gun B 5KW max (80KV to 150KV 33mA) 1 m above build platform. Providing additive printing through melting at high beam deflection speeds, enabling high build rates, prototype will be approx 1KW 100kv 10mA beam current

For the prototype we suggest one gun in a chamber that can be used to test either guns design( Melting gun and vision gun). Once we see the outcome of the test we can decide to try two separate guns again if necessary. The one gun will be stationary situated 1m above the build platform. A sensor pick up ring will be attached to a 12Kg gravity fed powder hopper just above the build surface with 2 powder wiper blades attached, using sliding slotted plates to release the powder (design similar to household air vents, but ours will have sharpened vent edges). A second powder hopper will gravity feed the 12 kg hopper. It will be situated in the side of the 14 inch OD diameter gun tube and will obscure a little part of the build chamber from the beam(a necessary compromise). This one gun will be used for both melting and vision systems. a back-scatter detector ring will be attached to the powder hopper, close to the workpiece mounted on the Cartesian XY system (the hoppers motion itself provided by the X motion of the hopper, Y motion by means of further 2 linear bearings on front of hopper and drive shaft (No automated Z movement of the ring is included in the design ), (Technical background: See 5.2 [25]see lecture 4.02/11/04[26],[27]

Providing build platform metal powder heating and melting, spot size 100µ (may be inaccurate) pointing accuracy 10µ (may be inaccurate). The gun probably will require the inclusion of a liquid cooling anode system via its support. You take heat out of assemblies like this by incorporating water cooling. If you use high purity water (80 meg-ohm) it is reasonably non-conducting electrically, though initially tests will be air cooled vanes on high voltage feed through copper bar.

Vision gun method of providing Sub µm Topological mode SEM vision system (See [28])

Additionally providing Micro vaporization (See gun layout Page 3 [29] down to 10µ to 40µ spot size), Initially this would be used to flatten every tenth layer of the build through high points / blobs removal. Future software development could provide live modeling of build, so through the adjustment of beam melting path in following layers errors/ blobs could be taken account of as they arise, thereby limiting the need for blob removal to critical surfaces.

Vacuum Chamber and 2 pumps

Link to details of High vacuum chamber (initially welded then glued)

  • first pump is a roughing pump (initially purchased Vane pump e.g. Varian DS102 1.5x10<math>10^-</math><math>^3</math>Torr ) or better an oil free diaphragm pump.
  • Second pump is a self printed High vacuum Titanium sputter-Ion pump (with some tantalum, slotted cathode cells for argon gas collection [30]) or bought in turbo drag pump or self printed oil diffusion pump (messy) (Use electron guns coils to provide magnetic field to splutter ion pump which pumps down chamber down [31] 50L/s max 1.5x10<math>10^-</math><math>^1</math><math>^1</math>Torr) Prior to self print bought in cost can be saved via diffusion pump route as they are by far the lowest cost to get to the vacuum levels needed compared to a turbo pump doubles the costs (4K euro extra) e.g. pfieffer or Turbovac 50L/s 1.5x10<math>10^-</math><math>^9</math>Torr).
  • Constructed from Stainless steel 304 14 inch pipe (NPS 14 min. SCH 10 ) with one 100mm thick Aluminum plate with interior "carved out" for hopper box sides and top, a further 304 plate for bottom of hopper box with o-ring seal, 304L Top and bottom pipe end caps if not domed min. 18mm thickness typical 25mm thick with copper CF flange and hinged window access.
  • High vacuum <math>10^-</math><math>^4</math> Torr to <math>10^-</math><math>^5</math>
  • Electrical feed-troughs ; For tungsten filament AC 10A 3V 50/60Hz heater power supply electrical feed-through includes a oil immersed 100KV isolating transformer using a Pyrex and quartz tubing within CF pipe coupler with orings with oil imersion on outside [32] .By placing last stage of main 100KV power supply the cockcroftwalton ladder in its own vacuum chamber keeps all high voltage ( 100KV) within vacuum(except filament isolating transformer) which allows 15 KV sparkplug type electrical feedthroughs to be used [33] these are welded sparkplugs on CF flanges with out radio noise suppression carbon resistor . A further welded sparkplug type electrical feedthrough will be used for interconnection of 100KV from power supply sub vacuum chamber to main gun chamber.
  • Mechanical feed-troughs ; 45Nm torque oring or more leak resistant magnetic feed-throughs
  • Viewing window/ Door 8inch borrsilicate glass, 3/8 thick, standard 10 inch CF plate and Oring.
  • Pirani vacuum guage ( avoid cathode guages as ionisation from gun my interfrere with them)

Our high vacuum pump will be a sputter ion pump as has a cost reduction and ease of use advantage for us especially with the window option . As the high vacuum turbo pump cost has been a block to costs coming down, but after redesign an Ion pump seems a good solution, approximately 300 tubes (anodes at 8KV) 15mm diameter 26mm long made of stainless, with 8mm diameter titanium plates ( cathodes at 0V) fitting in either end of anode tubes , leaving a 3.5mm gap for the gas to enter, these are situated around the outside of the lens coils providing magnetic fields in their own stanless steel cans and a 8KV supply hooked up, we have create a electron gun and ion pump combination pump. The number of tubes control the pumping rate it lasts 400 hrs at 10-4 torr but 40000 hrs at 10-6 torr . slotted cathode cells for argon gas collection [34] Nitrogen getting on repeated door opening will be overcome through 400µ micron silicon sheet with 50µ micro dead end holes creating ebeam window(inter maintenance interval much higher if us a window option, see below ).

Alternative roughing pump is use an oil diffusion pump but this may be of limited use as it puts some silicon oil vapor in to the chamber which will be cracked if in contact with tungsten filament (at 2600 C) producing oil by products that reduce the vacuum and affect the quality of final produced metal parts, there is an existing home build design, see here: [35],[36] (use google translate) though some people have had success with using the chilling unit from an air conditioner in-between pump and chamber [37]. Other electrical feedthrough options includes 100KV sparkplugs with out radio noise suppression carbon resistor [38] with oil immersion on outside.

But many commercial machines use the diffusion pumps and cope with the oil issues;The cooled condensation baffles in between the pump and the chamber is adequate to prevent any significant amount of oil getting in the chamber at these pressures.

The best way to do wire coils is to seal them into a stainless steel can, and allow a cooling medium like air to ventilate the can. You cannot hope to dissipate much heat from a coil in vacuum, and you don't want the coil to outgas into your vacuum anyway


Metal powder dispenser

This will be a gravity fed split powder hopper.A small hopper will move in the x direction, intermittently refilled by main hopper situated in side of electron gun tube.The small hopper will have a 12Kg powder capacity, this gravity fed powder hopper just above the build surface has two 1cm square section powder wiper blades attached wither side, leveling the roughly dispensed powder. The powder is released using two sliding slotted plates, ( design similar to household air vents but ours will have sharpened vent edges). At the end of the hopper travel a small waste powder slot will remove old dispensed powder before the next dispensing sweep takes place. A second main powder hopper will gravity feed the 12 kg hopper, it will be situated up in the side of the 14 inch OD diameter gun tube and will obscure a little part of the build chamber from the beam (a necessary compromise). The vision system feedback can accommodate some roughness in the powder deposition during beam melting phase and subtractive removal phase.This design may lead to clumping with some powders at higher vacuums. The window option overcomes this but introduces other complexities in vision system and beam distortion (see below).

Other dispensing/ considerations include:

  • Metal Vapor will be released in to the chamber during the melting of the the powder, a later consideration is protection of the gun, initially the guns distance from the build platform should be adequate, but the possible inclusion of a spinning slotted disc in front of the gun as further protection may need to be considered,
  • SEM pickup PIN diodes protection cover will be used when printing,
  • Variable layer thickness might (?) be desirable to provide fine control of the vertical resolution using thin layers where desired, while still allowing relatively high build speeds that come with thick layers for other areas.
    • The Arcam EMB uses a "textured roller". Presumably a roller is textured with a pattern of holes which is loaded with powder, then the powder falls out of the holes, and a little random redistribution occurs on the way down to the workpiece surface for a reasonably uniform powder layer of repeatable thickness this design will likely operate at ultra high vacuum.
    • Leveling the surface of the powder bed or enabling better flow through hopper at ultra high vacuums may be possible using ultrasonic lubrication to briefly fluidize the powder bed. It might cause unacceptable settling though.
    • The density of the powder is lower than the density of the solid metal. So if the powder is only deposited using say the textured roller the upper level of the powder bed will get higher than the surface of the part being printed. How is this dealt with in the Arcam printers? More research needed

Build platform

A 30cm vertical travel stepper motor driven circular platform within a 14 inch 304 tube. Within the build platform is a built in ceramic insulation layer. To keep the metal powder from falling off the platform two felt o- rings make a seal between the moving platform and the stationary tube.


Transformers and ladder 3 phases

Power supply

Power supply with Arc sense, arc quench and arc count with output via 100KV triode valve for beam current control .


LCC Series parallel resonant converter full bridge version 62.5KV 0 to 5KW running at 181.5KHz resonant up to 500Khz at idle, with a 325V to 62.5KV transformer with voltage doubler on output, the transformer is designed for a specific value of inductance and capacitance to operate at the desired resonant frequency, its magnetic flux pole with multiple ac to dc converter stages with planar coils. Each of the 208 transformer secondary converter stages is a pcb with 4 turn coil track outputting 300V d.c. via cheap rectifiers and smoothing capacitors. Along the stack of pcb's the voltage increases gradually keeping under the paschen air arc limit. This means that the power supply secondary converter stages can be tested as 208 seperate 300V Power supplies, before all the secondary converter stages are connected in series creating the 62.5 KV output,. Transformer magnetic flux pole/planar core has wire (87A) 8 turn primary on a transformer bobbin above it a single flanged (10cm flange on HV end) high voltage bobbin 4mm of UHMWPE insulation (calc?).This output is then current modulated by a tetrode ( triode limits bandwidth [39], this tetrode is a safety feature but you could modulate at main gun cathode instead with poor short circuit protection and poor repeatability due to main filament replacemnet) tetrode output goes on to gun cathode. This is a cheaper option and avoids high energy storage issues and reduces the amount of specialized high voltage equipment of the ladder version below.


Voltage multiplier ladder version Cartesian 1kW gun power supply circuit construction will be based around 2 MOT serialized 100KV(1Kw) that gets feeded from a freqency controlled 3 phase switchmode powersupply range 100 Hz to 1 KHz and 8 stage Cockcroft walton ladder for the positive 15 Kv x8= 120KV un regulated, To avoid the need for both; expensive air tight 100KV connecters, and power supply oil immersion , the Cockcroft walton ladder will be situated within the vacuum tank (dead tank with the enclosure at earth potential) in a sub chamber sealed from the main chamber having its own small 8KV ion pump with some tantalum, slotted cathode cells for argon gas collection [40]. The intermediate wall between vacuum tank containing Cockroft walton ladder and main chamber containing gun will be constructed from copper with internal water cooling channels connected to exterior water supply to avoid Diode and resistor overheating problems. With the use of a one way valve between chambers the circuitry remains well insulated unaffected by vacuum loss in the main chamber. .( Cross linking machines already use this vacuum encased powersupply approach).

Cockcroft Walton ladder Calculator Help & Tool for any one who want's a fast overview [41]


Power supply functional diagram now full wave Cockcroft- Walton ladder

Optional beam windows

A window between gun and build platform enables the ion pump inter maintenance duration to go from 400 hrs to 400,000 hrs, it enables the use of high brightness small spot size LaBa6 filaments that last 10,000 hrs as opposed to 70 hrs for tungsten. Allows the use of barrier argon gas at atmospheric pressure surrounding build platform and associated mechanics so no pump down time after accessing build chamber and great savings on mechanical feed through seals. Will also offer large part manufacturing in inexpensive argon "tents" as only the gun requires a vacuum chamber. Disadvantages include; some ballooning of beam as it passes through approx 5mm's of argon atmosphere between build platform and window, lowing resolution of SEM vision system ( x-ray sensing option may help or build platform chamber pump down for vision system and argn for printing), high tech stationary window will involve high tech manufacturing , Low tech Aluminum slot window will reduce print speed and increased mechanical complexity as build platform to gun physical scanning motion will be required.

Low tech option; Scanning Aluminum Slot beam window (14cm length x 100µ width )

A narrow slot window which is physically moved across the build area.Window will be cooled through thermal conduction to water channels surrounding window. Requires minimum 100KV beam to penetrate 20µ thick AL window, so keeping beam losses below 21%. Beam loss is inversely proportional to acceleration voltage.

High tech option; stationary window

A stationary high tech window that will be cooled through convection and radiation alone. "transparency" of window enables the possibility of a less penetrating beam of 60KV.

Beam divergence at different atmospheric pressures beyond window, left at atmospheric pressure, middle at third of atmospheric pressure , right at a hundredth of atmospheric pressure


Costs and technical calculations spreadsheet

Gun Calculator, download MetalicaRapReadOnly.ods left side
Lens Coil Calculator , download MetalicaRapReadOnly.ods above left side
Large part costs, download MetalicaRapReadOnly.ods above left side


File:Gun Coil Pump Cost calculator MetalicaRapReadOnly.ods this is metalicarap's master spread sheet click on to download.

please add your additional calculations for the above spread sheet by uploading either of the following two files with your fresh calculations in, we will then check and make the addition to the master spreadsheet. (please add to them when they are in the red font state only, to upload select upload from left hand menu, you know you have succeeded when one of the below goes blue)

File:MetalicaRap contributor additions to calculator spread sheet Rapatan checks adds002.ods

File:MetalicaRap contributor additions to calculator spread sheet Rapatan checks adds003.ods

Remember: What is contributed is more important than the expertise or qualifications of the contributor.

Software

Include the following models for tracking the process;

  • Electron gun beam focus model:To highlight resolution operational compromises between; the higher the gun cathode voltage the tighter gun focus, so the smaller the beam spot size on the metal powder giving rise to a higher XY minimum feature size (lens adjustment can alleviate. See lens simulation [42]), yet also the higher cathode voltage the faster the electrons go, so the deeper the electron energy deposition/giving rise to deeper vaporization holes, giving less vertical Z resolution, (used during Z axis error correction mode). Also surface tension is correlated with temperature, and works in opposition to wetting effect flattening the surface of the melt pool (if the melt pool diameter is small compared to the thickness of the metal layer it may appear as a molten blob of metal). This model will receive an energy profile of the beam by pulling two wire prongs through the beam in the X and Y direction, The wire prongs attached to the end of the sensor ring will be pulled through the beam by the XY motor drives, thereby sensing the energy cross section through the electron beam, which will be radioed back to Unified accelerator Library control system, enabling automatic adjustment of beam focus, beam strength and beam spot size. This will also be used to compensate for ripple in the power supply and operational loss of beam alignment from for example filament variation and magnetic interference. All except the last of these effects should be predictable so most calculations for build can be done by the model prior to build in offline mode.
  • Thermal Real Time Model; this allows us to keep track of the thermal changes across the build chamber or cooling path as the electron gun pulses strike the build volume powder. Considering the following 4 situations conduction rates:1. Metal powder & solid metal volumes experiencing direct electron energy deposition (i.e. heat around electron penetrated regions, the depth of these volumes increases with Cathode Gun Voltage KV & vary with metal type) see electron penetration model [43], 2. solid metal thermal conduction volumes (the completed elements of final metal part under construction), 3. metal powder conduction volumes (the surrounding powder), 4. chamber/boundary thermal conditions (vacuum region, build box). See electron strike model for different metals and different cathode Voltages.In general for any unit volume receiving an amount of energy per second to be raised by 1 degree K (the metals specific heat capacity) from a distant energy source, the amount of energy (W or J/s) arriving from that energy source(the electron beam) via a path; The paths energy transit rate (the conduction rate) is dependent on the cross sectional area of path, the length of path and the temperature difference between the ends of the path, ( "thermal conductivity, units in W/deg.K). The volume changes size by the surrounding pressure (atmospheric pressure, indicating the density of the material).So from known initial temperature conditions combining the specific heat capacity, thermal conductivity and density to calculate paths, then summing these paths leads to knowing the temperature of a specific unit piece of metal and its physical state, solid or liquid or vaporized (temperature above or below its melting point or vaporization point at any particular time). The following should be considered; variation of mass with scan speed, bed preheating scans. See for more background technical information. [44] [45].
  • We may need a network structure to combine the different hardware elements.

"Unified accelerator library"

Our electron beam focus model and control software choice

Those looking for entertainment might look at the open source Unified Accelerator Library (UAL) that has a 30yr track record of simulation and control of electron beam movement , a Electron beam focus model and a Control/Simulation approach. But UAL lacks thermal models and metal powder melting modeling so it's main use may be to get the beam spot landing on the powder at the correct position and with the desired diameter defined in the G code from skeinforge. (You can down load UAL here [46], [47] Introduction here, [48]

Manuel for UAL's Design Toolkit called MADX where you can enter a hardware definition i.e. collection of coils along a beam start with two solenoids at 0.1m and -6 m, beam at 0m along latticeset, at 3KW 100 micron diameter (MetalicaRap will likely have 3 XY deflector coils for beam deflection, 2 "Solenoid" for beam lenses) then run simulation of beam with OFFLINE MODEL UAL 1.9 here [49].

The hardware definition of coil positions is called the "lattice". The control ONLINE UAL 1.11 will them apply this simulation to the control of the electron guns in real time. Ignore the following elements we don't have them in MetalicaRap: BeamBean, electric kicker,Kicker, RF cavity, taylor map, wake, wriggler .

This has the advantage of being a closed loop system, which while simulating the beam movement simultaneously records models coils, guns, motors inputs; voltage values, current values etc. Then when you run the real world machine these form the drive instructions to the machine, any sensors picking up deviations are resolved through alarms or the software "reality checking" and thus improving the model. It also is designed as a multi user, multi platform software environment. Some draw backs may be over complexity of the system.

  • An open source network software Fast Network "EPICS" for running UAL on, See here [50] [51] More Info here[52]

"Code Aster"

Our thermal modeling software choice

Quick start instructions on thermal modeling software:

  • Open Source thermal real time model software Code_aster Introduction here[53],
    • Download code-aster software (Windows) here [54],
    • Download extra element GetDP.exe here[55] (put GetDP.exe in c:\ASTER\OUTILS\gmsh\)[56],
    • Download code-aster software (Linux to compile) here[57],
    • Download extra element GetDP.exe here[58] (put GetDP.exe in c:\ASTER\OUTILS\gmsh\) once it is installed and extra element has been copied then as it finishs select option to run code aster.

First select your problem type definition files from the wiki i.e.Thermal program example See here (Use login user: getdp password: getdp) [59]

Second build your mesh of shape you require to be tested, with code_aster sub module Gmsh: you can find it In ASTK prg window under menu item Tools Gmsh \\\ then in Gmsh window select GEO in drop down sub menu //// or import shape via .stl file In ASTK prg window, menu item Tools, Gmsh , then in Gmsh window select; MESH submenu

Third run solver to solve the problem you have defined above by selecting the SOLVER submenu in the GetDP window and hit GetDP button. In GetDP window choose source files for problem; name.PRO file(the problem defined in an example text file from GetDP wiki ) Choose name.MSH ( mesh file defining geometry) Then in GetDP window select options and tick "display client messages" option, then hit Pre then Cal then Pos buttons and then see window called message console window and it will tell you what happened, the output results files name.PRE name.RES name.POS will be in the same directory as the name.PRO file you selected for input.

General info;(Gmsh is a three-dimensional finite element grid generator with a build-in CAD engine and post-processor) See here [60] Can access Gmsh through Graphic user interface or directly through unix or TCPIP socket via code_aster sub module getDP Download GetDP.exe here[61] (put GetDP.exe in c:\ASTER\OUTILS\gmsh\ or specify path to existing location) Overview here [62]See here [63]GetDP documentation here [64], Thermal program example See here (Use login user: getdp password: getdp) [65] Documentation for relevant thermal model calculations See Thermics module R5.02 booklet: / General Architecture D00301a.pdf In DDocsHTML (Down load following two links, unzip to same folder) [66] [67], Complete Guide to code_aster documentation here [68], Software Principles explained here[69] ,Aster documentation source here [70] , home page here [71] wiki[72],

Research Corner Welcomes Your Contribution

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/research questions:

  • A. Find magnetic optics simulation packages and run simulations for a Pierce Electron gun running between 50W to 1KW 100KV  ? ( given cathode is 1.6m from target max deflection 8 degrees ) ( spot size vs Cathode voltage, ideal guns , for max 60 KV and max 100 KV guns) ( N.B. All lens are magnetic not electrostatic because to achieve high enough resolution implies guns at 60KV + , to deflect the beam Electrostatic lens must be similar leading to insulation problems and high distortions.)
  • B. Possible pit falls of running an SEM at 100W in four-source photometric stereo Ruderford back scatter mode ?
  • (Depth of field of measurements layer errors over 200µ height, 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?.
  • D. Quantify relationship between cathode surface tolerances and electron gun performance, (spot size variation , 2nd order effects etc ) Quantify range of gun performance at cathode tolerances of IT 7.
  • E. Which pattern of beam movement a "fixed raster pattern (like a TV scan)" or "point and fire where needed" in a) preheat stage? ( taking temp up to 20 C below melting point) b)melting/sintering part shape? (scanning coil eddy curents overcome with delays?,scanning blanked out areas leads to time wasting?, variable shaped beam more efficient?, Interference from other signals- X ray , secondary electrons , luminescence , beam induced currents?, Clear path for beam? )

Design question feed back / discussion. Add your ideas here!

MetalicaRap Construction; Physics Principles/Disscussion

Background Technical design considerations

Construction Materials

Materials:

  • Vacuum chamber wall stainless 304 ( Prototype ; Vacuum flanges use cross forged 304 stainless)
  • Nickel for some fittings
  • metals for cathode/1stanode-wehnelt/ anode electrodes? '(tungsten /molybdenum/ tungsten,)
  • metal for "soft iron core" surrounding coil windings, unalloyed soft iron for yoke use a soft iron, like AISI 1006; as low carbon as possible. or possible. "Hyperm O", (Cobalt iron alloys for pole pieces if needed e.g. Vanadium Permendur is a superior soft magnet material, but it is VERY difficult to work with and very expensive , and requires fair expertise in heat treating after machining. You should only use it if you need to)

Inter lens X Y deflection coils made from 3 ferite toroid's (N97?), all X deflection coils interconnected, with the first toroid wound in opposite direction from the second and third toroid's and Y deflection coils similarly connected.

  • thermal conducting material for anode support structure that extends through high voltage feed through? copper
  • Thermionic emission regime hot filament design; Tungsten Ribbon 2mm wide 0.254mm thick ( copper infused tungsten has also been mentioned as more stable physically
  • ceramic insulators, you can use either mullite or alumina. Do not use stuff like teflon (is a sponge for water, and outgasses too much) or macor (machinable glass - too delicate). Your shoulder washers in electron gun support are standard commercial items.

Finishes: Interior surface of vacuum chamber should be polished (..) then cleaned acetone and ethyl alcohol

Avoided materials:

  • brass contain zinc which out-gasses intensely when it gets hot, which can lead to ionization and flash overs.

Powder and metalurgy issues

NASA is also making their own machine but with wire not powder, t the 1 hour lecture is a good introduction to the metallurgy involved in EBM see here [73] (if not work then go to http://www.aeronautics.nasa.gov/electron_beam.htm# Select windows streaming in main page, then Windows Streaming Video then +window streaming in pop up window, some other selection options come up with the wrong video).


The initial test run prints will be made in stainless steel 30µ (Pre cool final printed parts from this powder is therefore likely to achieve a tolerance of 250µ) and chromium cobalt under 50µ 30µ?( Pre cool final printed parts from this powder is therefore likely to achieve tolerance of 250µ)metal powder [74]supplier[75], and then later the challenges of Titanium 4µ powder will be considered (Pre cool final printed parts from this powder is therefore likely to achieve tolerance of 20µ). See article on micro sls [76]. See example machine [77],See example of twin chamber 3D printer[78]. Though through subtractive machining we may be able to bring critical surfaces of most of parts down to 20µ. stainless is 316L grain size -45µ+10µ product purpose 3D printing good fluibility, 60gbp a kilo best price 80 kg per buy delivery 3 month. Powder is manufactured from cold rolled metal (e.g. 304 approx 1.8 Euro a KG 07/20111) by Electron Beam Melting of a rod of feed material which then is momentarily caught on spinning plate and flung thereafter, thereby solidify by cooling. See [79]

The magnetic metals lead to magnetizing of Iron based metal powders so should be avoided where possible, (the main magnetic metals are Iron, Nickel, Cobalt Iron)

The metal powders are not good to ingest or breath in so mask should be worn. The metal powders may get caught in the fine folds of your skin so gloves should be worn.

All metal powders can burn easier than solid blocks, the active metals are most flammable and difficult to handle; Titanium 4µ (other active metals include Aluminum, , zirconium ), then the moderate range metals e.g. Cobalt Chromium 50µ and finally low range Stainless steel 30µ . General fire avoidance should be followed, Avoid sparks and open flames, Avoid dust clouds( through dumping action of powders), and use appropriate tools. Design principles of fire avoidance should include; appropriate grounding of equipment, avoid excess mechanical friction in design. For active metals consider glove box contained nitrogen clean up environment or just a liquid based vacuum cleaner.

First layers are tricky to print  ; first layer must weld well to metal to stop part warping , because cold platform contact hot metal residual stress tries to snap build platform so build platform needs to be thick to resist this force, must also need to be reusable after each print must be milled.

Cost reduction by pre-processing billet metal in to metal powder within MetalicaRap through electron beam melting on to a spinning disk is also achievable later. For a particular steel unprocessed it costs about 0.5 Euro/ kg, but traditional metal stock for milling machining costs 20 Euro/kg, for metal powder up to 60 euro/Kg, these raw material pre-processing costs may reduce to 1Euro/kg by self processing.

Pros and cons of 3d metal processes [80](see below for link comparing tool head processes for more detail)

Safety issues

The penetrating ability of Xray produced is proportional to the voltage applied to the apparatus, So for your your old TV it was at 30KV but as long as you keep the electrons in a box that was no problem. But If you do like those crazy people in hospitals fire them all round the place precautions need to be taken, MetalicaRap keeps the electrons and the target in a metal box 7.925mm thick.

We can use this formula to calculate the dose rate,

R (rad/sec) = 50 x V (kV) x I (mA) x Ztarget / [r (cm)]2 x 74 where V is acceleration voltage, I beam current, Z constant for target metal type, r distance from target. Formula from Radiation safety manuel page 11 [81]

Lets calculate the dose inside the box we find;

The dose rate inside the chamber at 14 cm from a copper target operated like metalicrap at 100kV and 14 mA is: 50 x 100 x 14 x 29/ (7cm)2 x 74 = 560 rad/sec.

The recommended shielding from this level of radiation for working hours use is 1.2mm of lead. Our chamber is made out of stainless steel 304 each 3mm thickness is equivalent to 1mm thickness of lead shielding, our chamber is 7.925mm thick, So over twice the required shielding is provided by the chamber. So no further shielding materials are required.

Argon gas cylinder needs to be protected from falling over, as long as their is some ventilation the argon gas is no problem, a 60 euro cylinder should provide 3000 chamber purges in window option design ( background info; oxygen 21% of air argon less than 1 %, if oxygen concentration falls below 17% than can effect ill people for healthy people its ok down till 12%, if trace element of CO2 is also present hyperventilation can be triggered which allows no ill effects down to 7% Oxygen. this C02 trace approach is added to argon fire extinguisher systems).

Current status

We are based in Copenhagen Denmark at Labitat.dk our main engineers are also in Lancashire UK and Stanford California.

Wednesday night you can come to Labitat in Frederiksberg, Denmark and meet the team. Currently electron gun test rig and repstrap vacuum chamber, including pumps and gauges under electrical maintenance.


Get involved! The current team donates their free time, Current tech team; 1 Administrator, 1 software developer UAL, 1 electrical engineer, 1 Metal prototyper and 1 accelerator/ electron gun designer all part time

(Very occasional advice from; 1 Ultra-high vacuum metal deposition specialist, 2 physicist, 1 High-voltage system designer, 1 mechanical Design Engineer).

Do get in touch. See talk page and forum for more discussion.

Specialist Parts Chamber

CF flange Electrical connectors, Other (1x 140KV 2KW , , 6x SEM PIN diode pickups low current low voltage,

Main Deflector Coil driver solutions; a) Raster 30cmx30cm b) point and shoot Driver circuit choice Coil position options 1)7 degrees at bottom of gun 2)nearer build table.

3x 12mm Motor shaft Vacuum chamber motion feed through. 10-5 Torr Low torque version and high torque for 700W build platform motor.

Files and Parts

File:Assembly1 MetalicaRap V2.04.stl Pre detailing chamber to scale ( work in progress)

Click on file names to download file

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 deposition assembled tested. MetalicarapVacuumChamber parts Electron beam sintered by our system. MetalicarapVacuumchamber assembled tested. 5 Elements assembled and tested.

Downloads

MetalicaRap:Photos and Drawings

Self replication

Self-replication of a vacuum chamber runs into the "how to make a match box inside a match box problem".

Design review

Green Tech./Solar Cell production cost calculation

To produce thin film CIGS solar cells at under 11 cents per Watt peak. So Solar cells cost for a family 3 Bed house; Average Electricity usage 4200KW per year, 4200KW/365days*4.93 Equivalent Hrs peak sunshine= 4200KW/1800Hrs=2.3KW peak of solar cell panels required, at 11 cents per Watt peak the solar cell's would cost 253 dollars from MetalicaRaps plant plus cost of backing material, cost of inverter plus extras 1300 dollar, so it may offer an uninstalled system at under 1,900 dollars,( current price for uninstalled system is around 14,000 dollars (jan 2011)). (Calculation based on cloudy areas of world, 1KWatt peak solar panel system under 4.9 hours peak sunshine per day gives approx 1800KWh per year, A desert area at low latitude would be up to twice as good as this.)( For reference in a hot climate a 1.25 dollar/W installed financed system gives ;0.07 dollar/KWh over 20yrs, 0.03dollar/kWh over 60 yrs [82])

AMQ- A Million Questions section, no need to ask just add your thoughts

Note difference between minimum feature size tolerance, part final tolerance, printer machining tolerance, printer repeatability, post cool down tolerance. So should we design mechanics around 400µ Tolerance so it will still work if we don't get to 20µ/50µ. many commercial powder printers end up printing at 250 µ pre cool tolerance spec. But 400 µ may be more realistic since after printing,part cools down Kinks, coils & warps even if many printer can achieve feature size of 50µ. Though with post print subtractive ebeam machining flatten blobs through repeated surface spot melting, we could bring it back to 50µ? Depends on parts shape, use ..etc

How will the 10µ metal powder effect the mechanics?


Self reproducing tolerance critical parts design around? / buyin ?

CF flange 300µ CHECK WITH VACUUM DESIGNER,

Cathode surface 10µ CHECK WITH EGN 2 gun cross point spec.

Threads ETC 10µ check Mechanical eng.


How do we avoid materials that out gass in high vacuum and so stop vacuum forming.? ..... Two suggestions from an Open source day Copenhagen, Use electric field to pull waste metal away switch on in between beam vaporizing pulses so avoid bending beam.-ve may magnetize powder switching on and off , To protect guns have 2 motorized slotted sheets just above the powder, the hole where the slots cross is where beam enters -ve will slow beam down too much So N.G. as beam may reach 8000m/sn mechanical movement approx 1m/ S


Cathode tungsten pin is heated to 2500o C electron source overheating surrounding mechanical construction once been at 2500o C for 2 days. Ideas to reduce heating of surroundings 1. Not wire connection but use RF aerial to Aeriel connection, insulator which? Principles behind problem Types of energy exchange EM radiation , no convection (vacuum) , Conduction through supports.?

First layers are tricky to print WHY residual tension left in metal. powder thermal pre-treatment to degass and avoid powder balls and good flow.

  • seach in google scholar for METAL POWDER BEAM any thing about why the first layers are so tricky to print and result in most residual stress. [83], [84]


..

More Examples

Practical manufacturing walk through

Manufacturing walk through Time/Cost

Given Electricity is 2kwh per hour .5Euro/hr Part A Material; Stainless steal, Size; 300x300x200mm Weight; 15Kg 10µ Stainless powder (40 to 100Euro/kg) melt print 100µ Z layer thickness

1 minute per 100µ each layer See below; 1 minute per Z 100µ layer, each layer preheated 20 degrees Centigrade under melting-point followed by printed by beam5.33 minute per Every 10th layer Z axis correction see below ;

SEM ( part assumed to occupy 1/9 of whole print area; 1/9* 300*300=10 000<math>mm^2</math> measurement at every 10µ, SEM picture 500x500 pixel so 5mmx5mm, So for 10,000<math>mm^2</math> 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 = 100sec. plus time of mechanical movement of electron gun between .024m square patches at .03m per second is 12y strips each 0.3m strip takes 10 seconds to travel, so in all takes 120 seconds to cover build area( Risk of underestimate factor x100 ) 100+120=220 or 3.66 min flatten blobs through repeated surface spot melting 1ms per 70µ diameter spot area 4000x10-6<math>mm^2</math> ( 850µs duration & 150µs beam movement) 1/10 of part high(Risk of underestimate factor x2) ( 1/10*10 000mm2/ 4000x10-6 <math>mm^2</math>= 1x105 spots 1x105 spots*1ms= 100Sec 1.66min

Time so far 200* Z correction layers 5.33 Min each 1066 + 1800 printed layer 1min each = 2866 min ( 2.0 days) Cost 690 Euro materials 600Euro Electricity 90


MetalicaRap:Further future developments

Critical Design Review, Review of decisions made so far

In chronological order

1.metal.......................... Vs ..composite. ........... .........Why .Metals needed for high stress high temp contexts , engines, solar plants.. -ve ........................ +ve metals 100 % recyclable fits Cradle to Cradle Design See [85]

2.additive.Sintering........ Vs Subtractive EDM?.................Why Tool path manual intervention required.Consumables......... -ve ..Powder management ............ +ve

3.ebeam..Vs laser .....Why A)laser below 50W,small size part 5x5x5cm,slow B) Laser above 150W cost, permit , Wall plug efficiency , optics .-ve .not so cool , difficulty diagnostics...+ve solar cell printer possible

4.powder...........................Vs foil..........................................Why foil waste removal.................................-ve .Harder solid parts.& powder management...... +ve

5.vision & correction sub. Vs one pass blind process ... ....Why .reliability Verifiable tolerance............................................. -ve ...Complexity..................... ................ +ve

6.gravity hopper................ Vs twin chamber........................ Why avoid old powder reuse fresh every time easier prep ............ -ve their must be a good reason to use 2 build chamber? e.g. EOS is. +ve

7.one static top of chamber gun with just sensor ring on cartesian axis Top gun shoots through sensor ring from top........... Vs two gun would ensure spot size on vaporisation but could add in again if existing does not work. Why So SEM near table Sensors PIN Diodes 164$ each not 64x PINdiodes . Pros & Cons of two guns design

8. Passive cooling Vs Water cooling for 5KW gun .............Why .Air cooling fins on cathode head block and on high voltage copper enclosed connector plus ducted fan & fins -ve need to be FEL modeled to check conductance. +ve Simplicity no water ( though could add later ).


9 Tungsten thermionic cathode filament.2600C. Vs .hot Field emission cathode ..Why Cost of IrCe, field emission required UHV, .Thermionic is OK in high vacuum... -ve hot spots poor beam focus reduced filament lifetime, gas load in metal powder more critical due to filament sharing same space.... +ve cheap no need for window to separate gun chamber from powder chamber


10. .Internal coils in a 304 can. Vs .External coils .... ....Why .to achieve small enough spot size as spherical aborations are zero on axis of lens and increase as you move out, ... -ve need for barrier between coil pole pieces and beam for vacuum, construction of can for air cooling +ve no contact between coils and vacuum

11. Split hopper ..... Vs ..One large dispenser hopper.....Why ..cost chamber size less force required on motion feed through............... -ve ..complexity of refill mechanism ( shutter with knife edges ) ............... +ve. initial lower cost

...................................... Vs ...............................................Why ...................................................... -ve ..................................................... +ve.......................................

list in importance order, bold text indicates more thought required

General Information

Solar cell thin film deposition

Thin film deposition summary by material [86] RF sputter is another option for increased solar cell production rate [87] uses the electron beam to resonate a cavity to produce an RF magnetron) .

Useful links

EBM introduction [88]

Images EBM / EBW [89]

General background Videos EBW see here [90]

Back ground Information on Electron beam processes; electron beam welding / vaporization , EBM 3D printing(2),

Scanning electron microscope SEM background(3)(4).


2. http://www.arcam.com/technology/ebm-process.aspx

More technical sites

3. http://www.matter.org.uk/tem/sitemap.htm ,

4. http://www.uga.edu/caur/semindex.htm

5.practical advacned technical infomation; Transfomer winding [91]

Self Replication Engineering Options See section 2. [92].


EBM technical background lecture See here [93]


General background Videos EBW see here [94]

MetalicaRap:Tool head processes discussion

Futher Reading

Vacuum chamber principles; Essential reading before you weld/construct your vacuum chamber, Basic Vacuum technology by Varian

Maths behind vacuum processes ( Not for the faint hearted )[95]


Online Design Tool: Build Speed Calculator for metals including Aluminum,Stainless,Tungsten


Old general infomation

Click for link to Old Information section