# Old information

## Old file and parts information

MetalicaRap V2.5 (old)

SMPS insulators ( ensure G code objects have solid walls in nylon) File:Nylon1 elements of smps assembly v1p00.stlFile:Nylon2 elements of smps assembly v1p00.stlFile:Nylon3 elements of smps assembly v1p00.stl

MetalicaRap V2.00 (old)

File:Assembly1 MetalicaRap V2.04.stl Pre detailing chamber to scale (old)

## Old research infomation

o special chamber materials are necessary since you can get an electron beam to operate in a vacuum of around 5x10^-3 Torr. Buna rubber seals and low out gassing glues can be used for sealing components and costly vacuum flanges can be avoided in much of the construction. Simple pipe threads sealed with teflon tape or even glues can be used along with cheaper KF flanges. You dont need metal sealed flanges such as the conflat or wheeler flange.

There are three methods to triode gun biasing used in EB welders: Resistance bias: The oldest and simplest method. The filament is connected to a potentiometer and limiting resistor to the negative HV terminal. The wehnelt cup is also connected to the negative of the HV supply. The theory is if you short the filament to the wehnelt cup, you get full bias equivalent to saturation in a BJT transistor, unlimited current will flow. Introducing a resistance will allow one to control the current flow to the filament. The old EB machine used whats called a 100 position switch. Basically a pcb with 100 contacts arranged in a circle with a wiper that is controlled via a knob or servo/stepper motor. Between each contact is a high value and power (2-5W) resistor.

Transformer bias: If the potential of the filament is raised above the wehnelt cup then you put the triode is cut-off. For a 150kV EB machine this is somewhere in the order of 2-3kV, less for lower voltages. An isolation transformer powers a HV rectifier circuit with filtering and connected between the filament and negative of the power supply. As the biasing voltage is dropped, beam current rises. Be sure to include a current limiting resistor as you can easily cause a surge if you loose power to your bias circuit. Not exactly simple as the transformer adds a lot of cost but it could be done with a neon sign transformer or possibly a modified microwave oven transformer.

Vacuum Tube(Valve) bias: This is a complex system that was developed by Leybold Heraeus in the late 1970's in cooperation with IKE (a German technology institute which I cant spell). It is commonly referred to as the IKE system is also used by Steigerwald who is a partner of PTR. It uses one or more E130L vacuum valves to regulate the beam current to the filament. Inside the HV power supply tank a few circuit boards that accept a reference or as the IKE system calls it, a "command" signal. This is sent through an analog comparator circuit which then monitors the actual beam current vs the command signal and then outputs a bias signal to the E130L. the E130L is actually carrying the current through it and the current flow is regulated by the bias signal. Its the most complex of the three and I would avoid it because its over-kill for simple melting. It is however, very accurate and closed loop in its control making it very stable.

• Nickel for some fittings NG as has zinc in.

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

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. [1], [2]

..

• . 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.) used numeric method see spread sheet calculation.

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$mm^2$ measurement at every 10µ, SEM picture 500x500 pixel so 5mmx5mm, So for 10,000$mm^2$ 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 Remove metal by Vaporization 1ms per 70µ diameter spot area 4000x10-6$mm^2$ ( 850µs duration & 150µs beam movement) 1/10 of part high(Risk of underestimate factor x2) ( 1/10*10 000mm2/ 4000x10-6 $mm^2$= 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

Part B

Material; Aluminum Size; 300x300x20mm Weight; 1.5Kg Aluminum 15Euro 10µ powder, melt print 100µ Z layer thickness

Time 20* Z correction layers 5.33 Min each + 180 printed layer 1min each = 287 Min 4.8 hours

Cost 27 Euro materials 22 Euro Electricity 5 Euro

Powder

injection molding powder

Aluminum powder 15 Euro/Kg 10µ

Carbon chromium 40Euro a kg. 74µ

Stainless powder 40Euro/kg 10µ

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? Normally use copper wire to make up "CF flange".[3]

As the main consideration is avoiding non MetalicaRap conventional machining, can you make the copper wire pinch/seal of a CF flange out of the edge of a purchased plain rectangular plate? Is there a better approach? Print the coper flange then uncoil?

NB. It can also weld finished parts together placed in the chamber, the chamber is twice as wide XY as build area approximately, as it needs space for removable metal powder hoppers!, can you use this extra space?,

Chamber 1.3m high, 1m wide, 0.6m depth powder build chamber is 0.3m High 0.3m Bredth 0.3m wide

Door size is up to you, could be a full side eg 1.3m by 1m.

Outstanding questions,

Which insulator for cylinder holding 100KV terminal in electrical feed-through in to chamber ? PTFE? See page 5 [7] Which insulator to secure tungsten wire? Which ceramic?

Which wire for coil windings ? (4A) telflon coated copper? Maybe? Which thermal conducting material for anode support structure? copper 20100 alternatives? See page 5 [9] What insulator for surrounding the central stalk that makes the internal electrical connection to the hot IrCe metal ring which goes up through the cathode stem?

• Self study the material science to help us with its development free at this site[4]'' STUDY

Rejected design approaches

• Cartesian Electron Gun A 600W (60KV 10mA) close to build platform on Cartesian X,Y support. Providing subtractive micro vaporizing and vision system

So we are no longer restricting the design to known 2 gun technological solution, (i.e. 2 guns. One close to the target and one far from the target, 1m away (having functions SEM / Micro vaporizing and melting across build area respectively)) Carbon nanotube coated needles have been used and may be worth investigating

.General material issues;

The materials usually have limited lifespan due to sublimation at higher temperatures.

Design Tools

Electron Gun Collector(/cathode) Simulation Software (not for the faint hearted!)

Some people suggest the most acurate way for Electron gun design is it to be done manually with formula through consideration of 3 effects on electrons; Electromagnetic fields, laws of motion, Space charge (electrons pushing on each other). Here are two formula explanations and manuel calculations of pierce guns,; first a large non filament gun example See here [5], Second an example of Pierce weld gun See fig.3 [6] ), See final equations to give velocity of electron in equation(1.9) and beam current as (equation 2.10)See equations here [7] .

Others argue simulation software is accurate enough and necessary it was used 1980's onwards to refine design of the electron gun, See example design process of a gun cathode See page 19 here [8].

Cathode voltage choice controls minimum penetration depth of electrons energy in to the metal powder/target, beam current choice influences power transfer rate from electron beam to metal, once cathode voltage and max beam current are decided, Electron Gun Collector/cathode Simulation programs are used to design the appropriately cathode anode surface shapes to achieve the said max beam current at the applied cathode voltage, while maintaining at the gun crossover point the required beam power (Watts) at the optimum gun crossover diameter (cm) (gun crossover is situated in the middle of the anode see main electron gun diagram above), the gun crossover diameter is the primary factor controlling the final beam spot size on build platform/target ( other negative effects come from coil imperfections and aperture electron wave interference patterns) .

• For comparison try to get hold of open source charge particle/electron trajectory analysis programs, some times called electron gun computer simulation programs, like SAM or ULTRASAM (USAM) (By m Tiunov BINP russia )or maybe TREDI with modification?Get here[9], ( # -indicates confirmed as currently for commercial sale with no useful free trial version, #EGUN [10] / #EGN2w, windows version/ #EGN2w is currently seen as obsolete but will work fine for us, byBill Herrmannsfeldt, Reinard Becker University of Frankfurt/M, [11]) or #TRAK or #MAGIC). GENERAL RESEARCH

But for now we will try with a general magnetostatic program like Poisson for tracking through coils and calculating resultant forces on coils ( later we track beam live with UAL see above ) and unfortunately we have no solution for cathode anode design as we require space charge calculations and temperature and field regime "Schottky emission" which this CPO student limited version blocks, but you can get to know the principles behind it by play with CPO, ( CPO Boundary element method simulation program student version for standard pierce gun cathode shape/ solutions, Download CPO here [12] install and run in XP compatibility mode! (right click properties / compatibility tab) , Pictures [13] Installation help[14]).

So in general terms Run Geometric modeller to aid the production of the required input files for automesh, upon running automesh the problem set up is achieved. Once automesh has finished running and creating the problem file ( XXXXXXXXX.T35 ) then the solver program Poisson acts on this file to do the simulation of the design, The Gun simulation is an magnetostatic problem so is solved through Poisson equations ie uses subprogram called "Poisson"( We do not use RF cavities in the electron gun so ignore programs for tuning them, with FISH in the program name) . See summary of POISSON suite input and output files here input & output files using POISSON suite. You can confirm you output with approximate hand calculations at centers of coils See formula here , Deflection of beam by coil here [18] , coil Magnetic field B calculations [19], Background Coil design[20].

Old self replication method

Possible self-replicated vacuum chamber: Anders used Blender to draw this rough sketch of a vacuum chamber made from hexagonal parts printed in a MetalicaRap.

Hexagonal x40 halfhexagonal x16 endpieces x16, 384 bolts (what does this mean?), copper wire, main door can use a Viton O ring perhaps, or a metal to metal seal with vacuum oil or vacuum wax as a sealant. old solar cell material deposition rate of a few micrometers per minute / electron beam heating evaporation deposition EBPVD [21] / possibly a micro pulsed electron deposition process,

Calculations for 1m cubed box design - too expensive Step 1 - Required thickness approximation

I've calculated plate thickness, constrained by maximum deflections of 0.01 & 0.03 inches = 0.254 & 0.762 mm and pressure differential of 1 atm sea level for the largest dimension plates, ie electron gun tube length 0.80 diameter .032 on top ; H 0.8 x W0.8 x Depth 0.4 (assuming smaller plates will have less deflection)

Online calculator for fixed rectangular plate (Bypass calculation limit by clearing your cookies)[22]

old links before TWI blocked pages 1. http://www.twi.co.uk/content/spasaug2006.html

Simple just plate chamber with electron gun tube length .080 diameter 0.32 on top ; H 0.8 x W0.8 x Depth 0.4 area 2.56

Material

Stainless Steel 304 (check this)

Youngs modulus E GPa Stainless Steel 207

Poissions ratio v 1 0.3

Individual plate sides of chamber given 0.253097 mm max plate deflection

Width Lx mm 800

Length Ly mm 800

thickness needed TBA

Width Lx mm 400

Length Ly mm 800

thickness needed TBA

Width Lx mm 400

Length Ly mm 800

thickness needed TBA

Individual plate sides of chamber given 0.761671615 mm max plate deflection

Width Lx mm 800

Length Ly mm 800

thickness needed 15.8 ( 15.8mm ( 5/8inch)( deflection 0.683mm) 2098 euro per m sq.)2.56 x 2098 do again BAD PRICE? = 5370 euro(( do we need to go up to 316 stainless?)

Width Lx mm 400

Length Ly mm 800

thickness needed TBA

Width Lx mm 400

Length Ly mm 800

thickness needed TBA

Material

Aluminium

Youngs modulus E GPa 62.053

Poissions ratio v 1 0.3

Individual plate sides of chamber given 0.253097 mm max plate deflection

Width Lx mm 800

Length Ly mm 800

thickness needed

Width Lx mm 400

Length Ly mm 800

thickness needed TBA

Width Lx mm 400

Length Ly mm 800

thickness needed TBA

Individual plate sides of chamber given 0.761671615 mm max plate deflection

Width Lx mm 800

Length Ly mm 800

thickness needed 25 Aluminum plate (deflection .583mm) 2.56 m sq. 2000 euro[23]

Width Lx mm 400

Length Ly mm 800

thickness needed TBA

Width Lx mm 400

Length Ly mm 800

thickness needed TBA

another possible chamber with no electron gun tube.

Simple just plate chamber no electron gun tube ; H 1.6 x W0.8 x Depth 0.4

Material

Stainless Steel 304 (check this)

Youngs modulus E GPa Stainless Steel 207

Poissions ratio v 1 0.3

Individual plate sides of chamber given 0.253097 mm max plate deflection

Width Lx mm 800

Length Ly mm 1600

thickness needed 40.6 do again

Width Lx mm 400

Length Ly mm 1600

thickness needed TBA

Width Lx mm 400

Length Ly mm 800

thickness needed TBA

Individual plate sides of chamber given 0.761671615 mm max plate deflection

Width Lx mm 800

Length Ly mm 1600

thickness needed 28.2 do again ( 1inch 25.4mm 1200 euro per m sq.) so 6.4m x 1200 = 7680 euro(( do we need to go up to 316 stainless?)

Width Lx mm 400

Length Ly mm 1600

thickness needed TBA

Width Lx mm 400

Length Ly mm 800

thickness needed TBA

Material

Aluminium

Youngs modulus E GPa 62.053

Poissions ratio v 1 0.3

Individual plate sides of chamber given 0.253097 mm max plate deflection

Width Lx mm 800

Length Ly mm 1600

thickness needed 59.3

Width Lx mm 400

Length Ly mm 1600

thickness needed TBA

Width Lx mm 400

Length Ly mm 1080

thickness needed TBA

Individual plate sides of chamber given 0.761671615 mm max plate deflection

Width Lx mm 800

Length Ly mm 1600

thickness needed 41.1 40mm Aluminium plate 6.4 m sq 4708 euro[24]

Width Lx mm 400

Length Ly mm 1600

thickness needed TBA

Width Lx mm 400

Length Ly mm 800

thickness needed TBA next steps - Material prices ?? - using next larger standard dimensions ?? - factoring in compressive stresses from edge loading (buckling)

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)

• Put this type of bake able knife edge vacuum flange[25] in to freecad[26] for 1 inch 2 inch 6 inch and 14 inch pipe and upload the 3D result to the files and parts section on the site, owned by username ;...........likely finish date :11 feb 2013.........emotional status..........great

The electron gun (1.KW, 100KV)

Which metals for cathode/anode/wehnelt electrodes? '(tungsten / tungsten /molybdenum,)

Which metal for "soft iron core" surrounding coil windings, unalloyed soft iron for yoke e.g. "Hyperm O", cobalt iron alloys for pole pieces if needed e.g. Permendur Vacoflux

Which thermal conducting material for anode support structure? copper See page 5 [9]

Thermionic emission regime,Tungsten ribbon hot filament tungsten at 2500C 0.3 A/cm2(melts at 3410C)?or Thoriated Tungsten 1.16 A/cm2 or Tantalum 2.3 A/cm2(melts at 2996C)

• 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 ;.......thanks for all the help thomas
• 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 [27] Results are unverified as of 20:20, 26 October 2011 (UTC) - 2nd opinion required !
• /eZ great work in the design!

Nickel(1453 C melt), stainless steel(1400 C melt) and molybdenum (2617 C melt) are best materials for electron guns as (others like brass contain zinc which out-gasses intensely when it gets hot, which can lead to ionization and flash overs.) Ceramic or glass are good for insulating elements and can cope along with tungsten(3410 C melt) at over 2600 C creates a high enough current by thermionic emission.

• Which insulating washers between cathode and 1st anode (6KV) ? Which ceramic? in a 10$^-$$^4$ Torr vacuum Colored red in this diagram of electron gun [28] owned by username ;...........likely finish date :.........emotional status.......... 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.

• Which insulator and structural material for insulating beam between cathode and anode (120KV min), which ceramic? Colored red in this diagram of electron gun [29] owned by username ;...........likely finish date :.........emotional status..........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.

• If we went down the cheap window development path then it would have to be a 5-50µ Ti foil window, which is a factor of a thousand times too poor at conducting heat away, so multi guns from different angles would not work, moving beam and spinning build platform might work ( quantify rotation needed ) but alignment and weight 230kg of powder is impracticable?

• Thermionic and field emission regime with field emission cathode disadvantage requires 10 − 7 Torr vacuum, At this vacuum mechanical feed through s need to be magnetic as o rings no long work at this vacuum, the over 35Nm torque required for the build platform is pushing the design probably too hard so this is an obstacle for moving to the thousand times longer lasting expensive filaments like IrCe. At this vacuum baked-out Vacuum systems are required, the Vacuum system is heated up to 200 C for 24 Hr under vacuum but give the advantage of electrical break down no longer regarded as a threat.
• Schottky emitters, requires 10 − 7 Torr vacuum / Zr coated tungsten tip ?, e.g. IrCe or LaB6 80 A/cm2// Difficult to stop it reacting with its own support material.

What insulator for surrounding the central stalk that makes the internal electrical connection to the hot IrCe metal ring which goes up through the cathode stem? Do later on UHV version. NiCr Alloy (10-16)

• 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 [30]owned by username: cclor likely finish date : 28/09-11 emotional status: quick-ish. Too expensive for now go for cheaper option great work we may use later!