Talk:MetalicaRap
MetalicaRap Design question feed back / discussion. Add your ideas here!
Safety hazards
That thing would produce a lot of x-rays. Did not see that mentioned in the article - sorry if you guys already thought of that, just don't want any of you guys getting dangerous x-ray exposure when experimenting! Keep up the good work but please stay safe with high voltage at low pressure. It really is dangerous. Dmytry 19:09, 15 May 2011 (UTC)
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 )
Q:. Target metal surface temperature measurement would be a big advantage, Do you know of a electron bombardment based remote temperature measurement approach?
A1: ???
A2: The bombarded surface gets red-hot, right? Is it possible to put an infrared camera inside the chamber -- or an off-the-shelf webcam with its infrared filter removed -- and calibrate it using some test objects in the chamber heated to a known temperature?
Q: Some EBW machines put the workpiece outside the chamber, in open air. What materials are useful as a "window" -- to pass the electron beam, but hold the air out of the vacuum chamber?
I don't know how hard can be to make it, but this can be a solution? http://en.wikipedia.org/wiki/Plasma_window http://www.newscientist.com/data/images/archive/2390/23904801.jpg
Q: how will vacuum and powder work, won't that mean some gas will be trapped in the powder and each layer you make some of it will be released and will have to be compensated for?
--Robinmdh 14:03, 18 March 2011 (UTC)
Other ideas.
Q: Printing in air at 1 atmosphere would mess up the metallurgy, but a high vacuum is expensive. What about a low vacuum with a high shield gas percentage?
Answer ; In some existing low pressure weld EBW systems they enclose electron gun in a high vacuum box and send beam through window in to work piece in low vacuum air, keeping the work piece within 3cm and they get a 1cm diameter beam spot. Then shield the room with 1mm to 10mm of lead. So you can see that a beam will expand to 1cm diameter over 3cm of low pressure air travel. To get rid of all high vacuum the gun would not work as the electron gun is over 3cm's long, the cathode + anode+ 2 focus coils+ deflection coils is about 60cmn long may be you could get them down to less? So the electron gun needs a high vacuum at least.
A.High vacuum is a box 6/8mm steel + vane pump,(used 600E) + oil diffusion pump (used 800E) (possible make self) + Door Seals + electrical connectors + Gauge (used 80E) + circular motor feed through s +Powder deposit/electron gun/ power supply and control
B.low vacuum with shield gas is a 2mm Box + ( cylinder of Nitrogen or Argon (XX?E)or Nitrogen plant) + Door seals + electrical connectors + Guage(used 80E) + % oxygen sensor +circular motor feed through s + Powder deposit/ power supply/ control/ electron gun vacuum box vane pump,(used 600E) + oil diffusion pump (used 800E) (possible make self)
In case A the beam can be around 100µm tolerance 20µ m, over 1m travel (max 7 degree divergence out of gun, so build area 30cm x 30cm ), the metalurgy is good enough for jet engine parts.
In case B the the beam can be around 1cm tolerance 200µ m?, travel over 3 cm (build area 3cm x 3cm ) metallurgy not so good.
I hope that's a help? ( I have not done the maths on beam spread rate in low vacuums, so the above is from what I have read. )
Robinmdh, all good questions, which I'm interested in knowing the answers to. Since you're a dev, and I'm a dev, and the MetalicaRap team is all devs, want to ask them in reprap-dev? --Sebastien Bailard 09:18, 22 March 2011 (UTC)
For the vacuum chamber, I don't thing multiple parts will be a problem. Simply make them interlocking and to a close tolerance and with built in threaded holes etc. for fasteners, and apply vacuum grease /wax or there is probably a caulk like substance available, for a good seal. The thing to remember is that there are a wide range of useful products that have been developed for working with vacuum. If there is a mechanical hole it tends to be a relatively big hole and you can detect such holes in various ways with soap bubbles and ultrasonic sensors of the type HVAc people use. The second generation unit vacuum chambers will not be a problem I think. The number of parts is the only way really to surmount the make a matchbox in a matchbox problem without paying tons of money for more stainless steel sheets.
