MetalicaRap:Tool head processes discussion

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SLS vs EBM

SLS and EBM have some similarities: one puts down layers of powder, and one scans a beam over each layer of powder to get the powder to stick together in the right places.

EBM has some advantages over SLS. (See SLS Printer#SLS vs EBM for advantages of SLS over EBM).

  • electron beam melting produces parts that are void-free, and therefore full density and full strength.
  • The parts that generate an electron beam seem simpler to replicate than the parts to generate a laser beam.
  • An EBM machine can do both additive machining -- melting new powder grains onto a part -- and also subtractive milling -- vaporizing outer layers of a part.
  • in principle, it seems possible to EBM materials that are completely transparent to laser beams (and infrared light).
  • ... other advantages ...


Naive questions: The EBM machines I've seen photographs of generate the electron beam at the top, then focus and steer the beam to strike the appropriate spot on the powder at the bottom. That requires high vacuum -- otherwise the electron beam is completely absorbed by the air or other gas. is it possible to generate the electron beam on a moving toolhead a short distance above the appropriate spot on the powder? How short does the distance traveled by the electrons through air need to be, in order that at least half the energy of the beam makes it all the way through to melt the powder, rather than heating the air/nitrogen/argon atmosphere? See the artist's conception of a potential "Cartesian robot gantry" for non-vacuum electron beam welding[1]. Wikipedia: electron beam welding#In-air welding