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why i had to kill my beloved electron beam project after running the numbers and working through the failure modes, I just cant justify this machine anymore its a high voltage death trap this design needs 30–60 kV to drive a usable beam that’s insta dead territory insulation, arcing,... show more
265,290 views • 1 year ago •via X (Twitter)
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link to the video keep in mind this is only 200grams worth of powder in a printer you will have dozens if not hundreds of pounds of this in one area

terror

theres a new ebeam litho tool at stanford that arcs almost every other month it's not even funny anymore, thankfully no powder of any form allowed in there..

excuse me WHAT

As a former CRT engineer, I will say that your absolutely right that this project would be pretty challenging. My main issue is that if your workpiece is in the same vacuum envelope as the electron gun you will have major issues with outgassing from the workpiece poisoning the cathode and reducing electron emission. I ran experiments where I validated cleaning/decontamination methods by enclosing electron guns from our commercial projection product in sections of glass neck tubing but instead of an aluminized screen I put small pieces of stainless steel that had gone through different cleaning steps in front of the guns and connected them to the 40kv anode supply. By biasing the tube on to a specific beam current under a given set of conditions and monitoring the decline in beam current as the steel target outgassed, I figured I could determine how effective a given protocol was. This turned out to be incredibly effective method with a HUGE delta between control samples and the 3 methods I was evaluating. The biggest takeaway was that even stuff most people would consider extremely 'clean" is just NOT. The control samples got: Bright dip (heated solution of strong acids to remove the surface layers of metal) Ultrasonic bath in 18MΩ deionized water Ultrasonic bath in acetone Ultrasonic bath in isopropyl alcohol Final bath in deionized water 24hrs min in an argon purged cabinet at 250 degrees When these were hit with the electron beam, the emission at a given bias level fell 95-99%+ in 3 minutes. The evaluation samples got, in addition to all of the above, either: Partial pressure hydrogen (5% hydrogen/95% argon introduced in a vacuum) firing at 1200C Hydrogen firing at 1200C (hydrogen flow-through furnace with a natural gas flare to burn the hydrogen at the far end) Plasma cleaning Various combinations of the above. The best performing samples got both partial pressure hydrogen firing AND plasma cleaning. Their emission drop was between 3 and 5% at the 3-minute mark but unless you are prepared to go through all that with all your workpieces you would probably have major cathode poisoning issues. Of course, you could always keep the workpiece and gun envelopes separate, but that presents all sorts of issues on its own. I love the IDEA of welding with an electron beam because you can use magnetic or electrostatic deflection to move the beam over a weld path electronically but there are a LOT of potential issues that make me think a laser is just way easier.

yeah , normally on these you have a chamber pump and a beam column pump (pumps) do you recall what your electrons sources were in those days ? for additive we use Lanthanum hexaboride since it has a much lower work function than tungsten wire and it last considerably longer

I decided the same on my e-beam system. Mine wasn’t as high voltage, only 10kv, but it was 1.5 amps. I sneeze wrong and I die.

e beam is not even that high…. what were you making 💀👀👀👀

Oh you're working on an EBM ? I always wondered if you could just break open old vacuum tubes and do this. (minus the problem with mercury)

LMAO you mean like this , my first experiments were doing just that I DO NOT RECOMEND MESSING WITH CRT TUBES , THE FLYBACK TRANSFORMERS IN THESE TVS ARE SCARY AS HELL YEE BEEEEE WARNEE
