I blow glass and make neon as hobbies and am the chief engineer at Fluxeon which makes induction heaters, useful for heating the internals of a vacuum tube to outgas them so maybe I can throw in here a bit.
The first thing you'd need to do is pay to have a very thorough engineering analysis made of an existing tube known to have a long live. You'd want to learn, among other things, the type of glass used, the type of glass/metal seal used, the atmosphere (composition and pressure) inside the tube, the chemistry of the electrode metals and their surface treatment. The last part is probably the most important part. As far as the glass blowing goes, it's not really practical to do this by hand. Even though some people on this list are playing around with pinch seal, flying lead tubes, those aren't going anywhere, IMO. You'll need an actual multi-pin glass base that is pre-manufactured and is welded to the envelope as one of the final steps in manufacturing. If you watch some of the u-toob videos of vacuum tubes being made, you can see how the base is made. Pins made of the proper transition metal are inserted into a metal mold. A gob of molten glass is deposited into the center of the mold and the mating half is pressed down, forcing the glass around the pins and into all the nooks and crannies of the mold. The temperature of the mold, the temperature of the glass, the quantity of glass in the gob, cooling time before ejection and a bunch of other things in the process that have to be tuned and optimized. Many years ago I worked for an engineer named Ed Kay who was the chief engineer at the Tung-Sol tube plant in NJ before it closed. I was interested in ham radio and a little bit interested in tubes so we talked tube manufacturing a lot. I wasn't yet interested in glass blowing so I didn't spend too much time on the subject of the glass manufacture. I did get some knowledge from him, however. Making the envelope for a side-view Nixie is fairly easy using glass tubing and scientific glass blowing techniques, though you'd want to automate that too, if you plan on making very many tubes, something you'd have to do to justify setting up and running the base making machinery. Making the envelope for the non-round top view tube would be quite complex. I'm pretty sure those were deep drawn similar to the way beverage cans are made but I've never seen it done. I'd probably focus first on the round side view tube. In terms of vacuum, it depends on the production rate you have in mind. For tiny volume, hand made tubes, you'd need a pretty high vacuum - in diffusion or turbomolecular pump range - and an oven to outgas the electrodes. For high speed production, the tube, still hot from having the base welded on would go onto the vacuum manifold where vacuum is applied. Simultaneously, the internals are heated with an induction heater to outgas the electrodes without requiring a high vacuum. A getter may also be used. The vacuum requirement is modest since the tube is already hot and the electrodes are heated red hot. John On 08/28/2013 12:15 PM, gregeb...@hotmail.com wrote: > I've always been curious what level of glassblowing skills and cost/quality > of vacuum equipment one would need to make their own tubes. > > I had given some thought to attempt to make my own nixie tubes and other > ionized gas devices, then concluded it would take me several years and > several thousand US $ to make anything that would have a decent lifetime. > -- John DeArmond Tellico Plains, Occupied TN http://www.fluxeon.com <-- THE source for induction heaters http://www.neon-john.com <-- email from here http://www.johndearmond.com <-- Best damned Blog on the net PGP key: wwwkeys.pgp.net: BCB68D77 -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/521E2B4D.50505%40neon-john.com. For more options, visit https://groups.google.com/groups/opt_out.
