Hi Terry, this is great info, I am always surprised what kind of information folks here have ;-) really thanks for sharing it!
So, what kind of seals was produced this way? Were it seals for vacuum tubes with electrodes arranged in a circle? This process is completely different from what I have seen in documetary so far.. look here: http://youtu.be/GDvF89Bh27Y?t=20m55s In the seal division, did the carbon forms consist of bottom and cover or did the glass just flow by its own weight into the carbon mould? Was there any inert atmosphere to prevent the metal oxidizing or the temp was so low that it was opened to air? I would be really interested in photos of your stuff, that would certainly help! I hope You will find it! There is a question what kind of glass and metal use for the seal.. I chose the tungsten wire and borosilicate glass. I dont have to anneal it during work (however I plan to anneal entire tube after tip-off), I dont have to be afraid of cracks.. The tungsten wire is also very resistent to fire, so I may expose it to flame repeatedly during making the seal. All other common metals would melt immediately (iron, copper, nickel..). But the disadvantage of that combination is that the quality of the seal depends on thickness of layer of the tungsten oxide on the wire as the glass makes bond with the oxide, not the tungsten.. It could be difficult to control it in a furnace.. And also the boro glass needs working temperature at least 1200C, quite a lot compared to 900-1000 for lead glass. 1200C is a limit temperature of common lab furnaces.. Dalibor 2013/8/29 Terry Kennedy <terry+googleb...@tmk.com> > On Wednesday, August 28, 2013 1:28:00 PM UTC-4, Dalibor wrote: >> >> Why we (pinch seal makers) are not going anywhere? Look to Rodan CD47, >> there is also pinch seal.. But it would be definitely better to have >> disc shaped stems.. There are companies that produce them, but for >> high prices. I will definitely try to build a machine for making flat >> stems, but that is far future.. > > > Perhaps I can provide some info. I used to work in a glass factory, where > I was one entire department (bead). I'll provide as much info as I can > about the processes I performed, and what I know about the other processes. > > Surplus pill presses (from pharma prototype labs, not the huge machines > used for pill production) were fitted with custom dies which were used to > form a glass + wax + dye mixture into a raw bead. There was an amazing > amount of tolerance for most beads (after all, I was an 18-year-old kid at > the time - the mid-1970's). The beads were collected in a hopper. I built > the hopper and gizmo to move them into there (and blow off any loose glass) > by using microswitches triggered at various points by the up-and-down > movement of the press. They operated air valves which would then blow the > finished bead off the press platen. This worked well for simple beads > (1-hole round, 2- and 3-hole oval), but the more complex ones were made in > very short runs (mainly for aerospace companies) and I often moved those by > hand, as they would break or deform if just blasted into a hopper). > > I'd then take the beads from the hoppers and pour them into Inconel mesh > baskets and run them through the sintering furnace via conveyor belt. This > would evaporate all of the wax and slightly melt the glass, fusing each > bead into a solid unit. I don't remember the temperature the furnace, but > it was dependent on the glass formulation used, anyway. I'd measure some > random beads for QC and then bag them up for transport to the seal facility > about 20 blocks away. With 3 presses running, I could produce several 1-lb > bags per day, each countaining thousands of beads. > > At the seal division, other workers would take the beads (from me and > outside suppliers), metal leads, and (if needed) other metal parts and > position them in carbon-block forms. These forms would have a grid of > anywhere from a dozen to hundreds of complete seals. These were run through > a furnace which was fueled by hydrogen gas. The beads would completely melt > and flow around the wire leads and other metal parts. After cooling, they > would then be removed from the forms, inspected and packaged up to send to > customers. I'll see if I can find any of the stuff I took when I left that > job - I have a box full of assorted completed seals, a clear plastic resin > block with some of the company's most popular products, and one of the > carbon forms. > > -- > 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/d5759d56-d017-44a2-b5c8-709b40d84a91%40googlegroups.com > . > > For more options, visit https://groups.google.com/groups/opt_out. > -- Dalibor Farny http://dalibor.farny.cz -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. 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