3D printing in Tungsten

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3D printing in Tungsten

Postby Jake Gray » Wed Oct 22, 2014 1:32 pm

http://www.smitroentgen.com/en/capabilities/

I don't think the accuracy or density is what Doug needs for grids, but pretty interesting none the less. 230x230x200 mm max size, 100um minimum feature size. No idea what the surface finish looks like, but hey, its printed and in Tungsten!
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Re: 3D printing in Tungsten

Postby Doug Coulter » Wed Oct 22, 2014 4:55 pm

We will check this out. The main question is their attitude/price on "onesies".
We did find .009" tungsten carbide centerless ground rods we'd like to try. A bit less electron emmision might be good. Pure W is noticeably better than the stuff doped for high emmision. Just another peak we haven't seen the other side of, yet.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: 3D printing in Tungsten

Postby Jake Gray » Thu Oct 23, 2014 11:56 am

I think they primarily make x-ray imaging components for Philips, and I suspect they kind of charge what they like as it will still be cheaper/better than the alternative. If they are independent they might be interested in helping just for the challenge.
They may also be owned by Philips as the two guys mentioned as presenting their products are both from Philips Healthcare. They may have a harder time knocking off a favor in a large corporate setting. I suppose worth an email to ask.
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Re: 3D printing in Tungsten

Postby Doug Coulter » Thu Oct 23, 2014 10:56 pm

I figure it can't hurt to just call on them. They might like being able to say they made this awesome thing as part of their advertising/image, after all. If they are one of those "100k/month" types (demand a rate of orders, not an amount), well, they probably aren't interested in me anyway. But if they can do tungsten, they can probably do almost any high-melt stuff - Be, C, you name it. There's a lot of magic around using Be in a fusor, but it's real difficult to deal with at all, and also live through the process. I just had to leave this here...
Asimov_Sucker_Bait.pdf
Be can be dangerous, however....
(145.81 KiB) Downloaded 453 times
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Re: 3D printing in Tungsten

Postby solar_dave » Thu Oct 23, 2014 11:12 pm

I worked in a place that machined BE, nasty stuff but easily controlled as compared to radio active materials. A good updraft over a machine with a hepa vacuum right at or near the cutting tool is all that is required. It is really light stuff.
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Re: 3D printing in Tungsten

Postby Doug Coulter » Fri Oct 24, 2014 3:23 pm

Dave, out of curiosity, were you working with relatively pure Be, or a dispersion strengthened alloy, whatever? I know it's quite dangerous to say, use a diamond saw to slice 1/4" rods of beryllia (not to mention very difficult, tried it, eats diamond saws and water lube). It basically wasn't worth the effort, discounting any risk.
I use Cu/Be a lot here for springs - some of them hold the inner window in my tank, those, I just soldered after a spot weld wasn't quite enough. Any flavor of copper is kinda hard to spot weld...I wasn't crazy enough to go for the TIG.

The rare metals handbook points out that it's one of the few that have actually killed quite a few people. Cd for example, though more poisonous, tends to make you so sick so fast...hardly anyone has ever been killed by it. If you ingest food that had gone through Cd plated hardware and had low Ph, you just throw up before you can absorb much of it. The only Cd death I'm aware of involved welding fumes - no way to throw up your lungs. We have some Be and I've handled it a little, even cutting sheets with scissors to make neutron generators with a polonium alpha source but it was quite dodgy work - the stuff is super brittle. It has a high "neato" factor in nuclear stuff, since a really thin piece is strong enough to hold off a vacuum, yet let even low energy charged particles or X rays go right through...

In yet another case of "I'm lucky to be alive" I had about half a pound of Cd catch on fire in a melt pot I was going to make an alloy in. Good thing I was upwind and outdoors. The resulting ash killed a poison ivy plant with a stem the size of my upper thigh and the tree it was growing on, so not a total waste - it was a good place to dump the stuff. The resulting alloy was a good thermal neutron stopper, but the capture gammas that resulted made me just put it on the shelf instead.

Be interested me for a couple reasons. Being so low in Z, most things go right through - they use it as windows on super-sensitive particle counters, or did, despite it's nearly impossible to braze, weld, glue...funny tempco, nothing wets it, and so on.
But it also takes part in some neutron-boosting reactions, the n,2n variety, as well as reacts with all the other species in a fusor - T, He3, D (all flavors and we have them all), H, you name it. Since it's low Z (really, low A) it's not as hard to overcome the Coloumb barrier as it is with other things. Further, when hit by electrons etc, it doesn't make X rays well at all, the K lines are so low-energy due to the low charge and the loose electrons. Like I said, possibly a lot of magic in a fusor - it would cut X ray production, increase neutrons, act as part of the fuel and so on. I found out the hard way why you don't put high Z coatings on the fusor wall - the X ray production goes WAY up. I had to tear it down and remove the Pd I tried for that reason. Ti might still be a viable wall coating with refinement. I think my last try put it on too thick, and we loaded it up too much. It changed form (TiHx) and wanted to flake off. As well as releasing all the D when it got hot, and we weren't and right now aren't that good at keeping the walls cold. Hard to do, stainless steel is practically speaking, a thermal insulator and we only get to fool with the outside. The possibility of storing "too much" D for decent gas pressure control didn't occur to me till it happened. Ti really soaks it up.

I didn't know anyone machined the stuff at all - my old books talk about arc-melting it (in argon) in cooled copper molds, the outer part of the Be never gets hot, so you get rough ingots, nothing can really hold molten Be like you can with say, steel.
In other words, most of the same fab problems you run into with tungsten - and for the same reasons. Obviously, someone made the 4 mil thick sheet we have a few sq inches of some way. It impressed me as having large brittle crystals, not well held together and was hard to cut without shattering. It looked ground rather than machined.

I'm still liking carbon (graphite in our case so far) for grid ends. It has so many good features. It's both thermally and electrically conductive, doesn't melt (sublimes somewhere above the MP of tungsten - we never go past red/orange heat, not a problem), radiates heat well - almost the only way to get rid of heat in our conditions, and is just soft enough so that for example, with my 20 mil holes and slightly elliptical 20 mil tungsten rods, you have to (but also, can) just force them in and they are then held tightly. Keeping a grid together is no mean feat FWIW - there are gram to ounce levels of repulsion at normal conditions, and under arcing, it's far worse. Many is the time I've had to take the system down and recover loose grid parts from all over the inside of the tank, after giving them quite the torture test before putting them in there. I suppose tempcos matter too. Carbon has one of the lower secondary electron emission numbers of any conductor as well - at least measured the way they did back in the electron tube days with medium voltages and electrons as the projectiles. I can't seem to find any study of the elements on secondary emission from being hit with fast D (or whatever) at all, and it would be very useful to know how things act at our conditions. We need some, but not very many, electrons. I'm pretty sure we don't need many more than we have "free" from ionizing the D in the first place.

I'm even wondering about tungsten carbide we can now get that's supposed to be super round. Will that trick still work? It's going to be a lot of tooling up to use it, expensive. I might have to try and grind threads on one end or something.
It appears the .009" drills don't come in the usual solid carbide with 1/8" shanks, so I have to make a 1mm collet for my drill rig, for example, no small task that needs its own special tools (I made the 1/8" one I have as well, I managed but it was a lotta work). The collets etc I see in places like McMaster may as well not apply - too big, too complex, too expensive, too much inertial mass for these tiny drills...And I kind of doubt I can just drill a 1mm hole in the end of a rod and use setscrews to get the required accuracy...I'll have to actually make a collet (the tiny drills are 1mm shank). We're interested in the WC because if I read the old books right - it has lower electron emission, and this stuff is both tinier than anything else we can find, and very round and stiff - just what we want, I believe.

The one bad thing about carbon is that you can wind up with hydrocarbons if you smash hydrogen into it. We saw some simple ones when our mass spec was in working order, not many but some. It also sputters a little bit. But with our new BN high voltage feedthrough, cleanup of sputtered anything is now a walk in the park - one wipe with 320 grid sandpaper and all is new again. At any rate, what usually happens to any simple hydrocarbons in the tank is that they find their way to something incandescently hot and simply decompose again there, releasing the D and depositing the carbon. That's not all bad, and is probably responsible for the improvement with running of some of our grids - they get a little coating of C and don't emit electrons as well as a result, and do radiate heat better too.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: 3D printing in Tungsten

Postby solar_dave » Sat Oct 25, 2014 6:23 am

Doug I too have machined the BeCu variants used as masks in ion beam coating process but pure Be ingots (12 to 18 inches in diameter) were also machined to create asperical components for certain devices in our end product. While I am not completely sure of the physics, I suspect they were used to enhance and focus the neutrons created by these devices. I think I am getting close to the edge here so I will stop.

There is a facility in Sarasota FL that regularly machines BE to high tolerances, American Beryllium. I serviced and certified CNC measuring equipment in that facility which we provide to them. They used bag dust collectors on the vent hoods. Here is an link to an EPA evaluation of that facility back in 1971:
http://nepis.epa.gov/Exe/ZyNET.exe/9100 ... &File=D%3A\ZYFILES\INDEX%20DATA\70THRU75\TXT\00000009\9100CTI6.txt&User=ANONYMOUS&Password=anonymous&SortMethod=h|-&MaximumDocuments=1&FuzzyDegree=0&ImageQuality=r75g8/r75g8/x150y150g16/i425&Display=p|f&DefSeekPage=x&SearchBack=ZyActionL&Back=ZyActionS&BackDesc=Results%20page&MaximumPages=1&ZyEntry=1

That link shows them turning, milling, drilling, Electric Discharge machining and grinding the stuff. All were done dry except grinding. They used typical bag type dust collectors. I suspect these days that might be insufficient and glove box type containment with wet scrubbers may be required. The effects of inhalation can be quite devastating: http://en.wikipedia.org/wiki/Beryllium_poisoning

Thin cross sections tended to be pretty poor structurally as the material is really brittle.

A person sensitive to Be could tell the machining was taking place by tasting the metallic Be in the air. I can attest to this personally. I saw them literally sweeping the chips up off the floor in that Sarasota facility.

Here is a reference to the facility I worked at for over 15 years:
http://en.wikipedia.org/wiki/Rocky_Flats_Plant
http://upload.wikimedia.org/wikipedia/c ... leanup.jpg

You may want to remove the links as the bots might pick it up and bring many unwanted people here.
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Re: 3D printing in Tungsten

Postby Doug Coulter » Sat Oct 25, 2014 8:01 pm

Well, I do know what the Be was for in that case. They are already not responding to your longer link, and the rest is public anyway. Considering the other bad stuff they let get away, I'd think they thought Be was relatively harmless...the DOE sure has made some hard to clean up messes in the name of "our safety", haven't they?

In my case, most of the coolness of the Be would be in coating my tank walls with a thin layer (They get hit hard with D- from charge-exchange and other causes). That's a job for sputtering, given the super high melt point of Be - and something I can do here with more or less complete safety (my vacuum system even vents to the outdoors). This and a few other "probably factor of 2-3" things I am keeping in my "back pocket" if they turn out to be the difference - first we are going after the factors of 10's and 100's. If we then just need a little more...well, I've got a few like this, just in case.

Richard Hull's idea of putting D in the tank walls was a good one. His reasoning was wrong, but the answer was right - I proved it here. Credit where due. Ti works well for that if you don't go overboard, and like Be, is light and doesn't help make more X rays. A mix might turn out to be the ideal thing...Someone's just going to have to give it a try.

Right now, there are a couple of peaks on our Q charts we've only seen an upslope on - we need to see the other side of those to even confirm it ever goes back down with increasing this or decreasing that. That's first, the rest...will be a slog that won't be worth doing if we don't get the obvious stuff first. We are seeing Q (here meaning fusion power/input power) go up exponentially with drive voltage, and as the inverse exponent of grid focus accuracy - the tinier the errors, the more fusion for the same power. Those curves are so steep it's easy to believe that finding those limits alone gets us there, but we can't know of course till we see the other side of either one....

Rules for troubleshooting -
try the easy stuff first
divide and conquer - find out which subsystem is the cause
repeat till it works

We're still on step one here. The big difference and advantage we have is great data acquisition, so that things that used to have to be honestly reported as "odd outliers" we now know are real, and under what conditions they happen, so we can replicate them at will. Not even new science per se. Just the usual technological advancement.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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