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<_Sync_>
whitequark: did you read housekeepers work on ceramic to metal seals and the like=?
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<_Sync_>
he has a few books on that
<whitequark>
mm i see
<whitequark>
I am not sure I see how it would be easier though, kovar seals are like $40 each and they are fairly nontrivial to make yourself
<_Sync_>
well he also talks in depth about all kinds of glass or ceramic work
<_Sync_>
in the end the key to make good ceramic/metal seals is a hydrogen furnance
<whitequark>
mm yes i should read that book
<whitequark>
hydrogen is... annoying to work with
<_Sync_>
not really, if you have a proper oven it is not really all that dangerous to work with
<whitequark>
I mean more like having a cylinder of it
<_Sync_>
just making a safe oven is annoying
<_Sync_>
why?
<whitequark>
if it leaks, it can get rather nasty
<whitequark>
hot invisible flame, not to mention the enormous explosive mixture range
<_Sync_>
sure, but why would it leak
<_Sync_>
modern gas bottles are very safe
<_Sync_>
not sure how modern they are in russia tho ;)
<whitequark>
it depends but i believe they're on the order of ones used in EU
<whitequark>
unless you buy really old shit
<whitequark>
i guess i could just synthesize it on spot, in the tiny quantities needed for the vacuum oven
<_Sync_>
the quantities are not all that small
<_Sync_>
you need to purge through the entire heat cycle
<_Sync_>
with rates of maybe 5-20l/min
<whitequark>
hm i see
<_Sync_>
and fairly high purities
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<SpeedEvil>
I wondered a while back about InGa with nanoscopic ferrite particles in, as vacuum-tight constrainable by magnetic field 'zero' leak moving seals
<SpeedEvil>
^ferrofluid
<whitequark>
aren't ferrofluid passthroughs a thing?
<whitequark>
like, already
<SpeedEvil>
yes
<_Sync_>
yup
<_Sync_>
they are actually pretty spendy :X
<SpeedEvil>
Exactly
<SpeedEvil>
It's a pity printable magnetics suck a bit.
<SpeedEvil>
But at least magnetic steel is easy to machine
<whitequark>
is there printable anything that doesn't suck?
<whitequark>
PLA sucks. SLA is... okay-ish quality, slow, and the resin puts printer ink to shame. printing brass or steel results in something disgustingly porous
<whitequark>
selective electron beam sintering in vacuum seems to be okay, but incredibly expensive
<SpeedEvil>
whitequark: Inconel
<SpeedEvil>
and yeah - I've been wondering on that too
<SpeedEvil>
A ~2A or so electron gun doesn't seem _horribly_ complex.
<whitequark>
you need a turbo pump
<whitequark>
well, at EHSM there was a guy from Warsaw's ITR which did it in a sort of roundabout way
<whitequark>
he used the residual gas to do /ion/ beam sintering
<whitequark>
so it worked with only a rotary vane pump
<SpeedEvil>
sublimation pumps can get down to quite reasonably low pressures in some cases.
<SpeedEvil>
If you can get on top of leakage and your print media doesn't outgas under load
<SpeedEvil>
^heat
<whitequark>
hrm
<whitequark>
print media very certainly does, by virtue of being a fine powder with a shit ton of surface area
<whitequark>
don't forget you need to add print media too...
<SpeedEvil>
I don't know how much gas inconel or SS or ... beads will sorb
<whitequark>
'beads' ?
<SpeedEvil>
for sintering
<whitequark>
well.
<whitequark>
let's say 1 thou resolution
<whitequark>
so 0.3 thou particle size
<SpeedEvil>
I'm not sure you can do that
<whitequark>
why not?
<whitequark>
you can focus the beam pretty well
<SpeedEvil>
Well, for one thing, 1 thou layers is going to take for fucking ever.
<whitequark>
layers would be thicker.
<SpeedEvil>
yes, but they can't be that much thicker
<whitequark>
you can actually adjust resolution pretty easily
<SpeedEvil>
Also, 'conduction' through radiation is quite efficient at thosse scales.
<whitequark>
since beam power and spot size are both trivially controlled
<_Sync_>
SpeedEvil: you will need some kind of active pump
<SpeedEvil>
As particle size drops, square/cube means that it is a much more efficient radiator
<_Sync_>
sorption pumps have very bad absolute capacities
<_Sync_>
and turbos are cheap
<whitequark>
"cheap"
<_Sync_>
they really are
<whitequark>
not if you're trying to mass-produce 3D printers
<_Sync_>
did not pay more than 150€ for any of mine
<SpeedEvil>
_Sync_: yes - I don't have a good handle on gas loads from the media. And capacity varies by gas. Backstreaming through the pump is a concern that I was wondering about addressing the very silly way of enclosing the oil pump and putting it in a nitrogen box.
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<whitequark>
_Sync_: they were used.
<SpeedEvil>
But that's likely overkill.
<SpeedEvil>
And that too
<_Sync_>
sure, but there is not much to go wrong besides the bearings
<_Sync_>
and even new
<whitequark>
the secondary market will not support anything in batches
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<_Sync_>
a 150l/s pump runs you around 4k new
<whitequark>
yeah
<_Sync_>
that's pretty cheap after all
<_Sync_>
SpeedEvil: use a dry scroll then
<whitequark>
it's not a mass market device even for a vrey conservative notion of "mass"
<_Sync_>
but metal powders have a LOT of trapped gas
<_Sync_>
because they have a high surface area
<SpeedEvil>
_Sync_: I have a nice edwards double stage oil.
<whitequark>
and if not, I mean, those metal sintering in vacuum printers are already made and sold
<_Sync_>
thus they have a lot of OH groups on the wurface
<whitequark>
SpeedEvil: not enough for EB I believe
<SpeedEvil>
_Sync_: I know - but I don't know if they do once you heat it red hot for an hour
<_Sync_>
well, after outgassing they get better
<_Sync_>
but everytime you vent you have to bake again
<_Sync_>
I switched all my pumping systems over to dryscroll/turbo
<SpeedEvil>
Unless you keep your media under vacuum or dry gas, which isn't quite prohibitive.
<_Sync_>
because I don't want to deal with the oil vapors anymore
<whitequark>
SpeedEvil: argon will still be trapped on the surface
<SpeedEvil>
^Above opinions were formed when I was investigating relatively high presure uses like making mirrors. I don't have a good handle on UHV
<whitequark>
at least a monolayer
<SpeedEvil>
whitequark: I was assuming you could pick an easily bakeable gas - I don't off-hand know what it'd be
<whitequark>
if you have something like 1m^3/g
<whitequark>
er
<_Sync_>
argon is not too bad
<whitequark>
m^2
<whitequark>
so like 8m^2/ml
<whitequark>
that is going to be a lot
<whitequark>
also argon will not be sequestered by sublimation pumps or sth, you need a kinetic one
<_Sync_>
well, sublimators will still pump noble gasses
<_Sync_>
although they like reactive ones better
<SpeedEvil>
whitequark: yes, which is why I said N2 initially
<SpeedEvil>
^thought
<SpeedEvil>
Speed kind-of-sucks quite badly with nobles.
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<whitequark>
N2 will form nitrides though
<whitequark>
rather well at that
<whitequark>
which will make your finished piece extremely brittle
<SpeedEvil>
I was assuming it would bake out
<SpeedEvil>
I've not actually researched this properlym and would ned to do so before seriously...
<whitequark>
bakeout could work
<whitequark>
however apparently you do not need a lot of N2 to get a shitty crystal
<whitequark>
like there's a reason tig welding requires pretty pure argon
<SpeedEvil>
I would say hydrogen - but... :)
<whitequark>
uh
<whitequark>
hydrogen embrittlement is also a thing
<SpeedEvil>
yeah
<SpeedEvil>
hence the ...
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<whitequark>
huh, before 1952, it was not understood that metal-ceramic seal is not merely mechanical