<fenn>
azonenberg: re spin coater chuck, you want to have two set screws at 90 or 120 degrees, although a collet is preferred because it's more concentric
<fenn>
a single set screw will allow it to wobble
<azonenberg>
fenn: Hmm
<azonenberg>
Good idea
<azonenberg>
i'm not a mechanical engineer lol
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<Sync>
at 90° it will still be unbalanced fenn
<Sync>
either 3 at 120° or 2 at 180°, or a balanced wheel
<azonenberg>
Sync: 2 at 180 would work
<azonenberg>
i havent had time to do any more design on it in the last few days... silly lab reports for *school* :P
<Sync>
what is the speed on that thing?
<azonenberg>
Sync: The max speed is still up in the air as i havent picked out a motor or gear train / belt assembly yet
<azonenberg>
but i'm expecting 5-10k RPM would be a reasonable max
<azonenberg>
but it has to be stable and controllable down to zero
<Sync>
ew, use a collet then, everything else will get ugly for you
<azonenberg>
Sync: i need to attach the shaft to the head somehow
<azonenberg>
thats intended to be a one-piece assembly
<azonenberg>
i might use a collet for connecting the shaft+head assembly to a chuck of some sort
<Sync>
well, you could make that exchangable, or you just turn it from solid
<azonenberg>
this is the "bit"
<azonenberg>
Turn it from solid
<azonenberg>
Do you have any idea what that would cost
<Sync>
under 50 bux
<azonenberg>
4 inch x 2 inch 316 stainless bar
<Sync>
why stainless o.0
<Sync>
but yeah even then
<azonenberg>
there's going to be solvents and corrosives all over the place
<azonenberg>
i want something that wont be hurt by it
<azonenberg>
or rust and contaminate my specimens with particles
<Sync>
Al should be pretty good at that
<azonenberg>
I was thinking that but its soft
<Sync>
get 6061
<azonenberg>
and i dont want to use it for shafts
<Sync>
why not?
<azonenberg>
my plan was to use aluminum for the bulk of the tool
<azonenberg>
and steel where strength was important
<azonenberg>
i will freely admit i'm not a mechanical engineer
<azonenberg>
no anywhere close to one :p
<azonenberg>
nor*
<azonenberg>
So, if you think i should make it out of a single piece\
<Sync>
if you turn it from a single piece of aluminium you will not have balancing issues
<azonenberg>
The first thing to do would be to check if the chucks on the lathe at my school can handle 4" bar stock
<azonenberg>
we usually work on much smaller
<azonenberg>
like 1-2
<azonenberg>
they're full sized engine lathes but they may not have chucks in stock that open that far
<azonenberg>
4" rod*
<azonenberg>
since all the student projects use 1"
<Sync>
they should have something large enough
<azonenberg>
Hmm *fires up inventor and starts tweaking*
<azonenberg>
So lets see, 6 inch 6061 aluminum bar stock
<azonenberg>
or 3 inch
<azonenberg>
3 should work fine
<azonenberg>
by 4 inch diameter
<Sync>
check ebay
<fenn>
no, the goal is to make them off axis, 180 would be pointless
<azonenberg>
fenn: better idea, machine it out of a single piece of metal
<azonenberg>
no setscrews needed
<fenn>
eh, that's a lot of metal
<fenn>
brazing should work
<azonenberg>
Hmm
<Sync>
yes that is another idea
<azonenberg>
Well, my school's shop does have TiG, MiG, and oxyacetylene brazing capabilities
<azonenberg>
I dont know how to TiG but i sort of know how to MiG
<azonenberg>
and oxyacetylene is just like pipe soldering but a bit hotter :p
<Sync>
tig welding is easy
<azonenberg>
Sync: i didnt say it was hardf
<azonenberg>
but i dont want to practice on a $70 stainless steel bar :p
<fenn>
put it in a furnace for a while and then poke silver solder at the joint while red hot
<fenn>
or brazing compound
<azonenberg>
fenn: if i was going to braze i'd use acetylene
<fenn>
ok
<azonenberg>
we have the facilities for that in the welding shop
<azonenberg>
but, as fun as designing this thing right now is
<azonenberg>
i have three lab reports to do this weekend lol
<Sync>
I should see what I can whip up next week, building something like that should be pretty straigth forward
<azonenberg>
Sync: well thats just the chuck
<azonenberg>
i have to design the body, choose a suitable motor
<azonenberg>
a gear or belt system suitable for spinning it
<azonenberg>
a spatter guard
<azonenberg>
nothing particularly hard, at least for someone with more mechanical design experience than me
<azonenberg>
But still has to be done
<Sync>
mmh, the drive would be interesting, a flat belt would be the easiest, they support very high speeds without issues
<azonenberg>
That was my thinking
<Sync>
protip: put grooves in the rollers and make them thicker in the middle
<Sync>
this will cause automatic tracking and prevents slipping at high speeds
<azonenberg>
I was thinking some kind of a grooved belt, yes
<azonenberg>
My biggest question right now is bearings
<azonenberg>
The moving assembly will consist of the top chuck (4" flat disk to mount the wafer/sample on)
<azonenberg>
the shaft
<azonenberg>
and some kind of pulley/roller to attach to the belt
<azonenberg>
but then i have to attach that to the stationary base somehow
<azonenberg>
and i've never had to design anything with bearings in it lol
<azonenberg>
i'm a computer scientist who dabbles in EE, not a mechanical engineer
<Sync>
the bearings are the least problem here
<azonenberg>
They're the thing i know the least about lol
<Sync>
at 10k rpm most sealed bearings will do
<azonenberg>
I wouldnt know a sealed bearing if it bit me on the nose lol
<azonenberg>
how do you attach to it?
<berndj>
i missed the start; what are you building?
<azonenberg>
is it a solid housing and a rotor inside that you setscrew your shaft into?
<azonenberg>
i'm tired of the one i have now made from 2x4s and a power drill
<azonenberg>
i want something proper made from scratch with a real speed controller etc
<berndj>
heh. nasa spent a billion dollars making a pen that would work in space. the russians used a pencil.
<berndj>
2x4 and drill is good for DIYism though
<azonenberg>
berndj: yes
<azonenberg>
but i have a real need to replace it
<azonenberg>
first off, total lack of precise speed control
<azonenberg>
Second, worse
<azonenberg>
it's too big
<azonenberg>
i cant use it in my fume hood, it blocks the airflow
<azonenberg>
and i dont want solvent fumes all over the living room
<berndj>
fair enough
<azonenberg>
so i have a pressing need for a coater that has controllable speed and is signficnatly smaller height-wise than the current >12" high monster
<azonenberg>
And i figure it'd be a good exercise in mechanical design
<berndj>
oh it's that big
<berndj>
of course it's that big, it's at least as big as a drill!
<azonenberg>
actually the drill is on a flexible extension cable
<azonenberg>
but yeah, its about 8" x 12" square
<azonenberg>
and maybe 18" high
<azonenberg>
so in a 24" cube fume hood, well
<azonenberg>
the air currents arent what they should be
<Sync>
azonenberg: two 6205-2Z bearings, lip to run against on the shaft and a circlip on the bottom, maybe a nut but then it needs to be balanced
<Sync>
if you put a centered screw in there you may get away without balancing
<azonenberg>
ok, i'll take a look at these things, they look like they'll do
<Sync>
they will
<azonenberg>
i was thinking double sealed
<azonenberg>
since stuff will be spattering all over the place
<Sync>
you can reduce exposure by using a small circular baffle under the disc
<azonenberg>
well, i dont expect too much
<azonenberg>
because the chuck is 4" diameter
<azonenberg>
and will act as a shield
<azonenberg>
all the spatter is outward
<Sync>
but those bearings are dirt cheap
<azonenberg>
i'll then have some like 1/8" sheet metal or something sitting around the outside of the tray
<azonenberg>
to catch spatter
<azonenberg>
which will, in use, be lined with texwipes etc
<azonenberg>
Any estimates on what i can expect to pay for the entire tool components wise?
<azonenberg>
i was thinking in the $200 range
<azonenberg>
counting the motors and belts
<azonenberg>
motor*
<azonenberg>
and electronics for the controller
<Sync>
no way, if you get the motor new and a VFD
<azonenberg>
i was thinking brushless DC from an RC aircraft store
<azonenberg>
cheap speed controller
<azonenberg>
then build my own feedback circuit around that
<azonenberg>
brushless 3-phase*
<azonenberg>
my back-of-the-envelope budget was $100-150 in mechancial stock and $50-100 in electronics
<azonenberg>
too high? too low?
<Sync>
well if you can do everything mechanical in the shop that should pan out
<Sync>
if not, put a zero on it
<azonenberg>
For 2K i can buy one premade lol
<azonenberg>
I'm doign all the labor myself
<azonenberg>
and i intend to choose manufacturing processes i can do in the shop
<azonenberg>
so no tooling or labor expenses, just materials
<azonenberg>
i could prob afford to drop up to 500 on the project, maybe a bit more
<azonenberg>
Just trying to get a budgetary number
<Sync>
yeah expect around 300-400 that is realistic
<azonenberg>
Sounds reasonable... the main thing i care is that it gets the job done and costs less than a commercially made one
<azonenberg>
if it fails in either respect i'm better off buying one
<azonenberg>
Whenever i make a tool i ask myself those two things
<azonenberg>
for example i cannot make a drill cheaper and better than one you buy at the home depot
<azonenberg>
so i buy one
<didja>
i'll try asking here too since it seems relevant to nanostuff
<didja>
can you generate radio waves by mechanically oscillating a piece of metal very quickly?
<azonenberg>
not unless there's a magnetic field involved afaik
<azonenberg>
you should be able to generate light by running 10THz range electricity through a suitable antenna though, in theory :p
<Sync>
let me see what I can dish out in cad real quick azonenberg
<berndj>
didja, like a quartz crystal?
<berndj>
not metal, but that isn't too relevant
<Sync>
azonenberg: done
<Sync>
!
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<azonenberg>
Sync: sorry, dropped offline for a bit (stupid wifi card)
<azonenberg>
what did i miss
<didja>
azonenberg: all you need is a changing E field right?
<didja>
because then nanoscale mechanical oscillators make a lot more sense