#homecmos IRC log for Sunday, 2012-03-04

--- Sun Mar 4 201200:00
fennazonenberg: 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 concentric13:22
fenna single set screw will allow it to wobble13:23
azonenbergfenn: Hmm19:44
azonenbergGood idea19:44
azonenbergi'm not a mechanical engineer lol19:44
Syncat 90° it will still be unbalanced fenn21:05
Synceither 3 at 120° or 2 at 180°, or a balanced wheel21:06
azonenbergSync: 2 at 180 would work21:13
azonenbergi havent had time to do any more design on it in the last few days... silly lab reports for *school* :P21:14
Syncwhat is the speed on that thing?21:15
azonenbergSync: The max speed is still up in the air as i havent picked out a motor or gear train / belt assembly yet21:16
azonenbergbut i'm expecting 5-10k RPM would be a reasonable max21:16
azonenbergbut it has to be stable and controllable down to zero21:16
Syncew, use a collet then, everything else will get ugly for you21:17
azonenbergSync: i need to attach the shaft to the head somehow21:21
azonenbergthats intended to be a one-piece assembly21:21
azonenbergi might use a collet for connecting the shaft+head assembly to a chuck of some sort21:21
Syncwell, you could make that exchangable, or you just turn it from solid21:21
azonenbergthis is the "bit"21:21
azonenbergTurn it from solid21:21
azonenbergDo you have any idea what that would cost21:21
Syncunder 50 bux21:22
azonenberg4 inch x 2 inch 316 stainless bar21:22
Syncwhy stainless o.021:22
Syncbut yeah even then21:22
azonenbergthere's going to be solvents and corrosives all over the place21:22
azonenbergi want something that wont be hurt by it21:22
azonenbergor rust and contaminate my specimens with particles21:22
SyncAl should be pretty good at that21:22
azonenbergI was thinking that but its soft21:23
Syncget 606121:23
azonenbergand i dont want to use it for shafts21:23
Syncwhy not?21:23
azonenbergmy plan was to use aluminum for the bulk of the tool21:23
azonenbergand steel where strength was important21:24
azonenbergi will freely admit i'm not a mechanical engineer21:24
azonenbergno anywhere close to one :p21:24
azonenbergSo, if you think i should make it out of a single piece\21:25
Syncif you turn it from a single piece of aluminium you will not have balancing issues21:25
azonenbergThe first thing to do would be to check if the chucks on the lathe at my school can handle 4" bar stock21:25
azonenbergwe usually work on much smaller21:25
azonenberglike 1-221:25
azonenbergthey're full sized engine lathes but they may not have chucks in stock that open that far21:25
azonenberg4" rod*21:25
azonenbergsince all the student projects use 1"21:26
Syncthey should have something large enough21:26
azonenbergHmm *fires up inventor and starts tweaking*21:27
azonenbergSo lets see, 6 inch 6061 aluminum bar stock21:28
azonenbergor 3 inch21:28
azonenberg3 should work fine21:28
azonenbergby 4 inch diameter21:29
Synccheck ebay21:29
fennno, the goal is to make them off axis, 180 would be pointless21:29
azonenbergfenn: better idea, machine it out of a single piece of metal21:29
azonenbergno setscrews needed21:29
fenneh, that's a lot of metal21:29
fennbrazing should work21:29
Syncyes that is another idea21:30
azonenbergWell, my school's shop does have TiG, MiG, and oxyacetylene brazing capabilities21:30
azonenbergI dont know how to TiG but i sort of know how to MiG21:30
azonenbergand oxyacetylene is just like pipe soldering but a bit hotter :p21:30
Synctig welding is easy21:31
azonenbergSync: i didnt say it was hardf21:31
azonenbergbut i dont want to practice on a $70 stainless steel bar :p21:31
fennput it in a furnace for a while and then poke silver solder at the joint while red hot21:31
fennor brazing compound21:32
azonenbergfenn: if i was going to braze i'd use acetylene21:32
azonenbergwe have the facilities for that in the welding shop21:32
azonenbergbut, as fun as designing this thing right now is21:32
azonenbergi have three lab reports to do this weekend lol21:33
SyncI should see what I can whip up next week, building something like that should be pretty straigth forward21:33
azonenbergSync: well thats just the chuck21:34
azonenbergi have to design the body, choose a suitable motor21:34
azonenberga gear or belt system suitable for spinning it21:34
azonenberga spatter guard21:34
azonenbergnothing particularly hard, at least for someone with more mechanical design experience than me21:34
azonenbergBut still has to be done21:34
Syncmmh, the drive would be interesting, a flat belt would be the easiest, they support very high speeds without issues21:37
azonenbergThat was my thinking21:37
Syncprotip: put grooves in the rollers and make them thicker in the middle21:38
Syncthis will cause automatic tracking and prevents slipping at high speeds21:38
azonenbergI was thinking some kind of a grooved belt, yes21:38
azonenbergMy biggest question right now is bearings21:38
azonenbergThe moving assembly will consist of the top chuck (4" flat disk to mount the wafer/sample on)21:40
azonenbergthe shaft21:40
azonenbergand some kind of pulley/roller to attach to the belt21:40
azonenbergbut then i have to attach that to the stationary base somehow21:40
azonenbergand i've never had to design anything with bearings in it lol21:40
azonenbergi'm a computer scientist who dabbles in EE, not a mechanical engineer21:40
Syncthe bearings are the least problem here21:40
azonenbergThey're the thing i know the least about lol21:41
Syncat 10k rpm most sealed bearings will do21:41
azonenbergI wouldnt know a sealed bearing if it bit me on the nose lol21:42
azonenberghow do you attach to it?21:42
berndji missed the start; what are you building?21:42
azonenbergis it a solid housing and a rotor inside that you setscrew your shaft into?21:42
azonenbergor what21:42
azonenbergberndj: discussing spin coater design21:43
azonenbergi'm tired of the one i have now made from 2x4s and a power drill21:43
azonenbergi want something proper made from scratch with a real speed controller etc21:43
berndjheh. nasa spent a billion dollars making a pen that would work in space. the russians used a pencil.21:43
berndj2x4 and drill is good for DIYism though21:44
azonenbergberndj: yes21:44
azonenbergbut i have a real need to replace it21:44
azonenbergfirst off, total lack of precise speed control21:44
azonenbergSecond, worse21:44
azonenbergit's too big21:44
azonenbergi cant use it in my fume hood, it blocks the airflow21:44
azonenbergand i dont want solvent fumes all over the living room21:44
berndjfair enough21:44
azonenbergso i have a pressing need for a coater that has controllable speed and is signficnatly smaller height-wise than the current >12" high monster21:44
azonenbergAnd i figure it'd be a good exercise in mechanical design21:45
berndjoh it's that big21:45
berndjof course it's that big, it's at least as big as a drill!21:45
azonenbergactually the drill is on a flexible extension cable21:45
azonenbergbut yeah, its about 8" x 12" square21:46
azonenbergand maybe 18" high21:46
azonenbergso in a 24" cube fume hood, well21:46
azonenbergthe air currents arent what they should be21:46
Syncazonenberg: 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 balanced21:46
Syncif you put a centered screw in there you may get away without balancing21:47
azonenbergok, i'll take a look at these things, they look like they'll do21:48
Syncthey will21:48
azonenbergi was thinking double sealed21:48
azonenbergsince stuff will be spattering all over the place21:48
Syncyou can reduce exposure by using a small circular baffle under the disc21:50
azonenbergwell, i dont expect too much21:50
azonenbergbecause the chuck is 4" diameter21:50
azonenbergand will act as a shield21:50
azonenbergall the spatter is outward21:50
Syncbut those bearings are dirt cheap21:50
azonenbergi'll then have some like 1/8" sheet metal or something sitting around the outside of the tray21:50
azonenbergto catch spatter21:50
azonenbergwhich will, in use, be lined with texwipes etc21:50
azonenbergAny estimates on what i can expect to pay for the entire tool components wise?21:51
azonenbergi was thinking in the $200 range21:51
azonenbergcounting the motors and belts21:51
azonenbergand electronics for the controller21:51
Syncno way, if you get the motor new and a VFD21:52
azonenbergi was thinking brushless DC from an RC aircraft store21:52
azonenbergcheap speed controller21:53
azonenbergthen build my own feedback circuit around that21:53
azonenbergbrushless 3-phase*21:53
azonenbergmy back-of-the-envelope budget was $100-150 in mechancial stock and $50-100 in electronics21:53
azonenbergtoo high? too low?21:53
Syncwell if you can do everything mechanical in the shop that should pan out21:54
Syncif not, put a zero on it21:54
azonenbergFor 2K i can buy one premade lol21:54
azonenbergI'm doign all the labor myself21:55
azonenbergand i intend to choose manufacturing processes i can do in the shop21:55
azonenbergso no tooling or labor expenses, just materials21:55
azonenbergi could prob afford to drop up to 500 on the project, maybe a bit more21:55
azonenbergJust trying to get a budgetary number21:55
Syncyeah expect around 300-400 that is realistic21:59
azonenbergSounds reasonable... the main thing i care is that it gets the job done and costs less than a commercially made one22:00
azonenbergif it fails in either respect i'm better off buying one22:00
azonenbergWhenever i make a tool i ask myself those two things22:00
azonenbergfor example i cannot make a drill cheaper and better than one you buy at the home depot22:00
azonenbergso i buy one22:00
didjai'll try asking here too since it seems relevant to nanostuff22:01
didjacan you generate radio waves by mechanically oscillating a piece of metal very quickly?22:01
azonenbergnot unless there's a magnetic field involved afaik22:01
azonenbergyou should be able to generate light by running 10THz range electricity through a suitable antenna though, in theory :p22:02
Synclet me see what I can dish out in cad real quick azonenberg22:03
berndjdidja, like a quartz crystal?22:04
berndjnot metal, but that isn't too relevant22:04
Syncazonenberg: done22:18
azonenbergSync: sorry, dropped offline for a bit (stupid wifi card)22:31
azonenbergwhat did i miss22:31
didjaazonenberg: all you need is a changing E field right?22:36
didjabecause then nanoscale mechanical oscillators make a lot more sense22:36
didjai'm again brushing up on EM22:36
Synchttp://sync-hv.de/~tmp/coater.bmp I dished out that for you azonenberg22:37
Syncthis is basically what you need22:37
azonenbergSync: nice22:45
azonenbergi'll try something like that and post stuff here when i get achance22:46
--- Mon Mar 5 201200:00

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