--- Sun Mar 4 2012 | 00:00 | |
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 | 13:22 |
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fenn | a single set screw will allow it to wobble | 13:23 |
azonenberg | fenn: Hmm | 19:44 |
azonenberg | Good idea | 19:44 |
azonenberg | i'm not a mechanical engineer lol | 19:44 |
Sync | at 90° it will still be unbalanced fenn | 21:05 |
Sync | either 3 at 120° or 2 at 180°, or a balanced wheel | 21:06 |
azonenberg | Sync: 2 at 180 would work | 21:13 |
azonenberg | i havent had time to do any more design on it in the last few days... silly lab reports for *school* :P | 21:14 |
Sync | what is the speed on that thing? | 21:15 |
azonenberg | Sync: The max speed is still up in the air as i havent picked out a motor or gear train / belt assembly yet | 21:16 |
azonenberg | but i'm expecting 5-10k RPM would be a reasonable max | 21:16 |
azonenberg | but it has to be stable and controllable down to zero | 21:16 |
Sync | ew, use a collet then, everything else will get ugly for you | 21:17 |
azonenberg | Sync: i need to attach the shaft to the head somehow | 21:21 |
azonenberg | thats intended to be a one-piece assembly | 21:21 |
azonenberg | i might use a collet for connecting the shaft+head assembly to a chuck of some sort | 21:21 |
Sync | well, you could make that exchangable, or you just turn it from solid | 21:21 |
azonenberg | this is the "bit" | 21:21 |
azonenberg | Turn it from solid | 21:21 |
azonenberg | Do you have any idea what that would cost | 21:21 |
Sync | under 50 bux | 21:22 |
azonenberg | 4 inch x 2 inch 316 stainless bar | 21:22 |
Sync | why stainless o.0 | 21:22 |
Sync | but yeah even then | 21:22 |
azonenberg | there's going to be solvents and corrosives all over the place | 21:22 |
azonenberg | i want something that wont be hurt by it | 21:22 |
azonenberg | or rust and contaminate my specimens with particles | 21:22 |
Sync | Al should be pretty good at that | 21:22 |
azonenberg | I was thinking that but its soft | 21:23 |
Sync | get 6061 | 21:23 |
azonenberg | and i dont want to use it for shafts | 21:23 |
Sync | why not? | 21:23 |
azonenberg | my plan was to use aluminum for the bulk of the tool | 21:23 |
azonenberg | and steel where strength was important | 21:24 |
azonenberg | i will freely admit i'm not a mechanical engineer | 21:24 |
azonenberg | no anywhere close to one :p | 21:24 |
azonenberg | nor* | 21:24 |
azonenberg | So, if you think i should make it out of a single piece\ | 21:25 |
Sync | if you turn it from a single piece of aluminium you will not have balancing issues | 21:25 |
azonenberg | The first thing to do would be to check if the chucks on the lathe at my school can handle 4" bar stock | 21:25 |
azonenberg | we usually work on much smaller | 21:25 |
azonenberg | like 1-2 | 21:25 |
azonenberg | they're full sized engine lathes but they may not have chucks in stock that open that far | 21:25 |
azonenberg | 4" rod* | 21:25 |
azonenberg | since all the student projects use 1" | 21:26 |
Sync | they should have something large enough | 21:26 |
azonenberg | Hmm *fires up inventor and starts tweaking* | 21:27 |
azonenberg | So lets see, 6 inch 6061 aluminum bar stock | 21:28 |
azonenberg | or 3 inch | 21:28 |
azonenberg | 3 should work fine | 21:28 |
azonenberg | by 4 inch diameter | 21:29 |
Sync | check ebay | 21:29 |
fenn | no, the goal is to make them off axis, 180 would be pointless | 21:29 |
azonenberg | fenn: better idea, machine it out of a single piece of metal | 21:29 |
azonenberg | no setscrews needed | 21:29 |
fenn | eh, that's a lot of metal | 21:29 |
fenn | brazing should work | 21:29 |
azonenberg | Hmm | 21:30 |
Sync | yes that is another idea | 21:30 |
azonenberg | Well, my school's shop does have TiG, MiG, and oxyacetylene brazing capabilities | 21:30 |
azonenberg | I dont know how to TiG but i sort of know how to MiG | 21:30 |
azonenberg | and oxyacetylene is just like pipe soldering but a bit hotter :p | 21:30 |
Sync | tig welding is easy | 21:31 |
azonenberg | Sync: i didnt say it was hardf | 21:31 |
azonenberg | but i dont want to practice on a $70 stainless steel bar :p | 21:31 |
fenn | put it in a furnace for a while and then poke silver solder at the joint while red hot | 21:31 |
fenn | or brazing compound | 21:32 |
azonenberg | fenn: if i was going to braze i'd use acetylene | 21:32 |
fenn | ok | 21:32 |
azonenberg | we have the facilities for that in the welding shop | 21:32 |
azonenberg | but, as fun as designing this thing right now is | 21:32 |
azonenberg | i have three lab reports to do this weekend lol | 21:33 |
Sync | I should see what I can whip up next week, building something like that should be pretty straigth forward | 21:33 |
azonenberg | Sync: well thats just the chuck | 21:34 |
azonenberg | i have to design the body, choose a suitable motor | 21:34 |
azonenberg | a gear or belt system suitable for spinning it | 21:34 |
azonenberg | a spatter guard | 21:34 |
azonenberg | nothing particularly hard, at least for someone with more mechanical design experience than me | 21:34 |
azonenberg | But still has to be done | 21:34 |
Sync | mmh, the drive would be interesting, a flat belt would be the easiest, they support very high speeds without issues | 21:37 |
azonenberg | That was my thinking | 21:37 |
Sync | protip: put grooves in the rollers and make them thicker in the middle | 21:38 |
Sync | this will cause automatic tracking and prevents slipping at high speeds | 21:38 |
azonenberg | I was thinking some kind of a grooved belt, yes | 21:38 |
azonenberg | My biggest question right now is bearings | 21:38 |
azonenberg | The moving assembly will consist of the top chuck (4" flat disk to mount the wafer/sample on) | 21:40 |
azonenberg | the shaft | 21:40 |
azonenberg | and some kind of pulley/roller to attach to the belt | 21:40 |
azonenberg | but then i have to attach that to the stationary base somehow | 21:40 |
azonenberg | and i've never had to design anything with bearings in it lol | 21:40 |
azonenberg | i'm a computer scientist who dabbles in EE, not a mechanical engineer | 21:40 |
Sync | the bearings are the least problem here | 21:40 |
azonenberg | They're the thing i know the least about lol | 21:41 |
Sync | at 10k rpm most sealed bearings will do | 21:41 |
azonenberg | I wouldnt know a sealed bearing if it bit me on the nose lol | 21:42 |
azonenberg | how do you attach to it? | 21:42 |
berndj | i missed the start; what are you building? | 21:42 |
azonenberg | is it a solid housing and a rotor inside that you setscrew your shaft into? | 21:42 |
azonenberg | or what | 21:42 |
azonenberg | berndj: discussing spin coater design | 21:43 |
azonenberg | i'm tired of the one i have now made from 2x4s and a power drill | 21:43 |
azonenberg | i want something proper made from scratch with a real speed controller etc | 21:43 |
berndj | heh. nasa spent a billion dollars making a pen that would work in space. the russians used a pencil. | 21:43 |
berndj | 2x4 and drill is good for DIYism though | 21:44 |
azonenberg | berndj: yes | 21:44 |
azonenberg | but i have a real need to replace it | 21:44 |
azonenberg | first off, total lack of precise speed control | 21:44 |
azonenberg | Second, worse | 21:44 |
azonenberg | it's too big | 21:44 |
azonenberg | i cant use it in my fume hood, it blocks the airflow | 21:44 |
azonenberg | and i dont want solvent fumes all over the living room | 21:44 |
berndj | fair enough | 21:44 |
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 | 21:44 |
azonenberg | And i figure it'd be a good exercise in mechanical design | 21:45 |
berndj | oh it's that big | 21:45 |
berndj | of course it's that big, it's at least as big as a drill! | 21:45 |
azonenberg | actually the drill is on a flexible extension cable | 21:45 |
azonenberg | but yeah, its about 8" x 12" square | 21:46 |
azonenberg | and maybe 18" high | 21:46 |
azonenberg | so in a 24" cube fume hood, well | 21:46 |
azonenberg | the air currents arent what they should be | 21:46 |
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 | 21:46 |
Sync | if you put a centered screw in there you may get away without balancing | 21:47 |
azonenberg | ok, i'll take a look at these things, they look like they'll do | 21:48 |
Sync | they will | 21:48 |
azonenberg | i was thinking double sealed | 21:48 |
azonenberg | since stuff will be spattering all over the place | 21:48 |
Sync | you can reduce exposure by using a small circular baffle under the disc | 21:50 |
azonenberg | well, i dont expect too much | 21:50 |
azonenberg | because the chuck is 4" diameter | 21:50 |
azonenberg | and will act as a shield | 21:50 |
azonenberg | all the spatter is outward | 21:50 |
Sync | but those bearings are dirt cheap | 21:50 |
azonenberg | i'll then have some like 1/8" sheet metal or something sitting around the outside of the tray | 21:50 |
azonenberg | to catch spatter | 21:50 |
azonenberg | which will, in use, be lined with texwipes etc | 21:50 |
azonenberg | Any estimates on what i can expect to pay for the entire tool components wise? | 21:51 |
azonenberg | i was thinking in the $200 range | 21:51 |
azonenberg | counting the motors and belts | 21:51 |
azonenberg | motor* | 21:51 |
azonenberg | and electronics for the controller | 21:51 |
Sync | no way, if you get the motor new and a VFD | 21:52 |
azonenberg | i was thinking brushless DC from an RC aircraft store | 21:52 |
azonenberg | cheap speed controller | 21:53 |
azonenberg | then build my own feedback circuit around that | 21:53 |
azonenberg | brushless 3-phase* | 21:53 |
azonenberg | my back-of-the-envelope budget was $100-150 in mechancial stock and $50-100 in electronics | 21:53 |
azonenberg | too high? too low? | 21:53 |
Sync | well if you can do everything mechanical in the shop that should pan out | 21:54 |
Sync | if not, put a zero on it | 21:54 |
azonenberg | For 2K i can buy one premade lol | 21:54 |
azonenberg | I'm doign all the labor myself | 21:55 |
azonenberg | and i intend to choose manufacturing processes i can do in the shop | 21:55 |
azonenberg | so no tooling or labor expenses, just materials | 21:55 |
azonenberg | i could prob afford to drop up to 500 on the project, maybe a bit more | 21:55 |
azonenberg | Just trying to get a budgetary number | 21:55 |
Sync | yeah expect around 300-400 that is realistic | 21:59 |
azonenberg | Sounds reasonable... the main thing i care is that it gets the job done and costs less than a commercially made one | 22:00 |
azonenberg | if it fails in either respect i'm better off buying one | 22:00 |
azonenberg | Whenever i make a tool i ask myself those two things | 22:00 |
azonenberg | for example i cannot make a drill cheaper and better than one you buy at the home depot | 22:00 |
azonenberg | so i buy one | 22:00 |
didja | i'll try asking here too since it seems relevant to nanostuff | 22:01 |
didja | can you generate radio waves by mechanically oscillating a piece of metal very quickly? | 22:01 |
azonenberg | not unless there's a magnetic field involved afaik | 22:01 |
azonenberg | you should be able to generate light by running 10THz range electricity through a suitable antenna though, in theory :p | 22:02 |
Sync | let me see what I can dish out in cad real quick azonenberg | 22:03 |
berndj | didja, like a quartz crystal? | 22:04 |
berndj | not metal, but that isn't too relevant | 22:04 |
Sync | azonenberg: done | 22:18 |
Sync | ! | 22:28 |
azonenberg | Sync: sorry, dropped offline for a bit (stupid wifi card) | 22:31 |
azonenberg | what did i miss | 22:31 |
didja | azonenberg: all you need is a changing E field right? | 22:36 |
didja | because then nanoscale mechanical oscillators make a lot more sense | 22:36 |
didja | i'm again brushing up on EM | 22:36 |
Sync | http://sync-hv.de/~tmp/coater.bmp I dished out that for you azonenberg | 22:37 |
Sync | this is basically what you need | 22:37 |
azonenberg | Sync: nice | 22:45 |
azonenberg | i'll try something like that and post stuff here when i get achance | 22:46 |
--- Mon Mar 5 2012 | 00:00 |
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