#homecmos IRC log for Friday, 2013-03-22

glowplugWent to mcdonalds.  =)00:16
glowplugAgreed this is not easy stuff.  It will be very painful and slow.00:16
glowplugThe only way to know if 1um is possible with this design is to try it.  =)00:17
Sync_I'll see tomorrow if it is feasable00:17
Sync_I have no small angular contact bearings but that should be no problem00:18
glowplugYou have some way of making them?00:20
Sync_I'll just order some00:21
Sync_making bearings is no fun00:21
Sync_and 7200 angular contact bearings are like $4 each00:25
glowplugIs that like a rollerscate bearing?00:28
Sync_a rollerskate bearing has no angular contact00:30
Sync_which is important here :D00:36
glowplugI did not know about these.  They are just more robust in radial and axial directions.00:39
glowplugDo you plan on trying to copy the design I linked earlier (the aluminum one)?00:40
Sync_it's not about being more robust00:41
Sync_you can preload them in O or X configuration to get a precise spindle constraint00:41
glowplugSo this bearing is going to hold the end of the threaded rod.00:42
glowplugI was going to buy a rollerscate bearing.  Good thing you said something.  Haha00:42
glowplugI've never done preloading so I have to figure all of that out.  The design says "anti backlash nut" I'm assuming thats where I put my normal m3 hex nut?00:44
Sync_the problem is with a regular bearing that while it supports your piece radially and axially it does so with play00:48
glowplugAlright.  I'm not sure that m3 antibacklash nuts exist.00:48
glowplugWhich is insanely important.  So preloading it keeps everything level.00:48
Sync_huh. there seems to be standards which specify m8x0.2500:49
Sync_well the preload forces the assembly in a certain position00:49
glowplug.25mm pitch????00:50
glowplugI wonder how expensive that is per meter.  o.O00:52
Sync_I guess you are not going to get threaded rod in that size00:53
glowplugHow do you get m8x.25 then?00:55
Sync_by making your own spindle?00:56
glowplugI'm good on that.  Haha01:00
glowplugI think that 10031AB is an m3 antibacklash nut but its $43.  O.o01:00
glowplugThis is interesting.01:03
Sync_my dumb lathe only goes to 0.45 pitch01:07
Sync_it doesn't need to be that fancy01:07
Sync_you can just use a split nut with two orings01:08
Sync_or a clampable nut01:08
glowplugIf thats true then I should have no problem putting that mechanism in.  I can just design the cuts for that mechanism into the stage.01:08
glowplugI don't have a co2 cutter yet I'm just going to have a local shop cut my acrylic parts for now.01:09
glowplugI might go into i3 detroit do it for free.01:09
Sync_oh detroit01:10
Sync_I was there once01:10
glowplugYou poor soul...01:11
glowplugJust kidding its not that bad here.  There are worse places on Earth.  =)01:11
Sync_well it was in 99 or something01:12
glowplugI see. 8)01:13
glowplugI'm going to do some more updates to the wiki now then.  We have a good amount of info at add.01:13
glowplug*to add01:13
Sync_visited some relatives in grand rapids01:13
glowplugAhh I see.  Grand Rapids is actually really nice.  I was born in Lansing which is right next to it.  =)01:14
Sync_bah. conflict of interest01:20
Sync_I'm tired but also hungry01:20
glowplugSame here.  My solution was McDonalds.01:20
glowplugConflict... Resolved...01:21
Sync_well I either go to bed hungry or eat something and go to bed later01:22
glowplugOption #2.  8)01:26
glowplugWhere did you find the angular contact bearings?01:27
glowplugThey are $28 on mcmaster.  O.o01:29
Sync_my local bearing shop01:36
Sync_interestingly bearings die pretty fast in vacuum applications01:38
glowplugOk so the 7200 has a 10mm inner diameter and my threaded rod is 3mm.01:39
Sync_yes that is one of the reasons I want a bigger spindle01:40
glowplugI will succeed....01:40
Sync_one of the issues with the spinde so thin is that it will bend and flex01:41
Sync_even under the small load01:42
glowplugI have a solution for that.01:42
glowplugTons of nuts.  =)01:42
glowplugActually wait there shouldn't be any flex.01:44
glowplugNot if the threaded rod is only ~100mm long.01:44
Sync_hm probably, still larger is better01:50
Sync_and huh 1/4-32 UNS is expensive01:50
glowplugWhat is that?01:52
Sync_a thread01:52
glowplugOh I see.01:52
glowplugWell I found a 3mm to 5mm coupler they are $4 on Ebay.01:53
Sync_hm, I really think you are better off using a larger spindle01:54
Sync_even if it is only less fiddly to work with01:54
glowplugOk I didn't notice this before.01:56
glowplugThere is .5mm "low-strength steel" rod on mcmaster.01:56
glowplugIn m501:56
glowplugThese are interesting too. 50mm long .5mm pitch bolts.02:11
glowplugNot quite long enough I suppose.02:13
glowplugI guess the new wiki needs a logo.  O.o02:58
Sync_I thought about that too03:04
glowplugI'll try to toss something together tomorrow.03:08
glowplugStill working on the litho wiki.03:08
glowplugDo you know how to measure changes in X and Y with a single interferometer?03:35
Sync_beamsplitter glowplug03:55
glowplugYes but how do you position the sensor optics?03:56
Sync_after it03:57
Sync_you just put in two interferometers03:58
Sync_die google03:59
glowplugAlright so the "Remote Detector and Interferometer" boxes.04:07
glowplugThey take in one beam, offset it, and read the reflection with some optics?04:08
Sync_you get a fringe pattern04:11
Sync_and the intensity varies04:11
Sync_which you can read with a photodiode04:12
glowplugI know how interferometers work.  =)04:12
glowplugI figured out what those mysterious boxes are.  They are "linear interferometers".04:12
glowplugA system like that might be more difficult and expensive (due to need for increased optics quality) than just having two seperate interferometers.04:33
glowplugWhich this really is two seperate interferometers operating off of a single beam source.04:33
glowplugYeah I'm going to try it the other way.  Lasers are cheap optics are expensive.  Screw that.  Haha04:42
Sync_well you are only going to save one beamsplitter05:30
B0101yikes... chlorine gas is never fun to play with, more so when you have a gas leak in your test chamber05:30
glowplugYou save all of the internal components that comprise a "linear interferometer" which is tons of mirrors, a beam splitter, and a retroreflector.  The system is also very very sensitive.05:39
glowplugYou have to be careful dawg.  O_O05:39
Sync_huh how are you going to make a interferometer with just a laser?05:40
glowplugThey are called "linear interferometers" but its confusing.05:41
glowplugThey are really black boxes with tons of integrated components.  Two of those are added to the configuration to make it work.05:41
glowplugSo you have all of the necessary components of a single interferometer.  Plus the two black boxes which are extremely complex.  Plus massively increased system sensitivity.05:42
glowplugIt's getting late though going to bed.  8)05:49
Sync_glowplug: the integrated linear ones seem to be just michelsons with retroreflectors05:57
Sync_yeah two prisms and a beamsplitter will do06:07
nmz787there's a video online of a $20 interferometer07:15
nmz787using a CD case, laser pointer, mirrors and a cheap lens07:16
Sync_I just ordered some stuff from EO07:17
Sync_you can make one for under $200, that's not too bad07:18
nmz787if you just need micron-ish resolution, you probably just need something like the $20 one and a photodiode and comparator or schmitt trigger07:20
Sync_prisms are cheap and beamsplitter glass too07:21
nmz787if you want better res then you need to keep the sinosoid pretty noise-free, and get an ADC instead of the comparator/schmitt07:22
Sync_well, if it only has to have micron resolution I'd use glass scales all day long07:23
nmz787that's not consistent as interference though, so I guess it depends on your goal07:26
nmz787how do you read glass scales?07:27
Sync_rs422 output07:27
nmz787oh so it's not roll-your-own system?07:29
nmz787shars.com says $52007:29
nmz787"(the smallest are just 5 m apart)"07:30
Sync_that's not true07:31
Sync_you can get them with 100nm resolution07:31
nmz787heh, I don't like suppliers that don't list prices07:49
Sync_I don't care, I pay what they want07:50
Sync_but actually it is not that bad nmz787, if you get chinese ones with 500nm resolution they are like 200$ for 70mm length09:16
Sync_and not much more for longer ones09:16
glowplugGood morning.  8)16:14
glowplugI agree with the glass scales being very accurate but we already have *some* amount of mechanical accuracy built into the system via the leadscrew assembly.  The interferometers will be a reliable way to know if something else in our system is broken instead of guessing all day.16:15
glowplugnmz I agree they can be built for very cheaply.  My current plan (need to update the wiki) is to buy a giant piece of 50/50 glass and CNC hundreds of tiny 10x10mm squares out of it.  That gives you $1 beamsplitters with extremely good optical quality.16:16
glowplugIn terms of replicating the linear box units lets call them.  As you increase the amount of sensor positions in the beam network you multiply the system sensitivity by many times.16:17
glowplugI still think that two beam sources will give the best price/performance/reliability ratio.16:17
Sync_well if you have alot of 50/50 splitters a second source is a waste16:32
glowplugThat is technically correct.  But aligning the system with a second beam is many many times more difficult.16:49
glowplugThe alignment instruments need to be many times more precise.  And I'm not sure if the quality of the optics I mentioned is high enough for a setup like that.16:50
glowplugThe optics they are using in the PDF you linked are probably $10,000+16:50
Sync_I just ordered stuff from EO to try that16:50
Sync_I like the idea of using prisms for the beam return16:51
Sync_that way you can shift the receiver diode a bit16:51
glowplugGood luck.  Haha16:52
glowplugThe prisms can be fashioned from multiple standard mirrors correct?16:52
Sync_yes but it'll be annoying to align that16:54
Sync_and they are only $2916:54
glowplug$29 each! Ouch..16:55
glowplugYou can get another HeNe tube for $50.16:56
glowplugThis is why I abandoned the single beam idea.16:56
Sync_wat, you need the prisms anyway16:56
glowplugFor two standard michealsons you only need beamsplitters and mirrors.16:56
glowplugAnd two beam sources.16:57
Sync_yes but that is not as compact16:57
Sync_with two prisms and a beamsplitter you can move the receiver to the side of the input beam16:58
Sync_which is cool16:58
Sync_and $29 per piece, come on16:58
glowplugThat is extremely cool.  But I have plenty of desk space and not very much money.  HAha16:58
Sync_that's not too bad16:58
glowplugI'm shooting for $29 for the entire assembly.  8)16:59
glowplugI wonder is it possible to put the entire thing under vacuum.  That would make the lasers more accurate and reduce the chance of contamination.17:03
glowplugEverything is electronically controlled anyways.17:04
Sync_then you cannot make it out of acrylic17:10
glowplugWhy not?17:15
Sync_outgassing properties17:15
glowplugThere are retail acrylic chambers that pull 30"17:17
Sync_yes, but 30" is not really a vacuum17:18
Sync_at least from my vacuum perspective17:18
glowplugI knew that was coming.  Haha17:19
glowplugI agree that is not 0 torr but it would still greatly increase laser accuracy and greatly reduce contamination for a very low cost.17:20
diginet1the best way a DIYer can get a vacuum is a bell jar17:20
Sync_and then do what? suck on it?17:20
diginet1acrylic is just about the worst possible thing I can imagine for vacuum stuff17:20
diginet1Sync_: well you need a pump too :P17:21
diginet1but I more meant for the chamber17:21
glowplugI wonder why they sell $2000 acrylic vacuum chambers then.17:21
Sync_to outgas resin17:21
diginet1yeah, calling that a "vacuum" is a bit of a stretch17:21
glowplugSo the acrylic chamber wont hold any amount of vacuum that is useful for increasing beam stability and reducing contamination.17:22
Sync_I mean, yeah it is lower than atmosphere but oh well17:22
glowplugThat just doesn't seem realistic.17:22
glowplugRemember it's a $500 litho device.  No need for a $1500 bell jar.17:23
Sync_I'd just put some shields17:23
glowplugIt basically is a shield with a low vacuum.17:26
glowplugI mean... maybe its not worth the extra ~$50.17:26
glowplugBut something that both improves beam stabilit and reduces contamination for such a low cost is at least worth examining17:26
Sync_that came out pretty well19:38
Sync_just made a spindle19:44
Sync_rather amazed how backlash free it is19:45
Sync_only the material pairing isn't the best19:46
Sync_yeah I'll need oil but then it'll work fine19:51
Sync_pitch error is very low19:52
Sync_under 1/100mm in 5cm19:52
Sync_backlash when properly adjusted maybe 200nm19:52
Sync_but that is probably my setup19:52
Sync_because it cannot really have backlash19:52
Sync_the next one will have a brass nut and case hardened spindle19:54
Sync_yeah :) I like it19:58
glowplugHoly crap that is great!20:20
glowplugWhat material did you use for the stage?20:20
Sync_I did not build a stage yet, just the spindles20:25
Sync_I'll probably use aluminium20:25
glowplugHow did you test the spindle accuracy?20:26
Sync_mahr extramess 2001 and gage blocks20:26
glowplugAha! I see!20:28
glowplugAnd your leadscrew is standard .5 pitch stainless?20:28
Sync_aluminium, cut it myself20:29
glowplugYour joking?  That is seriously fantastic!20:30
glowplugI would buy that from you in a heartbeat!  How much for 200mm? Haha20:31
Sync_I'll verify that next week but it looks quite acceptable20:32
glowplugI was actually going to look at alu I saw it mentioned.  I would totally buy some as soon as you think they are ready.  You made them from M8 rod?20:36
Sync_no, I took some stock, turned it to 7.90mm and cut a thread20:38
Sync_bb in 1520:38
glowplugSo it is 7.9mm in diameter.  That is A LOT better than the m3 rod from mcmaster.20:40
Sync_no shit23:36
Sync_that's why I wanted to do it that way23:36
glowplugEasy there!  Haha23:37
glowplugI know it's better thats pretty obvious.  I just didn't realize you had a precision lathe and mad skills.  =)23:38
Sync_I'm more or less amazed that the pitch error is that good23:38
Sync_gotta verify that after my exams23:38
glowplugMe too thats awesome if it works.  =)23:40
Sync_but in reality it does not matter23:42
glowplugWhy is that?23:42
glowplugIt matters for me I'm the first customer of Sync_'s Custom Aluminum Threaded Rods Inc.23:43
Sync_because if you use closed loop positioning with the interferometers only backlash will hurt you23:45
Sync_but for that to work you need a very rigidly coupled system23:45
Sync_and no backlash23:46
Sync_but the next ones will be made from c45 steel and brass nuts23:47
Sync_the Al-Al pairing likes to bind23:47
glowplugAhh so you will be using steel.  Can your lathe cut steel?23:52
glowplugI think we can get rid of backlash pretty easily using the DIY spring method.23:52
glowplugAnd I agree about positioning otherwise.  As long as we have good absolute feedback the accuracy of the leadscrews is not super important.23:53
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