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I am a new member interested in trying to set up A vacuum chamber to deposit metal coating on telescope mirors. Salutations

I am building a vacuum system. I have no knowledge other than what I have discovered on the internet and a little personal experience of what has not worked well. I have questions. My vacuum system (powered by a Welch 8920 two stage rotary vane pump rated at 7.2 cfm) will serve three functions. First, a degassing chamber for various casting materials, second, for thermoforming, and third, as a vacuum chuck (work-holding device) for my Bridgeport milling machine. As you can see I do not need a high vacuum. Each of these uses will bring their own problems and having a knowledgeable source for the vacuum portion of these problems would be great. Right now I am building the degassing chamber. I am a semi retired draftsman enjoying my shop and trying to be useful. Nice to meet you. Bruce

Hello all, As to introduce myself to the group I will spin you a yarn as to how I found myself here. My tale starts a year or so ago learning how to cast using dental plaster for a very large 16 foot long gaming table (Hirst arts molds). Hundreds of hours and 100 lbs of dental plaster into the project i found this amazing stuff called allumite at the local hobby lobby. Using permission from Hirst to create my own to speed up the project, Eureka, I was now churning out 9x the amount of tiles I needed at the same time and quicker set times to boot! My sanity was saved It was finicky stuff, super quick set times etc but it got the job done. Then the use cases started to hit me and got me thinking about being able to duplicate other one-off projects, etc. A few months later and I've since moved to Smooth-on Products and while I've had great success I still get voids and bubbles etc. So began my search into pressure and vacuum casting. I picked up a 3CFM pump off of amazon and a chamber/lid from Ebay for what seemed like a good price. My first test was degassing silicone. It worked great but i didn't use a large enough cup, it nearly overflowed as i scrambled for the shutoff switch. Lesson learned! I've since been degassing my resins and pouring them into the molds I've made however its still not exactly perfect. So I've done my homework and it looks like what I'd like to try next is a liquid feedthru for my degassed resin. I checked online and all I could find was abbess instruments. I spoke with them but they essentially would not talk to me even though I was interested with buying one of their chambers. I asked if they would sell me a liquid feed thru kit they do-not/would-not sell one. It makes me wonder how they stay in business. Fast forward to today: Since all I really need is to modify the lexan lid to my chamber this sound like an easy DIY. Would any of you have a site or guide how to DIY a liquid feed through? Thoughts? comments? Thank you for your time...

I am a new member retired from the government; now do part time contract work from time to time. I purchased a Veeco EP-2A-1 diffusion pump from Ebay for a very low cost therefore willing to take a risk. I tried to get some information from the Web but couldn't find any technical information for this pump. I decided to test it out using my old version of the Welch 1405 for backing, decided to try about 70 cc of Specialty Fluids Co.version of type 704. With my limited resources it seems to work OK. However I want to make sure that the correct charge is used. Does anyone have any information for this diffusion pump; its correct fluid charge; backing pump requirements ?? Is there some archive on the Web for vintage vacuum pumps; ie the old Welch 1405? I did find one source http://www.liberatedmanuals.com/ after spending hours searching. Thanks

Hello, I've just joined this group. My background is electronics (TV), now pensioned off and I want to try my hand at some vacuum work with electron tubes etc. I have the above controller which looks like it can read both a Pirani and Ionization gauge. I'm looking for a manual for it, schematic, instructions, etc. Can anyone help with this please. Thanks, Don Black.

Hi everybody, I'm a new guy in the group. I joint this, because I have serious plans to build my own vacuum-chamber (10E-5 to 10E-7 mBar). I decided to go with a diffusion pump and a system as already decribed by "atm_ken_hunter" under the "Files" section in this group. Following link shows a screenshot of the basic concept I want to build (taken out from the File posted by "atm_ken_hunter"): https://lh5.googleusercontent.com/-Na-eiKFOMx4/UKdkpDWNMVI/AAAAAAAAA7U/wiOLFunRLQo/w318-h293-n-k/vacuum_concept.png In that concept a "baffle" is indicated. I wonder, how such a "baffle" looks like, how complicated it is, how it works and functions etc. I am even more curious about that "baffle" because in Ebay is an auction, where somebody points out, that he is selling a diffusion pump together with a "baffle" and that the "baffle" alone would already costs 2000.- Euro (approx. 2500.- US$ !!!). http://www.ebay.de/itm/Varian-Agilent-Oldiffusionspumpe-VHS-4-1200-l-s-Saugleistung-Baffle-Hochvakuum-/170940721377?pt=Laborger%C3%A4te_instrumente&hash=item27ccdc68e1 Wow, something that expensive was not on my bill-of-material list so far. Where can I learn more about "baffles", their function and design, and how to get a or build a "cheap" one. Thanks everybody for your support. Cheers Alexander

Drew, I've been lurking in the Vacuum-X group for a few years; I have an old (like nice wood case old) Sloan Omni II Deposition Control Master + Sloan SCR 7.5 (35A) that are about to hit the dust bin if I don't find them a new home. The Omni II reads a QCM and controls based on frequency shift. You have to do the conversion to rate yourself but has the ability to adjust power based on frequency shift for rate feedback (it has audible feedback that sounds a bit like a theremin which will be missed in the lab). This thing works but we're replacing it with a Sycon STM-2. I also have a whole bunch of tungsten coil baskets up for grabs as well. We're moving our shop so I'm thinking if you cover shipping their yours. If you're interested, or can suggest someone on the group who might put it to good use, please let me know. Best regards, Dave Senior Research Engineer Luxel Corp. www.luxel.com A good politician is like a good football coach. He has to be smart enough to do a good job but dumb enough to think it matters

I've uploaded pictures of a baffle we recently took off a system (http://groups.yahoo.com/group/VacuumX/photos/album/1665179354/pic/list). There's a disk with an elliptical cross section (think flying saucer) suspended in the middle of the fitting by four tubes (two on the bottom, two on the top). The baffle is water cooled and I suspect the water flows both through a water jacket on the outside as well as through the disk in the middle. No idea of the structure inside of the baffle portion but it has a pretty thin wall. So there's a bit more to these than the name would imply. David A. Grove Luxel Corp. www.luxel.com A good politician is like a good football coach. He has to be smart enough to do a good job but dumb enough to think it matters.

What's it like when you put the pumpkin into the vacuum chamber? ;-} Guy Brandenburg, Washington, DC http://gfbrandenburg.wordpress.com/ http://home.earthlink.net/~gfbranden/GFB_Home_Page.html ============================

Hey guys, Here is my latest addition to "baby George". I melted the previous high amp pass thru by putting way to much current thru it. The previous unit was made of 9 each 1/4" bolts passing thru Scotch Weld 2216 epoxy. Turns out 1/4" rods are rated for about 120 amps at best and when you pass 360 amps thru them they get really hot. I guess I missed the part about serial current being less than parallel current. Who knew that 90 amps x 12 volts is not the same thing as 360 amps at 3 volts. It was all bad from there. But I choose to move on and not live in the past. The new pass thru's (now there are 2 of them) are made with 3/8" rods. The epoxy and 1/2" thick acrylic spacer plate are the same. I once again discovered that 1/8" o-rings in square o-ring grooves are the answer to making vacuum tight seals. Note that 1/4" o-rings in curved grooves are not the answer to anything. Just thought you would like to see a poor boy's solution to high amperage pass thru of the chamber wall. The 360 amps is needed for the 4 each tungsten emitters in parallel. With 9 separate coil stations I need 9 separate pass thru. I do the switching outside the chamber and feed the full current to each quad emitter station. It is a rats nest of fiberglass sock shielded welding cable inside the chamber but them tungsten coils do get hot quick now. No more waiting for the the slow coil to heat up. They all get to hot fast and I am no where near the edge of the 12kw supply. Drew in sunny Florida

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I have several A/C compressor housings out back and it occurred to me that if I could cut them in half a make a good seal they would make a good chamber. Does anyone have any suggestions on how to make a sealing surface after I cut them in half at the equator? Russell

Every so often, I am recently finding that a haze remains on mirrors that I have cleaned and aluminized, even ones that I have stripped. I am wondering if it might be from the composition of the paper towels I use for the final drying... Any thoughts? Guy Brandenburg, Washington, DC http://gfbrandenburg.wordpress.com/ http://home.earthlink.net/~gfbranden/GFB_Home_Page.html ============================

A friend of mine suggested Alconox as a new cleaning agent for use on mirrors prior to aluminization. I have tried it and found that it seems to work many, many times faster and more effectively at producing a mirror that the water flows off of like a sheet. No other detergent comes close. Nobody paid me anything for this testimonial; I don't know if anybody on this list has tried the stuff. Guy Brandenburg, Washington, DC http://gfbrandenburg.wordpress.com/ http://home.earthlink.net/~gfbranden/GFB_Home_Page.html ============================

Hello, Does anybody have the ability to calculate the TIO2 thin film layer thickness and refractive index, form spectrometer measurement datas? I attached a folder and files to the files section. Folder name: Thin film thickness. Where is two excel files. I did a transmittance measurement of a sample, where 150nm Thick Tio2 film was evaporated. The substrate normal BK7 glass. I can't compute the refractive index and the thickness from the datas because I don't know the methode, and the lack of knowledge. I need this values for tooling factor calc. Can anybody help me? Thank's a lot! Attila Schné

Was wondering what an acceptable thickness - in steel- would be for a square welded chamber 22 inches in diameter? !/2 inch steel sound OK?? This is to coat mirrors with. Read the archives about a formula but people didn't seem to agree on it. Ric

Hello! I need to recoat two small mirror. One of them is 15mm diam and maybe 20gramm, the other is 24mmx36mm also very light. I have no idea how can I put the face down to the planetary holder. I thought maybe I use tesafix® 62855 double sided tape. Which can hold the mirror. Anybody tried such a way to hold mirror in the chamber? BR Attila Schné

Okay, I have been having trouble achieving a suitable vacuum. Today i replaced the o-ring seal on my diffusion pump. While I had it out I found the nameplate that said "use 50cc of DP oil. When I poured it out (much spilling) I discovered that I had way too much. Probably 100cc. After adjusting the quantity the pump worked like new. I got to 10X10-5, without using the cold trap. I am sure that with the cold trap I will do much better. On to coat some mirrors. Jerry

Just finished machining a 6061 Aluminum Baseplate for my Bell Jar. It's 14" in diameter by 1" Thick with a 4" hole in the center and drilled for a Conflat. I've yet to decide what type feedthroughs I'll be drilling holes for. It's the first component in my Vacuum System project. I turned it to as good a surface finish that I could muster, but still would like to finish it to as near a mirror surface as possible, regardless if that entails more machining or hand polishing?? It is darn close now, but, needs that last little Phuttt. Any suggestions? I'm thinking you guys resurface or polish you pump-plates now and then. Tom M.

Can anyone tell me if TRIVEX --a plastic can be aluminized for telescope use?