[Sem] All in on the mini-SEM?

Tue Dec 16 02:44:18 UTC 2014

Hi John!
Sounds pretty exciting! 
Just thought of something: You're going to want to vent your pump exhaust through a piece of 1/2 in. OD to 1" OD clear PVC hose ASAP. Even a small amount of smoke is pretty nefarious, rivaled only by marijuana smoke. More importantly it teaches good ballast practice and serves as a practical tool for knowing when the pump is dry. A dry pump stays much cleaner and lasts much longer, especially over long periods in storage. Start by blanking off the pump and closing the ballast and running it until warms up. If it won't warm up you can run it flat out for a bit but you'll lose a few grams of oil, and your hose may pop off, especially if your hose is not all downhill and thus forms a trap. Once warm, blank off and open the ballast. The hose should immediately turn silver-grey with condensed water. Run the pump with the ballast open until this disappears. Some of the water will form larger drops, especially in a trap, I usually run until these are gone too, but I'm sure all the real benefits have rolled in long before the last drop is gone.. I guess it's just absolute proof you are finished. 

You'll probably be pretty surprised how quickly water accumulates during normal operation. This water collects relatively harmlessly in the sump. But if the sump is iron it still makes for some rust. I think I cycle my ballast every three or four pump downs.
Ultimatley you'll want to vent this water and oil out a window or something, making sure it won;t waft  into another window, drip onto the house paint, or drip on pedestrians. A catchpot is a great idea if it can be protected from rain: otherwise it will fill with rainwater and the oil will of course float to the top and be first to spill over. Generally the oil is very clean and much less harmful than motor oil, being free of additives and byproducts of combustion. Depending on the pumps history it may have process contamination, including mercury which was widely used in vacuum instruments and still used in bulb and neon sign making.

The thing about turbos is that they really are hit and miss. There's not much room for grey area: maybe 1000 hours at most. Once the bearings wear to the point where they are out of spec, they deteriorate very quickly. It becomes difficult to keep them cool, so they wear even faster. It's not long before the power supply can't keep the pump running faster than %60, at which point most controllers give up.
That having been said, I've never witnessed this happen to a pump. All of my pumps have either been removed from working equipment (ie: some 1000's or 10's of thousands of hours of bearing life left). or deteriorated to the point they won't spin up. Dunno if that seems to discredit or support my theory.

What model Pfeiffer did you get? Did you fire it up yet?

Pfeiffer says WRT to some if not all of their pumps that if the pump is not run for more than a year, the bearings must be replaced. Any thorough treatment of bearing theory would suggest this might be true, at least to some extent. Obviousky the year figure is arbitrary and probably varies with temperatuere. Pfeiffer may be particularly affected because they are the only maker I can think of that still uses steel bearings, as well as heavy steel rotors. That having been said I've let some of my pumps go 3-5 years: I was dissappointed to hear the news but it hasn't changed my habits. 

I'll  be buying the alcatel toolkit, so NB wouldn't bear that expense.  So if NB found a pump for $200 and it needed $300 bearings, a good heart should be guaranteed for $500.

Alcatel is the only maker that explicitly supports customer bearing replacement. However, there is at least one third party pump rebuilder that also offers bearings and toolkits for a wide range of pumps. Dunno the name. 

Actually, if we make a bang-up diffusion pump based vacuum system it wouldn't be half bad, but it couldn't travel. And a pvc hose

      From: John McMaster <johndmcmaster at gmail.com>
 To: Jeff Miller <mysterylectricity at yahoo.com>; Chris Murphy <chrisnoisebridge at gmail.com> 
Cc: "sem at lists.noisebridge.net" <sem at lists.noisebridge.net> 
 Sent: Friday, December 12, 2014 7:09 PM
 Subject: Re: All in on the mini-SEM?

 Heyo,
 I haven't followed the noisebridge unit, but some updates on my side if anyone is curious.

 I traced the vacuum leak to the column in my Super IIIA.  I'm having trouble safely taking apart the column to troubleshoot further.

 Over the previous weekend I picked up a small ISI SEM similar to the noisebridge unit ($500 + drive to LA and back).  Some details on it here: http://uvicrec.blogspot.com/2014/12/theyre-multiplying.html

 The guy also threw in a carbon coater.

 Anyway, it has a broken PMT and needs a small vacuum adapter that should have come in the mail today.  PMT has unknown ETA but I could steal a spare off of the Super IIIA if I wanted to test sooner.

 I also have a *huge* (over 100 lbs) pile of ISI documents (schematics, mechanical drawings, service notes, etc) I've been scanning in that one of their retired lead techs gave me.  Maybe this weekend I'll finish the digitaization process and begin uploading/organizing them.

 I have a small Pfeiffer/Balzers turbo pump system I assembled off of eBay for under $500.  It was chosen specifically because parts for this particular system are readily available to piece together.  Of course, it would be hit or miss if the bearings are sub-optimal but I imagine often times they will be good enough for hobbyist use.  I'd suggest others looking into the same route before dropping 1k on a restore kit.  I haven't decided if I'm going to attach it to the SEM once it works better.

 I get class 10k using a high power Honeywell HEPA filter in my bedroom.  Very cheap and easy to setup.

 John

 On 12/12/2014 05:56 PM, Jeff Miller wrote:

  I think we should give the mini-sem project a second chance. 

  I've been thinking about what the SEM experience at NB drove home. 
  We should think small and practical. 

  Rather than a clean room, let's think glovebox. Small glovebox, easy enough to fab.

  The manual vacuum controls have to go. It should all be electric valves, interlocked and goof proof. 
  The coater should be integrated, and interlocked with the SEM to use the same pump(s). 
 Perhaps a small, low temp vacuum oven for drying bugs and plant samples, too.

  The console has to more or less go. We have to commit to the digital platform I developed, or develop a new one.  
  Ideally, the diff pump and forepump should be replaced.with a turbo and a diaphragm pump. With that we get instant on, no exhaust fumes. and no periodic cleaning of the column parts. 
  Alcatel makes a high speed molecular drag pump. I may be wrong, but I don't think it has stator blades. So I think you can up-to-air it at full speed with no damage, and it may be able to choke down a grain of sand or two without exploding. It will be mounted upside down of course. 

  The vacuum isn't as deep as theoretical for a turbo or diff pump, but is more than sufficient for a SEM and coater. 

  I have a bunch of these pumps.  So many in fact that I'm thinking of coughing up the $1,000 for the factory toolkit (probably a bearing puller and two precision bore steel plates, if that)  to rebuild them. I think the bearings alone go for $300, but it shouldn't be hard to find a pump with bad bearings for ~$250.  The pumps have a very high foreline pressure tolerance, 30 torr I think: I've seen them backed with run-of-the-mill two stage diaphragm pumps from Gast.  Meanwhile, high performance four stage diaphragm pumps seem to be fetching less than half of what I was getting for 
  them 5 years ago, $150 might buy a working pump and $200 more might effectively rebuild it. 

  As it turns out, I've already done some of the heavy lifting. It's probably been close to ten years now since I first wanted to make the mini-sem portable, to bring to classrooms. To that end I had custom pieces milled that attach to the top and bottom vacuum ports, and convert them to the KF standard.  Short lengths of stainless bellow also show up cheap enough these days. 
  Perhaps as much as anything, it would highlight vacuum technology as well as the SEM itself. 

  I might have almost everything we need on hand. I can see lending the core components for proof of 
  concept , or until they can be found serendipitously on ebay.. 

  For all the little pieces and parts, $200-$300 might be a good guess and represent a good working minimum budget for retrofitting the valves and 
  piping.  If we have to do it from scratch, the glovebox could be another $150 or so but further down the line. 

  I say pitch it as far more user friendly and less invasive, and see if we can get funds allocated.  
  Anyone care any more? How are you guys coming along with your SEMS, coaters, and turbos? 

  -Jeff 

      From: Chris Murphy <chrisnoisebridge at gmail.com>
 To: John McMaster <johndmcmaster at gmail.com> 
 Cc: "sem at lists.noisebridge.net" <sem at lists.noisebridge.net> 
 Sent: Tuesday, September 2, 2014 12:13 AM
 Subject: Re: [Sem] Picked up a sputter coater

 Well that's a breakthrough. Maybe Alan has something to coat. 

 Sent from my iPhone

 > On Sep 1, 2014, at 22:41, John McMaster <johndmcmaster at gmail.com> wrote:
 > 
 > ...3.5 hours of driving each way later.  Hit me up if you need to coat something.  I have a gold target for it
 > _______________________________________________
 > SEM mailing list
 > SEM at lists.noisebridge.net
 > https://www.noisebridge.net/mailman/listinfo/sem 

 _______________________________________________
 SEM mailing list
 SEM at lists.noisebridge.net
 https://www.noisebridge.net/mailman/listinfo/sem

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.noisebridge.net/pipermail/sem/attachments/20141216/cc3311e6/attachment-0003.html>