Latest vacuum setup

[Burkhardt]

I have been experimenting with vacuum clamps and built at one point a roots blower pump that was way too powerful and noisy for my small part purposes.

Lately I used a smaller dual rocking piston 3/4 hp pump (like the Gast pumps) with good success. Not only very quit but also great holding power with two or more 4x4" pods. However, getting it to hold from pump turn-on seems to be a well known issue with such small pumps.

Today I installed a combined manifold/storage tank that I made from a 10' section of black 4" ABS drainage pipe. Cut into six 20" sections it is compact and tucks in neatly under the CNC table. One mistake was to machine the end caps from MDF. Even after coating with 2 thick layers of acrylic paint it still leaked around the joints. It took a generous smear with silicone sealant to get it to hold tight. It would be much better to make the caps out of ABS or PVC, too.

I wanted to make the distance between the storage and the pods as short as possible and with good sized 1/2" fittings/tube to allow for a serious "suck" event when the ball valve (natural gas valve) is turned on. The filters in the lines to the pods are 3/8" universal fuel filters from Autozone. They are transparent and will show when I need to blow them out (cheap, too).

In Action:
https://lh4.googleusercontent.com/-FjGsW0gh3I4/UpbEHqK7oZI/AAAAAAAAEX0/r-KCIrDkJCs/w1024-h783-no/DSC02014.JPG

Interesting effect: I managed to cut into the area of the vacuum pods by mistake but I did not lose vacuum completely. The fine chips clogged the gap between the work piece and the pod. While a bit reduced, the vacuum held up to the end of the cut.
https://lh3.googleusercontent.com/-n_w66xL7l8Q/UpbEIn8HhqI/AAAAAAAAEX8/mix4AWeFKJ8/w1024-h768-no/DSC02016.JPG

[dana_swift]

You are lucky to have gotten away with cutting into the vacuum area and still keeping your setup. Consider Bradys vacuum sandwich hold-down approach, it lets you cut through the material and not risk losing the vacuum.

When I cut through the material, my pressure usually starts down pretty quick. Thats with the 5hp Becker pump running full time, I usually have to put tape over the cuts to keep the vacuum level up.

D

[Burkhardt]

You are lucky to have gotten away with cutting into the vacuum area and still keeping your setup.

Well, sometimes it is better to be lucky than smart :rolleyes:

That was already the second screw-up on this job. First I ran into the limit switch which makes the steppers stop hard and usually lose a few steps. Then I cut into the pods and thought that was it. But it held on. Probably because my pods have a solid mdf surface (no grooves) with only a few holes near the center and the weather strip gasket compresses to maybe 20/1000 thickness or less. It does not take much to clog the remaining gap.

But I would be interested in Brady's setup. Got a link? There are dozens of vacuum related posts here.

Thanks, Gert

[gpinard]

http://www.talkshopbot.com/forum/showthread.php?t=11481 :)

[Burkhardt]

http://www.talkshopbot.com/forum/showthread.php?t=11481 :)
Thanks for the link, that is indeed an interesting technique. I will try it on the next job with small/thin parts.

Update on my new vacuum setup: I blew it.

I am a bit embarrassed to describe what I did today but then it is too funny not to post.

So far I had the little vacuum pump just sitting on the floor with cables snaking around my feet and the cap dangling about. Not really the safe way to do it. Therefore I mounted it properly below my machine with junction boxes and nicely routed wiring. After that I reconnected the hoses and turned the pump on to test. Really strange, the vac gage did not show anything but I heard a slight and increasing hiss. Before the funny symptoms made their way into my brain for processing and reaction there was an ear splitting explosion and the bottom cap of my storage tubes blew off.

As you can imagine I did not pay attention when I reconnected the pump hose. The pump is built completely symmetrical with only labels that show what is in and out. Sure enough I plugged the hose onto the pump exit.

Oh well. I did not like the MDF caps anyway.

[scottp55]

Funny G. , Just mentioned your rig to my Dad yesterday as our manifold shows up Monday. I'll have to tell him it went bye-bye with a BOOM.:)

[Brady Watson]

Cheap...durable...voluminuous...11 gal (HF) or 10 gal (HD)

-B

[Burkhardt]

Cheap...durable...voluminuous...11 gal (HF) or 10 gal (HD)

-B

I do have one of those. The major reason to build one from the ABS pipe was the more compact installation and the bigger fittings. All the air tanks I have seen have only a single 1/4" connection. I have individual 1/2" barbs on my manifold and the bigger the fittings are the more instant the suck-down happens at the pod.

I am just going to get a new pipe. It is only 24 bucks at HD.

[Brady Watson]

...the bigger the fittings are the more instant the suck-down happens at the pod.

Yes. You can also use a shopvac to evacuate the pods in rapid order & employ a sewer check valve (flapper type only - search 'ova da hump' on here) and use your Gast to shoot you right up to max Hg". Once you get up to holding Hg, turn off the shopvac. As soon as you flip the valve to let the Gast suck air, it rockets up to max Hg in less than a second. No storage tank of any kind required.


I am just going to get a new pipe. It is only 24 bucks at HD.

Watch those big diameter plastic pipes. Not only are they not rated for pressure - they aren't rated for vacuum & can implode. 3" and under should be fine. 6"+ would be a no-no.

-B

[Burkhardt]

....Watch those big diameter plastic pipes. Not only are they not rated for pressure - they aren't rated for vacuum & can implode. 3" and under should be fine. 6"+ would be a no-no. ........

Thanks for the warning. I will never (intentionally) apply air pressure to plastic pipes, no matter what diameter, and especially not PVC. It is prohibited for good reasons.

I have fewer concerns about vacuum. The absolute pressure is quite low, ABS is very impact resistant (no shatter) and the drainage pipe has a foamed core resulting in a pretty stiff sandwich structure. I did not calculate it but my engineering gut feel has a big safety margin.

The shopvac idea is great but I don't have a shopvac. My dust extractor uses a high volume blower with very low vacuum pressure. That said I have not tried it and maybe it still helps.

[dana_swift]

I have to agree with Brady regarding pressure in large plastic pipes. The energy contained in a pressurized pipe increases rapidly as the diameter increases, so a rupture can be catastrophic.

However for vacuum.. my attitude is "try it". Because the pipe is basically round, the vacuum pushes the plastic together. Not that its unable to deform under pressure, but if failure occurs the pipe just sucks down and becomes caved in. No real harm done other than having to go figure out something else that might work better. There is no safety issue until you are talking about a really large vacuum storage failure.

I will share a story on myself: When I was using a shopvac as a dust collector, I rigged up a metal trash can as a cyclone separator. What happened is the very low vacuum level generated by the shopvac collapsed the trash can before my eyes! To say I was stunned is to understate my reaction. However it was harmless. What I did was beat the trash can back into semi-round shape with a hammer, then use the bot to build a reinforcement skeleton frame to go inside the trash can to give it strength. Then the system worked well until I bought a commercial cyclone dust collector. I ended up with a very wrinkled trash can.

Later when I bought the 5hp Becker vacuum pump I tried using industrial reinforced 3/4" garden hose to transfer vacuum from the main pvc line to the moving Buddy table. That worked just great even at near perfect vacuum. The extra thick walls and reinforcement of the hose just squishes down a bit, but holds itself open even with the bot moving around all the time and bending and flexing the hoses. That was cheap, easy, and I recommend it if anybody needs a flexible vacuum connection.

So.. as to trying large pipes with vacuum. I wouldn't hesitate to try it, as I expect it would have the same benefits of strength the garden hoses have, then I am willing to make mistakes for the sake of finding the limits. Especially when there is not an obvious safety concern. Garden hoses are not rated for negative pressures, yet they work fine. For the same reason PVC is worth a try.

Vacuum is inherently limited (the way we use it) to 14.7psi maximum + very small barometric variations. Altitude just makes the number go down to safer values.

My only caveat would be to be sure the pipe is not gouged or kinked as that is like a crack in glass which might weaken the pipe to where it would introduce a starting point for a failure.

Anybody wanting to contribute to an experiment, I would hook up a 10' section of 6" PVC to my Becker pump and just see what it will take. Then I could take it to a very good vacuum with my Gast. My bet is it will hold up very nicely. Anybody care to contribute to the cost of the experiment? One pipe, two end caps. I would just drill and tap a vacuum line to the end of a cap for the test.

If anybody has had a large PVC pipe collapse under vacuum pressure I would love to hear about it. Photos would be nice too! Could save the experiment!

D

[srwtlc]

If concerned about collapsing, you could make some plywood plugs with holes in them (guess that makes them not a plug) and adhere them in place inside the pipe for reinforcement.

[Burkhardt]

.........Anybody wanting to contribute to an experiment, I would hook up a 10' section of 6" PVC to my Becker pump and just see what it will take. ......

Might be a fun Mystbuster style experiment but the pipe manufacturers have already done that. See for instance page 21 of this document (http://corr-tech.com/EG-all.pdf)about external pressure. If I read it right, 6" PVC in schedule 40 wall would be good short term for 54 psi and in sched 80 for 215 psi. Well below the 14.5 psi atmospheric pressure anyway. I did not see it for the ABS pipe but I assume the thick foam core wall may resist buckling under external pressure even better.

[dana_swift]

Thank you Gert- that is a really informative document.

It says for positive pressure it wont take much. Negative pressures (vacuum) are not included because it is just 14.7 psi further away from the limit.

Sounds like my experiment suggestion will probably result in a big empty pipe :)

D

[genek]

The best vacuum that one can pull on earth is 29.9 inches of mercury. At that pressure water is boiling at ambient temperature. most of our piping is designed to hold pressure, in doing so most will hold about the same outside pressure that it will hold as a positive inside pressure. as you lower the inside pressure the outside pressure goes up. The strongest part of any pipe is the weakest part of that pipe, That is where the pipe will fail under pressure or under vacuum. Here in eastern Kentucky there are saw mills that produce treated wood. they roll the lumber in on a huge rail system into a huge chamber, pull a vacuum down to 29.9 and hold it for 24 hours, then when all of the air is pulled from the wood they pump in the solution that they treat with. while they are pulling the vacuum you can hear the wood moan, crack and pop. you can actually see steam coming out of the exhaust of the giant vacuum pump.

[Burkhardt]

I fixed the storage tubes that I blew up last week and made new pods/pucks. I really needed it because I had to cut a few parts on the range extender table (I use it when the 34" x-movement of the gantry is too short). But that table is just a flat sheet (actually a Masonite slab door) and vacuum is the only reasonable way of holding down a part. With the pods cut from 3/4" plywood and sealed with some wood glue the 4 pods hold 24" vacuum with my little pump. I also experimented with gasketing tape and found the 3/8 wide and 3/16 thick black Frost King weather strip works best for me. Seals just as well and much easier to use than the expensive gasket tape that needs a groove to be cut.

Extension table with separate vacuum lines.
https://lh4.googleusercontent.com/-yZ7vVTdhJr0/UqUY_nbfWvI/AAAAAAAAEZ8/1Wv6lsqqEj4/w1023-h767-no/DSC02032.JPG

Pods:
https://lh3.googleusercontent.com/-qagmETSW1Po/UqUY-3WhZ_I/AAAAAAAAEZ0/tODdQYQ8iwQ/w1024-h768-no/DSC02031.JPG

I need more space in may shop (i.e. garage). The moving parts of my tools share space with each other....
https://lh5.googleusercontent.com/-yP_jVUShi1U/UqUY-FEQDcI/AAAAAAAAEZs/J2xEZOAGvlw/w1024-h768-no/DSC02030.JPG

[scottp55]

Okay G. , I give up, what the heck is the plywood/roller/bottle? thingamajig in the top right corner of the third pic(it's going to bug me). You definitely need a bigger shop and more"stuff".:)

[Burkhardt]

Okay G. , I give up, what the heck is the plywood/roller/bottle? thingamajig in the top right corner of the third pic(it's going to bug me). You definitely need a bigger shop and more"stuff".:)

Yes it drives me nuts stumbling over tools and materials all the time. Maybe I should tidy up more often or move to another state where space is more affordable.

That thing in the corner is not the warp drive power plant of my shop. It is only my top secret dust collector. That means, what you see is not secret. It is basically a scaled-up version of the Dyson vacuum cleaner with a center main cyclone and 20 gal drum for the chips and debris and a subsequent battery of 12 mini-cyclones for the fine dust (For what it is worth...the mini cyclones are Trader Joe's water bottles). Each mini cyclone has its own home vac size filter bag on the outlet. The secret part is, well, I guess it is secret.

[scottp55]

Yes, does not seem wheelchair friendly, but at least it looks like everything is on casters(I hope). Ah! Makes more sense than an automatic board steamer/bender, or garden path veneer layer/downer. Glad I bought a Desktop and just had to plunk it down, or I'd still be building the retractable base. You certainly like to tinker with materials on hand.:)

[Burkhardt]

Another problem is that I need to work mostly with the garage door open for practical reasons, just to move around the machine. You would think no prob in SoCal and actually it is quite pleasant most of the year. But besides some nights with 90+ degrees in Summer it goes down well into the low 30's right now (got to scrape the ice off the car in the morning) so it is time for a warm jacket and the ear muffs do double duty.

I know I won't get much sympathy from you guys on the East Coast with knee-deep snow and maybe I am a whiner but I guess you are not working a few hours out in the driveway at night.

I also noticed I highjacked my own thread and strayed from the original vacuum setup topic. Oh well.

[genek]

Another problem is that I need to work mostly with the garage door open for practical reasons, just to move around the machine. You would think no prob in SoCal and actually it is quite pleasant most of the year. But besides some nights with 90+ degrees in Summer it goes down well into the low 30's right now (got to scrape the ice off the car in the morning) so it is time for a warm jacket and the ear muffs do double duty.

I know I won't get much sympathy from you guys on the East Coast with knee-deep snow and maybe I am a whiner but I guess you are not working a few hours out in the driveway at night.

I also noticed I highjacked my own thread and strayed from the original vacuum setup topic. Oh well.
get your self a propan space heater,, set it up out side and let it blow hot air into the garage and on you.
I did that for years before I could afford to put a central system in the shop.

[scottp55]

G., What Exactly did you use for materials on your second go around, what did you do different? What vacuum are you pulling? May try in a limited space under Desktop. It is attached to your mobile base, correct? ps played with magnets and plugs yesterday instead of cutting 2 sided maze,will send pics after air-cut and 2X10 spruce trial, thinking walnut.

[Burkhardt]

get your self a propan space heater,, set it up out side and let it blow hot air into the garage and on you....
That is an idea. A bit wasteful of the energy but I will try that. It is nice during the day but so cold at night that the glue does not set properly and laquer takes forever to dry.



G., What Exactly did you use for materials on your second go around, what did you do different? What vacuum are you pulling? .......

I bought a 2x4' sheet of 3/4" PVC for the new end caps but when I had it in my hands I got second thoughts about wasting that expensive stuff on such a simple purpose and put it away for future better use. Instead I used 3/4" Baltic Birch plywood and, glued the tubes in with PU construction adhesive and sealed the plywood surface with thinned Titebond. If it is of any help for you I can send you the Vcarve file for the end caps.
To make it look prettier I sprayed the whole gadget with black truck bed coating (I do that a lot because it covers well, dries rapidly, is abrasion resistant and has some texture to it).

When the valves are closed, the vacuum goes down to 27" Hg that is about as much as the pump will do and means the storage tube are indeed tight. With the pods active, the vacuum depends mostly on the material to clamp. With MDF I can use one or two 5x5" pods, with the Baltic Birch or Bamboo plywood I can get 20-25" Hg vacuum using 4 pods. It depends a bit on how clean the surfaces are and if the gaskets are good or already nicked.

[scottp55]

Thanks G., but I'll do it myself and learn.

[gerryv]

"...they roll the lumber in on a huge rail system into a huge chamber, pull a vacuum down to 29.9 and hold it for 24 hours."

Hi Eugene,
Think maybe a typo slipped by you on the 29.9 in this sentence. Danged grammar check, cut-and paste, and all these other new & improved, automated help features will do it every time (chuckle). NASA would be beating down their doors if this was possible eh!

[scottp55]

2 Products
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Product # HP Amps AC Displacement End Vacuum Max. dBA NPT Inlet Availability Price Qty
36Z455 2 6.9 35.0 cfm 29.9" Hg 67 1-1/4"

Item ships within 8 business days from supplier


$5,207.00 / each



36Z456 5 16.2 71.0 cfm 29.9" Hg 69 1-1/2"

Item ships within 8 business days from supplier


$7,470.00 / each

[genek]

"...they roll the lumber in on a huge rail system into a huge chamber, pull a vacuum down to 29.9 and hold it for 24 hours."

hi eugene,
think maybe a typo slipped by you on the 29.9 in this sentence. Danged grammar check, cut-and paste, and all these other new & improved, automated help features will do it every time (chuckle). Nasa would be beating down their doors if this was possible eh!
no typo 29.9 is the best vacuum that the vacuum pumps will pull.

Check with your local hvac guy he will tell you that is the best.

[ssflyer]

Of course the vacuum you can actually pull relates directly to your altitude...

[genek]

of course the vacuum you can actually pull relates directly to your altitude...
the 29.9 inches of mercury is the best at any altitude. To achieve that the system will have boiled off any water in that system. This is the normal vacuum that a havac tech pulls a/c and heat pumps systems to.

[ssflyer]

Actually, the maximum vacuum you can pull is determined by your elevation, since it is a pressure differential between the volume and the surrounding atmospheric pressure. HERE's (http://www.anver.com/document/vacuum%20lifters/atmospheric%20pressure.htm) a chart illustrating the difference.