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:


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.

[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

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.