Cheap Vacuum Clamps

[tonyb]

Just thought I'd post a note to let you guys know that I've just ordered a couple of vacuum hold downs from Vac-Clamps. They cost me $110.00 each Asutralian (about $65.00 US) and I've done a bit of research and they seem more than adequate. If you want to have a look there web site is
www.vac-clamp.com

[jay_mack1@hotmail.com]

Okay,

Guys, if you look at this, its a pretty simple setup. I'd like to find the science behind this little vacumn clamp. Its got to be pretty simple, were taking compressed air, running it past a Smaller? opening, which created negative pressure as it pass creating vacumn? Am I correct in my thinking. If anyone knows where I can find more information on the science of this process I'd appreciate it.

Thanks!

[ckurak]

I believe it is called the Bernoulli effect.

[ssmith@skeeball.com]

Check this out. Look under how does it work. Not as simple as it seems.
http://www.vaccon.com/cartridges.html

[tonyb]

I should get them middle of next week, so I will give them a go and will give an unbiased apraisile. To use only 1 CFM the venturi must be tiny, I'm wondering if there will be a noise issue.
If they work as I'm as good as I'm led to believe then I'm going to deck my Bot out with 4 or maybe 6 of them.

[tonyb]

I received the Vac Clamps today and just spent a few minutes having a play with them. What I did was to screw one down to the ShopBot then I put on a 18mm piece of MDF. Then I wrote a quick program which machined a 35mm diameter circle at 5mm deep, then a 45mm circle 10mm deep, then a 55mm circle 15mm deep. I ran the machine at 60mm Per second and used a 12.7 single bladed insert cutter.

The fist circle was no problem at 5mm deep, the second circle started to sound a bit cattery at 10mm deep and it couldn’t hold the MDF at 15mm.

Then I slowed the machine down to 30mm Per Second. The first 2 cuts were fine and the last at 15mm was quite cattery but the timber held.

After this I set up the second Vac Clamp next to the first and put a piece of MDF spaning both. All thee circles cut well although I think that the 15mm cut still sounded a bit cattery even though it looks and feels OK.

That’s all I’ve had time to do at present, I’ll have a bit more of a play tomorrow. The movement that causes the chattering seems to be a result of the movement within the sealing rubber. The hold down power is superb I need to try and eliminate the roll in the rubber.

[gerald_d]

Wonder if Vac Clamps borrowed the idea from this thread (http://www.talkshopbot.com/forum/messages/28/466.html?)?


Still think that a SB would be perfect for routing out channels and making your own "Vac Clamp". You would just have to buy a pretty common vacuum pump (venturi type) from one of these places (http://www.google.co.uk/search?sourceid=navclient&q=vacuum%2Bpump%2Bsuctio n%2Bcup).

[kerrazy]

Ok so can you use an AC vac pump?
Dale

[gerald_d]

Dale,

Alternating Current, Air Conditioner? A very cryptic ques!

Cryptic answer: Yes.

Longer answer: Yes, for what an "AC" vac pump is designed to do. But for vacuum hold-down . . . . I havn't the foggiest idea of what you are talking about!

[kerrazy]

Gerald, Gerald, Gerald, shouldn't you be in bed?

Air Conditioning my good man.

[gerald_d]

At 3 in the afternoon? There was an edit above.

[kerrazy]

What you don't nap in SA?

[gerald_d]

We nap in the boss's time - not in our beds.

[tonyb]

If you can just buy the Vac Pump from that link that was posted by Scott Smith above then it wouldn't be hard to make a vacuum set-up. The problem as of last night wasn't the hold down power, but not enough vacuum to hold the board to the faceplate, i.e. slight movement in the rubber.
Has anyone felt the vacuum from the inlet of their compressor? I’m going to check that out this morning when the neighbours wake up
Tony

[jay]

Tony, we asked our local compressor dealer about using a compressor for a vacuum hold down source. He said if we did try it the only thing we would suck is all the oil out of the compressor. So we figured we would go to one of the air conditioning specialists and aquire an old industrial freezer pump. Same problem. We would told we would suck the oil out of it and destroy the pump.

[jeff]

Hi Jay

Here is something I posted a while ago
"I just finished setting up my vacuum table using an old discarded air conditioner pump and it works like a charm. One could use a refrigerator pump also. So if you are looking for a cheap vacuum table that is really quiet give it a try.
Remember not to tip it over or all the oil will spill out(I bolted mine down to a small plywood sheet) and the very first time you turn it on, it will spatter a little oil so make sure its not anywhere that you cannot easily clean it up. "


Find yourself an old AC unit and give it a try,I used a 13500Btu and closed cell chalking filler availiable at any home center.

Your Ac specialist doesnt understand. My Father use to work in the railway shops where they used the same small Ac compressor to pull vacumm for 9 years running it sometime for more that a week at a time 24 hours per day.
give it a try with scrap unit and you will see for yourself

Your Thai restaurant eating buddy LOL

Jeff

[tonyb]

Ha
Jay guess what' I learned the hard way yesterday. Didn't do any damage but i smelt the oil. Must check the level come to think of it.
I also got my Vac-Clamps and posistioned them about 200mm apart. Solid as rock.On the WEB-SITE there is a photo showing a timber part being held by 1 Vac-Clamp and being machined by a CNC, but the feed rate only works out to be 15mm/per/second. Which I'm sure would work fine, but in my opion that just to slow. Any faster with a depth over 10mm and the job becomes chattery to disaterous, but put 2 next to each other and it's fine So now I have to workout away to make the whole thing workable.I don't want to add any height to the bed. I'm thinking that I would need at least 7 vacuum points on the CNC, but maybe it could be done by having one Vac-Clamp under a sheet of MDF operating 2 or 3 vacuum points.
Louise (my wife) wants one embedded into a sanding table.

[jay]

Hello Jeff, thanks for your post. We have a couple of old large freezer compressors kicking about, if the Vacuum pump I pick up over the weekend, at the University does not do the job, I will give one of the compressors a try.

PS. The restaurant was Lybian.

[gerald_d]

Aside from sucking out the oil when you use some compressors as a vacuum pumps, you must also watch for overheating. Refrigeration/AC compressors normally receive a stream of cold freon. If your Vac-Clamp has no leaks, your home-made pump will receive nothing to cool it.

[jeff]

Gerald,I find that my ac compressor barely leaks any oil, maybe a small drop per hour and I catch it in a small empty plastic bottle that sits on the floor, when it fills to more than an inch (a few mm.)I just move it back to the intake tube and let the machine suck the oil back in, then its good for another 60 hours or so. As for overheating sure it gets hot but not any hotter than if it was cooling freon at 35C and if that was a major concern one could use a reserve tank
similar to a regular air compressor or larger and put a couple shut off valves for those leak-free setups.This solution works great holding small parts, but less so for full sheets, but I havent bothered to make a proper setup for this like Bill P's table which would most likely work well.

Jay give it a try, used compressors are generally free and my total cost for this came out to less than $10.00 for some tubing, compression fittings and a valve.

Jeff

[gerald_d]

Lest someone get the wrong impression.....

I am all for experimentation and finding the lowest cost option. I am simply stating the reasons why SOME compressors/pumps are not suitable for vacuum use. There are thousands of different types out and I am careful to not make a sweeping statement that any old "AC pump" will work for you.

[jeff]

Fair enough Gerald, I agree with you that it is likely so that one make is not the same as another,just for the record the Ac unit that I used was from an old "Carrier" circa 1978.

Best regards

Jeff

[pappy]

I use a pump from an old freon recycling machine (it will pull 30 inches of mercury) and it works well. I have an old freon tank inline with it, so that when I open the valve it gives me more instant "suck".

[sales@vac-clamp.com]

Hello From Vac-Clamp
I thought it best to enter this forum and maybe add our two cents worth.
We have been developing the Vac-Clamps for about two years to iron our most of the bugs and hassles associated with a venturi based vacuum system in a dusty environment. What you see on the website ( http://www.vac-clamp.com ) is the culmination of that work.
The clamps have no moving parts, so there is nothing to wear out. They tolerate being buried in dust and wood shavings without getting upset.
they use about 1cfm of air and provide a reliable holding force of about 800 grams per square centimtre (12 pounds per square inch)
Why is it better?
-No moving parts to wear out
-Tolerant of dust and rubbish being ingested
-Holding force about 8 times that of a vacuum cleaner setup.
-Face can be badly damaged but can still work.

If you would like more info email me sales@vac-clamp.com

[Gerald]

Errol, surely there are moving parts and wear & tear on the compressor that supplies the compressed air to the vac-clamp?

[sales@vac-clamp.com]

Vac-Clamps run on compressed air provided by ANY compressor. You use them as you would any air tool.
The clamps are completely self contained apart from the compressed air supply requirement. Air regulation and vacuum generation occur within the clamp.

There is one wear item and that is the replaceable rubber seal.

[mrdovey]

I'll add my 2d worth... I've been using the compressor from a discarded refrigerator for about four months now. I bought a 3/4" x 4" x 48" piece of UHMWPE and cut it into 4" squares (I call 'em "pucks" for lack of a better name), drilled 5/8" all the way through the center of the large faces, and drilled 3/8" from opposed edges to the center 5/8" hole. Bought 3/16" closed cell foam weatherstripping and built a "wall" at the perimeter of the large faces (top and bottom). Bought ball cabinet door catches and force fitted them into the (top side only) center holes.

Then I bought some inexpensive 3/8" OD (1/4" ID) plastic tubing and used it to connect the vacuum side of the compressor to one of my pucks (and plugged the unused hole in the puck with a dowel), put it on my ShopBot table and powered up the compressor. I couldn't move it. Dropped a 6" square of plywood on top and pressed it down until the spring loaded ball in the cabinet catch allowed vacuum to the top surface. I couldn't slide the plywood; but did manage to (finally) pry it off.

So I cut four short lengths of tubing and made a "daisy chain" of 5 pucks. Lined 'em up and pressed a 1" x 6" x 6' piece of pine down - and routed a series of 70 individual cuts in the pine (no through cuts) - twice, to see if the board had shifted at any point. The result was slick and indistinguishable from a single cutting pass. I've been using it ever since.

Since the last puck in the chain always needed to have one hole plugged, I made a "terminal" puck that doesn't need any plugging; and I made a couple of "T" pucks so that my hold down system could have branches.

Component costs (US$):

o 30.00 - 3/4" x 4" x 48" UHMWPE (Made 12 pucks)
o 1.79 - Weather Stripping (17')
o 6.00 - Brass ball catches (12 ea)
o 15.00 - Plastic tubing (100')

I found that a set of 4-1/16" squares cut out of a piece of 1/8" hardboard makes a good "template" for ensuring that the pucks are always in the same place for a particular part. This helps me avoid damaging the pucks on through cuts.

I've bent the discharge tube from the compressor so that it blows at the bottom of the dome-shaped housing from about 2" away to provide some additional cooling. I don't know if the cooling is needed; or if my "blow tube" helps any. But if/when the compressor dies, I don't think I'll have any difficulty finding another at the same price. :-)

[Jeff B]

Sounds very similar to my set up,also free
,
One thing I would like to know is what is uhmwpe
and were do I find it?
Thanks
Jeff

[jay]

I also would like to know is what is uhmwpe
and were do I find it?
Thanks, Jay

[gerald_d]

uhmwpe is a fancy way of spelling plastic

[Mayo]

Technically speaking, I believe the product referred to is Ultra High Molecular Weight PolyEthylene.

I occasionally buy stuff they call (on the invoice) HDPE which is High Density PolyEthylene.

I have no idea what the difference is between UHMWPE and HDPE (if any) but I do know that the HDPE is used as cutting board material, among other things.

[johnandrhondawebb@netzero.net]

This sounds like a source for the rectangular stock UHMWPE: K-mac-plastics (http://k-mac-plastics.net/uhmwpe-square-rectangle-bar-stock.htm). Hey Morris, do you have a pic or sketch of your system?... Was thinking I'd be springing for some Vac-Clamps, but if your idea works like I think it does, I'd rather save the dough & have more to show. They've got 5 foot lengths of UHMWPE upto 1.5" thick by 6" wide. How did you determine what dimensions would work best for max suction on each puck? How did you "cap" the ends of each square you cut off the 48" stick- to make it air tight before drilling the holes? - Any feedback much appreciated - John

[barrowj]

I would be very interested in getting more info on your setup also mrdovey. It sounds like just what i have been looking for. - Joe

[johnandrhondawebb@netzero.net]

Whoops... looks like K-mac requires a min. $100 order

[gerald_d]

Seriously guys, for this application, practically any old solid plastic would do. You don't have to bother with the highly technical descriptions.

[Ron Brown]

Try looking on EBay for chunks of plastic.

[gerald_d]

Take chunks of wood (or mdf) and seal them to behave like plastic. . . . . . .

[billp]

OR, look at Shobot's web page for pictures of this year's New Jersey Camp Shopbot. You'll see how Bill Imschwieler made his "puck" setup out of the latest generation of MDF ("Extirra" which is a waterproof variety of the stuff..). As Gerald has suggested, it does NOT have to be anything of the "high tech/expensive" variety to work well.

[sheldon@dingwallguitars.com]

UHMW is one of the more affordable plastics.

[mrdovey]

Darn! (I can't edit my article.)

I woke up this morning realizing that I'd gotten the hole sizes wrong. The center through hole was 5/16" and the holes from the edges to the center hole are 1/4", with the outer 1" re-bored to 3/8". Sorry.

UHMWPE is u;tra high molecular weight polyethylene (and it looks and feels much like the cutting board material.) I would guess that the kind of plastic chosen wouldn't make much difference, so long as it can be sawn and drilled.

Holding power seems to be related to the area of clamped material exposed to the vacuum. I picked the 4" x 4" size because that would determine the smallest workpiece size that I might be tempted to clamp. Pretty scientific, huh?

I picked the 3/4" thickness because that was all they had in the store across the street. It seems to be a good thickness, because after drilling a 3/8" hole in the edge there's 3/16" of material left above and below the cavity. In use the puck robs me of slightly more than 3/4" of z travel - I don't think I could gain much by making it thinner or thicker.

My local building supply store had sturdy-looking 3/8" OD clear plastic tubing (probably intended for connecting icemakers) for cheap. The 1/4" ID matched up with the 1/4" hole in the puck; and I guessed that a 1/4" opening wouldn't restrict air flow anywhere. As you can see, I really pulled out all the scientific high-tech stops for this project. 8-)

The ball catches allow me to stick the pucks to the table without a workpiece in place. They were suggested by a friend who had a bagful and was willing to sell me a handful at 2/$ (his price). The diameter of the ball catch determined the diameter of the puck's center hole.

FWIW, I considered making the pucks out of MDF or wood and sealing them. (I re-considered carefully when I saw the price tag on the UHMWPE!) I decided to spend on the plastic because I wanted dimensional stability, workability, and more durability than I thought I might get from MDF or wood. I was so pleased with the result that I went back and got two more pieces of the stuff for terminal- and T-pucks; and to build some larger, specially shaped pucks.

I'll try to remember to take some pictures when I get to the shop. I should probably fire up my "drafting board" and make drawings as well. I'll post whatever I can tonight or tomorrow.

Morris Dovey

[mrdovey]

Took pictures of my vacuum setup - and can't find the camera-to-PC cable. Here's a drawing instead:


Morris

[mrdovey]

Not my day. I can't seem to upload the jpg image.

Morris

[mrdovey]

One more time to see if I'm getting the hang of it. Here's the drawing:

5405

Morris

[mrdovey]

Carol (my brighter half) just suggested that I offer both materials kits and ready-to-use puck kits (everything except the compressor/pump) to make vacuum clamping easy. I'll offer a set of eight pucks - seven daisy chain and one terminator. If anyone's interested, contact me by e-mail.

Morris

[stevem]

For all of you trying to make your own vacuum pucks, the type of plastic makes a huge difference if you’re trying to cut, drill or machine it. HDPE can turn into goo if routed too slowly or with a dull cutter and is difficult to cut with a band saw. UHMWPE is much better for routing and is only slightly more expensive. StarBoard is a type of HDPE that is UV stabilised and is easy to machine but is more expensive than HDPE .Delrin (Acetal) is better still, but much more expensive

[jay_mack1@hotmail.com]

Have you guys checked out this site, they have lots of plastics and such!

Us Plastics (www.usplastic.com)

[jay_mack1@hotmail.com]

Have you guys checked out this site, they have lots of plastics and such!

US Plastics (http//www.usplastic.com)

[jay_mack1@hotmail.com]

Okay it doesn't work - www.usplastic.com

[mrdovey]

For those interested in building a puck type clamping system, I've put up a web page at assembly instructions (http://www.iedu.com/ShopBot/Vacuum/Assembly.html) that might be helpful.

I've also located a limited supply of (used) smallish refrigeration compressors that can be used for small (1 - 4) puck clamping systems. They aren't free ($50 + shipping) but they're available.

Send me an e-mail if you're interested.

[mrdovey]

I'm in the process of remodeling my web site. All of my ShopBot-related stuff can be accessed at the DeSoto Solar Home Page (http://www.iedu.com/DeSoto). I'll be adding pictures to the assembly instructions as soon as my camera arrives (supposed to be here yesterday. )-:

Morris

[grant@shopbottools.com]

I just checked out your site, Morris. It looks like you have been working on some really cool projects! Can't wait to see your pictures.

Grant

[mrdovey]

Grant,

The first of the pictures have been added to the web pages. I'll add more as I get feedback about what people find interesting. I'm still working to learn how to use the camera.

If anyone has preferences as to resolution of images, I'd appreciate feedback. I can provide up to 2560 x 1920 x 16M colors, which seems cumbersome for web pages - smaller will be better; and the question is: "how much smaller?"

Morris

[Mayo]

Typically, resolution for web images only needs to be from 75 DPI to 96 DPI. To keep your file size low, you would also want to convert the color (adjusted in a photo editing software) to 256 colors. Anything more and you will unnecessarily increase load times for the pictures.

It's been said that higher DPI in images online will not give any noticeable difference. This has something to do with the pixels in computer screens and the distance apart they are. I have no idea if this is also true with plasma screens or LCD screens...

Higher DPI and more than 256 colors is advantageous when printing the image.

[johnandrhondawebb@netzero.net]

Hi Morris,

Standard web resolution is 72dpi. Palette reduction from 24bit to 256 or 8bit color will cause banding in photos (especially gradients), but for solid form illustrations or lines it works fine. Use jpeg file format for photographic images & set compression to 1/5 (preserves most quality & creates purdy small filesizes), with 0 smoothing if you have that option. In Corel PhotoPaint, the jpeg compression scale goes from 0 to 100 with 100 being totally compressed. In Photoshop, the scale is reversed. It's a jpeg quality scale from 1-10 with higher numbers meaning more quality, less compression. In PhotoPaint, I set compression to 20 usually, unless I need to really pack it down & don't care about quality. For web browser viewable stills, I stick to the following filetypes:

jpeg- (24 bit, 1.67+ mil. colors, lossy) for photos, excellent compression, small filesizes, lossy though, meaning once compressed you can't restore the file to it's original quality. Repetitive saves on the same image contintue to degrade the image. Produces "artifacts" or pixelization around high contrast/edge zones - can kill detailed textures/patterns when high compression is used.

gif- (8 bit/256 color, palette reduction) for illustrations, line/shape drawings with minimal gradients or textures, excellent compression, plus you can save animated gifs. If you start with 24bit content, you have to reduce your palette to 8bit before saving this filetype. This reduction is what makes this format lossy as well, although repetitive saves after the 8bit reduction will not degrade the image any further. This is not a factor if you design using an 8bit palette to start with.

png- (24bit, 1.67+ mil. colors, compressed, lossless) Good for maintaing original palette with maximum quality. Does not require palette reduction. Does not compress as well as jpeg/gif, but is perfect for preserving all of the original quality of the 24bit source image.

Then there's movie filetypes... but we won't go there.

As for your description pages, you may want to use thumbnails with clickthroughs to the higher resolution stuff. Pages load fast, yet user gets a graphic idea of content. I typically would use a thumbnail size of 120x90 pixels with a clickthrough to 640x480 images, & finally a text link to the high res version for printing. I then advise user to "Right Click" the text link & "Save Target As" to save the high res. version to disk, so that the browser doesn't interpret the 300dpi image as 72dpi (huge image when printed) or scale the image down to fit(tossing detail). Printing standard is 300dpi.

Here's some examples of some thumbnail clickthroughs... You'll note this page is slow cuz of excessive graphics at head/foot. It's on the board for re-design...
examples (http://www.intelliweather.com/imagesuite_satellite.htm)

If you have any ?'s, email'm - John

[mrdovey]

Thanks - good, usable info! I'd promised a number of people that I'd make pictures available, then discovered that I didn't really know how to do that very well. /-: As I learn to use the digital camera (and as the shop becomes better organized and better lighted) I'll want to post some better pictures than I have so far.

I'm shooting with a Nikon Coolpix 5700 and processing the images with a back-level version of Paintshop Pro. I used to do a fair amount of photo work with film cameras; but this is a whole new game to me. The camera seems to be (at least photographically) smarter than I am - and the challenge for me is to learn to take advantage of all those "smarts". Takes time and effort. I don't mind the effort; but time has been in short supply.

I've also been working on an SB dovetail jig and software; and will definitely want to post a series of "how-to" pictures for that. Sometimes prose just isn't enough; and this would seem to be one of those times. The info you've provided will help a lot - I appreciate it.

Morris

[dmidkiff]

I made some of the vacuum pucks today and tried hooking them up to a refrigerator compressor. I had suction but not enough to use even one puck. I made the pucks from mdf and sealed them good and the refrigerator was a small one. What sugestions does anyone have to make this work. I would like to have 20 to 24 pucks. Is this even possible? Thanks for your response

[mrdovey]

Dave...

I've been using shop made vacuum pucks for nearly all of my clamping since this fall. The most I've ever used at one time was seven (and backed off to five for that job because seven was huge overkill), so I know that this should be doing a better job than you report.

I tested using even a (very small) water cooler compressor and had better results than you're reporting - it just took a lot longer for the compressor to evacuate the air from the system.

Questions:
* How large are your pucks?
* Are you using closed-cell foam weatherstripping to seal the puck to table and workpiece?
* How large is your workpiece?
* Are you using any kind of a valve on the top side of the puck, and if so, have you checked to be certain that it's opening properly when you press down on a workpiece? One way to check this is to remove the valve and see if your puck performs better with the valve removed.
* Have you connected to the vacuum (intake) side of the compressor?
* Is there any obstruction or blockage on the exhaust side of the compressor?
* Are all tubing and seal connections vacuum tight?

Morris

[ron brown]

And there are a dozen more little factors you might have added Morris. Even the mild 15" of Hg(mercury) pulls air through most wood. I know it takes three careful layers of good epoxy to seal mahogany. And, if it has to be really "Vacuum Tight" even that takes patching to make it truely sealed.

If you are using the bed as one side, is it sealed? The small compressors used as vacuum pumps have very little volume. Can you attach a gauge to find what vacuum is actually pulling on the piece?

I wouldn't give up on vacuum clamping. But I would figure out what was failing to perform and why. I decided for my purposes, I preferred high volume and low pressures for 98% of what I did.

Ron

[mrdovey]

Ron...

One side of my clamps "mate" to my routed MDF table surface - which I suspect is fairly porus. I've been vacuum clamping tempered hardboard, luan plywood, well-planed pine, and plain ol' construction grade fir and spruce - with two to five pucks per workpiece and no problems. My vacuum pump is the compressor from an /old/ Fedders refrigerator that happened to be the first available.

I tried a really tiny used compressor from a water cooler and it worked considerably better than what Dave has described although it lacked the volume capacity as you described. This resulted in a longer evacuation time and a considerably lessened ability to deal with the more porus surfaces. It did best, unsurprisingly, with tempered hardboard, plywood, and select pine workpices clamped to my "leaky" MDF table top.

From a practical standpoint, there isn't much that can be done to reduce porosity of the work; but integrity of the clamping system is a prerequisite to clamping even the most non-porus of surfaces.

When I read Dave's post my first guesses were that he's either recycling a truly dead compressor or is using an open-cell foam seal. He really should be seeing much better results.

Morris

[dmidkiff]

Morris
My pucks are 4" X 4" and the weatherstripping looks like the pictures from your website. I did use a bullet catch and they seem to work like they should.
The compressor came from a working frig just yesterday. I put he tubing on the suction copper and let the exhaust just flow out. No luck. I made a complete circuit with thee air flow and still nothing. Then I closed the exhaust as goog as I could and still nothing. I should not say nothing because there was air movement but would not hold the puck to the table or a small 5" mdf to the puck.
Ron
I sealed table and the pucks with three coats of lacquer. I will be able to make a trip to the hardware store today to find some clamps for the leaking exhaust. I think I have a vacuum gauge if I can find it.
Thanks again

[mrdovey]

Dave...

The exhaust side of the compressor *needs* to be OPEN.

The compressor is sucking air in at one tube - and it needs to be able to expell it from the exhaust tube.

Morris

[mrdovey]

Dave...

Look at http://www.iedu.com/DeSoto/pix/sb_r.gif - this compressor has four copper tubes (some have only two) and the tube with the strongest suction is used to suck the air from the vacuum pucks via the clear tubing. I have a piece of Kleenex rubber-banded (loosely) over the exhaust tube to collect any oil that might otherwise make a mess.

See http://www.iedu.com/DeSoto/pix/reg_rail.gif for a view of the puck "daisy chain" from the other end of the table. The last puck in the chain has only one hole for tubing in order to prevent air from leaking into the system.

The object here is to use the compressor to suck all the air out of the clamps (and from the spaces between the clamps and the table; and from the spaces between the clamps and the workpiece).

If you're working with a single puck - which is a good starting point - make sure it's only got one hole for tubing. If it has two, then plug the second hole (I inserted a short piece of tubing into which I inserted a piece of 1/4" dowel)

Morris

[Brady Watson]

I have found that the ShopVac works better than the little pucks and a good vacuum pump. I have a Gast pump and a few pucks that I tried out on the machine. In my experience, the ShopVac (with high volume/low vac) works better than the vacuum pump on WOOD any day of the week. The ONLY time that the vacuum pump appeared to do better was cutting a non-porous material like lucite, that was less than 6" square in size.

For most of us, the ShopVac will do 95% of what we need a vacuum clamp for. For me, the pucks are a pain in the butt to deal with and more trouble than they are worth. I would rather take a $9 piece of luann plywood, cut out where my pieces go and put it on top of the table vacuum grid. I know that it will definately work...every time.

If I can't use vacuum, I'll just tab them. The pucks look neat, but in my experience they aren't worth the aggrivation and time messing with them.

Just my .02,
Brady

[mrdovey]

Brady...

Interesting. I've been using the puck setup to hold primarily 1"x6"x6' select pine and oak and 2"x6"x6' construction grade fir and spruce for dado and mortise-and-tenon cutting for solar panel frames.

I've liked the pucks better than mechanical clamps because of the quick, hassle-free setup and reconfiguration and, of course, because I can machine all five exposed sides of the workpiece in a single operation.

I would guess that it all depends on the particular task and setup requirements for the operation. I'm glad the ShopVac approach works for you and I'm pleased with how well the puck approach has been working for me.

Morris

[Brady Watson]

Hey Morris,
How big are the pucks? THey look a bit bigger than the ones I used...That might have something to do with it.

[mrdovey]

Brady...

I'm using 4"x4" pucks cut from 3/4" UHMWPE. There's a description at http://www.iedu.com/DeSoto/vacuum.html and a drawing and close-up photos at http://www.iedu.com/DeSoto/assembly.html

They've worked so well for me that I'm baffled by your unsatisfying experiences. The only thing I can imagine is that the difference must be in the kind of workpieces we're clamping...

Morris

[Jeff B (Unregistered Guest)]

Dave

Try this to see if your pump is able to draw adaquate vacuum.
Take 2 pieces of scrap 12 x 12 plywood, drill a hole threw the center of one that is just a little smaller than the fitting that connects to your vacuums suction tube.
Screw the fitting into the hole then turn on your compressor. take a piece of your closed cell tubing and make a 8 in. diameter tape the end together with masking tape. place the other board over the 1st board with the 8 in circle in between to form a sandwich and watch out that your fingers are not inbetween. this should quickly seal the 2 boards together. if after a couple of seconds you can still pull the boards apart your compresser is garbage if not your problem is with your set up .

Hope this helps

[kerrazy]

I just recently purchased and recieved today Big Mach vacuum system from Eagle-America out of Ohio. The kit sells for $69.00 USD and contains vac tape, bullet catches (similar to morris's design as well a shut off valve. I have it half biult and really hope when paired up with a fein vac it will do the job.
By the way if you could all join in singing Happy Birthday to my shopBot, I have officially had it for one year. And it has paid for itself Yeah!!!

Dale

The info on the mach is at this site http://www.m-powertools.com/products/big-mach/big-mach.htm

[Brady Watson]

Hey Dale...Does the Big Mach come with fries?


Congrats on your 1yr.

-Brady

[mrdovey]

Dale...

Happy Birthday to you and your 'Bot. Well done!

M-Power seems to make good stuff. I bought their point-2-point layout tool a while back and it's been /very/ handy. Am still waiting for introduction of their scaled-up version.

Let us know how you like the Big Mach when you've had a chance to test it.

Morris

[kerrazy]

Brady,
Atkins diet ...No fries...LOL

[Jeff B (Unregistered Guest)]

Hey Dale

Happy BOTDAY to you and many more....

Jeff

[dmidkiff]

Jeff,
I found that it was my setup. The pump makes 28Hg and holds for a while. Am changing the foam and will know more later today.
Thanks
Dale,
Happy Birthday Try South Beach Fries are better than baked!!!
Dave

[sales@vac-clamp.com]

Hello from Vac-Clamp again,
I have been reading with interest the many ways that have been used to hold a workpiece to enable cutting a workpiece. It may well be worth your while to have a look at http://www.vac-clamp.com
We have a new clamp coming out in April (the VC4) which will sell for about USD$51.00 which may solve a number of issues.
All of the clamps work by venturi effect. The venturi is within the unit itself so it is completely self contained. It also means that the clamps work independently of one another.
Any normal air compressor will power the clamps effectively.
All of the clamps produce a vacuum to about 88% of absolute (about -12psi)
Best Regards
Errol Weber
(Vac-Clamp)