Building Vacuum Veneer Press

It’s been years (actually more like two decades) since I last used a vacuum press during my days in a commercial shop. My recollection is that it was a cumbersome and noisy task. Are you familiar with the high-pitched whine of many vacuum pumps?

So a few months back I began investigating bag-clamping systems and became intrigued with those using a compressor and venturi* because they eliminate the need for a vacuum pump. Now, you might say, “Compressors are noisy, too!” Yes, but in using the system I found on the informative Joe Woodworker site, I learned that pairing the venturi with a switch and a tight bag means the compressor hardly cycles on and off at all.

I purchased a system called “Project V2 Plus” from Joe Woodworker’s companion web site VeneerSupplies.com ($159.50). The kit comes with almost everything you need to build the vacuum system you see pictured above; but you’ll spend another $20 or so on hardware-store items including the two capped PVC pipes and the electric switch and box. The bag is sold separately and come in a range of sizes in either polyurethane (more expensive) or vinyl. I purchased a 54″ square poly bag for $174.

OK, the costs are adding up – but when you consider the cost of the typical clamps used to come close to this size clamping capacity, the vacuum system is considerably less. And if you already have a compressor that puts out close to 5 CFM at 80lbs, you don’t need to buy the vacuum pump.  I can further rationalize the cost of the system because I can use it with my lathe as a vacuum chuck, and I can inexpensively build other simple devices and use the vacuum for workholding.

Putting the kit together felt a lot like a small plumbing project, because it involved assembling the various brass fitting and parts, and making the two PVC vacuum storage chambers. It took about three hours to fully assemble the system, and it worked perfectly the first time. I was pleasantly surprised by how well the closure system for the open end of the bag worked. It’s a piece of PVC pipe slightly longer than the bag opening. You simply fold the open end of the bag over the pipe then pop on another piece of plastic (“C” shaped in section) that clamps the bag shut.

So how does it work? With my relatively small compressor, a “sidestack” model rated at 6.2 CFM at 90psi, the bag was completely evacuated in about 50 seconds. The compressor/venturi, cycled only one time as it sucked all the air from the bag. The compressor did not cycle once for the following hour as the vacuum pressure held steady at about 24″ of Hg (mercury) which translates inside the bag to more than 10 lbs of pressure per square inch.

With this new-to-me technology in the shop, I’m beginning to think about more than making my own custom veneer panels. I mentioned the uses for the lathe and workholding, but I’m also now thinking a lot more about forming curved parts using bent lamination techniques with the vacuum bag used as the clamping method.

– Steve Shanesy

*In the 18th century, Giovanni Battista Venturi discovered that when compressed air is forced through a restrictive nozzle, its velocity increases and the air is compressed and when it exits the nozzle, it expands and has the ability creates vacuum. From the Joe Woodworker web site.

• Learn more about veneering in Johnathan Benson’s book “Woodworker’s Guide to Veneering & Inlay” – and look for my video in late October.

13 thoughts on “Building Vacuum Veneer Press

  1. chucksdust

    Steve,
    Thanks for the great post, I look forward to the DVD. One quick question, what kind of compressor are you using with this? It seems almost double what my “smallish” unit will pull, 3SCFM at 90psi?
    Charlie

    1. Steve ShanesySteve Shanesy Post author

      Hi, Charlie,
      My compressor is a Porter/Cable Sidestack model CF2400. It’s probably 10-years-old, maybe more. It’s 2 hp, 6.1cfm at 90psi with tank capacity of 4 gal. I’m investigating just how small a compressor can be used with this system and not strain anything. Will advise.

  2. Steve_OH

    The last time I used a venturi vacuum pump (a very long time ago, as a postdoc doing physics research), it was shriekingly loud, even with the muffler in place. How loud is the one in the kit?

    You can also get a venturi pump that works with water rather than compressed air. It’s pretty quiet, but it does consume a lot of water, of course.

    -Steve

    1. Steve ShanesySteve Shanesy Post author

      Steve,
      I’m not using a vacuum pump at all. Just the compressor with the vacuum generating venturi. Once the air is evacuated from the bag (less than a minute), there’s no sound at all from the system or compressor.

      1. Steve_OH

        The venturi IS a vacuum pump, albeit one in which the only moving part is air. Obviously, there is no noise when the system isn’t running. The question is how much noise there is when the system IS running, from the air rushing through the venturi. THAT is what I found to be unbearably loud.

        -Steve

  3. Steve ShanesySteve Shanesy Post author

    Al, you are 100% correct and I’ve updated the post. Thanks. And why is it we don’t listen to those little niggling sensations that question something, as I did when I wrote the post and put that number in. I stopped and though about it for a few seconds and moved on. Got to pay attention to those first instincts. They are so often right.

  4. Al Navas

    Steve,

    Assuming you are at about 800 ft. above sea level, like we are in NW Missouri, I believe the vacuum you can pull at the shop in Cincinnati is equivalent to around 1,500 to 1,600 lbs per square foot. This translates to 10.4-11.1 pounds per square inch. Maybe the math is off a tad?

    For this calculation I assume around a ton per square foot at sea level.

    Al

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