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Thread: New vacuum bagging setup?

  1. #1
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    New vacuum bagging setup?

    Pneumatic or vacuum pump? Veneersupplies.com seems to be one of the main suppliers for turnkey vacuum systems. Their low/mid range venturi and pump systems are roughly comparable in price. I have a big 5HP 80 gallon compressor so I have plenty of air. How much should I expect the compressor to cycle on and off while maintaining the vacuum, assuming good bags and seals? A little vacuum pump would use a lot less power than the air compressor, even if it did run more.

  2. #2
    Quote Originally Posted by Dave Cav View Post
    Pneumatic or vacuum pump? Veneersupplies.com seems to be one of the main suppliers for turnkey vacuum systems. Their low/mid range venturi and pump systems are roughly comparable in price. I have a big 5HP 80 gallon compressor so I have plenty of air. How much should I expect the compressor to cycle on and off while maintaining the vacuum, assuming good bags and seals? A little vacuum pump would use a lot less power than the air compressor, even if it did run more.
    I don't know if you've looked at other options already, but I bought the Compact 300 from Vacupress and it works beautifully. Plenty of power for even a 4' x 8' bag. Automatically monitors pressure in the bag and cycles on as needed. Much quieter than any compressor. Would definitely recommend.

  3. #3
    Join Date
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    I bought a used Gast Vacuum pump, off eBay, about $50. I used it wish a 4' x 8' bag from veneerSupplies.com. You don't need much of a vacuum pump to suck the air out of a large bag and once most of the air is out of the bag, the atmosphere outside the bag is doing most of the job for you.

    No way would I use my old, super noisy compressor as a venturi pump.

    I also have a cheap AC Vacuum pump (Amazon) that I use on my wood lathe when I'm finishing the base of bowls. Links in the YouTube description


  4. #4
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    One issue with a venturi is that the cfm is pretty low. But that can be overcome by using a shop vac to remove a lot of air from the bag, and then hooking up the venturi. You need a venturi system that has an automatic cycling valve or else the venturi uses air constantly. Most venturi air consumption is about the same as cutting the end off a hose. Wide open in other words.

  5. #5
    Hybrid of all the above, plus a word of warning.
    I 've used an air operated (venturi) from vacu-press for over 15 years now. My compressor is in a closet under the stairs, so it doesn't blow me out of shop with noise, but I do notice it cycling when pump starts. Realize, once the bag is drawn down to appropriate Hg, as long as low to no air leaks, it can go 30-45 minutes before venturi cycles on with an optimal seal. Note, when it does this, its a 1-5 second sip of air to maintain target amount of vacuum. This means little to no air used = no running compressor. It's just that initial evacuation that dumps the most air. Like Richard, I discovered a while ago, when using a large bag with lots of air to remove, use your shop-vac for a quick pull down. Switch back to vac line and pump does the rest.

    Manifold- Once you get rolling, you may find running multiple bags is a great stride towards efficiency. Once bag 1 is loaded and drawn down, you switch it's valve off to lock temporarily, then load/pull down bag 2. At that point, re-open bag 1 and you're all set. Again, same venturi system 15+ years handles this activity with no problems and no excessive compressor running.

    I've also tried the gast-style electric pump, but bought a cheapie. It used oil for lube. Took a few hours to realize what was going on, but it basically fogged the entire shop with a fine mist of oil.
    Yep - it went into the trash, and I've never wasted any more time trying an electric vac pump. Venturi is solid and works fine for me, though you'll want an oil-less electric vac pump if you desire to use vacuum pucks and the like, or you're running constant air flow and taxing the heck out of the compressor.
    Again, strictly speaking for vacuum bag work, nothing wrong with the venturi at all. Just be sure to invest in a system that is auto-cycling to keep things regulated.

    BTW- I still find vacuum to be one of the most fun "tools" in the shop. So many uses. No matter your choice, you won't want to ever be without, once you start.

    Good luck,

    Jeff

  6. #6
    On the topic of bags - Don't get too wrapped up on the polyurethane hype. Won't mention which vendor, but I'd placed a less than stellar review and got squelched fast.
    Had made a table top frame with it, as well as buying a 4x8 conventional bag. Leaks, leaks, leaks. Vendor said it was my fault, as it was left folded on a shelf in a room that had florescent lighting.
    He explained that the polyurethane material breaks down when exposed to sunlight or florescent lighting. You must get your project done and put the bag in a sealed, light-tight storage container as soon as possible. Great vendor, as he replaced the product (which now, a few years later is leaking like a sieve too) but disturbing, as this is the first time I've been able to relay this experience on an open forum.

    My experience indicates polyurethane is unnecessary, having gone through at least 6-7 different size bags of both vinyl and polyurethane over the years. The price difference is far beyond justifiable (unless you want to veneer a baseball, as they like to show in demo images). 20-30mil vinyl bags can be replaced in regular intervals, spaced much further apart than any polyurethane products, for a fraction of the cost.

    Jeff

  7. #7
    I have been considering getting a vacuum setup for veneering too. As an alternative, I wonder if eBay or craigslist has any older used presses that use the force of the press instead of a vacuum setup? I have bought a lot of old iron and seems like I might come across presses from time to time. They take up a lot of space though.

  8. #8
    Vacuum is just so much more versatile. allowing for laminating curves with a single form, even with a bag outside the form, laying up very large surfaces using sheet plastic and dum-dum sealer at the edges and clamping work to a bench with full access to the edges, plus easy to store away in a small shop. If you are doing primarily flat layups of moderate size and have the space an old screw press could be useful.

    To the original question, a venturi setup with a well-sealed bag will cycle on rarely and use little power once the bag is evacuated. The problem is most bags get leaky over time, and clamping is inherently leaky enough to require full-time airflow. I have had a used 1/4 hp Gast 522 rotary vane pump for nearly 30 years that pulls a nominal 4 cfm at ambient pressure and can run constantly without issue (I do have a pressure switch on it). No worries about oil mist and any carbon wearing off the vanes is caught by an exhaust filter.
    Last edited by Kevin Jenness; 06-03-2021 at 7:56 AM.

  9. #9
    We just retired a pneumatic system with an electric pump. It runs constantly but the low hum is so much better than that horrible hissing cycling on and off during the day. We also like that we can turn off the compressor and go home with a pressing in the bag.

  10. #10
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    I went with one of the smaller continuous run vacuum pumps. It does a fine job on a 2x4 bag, which has been plenty big for my needs. It’s quiet...my shop is in the basement, and I can barely hear it running when upstairs.

  11. #11
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    Thanks for the input. I think I'll probably go with Veneer Supplies EVS kit and an inexpensive generic pump.

  12. #12
    Join Date
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    Quote Originally Posted by Jeff Roltgen View Post
    On the topic of bags - Don't get too wrapped up on the polyurethane hype. Won't mention which vendor, but I'd placed a less than stellar review and got squelched fast.
    Had made a table top frame with it, as well as buying a 4x8 conventional bag. Leaks, leaks, leaks. Vendor said it was my fault, as it was left folded on a shelf in a room that had florescent lighting.
    He explained that the polyurethane material breaks down when exposed to sunlight or florescent lighting.
    I've heard some weak arguments for sub-par products but a florescent lamp degrading a vacuum bag? Unless the internal coating on a fluorescent tube is totally cracked or missing only a very minuscule amount of UV radiation can make it through, certainly not more than other light sources around the house.

  13. #13
    Quote Originally Posted by Dave Cav View Post
    Thanks for the input. I think I'll probably go with Veneer Supplies EVS kit and an inexpensive generic pump.

    For venturi, consider AirVac Engineering's AVR093H - $35 plus shipping. It's the standard in most small commercial systems. A controller will run you more money. With a little engineering skills, you can take a take the vacuum diaphram off a Ford heater control valve, and make your own controller. For switch, use a water level switch, and inlet valve out of a GE dishwasher. Several you tubes out there.

  14. #14
    I have had an quality vak vm4 Venturi system for probably 25 yrs no issues, compressor hardly cycles at all if ever (depending on leaks of course) am using a small 10 gal and in my opinion it’s not loud at all

    https://www.qualityvak.com/air.html#vm

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