Troubleshooting

1. I hear air leaking from the bag stem connector. What should I do?
2. D'oh...I punctured my vacuum bag or I have a leak somewhere. How do I fix this?
3. How do I make my vacuum bag last as long as possible?
4. I think my system is leaking. How can I test it?
5. I just wired my system as shown in the directions and it's not turning on. What should I do?
6. How do I reset the vacuum gauge so the needle reads zero when there is no pressure on it?
7. My system is complete and it holds pressure perfectly after the pump cycles off but it takes a long time for it to shut off and I can't get it any higher than 21" of Hg. Why is that? 
8. My system seams to be leaking vacuum pressure. What should I do?
9. My system was running fine for years but recently it started to cycle on and off very frequently. How do I fix this?
10. My glycerin-filled vacuum gauge has an air bubble in it. Is it defective?

General Vacuum Press Questions

1. I want to build the vacuum press. Which version should I build?
2. How is vacuum measured?
3. Can you measure the total pounds of pressure under the platens in a vacuum bag?
4. What is CFM?
5. What if I can't pull the required vacuum within 10 minutes? And what is so important about "10 minutes" any how?
6. How much vacuum do I need?
7. What size vacuum pump should I look for?
8. Will quick-disconnect fittings for compressed air work with vacuum?
9. Is it safe to use PVC for the vacuum reservoirs?
10. I have extra PVC available. Should I consider making the vacuum reservoirs larger?
11. Do I have to use the "dual reservoir" design or can I use a single reservoir of comparable volume?
12. Do I have absolutely have to use a vacuum reservoir for my vacuum press?
13. Why should I buy parts and build a press when there are other companies offering similar pre-assembled units for the same amount of money? And since this pump will run continuously, how long will it last?
14. Are there any good books about veneering available?
15. Can a vacuum press be used for flooring inlays and medallions?
16. Does the vacuum valve have to be attached to the vacuum press? Can I attach it to the lock-on connector instead?
17. What else could I use for the reservoirs besides PVC?
18. Is it difficult to find the schedule 40 PVC for the reservoirs?
19. Why do I have to leave the bag connected to the vacuum press after it pulls the full vacuum?
    

Electric Vacuum Press Questions

1. Where can I find a vacuum pump?
2. Can I use a small Gast vacuum pump with a reservoir based system?
3. I already own a vacuum pump. What do I need to use it for vacuum pressing? And what size bag can I make for it?
4. Why do I need the vacuum controller, gauge, reservoirs and other parts to build the EVS system?
5. I live at 5,000 feet above sea level. What effect will that have on my vacuum pump?
6. What kind of pump will work for a vacuum press?
7. I have an odd ball vacuum pump available. What do I need to use it for vacuum pressing?
8. I've heard that some vacuum presses have a 'quick pull-down' scheme that allows you to release and quickly re-evacuate the press for minor adjustments. How can I accomplish this on my vacuum system?
9. What's the purpose of the bleeder valve on the continuous-run systems?
10. Is there a way to make the auto-cycling press run continuously?
11. I bought a 220v Gast vacuum pump from "surplus center". Will this work for vacuum pressing? Do I need and special parts to make it work.
12. I bought the rebuilt Thomas vacuum pump from the VeneerSupplies.com website. What is each port used for and how do I wire it?

Air Powered Vacuum Press Questions

1. With the Project: V2 system, does my compressor need to run continually?
2. How much air does the venturi version of the press require?
3. Is a venturi system better than an electric pump system?
4. Harbor Freight has a venturi pump rated at 28.3" of mercury and 4.2 CFM for only $17. Could this be used for a vacuum press? 
5. What do I do if my air compressor can't keep up with the venturi on my vacuum press?
6. How many licks does it take to get to the center of a Tootsie Roll Pop?
7. I want to build the Project: V2 Premium system but I don't want the full kit. Do you offer the Premium version of the Mac valve and venturi separately?
8. I've heard that Piab makes the best venturi vacuum generators because they are "multi-stage" units. Is that true?
9. Can I use the intake port on my air compressor to generate vacuum?
10. Do you offer a kit to upgrade the V2 kit to the V2 Premium?

Vacuum Bagging Questions

1. Since vinyl for bag making is only 54" wide, what should I do if I need a vacuum bag that is 6' wide?
2. What is a frame press?
3. What is the difference between vinyl and polyurethane for vacuum bags?
4. I'm on a budget and need to find a cheaper material for the vacuum bag. Any suggestions?
5. Can I use Space Bags™ and a Food Saver™ for veneering?
6. It's difficult to get everything into my large vacuum bag. What do you suggest?
7. What can I do to make my plastic bag closure easier to snap onto the bag?

Miscellaneous Questions

1. I'd like to use a refrigerant compressor from an old air conditioner. How do I make the connection from the compressor to the first part of the vacuum press?
2. Regarding the use of a refrigerant compressor for vacuum veneering...what kind of compressor (refrigerator, freezer, etc.) works best and what brand should I look for?
3. I'd like to use a refrigerant compressor for my system. Will the lack of oil in a compressor pump cause the unit to eventually burn out?
4. When vacuum clamping, how do I ensure a good seal on porous woods like mahogany?

Troubleshooting

T1: I hear air leaking from the bag stem connector. What should I do?

It's commonly thought that the sound of air flow in the vicinity of the valve stem and bag connector junction is a leak. If the sound from the valve stem area is not a clear "hiss" but instead sounds more like a combination of hiss and static (as on a poorly tuned radio station), then the leak is probably coming from a hole in the bag or from the bag clamps not being tightened adequately. Actually, what you are hearing is air being removed from the bag, through the valve stem/connector and into the reservoir and pump. You can simulate this sound by turning on your system and leaving the bag end unclamped.

You can further test the connection by placing a piece of duct tape inside the bag over the bottom of the valve stem (covering the entire stem base). Then attach the connector and turn on the pump. If you do not hear any sound near the stem, then the air you had originally heard was air flow as described above and you probably have a leak in your bag.

However, if the valve stem area has a clear, unmuffled "hissing" sound, it could be caused by air leaking between the connector and the stem. In this case, be sure to apply adequate downward pressure on the connector before releasing the locking lever. Usually, a quarter turn (clockwise) on the bag connector will further tighten the connection.

Please note: The vacuum connector does allow air flow when not connected to the vacuum bag stem. As you can probably tell, this connector is "borrowed" from the automotive industry. The manufacturer wanted to charge three times more for a unit that would hold vacuum pressure when disconnected. That feature isn't necessary for optimal vacuum operation and is hardly worth the expense. Additionally, allowing fresh air into the pump cleans out the air inside and prevents a buildup of airborne glue residue from occurring inside the pump cylinder.
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T2: D'oh...I punctured my vacuum bag or I have a leak somewhere. How do I fix this?

To find the leak, slide some paper inside the bag near the edges and insert your platens. Now place more paper near the valve stem and some in the vicinity of the bag closure. Close the bag and turn on the press. Allow the bag to develop some pressure. Then spray the edges of the bag with water. You should be able to see the leak if the paper becomes wet. Any leaks in the bag will show up as the water is absorbed by the paper. If not, try spraying water around the valve stem and the bag closure.

You may find it easier to add a little food coloring to the water before spraying the bag. This will dramatically improve the visibility of the leak. I've also found that brown kraft paper shows the water results very well.

If you notice the leak while the press is running and need a quick fix, just place some clear packing tape over the hole and press it down firmly.

For a more durable patch, cut a piece of vinyl about 1" square and attach it to the outside of the bag with vinyl cement. Don't forget to prepare the patch and the exterior of the bag. Using acetone or xylene, clean the surfaces where the patch will be placed. Very fine steel wool will aid in the cleaning process, but you must be sure that no steel residue is left when you are finished. Apply the patch and press it down using a J-roller or a seam tool. Then turn off the press and allow the patch to dry over night.

Vinyl patch kits used for repairing swimming pool liners also works well.
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T3: How do I make my vacuum bag last as long as possible?

General Vacuum Press Questions

G1: I want to build the vacuum press. Which version should I build?

Click here for a breakdown of the various types of systems.
Or check out this link which is a chart of the systems offered at VeneerSupplies.com
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G2: How is vacuum measured?

In vacuum veneering, the vacuum level is usually measured in terms of inches of mercury (" of Hg).
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G3: Can you measure the total pounds of pressure under the platens in a vacuum bag?

The total pressure can be calculated by the vacuum pressure (in Hg) multiplied by .5. Then multiply this number by the total square inches of one platen. Therefore, if you are applying 23" of Hg to a platen that is 1'L x 2'W, the calculation is as follows:

23 x .5 x 288 = 3312 pounds of force.

For more information, see this chart.
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G4: What is CFM?

CFM or "cubic feet per minute" will only describe the speed at which the vacuum is created. It is a measurement of the amount of air volume that can be moved within a specified time frame. The "CFM" rating will not give you an idea as to the maximum possible vacuum pressure.
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G5: What if I can't pull the required vacuum within 10 minutes? And what is so important about "10 minutes" any how?

Ten minutes is the average amount of time that most users will have to get a project under vacuum pressure before the veneer glue starts to set up. If the glue starts to set up before decent pressure is on the project, the veneer may not adhere correctly.

If you can't get the pressure on the project within 10 minutes, you can use a smaller bag, a slower setting glue, chill the air in the work shop (to slow down the glue flash), or add an additional pump. Or...

You can also use a Shop-Vac to pull some of the bulk air when using exceptionally large vacuum bags. The easiest way to do it is to tee in a ball valve to the vacuum line (between the reservoir and the bag). Then you'll need to rig up a few fittings to mate the Shop-Vac hose to the vacuum line. Most Shop-Vacs will only pull about 1.75" of Hg (provided the filter is clean) but this low pressure air in your bags could be a lot of volume and waste a lot of core vacuum time by the pump. As soon as the bulk air is removed, close the ball valve, then shut off the Shop-Vac (in that order). For an idea on building this contraption, see the box below.

From a vacuum press builder in Naperville, Illinois ... "...I started out in the tool department, with an air compressor tee and connectors (I had trouble finding them, but Coleman makes them). Then I moved to plumbing and got a ball valve and a series of adapters to go from 1/4" to 1" pipe. Finally, I ended up finding a piece that's meant for a dishwasher connection that will let me connect the whole mess to my Fein shop vac with duct tape."

[Click to enlarge]

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For vacuum veneering, you'll need a minimum of 18" of Hg. However, the recommended pressure for most adhesives is 21" of Hg.
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G7: What size vacuum pump should I look for?

The critical factor is that it must be able to pull at least 18" of Hg.

There are basic rules that determine the size (or CFM) of the vacuum source needed for various projects. Check out this chart to see which system is right for you. Keep in mind, these are rough estimates.

G8: Will quick-disconnect fittings for compressed air work with vacuum?

Unfortunately, quick-disconnect fittings will not work with negative pressure.
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G9: Is it safe to use PVC for the vacuum reservoirs?

This information is provided by Uni-Bell:
Yes, PVC pipe can withstand vacuum pressures.  According to research conducted by Dr. R.K. Watkins at Utah State University, vacuum pressures cannot collapse PVC pipe that is exposed to normal service temperatures.  In fact, quick calculations show that even under conditions of elevated operating temperatures of 100^oF, the pressure required to collapse most PVC pipe is greater than atmospheric.  In other words, the pipe can withstand a complete vacuum.

For more information please see this article from the Uni-Bell PVC Pipe Newsletter.

Please note, cell core PVC or any other form of plastic including ABS is not recommended for vacuum pressure. The pipe must meet ASTM D1785 or D2241 requirements.

*Uni-Bell has served the engineering, regulatory, public health and standardization communities with integrity and considerable measures of both time and resources. Whenever questions have arisen relative to PVC pipe performance, Uni-Bell members, through their Association, have responded. Pipe designers and installers have been provided with much needed research from Uni-Bell regarding pipe deflection, ultraviolet aging, tapping, cyclic surge performance, in-service durability, and safety.

Schedule 80 PVC
(Thanks to Jean-Philippe Mendes for pointing out this article)
Solid core schedule 80 PVC can also be used for vacuum pressure according to George Fischer Piping Systems. Click here to see their conclusion. The full article can be found by clicking here.
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G10: I have extra PVC available. Should I consider making the vacuum reservoirs larger?

Larger vacuum reservoirs will allow the system to recharge less often. However, the recharging cycles will be longer. Conventional wisdom says that the unit will last longer if it cycles on less often but the truth is that the moving components on the Mac valve and vacuum switch are rated for a hundred thousand cycles or more. So the benefit of the larger tank isn't really earth shattering.
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G11: Do I have to use the "dual reservoir" design or can I use a single reservoir of comparable volume?

There is no problem changing the tank design from a dual to a single reservoir design. You could also use a triple or quad reservoir design if you wish.
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G12: Do I have absolutely have to use a vacuum reservoir for my vacuum press?

The vacuum controller I offer can be used without a vacuum reservoir. To do this, the vacuum pressure is measured from inside the vacuum tube. You just need to make a "T" connection in the vacuum line.

However, I highly recommend using a reservoir. The vacuum reservoir serves as a buffer zone (or a backup for vacuum pressure). Without it, your system will constantly turn on and off. This will lead to premature failure of any pump. The reservoir also serves as a coarse filter. It will collect any heavy debris that come through the bag and through the air line tube.
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G13: Why should I buy parts and build a press when there are other companies offering similar pre-assembled units for the same amount of money? And since this pump will run continuously, how long will it last?

Despite that fact that each system achieves similar results, there is an inherent quality difference between the systems. I've seen the most of the low-tech vacuum systems in operation and they all work well but their systems consist of a generic imported vacuum pump and cheap accessories. The pumps that we (VeneerSupplies.com) offer are made in the USA and have rebuild kits that the manufacturers have promised to offer for a minimum of 10 years. In fact, Gast has been using the same filters, valves, and gaskets on their pumps since 1981!

Additionally, our press parts are all nonproprietary so you can add and modify the unit as needed. For instance, with our kit, you can build a vacuum bag in any size you want and still connect it easily to the pump system. With bags from other manufacturers, you are limited to the sizes they stock and should they ever change the bag connector design, you may not be able to add future bags if one were to go bad.

The nonproprietary parts we offer allow you to hook up additional bags with simple T-fittings found at the hardware store. This system is also easily adaptable for use with vacuum clamping and templating.

Overall, you get the same end result with either system (ours or theirs) for about the same amount of money. Our system requires a bit of your time, but it includes heavy duty components adapted from other industries (at industrial level specs); not imported parts that were assembled trying to maintain a healthy "margin". A good example of this is in the vacuum gauge. On other systems, they use plastic dry gauges. This causes needle flutter which makes reading the gauge impossible. Our stainless steel gauge is glycerin filled so the needle doesn't flutter and you can see exactly what pressure is in the system.

Needle Flutter (What pressure is it reading?)

And unlike the bare-bones kits that our competitors offer, our Excel Vacuum Press system has a fully adjustable vacuum range for delicate projects. You can dial it in for any pressure from 840 to 1750 lbs of pressure per square foot.

The truth is that we don't have the "overhead" as other companies. We ship website orders from my workshop so we don't need the high financial return from the sale of the systems and components. So what you get is a heavier duty system at the same price that can be modified and adapted as your veneering skills expand. For more information, check out this page... "Why Build A Vacuum Press"   

How long will the pump last?

The manufacturer says that if the pump were left running continuously, it would be two years before it would need to be rebuilt.
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G14: Are there any good books about veneering out there?

Yes! There are two exceptional books on veneering that would make great additions to a woodworking library.

The first is called the The Complete Manual of Wood Veneering by William Lincoln. It reads more like a high school text book than a "manual" but it is very thorough and well organized. It's currently out of print but it does show up on Ebay rather often.

The other book I recommend is Veneering: A Foundation Course by Mike Burton. This book was out of print and hard to find for quite a while but it was revised and published again in June of 2006. The new version includes a section on marquetry which was a great compliment to the other chapters. Mike Burton covers various forms of veneer application including vacuum pressing, iron-on veneering, and more traditional methods. The book also includes a few well designed veneering projects. One thing that I really enjoyed is the author's down to earth writing style. He writes as if he was speaking directly to you and his comments are insightful and often downright hilarious.
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G15: Can a vacuum press be used for flooring inlays and medallions?

Yes. I've helped several inlay and medallion craftsmen build systems for this purpose. But to be honest, I only have a rough idea as to how these specialists do their work.

They built a wooden frame, wrap it in 30 gauge vinyl sheeting and put gasket tape under the frame (attached to the vinyl). After a valve stem is attached to the center of the vinyl, they place breather mesh over the inlay so the vinyl can pull down evenly over the entire project.

Since some species of wood used for flooring are porous, air will leak into the system. If you have a cycling vacuum press such as the Project: V2 or EVS system, you can easily wire in a switch to convert it to run continuously.See FAQ E10
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G16: Does the vacuum valve have to be attached to the vacuum press? Can I attach it to the lock-on connector instead?

Since the threads on those fittings are the same (1/4" NPT) you can easily move the vacuum valve from the system to the lock-on connector. This requires no additional parts and simplifies the process of vacuum bagging by allowing you to open the vacuum flow from the vacuum press immediately after you connect the lock-on connector to the bag.
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G17: What else could I use for the reservoirs besides PVC?

There are no easy and safe answers to this question. I have seen vacuum press reservoirs made from fire extinguishers, scuba tanks, air compressor tanks, ABS plastic, aluminum tanks, and many other materials. Ultimately, the question is of safety. None of these are considered safe for vacuum unless the manufacturer specifically says so.

The only material that is scientifically proven safe for vacuum is schedule 40 or 80 solid core PVC.
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G18: Is it difficult to find the schedule 40 PVC for the reservoirs?

In the eastern and midwest areas of the US, schedule 40 PVC pipe can be found at most plumbing suppliers. I have heard from several west coast residents that schedule 40 PVC can only be found at "specialty" plumbing dealers.

Canada appears to have a good supply of schedule 40 PVC.

Schedule 40 PVC pipe is not available in Australia. I have been advised that the Australian equivalent is Class 12 Water Pressure Pipe. Only specialty irrigation/pipe centers handle it. It is rather expensive so consider purchasing the PVC kit from the VeneerSupplies.com website to save a few bucks.
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G19: Why do I have to leave the bag connected to the vacuum press after it pulls the full vacuum?

No matter what anyone says, a perfect seal on a vacuum bag is nearly impossible. One could argue this until the cows come flyin' home but the bottom line is that a bag will leak from time to time. Why?

• Sometimes the bag closure doesn't seat perfectly across the opening and needs to be repositioned.
• Sometimes the residual air pressure makes its way from the core of the substrate and platen components which reduces the pressure inside. This happens most often when there is a large project in the bag. You'll hear the vacuum system cycle off (if you have any auto-cycling system) and then turn on again for a few seconds. After that, it may not cycle again for several minutes or even hours.
• After many uses some bags develop pin holes which can be hard to find. In those cases, it's best to let the vacuum press keep the bag pressure in control.

When a leak happens, you won't know it because there is no gauge on the bag. If the bag is connected to the system, you could easily see the pressure reading by looking at the gauge. The pressure inside the vacuum press system is the same amount of pressure inside the bag. If your vacuum press cycles on and off too frequently during a project, you know there is a leak and if you can fix it, great. But if you can't, at least the vacuum system will keep the bag under pressure until the panel is finished.

If you are still hell-bent on disconnecting the bag from the system, you can purchase tire stem caps from your local automotive store (good ones!) and attach one to your bag stem immediately after pulling the initial vacuum. But are you willing to risk a botched panel with expensive veneer for the sake of it all?
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Electric Vacuum Press Questions

E1: Where can I find a vacuum pump?

Of course, I offer pumps at the VeneerSupplies.com. You can also look in the phone book under "salvage" for used pumps. Be careful with salvaged units because vacuum pumps can be used in a variety of hazardous conditions such as use from medical and toxic waste disposal. You might also try calling a local appliance repair company and asking for a used compressor from a refrigerator, dehumidifier, or air conditioning unit.
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E2: Can I use a small Gast vacuum pump with a reservoir based system?

You can use a reservoir based system (and the vacuum controller) with any pump. But there is no problem with letting smaller pumps run for the whole time the veneer is being pressed. This eliminates the need for a vacuum reservoir and vacuum controller. VeneerSupplies.com offers a kit to turn just about any pump into a continuously running vacuum press system with full pressure adjustment. Click here for details.
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E3: I already own a vacuum pump. What do I need to use it for vacuum pressing?
       And what size bag can I make for it?

The first thing to do is find the specs for the pump. Most of the manufacturers have great customer service and if you provide them with the model number of your pump, they can give you these specifications:

• Thread size of the ports
• Vacuum flow at 0 pressure (CFM)
• Amperage at startup
• Maximum vacuum in inches of Mercury (" hg)

Your vacuum pump will need to pull at least 21" of Hg to do flat veneer work. Additionally, it should be rated for at least 3 CFM which will allow you a maximum bag size of 4 x 8. To use the pump for vacuum pressing, you'll first need to decide whether you want it to run continuously while pressing a veneer or have it auto-cycle on and off. You can learn more about the differences between a continuous-run and a auto-cycling vacuum press at this link.

Auto-Cycling Vacuum Press
Use the Project: EVS builder's kit offered at VeneerSupplies.com and the instructions found here.

Port Size: Make sure the vacuum port on the pump has 1/4" NPT threads. The builder's kit is designed to use this thread size. If your pump has a different thread size, you'll need an adapter to change it to 1/4" NPT. These can be found at hardware stores and also by clicking here.

Vacuum Flow: If your pump has a flow rating of more than 4 CFM, you will also need a vacuum dampener to prevent the vacuum controller from "chattering". This occurs when the individual rotations of the pump draw larger amounts of vacuum. It causes the vacuum controller to turn on and off rapidly which may damage the pump.

Start Up Amps: The "running" amperage is usually low on most vacuum pumps, but the "start up" amps can be the killer. The vacuum controller on the EVS kit will handle up to 10 amps. If your pump draws more than 10 amps at start up you will need a relay which will handle the high-current switching. You can find more information about wiring a relay to the vacuum controller by clicking here.

Continuous-Run Vacuum Press
Use the Project: CRS builder's kit offered at VenerSupplies.com and the instructions found here.

Additional Notes
Based on experience, I do not recommend rotary vane vacuum pumps. I have found them difficult to fine tune for vacuum pressing and they draw a tremendous amount of power when they start up. There are much better choices in vacuum pumps than rotary vane.
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E4: Why do I need the vacuum controller, gauge, reservoirs and other parts to build the EVS system?

In a perfect world, you'd only need to connect the intake of the vacuum pump to a tube which would be connected to a vacuum bag to have a working vacuum press. All of the "extras" on the Project: EVS and V2 systems might seem a little unnecessary but each has a place and purpose on an auto-cycling system.

The Vacuum Gauge Obviously, the gauge shows the user the vacuum level inside the system. More importantly, it shows the user if there is a leak. When the system cycles off, the needle on the gauge will move subtly, but it's enough to indicate when a leak is present.

The Vacuum Controller Without this piece, the system would run continuously. This is fine if you don't mind the 74 decibels of sound being continuously emitted from the pump. Or if you are not bothered by the waste of electricity from a pump that has to run for the entire duration of the pressing. The vacuum controller monitors the vacuum pressure and cycles the system on and off as needed.

The Vacuum Reservoirs If you are going to have a system that cycles on and off, you certainly don't want it to cycle too frequently. This is bad for the pump and it's just plain annoying. The reservoirs hold spare vacuum pressure just like scuba tanks hold air for divers. If you have an air compressor in your shop, you certainly understand that a larger tank on an air compressor means that it will cycle on less frequently. The same is true of the vacuum reservoirs.

The Vacuum Valve The vacuum valve allows you to pre-charge the reservoirs with vacuum pressure which will give you a short burst of vacuum pressure in the initial pull-down of the vacuum bag.

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E5: I live at 5,000 feet above sea level. What effect will that have on my vacuum pump?

The general rule of thumb is a loss of 1" of Hg for every 1,000 feet above sea level. A pump that delivers 25" of Hg, will actually provide 20" of Hg at 5,000 feet above sea level. This pump would be fine for vacuum veneering but you might find that it takes more time to achieve 20". In that case, simply turn back the shut-off point on the vacuum controller. A setting of 17" to 18" of Hg will still yield a good veneered panel. For a more detailed chart describing the effects of altitude on vacuum pressure, please click here.
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E6: What kind of pump will work for a vacuum press?

Any vacuum pump that can pull 20" of hg will work with the system. Vacuum presses can be made from rotary vane, oil bath, diaphragm,and piston based pumps.
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E7: I have an odd ball vacuum pump available. What do I need to use it for vacuum pressing?

1. Most importantly, you need to figure out how to get your pump to adapt to a 1/4" NPT pipe fitting. Sometimes, that's pretty easy and other times, it can be a real pain.
   
2. You'll need to know how many amps it draws at start up. The best thing to do is call the manufacturer. If it is more than 10 amps, you'll need to wire in a relay.
   
   See the links below for more info on using a relay...
   http://www.joewoodworker.com/veneering/EVS/wiring.htm (see "situation 2")
   http://www.veneersupplies.com/product_info.php?cPath=36&products_id=513

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E8: I've heard that some vacuum presses have a 'quick pull-down' scheme that allows you to release and quickly re-evacuate the press for minor adjustments. How can I accomplish this on my vacuum system?

Easy. Simply attach a vacuum valve between the reservoir and the main vacuum tube that goes to the vacuum bag. This allows you to shut down the vacuum pressure without losing the pressure inside the reservoirs. You can then re-adjust the material and re-connect the bag to the system. After you open the vacuum valve, the buffer of vacuum  will then transfer to the bag and give you a short burst of vacuum pressure. Of course, the press will start to recharge the reservoirs almost immediately but at least you still get that faster initial pull down. All of the builder's kits offered at VeneerSupplies.com now come with a valve.
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E9: What's the purpose of the bleeder valve on the continuous-run systems?

The bleeder valve serves several functions. The core reason is that it allows you to easily adjust the pressure in the system. But it’s important to note that the bleeder valve also allows the pump to circulate a little bit of fresh air through it so any off-gases from adhesives are allowed to escape.

The pumps are continuous duty, but they can generate some heat which can cause the off-gases to create a build up of residue. This residue will clog the head-valve inside and reduce the efficiency of the pump. And eventually, the residue will harden the flexible surface of the diaphragm and cause it to crack prematurely.

Piston based pumps are also prone to residue build up which can cause the pump to over-heat as the friction on the cylinder walls builds up.

There are several companies offering continuous-run system but few (if any) offer a bleeder valve with the system. My gut feeling is that they don't offer it because they feel the system will not be used frequently enough to warrant the expense of the valve.

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E10: Is there a way to make the auto-cycling press run continuously?

Air Powered Vacuum Press Questions

A1: With the Project: V2 system, does my compressor need to run continually?

No. Think of it this way... the Mac valve is a gate that controls the flow of air from the air compressor only when the vacuum controller recognizes the need for additional vacuum. The venturi pulls vacuum very quickly. In fact the reservoirs tanks will achieve full vacuum in just 20 seconds. After that, the compressed air is shut off automatically.
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A2: How much air does the venturi version of the press require?

The CFM for the "plus" model venturi is 4.8 CFM at 80 PSI. The "premium" model requires 7.8 CFM at 80 PSI.

Smaller air compressors may require a separate reserve tank that will easily piggy-back to your existing tank and give you more pressure in reserve to get the initial vacuum created in the bag. If the pressure coming out of the air compressor drops below 80 PSI, the air coming out of the compressor will just be wasted. It really needs the full 80 PSI to work correctly.

The temporary fix is to manually shut off the venturi press until the compressor has reached 80 PSI, then turn the system back on and let it generate vacuum again until it is below 80 PSI. By doing this, it may take longer to pull a full vacuum but you will not lose any noticeable vacuum pressure inside the system because of the check valve.

If you would like to add a piggy-back tank to your existing air compressor, I've heard that Northern Tool carries them at a reasonable price (though I've also found their shipping rates to be a bit high).

A3: Is a venturi system better than an electric pump system?

Both systems work nearly identically but there are some details that might swing your vote in one direction or another. Click here for more help.
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A4: Harbor Freight has a venturi pump rated at 28.3" of mercury and 4.2 CFM for only $17. Could this be used for a vacuum press? 

VB1: Since vinyl for bag making is only 54" wide, what should I do if I need a vacuum bag that is 6' wide?

You can make a vacuum bag of any size. I have made huge bags by making two "tubes" of vinyl and gluing them end to end. This gave me a bag size of 25" by 108". I have also glued two pieces of vinyl 54" wide by 6' long together (side by side) and then rolled the edge together to make a 4' x 6' bag. You can fuse together as much vinyl as necessary to get the size and shape you need. The HH-66 cement is very powerful stuff!
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VB2: What is a frame press?

Basically, a frame press is a table with weather-stripping around the edges. The vacuum port is attached on the bottom. The top frame is hinged and has vinyl or polyurethane sheeting in the center. The amount of vinyl can be adjusted for panels that are thicker. The weather-stripping around the frame isn't the best way to seal the bag and consequently, it's not uncommon for the vacuum system to run constantly during use. Frame presses are also difficult to store in a small shop. Remember...a standard bag press is super easy to fold up and stow away!
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VB3: What is the difference between vinyl and polyurethane for vacuum bags?

Polyurethane is more resilient than most vinyl. Its superb flexibility allows it to retain its shape even when stretched to the extremes which makes it good for curved projects. On the flip side, polyurethane can be considerably more expensive than vinyl and most polyurethane films can not be bonded with HH-66 cement. The good news is that VeneerSupplies.com has an affordable polyurethane material that will bond with HH-66. For more information about polyurethane vs. vinyl for vacuum bagging, click here.
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VB4: I'm on a budget and need to find a cheaper material for the vacuum bag. Any suggestions?

If you have access to an old waterbed mattress, you're in luck. The mattresses are usually made of a decent grade of vinyl. The only downfall is that most of them are not clear so seeing the panel and platens is not possible. For seasoned press users, this may not make much difference but for others, it may make things more difficult.

There have been reports that inflatable air mattresses will also work for vacuum bags but I have not tested this.

I've also received emails from users who have built a vacuum bag with PVC shower pan liner available at most home centers. It's a thick vinyl material that is gray in color and is usually sold by the linear foot. It's not really cheaper than the 30 gauge vinyl but if you have access to some scraps, it will make a nice vacuum press bag. With this material, you can cement the bag with Oatey PVC cement.

Follow-up question:
Can I use the Oatey PVC cement for making bags from vinyl material?

Nope. I've tried 3 different versions of PVC cement and none of them work.
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From Bobby Tonsly...
Trying to be cheap, I decided to use one of my wife's clothing space bags for vacuum pressing a panel. The hard part was trying to get the vacuum tube to connect to the bag. I never got a connection that was completely free of leaks but I did manage to get the bag down to 21" of vacuum. The press ran almost continuously. The good news is that the panel turned out well but on the next panel, the bag developed a tear. Of course, the wife was ticked off but at least they are cheap. I ordered her a replacement bag and immediately after that, I ordered a real vacuum bag.

From Joe Hillenborough...
I placed a vacuum gauge inside of a Food Saver bag and sucked it down with the Food Saver unit. It doesn't draw enough vacuum to do veneering. I guess that why they don't call it a "Veneer Saver".
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VB6: It's difficult to get everything into my large vacuum bag. What do you suggest?

First, a large project going into a large bag should be the work of two people. Get a hand from a friend or spouse to help get the project loaded.

Second, consider cutting off the seal on the far end of the bag. It is much easier for two people to load the project when one person can help pull it in from the other side. To make this work, you'll only need to purchase a second bag closure.
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VB7: What can I do to make my plastic bag closure easier to snap onto the bag?

A light coat of car wax or a wiped-on coat of silicone spray will make it easier to snap the bag closure over the vinyl or polyurethane vacuum bag. Be certain that neither of these products is accidentally applied to the inside of the bag where it could foul the work piece for finishing.

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M1: I'd like to use a refrigerant compressor from an old air conditioner. How do I make the connection from the compressor to the first part of the vacuum press?

It can be difficult to find fittings to make that first connection. I've found two decent solutions that work on most of these pumps. First I want to remind anyone using a refrigerant compressor to please have the refrigerant professionally withdrawn from the system before you remove it from the equipment. The freon inside is horrendously harmful to our atmosphere. It's not worth the weight that will sit on your shoulders when you see how much refrigerant will come out of even the smallest system.

If the copper tubing on the refrigerant compressor is reasonably close to 1/4" outside diameter, you can make an easy connection to the first component of the vacuum press (either the reservoir or the Mac valve) by simply sliding a piece of 1/4" inside diameter vinyl vacuum tube over it. On the other end of the tube you can attached a brass barbed fitting to get to 1/4" NPT threads. If the vacuum tubing doesn't quite fit, you can heat it in hot water to make it more flexible and it will slide on easier.

If there is no way to get the vacuum tube connected directly to the copper tubing on the compressor, you can take the pump to the hardware store and find the closest matching brass component (with 1/4" NPT threads) that will fit over the copper tubing and bond it on with JB Weld. Yes, this really works very nicely!

From Jim Wilson (click here for more)
"One of the obstacles I encountered was the 5/16" inlet line -- I couldn't find anything in that size locally, except compression fittings, which I wanted to avoid. Finally, I reamed a short piece of 3/8" refrigeration tubing to 5/16", soldered it to the inl