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JoeWoodworker Veneer
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Part 1
Introduction

Welcome
Veneering Basics

14 Good Reasons
Vacuum Press Uses
Vacuum Press Options
Overview

Questions & Answers
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Part 2a (Option 1 of 2)
Project: V2 Venturi Press

About Project: V2
Parts List
Build the Manifold
Build the Reservoirs
Assemble the Venturi
Make the Carrier
Wire the Press
Testing and Adjusting
Mods and Options
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Part 2b (Option 2 of 2)
Project: EVS Pump Press

About Project: EVS
Parts List
Pump Selection
Build the Manifold
Build the Sub-Manifold
Build the Reservoirs
Make the Carrier
Final Assembly
Wire the Press
Testing and Adjusting
Mods and Options
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Part 3
Vacuum Bagging

Vacuum Bag Basics
Polyurethane vs. Vinyl
DIY Vacuum Bags (A)
DIY Vacuum Bags (B)
Connect the Bag
Bag Closures
Bag Platens
Breather Mesh
Maintenance
DIY Frame Press

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Part 4
Veneer Information

About Veneer
Veneering Glossary
Veneering Myths
Backer Veneer

Veneer Glues
Veneering Tips
Substrate Materials
Flattening Veneers
A Sharp Veneer Saw
Jointing Veneers
Taping Veneers
Dealing with Defects
Curing Glued Panels
Veneering w/o Vacuum
Hammer Veneering
Iron-On Veneering
Veneer Storage
Amazing Bookmatches
Copper Veneer Guide
Paperbacked Veneer

Edgebanding Guide
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Part 5
Miscellaneous Info

Vacuum Forming
Vacuum Chucking
Vacuum Clamping
Vacuum Clamp Matrix
Vacuum Infusing
DIY Vacuum Manifold
Vacuum Press Gallery 1
Vacuum Press Gallery 2

Veneering FAQ
Veneer Glue FAQ
The Vac FAQ
Copper Veneer FAQ
Downloads (PDF's)

VeneerSupplies.com

EVS Logo Information
Type: Adjustable Auto-Cycling
Vacuum: Electric Pump
Page: 3 of 11
EVS Kit

Selecting A Vacuum Pump

Speed and Maximum Pressure
Vacuum Press PumpVacuum pumps are often rated on the flow capacity which is stated as CFM (cubic feet per minute). This references the speed at which the pump is capable of moving or removing air and is most often measured at zero pressure. A pump rated at 1 CFM will be fine for flat panel work on vacuum bags up to 4' x 4'. For bags up to 4' x 8' a 3 CFM or greater pump is needed.

If your vacuum press will be pulling down curved veneer forms or bent laminations, the general rule of thumb is that the pump must be three times faster. This means that a 3 CFM or greater pump is best for vacuum bags up to 4' x 4' for this type of use. Why? Because there is, on average, 3 times more free air inside of a bag containing a bent lamination than there is inside a bag containing a flat panel.

Vacuum pumps are also rated by their maximum achievable vacuum level at sea level which is often expressed as inches of mercury or "Hg". For vacuum veneering, the minimum acceptable level of vacuum is 18" of Hg. The ideal vacuum level though is 21" of Hg. At the high end, the maximum level of vacuum for veneer work is 25.5" of Hg. Anything over this amount is not only overkill, it's also harder on the pump. Additionally, extreme vacuum levels can cause the veneer to develop small pustules of glue on the veneer face.

Types of Vacuum Pumps
The next consideration when building a pump based vacuum press system is the pump style. Here are the some of the options:

  • Diaphragm pumps are very quiet and durable. This type of pump is oil-less and usually has a small footprint. They are ideal pumps for a vacuum system. Typical CFM rating is 1 to 3.
Gast Diaphragm Vacuum Pump
  • Piston pumps are not as quiet as diaphragm pumps, but are just as durable. They are almost always oil-less and also work well for a vacuum press. Typical range of CFM is 2 to 5.
  • Oil bath pumps are less noisy than piston pumps but not as quiet as diaphragm pumps. This type of pump has a tendency to emit a plume of oil into the air. To the best of my knowledge, there is no way to contain the oil smoke. For most users, this can be a huge issue that causes problems with the finish that is applied to the veneered project or any other unfinished project in the vicinity of the pump. This type of pump requires occasional oil changes and can draw a large amount of amperage. Usually, these pumps range from 3 to 6 CFM.
Robinaire Vacuum Pump
  • Rotary vane pumps are designed to run continuously. I have found them difficult to fine tune for vacuum pressing and they draw a tremendous amount of power when they start up. Rotary vane pumps are designed to run continuously. This type of pump is not suitable for systems which cycle on and off frequently. I suggest avoiding this type of pump for the EVS vacuum press system. You will need a relay to do the high current switching for the vacuum controller if you use this type of vacuum pump. A vacuum damper for the vacuum controller will also be required. These pumps are notoriously difficult to adapt to vacuum press use due to electrical issues. This is especially true of Gast 0522 and 0523 pumps.
Gast Rotary Vane Vacuum Pump
  • Refrigerant compressors can also be used for limited runs of vacuum press work. They are quiet, but slow to pull a full vacuum. Typical CFM is less than 1.
Refrigerant Compressor

Restart Pressure
Project EVS Vacuum System with Gast PumpThe pump's ability to restart while under pressure is not a factor in selecting a model for vacuum pressing. The Project: EVS system uses a sub-reservoir and Mac valve assembly to unload the vacuum from the pump's intake port. Even if the pump you have selected can restart under pressure, it's a good idea to vent off the pressure after each cycle.

"Regardless of the restarting capability, pressure should always be released from the system to maintain proper life expectancy of the internal valves in each pump. This is true for all pump models including piston, diaphragm, and rotary vane."
                                                       
- Gast Manufacturing

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