There’s a lot of vacuum going on in the woodworking industry. From treatment to routing to handling, vacuum systems help meet the demands for higher speed performance, greater precision, faster production and better quality. Vacuum technology enhances the skills and talents of operators. With a variety of well-established system designs to choose from, each offering various combinations of advantages, woodworking facilities of all sizes and production capabilities can precisely target their vacuum requirements to deliver maximum output. Here’s an overview of the most significant woodworking vacuum applications.
Versatile Vacuum Technology is a Force Behind Industrial Woodworking
Pod System CNC Routers
“Small but powerful” is the operative phrase for pod-system vacuum. The individual pods on the grid are small and don’t cover a lot of area. One system may have as few as four pods to as many as 24 pods, and they are adjustable. This gives the system flexibility in several ways, such as being able to machine on the sides and bottom of a piece. Since there is very little air that needs to be removed, a deeper vacuum is required for the additional holding force.
A small lubricated rotary vane vacuum pump is the most common type used for a pod system. It has sufficient flow and a consistent, deep vacuum for maximum holding power. They are usually air-cooled. The lubricated rotary vane has a simple mechanical design and is simple to install and has the additional benefits of being low-noise, low-maintenance pumps.
A lubricated rotary vane pump is a common solution for pod-system vacuum since it provides sufficient flow and a consistent, deep vacuum to provide maximum holding power.
Nesting CNC Routers
When you associate vacuum with woodworking, the ubiquitous nesting CNC routers are usually first to come to mind. As opposed to pod systems, nested systems have a larger area to cover, so a much larger capacity vacuum system is needed.
Hold-down force depends on the type of router tools, force generated by the depth of cut, feeding speed and other variables. Generally, the average hold-down force on a single piece should be around 2,000 pounds. Because there is a continual leak of air through the fiber board, a table with a fiber board of four by eight feet usually uses a vacuum system that can deliver a minimum of 300 ACFM with as much depth of vacuum as possible. Generally, a vacuum level between 18 to 24 inches mercury (Hg) is considered “the sweet spot.”
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Vacuum Pump Options and Considerations
A common solution for nesting routers is the oil-sealed liquid ring vacuum pump (LRVP). Less common are the lubricated rotary screw vacuum pump and dry (oil-free) rotary vane pump.
The lubricated rotary screw makes the grade for its high vacuum and energy efficiency. Rather than rotating vanes, the design incorporates two parallel screw rotors rotating in opposite directions. Because they never contact each other, there is virtually no wear, and are thus low maintenance. They run very quietly and are considered eco-friendly.
The dry rotary vane uses more energy but offers a wide performance range and deep vacuum. Like the rotary screw, there is no internal metal-to-metal contact (in this case, of the vanes), so they are durable and require little maintenance. Generally, the initial cost of dry pumps is greater and they require more expensive maintenance.
The challenge with using these two types of vacuum pumps in woodworking operations is the usual suspect – sawdust. Ingestion can break vacuum pump types such as the lubricated rotary screw
and dry rotary vane, unless the utmost care is taken to maintain the complete functionality of the inlet filter.
Carryover of wood dust into the vacuum pump and possible rupture of the filter element can increase pressure loss, resulting in a reduction of pump capacity and vacuum level. If the vacuum level is 24” Hg vacuum and there is a pressure drop of 2” Hg vacuum, the pump capacity loss is 33%. If the pressure drop is 3” Hg vacuum, the pump capacity loss is 50%! Because of the heavy dust load, the pressure drop can increase rapidly. It’s highly recommended to install a two-stage inlet filtration system to protect the pump.
Oil-sealed Liquid Ring Vacuum Pumps Stand Up to Woodworking Rigors
Using LRVPs is often a good choice for nested parts routers given the combined advantages offered. There is a wide range of product lines with ACFM capacities ranging from under one hundred into the thousands. High-efficiency, single-stage liquid ring vacuum pumps are capable of deep vacuum levels up to 29” HgV, with maximum efficiency throughout the vacuum range.
Oil-sealed liquid ring vacuum pumps, such as the DEKKER VmaxPLUS model, deliver efficient and reliable performance in sawdust environments.
The LRVP is easily incorporated into the woodworking environment. With its self-contained circulating system, the pump is basically “plug and play.” But the most significant advantage of the oil-sealed liquid ring vacuum pump is its steady performance in a sawdust-heavy work environment.
Woodworking may be the most difficult application for vacuum pumps. With a nested parts router, cutting and drilling puts the vacuum system right in the middle of a sawdust storm. The design of the LRVP allows it to handle soft solids and entrained liquids or vapors without compromising the pumps’ mechanical integrity or efficiency. This is because there is no metal-to-metal contact between the rotating parts and the casing, eliminating the need for internal lubrication. With noise levels in the 68 to 80 dBA range, “quiet running” is frequently mentioned by end users as one of the most popular features of the pump.
Rugged liquid ring pump systems are also known to provide years of trouble-free operation and don’t need to be rebuilt or replaced on a regular basis. The pump has only one moving part, and no metal-to-metal contact means the pump is wear-free. Grease-lubricated bearings are located external to the pumping chamber, negating the damaging effect contaminated lubricants can have on the bearings. The pump runs at a low operating temperature. Also, because oil is used instead of water for the seal liquid, the corrosion and scale buildup associated with water is completely eliminated. Preventive maintenance can be enhanced through “adders” that help safeguard the system, including an inlet filter, vacuum relief valve, spin-on oil filter and exhaust trip leg.
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Advantages of Variable Frequency Drives
A significant benefit of the various pump types is their adaptability to variable frequency drives (VFDs), which allow motors to adjust speed to match actual load. VFDs offer two advantages.
The first is reduced energy consumption (50% turndown on power) when the pump is not in use. Second, VFDs help eliminate part slippage. As leakage increases from cutting, the vacuum pump speeds up to maintain constant pressure, eliminating slippage and scrap. The pump may also have a longer operating life when not running at maximum output at all times.
An oil-sealed liquid ring pump with variable frequency drive control ensures the motor speed adjusts to match actual load.
Matching the Pump Technology to the Application
The specific requirements of the application will determine the ideal vacuum system. Consulting a woodworking vacuum distributor or manufacturer is recommended. Applications include preservation/impregnation, as well lamination/pressing and material handling.
Wood preservation extends the service life of timber products through the pressure impregnation of chemicals into wood to provide long-term resistance to fungi, bacteria, insects and more. The three most common pressure processes used – the full-cell (Bethel), modified full-cell, and empty-cell process (Rueping process or Lowry process) – all contain sequences in which vacuum and pressure are applied. The pressures used in treatments vary from about 50 to 250 pounds per square inch, depending on the species. Pressures commonly range from about 125 to 175 psi.
Preservation is a chemical-oriented process. According to the U.S. EPA, there are two general classes of wood preservatives: oils, such as creosote, pentachlorophenol, copper naphthenate and oxine copper; and waterborne salts, including chromated copper arsenate, copper zinc arsenate, copper azoles and borates, The versatile oil-lubricated rotary vane vacuum pump system is an excellent choice for the preservation process, particularly for its capability to handle entrained liquids and vapors from the chemicals.
In lamination/pressing applications, atmospheric pressure is a powerful source when used with adhesives to bond together layers of wood or wood material. The lubricated rotary vane and the oil-sealed liquid ring vacuum system are appropriate technologies for this application.
Another application in virtually every operation is material handling. However you want to handle, lift, maneuver, transport, load and unload wood products, vacuum helps get the job done. Vacuum lifters, frames and grippers with the capability to hold up to thousands of pounds are able to manipulate products while protecting them from damage, reducing labor time and enhancing safety.
From small or large work pieces, pieces with gaps, finished pieces and delicate veneers and more, the variety of material handling situations are met with a variety of vacuum types. An oil-sealed liquid ring system and both the dry and lubricated rotary vane vacuum pumps are well-adapted to handling, as is the variant of the oil-sealed LRVP, the water-sealed liquid ring. Water is the most used service liquid sealant.
In Control with Vacuum
The many advantages of versatile, powerful vacuum technology can be summed up in one word: control. The liquid ring, rotary vane and rotary screw vacuum pumps and systems, and the use of variable frequency drive, give woodworkers the surehanded, reliable control of the woodworking processes they need to ensure optimized production.
About the Author
Kevin Kalk is Vice President of Sales and Marketing, DEKKER Vacuum Technologies. Kalk has been with DEKKER for over three years and helped in product design and implementation, including products developed specifically with the woodworking industry in mind.
About DEKKER Vacuum Technologies
Established in 1998, DEKKER Vacuum Technologies is an industry leader in the manufacture and distribution of liquid ring vacuum pumps and compressors, rotary piston and rotary vane vacuum pumps and systems. For additional information, visit https://www.dekkervacuum.com/.
All photos courtesy of DEKKER Vacuum Technologies.
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