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Veneer use grows: as raw materials shrink.


For decades, the woodworking industry has experimented with veneering to try to obtain higher yields, minimize waste and produce high quality appearance to compensate for the loss of shrinking resources. With fewer lumber resources than the United States, the increasing demand for improved veneering technology in Europe has become even more significant. "If it's flat, Europeans will veneer it. But Americans don't think that way," said George Force, president of Force Machinery Co. "The quality of wood has gone down tremendously here, and veneering is the answer."

Major price increases and decreased supplies of quality lumber have prompted some U.S. wood product manufacturers to research and invest in more advanced veneering equipment to make quality goods that look as good as their solid wood counterparts. "Larger trees generally give more clear wood and better veneers," according to Henry van Brussel, president of Ruckle Veneer Systems Inc. "But there is a drop in log quality because harvesters are cutting less mature trees where the diameter is smaller."

Veneer usage is also growing because customers of wood products manufacturers are accepting veneers over solid woods because of price and improved quality in veneer products. Lewis Buchner of Buchner Design Studio Inc. thinks customers in the design community have become more sophisticated by including veneers over solid wood in their plans. "This is because we're seeing more traditional patterns in architecture," he said.

Making the grade

According to the USDA Forest Service guide "Wood Veneer: Log Selection, Cutting and Dying," most species of hardwoods and softwoods can be successfully cut into veneer. Hardwoods, as a class, are easier to cut into veneer than softwoods. Although it is unknown why, two possible theories are that hardwoods contain less lignin than softwoods and that the lignin in hardwoods is more thermoplastic.

Veneer is often cut soon after a tree is felled because the wood is more pliable wet than dry. Moisture contents stand around 50 to 60 percent, and it is advisable to carefully check veneers with a moisture meter before applying them to the substrate to eliminate problems associated with high moisture content veneers.

Veneers are classified into three basic categories: "A" grades, which include decorative or fancy-face veneers, "B" grades, which are often used for inner plies of decorative panels and "C" grades, which are used for container veneer and plywood.

Higher yields

A trend in overseas markets is the use of thinner veneers to get higher veneer yields from logs. "Some species like walnut and cherry are indigenous to North America and are highly prized by overseas manufacturers," said Bill Groah, technical director of the Hardwood Plywood Manufacturers Association. He said the standard thickness for most domestic veneers ranges from 1/32 inch to 1/42 inch and the thickness for export veneers can range from 1/36 inch to 1/50 inch.

"Thinner veneers are being used by overseas producers because manufacturers use more particleboard, which has a homogenous surface that is less likely to telegraph," he said.

Will the U.S. adapt to thinner veneers? Groah thinks it will happen, "because veneering's biggest advantage is better utilization of our natural resources."

Quality surfaces

To obtain higher yields and reduce waste, veneer equipment manufacturers are designing machines that can meet these exacting tolerances. Many manufacturers are now incorporating computers into their machines to improve accuracy. "The trend right now is toward more sophisticated equipment," said Hank Serdio, international sales engineer at Coe Manufacturing. "In veneer lathe chargers with laser scanners, a computer will give the best geometric center in order to maximize veneer recovery."

Since veneering is such a demanding process that is done in tenths, hundredths and thousandths of an inch, quality control and machinery adjustments must be carefully controlled. At the same time, the machines must give product manufacturers good quality, durability, low maintenance and affordability.

"Manufacturers are looking for a tight, precise veneer joint, better quality materials, a perfect surface finish without bubbles and a high quality finish," said Force. "What we're seeing now in veneering is the ability to get a good joint and good veneered surface at a low cost."

Production guidelines

Major technological advances in adhesives and veneer machinery have produced veneers with excellent seams as far as strength, hiding ability and high quality finishes. But proper guidelines must be followed in order to achieve satisfactory results.

When applying adhesives to the substrate and veneer, careful attention is required because different species have different characteristics. "Different species of veneers expand and contract differently as they absorb moisture from the glue line and as they cure after pressing," said Buchner, "You also have to be more careful with porous veneers like sapele and lacewood which can allow an excessive glue spread to show through the face of the veneer." Proper drying of veneers can help reduce shrinkage because veneers can shrink as much as 10 percent and hardwoods can shrink more, according to Serdio. He said a moisture content of 6 to 8 percent is acceptable.

Problems that occur during the gluing operations require special attention and improper implementation of these guidelines can lead to poorly finished products. According to van Brussel, these problems include delamination, which occurs when the adhesive bond between the veneer pieces fail. Blow out occurs when excessive moisture content in the glue or the veneer (over 18 percent) causes steam to gather under the veneer surface during pressing and blows through the veneer. And telegraphing happens when a foreign material or improperly heated stitched veneer shows through a thin veneer after pressing.

To deal with the shrinking thicknesses of veneers, sanding equipment manufacturers are meeting the veneer sanding challenge by supplying product manufacturers with sanders that are capable of precision sanding. With less material covering the substrate, the sanders can work within millimeters or hundredths of an inch.

Pressing issues

With Europeans using thinner veneers in their product manufacturing, they are requiring lower pressures and temperatures on their veneer presses. "Presses in the U.S. run from 80 to 100 psi, while the current trend in the amount of pressure used in Europe is around 30 to 35 psi and trying to go as low as 15 psi." said Force. "The reason for this is so there won't be any telegraphing through the thinner veneers."

Force also said presses have improved heating systems because temperature controls are now monitored by microprocessors accurate to 1 1/2 degrees of the desired setting.

With proper training and efficient equipment, wood product manufacturers can utilize veneering to meet the demands of customers looking for quality wood products and conserve raw materials for future use. Jerry Lines, project engineer with Globe Manufacturing, commented on the future of supplying lumber by saying, "Recovery in every sense is going to be the key."

Available products

The following is some of the veneer equipment available on the marketplace. For more information, circle the corresponding number on the Reader's Service Card. Another valuable source of information for veneering equipment or veneer species is the WOOD & WOOD PRODUCTS 1991 RED BOOK.

Adwood Corp. offers a variety of Kuper hand-held veneer tools that include the Papertaper which allows the operator to apply paper tape quickly and avoid spots on the veneers. The Kuper hand veneer splicer applies a straight line of glue thread onto veneers and can be applied toward protection of veneer sheet ends, repairing split veneers and patching short faces of fancy face veneers. The mini veneer splicer pulls veneers tightly together and automatically applies a thin line of glue, the company says.

Capital Machine Co. manufactures veneer production equipment including: veneer slicers with blade lengths ranging from 118 in. to 225 in., lathes that are reported to cut as thin as 0.1 mm, clippers that cut from 100 to 1,000 cuts per minute, knife grinders ranging from 76 to 225 in. and veneer hogs that reportedly can cut scrap small enough for sale to particleboard.

Coe Mfg. Co. manufactures various size veneer lathes, Vert-A-Jet veneer dryers, dryer feeder systems, the model 431 knife grinder, the model 777 computerized lathe charger, automatic digital carriage drives. Also offered is the M1380 powered core drive that reportedly increases veneer recovery.

Diehl Machines' VS 81 tapeless veneer splicer is reported to efficiently handle veneer stock regardless of length or thickness. Features include block-link feed chains that hold warped or wavy strips flat and solid steel heater bars that are hard chrome plated to assure wood to wood contact at the glue line.

Duespohl North America's Dup "E" profile wrappers are designed to handle interior or exterior veneer surfacing applications on profiles made of solid wood or composite board.

European Woodworking Machinery offers Torwegge veneer guillotines which feature fully hydraulic drive knife and pressure beam systems. Optional equipment for the machine includes a rear parallel fence, pneumatic lift for the rear fence and an electronic control device.

Force Machinery Co. offers Joos HP series hot presses with automatic brake systems to prevent platen damage. Also available are Mayer FSK fine veneer cutting saws that cut thick and thin veneers splinter free, the company says.

Globe Machine Mfg. manufactures pre-presses that can be installed with variable size glue spreaders, conveying systems and loading and unloading equipment. Other equipment includes knife hogs and veneer recovery systems.

Ruckle Veneer Systems says the MTQ 4000 veneer optimizer is a laser measuring and optimization station that controls face costs and yield, provides reports, centralizes control of the veneer department and cuts raw veneer to length automatically.

Stiles Machinery offers Kuper crossfeed zig-zag veneer splicers which can splice decorative or constructional veneers in thicknesses from 0.4 mm to 2.5 mm. Also offered are Josting EFS veneer jointing guillotines that make straight, neat edges ready for splicing, the company says. Replacement spools of Kuper glue thread for Kuper zig-zag veneer stitching machines are also available.

PHOTO : The Josting EFS jointing guillotine from Stiles Machinery prepares edges for splicing.

PHOTO : Coe Manufacturing Co. veneer lathes are available in a variety of models and sizes.

PHOTO : Capital Machine Co. has veneer slicer blades ranging from 118 in. to 225 in.

PHOTO : Joos HP series hot presses, available from Force Machinery, feature automatic brake systems to prevent platen damage.

PHOTO : Adwood's Kuper 630 mini splicer pulls veneers together and applies a thin line of glue.

PHOTO : The Diehl VS81 splicer can handle strips as short as 6 in. and as thin as 1/64 in., according to the company.

PHOTO : The Torwegge veneer guillotine from European Woodworking features a fully hydraulic drive knife and pressure beam systems.
COPYRIGHT 1991 Vance Publishing Corp.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
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Author:Derning, Sean
Publication:Wood & Wood Products
Date:Jun 1, 1991
Previous Article:Cutting tools: manufacturing's unsung heroes.
Next Article:Diamonds in the rough mill.

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