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Automated lumber processing: a glimpse of the future.


Combining state-of-the-art computer scanning and laser machining with conventional rough mill technology, researchers at Michigan State University say they have developed an advanced system for optimizing lumber yields to previously unheard of levels. ALPS, an acronym for Automated Lumber Processing System, is a broad conceptualized research and development program to fully automate lumber processing from primary log breakdown to secondary remanufacture of lumber into furniture and dimension parts. The goal of this automation is to eliminate human decision and manual labor in maximizing wood yield and value of lumber and dimension products.

The method we have worked with incorporates available new technology, including a machine vision system to locate and identify defects -- both external and internal -- within lumber. This information is used to position the workpiece and with the computer, direct the laser machining sawing pattern to achieve maximum recovery of the lumber.

Importance of ALPS

Yields of 40 to 60 percent are common in the furniture and dimension industry using graded hardwood lumber. There are a host of factors that influence yield, but the most important ones are the grade of lumber, the quality and size of the required part, human fatigue, the operator's decision-making ability and the limitations of the processing equipment that is used.

Studies have shown that actual defective areas such as knots, wane, etc., of the lower lumber grades are quite small in comparison to expected yields. The percentage of defective areas for No. 3 Common is 13 percent; No. 2 Common, 8 percent; and No. 1 Common, 5.5 percent. Yields of clear parts for the same grades may be 45 percent, 55 percent and 60 percent, respectively, depending on a combination of factors.

Examining the potential for yield improvement in the No. 1 Common grade indicates that if the yield were 60 percent and there is only 5.5 percent of actual defective area, there would be 34.5 percent clear material that is wasted, usually because it has been cut into smaller pieces than desired. Five to 8 percent of that waste is sawdust. Thus, if we could decrease the kerf, we would automatically improve yield. The real challenge is to develop a new cutting method that will only take out desired parts of the board without cutting into other parts that may also be useful.

In conventional cutting of lumber, the practice is to cross cut and rip, in either sequence, into defect-free rectangular pieces of the desired size using circular saws. The initial selection of a clear part and either cross cutting or ripping first will necessarily make shorter or narrower clear areas available for subsequent parts selected.

The only perfect way to maximize yield and still produce the size parts we want from graded lumber would be to "cookie cut" or "punch out" the pieces we want out of the available clear area without having a circular saw cut from one side to the other or from one end to the other end of the board. Ultimately, if curved parts are needed in a more advanced ALPS, they would be nested together to get the desired part without first producing wasteful rectangular pieces.

Recent progress of ALPS

Since 1982 a number of research projects involving the ALPS concept have been initiated. Most recently we have built or purchased prototype equipment for demonstration and research for the Michigan State University High-Energy Laser Processing Laboratory. This prototype, which is being used to test the complete system in real time and run tests applicable to factory conditions, includes surface scanning equipment designed by Dr. Klinkhachorn that will locate and determine defects, a computer-controlled device for accurately moving and positioning a full length board having a maximum length of 16 feet by 18 inches wide and high-energy C[O.sub.2] lasers providing a choice of a 3,000 or 600 watts for cutting or etch marking the board.

The computer software working in conjunction with vision equipment recognizes lumber defects, accepts furniture part cutting orders and optimally positions the location of these parts in the clear areas of the board. It then directs the laser to efficiently cut parts and is interfaced with the three pieces of equipment -- the laser, the board positioning machine and the vision camera -- to form ALPS. Additionally, a program to grade the board can be incorporated into the system.

Economic feasibility

All of the studies conducted to date have shown ALPS to be economically viable. The best economic returns measured by IRR (Internal Rate of Return) and NPV (Net Present Value) come from using higher value species and larger operating units. The ALPS program has probably had more economic consideration than most research projects.

With continued study and rapid developments in robotics, machine vision, computer and laser technology, the future of ALPS is not in question, only the time needed for implementation.

As of 1990, there were a number of lasers used in the U.S. wood industry for manufacturing die boards, fancy furniture parts and novelty cuttings and engravings. They have not yet been used for cutting furniture parts from solid lumber and the power they typically use is relatively low, in the 40-800 watts range, instead of 3,000 watts used by ALPS. The cost and physical size of laser equipment has been reduced substantially and the capability and power has increased in a manner similar to computers so the future of laser use in wood processing is very promising.

ALPS' implication for oak

The ALPS program presents several important implications for oak lumber. In the two factory tests we achieved an average yield improvement of 13.44 percent. Given conventional production yields of 69 percent, a 13.44 percent increase would mean 16.3 percent less lumber would be required to produce parts. If the same level of product were required, this provides a tremendous saving of the oak resource. Since lumber is the largest cost item in dimension production, ALPS could significantly lower that cost and could change the market. Secondly, it could change the lumber grade required for use.

Since No. 2 Common oak lumber is almost one-half the cost of No. 1 Common oak, a production facility could achieve a greater economies by lowering the grade rather than by increasing the yield of a higher grade. Considering there is more No. 2 Common oak available and lower grade logs produce more No. 2 Common grade, the oak resource would be further extended.


A great deal of wood industry interest in the ALPS program has been generated. The three essential elements of ALPS (machine vision, computer directed optimal part location and laser wood cutting) have all progressed at a very rapid pace in the last three years and prototype equipment is now available.

The computer programs have reached the degree of development suitable for commercial use and will be used with the prototype equipment. Both machine vision for lumber defect location and identification, and laser cutting of wood are in the prototype equipment state. Now, direct industry involvement is needed and welcomed. Various aspects of our research and development program will continue in the next few years, but the time when the ALPS system is finally ready for industry use will depend on the combined effort of both woodworking manufacturers and machinery suppliers.

Initial industry adoption of ALPS may well be in a specialized area or for a limited product of high value such as oak processing. Only by using the new technology that is available today can our industry hope to compete in the '90s.

PHOTO : ALPS' camera vision system, above, scans a board for defects. A computer then directs the high-energy laser to "cookie cut" the defect, maximizing lumber yields.

Henry Huber is professor emeritus, Department of Forestry, Michigan State University, East Lansing. Powsiri Klinkhachorn is an associate professor, Department of Electrical and Computer Engineering, West Virginia University, Morgantown.
COPYRIGHT 1991 Vance Publishing Corp.
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Copyright 1991, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Author:Klinkhachorn, Powsiri
Publication:Wood & Wood Products
Date:Sep 1, 1991
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