COATED ABRASIVE PLANING OF ROUGH KILN DRIED HARDWOOD LUMBER. Calvin G. Fye Northwest Hardwoods, Inc. Portland, Oregon

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1 COATED ABRASIVE PLANING OF ROUGH KILN DRIED HARDWOOD LUMBER Calvin G. Fye Northwest Hardwoods, Inc. Portland, Oregon Today we are faced not only with increased costs of the resource but reduced availability as well. As costs continue to climb, the emphasis has changed from how much labor can we save to how much wood fiber can we save? It has become increasingly important for the mill to exert every possible influence to maximize potential dollar value during their conversion processes. We believe abrasive planing is the guarantor that provides that assurance. With that fact in mind, Northwest Hardwoods pioneered the coated abrasive planing of rough kiln dried hardwood lumber in 1972 at their Arlington, Washington operation in conjunction with the Kimwood Corporation of Cottage Grove, Oregon, and the 3M Company of St. Paul, Minnesota. Northwest Hardwoods processes two hardwood species--pacific Coast red alder and Pacific Coast big leaf maple. Currently we are processing in excess of 4 million board feet per month, 95% of which is red alder. The finished volume is abrasive planed, S2S, 1/16" less the nominal thickness, in a thickness distribution of 4/4 through 12/4. The sander installed at Arlington is a four head system that carries a 38" x 103" belt. Each head is powered by a 100 h.p. motor with a belt speed of 8500 s.f.p.m. Using the batch feed system, the average inches of wood at the infeed is 31" or 2.5 b.f.l.f. Usual feed speed is 50 l.f.p.m. for 4/4 8' alder, and l.f.p.m. for 4/4 10' alder (see Table 1). This machine has satisfied the production requirement on a two shift basis, surfacing in excess of 20 million board feet for the year The success at Arlington justified the installation of updated equipment at Centralia, Washington in This is also a four head system, but a larger machine overall. The opposed heads carry a 51" x 103" belt with a belt speed of 9500 s.f.p.m. Power is supplied by two 200 h.p. motors on the primary heads, and two 150 h.p. motors on the secondary heads. Average inches of wood at the infeed is 45" or 3.7 b.f.l.f. I use an adjusted figure of 3.5 b.f.l.f. Usual feed speed is 50 l.f.p.m. for 4/4 8' alder, and 60 l.f.p.m. for 4/4 10' alder (see Fig. 1). This machine has satisfied the production requirement on a one shift basis with an average in excess of 10 m.b.f.h. based on the current mill cut of 85% 4/4 thickness. However, the demand for resurfacing to finished dimension has required the services of a partial second shift. The abrasive used is a synthetic--a variation of aluminum oxide with a hardness of It is basically brown or brown-grey in color with a heavy wedge shape capable of withstanding the impact shock of abrasive planing. Northwest Hardwoods cannot use the full production capability of the Centralia machine because of limitations in the areas of product evaluation and unitizing. However, I believe the 72

2 Table 1 Board Board Board Lineal feet feet feet board Feed per per per Species Size Lgt. footage rate minute hour shift Arlington Machine -- 38" Belt Abrasive Planer Alder 4/4 All ,200 57,540 ft ,000 63,000 II IV ,720 68,040 II 11 VI II ,500 73, II ,280 78,960 II 0 0 If ,000 84,000 Average inches of wood at infeed 557/17401 = 31/12 = 2.5 Bd. Ft. Centralia Machine -- 51" Belt Abrasive Planer Alder 4/4 All ,520 80, ,600 88,200 II II I 1 II ,620 95,340 ft II II 1 t , ,900 If ff 11 If , ,040 II If If It , ,600 Average inches of wood at infeed 45" = 3.7 b.f.l.f. Above figures based on 7 hours per shift. production capability of this machine could satisfy the surfacing requirements of most hardwood surfacing facilities in use today. End usage of the product is directed heavily to the furniture industry. Case goods, custom cabinetry, mouldings, and upholestered furniture framing components are major uses while lesser volumes are used in products such as wall paneling and toy manufacturing. Therefore, we are required to work with moisture content levels in a range of 5% to 10%. It is well to note there is no introduction of degrading or offensive characteristics as a result of the surfacing process. We understand the industry requirements involved with the fabrication of our lumber. We know the exacting demands established on tolerances relative to acceptable moisture content levels. Wood looses its resiliency as the moisture content deteriorates, thus the resistance to the cutting edge increases. It has been determined that hardwood lumber surfaces well at higher moisture content levels with knife planing equipment. Unfortunately, those levels of 12% or higher, conducive to satisfactory surfacing performance, are not acceptable for utilization in the fabrication of furniture. Therefore the average moisture content of 6% required throughout the furniture industry encumbers many knife planing facilities in use today. Perhaps we should look at the kiln drying capabilities throughout the hardwoods industry today and ask ourselves do we consistently produce a product within an acceptable moisture content range that is not only conducive to knife planing, but still within the tolerances established by those involved in fabrication? I would not hesitate to say, "no, we do not." Therefore, on occasion, those using knife planers will receive a portion of their resource that manifest properties not consistent with their desire 73

3 to realize maximum recovery of that resource. Offensive characteristics such as chipping, tear-out, splitting or fracturing can be the result of excessively low moisture content. We have proven abrasive planing will not reflect a deterioration in anticipated yields as a result of surfacing lumber that has been subjected to an over-dry condition. We have failed to identify any degrade as a result of surfacing hardwoods at moisture levels of 5% or below. In short, abrasive planing permits a 100% recovery of the grade yield potential. Northwest Hardwoods, Inc. anticipated a gain in product value with the introduction of this system. At this stage of the game, it would be difficult to assign a number that would be more than a rough approximation. The advantages of abrasive planing for one operation would not necessarily reflect as an advantage for another. The variables are many -- volumes, species, thickness distribution, product marketing and end usage, and costs of installation. If we review the state of the art of hardwood surfacing throughout the hardwood industry today, we can identify extremes from total product acceptance to almost total product destruction. In essence, the knife planed surface can only be as good as the condition of the knife or the attitude or capability of the machine operator. Knife planing by the very nature of using steel inserts, cuts with tooling that is constantly wearing and producing a surface of continual deterioration. At no time after the initial exposure of the product to the cutting edge, will you experience an improvement to the finished surface. Belts do not require special tooling, adjustment or balancing, nor do they require the support activities of tool room personnel. Frequently management fails to identify product degrade as a result of faulty workmanship and they labor under a false image of their product quality and yields. Perhaps a more thorough examination of the surfacing operation would show product losses that contribute substantially but unnecessarily to the overall conversion costs. In short, I believe the product loss is higher than most companies believe because of the inability or absence of competent personnel to evaluate the initial surfacing techniques. Therefore, the advantages of abrasive planing are not identified and the potential gains in dollar value per mbf are not even considered. High priced hardwoods such as red and white oak, black walnut, hard maple, cherry and birch provide substantial volumes directed toward the manufacture of casegoods. We realize the lumber generated from this resource is evaluated by the percentage of clear face cuttings available. A clear face cutting free of inherent defects will not remain of equal value if the cutting manifest defects introduced as a result of improper knife or machine maintenance. Surface characteristics introduced at this time not only reduce the value of the product but reduce the anticipated yield as well. Generally the high grade hardwoods are used in such a manner that both faces are exposed in the finished product so the grades of Select and Better, or 1 Face and Better are the grades where you can least afford to deface the product. Still, we can consider the effect of poor surfacing equipment on a low yield hardwood, an extremely expensive species. Black walnut would be a good example. The 74

4 profusion of defects in the grades of #2 shop and better present an excellent opportunity for a knife planer to develop chipping or tear-out as a result of grain distortion surrounding the defects. Walnut will generally manifest many small defects or other adventitious defects that have a tendency not to surface cleanly. The cutting requirements of walnut have been deliberately minimized to realize the full potential of the species. Abrasive planing of this species would permit you to fully realize the permissiveness of those grade structures. Annually millions of board feet of hardwood lumber suffer reductions in dollar value as a result of fracturing during the surfacing process. The contributors are many--poor stickering, poor unitizing in the green, poor kiln drying practices, or the inability of antiquated machine installations to physically handle the product during the rough dry conversion to a surfaced condition. Abrasive planing of both hardwoods and softwoods virtually eliminates roller split. Northwest Hardwoods has not been limited to surfacing only the species of the northwest. Other hardwoods include: red and white oak, hard maple, yellow birch, ash, cottonwood, black cherry, black walnut and some imported species including teak. All species responded well to the surfacing with no identifiable degrade or roller split. Using the kiln operators manual as a reference we see the specific gravity of red alder listed as Using this species as a reference point, we can list all domestic hardwoods with comparable densities. The extremes of popular cabinetry species reflect basswood at 0.32, yellow poplar 0.40, silver maple 0.44, American elm 0.46, black cherry 0.47, black walnut 0.51, red oak 0.54, yellow birch 0.55, sugar maple 0.56, and white oak So the extremes of basswood at 0.32 to white oak at 0.60 illustrates the variability in density and the increase in difficulty of removing wood fiber as the density intensifies. We have determined with our limited exposure, all domestic species can be processed by abrasive planing without appreciable reduction in feed rates in specific gravity ranges from 0.32 to 0.55 at an average moisture content of 7%. One consideration with regards to the conversion to abrasive planing in the southcentral or eastern United States would be the many species produced or processed in any singular facility. Conceivably, twenty or more species could be handled in any given installation. Therefore, the performance of abrasive planing at various degrees of density would be of considerable concern. If we lump all the so-called soft hardwoods together and say the defect structures are comparable, we find they would fall into a range reflecting densities conducive to abrasive planing. In addition, these species are all prime hardwoods in demand by the manufacturers of custom cabinetry. With today's increased costs of the resource coupled with lower yields of clear face cuttings, a trend is rapidly developing towards utilization of the sound defect structures. Efforts by various hardwood associations throughout the United States have been aggressively promoting the character marked grade structures in the high grade hardwoods and veneers. Their efforts have been rewarded by outstanding customer acceptance. Softwood manufacturers have used the low grade structures for 75

5 years. I recall the big thing in the early 1950's was knotty pine kitchen cabinets, and knotty pine wall paneling. We have demonstrated beyond question the advantages of abrasive planing low grade hardwoods by the acceptance of our character marked grade structure. It is only logical to assume the reduced availability of the high grade resource coupled with higher conversion costs by the end user will force an introduction of the sound defect structure in furniture and other end products where the character marked defect has previously been rejected. In the very near future abrasive planing will permit a utilization of the low grade resource throughout the domestic hardwood species not realized before by the furniture industry. Because of the prevailing defects and the high risk of yield loss as a result of grain distortion surrounding the defects, perhaps the lower grades are best served by the abrasive planing process. A prime influence behind the decision to enter into the process by the major softwood producers is the capability of higher resource realization, simply by reducing the green product dimension. This brings us into the area of precision sawing and the potential of increased over-runs. Using the batch feed system, precision sawing is not a requirement in abrasive planing. Precision sawing merely compliments the system by increased resource recovery, increased feed rates through the machine, and longer belt life, thus lower costs per MBF. Unfortunately some systems in use today are not gaining the advantages of precision sawing for one reason or another, but it is the intent of companies developing the latest installations to realize the full potential of their investment. Northwest Hardwoods frequently reruns products to a finished dimension for special accounts. A substantial percentage of that volume is high grade lumber where the product is used in a two face exposed situation. Therefore, the quality of surfacing is critical to assure a total product utilization. Abrasive planing has provided the assurance we can resurface to any finished dimension without fear of any product loss below the established yield of the input volume. Although we realize the full recovery of the grade yield potential in our initial conversion process of surfacing to 1/16" less the nominal thickness a substantial volume of the high grade lumber is re-introduced by the customer to poorly maintained or antiquated knife planing equipment, thus the introduction of many degrading characteristics. In this case, the benefits of abrasive planing are lost beyond the initial surfacing of the product. The major and significant differences between knife planing and abrasive planing lie in the areas of surface finish integrity and consistency. It is difficult to identify any negative qualities of abrasive planing which would contribute to a deterioration of the surface or product abuse. Abrasive planing effects a blending of grain and defect structures that enhance not only the appearance of the piece, but which maximizes the full potential of the product during the remanufacturing process. The 3M Company began research in abrasive planing over twenty years ago, but it was not until 1962 that the first abrasive planer appeared in the finish department of a case goods manufacturer. Today virtually all manufacturers employ abrasive 76

6 planers of some configuration throughout their plants. However, it was not until Northwest Hardwoods entered the picture in 1972 that any attempts were made to surface rough kiln dried hardwood lumber. Table 2 lists all production surfacing operations in use as of this writing. As is typical, the softwood manufacturers have exhibited more aggressiveness in pursuing the potential of the process. True enough, the list is not impressive by number and in only the past year have gains been identified in acceptance of the system by the inclusion of large volume softwood producers. Pulaski Furniture Pulaski, Virginia (Two plants) Table 2 Hardwood Conversion -- Abrasive Planing Anderson Tulley Vicksburg, Miss. Memphis, Tenn. Hardwood truck flooring Two head system Arkansas Oak Flooring Little Rock, Ark. Hardwood truck flooring Two head system Louisiana Pacific Oroville, Calif. Masonite Corporation Laurel, Miss. (Finger joint line) Louisiana Pacific Samoa, Calif. Finger Joint Profiler Source: 3M Company Hamer Lumber West Virginia Hardwood truck flooring Two head system Veach May Wilson Knoxville, Tenn. Hardwood truck flooring (Two lines) Two head system Northwest Hardwoods, Inc. Centralia, Washington Arlington, Washington Softwood Conversion -- Abrasive Planing American Forests Products Stockton, Calif. Remanufactured Ponderosa Pine Weyerhaueser Corporation Klamath Falls, Oregon Eight head system Upper grade Ponderosa Pine Crown Zellerbach Omak, Washington Finger Joint Profiler It is just a matter of time and in the very near future, the major furniture manufacturers of the northeastern and southeastern United States will realize the benefits of abrasive planing and the conversion process will begin. Table 3 shows the production capability of a batch feed system surfacing softwoods using a 51" belt. These volumes, if realized, are reliant on the support equipment to handle the product ahead of and behind the machine. 77

7 Lumber Width Number pieces in 50" batch Lineal Feet 4/4 Board Feet 5/4 " It 6/4 " 8/4 'I 'I Table 3. Production Rates -- Kimwood Corporation , , , , , f.p.m. Batch Lumber Sander 6" Lumber Width 4" 8" 10" 12" Number pieces in 50" batch Lineal Feet 1,014, f.p.m. Batch Lumber Sander 4" 6" 10" , , , , , , , , , , , , , , ,500 12" 624, , , , , , , , ,000 4/4 Board Feet 338,000 5/4 " " 422,500 6/4 " 507,000 8/4 " 676, , , , , , , , , , , , , , , , ,000 Note: The above board fe et figures are based on 6-1/2 hours production per shift. Although we have discussed primarily the conversion of hardwood lumber almost without exception all considerations are applicable to the softwood species. Our obligation as dry kiln people is to investigate the potentials of abrasive planing and thoroughly understand its influence on our responsibilities to present a product compatible with the capability and intent of the system. We should become totally involved not only with the drying functions but the primary techniques of stickering and unitizing. The potential of precision sawing to a lesser green dimension does afford an opportunity for the kiln operator to be less attentive to his schedules or final moisture content. Even though I stated earlier, abrasive, planing virtually eliminates roller split in all species, this does not imply the excessive shrinkage as a result of over-dry will permit the surfaced product to surface cleanly and meet the grade requirement. We are plagued with distortion in our kiln dried lumber. This is a result of many contributors, some beyond our control. For the most part we have varying degrees of difficulty in processing that portion of the product through conventional surfacing equipment. Abrasive planers using the batch feed system, generally handle these problem pieces with ease, without expensive jam-ups or down time. Obviously this is a consideration in the processing of high grade hardwoods or softwood dimension. 78

8 Perhaps the kiln operator should appreciate this benefit in the sense that perhaps he will be critized to a lesser degree and hopefully his position will be enhanced by the identifiable gains in grade recovery and over-all product realization. I do not pretend to defend the kiln operators, but all too frequently they are the receipients of harsh, unjust comments by other personnel unfamiliar with the complexities of their obligations. Yes, we can identify some pluses and some minuses in the abrasive planing kiln drying relationship, but I believe the scales are tipped heavily in favor of this new born child. The growth will be rapid as the process gains exposure throughout the lumber industry. In conclusion, let me say that although abrasive planing is perhaps in its infancy, the gains made in planer design improvement, and the gains made in abrasive belts have permitted these people to present to us a production piece of equipment with a return on the investment that will be a very bright spot in our future economy. 79