Key Characteristics of Solid Wood Materials by Secondary Wood Products Manufacturing Segment

Transcription

1 Key Characteristics of Solid Wood Materials by Secondary Wood Products Manufacturing Segment JOHN PUNCHES 1 OREGON STATE UNIVERSITY DEPARTMENT OF WOOD SCIENCE & ENGINEERING MARCH 6, 2002 Manufacturers of secondary wood products use solid wood in a variety of applications. In each application, solid wood must meet performance criteria related to the customer s expectations (generally related to appearance) and the manufacturer s design and manufacturing process. Case studies (including site visits and personal interviews) of 53 secondary wood products companies conducted between 1999 and 2001 identified characteristics important in solid wood applications in each of five industry segments. Characteristics of solid wood materials necessary in particular products, including specific information about the defects or character marks allowed, were determined. Raw material species and grades were identified, as were the products intended uses, finishes, and mechanisms of fastening. Performance criteria included: Appearance Characteristics: Uniform Color, Specific Grain Pattern, Presence of Burl, Heartwood or Sapwood Grain Characteristics: Fine Grain, Vertical Grain, Straight Grain Physical/Mechanical Characteristics: Strength (low, medium, high), Texture (fine, medium, coarse), Surface Hardness, Density, Abrasion Resistance, Shock Absorbance, Stability (low shrink/swell), Straightness (low warp, crook, bow, twist) Drying Characteristics: Dries Quickly, Dries Easily, Dries with Minimal Degrade Machining Characteristics: Cuts Well, Edges Well, Surfaces Well, Sands Well, Steam Bends Well, Fingerjoints Well Allowable Defects: Pin Knots, Sound Knots (by size), Loose Knots (by size), Wormholes, Stain, Discoloration, Pith, Gum/Pitch Pockets, Wane, Bark Pockets, Surface Checks, End Splits Results, listed below, are stratified by industry segment and type of application. Drying characteristics are not included, as only one of the case study companies (a flooring manufacturer) dried its own wood raw materials. In this report, the category natural appearance applications includes products that, following assembly or installation, will be visible and be finished with stain, clear finish, or no finish at all. Painted applications includes products that will have an opaque finish. Hidden/structural includes components that will be covered by other wood, upholstery or laminate, or will otherwise be hidden from view in the completed application. The information reported provides insights into how the secondary wood products industry uses solid wood and the characteristics it requires in broad categories of applications. It is qualitative at best, and should not be assumed to represent the average company in any particular category or to accurately represent every company in any particular segment. Wood use and acceptable wood characteristics vary widely among industry segments, individual manufacturers, and specific products. 1 John Punches. Associate Professor. Department of Wood Science & Engineering. Oregon State University. Stationed at: Douglas County OSU Extension Service SE Douglas Ave., PO Box Roseburg, Oregon, Phone: Fax: john.punches@orst.edu.

2 Architectural Millwork Uniform color is critical in natural appearance millwork applications. Either heartwood or sapwood is specified, depending on species. Grain pattern and/or orientation (plain/quarter/rift) is specified in many applications. Occasional pin knots are allowed by most manufacturers, otherwise material is essentially free of defect. Gum/pitch pockets are allowed in most cherry applications. Larger knots are allowed in knotty pin but otherwise excluded. Architectural Woodwork Institute (AWI) standards tightly proscribe allowable defects in millwork (along with other characteristics including flame spread rate). Stability and straightness are critical, and material may need to be hard enough to resist denting. Manufacturers prefer species that cut, edge, surface and sand cleanly, but customers or architects typically specify species and manufacturers must tailor processes accordingly. Steam bending appears to be infrequent, and fingerjointing extremely uncommon. Mechanisms of fastening include glue (very common), dowels/pegs, screws, staples/pins, and to a lesser extent biscuits, nails, mortis and tenon, and a variety of specialized systems. Commonly utilized species include hard and soft maple, red and white oak, cherry, walnut, mahogany, and yellow-poplar, in FAS or higher grades and eastern white pine in equivalently high grades. Color and grain are not critical in painted millwork applications. Manufacturers often seek fine textured species that will take paint well and finish smoothly. Pin knots are allowed, as are stain and discoloration provided they will not show through the finish. Small, tight knots and other small defects that can be filled and will not show through the surface are tolerated by many manufacturers. Loose knots, decay, wane, pith, bark pockets, large wormholes and end splits are rarely tolerated. Stability and straightness remain critical, and material may need to be hard enough to resist denting for specific applications. Manufacturers prefer species with good overall machining characteristics, but often must tailor processes to species dictated by a customer or architect. Fingerjointing appears to be rare. Mechanisms of fastening are the same as noted for natural appearance applications. FAS yellow-poplar and soft maple are commonly purchased for painted millwork, but much is produced from falldown from higher grade products. Hidden/Structural Applications Color and grain appearance are not important in hidden millwork applications. Pin knots are allowed, but other knots may be excluded. Other defects are typically allowed as long as material is sufficiently solid to perform structurally and/or as a fastening medium. Materials must be straight and stable for most applications. They must cut moderately well, but other machining characteristics are of lesser importance. Hidden materials are more likely to be fastened with screws, staples, pins, or nails than in appearance or painted applications. Poplar is a common species in hidden applications, and its source is generally falldown from other products. Construction lumber is used for general framing, and plywood is used under panels and, increasingly, ripped and glued up to serve in place of construction lumber. Moulding Uniform color is critical in natural appearance moulding applications. Heartwood or sapwood will be specified depending on species. Uniform and/or straight grain is important to some manufacturers. Pin knots are generally allowed. Occasional, larger knots are allowed by some manufacturers, although they are likely to be cut out by the installer. Most manufacturers avoid other defects, but a few allow minor stain or discoloration, gum/pitch pockets in cherry, and occasional small wormholes. More frequent and larger defects are allowed on the back. Straightness is very important and stability is important to some manufacturers. Dent resistance Punches, page 2

3 may be desired for some applications. A clean, smooth surface is required in the finished product, but species is often dictated by the customer and manufacturers must tailor their machining processes to the species. Staples/pins are the most common mechanism of fastening. Glue is also common, and screws are used occasionally. Red oak, maple, cherry, yellow-poplar, eastern white pine, ponderosa pine and hemlock are common species. Grades are typically high, including FAS for hardwoods and D and Better or shop grades for pine. Color and grain need not be uniform in painted millwork. Fine textured species may be preferred for a smooth, painted surface. Pin knots are generally allowed, and stain and discoloration are allowed if they can be covered by the finish. Some manufacturers tolerate tight knots and to a lesser extent wormholes, pith, and surface checks as long as they can be puttied and finished smooth. Straightness is very important. Stability is important to many manufacturers. Dent resistance is important in some applications. Manufacturers prefer materials that cut, edge, surface, and sand well, but species are typically dictated by the customer. Some fingerjointing is done in painted moulding. Staples/pins are the most common mechanism of fastening. Glue is also used, as are nails and occasional screws. Yellow-poplar is preferred for many painted mouldings, and is frequently purchased as FAS for higher grade products and the falldown used in this application. Much painted moulding is produced from MDF. Doors & Windows Uniform color is critical in doors and windows. Either heartwood or sapwood will be specified, depending on species, and wild grain patterns will usually be avoided. Windows often require straight grain, and where Douglas-fir is employed it will generally be sawn to have vertical grain and a minimum ring count may be specified. Occasional pin knots are allowed in most door and window applications, but other defects are rarely tolerated. Some manufacturers and/or applications utilize only defect-free material. Wood used for doors and windows must be straight and reasonably stable. Dent resistance may be in issue in some applications, and decay resistance is necessary for exterior use. Preservative treatments may be employed to enhance decay resistance. Manufacturers prefer species that cut, edge, surface and sand well, but tailor their processes to the species dictated by their customers. Steam bending and fingerjointing appear rare in these applications. Mechanisms of fastening include gluing, dowels/pegs, screws, staples/pins, mortis and tenon, and nails. Common species for windows include ponderosa pine, eastern white pine, radiata pine, and Douglas-fir (vertical grain) in very high grades (e.g., highest export grades or sorts exceeding FAS). Exterior doors are typically produced of eastern white pine, mahogany, white oak, and Douglas-fir, while interior doors employ a broader range of species. High grades such as FAS (hardwoods) and D and Better (pine) are common for doors. Color and grain uniformity are not important in painted door and window applications when the entire component is painted or hidden. (Many components, particularly in windows, have only one surface painted and the other remains visible. In these cases the requirements of the natural appearance application take precedence.) Manufacturers may prefer fine textured species that will yield a smooth painted finish. Pin knots are generally allowed. Stain and discoloration are allowed where they can be successfully covered by the finish. Very minimal other defects are generally tolerated, but they must putty and finish smooth. Material for these applications must be straight and smooth, and dent resistance is desired in some applications. Machining and fastening requirements differ little from natural appearance applications. Yellowpoplar, ponderosa pine, radiata pine, and eastern white pine are employed in their high grades, along with some fingerjointed stock and falldown from other products. Punches, page 3

4 Hidden/Structural Applications Doors and windows utilize glued-up components primarily for the purpose of improving stability and ensuring straightness of the finished product. This leaves the cores of flat-panel doors and parts of doorjambs, stiles, and rails hidden from view but playing critical roles in the product s performance. Color and grain appearance are not important in these applications. Pin knots, stain and discoloration are generally allowed. Acceptance of other knots varies among manufacturers and products. Other defects that will not show through a surface veneer or otherwise negatively impact performance are typically allowed. End splits are not tolerated. Straightness is critical, and conditioning (lack of tension) is important to ensure material remains straight in the remanufacturing process. Stability is important, but is addressed in the design of glued-up components. Good machining properties are necessary, as flat surfaces are needed for gluing. Glue, dowels/pins, screws, staples, pins and nails are common fastening mechanisms. Many species of pine, plus fir and hemlock, are commonly employed in these applications, in grades of #2 and #3 Common. Fingerjointed material is also employed, along with composites such as laminated veneer lumber and laminated strand lumber. Furniture Uniform color is critical in natural appearance furniture applications, particularly those with light colored finishes. Heartwood or sapwood will be specified, depending on species. Grain pattern and/or orientation (quarter, rift, or plain sawn) may be specified in some applications. Slope of grain is important in structural applications (e.g., frames and legs). Pin knots are allowed in some applications. Gum/pitch pockets are allowed in cherry, and knotty pine allows large, sound knots and pitch pockets. Other defects are excluded in nearly all applications. Straightness and stability is important in most applications. Legs and frames require reasonably high strength material. Impact resistance may be an issue in legs. Manufacturers prefer species that have good overall machining characteristics, but must often tailor their processes to species dictated by customers. Fastening mechanisms include glue, dowels/pegs, screws, staples/pins, some biscuits and dovetails, mortis and tenon, and a variety of special fasteners. Species common in these applications include hard and soft maple, yellow-poplar, red oak, ash, mahogany, walnut, and eastern white pine in FAS, #1 and #2 Common, and Select and Better grades or the pine equivalents. Color and grain are not critical in painted furniture applications, as long as a uniform finish can be achieved. Requirements for painted furniture applications are otherwise nearly identical to those for natural appearance furniture applications. Only minimal defects are tolerated and requirements for stability and other mechanical/physical properties remain unchanged. Yellowpoplar and maple are common species for painted furniture components. They are purchased in a range of grades. Falldown from natural appearance products is also employed. Hidden/Structural Applications Color and grain appearance is not important in furniture s hidden applications. Slope of grain is often a key consideration. Pin knots and some sound knots, stain and discoloration are generally allowed. Some applications allow other defects as long as they are sound. Defects must not interfere with fastening or otherwise negatively impact performance. Thus, some hidden applications (including portions of furniture frames) will allow only stain and discoloration and exclude all other defects. Straightness and stability are key considerations, and strength is important in many applications. Some applications limit wood density to ensure successful stapling. Screw holding capacity is important in some applications, and impact resistance is important in leg components. Good cutting characteristics are desired. Other machining Punches, page 4

5 characteristics are typically of less importance. Fastening mechanisms are consistent with those employed in natural and painted applications. Yellow-poplar and maple are commonly utilized in these products, often gleaned from falldown from higher grade products. If purchased, it is typically of FAS or #1 Common grade. Many hidden furniture components are manufactured from plywood, which is favored for its uniform strength and stability. Cabinets Uniform color and grain are critical in natural appearance cabinet applications. Many manufacturers sort material to match color and grain within individual assemblies. Heartwood or sapwood will be utilized depending on species, and grain orientation may be specified. Pin knots are allowed by most manufacturers. Gum/pitch pockets may be tolerated in cherry. Other defects are rarely tolerated. Some manufacturers exclude all defect, using perfect material. Significantly more character is allowed in rustic grades or species known for their variation (e.g., hickory or knotty pine). Material must be straight and stability is desired. Some manufacturers consider dent resistance when choosing materials. Good cutting, edging, surfacing and sanding characteristics are desired, but manufacturers tailor their processes to the species dictated by their customers. Primary mechanisms of fastening include glue, screws, staples/pins, and to a lesser extent dowels/pegs, biscuits, and mortis and tenons. Red oak, white oak, maple and cherry are perhaps the most common cabinet species, but many other species are employed at customers requests. Light colored species are currently in vogue. FAS and 1 Common raw material grades are commonly utilized, often with additional restrictions on color variation. Color and grain appearance is not important in painted cabinets. Pin knots are allowed, and stain and discoloration are accepted as long as they do not show through the product s finish. Other defects are typically excluded unless they can be puttied smooth. The manufacturer s objective is a smooth, uniform surface. Material must be straight and may require dent resistance. Machining requirements and fastening mechanisms mirror those of natural appearance cabinet applications. Yellow-poplar, maple, and alder, (mostly in the #1 Common or equivalent grade) are employed, along with falldown from higher grade products. MDF is used extensively for painted, veneered, or laminated cabinet panel components. Hidden/Structural Applications Hidden applications in cabinets include glue/fastening blocks and various structural braces. Appearance is not important the components need only serve adequately as supports or points of fastening. Defects that would interfere with their performance are not allowed. These components are typically produced from plywood or falldown from other products. Flooring Solid Wood Solid wood flooring is available as strip, plank or parquet products (differing primarily in piece size) and in four generally accepted grades. High density, dent resistant species are best suited to flooring applications, but almost any species is utilized at customers requests. Straightness and stability are important. Abrasion resistance is achieved through finishing. Manufacturers prefer species with good machining characteristics, but tailor their processes to the requested species. Thin flooring (1/2 or less) is commonly glued down, while standard thickness flooring is pinned or nailed. Red and white oak, maple, cherry, ash, and walnut are common flooring species, and manufacturers generally purchase these materials in FAS to #2 Common lumber Punches, page 5

6 grades. Flooring grades are defined by industry organizations, but there are also many proprietary grades. The top grade (Clear) is extremely uniform in color and virtually defect-free. Grain orientation (quarter, rift or plain) is often specified. Flooring s second grade (Select) allows some variation in color, including natural variation between heartwood and sapwood and very limited amounts of stain or discoloration. Defect is still very limited, but generally includes pin knots and limited numbers of very small tight knots. Some manufacturers allow small wormholes and minor surface checks. The third grade (1 Common) includes a mixture of color and grain appearance, pin knots and larger sound knots, small loose knots, wormholes, incipient decay, stain, gum pockets, wane on back edges, partial tongues, small bark inclusions if solid, short splits, and surface checks. The fourth grade (2 Common or rustic) allows wide variation in color and grain and almost any defect. Wood Composite Composite flooring utilizes a sliced or peeled veneer face on a plywood core. It generally has the appearance of a Clear or Select solid floor. It may be prefinished or impregnated with plastics to assure surface durability. Good machining characteristics are desired. Most composite material is glued down, or may attach only to adjacent pieces and float over a substrate. Oak, maple, ash, and cherry are common, but many other species are utilized. Appearance layers are typically produced from high quality lumber or thick veneers. They allow some pin knots (slightly larger in some products) but are otherwise clear. Miscellaneous Solid Wood Products Several products encountered in this study do not fit neatly into one of the five major categories described above. These miscellaneous products include trophy bases, plaques, small display cases, educational unit blocks, butcher blocks, caskets and casket parts, edge-glued panels and laminated squares, and decorative inlays for wood floors. Each of the products is intended for appearance applications with stained or clear finishes, or no finish at all. Uniform color is thus of key importance. Grain orientation may be specified. Most applications allow little or no defect, although as with other products gum/pitch pockets are typically allowed in cherry and knots in knotty pine. Straightness is important in nearly all applications stability to a lesser extent. Surface hardness is important in some applications. Abrasion resistance, where needed, is achieved through the finish applied. Educational unit blocks require wood of fine texture that will not splinter. Good overall machining characteristics are typically desired, but customers often dictate species and manufacturers adapt accordingly. Gluing is the most common mechanism of fastening, but many others are utilized as well. Maple, cherry, walnut, yellowpoplar and eastern white pine are commonly employed for the products encountered, and manufacturers utilize high grades of raw material (FAS or equivalent) Oregon State University. Not to be published or distributed without the author s express permission. This publication was produced and distributed in furtherance of the Acts of Congress of May 8 and June 30, Extension work is a cooperative program of Oregon State University, the U.S. Department of Agriculture, and Oregon counties. Oregon State University Extension Service offers educational programs, activities, and materials without regard to race, color, religion, sex, sexual orientation, national origin, age, marital status, disability, and disable veteran or Vietnam-era veteran status as required by Title VI of the Civil Rights Act of 1964, Title IX of the Education Amendments of 1972, and Section 504 of the Rehabilitation Act of Oregon State University Extension Service is an Equal Opportunity Employer. Punches, page 6