A common challenge related to hardwood plywood is checking along the grain of face veneers. This study tested the hypothesis that face checking of rotary peeled maple veneer plywood will be greater on the loose side of the veneer and that checking will be reduced by the application of a clear film-forming finish. Fifteen panels were constructed with the tight side of the face veneer oriented out (i.e. exposed to the atmosphere) and 15 with the loose side of the face veneer oriented out. Half of each panel was finished with lacquer and the other half left unfinished. Panels were conditioned in a hot, wet chamber, visually inspected, and then inspected again after conditioning in a hot, dry chamber. Contrary to conventional wisdom, panels oriented with the tight side of the face veneer oriented out checked significantly more than panels with the loose side oriented out. There was no effect due to finishing. Because these findings are contrary to established practices, further investigation is warranted.

Nondestructive commercial ultrasonic grading provides laminated veneer lumber (LVL) manufacturers a means for sorting veneer based on average ultrasonic propagation time (UPT) and/or average dynamic modulus of elasticity (MOE d ). However, little is known about the influence of veneer defects on strength properties of veneer and LVL. Including veneer defect and growth ring pattern measurements, obtained via optical scanning, was hypothesized to improve LVL static tensile strength (F t ) property predictions. Nondestructive and destructive testing of Douglas-fir ( Pseudotsuga menziesii ) veneer and LVL was performed to evaluate improvements in LVL F t property predictions. Various models based solely on density, optical, ultrasonic, and combined system measurements were developed for LVL property predictions. LVL static F t was best predicted ( R 2 1/4 0.65) with integrated optical and ultrasonic measurements (ie combined system model), which included average defect, growth ring pattern, and MOE d measurements from the LVL material. Results suggested improved LVL F t predictions could be achieved by integrating ultrasonic and optical systems. Additionally, the optical model, which included average defect, growth ring, and density measurements, better explained the variation in LVL static F t values ( R 2 = 0.58) compared with the MOE d ( R 2 = 0.51) and UPT ( R 2 = 0.31) models.

This paper examines how 11 part-families were developed and then selected, using discrete event simulation, for cell manufacturing and subsequent exclusion from the current manufacturing system of a value added wood products company. The criteria used to exclude a family were the reduction of current average work-in-process and, secondarily, average lead times. The excluded parts could then be processed through a manufacturing cell. Using simulation and management input, two of 11 part-families, representing 51 different part types, were chosen to be excluded from the traditional job shop floor. Their exclusion resulted in an average total work-in-process reduction of 112 parts which represented a 17% reduction. A second article, in preparation, will compare the processing of the 51 parts through different simulated manufacturing cell designs.

Birch lumber is often characterized by a high degree of knots, bark pockets, heartwood, and other features which force sawmill owners to decide whether to edge and trim boards to produce standard grade lumber vs. proprietary grade character-marked lumber. In addition, the edging strategies used with irregularly shaped flitches can greatly influence cut-stock recovery. To investigate this recovery, 143 kiln-dried 4/4 birch flitches were obtained from a sawmill-in south-central Alaska and evaluated by a National Hardwood Lumber Association (NHLA) grader for board grade and lumber tally. Each flitch was marked by the lumber grader, indicating where the board would be edged to produce NHLA grade lumber in a production setting. The flitches were transported from Alaska to Oregon State University where they were scanned to produce digital board data. These data were then processed with the computer simulation program CORY (Computerized Optimization of Recoverable Yield) to estimate the cut-stock yield for various levels of edging severity and sound feature (character mark) inclusion.Four edging strategies were evaluated, ranging from unedged (least severe) to wane-free (most severe). As expected, cutting area recoveries and cutting yields were reduced as edging severity was increased. In many cases, however, these differences were minimal. Cutting yields for clear parts were 21.1, 23.7, 26.2, and 27.1 percent for wane-free, actual, light, and unedged strategies, respectively. Cutting yields for parts that included sound character features increased by more than double to 44.0, 49.0, 52.7, and 54.0 percent for wane-free, actual, light, and unedged strategies, respectively. These results indicate that finding value-added alternatives for this character-marked birch might prove profitable for some Alaskan sawmills that also produce secondary products such as cabinets and furniture or supply cuttings to these manufacturers.

Current raw material characteristics and industry practices contribute to manufacturing rougher softwood veneer with varying annual ring and lathe check characteristics. However, questions exist about how these characteristics influence plywood gluebond quality. This study's objectives were to determine which veneer roughness, lathe check, and annual ring characteristics affect Douglas-fir (Pseudotsuga menziesii) plywood gluebond quality and whether these characteristics could be used to predict gluebond quality. Veneer sheets were separated into smooth, intermediate and rough visual categories. Mathematical surface roughness was determined for randomly selected areas using a laser scatter/optical imaging system. The scanned veneers were used as center ply material in three-ply panels. Lathe check and annual ring characteristics were measured from optically scanned images. Plywood gluebond specimens were evaluated for percent wood failure and load at failure. Statistically significant differences existed between visual roughness categories for both average percent wood failure and load at failure. Regression analysis indicated that percent wood failure and load at failure were influenced by different surface roughness, lathe check, and annual ring measures. While the regression models did not produce reliable predictions of gluebond quality, they did provide information on which veneer characteristics are most important from a manufacturing standpoint. In particular, percent wood failure can be increased by reducing veneer roughness, and load at failure can be increased by reducing the number of lathe checks per inch.

To evaluate the influence of various preparation conditions oil standard Douglas-fir (Pseudotsuga menziesii) plywood gluebond specimen performance, tests were conducted on samples in wet boiled and dry states and kerfed such that opening and closing of lathe checks occurred under each conditioning method. Each factor and combination of factors had statistically significant influences Oil load at failure but not percent wood failure.

The availability of quality flitches for the moulding and millwork industry has decreased, resulting in increased veneer prices. This project investigated the feasibility of using serpentine-end-matched (SEM) joined material for veneer flitches. Eighteen ponderosa pine (Pinus ponderosa Dougl. ex Laws.) veneer flitches were randomly selected and crosscut into paired samples. The samples were then crosscut and machined with SEM joints such that one sample of a pair received a joint with the amplitude equal to its width while the other received a joint with the amplitude equal to two-thirds of its width. The joints were then glued together with a cross-linking polyvinyl acetate adhesive, cured, and sliced into three veneer thicknesses, 1/16 inch (1.6 mm), 1/12 inch (2.8 mm), and 1/8 inch (3.2 mm), using typical industry processes. The flitches produced 468 veneers, only 14 of which had bonds that failed during manufacturing. The veneers from 14 flitches were also tested in tension for ultimate load and failure mode. No significant differences in stress levels were found among veneer thicknesses or failure modes, or between joint designs. Partial wood failure occurred in 69 of the 107 veneers analyzed. The average wood failure involved approximately a third of the joint and typically occurred anywhere along the glueline except at the joint apex.

A changing raw material supply and smaller, generally lower quality logs, are resulting in an increase in undesirable surface characteristics in veneer, such as roughness, that can adversely affect plywood glue-bond performance, The typical response by plywood manufacturers is to increase the adhesive spread rate and press pressure when using rough veneer, but the effectiveness of this technique has not been verified. One problem has been understanding the role surface roughness and lathe checks play in defining glue-bond quality. The objective of this research was to determine how well seven traditional two-dimensional measures of surface roughness as well as lathe check information related to glue-bond performance (load at failure and percent wood failure) of plywood made from rotary peeled, 1/8-inch-thick Douglas-fir (Pseudotsuga menziesii) veneer. There was strong evidence that an increase in surface roughness was associated with a decrease in load at failure and percent wood failure. However, the only statistically significant relationship found between any of the seven roughness measures or combination of measures and load at failure or percent wood failure was a correlation of 0.82 when all loose-side roughness measures were regressed against percent wood failure. The inclusion of lathe check depth and frequency with the roughness measures improved the correlation with percent wood failure to 0.91. Except for the skewness and kurtosis measures, there was no statistically significant difference in the means of the roughness measures between the tight and loose sides of the veneer. Analysis of the nature of failure indicated that the samples primarily failed on the loose side of the veneer, and this trend was noted across all roughness categories.

Image segmentation is a key stage in the detection of defects in images of wood surfaces. While there are many segmentation algorithms, they can be broadly divided into two categories based on whether they use discontinuities or similarities in the image data. Each algorithm can also be categorized based on other factors such as whether it uses color or gray-scale data and is a local or global operator. While this presents a wide variety of approaches for segmenting images of features on wood surfaces, it also makes it difficult to select the most appropriate techniques. This paper presents the results obtained from using a variety of algorithms for wood surface feature detection and defines several measures used for examining algorithm performance. A region-based, similarity algorithm that was a combination of clustering and region-growing techniques exhibited the best overall performance. This was particularly true for defects that are subtle, meaning they blend in with other natural features on wood surfaces that are not considered defects. Examples include blue stain, pitch streaks, and wane. The clustering with region growing algorithm improved the detection accuracy of pitch streaks by over 20 percentage points compared to the next best algorithm. However, if subtle defects are not of interest, the edge detection algorithms performed as well as the region growing algorithm but with slightly better clearwood detection accuracies. The influence of color information, local-basis analysis, and camera resolution on algorithm performance varied by segmentation technique and defect category. Because each wood processing application has its own unique set of defect detection requirements, conclusions regarding which algorithms and factors are best must be made in the context of those processing requirements.

(Mirb.) Franco) veneer can be accurately classified via visible-region spectral-reflectance curves and quadratic discriminant analysis. This paper extends those results to an expanded set of features, a broader spectrum that includes near-infrared as well as visible wavelengths and a larger set of physical samples. It also tests two methods for eliminating the classification procedure's reliance on raw spectral-reflectance curves. Instead of working with the raw curves, which are difficult to obtain by traditional means at sufficient speeds in a production environment, the data required by these two methods is much reduced and can potentially be obtained from a video camera equipped with either custom or commercially available bandpass filters. The paper shows that classification accuracies achieved with either of the two reduced-data methods are comparable to the accuracies achieved when using raw spectral data.

This article presents a framework for generating knowledge using computer simulation for problems that are constrained by expert availability and knowledge acquisition. The methodology is developed in the context of sawmill industry. A range of sawmill manufacturing configurations are modeled and analyzed under different operating conditions. The simulation results are used to develop relationships among operating variables and system constraints. Simulation experiments are then used to identify and evaluate solution strategies for handling the constraints. The result is a simulation model with an embedded knowledge base for decision support in sawmill management.

Previous research on the dielectric properties of wood concentrated on clear wood or specific chemical components of wood. Practice, however, requires data not only on the dielectric properties of normal wood but also for typical defects associated with wood. Research was conducted to determine the magnitudes of the complex dielectric constant and loss tangent for typical wood features. In addition, their sensitivities to a range of excitation frequencies and wood moisture levels were examined. This paper presents examples that illustrate the type of data obtained for various wood features. This information will eventually help determine optimal operational parameters for dielectric-based scanning devices for wood products.

Simulation was used to investigate the effects of a salvage operation on finger-joint cut-stock production from three grades of red alder (Alnus rubra) lumber edged by two alternative practices. The edging practices considered are an actual mill practice versus a much lighter edging practice that creates 2 feet of uninterrupted wane-free edge on both sides of each board. The sawing processes considered were a 2-stage, rip-crosscut process and a 3-stage, rip/crosscut/re-rip process, both of which produce random-length, fixed-width pieces. The paper presents the effects of these operational parameters on the number and sizes of the cut-stock parts. A differential income analysis was also conducted to examine their effects on cut-stock and by-product income, as well as on handling, drying, and transportation costs. The results show that both the edging and sawing methods substantially affect cut-stock volume and piece-size distribution in ways that are similar for each lumber grade. Either switching from mill edging to 2-foot-clean edging or adding a third-stage, re-rip salvage operation increased recovery by about 12 to 13 percent. Combining both changes increased recovery by about 30 percent and increased differential revenue by an average of more than $300 per thousand board feet over mill edging and 2-stage sawing. While the actual benefits realized will be specific to each mill, these dollar amounts appear to be large enough to make investigating these alternatives worthwhile for roughmill operators.

The paper presents a simulation modeling environment developed for sawmill design and analysis in the forest products industry. The design facilitates flexibility in modeling different sawmill configurations and production scenarios. The system represents a library of objects developed in an object-oriented framework. These include structures required to develop simulation models, to execute discrete event simulation, and for system-user interface.

Analysis of computer images of wood can usually be enhanced by the early elimination of uninteresting areas in the images. SISM and NSISM are algorithms that identify clear regions in images of wood so that such regions can be largely ignored in subsequent processing. Both perform well on most images, but falter on some. This paper describes how NSISM was refined to make it perform better on troublesome image areas without compromising its performance on more typical areas. Making such refinements to any scanning algorithm is a difficult undertaking that is usually characterized by modest performance gains. However, the economic viability of a scanning system may depend critically upon whether such gains can be achieved. A comparison of the refined algorithm, called ASISM, to the original two shows that ASISM performs better than or equal to its predecessors across a range of commonly occurring wood features in Douglas-fir veneer.

The dichromatic reflection paradigm describes light reflection from optically inhomogeneous materials as the sum of body (diffuse) and interface (specular) reflections. Interface reflection represents unaltered light reflected from a material's surface. Body reflection represents light altered by the material's pigments and thus may provide information about the identity of the material. Wood is an optically inhomogeneous material that is also anisotropic. This latter property adds further complexity to the analysis of wood-surface images by creating localized magnitude differences in interface reflection as surface texture and fiber orientation change. This paper presents the results of a study that tested whether the use of only the body component of reflected light can significantly improve the classification of wood-surface features. To this end, reflectance curves of various Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) veneer features were separated into body and interface components, and their dimensionality reduced to a small number of basis function. Two discriminant functions, one constructed from body reflectances and the other from total reflectances, were then developed from the reduced reflectance data. The performance of the two discriminant functions were compared by classifying a new set of wood-feature spectral reflectances with each discriminant function.

Many wood products manufacturing processes require a 3-dimensional measure of surface roughness to determine processing parameters and product grades and values. Currently, on- line measurement of wood surface roughness is limited to visual inspection and single-point laser-based triangulation or ultrasonic systems, while most off-line analysis is based on stylus tracing. Wood has unique characteristics that complicate surface texture measurement and analysis such as the need to separate distinct causes of error of form, waviness, and roughness as well as to correlate visual grades of processing standards with 1-dimensional (1-D), 2-D, and 3-D measures. This paper discusses the performance characteristics of a laser scatter/optical imaging system for wood roughness measurement and compares them to those of a stylus tracing system. The abilities of both approaches to capture the types of roughness information required in wood manufacturing processes are discussed as well as the functionality of 1-D, 2-D, and 3-D roughness descriptors.

This paper describes a flexible, general-purpose simulation environment for sawmill modeling and analysis. The system represents a library of objects developed in an object-oriented framework. The objective is to develop a system that can be used to mode different sawmill configurations, to identify manufacturing process constraints, and to evaluate control strategies and management practices.