Eastern SPF producters experience an average value loss of $10 to $16/mbf due to drying degrade. A clear understanding of how wood characteristics influence warp will make it easier to effectively modify drying processes to reduce these losses. The goal of this study was to categorize green lumber according to its potential to warp, dry the lumber using a typical industrial kiln schedule and assess whether pieces that either warped or remained straight were correctly identified. Experimental material was a sample of 440 black spruce 8-foot 2x4's from four grain defect groups. These were : 1) control, no grain defects; 2) cross grain but no compression wood; 3) compression wood but no cross grain; and 4) both cross grain and compression wood. Methods used to select lumber with either a high or low potential to warp were successful. Warp was found to be related to the severity of compression wood and cross grain in each piece. Lumber without cross grain or compression wood dried with very little warp. Lumber with both cross grain and compression wood had the lowest quality after drying.
Standard tooth designs for ripsaws carry a cutting edge which is square in relation to the saw blade axis. This saw tooth design proved to be satisfactory in the past when saws were heavy in kerf and sawdust was not considered as an important fibre source for pulp or other fibre based products. Forintek recognized that this tooth design is not optimum for achieving the best sawing performance and producing high quality sawdust for pulp. This report describes the results of extensive sawing experiments carried out in both the laboratory and in the sawmill to develop a new tooth design.
Mould and stain became troublesome problems on lumber manufactured at a coastal British Columbia sawmill, and the difficulties were suspected to be a fault of the mill's antisapstain treatment. Forintek technical staff visited the sawmill and planer mill and used two procedures to gather assessment. Firstly, boards were pulled from spray box chains after spray treatment and one-inch square samples were punched from four faces of these boards for chemical analysis of DDAC, one of the active ingredients in the formulation being used. With a large number of samples, this procedure quantitatively assessed DDAC retention levels at points along boards. Secondly, fluorescent dye was added to the spray solutions and special paper strips were stapled along the length of boards prior to treatment in the spray box. The paper strips were then retrieved for examination under ultraviolet light. This procedure is largely a qualitative one, showing the pattern of spray coverage over the whole board. Liquid samples of the treatment solutions were taken from both the sawmill and planer cross chain day tanks to determine their DDAC concentrations.
Softwood sawmill designers, engineers and managers may benefit from computer simulation analysis of proposed and existing sawmill systems. Simulation models exist that allow users to construct and execute discrete event simulations, but these have incorporated compromises or limitations that reduce the accuracy of the results, or preclude special considerations and observations. The proposed microcomputer discrete event simulation model will allow for real log shapes, explicit lumber orders, learning curves and catastophe scheduling with emergency actions and transient response analysis.
Le projet visait la modelisation du positionnement des billes de bois au premier debitage. L'objectif etant de developper de nouvelles methodes de simulation du comportement des appareils et des strategies usuelles de positionnement des billes au premier debitage. Dans un premier temps, une analyse du processus de sciage et des appareils a ete effectuee en rechechant les caracteristiques essentielles a modeliser. Par la suite un ensemble d'algorithmes de nature geometrique a ete developpe de maniere a modeliser les positionneurs existants. Deux methodes de construction des algorithmes ont ete etudiees : la calcul des angles formant une suite de transformations applicables a la representation geometrique initiale des billes et la recherche d'un nouveau referentiel. Cette derniere methode fut examinee en profondeur; son implantation et les resultats generes ont permis de visualiser les effets des differents positionneurs. Les algorithmes resultant du present projet ont d'ailleurs ete integres au prototype du modele de simulation du sciage presentement en developpement au groupe Forintek-Laval.
Ce projet constitue le programme d'etude de maitrise d'une etudiante (Annick Tremblay) du departement d'informatique de l'Universite Laval. Les objectifs etaient de developper un algorigthme d'optimisation des operations de delignage et d'eboutage ainsi que de proposer un algorithme effectuant le positionnement optimal des pieces a debiter. L'algorithme choisi pour le delignage et l'eboutage est fonde sur une technique d'optimisation appellee programmation dynamique. Pour sa part, l'algorithme de positionnement fait appel a une technique de subdivision d'intervalles. L'algorithme de positionnement ameliore de 76% le temps de traitement par rapport a l'algorithme de recherche exhaustive (force brute) generalement utilise.
Les travaux prevus pour l'annee fiscale 1993-1994 sont les suivants : 1) Inclure la possibilite de considerer des conditions de sechage variables dans le modele; 2) Inclure la modelisation du transfert de chaleur dans le bois et son couplage avec le transfert de masse; 3) Effectuer une etude de sensibilite afin d'identifier les parametres auxquels le modele est le plus sensible; 4) Determiner la relation teneur en himidite - potentiel hydrique et la conductivite hydrique effective pour l'epinette; 5) Effectuer une etude theorique des phenomenes de transfert convectifs a l'interface bois-air.
There are six species of poplar native to Canada's forests. One of the most abundant and widely used of the species is the aspen poplar (populus Tremuloides). Aspen has become the most desirable species for the production of oriented strandboard (OSB). Certain sections of Alberta and British Columbia have considerable stands of aspen. The aspen stands also contain varying amounts of balsam poplar (populus balsamifera) and black cottonwood (populus trichocarpa) and various hybrids of the three species. Forintek Canada Corp's Technical Advisory Committee (TAC) was asked by the B.C.Ministry of Forests to establish whether cottonwood could be a suitable furnish for the production of OSB, since it represented a sizeable potential resource in British Columbia. The poplar species are loosely identified by several names and to confirm the actual species we were referred to Mr.Bob Brash, District Manager, Dawson Creek Forest District. Mr.Brash confirmed that the species in question was in fact balsam poplar (populus balsamifera). Balsam poplar is also known as black poplar and balm poplar. An extensive literature search was conducted on the use of balsam poplar/cottonwood in the production of OSB. The literature review and a summary are reported here.
This paper describes and evaluates new and existing models for exterior log geometry. Compatibility with 1,2,3, and 4-axis shadow scanners determined which models were selected for evaluation. Models were considered for potential use in sawmilling process simulation and optimization. The accuracy evaluation compared models based upon lost and added fiber percentages. All models tended to overestimate log cross section area. Popular circular and elliptical models provided the poorest accuracy. Elliptical models used with 2-axis or 3-axis scanners generated up to 8% lost fiber and up to 15% added fiber. The 3-axis dyadic and Chaikin models provided the best overall performance : lost fiber under 3.5% and added fiber under 13%. Results from the evaluation recommend a 3-axis scanner system for automatic positioning and breakdown optimization. The small benefit obtained from 4-axis models does not justify their use. Other technologies are recommended where better accuracy is needed.
Ce rapport renferme essentiellement les specifications fonctionnelles de la version 1.0 du prototype d'un modele de simulation de la transformation des bois en bois de sciage. Une description des structures de donnees, des fonctions et des classes est fournie pour chaque module du prototype. Un listage de l'implantation accompagne egalement chaque module. A la section 2.0, le lecteur peut au depart se familiariser avec les objectifs et l'approche adoptes pour le developpement de ce prototype. A cette fin, un acte de conference et un article scientifique ont ete inseres dans le rapport.
Nous presentons ici une revue des travaux parus jusqu'a maintenant au sujet du comportement mecanique et de la modelisation des contraintes de sechage dans le bois. Notre presentation est articulee en fonction des principaux domaines - transferts de chaleur et de masse, modeles de contraintes de sechage, proprietes mecaniques du bois lors du sechage et modelisation numerique, l'accent etant mis sur les trois derniers domaines. Afin d'identifier les approches presentant le plus de potentiel pour la description mecanique et la modelisation de contraintes du sechage, notre revue est basee sur une compilation bibliographique d'environ 90 titres.
