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Characterizing aspen veneer for LVL/plywood products. Part 1. Stress grades of veneer|Characterizing aspen veneer for LVL/plywood products

https://library.fpinnovations.ca/en/permalink/fpipub1157
Author
Wang, Brad J.
Date
July 2001
Edition
37589
Material Type
Research report
Field
Wood Manufacturing & Digitalization
Author
Wang, Brad J.
Date
July 2001
Edition
37589
Material Type
Research report
Physical Description
14 p.
Sector
Wood Products
Field
Wood Manufacturing & Digitalization
Research Area
Advanced Wood Manufacturing
Subject
Veneer manufacturing
Veneer
Populus
Plywood manufacture
Plywood
Laminate product
Aspen
Series Number
W-1791
Location
Vancouver, British Columbia
Language
English
Abstract
In this work, the properties of aspen veneer from two mills (A and B) were compared. The comparisons between the incised veneer and non-incised veneer for mill A were made in terms of veneer thickness, ultrasonic propagation time (UPT), density and MOE. The aspen veneer was further characterized for LVL/plywood products by tailoring veneer grades to the requirements of final veneer products. In addition, MOE-based veneer stress grading and UPT-based veneer stress grading were compared for the aspen veneer. The advantages of MOE-based veneer stress grading over UPT-based veneer stress grading were identified in terms of veneer grade MOE and volume breakdown. The main results are summarized as follows: 1) Aspen veneer properties change from mill to mill. The differences in aspen veneer density and MOE between mill A and B are significant with mill A producing denser and stronger aspen veneer. 2) For aspen veneer in the mill A, the distribution shapes of veneer thickness, UPT, density and MOE between the non-incised and incised veneer are quite similar. Although the differences in veneer thickness, UPT and density between the non-incised veneer and incised veneer are identified as significant, the difference in veneer MOE is not significant due to the effect of both veneer UPT and density. The incised veneer has a slightly higher variation in thickness and is also slightly thicker compared to the non-incised veneer. This could due to the change of lathe settings or the property variation of aspen species as indicated with the veneer density variation. 3) Of the aspen veneer from mill A, using the optimum UPT thresholds, about 27.5 ~ 30.9% can be extracted through veneer stress grading to make 2.0 million psi LVL; about 43.4 ~ 59.9% can be sorted out for 1.8 million psi LVL; and the remaining 12.6 ~ 25.7% can be used for 1.5 million psi LVL or for plywood. It was also found that the incised aspen veneer generates 3.4% less of top stress grade G1 but 16.5% more of stress grade G2 compared to the non-incised aspen veneer if performing the optimum UPT-based stress grading. 4) The MOE-based veneer stress grading not only results in a smaller variation in MOE of each grade, but also higher volume percentages of stress grades G1 and G2 compared to the UPT-based veneer stress grading. This smaller variation in MOE of each stress grade will be very beneficial to the industry and structural applications since higher design stress can be assigned for the wood structural components. Also the higher percentages of stress grades G1 and G2 with the MOE-based veneer stress grading has significant economical implications and should be recognized by the industry. 5) To maximize mill profits, veneer sheets need to be periodically sampled and analyzed using the VGrader software. The optimum grading thresholds for the specific veneer can be established for on-line veneer stress grading based on the current market and requirements of final veneer products, providing a real solution to characterize and make best use of the specific veneer for LVL/plywood products.
Veneers - Manufacture - Tests
Populus - Veneers
Plywood - Manufacture
Lumber, Laminated veneer - Manufacture
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Characterizing aspen veneer for LVL/plywood products. Part 2. LVL pressing strategies and strength properties|Manufacturing characteristics and strength properties of aspen LVL using stress graded veneer

https://library.fpinnovations.ca/en/permalink/fpipub1158
Author
Wang, Brad J.
Date
August 2001
Edition
37590
Material Type
Research report
Field
Wood Manufacturing & Digitalization
Author
Wang, Brad J.
Date
August 2001
Edition
37590
Material Type
Research report
Physical Description
41 p.
Sector
Wood Products
Field
Wood Manufacturing & Digitalization
Research Area
Advanced Wood Manufacturing
Subject
Veneer manufacturing
Veneer
Mechanical properties
Populus
Laminate product
Aspen
Series Number
W-1792
Location
Vancouver, British Columbia
Language
English
Abstract
In this study, aspen veneer sheets were sampled from a Forintek member mill. Their attributes and properties were measured. Using the optimum stress grading strategy, aspen veneer was segregated into 3 distinct stiffness groups (stress grades G1, G2 and G3) and conditioned to 3 different moisture levels. An experimental design for 3-level four factors comprising veneer moisture content, veneer stress grade, mat pressure and glue spread (or resin level) was adopted. Based on the experimental design, LVL panels with different combinations of four factors were pressed until the target core temperature reached 1050C to achieve full cure followed by a stepwise decompression cycle. The LVL panel final thickness, density, compression ratio and relevant strength properties were measured. After that the effect of aspen veneer moisture, stress grade, mat pressure and glue spread and their relative importance on LVL compression behavior, hot-pressing and strength properties were evaluated using a statistical analysis program. The relationship between LVL panel properties and veneer properties was examined. Finally a method to enhance LVL modulus of elasticity (MOE) to make high stiffness LVL was discussed. From this study, the following results were found: Aspen veneer is capable of making LVL products meeting 1.8 and 2.0 million psi MOE requirements. Optimum veneer stress grading and proper pressing schedule are two important keys to the manufacture of high-stiffness aspen LVL products. Further, a possibility to make high-grade aspen LVL meeting 2.2 million psi MOE exists by proper veneer densification and optimum veneer stress grading. The roles of four factors affecting LVL pressing behavior and strength properties are quite different. Glue spread and mat pressure, rather than stress grade and veneer moisture content, are two main factors affecting hot-pressing time taken for the core to reach 1050C. With incised veneer, the moisture from the glue in the glueline affects the rise of core temperature more pronouncedly than the moisture in the veneer, and is more critical to the cure of the glue. High glue spread (44 lbs/1000ft2) not only significantly increases the hot pressing time taken for the core to rise to 1050C, but overall also decreases most LVL strength properties with the pressing schedule used. High mat pressure does not necessarily result in high LVL panel compression due to the high gas pressure that occurs in the core. Veneer stress grade and veneer moisture are the two predominant factors that mostly affect LVL strength properties. LVL panels assembled with high stress grade result in increases in both flatwise and edgewise MOE and MOR properties rather than shear strength either longitudinal or through-the-thickness. Further, using high stress grade veneer can help make more efficient structural systems in terms of both stiffness-to-weight and bending strength-to-weight ratios compared to using low stress grade veneer. High veneer moisture at 6% impairs all LVL strength properties except edgewise bending MOE. LVL compression ratio can help link veneer MOE with LVL panel edgewise bending MOE. Overall, every increase of 1% in LVL compression ratio would result in 1% increase in LVL and veneer MOE ratio. With regard to aspen LVL MOE enhancement, using high veneer stress grade gains slightly less than using low veneer stress grade. On average, every increase of 1% in aspen LVL compression ratio results in 0.82%, 1.05% and 1.20% increase in aspen LVL and veneer MOE ratio assembled with stress grades G1, G2 and G3, respectively. In practice, those conversion factors for any specific veneer can be derived based on the correlation between veneer MOE and MOE of target LVL/plywood products made with proper pressing schedules, and be further used to derive requested veneer MOE for each stress grade to perform the optimum veneer stress grading. Pressing schedules show significant effect on aspen LVL compression behavior and strength properties. Using a pressing schedule with step-wise decompression cycles following the core temperature to rise to 1050C, an excessive compression of LVL in the range of 13.5% to 27.6% is generated which results in high-stiffness LVL with an average MOE of approximate 2.0 million psi for all experiments. Although this pressing schedule has slightly longer pressing time and off-target LVL thickness than current commercial LVL pressing schedules, it helps enhance the strength properties of LVL. It is recommended that further work should include the effect of different decompression cycles and mat pressure on LVL panel compression ratio and strength properties.
Populus - Veneers - Strength
Veneers - Manufacture - Tests
Lumber, Laminated veneer - Manufacture
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Development of pressing strategies for veneer panel products

https://library.fpinnovations.ca/en/permalink/fpipub37386
Author
Andersen, Axel W.
Troughton, G.E.
Date
March 1995
Material Type
Research report
Field
Wood Manufacturing & Digitalization
Author
Andersen, Axel W.
Troughton, G.E.
Contributor
Canada. Canadian Forest Service.
Date
March 1995
Material Type
Research report
Physical Description
19 p.
Sector
Wood Products
Field
Wood Manufacturing & Digitalization
Research Area
Advanced Wood Manufacturing
Subject
Veneer manufacturing
Veneer
Pressing
Plywood manufacture
Plywood
Panels
Laminate product
Series Number
Canadian Forest Service No. 21
Contract no. 1812L010
W-1223
Location
Vancouver, British Columbia
Language
English
Abstract
A series of plywood and laminated veneer lumber (LVL) panels were prepared using incised veneers in the second phase of this two year project. The primary purpose of the work was to evaluate the effects of steam injection on the pressing times. A secondary objective was to expand the study of warpage in three-ply and four-ply plywood which was begun in phase one. Thirteen-ply 40 mm (1 5/8 inch) thick panels were evaluated for press times and thin 9.5 mm (3/8 inch) and 12.5 mm (1/2 inch) panels were evaluated for cupping and bowing. Press temperatures of 150 degrees C, 175 degrees C and 204 degrees C were used with a commercial adhesive mix for the LVL study while normal plywood pressing conditions were used for the plywood. For the plywood warpage study, the effect of lathe check orientation and species mix were evaluated. The lathe check orientation had little effect while the surface veneer species had a pronounced effect on the warpage in the plywood. Steam used for injection was heated to 260 degrees C at 450 KPa (65 psi) with a super-heater. All panels were made with incised 3.2 mm (1/8 inch) SPF veneers. The project demonstrated that steam injection can shorten press times by fifty percent if incised veneers are used.
Lumber, Laminated veneer - Pressing
Lumber, Laminated veneer - Manufacture
Veneers - Pressing
Veneers - Manufacture
Plywood - Panels - Pressing
Plywood - Manufacture
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Development of pressing strategies for veneer panel products

https://library.fpinnovations.ca/en/permalink/fpipub37334
Author
Andersen, Axel W.
Date
March 1994
Material Type
Research report
Field
Wood Manufacturing & Digitalization
Author
Andersen, Axel W.
Contributor
Canada. Canadian Forest Service.
Date
March 1994
Material Type
Research report
Physical Description
8 p.
Sector
Wood Products
Field
Wood Manufacturing & Digitalization
Research Area
Advanced Wood Manufacturing
Subject
Veneer manufacturing
Veneer
Pressing
Plywood manufacture
Plywood
Panels
Laminate product
Series Number
Canadian Forest Service No. 23
Contract no. 1812L010
W-1093
Location
Vancouver, British Columbia
Language
English
Abstract
A series of plywood and laminated veneer lumber (LVL) panels were prepared using veneers with higher than normal moisture contents in face and back layers. The purpose of the work was to evaluate the effects of self-generated steam on the pressing times and panel warpage. Panels made with 6% and 10% m.c. faces and backs were compared with control panels made with all dry veneer. Thirteen- ply 40 mm (1 5/8 inch) thick panels were evaluated for press times and thin 9.5 mm (3/8 inch) panels were evaluated for cupping and bowing. Normal plywood press temperatures and adhesives were used. All panels were made with incised 3.2 mm (1/8 inch) SPF veneers. The project demonstrated that substantially shorter press times and more dimensionally stable panels can potentially be made using higher moisture content outside veneers.
Lumber, Laminated veneer - Pressing
Lumber, Laminated veneer - Manufacture
Veneers - Pressing
Veneers - Manufacture
Plywood - Panels - Pressing
Plywood - Manufacture
Documents
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Improved veneer production : final report

https://library.fpinnovations.ca/en/permalink/fpipub5520
Author
Dai, Chunping
Salahuddin, U.
Date
April 1996
Edition
37406
Material Type
Research report
Field
Wood Manufacturing & Digitalization
Author
Dai, Chunping
Salahuddin, U.
Date
April 1996
Edition
37406
Material Type
Research report
Physical Description
26 p.
Sector
Wood Products
Field
Wood Manufacturing & Digitalization
Research Area
Advanced Wood Manufacturing
Subject
Veneer manufacturing
Veneer
Series Number
W-1302
Location
Vancouver, British Columbia
Language
English
Abstract
In order to help the plywood industry improve veneer production from new high-tech veneer lathes, this report evaluates present veneer block conditioning methods and techniques for possible areas of enhancement and identifies the need for new innovative instrumentation technology.
Veneers - Manufacture
Documents
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Innovative veneer processing technologies

https://library.fpinnovations.ca/en/permalink/fpipub37668
Author
Dai, Chunping
Wang, Brad J.
Date
September 2003
Material Type
Research report
Field
Wood Manufacturing & Digitalization
Author
Dai, Chunping
Wang, Brad J.
Date
September 2003
Material Type
Research report
Physical Description
34 p.
Sector
Wood Products
Field
Wood Manufacturing & Digitalization
Research Area
Advanced Wood Manufacturing
Subject
Veneer manufacturing
Veneer cutting
Veneer
Scanning electron microscopy
Scanners
Recovery
Quality control
Qualitative analysis
Peeling
Series Number
3250
W-1987
Location
Vancouver, British Columbia
Language
English
Abstract
This report addresses issues about productivity, recovery and quality concerning veneer peeling in plywood mills. It was demonstrated that green veneer can be composed using a stitching technique. The maximum stitching speed was 50 ft/min which was slower than a current veneer composer. Stitched veneer did not have a significant effect on bending properties, but shear strength was slightly reduced which could be caused by the existence of stitching threads between the glueline. The roller bar diameter size had a significant influence on veneer quality. In general, peeling veneer with a 1” diameter roller bar resulted in the smoothest veneer with the most uniform thickness. The veneer thickness and roughness between 1.0” and 2.56” diameter roller bars were significantly different, but the difference in veneer quality between 1.75” and 2.56” diameter roller bars was not significant. Further, the difference in veneer quality between 1.0” and 1.75” diameter roller bars was not significant except for veneer roughness. Knife height also had a significant effect on veneer quality. Setting the knife at the spindle center proved to be the best. Veneer thickness at this setting was consistently closest to the target, and had the smoothest surfaces and smallest lathe checks. Average veneer thickness was lowest as well. While higher or lower settings created rougher veneer, higher settings were more forgiving than lower ones. For best results, the peeling knife should therefore be set at 0.0” to 0.015” above the spindle center. Incisor teeth pattern affected veneer quality. Narrower teeth and a wider gap resulted in better veneer quality in terms of veneer curl-up (flatness) and green and dry veneer thickness variations. However, the effect of incisor teeth patterns on veneer roughness and lathe checks seemed to be negligible. The validation tests revealed that an optimum lathe setting for the smooth roller bar was the following: pitch angle (PA) =89.50, vertical gap (VG)=0.425” and horizontal gap (HG) = 0.1”, and the optimum lathe setting for the incisor bar was the following: PA=90.50, VG=0.388” and HG=0.1” to 0.11” when peeling 1/8-inch veneer. The peeling computer program VPeel® was successfully upgraded to allow users to define profiles of pitch angle and horizontal gap. This feature will help the veneer product industry to define optimum lathe settings.
Recovery - Veneers
Veneers - Peel quality
Veneers - Manufacture
Scanners, Electronic
Veneers - Cutting, Rotary
Documents
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Investigation on air permeability of aspen veneer and glueline

https://library.fpinnovations.ca/en/permalink/fpipub5581
Author
Wang, Brad J.
Zhou, X.
Dai, Chunping
Date
April 2004
Edition
37695
Material Type
Research report
Field
Wood Manufacturing & Digitalization
Author
Wang, Brad J.
Zhou, X.
Dai, Chunping
Date
April 2004
Edition
37695
Material Type
Research report
Physical Description
27 p.
Sector
Wood Products
Field
Wood Manufacturing & Digitalization
Research Area
Advanced Wood Manufacturing
Subject
Veneer manufacturing
Veneer gluing
Veneer
Populus
Gluing
Aspen
Series Number
3901
W-2051
Location
Vancouver, British Columbia
Language
English
Abstract
In this study, we conducted systematic experiments on air permeability of aspen veneer and glueline in terms of panel compression ratio (or applied platen pressure), degree of glue cure (or pressing time), veneer type (sapwood or heartwood veneer) and glue spread level. We also compared the air permeability data of aspen veneer and veneer-ply (2-ply veneer panel) to aspen solid wood and aspen oriented strandboard (OSB). Based on this study, the following conclusions were drawn: For laminated veneer lumber (LVL) and plywood panels, the compression ratio is the most important factor affecting the panel permeability, followed by veneer type (sapwood or heartwood veneer), glue spread and degree of glue cure (or pressing time). The air permeability of the glueline decreases in the course of glue curing; however, its order of magnitude remains the same as that of uncured glue. The reduction in panel permeability mainly results from small densification of each veneer ply instead of the sealing effect of the glueline. Therefore, during LVL/plywood hot-pressing, the glueline does not serve as a main barrier to the gas and moisture movement as commonly speculated. However, due to the substantial change in the magnitude of panel permeability merely within a 5% compression ratio, the convection effect on heat and mass transfer is considered to be very limited. The air permeability of sapwood veneer is about twice that of heartwood veneer without compression. However, with compression, the air permeability of heartwood veneer drops much faster than that of sapwood veneer. The permeability of a sapwood veneer panel is 5.5 ~ 7.0 times higher than that of a heartwood veneer panel merely with a compression ratio in the range of 2.5% ~ 5%. In practice, it implies that 1) panels made from sapwood veneer are more treatable with preservatives; and 2) by controlling panel permeability through veneer incising, proper panel lay-up and densification, mills could reduce blows/blisters during hot-pressing. The air permeability of aspen wood or veneer is not affected by wood density. The air permeability of aspen LVL/plywood panels is 1.5~ 2 times larger than that of aspen solid wood due to the existence of lathe checks, but is significantly lower than that of aspen OSB at the same density level of the panel. On average, commercial LVL/plywood panels have almost the same magnitude of air permeability as commercial OSB. However, due to the absence of voids and small horizontal density variation, LVL/plywood panels will be less permeable than OSB.
Populus - Veneers
Veneers - Manufacture - Tests
Veneers - Gluing
Documents
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Manuel de déroulage et de tranchage

https://library.fpinnovations.ca/en/permalink/fpipub38871
Author
Feihl, A.O.
Date
January 1986
Material Type
Manual
Field
Wood Manufacturing & Digitalization
Author
Feihl, A.O.
Date
January 1986
Material Type
Manual
Physical Description
288 p.
Sector
Wood Products
Field
Wood Manufacturing & Digitalization
Research Area
Advanced Wood Manufacturing
Subject
Veneer
Veneer manufacturing
Series Number
E-3138
Location
Ottawa, Ontario
Language
French
ISBN
ISBN-0-86488-507-2
Abstract
Destiné au personnel des usines, ce manuel se veut un guide pratique sur les techniques de déroulage et de tranchage des placages. D'abord préparé pour les usines de l'Est du Canada, il fait aussi référence aux méthodes employées dans l'Ouest canadien. Les sujets qui suivent sont développés dans le manuel: le bois, les billes (entreposage, sciage, écorçage et chauffage), caractéristiques des palacages, couteaux de dérouleuses, dérouleuses, barres de semi-déroulage, trancheuses, problèmes de déroulage et leurs solutions, rendement en placage, utilisation de déchets et contrôle de la qualité.
Veneer Peeling - Technology
Veneer Properties
Veneer industry - Eastern Canada
Forintek Canada Corp. - Publications
Documents
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Optimization of peeling of aspen veneer using a 5/8" rotary bar

https://library.fpinnovations.ca/en/permalink/fpipub5522
Author
Dai, Chunping
Wong, J.
Date
August 1996
Edition
37420
Material Type
Research report
Field
Wood Manufacturing & Digitalization
Author
Dai, Chunping
Wong, J.
Date
August 1996
Edition
37420
Material Type
Research report
Physical Description
10 p.
Sector
Wood Products
Field
Wood Manufacturing & Digitalization
Research Area
Advanced Wood Manufacturing
Subject
Veneer manufacturing
Veneer cutting
Veneer
Populus
Aspen
Series Number
W-1332
Location
Vancouver, British Columbia
Language
English
Abstract
As a result of its fast growth and abundant availability, aspen has become an increasingly important commercial wood species in the production of oriented strand board (OSB) and veneer-based composites such as laminated veneer lumber (LVL). The purpose of the study described in this report was to determine the effect of conditioning temperature on veneer quality using a 5/8" roller bar, and to determine the optimum bar gaps based on results from previous Forintek studies on aspen veneer peeling.
Veneers - Manufacture
Populus - Veneers
Veneers - Cutting, Rotary
Documents
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Optimization of steam injection pressing for veneer panel products

https://library.fpinnovations.ca/en/permalink/fpipub37445
Author
Andersen, Axel W.
Troughton, G.E.
Date
April 1997
Material Type
Research report
Field
Wood Manufacturing & Digitalization
Author
Andersen, Axel W.
Troughton, G.E.
Date
April 1997
Material Type
Research report
Physical Description
15 p.
Sector
Wood Products
Field
Wood Manufacturing & Digitalization
Research Area
Advanced Wood Manufacturing
Subject
Veneer manufacturing
Veneer
Pressing
Plywood manufacture
Plywood
Panels
Laminate product
Series Number
Project No. 1070
W-1404
Location
Vancouver, British Columbia
Language
English
Abstract
Experiments were conducted to evaluate steam-injection pressing of plywood and LVL using saturated and superheated steam conditions. Three steam-injection times of one, two and three minutes were used to prepare 7-ply plywood and steam-injection times of three, five, seven, and nine minutes were used to prepare LVL. The results showed optimum pressing times were achieved with the steam-injection times of one and two minutes for the 7-ply plywood and seven minutes was found to be an optimum steam-injection time for LVL. All the panels prepared under a variety of steam conditions exhibited excellent bond quality and the average % wood failure was greater than 80% in all cases. For the preparation of the 7-ply plywood and LVL, using the optimum steam-injection times for both superheated and saturated steam conditions, the pressing time was reduced by over 30% compared to conventional platen heating. An economic analysis of return on investment for thick plywood products and LVL shows the pay-back period for retrofitting an existing plywood or LVL press for steam injection is less than three months.
Lumber, Laminated veneer - Pressing
Lumber, Laminated veneer - Manufacture
Veneers - Pressing
Veneers - Manufacture
Plywood - Panels - Pressing
Plywood - Manufacture
Documents
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15 records – page 1 of 2.