Further to the successful mill trial at Federated Co-operatives Limited in August 1995, a need to optimize the veneer lathe incisor and determine the benefits was identified. While the feasibility study was carried out directly at the mill, a majority of this work was conducted at the Forintek laboratory. During the early stages of this project, much effort was given to upgrade the Forintek 14-inch mini-lathe so that it could run with an incisor bar. Then an incisor bar assembly was fabricated for bar pattern tests. Finally, a series of tests were conducted to determine the optimum operation condition for an incisor bar and the effects of incising on veneer quality and recovery. The results showed that veneer is much flatter when peeled with a combination of incising and overdriving during peel. Species has a very strong effect on veneer flatness, especially spruce. Bar overdrive seems to be as equally important as incising. For the mini-lathe with which the tests were carried out, a 100.5% overdrive seems to yield the flattest veneer. Peeling speed and log conditioning has much less effect on veneer flatness than species and overdrive. Faster peeling speed and lower conditioning temperature seem to favour veneer flatness. According to the laboratory tests, veneer recovery can be increased by 5% from veneer stretching and flattening and reduction of spinout. An initial comparison also reveals that veneer peeled using an incisor bar may have less thickness variation and surface roughness. As a recommendation, further tests should be carried out to determine the effects of incising on other processing and performance properties such as pressing and bonding. The incising technology should be implemented in plywood mills, particularly in the softwood plywood mills, which use a big bar lathe, because an incisor bar can be easily retrofitted.
The work presented in this report addresses the FRBC value-added research priority area and shows good potential for creating jobs in the forest products sector and leading to new technology for manufacturing a value-added product. Experiments were conducted to evaluate steam-injection pressing of 7-ply SPF plywood and 13-ply SPF laminated veneer lumber (LVL) on a laboratory scale at Forintek and a pilot plant scale at Alberta Research Council (ARC). The laboratory experiments provided a basis for the pressing schedules used in the pilot plant trials at ARC. The following parameters were necessary for the steam-injection pilot plant trials: Top and bottom screens (0.6 mm stainless steel 30-mesh screen), incised veneer and a phenolic glue (Borden 2020) resistant to washout. Using steam-injection technology in pilot plant trials, substantial reductions in pressing time were achieved both for 7-ply SPF plywood and 13-ply SPF LVL. Specifically, a steam-injection time of one minute using saturated steam at 80 psi reduced the pressing time of 7-ply SPF plywood by 27% compared to conventional platen pressing. A steam-injection time of eight minutes using saturated steam at 80 psi reduced the pressing time of 13-ply SPF LVL by 32% compared to conventional platen pressing. Both the control and steam-injected 7-ply SPF plywood and 13-ply SPF LVL panels exhibited excellent bond quality and the average percentage wood failure was much greater than 80% in all cases thereby meeting the average percentage wood failure requirement in the CSA 0151 plywood standard. There was no significant difference in shear strength between control and steam-injected shear specimens. There was no statistical difference in average modulus of elasticity or modulus of rupture under flatwise and edgewise bending for the steam-injected LVL compared to the control LVL made using conventional platen pressing. A previous economic analysis of return on investment for thick plywood products and LVL showed that a 30% reduction in pressing time for a medium-size manufacturing plant would generate an additional profit of $3,000,000 per year.
Experiments were conducted to evaluate pressing of plywood and LVL using self-generated steam. For the 13-ply SPF LVL experiments, the average moisture content (avg. m.c.) in the outermost incised veneers was varied from 10 to 14% and for the 15-ply aspen LVL experiments the avg. m.c. was varied from 8 to 12%. For the 7-ply SPF plywood experiments, the avg. m.c. in the outermost incised veneers was 10 and 15%. In these experiments the controls and core incised veneers were 2% avg. m.c. Using the highest avg. m.c. in the outermost incised veneers, the pressing time for 13-ply SPF LVL was reduced by 31.1% and for 15-ply aspen LVL, 30.8 % and for 7-ply SPF plywood, 38.7%, compared to conventional hot platen pressing. The results showed that small changes in the avg. m.c. of the outermost veneers had a large effect on pressing time. Therefore, careful control of veneer m.c. under mill conditions would be very important. All the panels prepared under a variety of self-generated steam conditions exhibited excellent bond quality and the average % wood failure was much greater than 80% in all cases, thereby meeting the average % wood failure requirement in the CSA 0151 plywood standard. An economic analysis of return on investment for thick plywood products and LVL using self-generated steam pressing showed that a manufacturing plant would make a profit of about $3,000,000 per year.
Two methods of adding borate compounds to plywood panels were investigated. One method was patterned after successful efforts to incorporate zinc borate into OSB panels, where the borate is added to the adhesive. Zinc borate, which has shown some success in OSB, was however not sufficiently soluble and was replaced with a sodium borate. Method two involved the more traditional approach in pressure-treating wood veneers with a borate solution. A commercial borate compound (Timbor®) was used. The treatment target in each case was 2 % boric acid equivalent (BAE), which is the normal level being applied to solid wood. Borate addition to the adhesive was not successful for plywood due to the high level of borate required relative to the adhesive quantity. Treating of wood veneers prior to bonding yielded better panel bond quality results but showed large variation in borate retention levels within and between veneers. Treatment at the 2 % BAE target level did not produce panels with adequate bond quality. Treatment to 1 % BAE showed more promise but there were insufficient panels at the lower BAE level to allow for any evaluation of termite resistance.