Western hemlock is a species that is highly susceptible to compression wood (CW) formation, an abnormal wood tissue that forms on the under side of leaning tree stems and branches. When lumber cut from logs containing CW is dried, the CW shrinks approximately 10 times normal in the parallel to grain direction, resulting in degrade, at times severe, due to warp in the form of crook and bow. In this project a technique using an ultrasonic materials evaluation system (UME) was tested for its ability to detect CW. Since stress wave velocity, in addition to being dependent on elastic properties and material density, is also a function of growth ring orientation, a slope of grain indicator was evaluated for its ability to measure growth ring orientation, to be used in conjuction with the UME.
The objective of this project was to develop a new feed speed control system for band saws. This system regulates the feed speed based on the cutting depth measured ahead of the saw. In comparison to other feed speed control systems presently used in sawmill operations, the new system allows maximum feed speeds without overfeeding the saw and also avoids underfeeding. The equipment developed basically involves two laser light generators which place laser lines along the saw cut on the saw entry and saw exit side, two cameras which locate the position of the laser or saw lines, and a microprocessor which processes the information from the cameras, determines the feed speed based on the known relationship between sawing variables and gives the signal to the carriage drive. Considerable experimenting was required to accurately measure the distance between the laser lines on the saw log due to colour variations of the long surface and more so due to the irregular geometry of many saw logs. Also a high working speed of the system had to be achieved to correspond to the high feed speeds used in sawmill operations. The new feed speed control system was tested with Forintek's 5-ft band mill. It was found that the actual feed speed set by the feed speed control, and the calculated feed speed were in close agreement showing that the system is able to effectively control the feed speed based on the cutting depth. Additional work is needed and will be carried out to further refine the system before commercialization can be undertaken.
The new technologies, incising, moisture tolerant phenolic adhesives and steam pressing were evaluated for the manufacture of laminated veneer lumber (LVL). Both 8- and 13-ply incised spruce LVL panels were prepared using these new technologies. The results showed that both steam pressing and self-generated steam from wet face and back veneers accelerated temperature rise in the innermost glueline of 13-ply incised spruce LVL panels. This would help facilitate faster production rates for LVL manufacture. Bond quality and edge bending values were determined for the steam-pressed 8-ply and 13-ply incised spruce LVL panels. In all cases the average % wood failure was above 90% indicating excellent adhesion between the moisture tolerant adhesive and wood. The modulus of rupture and modulus of elasticity values measured for the steam-pressed incised spruce LVL samples compared very favourably with those for a commercial Norway spruce 15-ply LVL product.
Thin circular saws can suffer from a vibration phenomena called critical speed instability. At the critical speed, a resonant condition occurs where a saw can snake slowly from side-to-side producing unacceptably large sawing variation. To avoid this problem, most circular saws operate at 10 to 15 percent below the first critical speed. Unfortunately, this practice limits reductions in saw plate thickness and corresponding improvements in lumber recovery. Recently, several mills have been able to operate guided splined-arbor saws above critical speed. These supercritical speed saws offer significant sawing performance improvements by allowing both high recovery and high production rates. The use of these saws remains rare, however, and very little knowledge is available to guide mills that want to investigate this promising area. This report describes laboratory tests involving two supercritical speed saw configurations which are operating successfully in industry. Detailed descriptions of these configurations are given and guidelines for use are described. Idling and cutting tests were completed to characterize vibrational behaviour and demonstrate sawing performance levels. Tests were done to investigate the effect of changes in saw tensioning, saw tooth design parameters, saw and feed speeds and saw plate thicknesses. Test results confirm that for the sawing configurations tested, operating speeds can be found in the supercritical speed region where stable idling behaviour allows successful sawing. As with conventional saws, sawing accuracy is best at lower feed speeds. However, by operating at supercritical speeds, acceptable sawing accuracy can be achieved at higher feed speeds than are possible using conventional saws. Saw tensioning allows further increases in saw and feed speeds, but is not essential for supercritical speed operation. Changes in saw thickness strongly affect sawing performance levels and lumber recovery. Thinner saws have higher sawing variation and must operate at lower feed speeds than thicker saws. Curves showing the relationship between saw plate thickness, feed speeds and sawing accuracy are presented which can be used to assess the economic benefits of the supercritical speed saws that were tested. Supercritical speed circular saws offer considerable potential to improve sawing performance and increase lumber recovery. These saws allow reductions in saw kerf widths while maintaining high feed speeds and acceptable sawing accuracy.
Six impregnating phenol formaldehyde (PF) resins having low to moderate molecular weight were synthesized and evaluated for their wood veneer penetration and curing properties. Based on the results from the penetration and curing properties studies, a PF resin designated as B-2 was used to impregnate subalpine fir, white spruce and lodgepole pine veneer. LVL panels, 12 x 12 inch, were prepared with these veneers. Both modulus of rupture (MOR) and modulus of elasticity (MOE) were increased by 10 to 15% for the resin-impregnated LVL made from each of the SPF species. Edgewise bending results for specimens cut from 2 x 4 foot white spruce LVL panels showed an increase of 15% both for MOR and MOE for the resin impregnated specimens. As well, the dimensional properties (% edge swelling and % water uptake) of the SPF LVL panels were improved by 50% using the patented Forintek resin impregnation method.
Canadian wood products present a problem when it comes to improving their properties through chemical treatment. Most Canadian wood species have heartwood that, after kiln drying is relatively impermeable to pressure treatment with aqueous solutions. One means to rectify this problem may be the use of different drying regimes. This project was designed to evaluate the effect of seven different drying regimes on the permeability of the heartwoods of five BC wood species. This report covers Phase I, research on lodgepole pine and white spruce. Lumber from these species was pre-sorted for permeability and moisture content and matched groups of 60 boards were subjected to one of seven drying regimes. These were, air drying, dehumidification, conventional kiln drying, steam plus conventional, high temperature, radio frequency/vacuum and superheated steam /vacuum drying. Each group was then separated into two sub-groups of 30 boards. One sub-group was pressure treated with disodium octaborate tetrahydrate (DOT) and the other was pressure treated with chromated copper arsenate (CCA). Each board was weighed before and after treatment to determine solution uptake. The DOT-treated material was sampled for solution penetration and chemical analysis immediately after treatment. The CCA-treated material was sampled after preservative fixation. The data from Phase I have not yet been statistically analysed. This will be done early in year two.
This paper investigates the feasibility of increasing bandmill production by proportionally increasing both blade speed and lumber feed speed. A modal analysis of the bandmill and bandsaw was conducted and resonant conditions, likely to impair performance, were identified. Cutting tests were conducted to determine the effect of increased blade speed on cutting accuracy, surface finish and sawdust quality. The tests were conducted at blade speeds of 10,000 fpm, 12,500 fpm and 15,000 fpm and examined the effect of tipped and swaged blades cutting Coastal Hem/Fir and Interior SPF.
The global objective of the project is to investigate the feasibility of increasing bandmill production by proportionately increasing both the blade speed and the lumber feed speed. The objective of this phase of the project is to transfer the results of the laboratory experiments to the sawmill industry. The work described in this report covers the transfer of the technology to two sawmills. The first report has a more detailed introduction to the project and a review of the literature.
