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The effects of wood temperature, cutting width, and knots on the surface quality of black spruce cants processed by a chipper-canter were evaluated. Four matched groups of logs were machined at temperatures of 20°C, 0°C, −10°C, and −20°C. Each log was transformed at two cutting widths (CW: 12.7 and 25.4 mm). Knot characteristics were measured on the cant surfaces after log processing. Surface quality of cants was assessed by roughness and waviness parameters and torn grain. The quality of surfaces was affected by the temperature of logs and cutting width. Poorer surface quality was obtained at larger cutting widths. This was caused by increased cutting forces when processing more material at larger cutting widths, compounded by the presence of knots. Waviness and roughness were higher for frozen logs than for unfrozen logs. Although the sub-zero temperatures caused higher cutting forces and vibrations, their effect was partly offset by the strengthening of the earlywood and the brittle behaviour of frozen wood. Correlations and regression analyses showed that the optimisation of the cutting conditions for decreasing waviness and roughness should also reduce the torn grain depth. Moreover, the position and area of knots could be considered to minimise waviness and roughness and the occurrence of torn grain. [ABSTRACT FROM AUTHOR]

The effects of cutting speed (CS) and feed-per-knife (FK) on the surface quality of black spruce (Picea mariana [Mill.] B.S.P.) cants processed by a chipper-canter were evaluated. Nine matched groups of logs were studied at 20, 25, and 30 m/s of CS, and 19, 25, and 32 mm of FK. Each log was processed at frozen and unfrozen conditions. Knots and grain angle measurements were taken on the cant surfaces after machining. The quality of cants was assessed utilizing waviness, roughness, and torn grain. The results showed that the surface quality was affected by CS and FK. Surface quality improved as FK decreased, likely due to decreasing cutting forces. The waviness tended to improve as CS increased, which could be partly due to the reduction of the non-cutting period between knives at higher CS. The waviness and depth of torn grain were similar for frozen and unfrozen logs. Surface quality varied within the cant, being generally poorer in the lower half. Knots and orientation of spiral grain (left-handed) contributed to diminishing the quality of surfaces. Finally, the results of correlations and regression analyses showed that optimizing the cutting conditions to decrease waviness should also reduce the depth of torn grain. [ABSTRACT FROM AUTHOR]

The effect of the tip path overlap on debarking quality of unfrozen and frozen black spruce logs was studied. The power, energy consumption, and torque were also measured for both temperature conditions. The experiment consisted of debarking logs using three overlaps (8, 27, and 43%) at two temperatures (−12°C and +20°C). Debarking quality was evaluated by the proportion of bark remaining on log surfaces and by the amount of wood in bark residues. Log characteristics (dimensions, eccentricity, and knot features), bark/wood shear strength (BWSS), moisture content, and basic densities of sapwood, inner, and outer barks were measured and treated as covariates. Experiments revealed that tip path overlap affects debarking quality for both temperature conditions: the amount of bark remaining on log surfaces decreased, and the proportion of wood in bark residues increased as tip path overlap increased. In addition, the effects of bark/wood shear strength, the proportion of knot area and sapwood, inner and outer barks densities, and moisture content on debarking quality criteria were analyzed. The mean power, energy consumption, and torque increased as the tip path overlap increased. These parameters were also positively affected by the log diameter and BWSS for frozen logs. The results give helpful information to improve debarking quality within the studied range of overlaps, log characteristics, and debarking parameters with efficient energy use. [ABSTRACT FROM AUTHOR]

A conventional straight knife cutterhead and three helical knife cutterheads were tested for planing sugar maple (Acer saccharum Marsh.) and black spruce (Picea mariana (Mill.) B.S.P.) woods. The effects of helix angle and feed per knife (FK) on roughness, tactical perception, and anatomical features of the planed surfaces were evaluated. Rk and Rpk parameters were found to be more descriptive in evaluating the roughness of these woods and proved to be good indicators of tactile perception. Roughness increased as the helix angle and feed per knife increased for both wood species. Sugar maple showed smoother surface than black spruce. Surfaces planed with helical knives showed a fuzzy texture resulting from cell-wall fibrillation. For sugar maple wood, the differences in roughness between straight and 40° helical knives were small. Therefore, the latter must be preferred for planing this species. Roughness of planed black spruce also increased as helix angle increased and in this case its effect depended on FK. The straight knife produced the lowest roughness, for all studied FKs. Planing with helical knives produced higher roughness as a result of cell-wall fibrillation. This defect was more pronounced than that of sugar maple, and by far more present with helical knives of 50° and 60°. Therefore, straight knives working at low FK (1.3 mm) should be preferred for planing black spruce wood when roughness is a critical concern. Possible benefits provided by rougher surfaces planed by helical knives are discussed. [ABSTRACT FROM AUTHOR]

The cutting speed (CS) and feed per knife (FK) are among the most important variables affecting chip size produced by chipper-canters. Nine groups of black spruce logs were processed at three CS (20, 25, and 30 m/s) and three FK (19, 25, and 32 mm). Each log was processed under frozen (−13°C) and unfrozen (19°C) conditions. Chip size was assessed by thickness and by width/length. Chip size increased as CS decreased and FK increased. Frozen logs produced thinner chips and higher proportions of small chips. The weighted mean chip thickness (WCT) increased as the FK increased and CS decreased. The highest accepts proportion by thickness was obtained at 19 mm FK and 20 m/s CS, while the highest width/length accepts were produced at 32 mm FK and 20 m/s CS. Grain angle and knot proportion were the most significative covariates for chip size. Regressions showed that FK, CS, knot proportion, grain angle, and taper were the best predictors for WCT, explaining 86% and 81% of the WCT variations for frozen and unfrozen logs, respectively. Therefore, a combined evaluation of cutting parameters and raw material is essential to predict WTC, reduce chip size variations, and thus improve chip quality. [ABSTRACT FROM AUTHOR]

A conventional straight knife cutterhead and three helical knife cutterheads were tested for planing black spruce wood (Picea mariana (Mill.) B.S.P.). Effects of helix angle and feed per knife (FK) on maximum cutting forces and sound level were evaluated. A 3-axis dynamometer and an array microphone were used to simultaneously record the forces and the sound level, respectively. Parallel (FP), lateral (FL), resultant (FR) forces, and sound level increased as FK increased. Helical tools produced lower FP, positive and negative normal forces (FNP and FNN), and FR. Parallel forces tended to decrease as helix angle increased at high FK (4.7 mm). Differences among helical tools were not significant for normal and resultant forces. Cutterheads with the two highest helix angles (50° and 60°) produced higher FL at low (1.3 mm) feed per knife. Impacts of these cutting forces on the production of surface defects and ways to reduce them were discussed. Helical cutterheads considerably generated lower sound pressure level, with a maximum difference of up to 11.5 dB(A). [ABSTRACT FROM AUTHOR]

Four matched groups of 15 black spruce logs were processed with a chipper–canter at temperatures of 20, 0, −10, and −20°C. Each log was transformed at two moisture contents (MCs) (green and air-dried) using two cutting widths (CWs) (12.7 and 25.4 mm). Mean MC for each CW was assessed from a sample of the obtained chips. The results showed that mean power, energy consumption, and specific cutting energy were significantly affected by the temperature and CW, and in a lesser degree by the MC. These parameters were greater when cutting frozen logs. Mean power and energy consumption were higher at the larger CW, as a result of the higher volume of removed wood. However, specific cutting energy increased as CW decreased. This behavior was related to the higher level of fragmentation occurred with the smaller CW. These results are useful to estimate changes in energy requirements occurred within the range of cutting conditions studied here. [ABSTRACT FROM AUTHOR]

The effect of the radial force applied by a ring debarker tip to frozen black spruce logs, obtained at three positions on the stem, was studied. A one-arm ring-debarker prototype was developed, which controlled the radial force, rake angle, and cutting and feed speeds. The experiment consisted of debarking logs using three different levels of radial force. The rake angle (80°), tip overlap (20%), and cutting and feed speeds were kept constant. Debarking quality was evaluated by two criteria: the proportion of bark remaining on log surfaces and the amount of wood in bark residues. Log characteristics (dimensions, eccentricity, and knot features), bark/wood shear strength, and basic densities of sapwood and bark were also measured. Experiments revealed that log position on the stem did not affect debarking quality. The results also showed a significant effect of the radial force: the amount of bark remaining on log surfaces increased and the proportion of wood in bark residues decreased as radial force decreased. The effects of log eccentricity, bark/wood shear strength, and the proportion of knot surface on the debarking quality were examined. These results give useful information to improve debarking quality within the studied range of radial force, log diameter, and debarking parameters. [ABSTRACT FROM AUTHOR]

In northern countries, engineered wood products are widely used for the construction industry. Recently, a concern has been raised regarding a slow freezing rate in green wood (of the order of 1 °C / h up to 25 °C) that could greatly reduce wood strength. Thus, logs processed during winter might produce lumber with a lower mechanical strength in service than those produced during summer. Therefore, the main objective of this study was to evaluate the influence of the freezing rate on the selected mechanical properties of balsam fir (Abies balsamea [L.] Mill). Three groups of 17 planks (20 mm x 20 mm x 1200 mm) were exposed to three freezing rates (10 °C/h, 5 °C/h, 1 °C/h) and another group was kept as a control group. After the freezing treatments, the planks were stored in a conditioning room at 20 °C and 65% relative humidity to obtain an equilibrium moisture content of 14%. Samples of 10 mm x 10 mm x 190 mm and 10 mm x 10 mm x 40 mm, for static bending and parallel compression to the grain tests were then prepared, respectively. The results showed that the freezing rate did not have any effect on the mechanical strength of balsam fir wood. [ABSTRACT FROM AUTHOR]

Twelve-year-old Japanese larch (Larix kaempferi[Lamb.]Carr.) trees of 20 different progenies and/or provenances were sampled at one site in the Mauricie region of Quebec. Two standard samples were obtained at breast height and closer to the bark from each tree. Partial and total radial, tangential, and volumetric shrinkages, and tangential/radial (T/R) shrinkage ratios were assessed. All of these variables were significantly affected by the progeny/provenance. Drying defects are one of the main reasons for downgrading larch lumber; thus,T/Rshrinkage ratio was considered for the selection of progenies/provenances for lumber production purposes. Lowest partial and totalT/Rshrinkage ratios were obtained with progenies/provenances 8964, 8904, 8962, 8957, 8907, 8927, 7283, and 7795. Among them, lowest partial and total tangential, radial, and volumetric shrinkages were found in progenies/provenances 8964, 8962, and 8907 as well. Other physico-chemical (mechanical properties, density, extractive content) and silvicultural (growth rate) attributes should also be taken into consideration for an adequate selection of progenies/provenances according to the specific final utilization. [ABSTRACT FROM AUTHOR]

Fifteen stems of jack pine (Pinus banksianaLamb.) of 3 commercial thinned plots (control, moderate, and intensive thinning) and 15 stems of black spruce (Picea mariana(Mill.) B.S.P), both coming from the Abitibi-Témiscamingue region – Canada, were cross-cut into three 2.4 m length sections: bottom, middle, and top logs. Logs were processed with a chipper-canter at three cutting widths (12.7, 19.1, and 25.4 mm), producing chips and a three-faced cant. The middle section of the cant was used to evaluate surface quality across the grain on each face. Roughness and waviness parameters and depth of torn grain were recorded. Knot characteristics were assessed in the three cant faces. Poorer surface quality was found in the lower part compared to the upper part of the cant for both species. At larger cutting widths, jack pine logs coming from a natural stand showed lower surface quality compared to logs from thinned stands. Black spruce waviness increased with the cutting width and stem height. These results were attributed to the increase of forces and vibration when cutting at larger cutting widths, which was worsened by the presence of bigger, more numerous knots at the control plot and in the top logs. Black spruce had deeper torn grain compared to jack pine. Their differences in knot characteristics resulted in a maximum torn grain depth favored by the presence of more knots rather than by bigger knot size. Other knot characteristics, such as the position of the knots in the cant face, the insertion angle of the branch and the distribution of the knots around the log, should be studied to better understand the relationship between torn grain formation and knottiness. [ABSTRACT FROM PUBLISHER]