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Silva Fennica 1926-1997
Acta Forestalia Fennica

Articles containing the keyword 'sawing'.

Category: Research article

article id 1393, category Research article
Werner Poschenrieder, Andreas Rais, Jan-Willem G. van de Kuilen, Hans Pretzsch. (2016). Modelling sawn timber volume and strength development at the individual tree level – essential model features by the example of Douglas fir. Silva Fennica vol. 50 no. 1 article id 1393.
Highlights: An individual tree timber growth and quality model toolbox was designed; It realistically predicts an increase of bending strength with planting density; Prediction was shown to be based on consideration of essential intrinsic variables; Height‑diameter‑allometry depending on planting density was effective; Consideration of cambial age and knot area ratio was crucial.

We designed a streamlined timber growth and quality model that aims at the effect of stand management on the efficiency of wood resource use. Applying the R based module toolbox to experimental plots of Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) we analysed essential model features for reflecting the influence of planting density on board strength. The current version realistically predicted a significant increase of centre board bending strength at tree age 40 with initial stand density. Model performance gained clear advantage from a) parameterisation of height to diameter allometry as dependent on planting density b) consideration of cambial age and cross‑sectional knot area in board strength computation. Crown shape was less decisive. The model produced a significant effect of planting density even after a whole rotation period of 70 years as well as a realistic spectrum of board bending strength.

  • Poschenrieder, Technische Universität München, Chair of Forest Growth and Yield Science, Hans Carl von Carlowitz Platz 2, 85354 Freising, Germany ORCID ID: E-mail: (email)
  • Rais, Technische Universität München, Chair of Forest Growth and Yield Science, Hans Carl von Carlowitz Platz 2, 85354 Freising, Germany; Technische Universität München, Holzforschung München, Winzererstrasse 45, 80797 Munich, Germany ORCID ID:E-mail:
  • van de Kuilen, Technische Universität München, Holzforschung München, Winzererstrasse 45, 80797 Munich, Germany ORCID ID:E-mail:
  • Pretzsch, Technische Universität München, Chair of Forest Growth and Yield Science, Hans Carl von Carlowitz Platz 2, 85354 Freising, Germany ORCID ID:E-mail:
article id 459, category Research article
Tomi Tulokas, Jawdat Tannous. (2010). Research method and improvement of log rotation in sawmills. Silva Fennica vol. 44 no. 1 article id 459.
Log rotation studies were performed at 14 Finnish sawmills during the years 2003–2005. In the investigation of automatic log rotation, the materialized degree of log rotation for each log was calculated from photos captured from a digital video recording. Rotation errors (D) for individual logs and again the accuracy of the automatic log rotator was determined from optimized angle values of the log measuring system and materialized angle values calculated from the still photos. The accuracy of the log rotation varied considerably between sawmills. The rotation error average of the automatic log rotation varied from –23.6° to +11.4°. This means that in some cases the logs were under-rotated and in some they were over-rotated, on an average. Standard deviation of the rotation error (s) of the automatic rotator varied from 4.4° to 22.9°. The results of the simulation indicated that the performance of the log rotation system can be improved by adjusting the log rotator control. In addition to the zero degree error on an average rotation (or near to zero), the corrected values have a significantly smaller standard deviation of the rotation error, and the number of correct rotations was significantly higher compared to the situation before the adjusted rotation commands. At Sawmill 1, standard deviation of the rotation error was reduced by 40.9% from 14.9 degrees to 8.8 degrees. At the same time the number of correct rotations (–10°≤ D ≤ +10°) increased 4.0 fold from 20.1% to 79.4%. At Sawmill 2, standard deviation of the rotation error was reduced by 23.8% from 10.5 degrees to 8.0 degrees. At this sawmill, the rate of accepted rotations increased 1.9 fold from 42.6% to 81.0%. According to previous research, 2.5° decrease in standard deviation of the rotation error (from 10.5 to 8.0°) in square sawing means about 0.5% increase in value yield. For example with 10 million Û annual sales of sawn timber this means 50 000 Û extra profit.
  • Tulokas, Centre for Timber Engineering, Edinburgh Napier University, 10 Colinton Road, Edinburgh EH10 5DT, UK ORCID ID:E-mail: (email)
  • Tannous, School of Engineering and the Built Environment, Edinburgh Napier University, 10 Colinton Road, Edinburgh EH10 5DT, UK ORCID ID:E-mail:
article id 197, category Research article
Veli-Pekka Ikonen, Seppo Kellomäki, Heli Peltola. (2009). Sawn timber properties of Scots pine as affected by initial stand density, thinning and pruning: a simulation based approach. Silva Fennica vol. 43 no. 3 article id 197.
The aim of this work was to analyze how different management schedules with varying initial stand density, thinning and artificial pruning of branches affect the quality, quantity and value of sawing yield in Scots pine (Pinus sylvestris L.). For this purpose, an integrated model system was employed and further developed to simulate: i) the three dimensional structure of the crown and stem of an average tree grown in a stand related to the changes in the within-stand light conditions as caused by the stand management, and ii) the sawing of logs into pieces and their quality grading based on the size and number of living and dead knots on the surfaces of sawn pieces. To maximize the quality of sawn timber, relatively dense stand is desired in the early phase of the rotation to reduce, especially in the lower part of stem, the growth of branches, and to increase the rate of dying and pruning-off of branches. In the later phase, a relatively sparse stand is desired to increase the self-pruning of branches and the occlusion of knots. However, in any case, artificial pruning is needed to maximize the knot-free zone of the stem. Also the value optimization of individual sawn pieces affects the quality and value of sawn timber. Because, only average tree was simulated, the differences between scenarios for stem volume were small. In the future, further model development is needed to analyze the development of crown and stem properties of trees with different status in a stand.
  • Ikonen, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: (email)
  • Kellomäki, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail:
  • Peltola, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail:

Category: Article

article id 7184, category Article
Bror-Anton Granvik. (1967). Havusahatavaran valmistus kenttäpyörösahalla : työtieteellinen tutkimus. Acta Forestalia Fennica vol. 84 no. 3 article id 7184.
English title: The preparation of coniferous sawn goods using circular saws. A work study.

The objectives of the paper were to find out structure of the sawing time when using field circular saws, influence of the different factors on the sawing time and its structure, average sawing time per unit of raw material and sawn goods, and the fundamentals for the creation of an equitable system for the determination of the basis of payment in sawing work. The observations of the time study were made on both a single log and a work period basis. The material was collected using four saws of different brands.

The results showed that the season when the work was done, and top diameter of the logs to be sawn affected the constant times included in the total sawing time and the time used for sawing of center pieces. While the tree species did not affect the constant times, the grade of the logs of different tree species did have effect, especially in winter sawing. The factors affecting the different phases of the work are described in detail. The length of sawing time was longer in the winter than in the summer. The preparatory jobs in sawing required in average 82 cmin per log, and the time increased with increasing top diameter. The actual sawing is the most time-consuming part of the work, it took in average 132 cmin. 

The PDF includes a summary in English.

  • Granvik, ORCID ID:E-mail:
article id 7463, category Article
Paavo J. Ollinmaa. (1955). Koivun vetopuun anatomisesta rakenteesta ja ominaisuuksista. Acta Forestalia Fennica vol. 64 no. 3 article id 7463.
English title: On the anatomical structure and properties of the tension wood in birch.

The investigation concerns with the strength of the eccentric growth accompanying formation of tension wood in silver birch  (Betula pendula Roth.) and downy birch (Betula pubescens Ehrh.), behaviour of wood in wood-working machines and its macroscopic characteristics, its microscopic and sub-microscopic structure, chemical composition, resistance against certain chemicals, physical properties, and the strength characteristics of wood.

The most detrimental properties of tension wood used in wood working industry are high longitudinal shrinkage, warping, twisting and checking. The wooliness of the cut is unwanted, for instance, in plywood and furniture. In pulp industry tension wood is better raw material than normal wood because it yields more and purer cellulose than normal wood. However, it has poorer strength properties.

The PDF includes a summary in English.

  • Ollinmaa, ORCID ID:E-mail:
article id 4768, category Article
Veijo Heiskanen. (1968). Havaintoja eräiden vikaisuuksien vaikutuksesta mäntytukkien sahauksessa. Silva Fennica vol. 2 no. 3 article id 4768.
English title: Influence of some log defects in sawing of pine logs.

The present paper presents studies on the influence of some relatively common defects of Scots pine logs in Northern Finland on both the sawing yield and on the quality of the sawn goods. The study was based on test sawing of 25 logs for each of the defects (upright limb, heart shake and various kinds of wounds and scars) at Karihaara sawmill. The yield was graded into grades used for export timber according to the system of the sawmill. The proportion of the different export grades (U/S), fifths, sixths and culls) were used as characteristics together with the ratio of raw-wood consumption expressed as cu.ft/std.

Upright limbs occurring in a piece of sawn timber was shown to lower its quality to fifth grade in 43.5%, to sixth grade in 46.8% and to the category of culls in 6.5% of all cases. Only 3.2% of the cases the piece remained in U/S-grades. The size of the upright limb was the most important factor lowering the quality and affecting the ratio of raw-wood consumption.

Heart shakes are relatively common defects in pine logs deriving from over-mature trees. The quality-decreasing influence on the sawing yield depends clearly on the length of the shake in the cross-section. The same characteristics also decreases the ratio of raw-wood consumption. In addition, twisting and star shakes are considerably more harmful than straight ones. If rot occurs in connection with shakes, the places marred by the shakes are only capable of yielding sixth-grade sawn goods or culls.

Scar encountered in logs affect the sawn yield and its quality to quite a varying degree, but these defects themselves may also vary considerably both in size and quality. The length of the scar is highly significant as a quality-decreasing factor. If, in addition, rot is encountered, the defect is of a severe nature.

The PDF includes a summary in English.

  • Heiskanen, ORCID ID:E-mail:
article id 7186, category Article
Bror-Anton Granvik. (1968). Sahaustuloksen määrä ja laatu havutukkien kenttäpyörösahauksessa. Acta Forestalia Fennica no. 86 article id 7186.
English title: The quantity and quality of the sawing yield in sawing coniferous logs with circular saw.

The aim of the study was to find out the ratio of raw wood consumption and the quantity and quality of the sawing yield using circular saws. The unit of study was one single log, the Norway spruce logs were divided into two grades and Scots pine logs in three grades. The principal material of the study was collected in 1950-51 using four types of saws of type EKA-50. The data consisted of 1,690 logs.

On the basis of the material, the efficiency of centre-piece sawing was 63.9% of the technical volume. On the average, 32.1% was unsorted goods, 11.5% fifths, 19.1% sixths and 1.2% culls. For spruce, the efficiency was superior to pine, which means that the consumption of raw wood for preparation of one standard of sawn goods is smaller in spruce than in pine. The volume of side boards trimmed reached about 2% of the total log volume. The efficiency of sawing and the ratio of raw-wood consumption were calculated both on the basis of the estimated and actual volume of trimmed goods. The raw-wood consumption is particularly good in logs of small and large top-diameter.

Goods sawn with circular saw have a characteristic shape. They are thinner at the ends than in the middle parts, and the deviation from the correct measure is larger in the first than in the last end of the pieces. They are also wedge-shaped because of the first piece sawn is thinner than the second one. The deviation from the correct measure exceeded the allowance for shrinking in seasoning. The goods are often under sized even if surplus measure occurs. In goods sawn using frame saws, however, it was difficult to discover any deviation from the correct measure.

The PDF includes a summary in English.

  • Granvik, ORCID ID:E-mail:

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