| In our country, forest resource is deficient relatively, and timber output is decreasing yearly associated with the implementation of the "Natural Forest Protection Project". Big-diameter wood is becoming more and more scarce, but the percentage of timber produced from plantation forest in intermediate cutting and harvest cutting is becoming more and more abundant, so it is important to high efficiently use available forest resource.The properties of Larix gmelinii Rupr plantation are different from mature wood, which are soft quality, low strength and hardness, bad size stability and low out-put. Additionally, the timber produced from Larix gmelinii Rupr platation generally contain some natural defects, such as knots, resin, difficult to dry and easy to shrinkage, so its process and use is restricted. Through studying the glued laminated techniques and processes of small-diameter Larix gmelinii Rupr wood, it will increase the operating factor and competitive strength of wood and wood production. It has a very important significance for buffering the contradiction between the supply and requirement, and realizing the transformation from high efficient utilization to sustainable development. In a word, it will bring significant economical and society benefit.The aim of this paper is to study the wood property of small-diameter Larix gmelinii Rupr platation in Heilongjiang province based on forefathers study results, to realize the optimization design of Polygonal Cutting by means of mathematical method, and to determine the drying process and glued laminated technology. Some conclusions are showed as follows:(1)There are the variations of Wood Properties within and between Individual Trees for Larix gmelinii Rupr, such as the basic density, late wood percent, tensile strength parallel to grain, compression strength parallel to grain and modulus of tensile elasticity. With in all these, the basic density, late wood percent and tensile strength parallel to grain have more variation, others are small. The basic density is between 0.40-0.45g/cm3. Late wood percent is between 16.96-19.86%. Tensile strength parallel to grain is between 86.15-99.21MPa. Compression strength parallel to grain is between 46.92-49.04MPa. Modulus of tensile elasticity is between 8878-11263MPa. All of above are smaller than mature wood, it means that small-diameter Larix gmelinii Rupr plantation are suit for materials as structural glulam and non- structural glulam.The air dry shrinkage rates of small-diameter Larix gmelinii Rupr plantation are 0.49% larger than that of mature wood in radial, and 0.55% in tangential.(2)According to the wood geometrical feature, and considering operability, we think that regular hexagon cutting is the best select. Divided log section as 60°angle, it can formed triangle polygonal wood that having some taperingness along length. The theoretical out-put of small-diameter Larix gmelinii Rupr plantation in polygonal cutting is 66.16%. Using self-made polygonal cutting machine, we made cutting experiment. The result showed cutting made better effect. Experiment out-put is between 54.78%-57.14, the value is lower than the theoretical out-put but it's higher than other cutting type. Service behavior of polygonal cutting machine and precision reached GB/T4384-1993 standard, it also reached the demand of Heilongjiang province science and technology plan(GB06B305-1).(3)By experimental study under different drying temperature of small-diameter Larix gmelinii Rupr plantation in polygonal cutting, the tangential shrinkage coefficient showed two kinds of trend. One is first decreased and then increased from pith to surface; the other is increased gradually from pith to face. These trends were decided by the frequency of tensile stress in wood drying process. Moreover, drying temperature could affect the response of wood shrinkage coefficient. The shrinkage coefficient of wood was large at low temperature, and decreased firstly and then increased as drying temperature increased. It also founded a better quadratic correlation between drying temperature and shrinkage coefficient of different part in wood.Drying curves and drying evenness of small-diameter Larix gmelinii Rupr plantation in polygonal cutting showed different states and results under different drying schedule. The drying curve showed continue curve, the drying time was longer and the drying evenness was better under conventional drying schedule. Under varying drying schedule and hard drying schedule, the drying curve showed two stages, the drying time was shorter and the drying evenness was worse than that under conventional drying schedule. Drying time and drying evenness under varying drying schedule were better than that under hard drying schedule. Test showed that varying drying schedule was fit for the drying of small-diameter Larix gmelinii Rupr plantation in polygonal cutting.Based on the test, the paper drafted varying drying schedule to use in practice. This schedule made better result. Drying rate is better. All of indexes are with in scope of criterion. This schedule could use in practice for small-diameter Larix gmelinii Rupr plantation in polygonal cutting.(4)Using self-made planning machine, we made production test. The result showed that two joint face angled 60°that could meet the demand of next process. Planning machine satisfied the basic demand of polygonal wood, and realized the paneled in technique and technologically.(5)Glue jointed the polygonal cutting wood by using self made glue jointer, and then determined mechanical properties after gluing. Results showed that:shear strength is between 8.2-10.6MPa, wood failure in room is between 86-100%, peel of dip is between 0.00-10.00%, Water immersion out room is between 0.00-4.88%, bending strength is between 43-99MPa and modulus of tensile elasticity is between 10×10~3-10×10~5MPa. All this indexes after gluing showed that the glue jointer could meet the use demand of small-diameter Larix gmelinii Rupr platation Rupr in polygonal cutting, and the jointed timber can meet the use demand.
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