Development of continuous pressing method for producing LVL cylinder

本文提出了一种改进的单板层积材筒体原材料SUGI单板的热压干燥方法。实验结果表明，该方法比传统方法更有效。设计了一种用于单板指接的端接器。试验装置运行良好，制成的连接件强度与非连接件相当。采用具有射频加热功能的履带式连续压机压制无端成型单板层积材，压制件宽300 mm，长700 mm。一个接一个地使用由木材制成的具有电极的成型夹具来进行连续的模压。产品是LVL圆柱体的1/6部分，外径390 mm，厚度30 mm。实验结果表明，这种方法的可行性，在1米/分钟的生产速度，如果挤压部分的长度延长到7米。六件成型LVLs的边缘连接在舌槽型接头与RF胶，使一个中空的圆柱形柱的长度为5400毫米。桩内填充密度为0.38 g/cm^2的聚氨酯树脂泡沫。充填后桩的抗侧压强度比未充填桩提高了40倍。用有限元法计算了单板层积材的应力分布，并将其用于预测单板层积材的破坏准则。将牛皮纸增强的横向细长单板带缠绕到加热芯轴上，制成螺旋缠绕单板层积材。这种技术通常用于制造纸管。试验结果表明，该技术在单板层积材生产中具有广阔的应用前景。

An improved press-drying method of SUGI veneers which were used as raw materials for LVL cylinders in the present Research was proposed. The experimental results showed the new method was more effective than the conventional ones. An end-jointer for making finger-type joints of veneers was designed. The machine set up in trial worked well and the jointed parts made by this machine had strength comparable with that of non-jonted parts.A caterpillar-type continuous press with a radio ferquency heating function was used for pressing an endless molding LVL.The press had a pressing part 300 mm wide and 700 mm long. Molding jigs made of wood with electrodes were used one after the other to make a continuous mold pressing. The products are 1/6 parts of a LVL cylinder with 390 mm outer diameter and 30 mm thickness. The experimental results showed the feasibility of this method in the production rate of 1 m/min if the length of the pressing part was extended to 7 m.Six pieces of the molded LVLs were edge-jointed in tang-and-groove type joints with RF glue to make a hollow cylindrical post of 5, 400 mm length. Urethane resin foam with density of 0.38 g/cm^2 was filled inside the post. The filling was very effective to improve the lateral compressive strength by 40 times as that of a non-filled post. The stress distribution was calculated by the finite element method and used for the prediction of the failure criteria.Slender veneer tapes of lateral direction reinforced with craft papers were winded to a heated mandrill to manufacture an LVL with helical-winded veneers. This technique is commonly used for manufacturing paper tubes. The trial seemed successful and the application of the technique to LVL production will be promising.