Development of continuous pressing method for producing LVL cylinder

本文提出了一种改进的加压干燥方法，用于LVL气缸的原料SUGI单板。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形接头的末端接头。试制的机器运行良好，所制的连接件与未连接件的强度相当。采用带射频加热功能的履带式连续压力机，对一种无级成型LVL进行了压制。压力机有一个300毫米宽，700毫米长的冲压件。用一个接一个的带电极的木材成型夹具进行连续模压。产品为外径390mm，厚度30mm的LVL圆柱体的1/6零件。实验结果表明，当冲压件长度扩大到7 m时，该方法在1 m/min的生产速度下是可行的。将成型的6块lvl用RF胶在切槽式接头中边缘连接，制成长度为5,400 mm的空心圆柱形立柱。柱内填充密度为0.38 g/cm^2的聚氨酯树脂泡沫。充填后的桩侧抗压强度比未充填时提高了40倍。采用有限元法计算应力分布，并用于破坏准则的预测。用工艺纸加固的横向细长贴面带缠绕到加热的山钻上，以制造具有螺旋缠绕贴面的LVL。这种技术通常用于制造纸管。试验成功，该技术在LVL生产中的应用前景广阔。

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.