實木蒸汽彎曲之研究

Studies of The Solid Wood Steam Bending

黃清吟(Chin-Yin Hwang)

《林業試驗所研究報告季刊》 3卷2期 (1988/06) Pp. 99-120

https://doi.org/10.7075/BTFRI.198806.0099

摘要

本研究旨地探求常用加工樹種之彎曲適性。以省産木荷及相思樹爲材料，於飽水狀態下蒸汽處理30分鍾，再以滾輪式彎曲成型機彎曲並置於烘箱中乾燥成型，拆卸模具之同時即逐一評估其缺點種類及彎曲品等，複存放於室溫之變化溫濕度條件下歷時八週，定期記錄觀察曲率半徑及含水率之經時變化情形，以此探討樹種曲率變徑、截角與否、厚度、成型溫度等因子之影響，試驗結果歸納如下：
①厚度及曲率半徑影響實木彎曲成功率，厚度愈小曲率半徑愈大，彎曲成功率愈大，截角與否則不具效應。
②木荷之彎曲適性優於相思樹，允宜推廣。惟其乾燥缺點仍待克服。
③延長蒸汽處理時間可望充分軟化相思樹提昇其變曲成功率。
④二樹種在乾燥成型後之存放初期，複元性並無顯示差異，八週後則出現明顯之歧異，木荷爲spring in相思樹爲spring back。曲率半徑僅影響初期複元性。
⑤含水率與存貯時間之對數成線性相關，複元率與含水率、存貯時間均呈二次曲線相關。

關鍵字

實木彎曲 ； 彎曲層積 ； 曲木 ； 複元性 ； 瞬間回複 ； 潛變回複

並列摘要

The trend of Taiwan's furniture industry is moving toward high-quality items. Upgrading the processing technique is an urgent task. Bentwood furniture originated a century ago and is still popular in certain foreign markets. The major limitation of Taiwan's bentwood furniture makers is poor bending techniques which lead to few defect-free parts and raised the cost of production. The purposes of the studies were to evaluate the bendability of some local commercial woods and the feasibility of producing defect-free bentwood parts from them.
Chinese guger-tree (Schima superba) and Taiwan acacia (Acacia confusa) materials were sawn and planed into test specimens 5.5 by 2 or 3cm in cross section. The lengths of the pieces depended on the bending curvatures. The specimens were kept in a water-saturated condition and plasticized with 100℃ steam at 1.5kg/cm2 pressure for 30 min. After steaming, the materials were transferred quickly to a roller-type solid wood bending equipment, bent, then set and dried under restraint in an oven for 20 to 22 hrs. Right after the molds were removed, the bending ratings and the kinds of failures were recorded. During the storage duration under room conditions for eight weeks, the curvature deviations were checked periodically.
The results indicated that:
1) The bending ratings of Chinese guger-tree were influenced by the thickness of the specimens and its curvature. Percentage of acceptable bent stocks increased with decreasing thickness and increasing radius. The bending ratings of the specimens were similar, irrespective of beveling.
2) Chinese guger-tree was easier to bend than Taiwan acacia. It could be used to make good quality bentwood furniture, provided its drying problems be solved.
3) Prolonged steaming may improve the bending ratings of Taiwan acacia.
4) At the start of storage, the percentages of curvature recovery (spring back) were roughly the same for the two species. After 8 weeks storage they tended to differ as Chinses guger-tree sprang in (decrease in radius), and Taiwan acacia sprang back (increase in radius). Statistical analysis also indicated that the final curvatures of the bent stocks correlated with the degrees of instantaneous recovery.
5) There were second order relationships between recovery and moisture content and storage days, respectively.

並列關鍵字

Solidwood bending ； laminated bending ； bentwood ； recovery ； spring back ； spring in ； instantaneous recovery ； creep recovery