帯鋸の振動特性に関する一考察 : 振動モードと振幅

Abstract

800mm小割用帯鋸盤を用い, 腰入れ・背盛り量の異なる帯鋸 (厚さ0. 82mm, 幅102mm) について, 静止時, 自由部分中央の衝撃的加振による振動の過渡応答を鋸の前後縁で測定し, 振動モード, 固有振動数, 振幅などを調べ, これらにおよぼす鋸種, 鋸断面の引張応力分布の影響を検討した。その結果, 過渡応答は主にl次の曲げ, ねじりの減衰振動からなり, 理論モデルのインパルス応答と定性的に一致した。振動成分中ねじり振幅よりも大きかったたわみ振幅は, 緊張力の低下とともに増加するのみならず, 鋸車の傾斜による引張応力の鋸幅方向の減少に応じて増大し, この変化には鋸種による差は殆どないこと, ねじり振幅は緊張力の影響は受けるが引張応力分布の影響は受けないことがわかった。空転時の振動は主に衝撃時に観察された振動成分からなり, 振幅の鋸幅方向の変化も衝撃時のそれに対応した。

In order to clarify the vibration characteristics of band saw, transient response of band saws of different tensioning and back stretching radii (Fig. 2) was measured in both front and rear edges of a saw blade when the saw was excited impulsively at the halfway between wheel axes (Fig. 3). Vibration mode, natural frequencies, amplitude were analyzed and the influences of tensioning or back stretching and tensile stress distribution across saw width on the vibration characteristics were discussed. The transient vibration mainly cosisted of both flexural and torsional damped vibration of modal number one (Fig. 4) and corresponded to the impulse response of the modes analyzed theoretically (Fig. 1). Flexural amplitude was larger than torsional one (Fig. 5) and increased according to the decrease of the tensile stress due to the inclination of upper wheel, as well as to the decrease of tensile force (Fig. 6). This change was not influenced by saw tensioning nor back stretching. Torsional amplitude was not influenced by the stress distribution. Vibration of saws in idling mainly consisted of both flexural and torsional vibration of the lower modal numbers and amplitude was changed in saw width according to the vibration characteristics observed in shock excitation (Fig. 7).