本論文主要目的為降低工業用直驅式縫紉機之整體振動量。振動量測的基準轉速為正常使用之4,500rpm,而量測之位置則以機頭及針板為主。研究目標為從原始機頭振動加速度37.6 m/s2之峰值降低10~15 m/s2,降幅約26.6%~39.9%。 就振動研究部份,經由上大心之平衡相位量測,發現縫紉機運轉時,振動最大的狀況為針棒與送具行程同相時,且機頭內部機構如針棒等之運動影響振動量甚大。因此除了調整上述行程使之成為反向外,並改變上大心配重塊的配置方式,以對整體轉動平衡進行分析改善。經由計算不平衡量的方式,設計出配重塊的適當質量,安裝於上大心左側分隔槽之左方及右方位置,能使機頭振動加速度值由原始的37.97 m/s2降低至24.2 m/s2 (降幅36.3%),針板位置之振動加速度值也從原始的44.84 m/s2降低至28.06 m/s2 (降幅37.4%)。隨後,更進一步改用勁度較低之縫紉機腳隔振膠塊,亦能增加振動降低的效果。整體而言,配重塊之改變配合勁度較低之隔振膠塊,能使機頭加速度降低14.57 m/s2(約38.4%),針板位置之加速度也同步降低19.94 m/s2(約44.5%)。同時,藉由改變隔振膠塊之外型以降低其勁度,經由ANSYS分析結果,發現採用壁厚2.6mm側邊切四個槽之隔振膠塊,可得勁度為19N/mm之最適膠塊,能使機頭加速度由原始的38 m/s2降低至22.85 m/s2,降幅達39.9%已大幅減少縫紉機機頭之振動。
The study was aimed to reduce the vibration problem of an industrial sewing machine which has a servo motor direct drive system. All the test condition was based on a normal operation speed of 4,500 rpm that is the full speed of the machine. The vibration measurement locations were set at the head of the sewing machine body and the needle plate. It was expected to reduce an amount of 10 ~ 15 m/s2 on the head accelerations from the original peak acceleration of 37.6 m/s2 with a 26.6%~39.9% decrease approximately. For the study on vibration reduction, the first task was focused on the balance of the top drive shaft on the machine. It was found that the maximum vibration occurred when the needle stick and feed teeth were in phase during their travel, and those mechanisms inside the head of machine such as the needle stick has great effects on the vibration during operation. Thus, by adjusting the strokes of forgoing components to be in reversed phase and changing the weights on the top drive shaft, it is possible to improve the rotating balance of the machine. Thus, the reduction of vibration could be done through calculating the unbalance amount and designing the suitable balancing weights either on the left or the right housing locations of the top shaft. These measures could reduce the machine head’s vibration with an amount of 13.77 m/s2 (i.e. 36.3%) from the original 37.97 down to 24.2 m/s2. Meanwhile, the vibration on the needle plate was also reduced from the original 44.84 m/s2 down to 28.06 m/s2 with a 37.4% decrease. Furthermore, by using the lower stiffness vibration isolation rubber to support the machine, it can also reduce the vibration further. Finally, combining all these measures by changing the balancing weights of the top drive shaft and using the lower stiffness rubber feet, it can reduce the vibrations both on the machine head and on the needle plate with amount of 14.57 m/s2 (i.e. 38.4%) and 19.94 m/s2 (i.e. 44.5%) respectively. If using ANSYS software to redesign the rubber feet by cutting several slots on its side wall, their stiffness can be reduced further. It turned out that the best one for vibration isolation (stiffness 19 N/mm) was that with four slots cut and wall thickness of 2.6 mm. The overall vibrations at the sewing machine head will finally be reduced to 22.85 m/s2 with a 39.8% decrease which has far exceeded the design objective.
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