自动反拉式换位夹持苎麻剥麻机设计与参数优化

    Design and parameter optimization of the automatic reverse pulling type shift clamping device for ramie stripping machine

    • 摘要: 针对目前普遍使用且依靠人力喂入及反拉的苎麻剥麻机劳动强度大、安全性差、剥麻质量不稳定等问题,该研究以“川苎11号”苎麻为研究对象,设计了一种自动反拉式换位夹持苎麻剥麻机。首先对苎麻茎秆物理尺寸和力学性能参数进行测量,确定采用双夹持机构与同步带夹持输送、电机驱动夹持机构翻转换位、双滚筒反向剥麻的技术方案。进而对剥麻装置、夹持机构等主要部件进行结构设计和理论分析,确定苎麻剥麻机结构和剥麻滚筒转速、反拉速度、喂入角度等工作参数。然后分析苎麻茎秆剥打过程并建立仿真模型,运用ANSYS/LS-DYNA模块对剥麻过程进行单因素仿真试验,分析了木质部去除量、韧皮部损失量等,仿真结果表明,剥麻滚筒转速、反拉速度、喂入角度分别在350~650 r/min、0.2~0.4 m/s、5°~15°范围内时的剥麻效果较好。根据Box-Behnken试验设计方法,开展三因素三水平正交试验,通过方差分析和响应面分析,得出反拉式换位夹持苎麻剥麻机的最优工作参数为:剥麻滚筒转速451.047 r/min,反拉速度0.319 m/s,喂入角度10.728°;样机试验表明最优工作参数下的平均鲜茎出麻率为5.03%,平均原麻含杂率为1.14%,满足苎麻剥麻机技术标准。该换位夹持装置能够实现苎麻夹持喂入与自动反拉,简化剥麻机结构,提高剥麻机作业性能和剥麻质量,研究结果可为轻简型苎麻自动剥麻机的研发提供技术参考。

       

      Abstract: A ramie stripping machine has been commonly used in modern agriculture in recent years. However, the current manual feeding and back-pulling cannot fully meet the large-scale production, due to the high operational intensity, low safety, and unstable stripping quality. In this study, a double-drum stripping device was designed to replace the manual feeding and reverse-pulling in an automatic ramie fiber stripping machine. There were also the different mechanical properties between the ramie fiber layer and the woody part. Firstly, some measurements were performed on the physical dimensions and mechanical property parameters of "Chuanzhu No. 11" ramie stalks. Then, the technical solution of a double clamping mechanism was proposed with the synchronous belt clamping and conveying, motor-driven clamping mechanism flipping and changing position, and double-drum reverse stripping. The ramie stalks were fed directly, and then stripped at the base and tip of the ramie stalks in turn by the changing position of the clamps. The toothed rubber clamping plate was used to hold the stalks. The grooves and projections of the toothed rubber plate were firmly held to prevent the stalks crushed by the clamps and slipping out. The operation of the ramie stripping machine was divided into four steps: the straw feeding, base stripping, tip stripping, and collecting ramie skin. The key components mainly included the transposition clamping, lateral feeding, and ramie stripping device. The mechanical analysis of double-drum ramie stalk stripping showed that the stripping force was closely related to the drum speed. A mechanical test was carried out to investigate the relationship between the stalk feeding angle and stripping force. The results showed that the stalk feeding angle and stripping force shared a highly significant negative linear correlation. The structural design and theoretical analysis were performed on the main components in the ramie stripping device and clamping mechanism. After that, the structure and motion parameters of the ramie stripping machine were determined, including drum speed, reverse-pulling speed, and feeding angle. Furthermore, a single-factor simulation model was established using ANSYS/LS-DYNA to simulate the process of stripping and the amount of xylem removal, the loss of the bast fiber layer, and the force of the feeding direction. Previously, the ramie stalk actual stripping process was analyzed and a simulation model was developed. The structure of the ramie stalk was also analyzed during this time. The optimal ranges of parameters were achieved for a better stripping effectiveness: the roller speed of 350-650 r/min, the reverse-pulling speed of 0.2-0.4 m/s, and the feeding angle of 5°-15°. A three-factor and three-level orthogonal test was conducted, according to the Box-Behnken method. The results showed that the drum speed, reverse-pulling speed, and feeding angle posed the significant effects on the fiber percentage of fresh stalk, and the impurity rate of raw fiber using ANOVA and response surface analysis. In addition, a significant coupling effect was found in the interaction of drum speed and reverse-pulling speed, as well as each experimental factor, but there was no a simple linear relationship. The optimal operating parameters were obtained for the ramie stripping machine with the reverse-pulling clamping: the stripping drum speed of 450 r/min, the reverse-pulling speed of 0.32 m/s, and the feeding angle of 11°. Finally, the validation test of the ramie stripping machine prototype was carried out using the optimized parameters. A better performance was achieved in an average fresh stem fiber yield of 5.03% and an average impurity rate of 1.14% of raw ramie, fully meeting the national technical standards of the ramie stripping machine. The transposition clamping device can be expected to realize the ramie clamping and feeding, as well as the automatic reverse pulling. The simple and optimal structure of the ramie stripping machine was had improved the performance and quality of ramie stripping. The finding can provide a technical reference for the development of an automatic lightweight ramie stripping machine.

       

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