Analysis of tobacco stem shaping effect based on compression-set
In order to investigate the technical basis of the heavy rolling process for tobacco stems, the relationships between compression-set of tobacco stems and several influencing factors including stem structure, moisture content and roller clearance were studied. Compression-set is a professional term which means the thickness change of the material before and after compression. In this study, a compression-set-characterization method was developed to evaluate the shaping effect of tobacco stems, and the influence of stem rolling on the structure of cut rolled stems was analyzed. The results showed that: 1) The coefficient of variation and relative error of the compression-set-characterization method were 3.43 % and 0.77 %, respectively. 2) A high compression-set resulted in an improved stem shaping effect after rolling. Notably, the stem compression-set occurred mainly in the parenchymal tissue layer with large pore size and loose pore structure, while the duct structure was not significantly affected. 3) The compression-set of stems was significantly negatively linearly correlated with the roller clearance, and positively linearly correlated with stem diameter and moisture content. Stem length had no significant effect on stem compression-set. 4) In the rolled stem cutting process, a higher value of stem compression-set resulted in a smaller width, a lower integral stem rate, and a higher broken stem rate in the cut rolled stem. While focusing on optimizing the filamentous effect of the stems, attention should also be paid to the lower cut stem structure and the higher cost due to the higher breakage rate during the cutting process. During the evaluation of stem shaping effect, the compression-set method has shown its high precision and clear physical principles, and provided a reference for maintaining roller clearance and consistent stem shaping effect.