Pre-removal of short stems on the stem screening and stemming production line with size-controlled spatial screening

[Objective]A pre-removal line for short stems was designed in this study to improve the quality of tobacco stem fiber production. Screening hole design theory was studied, and size-controlled spatial screening technology was utilized to enhance the accuracy of tobacco stem separation and classification. [Methods] Screening holes were designed as feed ports on the surface of the screening plate, with separation holes, curved separation surfaces, and discharge chutes arranged directly below. By controlling the position and dimension x of the discharge chute, the accuracy or efficiency of tobacco stem classification can be improved. Screening holes were arranged according to a sinusoidal pattern, using sinusoidal flow-guiding strips to balance the flow rate of the tobacco stems, or designed along the troughs of a cosine curve, with the crests used to guide the tobacco stems, improving the smoothness of the screening process. [Results] Screening holes with a diameter of 20 mm captured the flowing tobacco stems on the vibrating screen, achieving size-controlled spatial screening. Optimizing the value of x improved the classification accuracy, and the sinusoidal flow-guiding enhanced the separation effect. [Conclusion] The short-stem pre-removal line improves the classification accuracy of tobacco stems and the quality of tobacco stem fiber production. The size-controlled spatial screening theory can be applied in the tobacco industry, such as for the separation of stems from cut tobacco and the screening of reconstituted tobacco sheets. It can also be extended to screening technologies and mechanical engineering research across various industries in China.