Parameter optimization design and experiment of famous tea continuous carding machine

A tea carding machine is one of the key equipment in the shaping process of needle-shaped green tea. However, the key parameters are the empirical values in the traditional tea carding equipment, leading to the low carding quality. This study aims to optimize the structural and operation parameters of a continuous tea carding machine using numerical simulation and analogy methods, in order to improve the performance. The kinematics analysis was implemented to express the velocity and acceleration of the pot trough. The motion and force of the pot trough were then determined to explore the relationship between the pot trough movement and the tea carding state. The dynamic model of the tea-U-shaped groove was then established at each stage of the collision motion of tea hitting the convex edge, the rubbing movement of tea at the bottom of the U-shaped groove, the collision motion of tea and the right plate of the U-shaped groove, as well as the collision motion between tea and the left arc inner wall of U-shaped groove. The force characteristics of tea were analyzed to evaluate the tea striping in each stage of the pot trough motion cycle. A single-factor test was carried out to simulate the tea carding using EDEM software. The key parameters were simulated, such as crank rotational speed, pot trough amplitude, pot trough inclination angle, number of convex ridges, and height of convex ridges. The relationship curves were obtained among the average speed, average force, and tea carding time of tea particles. After that, a three-factor and three-level quadratic rotation orthogonal test was designed, where the strip rate and broken tea rate were taken as the evaluation index. The data processing and regression analysis were carried out using Design-Expert software. The experiments were then performed to verify the optimal model. The simulation results show that the crank rotational speed, pot trough amplitude, and the number of convex ridges shared a great influence on the quality of tea carding, where the tea particles were gradually transited from the disordered state at the beginning of carding to the longitudinal ordered state. The longitudinal proportion of tea leaves increased with the increase of time, in order to promote the formation of strip shape in the axis direction of the main stem vein of tea leaves. The orthogonal test results were processed by data processing and regression analysis. The optimal combination of parameters was obtained with the crank rotational speed of 195 r/min, pot trough amplitude of 99 mm, and number of convex edges of 2. The strip rate was 87.39%, whereas, the broken tea rate was 1.85%. The relative error with the optimization was within 5%, indicating the reliability and accuracy after optimization. The findings can also provide a theoretical reference to optimize the continuous carding machine.