Design and experiment of shrimp backside cutting machine formed by belt clamping and conveying

Abstract: Shrimp backside cutting is an important pretreatment process of shrimp's mechanized peeling, which directly affects the realization of mechanical shelling. Aiming at the current situation of immature development of shrimp cutting and the shortage of backside cutting device in China，it is urgent to develop the shrimp cutting machine which is suitable for Penaeus vannamei and adapted to each level shrimp with different shape parameters. Furthermore, to develop a practical and reliable shrimp cutting equipment is of great significance to promote shrimp's mechanized processing. In this paper, a shrimp backside cutting machine formed by belt clamping and conveying has been designed and manufactured. This machine consisted of four main sections: the clamping and conveying mechanism, the adjusting mechanism of clamping angle-V, the fine-tuning mechanism of blade height, and the depth limiting and guiding parts. The basic requirement for clamping and conveying mechanism was to achieve continuous and stable gripping of the shrimp and to ensure the correct posture when getting on the shrimp's backside cutting and reduce the clamped body damage of shrimp. The clamping and conveying mechanism consisted of two sets of independent belt conveyor mechanism. The inner side of the belt was arranged in rows of tensioning wheels which led the conveyor belt, and the entire conveyor belt was driven by a stepper motor with a timing pulley with transmission ratio. The clamping angle V adjustment motion was accomplished by the angle adjustment and the gap compensation. The angle adjustment electric push rod drives the slider to slide up and down soon afterwards the bending rocker arm begins rotating, and the action produced torque to drive the belt base turn a certain angle, and then to achieve the adjustment action of the clamping V angle which formed by the two symmetrical belt. The gap compensation electric push rod drove the base pin to move left and right and then adjust the gap between the two symmetrical belts drive mechanism, and these actions ensured the space in the bottom of the V-shaped clamping unchanged ultimately. The depth limiting plate and the inverted U-shaped plate were mounted on the motor shield. The disc knife passed through the slot of the depth limiting plate to control the depth of the incision by adjusting the height of the blade leaking. Inverted U-shaped plate with different closed mouth on the two sides which was arranged at a certain angle on the above of the V-shaped clamping space, and the plate forms an inverted U-shaped and wedge-shaped space that converged along the movement of the shrimp. The depth limiting and guiding parts can straighten and guide the shrimp body and effectively ensure the depth and incision symmetry. Through the single factor test, it was illustrated that how the three key parameters that the clamping V Angle, conveying speed and cutting speed, to influence four evaluation indicators which were incision length, incision symmetry, incision depth and incision smoothing on the shrimp backside cutting machine. Furthermore the three key parameters have been optimized. An orthogonal test of three factors and three levels which had been arranged by Box-Behnken Design, the regression mathematical models of four evaluation indicators with three key parameters had been found. The variance analysis of the test results was carried out by using Design-Expert8.06 software. The satisfactory process parameters of the shrimp backside cutting machine had been obtained through the optimization analysis. The optimal combination of the process parameters were as follows: conveying angel of 33°, conveying speed of 285mm/s, cutting speed of 1 250 r/min. From the results of predicting model, success rate of incision length was 92.46%, success rate of incision symmetry was 95%, success rate of incision depth was 91.83%, success rate of incision smoothing was 93.54%; The related verification experiment under the best combination of the process parameters was carried out, and the experimental results showed that the success rate of incision length was 92.5%, success rate of incision symmetry was 90.83%, success rate of incision depth was 90.0%, success rate of incision smoothing was 93.33%. By comparing the predicted results with experimental results, we concluded that the shrimp backside cutting machine can work reliably and stably under condition of the best parameter combination, and moreover all indicators can meet the requirements.