Search Results (4)

China’s small arched shed-building machinery suffers from a low degree of mechanization, building efficiency, and qualification rate for frame insertion. Therefore, we designed a rotary double-insertion device and established the equation for its motion trajectory. The analysis shows that in the rotary insertion process, a better point of entry into the soil exists. A simulation model was constructed in ADAMS, and the static and dynamic trajectories were analyzed. Additionally, the optimal planting and insertion speed ratios were determined. Considering the qualified rate of the insertion frame as the evaluation index to establish a regression model, we adopted a three-factor three-level experimental design and established the planting speed ratio, center distance of the planting arm, and length of the pressing rod arm as the main influencing factors. We used Design-Expert 13 to perform the analysis of variance and determined the optimal parameter combinations. The experimental results show that the planting speed ratio was 0.7, the center distance of the planting arm group was 554 mm, the length of the pressing rod arm was 923 mm, and the qualification rate of trellis planting at this time was 98.05%. The bench was adjusted and tested based on the optimal parameter combination. The average value of the measured trellis qualification rate was 96.73%, and the relative error between the test value and the theoretical optimization value was 1.32%, thereby verifying the reliability of the optimal parameter combination. Field verification test results show that the rotary double-insertion device had a planting speed ratio of 0.7 and a trellis qualified rate of 95.74% compared with the theoretical optimization value of 2.31%. Conforming to the design requirements of small arch shed-building machinery, the prototype operation performance was stable. Full article

Weeds in paddy fields can seriously reduce rice yield. An intra-row weeding device with double-layer elastic rods was designed, considering the differences in mechanical properties between rice and weeds, which can press weeds into the soil and avoid damaging rice. The elastic force of the elastic rods can be adjusted by changing the position of the regulating mechanism to adapt to different weeding conditions. A measurement experiment was conducted to determine the variation rule of elastic force. The quadratic orthogonal rotation combination discrete element simulation experiment, which used weeding depth and weeding speed as experimental factors, and the amount of soil disturbance and the force of the inner and outer elastic rod in the horizontal and vertical directions as experimental indicators, was conducted to study the interaction between the weeding device and the soil. The optimal weeding parameters were obtained: the weeding depth was 15 mm, the weeding speed was 0.9 m/s. The field experiment, which used the various parameters of the weeding device as experimental factors and the weeding rate and damaging seedling rate as experimental indicators, was conducted to determine the weeding effect. The experimental results showed that the optimal position of the regulating mechanism was 270 mm, with a weeding rate of 80.65% and a damaging seedling rate of 3.36%. The weeding rate can be increased by at least 11.18% by adjusting the regulating mechanism to a suitable position under the same weeding conditions. This study can provide a reference for research on weeding machinery for organic rice. Full article

In crank presses, an important role is played by the presence of actuators with dwell, in which, with continuous movement of the input links, the output working link remains stationary at some part of the work. The use of a high-class structural group (fourth class) expands the functionality of the crank press, including it can ensure the link dwell of the working link on a given section of movement during the required period of time. As a result of the conducted numerical research, four variants of actuators of the crank knee press were designed. Due to the rational choice of the positions of racks and crosshead guide, the best layout of the dimensions of the press mechanism has been achieved. Changing the coordinates of the racks accordingly allows for designing a mechanism with upper or lower dwells of the working links. The duration of the dwell of the working link (slider) can be adjusted by selecting the distance between the racks with rotational pairs and a crosshead guide of the mechanism. All this is shown on the basis of a numerical experiment based on kinematic analysis. In addition, the proposed structure of the mechanism makes it possible to ensure the exact link dwell, which cannot be achieved due to the well-known knee presses based on the second-class mechanism. Full article

Many studies concerning the precision manufacturing of freeform concrete panels have been conducted, however, this process remains labor intensive taking significant amounts of time and cost. In particular, the precision in the shape of the panels produced tends to be low because of the manual work involved in producing the curves of those panels. This study documents the development of mold production technologies that can be used to produce precise curved surfaces on the upper and lower parts of a mold for freeform concrete panels. A double-sided multipoint press CNC (computer numerical control) produces curved upper and lower surfaces of a mold without the need for manual work, while the operational technology we developed to control this tool enhances the precision of the curves created. The precision of these technologies was verified through experiments. The difference between the shapes designed and those produced were found using 3D scans and quality inspections. Unpredictable errors can occur due to the size of certain curvatures, the elasticity of the silicone plate, and the rotational angle of the joints of the rods supporting the surfaces. To minimize errors, shape compensation was carried out through reverse engineering, leading to a maximum error of 2.887 mm, which is within the allowable error. The results achieved in this study are a significant step toward technologies that will produce increasingly precise freeform concrete panels. Full article