| dc.description.abstract | To meet the diverse sewing requirements arising from various fabric materials and thicknesses, sewing machines utilize specially designed feed mechanisms to achieve different feeding trajectories for the desired sewing effects. This paper proposes a novel feed mechanism capable of achieving variable feed trajectories through mechanical means. This mechanism can replace the original crank-rocker mechanism with a cam mechanism, without altering the existing machine structure. Therefore different feed trajectories are able to be achieved by changing the cam disc, to meet different sewing needs.
To establish a comprehensive design methodology, the main working components of existing industrial overlock machines are at first analyzed using the modular function deployment method. Components performing the same function are classified into the same module. The feed module and feed adjustment module, responsible for the feeding operation, are further analyzed using the interpretive structural modeling method to understand the impact of each module on the feed trajectory. The feasibility of replacing the crank-rocker mechanism with a cam mechanism featuring an oscillating roller is confirmed.
To calculate the feed trajectory, this study uses the vector loop method to develop a motion position analysis model for each component of the mechanism. When designing the feed trajectory of the new feed mechanism, it is essential to meet the constraints of the original mechanism, including the motion timing relationship between the feed and needle bars, as well as the swinging angle constraints of the feed components. Therefore, Bezier curves are used to define the feed trajectory with the minimum number of data points, ensuring the generated trajectory is continuous, smooth, and curvature-continuous under the given constraints. Considering the space limitations of the existing machine and the manufacturing limits of the cam are also considered in the study. A calculation model for determining the cam mechanism parameters based on the feed trajectory and synthesizing the cam plate profiles is established in the study.
To validate the accuracy of the new feed mechanism design, the corresponding cam profiles for the original trajectory and three specific feed trajectories are designed and calculated in the study. These designs are verified through simulations using the commercial SAM software. Additionally, the impact of feed amount adjustments on the trajectory is discussed. The results demonstrate the feasibility of the proposed design methodology, achieving the intended feed trajectories.
The novel feed mechanism concept and the complete design methodology, from modular analysis and mechanism analysis to feed trajectory design and cam plate synthesis, presented in this paper can be extended to other machines. This can aid in upgrading the functionality of related equipment in the domestic sewing machine industry. | en_US |