Simulation of the hexagonal 3D braiding process for stent preforms

Abstract

Due to the complex braiding process and long development cycle of the hexagonal three-dimensional braided stent, a MatLab based computer-aided braiding method for a stent is proposed to speed up the development process. First, an oblique coordinate system for the chassis and a polar coordinate system for the chassis unit are constructed, respectively, precisely to coordinate the carrier’s movements on the chassis. Subsequently, an iterative formula delineating the trajectory of the carrier is introduced. The formula effectively translates the entire braiding process into the positional coordinates of the carrier on the chassis and the yarn heights on the mandrel during different stages. Based on the specific characteristics of the braiding process and the stent’s structure, the stent is divided into pressing and twisting sections. The interwoven pattern for both the pressing and twisting sections is determined by establishing the basic tiling form, solving the yarn interwoven sequence, judging the interwoven type and computing the number of kinks. Finally, while considering the stent's dimensional parameters and the interwoven pattern of the yarn, the spatial curve equations for the yarns in both the pressing and the twisting sections are formulated. By concatenating these equations for each section, the three-dimensional trajectory equations and a comprehensive solid model of the stent are successfully derived. Through a rigorous comparative analysis of dimensions and the braiding pattern between the three-dimensional solid model and the physical stent preform, the accuracy and fidelity of the model generated through the implementation of computer-aided braiding technology are verified.