Abstract:

Objective In view of the problems existing in the current three-dimensional braiding virtual simulation technology, such as the asynchrony between reverse modeling and the actual manufacturing process, the difficulty of conventional yarn models adapting to multi-layer and multi-yarn braiding, and the disconnection between algorithms and electromechanical systems, a yarn finite element processing method based on the dual states of winding and unwinding is proposed to achieve real-time synchronization of the braiding process and the simulation model, and then a mechatronic simulation system suitable for hexagonal and rotary braiding machines is developed, so as to enhance the universality and practicability of virtual braiding software in engineering applications.

Method The principles of hexagonal and rotary braiding were analyzed. Based on the commonalities of these two braiding methods, a mathematical model of the braiding machine base was established using the Cartesian coordinate system. The motion matrix of the yarn carrier on the base was derived, thereby obtaining the motion data of the yarn. Then, the braiding process was transformed into the position change information of the yarn carriers, and a pressing matrix was constructed to provide a basis for the interlacing judgment of the yarn on the mandrel. Based on the above analysis, the shape of the yarn was accurately expressed using NURBS curves. A yarn finite element processing method based on winding and unwinding states was proposed for the generation of yarn on the mandrel, enabling the three-dimensional dynamic generation of yarn. Taking a real braiding machine composed of 32 angle wheels and 32 dials as the development object, a virtual three-dimensional braiding software suitable for both braiding processes was developed using the Qt Toolkit. Finally, the three-dimensional theoretical models of 10 sets of braided materials produced by the prototype machine were compared with the actual products using industrial Computed Tomography equipment.

Results The yarn generated using NURBS curves can change the local curvature of the yarn with a small number of control points, meeting the multi-layered development requirements of the fabric. The proposed winding and unwinding yarn finite element generation methods can simply and quickly achieve the three-dimensional dynamic generation of yarn. The comparison of 10 sets of three-dimensional theoretical models of braided materials with the actual products showed a high degree of consistency in yarn pressing, with an average error of only 3%-6% in diameter and length.

Conclusion The accuracy of the software algorithm was verified through practical examples, achieving the application of one machine in hexagonal and rotary braiding. The software can also be integrated with other conventional industrial software for secondary development, enabling it to be endowed with material properties and pre-assessment performance, thereby realizing the integrated electromechanical simulation design of three-dimensional braiding.

Key words: three-dimensional braiding, rotary braiding, hexagonal braiding, yarn expression, virtual simulation