Loads on yarns change approximately 3,000 times from the warp beam to the finished fabric during weaving. Sulzer Innotec's WebSim software evaluates machine dynamics and calculates warp and tensile forces on Sulzer Textil's G6200 rapier loom and M8300 multiphase loom. The program simulates yarn behavior, deflecting elements, control influences, fabric movement through fabric takeup, and friction forces on rotating deflectors. It includes numerical models for the dynamics of all machine components that contact the warp yarn ends of fabric. Sulzer Textil will use the program to evaluate loom problems for customers, improve the design of machine components, and reduce the need for testing to establish parameter settings for fabrics and yarns.