Knit products are widely used in our daily lives because of their excellent elasticity and flexibility. Most of such products are usually composed of flat knitted fabric, which is the basic structure of knitted fabric. This unique structure of it gives knit products high functionality. However, since flat knitted fabric is easily affected by material properties of yarn and knitting machine, and defects that cause the loops of knitted fabric to tilt often occur. Especially, a defect in which the loops of the knitted fabric tilt alternately to the left and right at each step is called Yotari. Since the functionality of knit products are impaired by this defect, the cause of Yotari is needed to be investigated. In this paper, two hypotheses of Yotari are proposed, and the purpose of this paper is to test one of them. For this purpose, firstly, a yarn is modeled because it makes up knitted fabric. Secondly, the knitting process is modeled because influence of knitting process should be considered. Finally, the proposed simulation models are used to analyze the dynamic behavior of yarns knitted in a knitting machine. Then, the results of this simulation are used to test the hypothesis of Yotari.

A five-axis machining center is known for its synchronous control capability. We aimed to maintain the feed speed vector at the end-milling point by controlling two linear axes and a rotary axis with a five-axis machining center to improve the machined surface quality. In previous research, we suggested a method to reduce the shape error of machined workpieces (referred to as the shape error herein) considering the tool approach path determined via calculation. However, a high machining force at the start of the workpiece cutting was observed. In this research, a theoretical method to estimate the machining force is developed by using an instantaneous cutting force model, which considers the synchronized motion of two linear axes and a rotary axis of the 5MC. Subsequently, the most suitable tool approach path is determined considering the prediction of machining force and the machining area in the approach path. Therefore, both a high machining force at the start of the workpiece cutting and shape error reduction can be realized by using the proposed tool approach path.