Abstract:

Objective To transcend the prevalent knitting techniques for shoe uppers in the current market, a four-needle-bed computerized flat knitting machine is employed in this study for fabric construction. The objective is achieve the 3-D shoe uppers in one operation to eliminate the needs for stitching. This method is anticipated to diminish raw material wastage and streamline the shoemaking process.

Method The design of traditional knitted shoe uppers was delved into in this study through optimizing and designing a new type of knitted shoe structure layout. A four-needle-bed computerized flat knitting machine was utilized, opting to knit the left and right sides of the shoe on the front and back needle beds, respectively. Concurrently, each side is used to knit the exterior and interior structures of the shoe. Distinct stitch structures tailored to the various functional zones of the shoe uppers were incorporated into the design, utilizing four types of yarns, which are polyester multifilament, polyester monofilament, polyester covered spandex yarn, and hot melt yarn. Subsequently, the shoe uppers were placed over a shoe mold of the corresponding sizes and subjected to a heat setting process to set the shoe upper, culminating in the final product.

Results Upon removal from the knitting machine, a comprehensive structure was revealed by the shoe upper, incorporating integrated tongue and sole components without the need for subsequent stitching between the heel and sole, or the lateral sides, thus achieving a seamless, one-piece construction. Increased density and weight were typically exhibited by traditional 2-D flat knitted shoe uppers following a flat heat shrinkage process during shaping. Initially, the fabric dimensions directly off the machine were slightly larger than those of the final shoe upper, necessitating design considerations for the end product's dimensions. Contrastingly, an analysis involving zone sampling across various sections of the new shoe upper, both pre- and post-shaping, was conducted. Measurements of stitch density changes revealed a post-shaping decrease in stitch density and an enlargement of the shoe upper's overall dimensions. Consequently, a size deficit is initially presented by the new shoe upon machine removal. However, following stretching and shaping, the interstitial spaces within the overall stitch expanded, resulting in a lighter construct compared to traditional uppers. A lighter weight was achieved by this innovative approach, ensuring the inclusion of integral sole and tongue components. Furthermore, due to the large surface area of the sole structure, it was not only convenient but also robust when stitching or bonding with rubber soles. In the context of this investigation, the terminal physical representation of the shoe's structure was examined, accompanied by pertinent measurements and analytical data. It was elucidated that the fabric constituting the shoe's sole undergoes extension to conform to the dimensions prescribed by the shoe last mold. This observation result is very important for understanding the adaptability and performance of the shoe body under different forces in the last mold. Therefore, it was found that the tensile force of the shoe body at the head of the shoe last is the largest, which requires a specific structure to withstand.

Conclusion Diverse yarns are employed in this study, implementing a segmented structural approach. A four-needle-bed computerized flat knitting machine is utilized to design and craft a 3-D shoe upper through a one-step knitting forming process that enhances material conservation. Cutting requirements are markedly diminished by this technique, and 3-D integrated forming is facilitated, incorporating the tongue, sole stitch, and a seamless heel. The result is a shoe upper with superior breathability, fit, and reduced weight, offering an innovative perspective on the fabrication of knitted footwear.

Key words: horizontal knitting, fully shaped shoe body, structural design, partitioned process, solid forming