OPTIMIZATION OF HOT FORMING PARAMETERS FOR SHOE BLANKS ON A LAST

Abstract

The paper investigates the features of modern footwear manufacturing under conditions of rapid adaptation to market requirements, the increasing role of advanced materials and technologies, and the necessity of designing components and assemblies joined on complex three-dimensional surfaces. Particular importance is attributed to the process of hot forming of the footwear blank bottom on the last, as it determines the geometric accuracy of the internal shape of the product and its operational performance characteristics. Despite the development of digital modeling and CAD technologies, the problem of local gaps between the last bottom surface and the press mold remains relevant, leading to an uneven distribution of specific pressure, reduced shape stability, and decreased durability of footwear products. The study proposes a scientifically substantiated approach to basing the longitudinal-axial profiles of lasts and press molds within a series of adjacent sizes, relying on stable support zones (heel region, longitudinal arch, and metatarsophalangeal flexion area). A methodology for forming the longitudinal–axial profile of the press mold is developed, taking into account technological allowances, viscoelastic-plastic material properties, and thermal deformations of the footwear blank. Within the scope of the research, geometric gaps between lasts and press molds in the XZ plane were analyzed. It was established that the proposed basing principle according to stable support zones reduces maximum gaps by 20-30 % compared to traditional linear scaling of profiles and localizes them within intersupport segments, ensuring a more uniform distribution of specific pressure during the hot forming process. The use of CAD-based analysis enables the prediction of geometric mismatches, optimization of press mold geometry, and adjustment of technological process parameters for serial footwear production. The practical significance of the study lies in improving the stability of the hot forming process, reducing the volume of corrective operations, decreasing defect rates, and increasing the repeatability of results in serial footwear manufacturing. The proposed approach is compatible with modern CAD/CAM systems and can be integrated into automated production lines without significant equipment modifications, confirming its technological and economic feasibility