Саlculation of Cutting Tool Parameters for Production of Split Fluoroplastic Rings

The paper considers the technological process of manufacturing fluoroplastic sealing rings, consisting in forced feeding and pulling a polymer tape blank between rotating rollers, plastic bending of the tape in the deformation zone toa given curvature by twisting it on a drive roller and the subsequent operation of cutting off the strip after obtaining a ring of the required diameter. This technology has high productivity due to the automation of the full cycle of manufacturing a split ring and the continuity of the process allowing to minimize waste, reduce the labor intensity and energy intensity of production. The most difficult issue in developing the proposed technology is the design of the working tool, its dimensions and geometry, as well as the power and kinematic parameters of the device that ensure the production of fluoroplastic rings of the required accuracy. The complexity of the issue lies in the fact that fluoroplastic has a number of features that manifest themselves during deformation, and its mechanical behavior under force exposure differs significantly from the behavior of known classical materials. However, unlike other polymers, fluoroplastic is a high-density material and has a structure with a high degree of crystallinity, therefore, as studies show, its behavior under load, as well as the mechanism and sequence of deformations in it, are in many ways similar to the behavior of metals, which allows to use methods and approaches adopted in the mechanics of solid deformable bodies for fluoroplastic. According to the proposed technology, a fluoroplastic tape blank, pulled between rotating rollers and subjected to bending in the deformation zone, experiences pure bending with the occurrence of elastic and residual deformations, of which it is the latter that give the product the necessary shape and ensure the production of a ring of the required diameter. To solve this problem, it is necessary to perform the corresponding force and geometric calculations of the process. Force calculation is aimed at determining the force parameters of bending that create the maximum possible irreversible deformations in the deformed product with the minimum possible elastic recovery (springing) after leaving the deformation zone, and the geometric calculation is aimed at fulfilling force conditions. Based on a study of the stress state during bending of fluoroplastic tape, taking into account the different rigidity of fluoroplastic under tension and compression, as well as the kinematic calculations of the elements of the working unit of the installation, the diameters of the forming roller that creates the necessary bending forces in the deformation zone and the cutting roller-caliber that ensure obtaining a ring of the required diameter are determined. The calculation methods developed by the authors are in fairly accurate agreement with the results of experimental studies.