The 15.01.003 disc spring is mounted on threaded nut 0801401 of the collet opening and closing assembly on Gildemeister-DMG Mori AS20, GS20 and GM20AC multi-spindle automatic lathes. Its main function is to keep the closing pressure of the main spindle bar collet constant, even when slight dimensional variations occur along the total length of the bar being machined. During the machine cycle the spring is axially loaded by the movement of sleeve 3160202 on GS20 and GM20AC machines, or by sleeve 0801301 on AS20 machines, during the collet closing phase. This elastic load stabilizes the clamping force, absorbs small position differences and ensures a regular response of the closing system, reducing the risk of dimensional variations on turned parts. In addition to maintaining the load, the disc spring also contributes to the opening phase of the bar collet by supporting the elastic return of the unit and the correct alternation between material clamping and release. From a kinematic point of view, the component operates in the axial chain formed by threaded nut 0801401, the actuating sleeve, the bar drawtube, the main spindle collet and the elements connected to the opening and closing command. If the spring loses elasticity or breaks due to fatigue, the closing force may become irregular and cause bar micro movements, loss of accuracy, cutting instability, diameter variation, scrap, part sorting and damage to tools, the bar collet or the bar drawtube. For this reason the disc spring must be considered a wear component to be checked periodically during preventive and extraordinary maintenance. Replacement is recommended when breakage, deformation, loss of elasticity, inconsistent collet closing or reduced accuracy on machined parts is detected. Keeping a minimum spare stock is advisable and, when replacement is required because of wear, it is recommended to evaluate replacement on the other spindles as well in order to maintain uniform clamping behavior across the machine. Replacement of a single component is mainly appropriate in the event of collision or localized damage.