Dynamic analysis of disc spring effects on the contact pressure of the collet—spindle interface in a high-speed spindle system

Abstract

In a high-speed gas spindle, the drawbar force required to hold the drill bit is produced by the deformation of disc spring stacks. This drawbar force, applied to the collet-spindle interface, generates a contact pressure on the collet to hold the drill bit in position. Thus, the behaviour of the collet-spindle interface is critical to machining quality. Accordingly, this study investigated how disc spring characteristics affect the collet-spindle interface in a high-speed spindle. Typically, the drawbar force will decrease following the deformation of disc springs resulting from the effects of centrifugal force at high rotational speeds. This effect must be considered, especially in high-speed spindle applications. This study first measured the drawbar force experimentally and compared these results with theoretical and finite-element analysis (FEA) data under static conditions (i.e. no rotation). Having obtained satisfactory agreement among these data, the FEA was extended to a further investigation. Properties of the collet-spindle contact interface were analysed, given changes in rotational speed from 0 to 300 000 r/min under various disc spring deflections, various friction coefficients between the disc springs and their support, and distinct taper angles at the collet-spindle interface. All of these conditions are discussed here. These essential parameters are believed to cover much of the design of high-speed gas spindle systems.

A load–displacement prediction for a bended slotted disc using the energy method

“…Previous research 5,8,9 has not established any numerical equations that can approximately satisfy the finite element analyses.…”

“…These trends are similar to the results obtained in the previous research. 5,8,9 One possible explanation is that the radial deflection was allowed in the 3D finite element analyses. However, such deflection was ignored in the 2D computations.…”

“…[1][2][3][4] Load-displacement formula for a coned disc spring or a non-slotted disc spring was first developed by Almen and Laszlo. 1,5 Based on the theory of Almen, the dimensions used to define the geometries refer to the middle line of the disc spring cross-section. The same dimensions were also used by Schremmer 6 as an attempt to propose a new formula for a limited straight slotted disc spring.…”

Effect of the screw–nut joint stiffness on the position-dependent dynamics of a vertical ball screw feed system without counterweight

“…The machining stability of a machine tool is not only affected by the dynamic characteristics of the spindle system but also by the dynamic characteristics of the ball screw feed drive. Most scholars focus on studying the dynamic characteristics of spindle system, 4–7 while only a few pay attention to the dynamics of the ball screw feed drive. However, with the increasingly enhanced requirements for the cutting performance of machine tools, the influence of the dynamic behavior of the full machine tool mechanical structure on the machining stability has become of major importance, 8,9 especially the ball screw feed drive.…”

Dynamics prediction of spindle system using joint models of spindle tool holder and bearings

“…20 Shamine and Shin 21 reported that 25–50% of the deformation of the spindle tip is related to the spindle tool holder joint interface, and the characteristics of the joint relate to the interface features, such as the material properties, machining roughness, lubrication and clamping force. 22 Many obstacles exist for the analysis of tool holder joints, such as the complex stress state at the interface and the changeable joint stiffness. 23,24 Generally, the tool holder is drawn by the clamping bar and the clamping force is generated by spring stacks.…”