Comparing approaches for multi-axis kinematic positioning in machine tools

Abstract

Maintaining minimal levels of geometric error in the finished workpiece is of increasing importance in the modern production environment; there is considerable research on the identification, verification and calibration of machine tool kinematic error, and the development of Postprocessor implementations to generate NC-code optimised for machining accuracy. The choice of multi-axis positioning function at the controller, however, is an often-overlooked potential source of kinematic error which can be responsible for costly mistakes in the production environment. This paper presents an investigation into how mis-management of the positional error parameters that define the rotary-axes’ pivot point can lead to unintended variations in multi-axis positioning. Four approaches for kinematic positioning on a Fanuc-based controller are considered, which reference two separate parameter locations to define the pivot point – managing the kinematics within the Postprocessor itself, full five-axis positioning with a fixture offset, full five-axis with rotation tool centre point control and 3+2-axis with a tilted workplane. Error vectors across four sets of rotary-axis indexations are simulated based on the theoretical kinematic model, to highlight the expected differences in geometric error attributable to mismatched pivot point parameters. Finally, the simulation results are verified experimentally, demonstrating the importance of maintaining a consistent approach in both programming and operation environments.

A framework for practically effective creation of postprocessors for 5-axis CNC machines with all possible configurations and working mechanisms

“…The methods proposed in this study for practically effective creation of postprocessors for 5-axis CNC machines were also successfully applied to determine the inverse kinematic equations for the 5-axis CNC machines that include the 5-axis CNC machines with the non-orthogonal rotary axes 3–8 and the 5-axis CNC machines with the orthogonal rotary axes. 9–15 The proposed methods were also verified with the 5-axis CNC machines with the TTTRR configurations, 3,5,6 and the 5-axis CNC machines with the RTTTR configurations. 6,15,20 It is noted that the inverse kinematic equations which are obtained by using the proposed method in this study and the inverse kinematic equations which were documented in Refs 3–15,20 are the same.…”

“…There has been a number of studies that focused on the kinematic modeling and the creation of postprocessors for the 5-axis CNC machines. 3–25 The kinematic modeling and the postprocessor creation for specific 5-axis CNC machines with the non-orthogonal rotary axes were investigated. 3–8 The methods for creating CNC postprocessors for the individual 5-axis CNC machines with the orthogonal rotary axes were proposed by Refs.…”

“…3–8 The methods for creating CNC postprocessors for the individual 5-axis CNC machines with the orthogonal rotary axes were proposed by Refs. 9–15 My 4 developed the postprocessor for the 5-axis CNC machine DMU 70e to transform the CL data in the form of the ISO format into the CNC machining programs, the G-codes files. Son et al 5 introduced the postprocessor for the 5-axis CNC machine in which the head is inclined at about 45°, and the rotation and tilting angles are calculated based on inverse kinematics and mapping the part coordinate system with the machine coordinate system.…”

“…My et al 25 proposed a general approach for the kinematic modeling of the two rotary axes of the 5-axis CNC machines. Although there have been investigations, as shown in the above-mentioned attempts, 3–25 that aims to obtain solutions for a generalized kinematic modeling of 5-axis CNC machines, a little attention has been paid to formulation of the kinematic model in a simplified and explicit manner that make it possible to create CNC postprocessors intuitively, without the required strong backgrounds and skills for engineers or CNC operators in mathematical modeling and kinematics of machines, especially mathematical modeling of multibody systems, with the advanced knowledges of kinematic modeling and complex mathematic transformations.…”

Design and application of a biconjugate closed-end cylindrical single-cam pair

“…The cam was manufactured in a DMU80T produced by DMG company. 22,23 After establishing the equation of cam surface, VB language is used for CNC programing of tool track. The cutter with the same shape as the roller is used to process the cam.…”