Kinematical Smoothing of Rotary Axis near Singularity Point

Abstract

This paper deals with singular configurations of a 5-axis machine tool in high speed milling which may lead to the appearance of large incoherent movements of rotary axes near singularity points. These movements generate slowdowns of the actual feedrate during the execution of the tool path, which affect quality and productivity. Thus, this paper proposes a method to detect these behaviors during machining simulation and correct the tool path. Unlike the literature methods, this correction consists in modifying the tool axis orientation by going through the singularity point while respecting maximum velocity, acceleration and jerk of the rotary axis. For that purpose, the initial articular positions of the rotary axis near the singularity point are fitted with B-spline curves, modified and finally discretized for linear interpolation. Experimental investigations on a test part are carried out to show the efficiency of the method.

A tool path patching strategy around singular point in 5-axis ball-end milling

“…Due to the relationship between kinematical constraints (velocity, acceleration and jerk) and geometrical derivatives (first, second and third derivatives) (Equation 7), the more slender the patch curve the higher the feedrate. Thus it is not mandatory to pass through the singularity as considered before (Grandguillaume et al 2015). Figure 4(b) shows two different patch curves, one passing through the singularity and the other not.…”

“…Thus, this paper proposes a strategy to treat incoherent movements of rotary axes near singular point in terms of geometrical and kinematical behavior. In this proposal, the tool path is not constrained to pass through the singular point as in earlier work on the subject (Grandguillaume et al 2015) but has sufficient degrees of freedom to create the smoothest tool path to follow by the machine tool respecting kinematical constraints such as velocity, acceleration and jerk constraints.…”