A two-step feedrate planning of polygonal path for micro laser-cutting machines

Abstract

The sample machined with the polygonal path is a common feature in a micro laser-cutting machine. It brings a difficult problem in feedrate planning when the machining accuracy is limited to the scale of sub-micrometer. In this paper, the transition feedrate at the node point is determined by the dynamic capacity of a machine. Then, the jerk-limited feedrate planning is introduced to adjust the feedrate in a smooth manner. The feedrate profile is transferred into the discrete shape for the sampling mechanism of the interpolator in a CNC controller. Moreover, a two-step feedrate planning is proposed to handle the problem that, there exists a distance error, as the line segment is not divisible by the step calculated by feedrate and sample cycle. Firstly, the control parameters, namely, the command feedrate, acceleration and jerk in different stage of the feedrate profile, are estimated by the jerk-limited feedrate planning. Then, a correction scheme is developed to slightly regulate the control parameters. It aims to compensate the distance error caused by the discretization in the process of interpolation. Meanwhile, the proposed method is discussed in two cases according to the length of the line segment. The method of direct adjustment is applied to handle the situation where a line segment is long enough; otherwise, the method of numerical estimation will take the place. Finally, a simulation analysis is presented to demonstrate the performance of the proposed method in feedrate planning. Then, machining experiments are conducted on the self-developed micro laser-cutting machine to verify the effeteness of proposed method.