Feed Rate Variation Strategy for Semi-Conical Shell Workpiece in Ball Head End Milling Process

Abstract

The semi-conical shell workpiece is a special kind of thin-wall part that is commonly used in aerospace and mold industries. Due to the special stiffness distribution and weak rigidity for the area with a large radius, the machining quality of the semi-conical shell is sensitive to both cutting force and vibration. Conventionally, constant conservative machining parameters are chosen to ensure the workpiece deformation and surface quality, which will reduce the machining efficiency. Based on the cutting force and vibration response simulation of the whole milling process. A feed rate variation strategy is proposed for the ball head end milling process of the semi-conical shell workpiece. The cutting force, dynamic performance and stability prediction are obtained considering the shape and boundary conditions of the workpiece and the contour tool path of the milling process. Variable feed rate is used in the milling simulation to find the harmony between machining quality and efficiency. User-defined vibration amplitude and another user-defined cutting force threshold are used to find the optimal feed rate for each simulation segment. Both continuous and discrete feed rate variation strategies are proposed, and the improved discrete feed rate variation is applied in the milling experiment. About 25% of the consumed time is saved with almost the same machining quality by the experimental results.

Intelligent Feedrate Optimization Using an Uncertainty-Aware Digital Twin Within a Model Predictive Control Framework

“…To directly incorporate dynamic components via physics-based models, numerous feedrate scheduling methods for CNC machines maximize feedrate in each NC block while keeping cutting force under desired levels via mechanistic force models [31]- [38]. Some feedrate scheduling techniques maximize feedrate while regulating machining error due to tool deflection [39]- [45] or force-induced servo error [46], [47] under desired tolerance in CNC machine tools. A few works in feedrate optimization [11], [30] constrain motion-induced error via linear physics-based models of servo dynamics.…”

Construction Method of Digital Twin System for Thin-Walled Workpiece Machining Error Control Based on Analysis of Machine Tool Dynamic Characteristics

“…The strategy takes into account the shape and boundary conditions of the workpiece as well as the contour tool path of the milling process to obtain predictions of cutting forces, dynamic performance, and stability. Experimental results showed that the strategy saved about 25% of time while achieving almost the same machining quality [19]. Olvera considered the helical angle, runout and cutting speed effects to calculate the stability diagram.…”

Intelligent Feedrate Optimization using an Uncertainty-aware Digital Twin within a Model Predictive Control Framework

“…To directly incorporate dynamic components via physics-based models, numerous feedrate scheduling methods for CNC machines maximize feedrate in each NC block while keeping cutting force under desired levels via mechanistic force models [9,10,15,16,27,29,38,42]. Some feedrate scheduling techniques maximize feedrate while regulating machining error due to tool deflection [2,4,18,24,30,37,43] or force-induced servo error [21,41] under desired tolerance in CNC machine tools. A few works in feedrate optimization [12,13] constrain motion-induced error via linear physics-based models of servo dynamics.…”

“…A few works in feedrate optimization [12,13] constrain motion-induced error via linear physics-based models of servo dynamics. However, the works in [2,4,9,10,12,13,15,16,18,21,24,27,29,30,37,38,[41][42][43] are unable to effectively constrain actual cutting force or servo error in situations where uncertainties arise from nonlinear dynamics or disturbances that are not incorporated in the physics-based models. As a result, their capability to maximize feedrate while adhering to dynamic constraints is severely restricted.…”