NC Machine Tool Feedrate Smoothing for Uniform Surface Finish
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Solution Overview
Problem
Existing numerically controlled machine tools face challenges in producing uniform surface finishes, particularly in areas with high tool wrap through the contour, leading to undesirable vibrations and suboptimal machining results due to constant feedrate and spindle speed settings.
Innovation Solution
A method that transforms suddenly changing feed values in the parts program into continuous desired speed profiles, allowing for uniform and efficient machining by approximating these values using polynomial or spline functions, taking into account the geometry and dynamics of the machine tool, to ensure smooth and accurate movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If constant feedrate and spindle speed settings are used, then the machine tool operation is simple, but undesirable vibrations occur and machining quality is suboptimal
Solution Approach 1:
The patent applies dynamics by transitioning from constant feedrate and spindle speed to continuously variable settings. The numerical controller dynamically adjusts feedrate and spindle speed based on real-time machining conditions, tool position, and workpiece geometry, enabling optimal surface finish while avoiding vibrations through adaptive control rather than fixed parameters
Solution Approach 2:
The patent implements parameter changes by continuously varying feedrate and spindle speed parameters during machining operations. The system modifies these parameters based on machining stage, tool engagement depth, and workpiece material properties, transforming the machining process from static parameter control to dynamic parameter optimization to achieve superior surface quality
2Manufacturing precision
If feed values change suddenly in the parts program, then the programming is simple, but the machining quality becomes non-uniform
Solution Approach 1:
The patent applies preliminary action by pre-calculating and smoothing feedrate transitions before machining begins. The numerical controller processes the parts program to identify sudden feed changes and automatically generates continuous, smooth transition profiles, preventing machining quality variations before they occur rather than reacting to them during execution
Solution Approach 2:
The patent uses an intermediary approach by introducing a feedrate smoothing function between the parts program and the actual machining execution. This intermediary layer processes discrete feed commands and transforms them into continuous, gradually varying feedrate profiles, ensuring uniform machining quality while maintaining programming simplicity
3Productivity
If the tool moves quickly through high wrap areas, then productivity increases, but vibrations increase and machining quality deteriorates
Solution Approach 1:
The patent applies local quality by implementing spatially varying feedrate and spindle speed control. The system identifies specific high-wrap areas on the workpiece and applies localized speed reductions only in those regions, while maintaining higher speeds in low-wrap areas. This enables productivity optimization by preserving high speeds where possible while eliminating vibrations only where necessary
Data Source
AI summary
A numerically controlled machine tool has at least one movement axis and is connected to a numerical controller which includes a parts program. Movements of each movement axis are limited by maximum permissible axis dynamics. The parts program has a sequence of instructions for machining a workpiece which specify different maximum desired speeds for the machining of the workpiece which change abruptly over time. The numerical controller approximates the different maximum desired speeds which change abruptly over time with a desired speed profile that is continuous over time and has a profile of the maximum desired speeds which is also continuous over time. The numerical controller uses the continuous desired speed profile to calculate the desired values of an actual movement profile of the movements for each movement axis.