NC Machine Tool Feed Profile Smoothing for Complex Contours
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Solution Overview
Problem
Modern machine tools face challenges in maintaining uniform feed rates and spindle speeds, especially in areas with high tool wrap and contour complexity, leading to vibrations and suboptimal surface quality, despite advancements in CAM algorithms that require frequent changes in feed specifications and increased complexity in NC part programs.
Innovation Solution
A method that converts abruptly changing feed values in NC part programs into continuous target speed profiles, considering maximum permissible axis dynamics, to ensure uniform relative movements between the tool and workpiece, allowing for flexible and efficient machining of complex surfaces on non-specialized machine tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If feed values are frequently changed in NC part programs to adapt to complex contours and high tool wrap areas, then machining accuracy and surface quality can be improved in critical areas, but feed rate uniformity deteriorates and vibrations occur
Solution Approach 1:
The patent applies dynamics by transitioning from static, block-based feed rate specifications to a dynamic, continuous feed rate profile. The numerical control system continuously adjusts the feed rate along the tool path based on real-time calculation of tool wrap angles and contour characteristics, rather than using discrete step changes between NC blocks. This dynamic adaptation allows the feed rate to smoothly vary according to machining conditions, maintaining both accuracy in critical areas and uniformity overall.
Solution Approach 2:
The patent implements parameter changes by modifying the feed rate parameter continuously along the tool path based on calculated tool wrap angles and contour curvature. Instead of changing feed rate values abruptly between NC blocks, the system calculates optimal feed rate values at multiple points along the tool path and interpolates between them, creating a continuous parameter variation that adapts to local machining conditions while maintaining overall uniformity.
2Manufacturing precision
If CAM algorithms generate detailed tool paths with frequent feed rate changes for complex surfaces, then machining quality in critical areas improves, but NC part program complexity increases
Solution Approach 1:
The patent applies self-service by enabling the numerical control system to automatically calculate and adjust feed rates based on tool wrap angle and contour curvature information already present in the tool path data. The system uses its own computational resources to analyze the geometry and dynamically determine optimal feed rates, eliminating the need for complex pre-programmed feed rate specifications and reducing NC part program complexity while maintaining high surface quality.
Solution Approach 2:
The patent implements preliminary action by pre-calculating tool wrap angles and contour characteristics along the entire tool path before generating the feed rate profile. This preliminary analysis of the tool path geometry allows the system to prepare optimal feed rate values in advance, which are then smoothly interpolated during execution, reducing the complexity of real-time control decisions and simplifying the NC part program structure.
3Manufacturing precision
If feed rate is reduced in areas with high tool wrap and contour complexity, then vibrations are reduced and surface quality improves, but overall productivity decreases
Solution Approach 1:
The patent applies local quality by implementing spatially varying feed rate specifications along the tool path. The system calculates local tool wrap angles and contour curvature at different positions and assigns appropriate feed rate values to each location, allowing high feed rates in areas with low tool wrap and low feed rates only where necessary for complex contours. This localized adaptation maintains surface quality in critical areas while preserving productivity in less demanding areas.
Solution Approach 2:
The patent uses dynamics to create a continuously varying feed rate profile that adapts to local machining conditions along the tool path. Rather than maintaining a uniformly reduced feed rate throughout the entire machining operation, the system dynamically adjusts the feed rate based on real-time calculation of tool wrap angles and contour characteristics, allowing the tool to move quickly through simple areas and slow down only where necessary for complex geometries, thereby maintaining both surface quality and productivity.
Data Source
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AI summary
A numerically controlled machine tool (4) has at least one movement axis (16) and is connected to a numerical controller (2). Movements of each movement axis (16) are limited by maximum permissible axis dynamics. A parts program (34) is present in the numerical controller (2). The parts program (34) comprises a sequence of instructions for machining a workpiece (62), wherein the sequence of instructions comprises the specification of different maximum desired speeds for the machining of the workpiece (62) which change suddenly over time. The numerical controller (2) approximates the different maximum desired speeds which change suddenly over time by means of a desired speed profile (50) which is constant over time and has a profile of the maximum desired speeds which is constant over time. The numerical controller uses the constant desired speed profile (5) to calculate the desired values of an actual movement profile of the movements for each movement axis (16).