Numerical Controller Interpolation for Constant Relative Speed
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Solution Overview
Problem
Existing methods for interpolating between program command points in machining processes, especially in multi-function machines like lathes and machining centers, fail to maintain a constant relative speed between the tool and workpiece when the workpiece is rotated, leading to deviations in the actual tool path and poor surface quality, particularly in laser machining where maintaining constant laser output is crucial.
Innovation Solution
A numerical controller performs provisional interpolation on a non-rotating coordinate system, converts the start and end points to a rotating coordinate system to obtain speed ratios, and adjusts the command speed to maintain constant relative speed between the tool and workpiece through main interpolation on the non-rotating coordinate system, ensuring consistent cutting quality and laser output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If interpolation is performed on the rotating coordinate system according to command speed, then the relative speed between tool and workpiece becomes command speed, but the actual path deviates from the command path
Solution Approach 1:
The patent performs preliminary interpolation calculations on the non-rotating coordinate system before actual machining, converts the start and end points to the rotating coordinate system to obtain speed ratios, and uses these pre-calculated ratios to adjust command speeds. This preliminary action allows the system to maintain both accurate paths and correct relative speeds without real-time computation delays.
2Manufacturing precision
If interpolation is performed directly on the non-rotating coordinate system according to command speed, then the interpolation path matches the command path, but the relative speed between tool and workpiece varies
Solution Approach 1:
The patent calculates the ratio of rotational speed to command speed at the start and end points of the interpolation path, and uses these feedback ratios to continuously adjust the command speed during machining. This feedback mechanism ensures that the relative speed between tool and workpiece remains constant while maintaining accurate path following on the non-rotating coordinate system.
3Productivity
If command path length is increased to improve productivity, then machining efficiency increases, but surface quality deteriorates due to variable relative speed
Solution Approach 1:
The patent dynamically changes the command speed parameter based on the calculated speed ratios at different points along the interpolation path. By adjusting the command speed according to the rotational coordinate system requirements while maintaining the non-rotating coordinate system path accuracy, the system can process longer command paths without sacrificing surface quality or relative speed consistency.
Data Source
AI summary
A numerical controller analyzes a machining program, generates movement command data for moving a main spindle relative to a workpiece, causes an interpolation unit to perform interpolation processing based on the generated movement command data, and generates and outputs interpolation data for each interpolation cycle. Further, the interpolation unit performs provisional interpolation processing according to command speed F on a non-rotating coordinate system, converts a start point and an end point of provisional interpolation to positions on a rotating coordinate system to obtain speed F′ on the rotating coordinate system, obtains a ratio r of the speed F′ to the command speed F, and performs main interpolation processing at speed of F/r.