Numerical Controller Corner Curves Inserting Unit
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Solution Overview
Problem
Existing numerical control systems for machine tools face challenges in maintaining machining accuracy and minimizing shock at corners due to inward rounding errors, which are influenced by velocity changes and require adjustments in allowable velocity differences and time constants for each machine or machining program.
Innovation Solution
A numerical controller that inserts three cubic polynomial curves between blocks to ensure continuous direction and curvature at corners, allowing for the reduction of inward rounding within a preset tolerance, independent of post-interpolation acceleration and deceleration, using equations to determine curve parameters based on corner angles and distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If post-interpolation acceleration and deceleration is performed to suppress shock at corners, then shock is reduced, but inward rounding error increases and machining accuracy deteriorates
Solution Approach 1:
The patent applies preliminary action by performing pre-interpolation acceleration and deceleration before the corner point. The feed rate is decelerated from a position a distance short of the corner so that the feed rate at the corner agrees with the calculated corner velocity, then accelerated on and after arrival at the corner. This preliminary velocity adjustment suppresses shock while controlling inward rounding error.
Solution Approach 2:
The patent uses parameter changes by calculating a specific corner velocity based on the rounding angle and other parameters, then controlling the feed rate to match this calculated velocity at the corner. The allowable velocity difference parameter is adjusted to balance shock suppression and machining accuracy requirements.
2Manufacturing precision
If allowable velocity difference or time constant is adjusted to reduce inward rounding error, then machining accuracy is improved, but system adaptability deteriorates as adjustments are needed for each machine or machining program
Solution Approach 1:
The patent achieves universality by providing a corner velocity calculation method that works for different rounding angles and machine configurations. The system calculates corner velocity based on the specific rounding angle and allowable velocity difference parameters, making it adaptable to various corners without requiring separate adjustment procedures for each machine or program.
3Object-affected harmful factors
If velocity control is performed to match calculated corner velocity, then shock is suppressed, but feed rate control complexity increases
Solution Approach 1:
The patent simplifies feed rate control by using parameter changes - calculating the corner velocity as a specific parameter based on the rounding angle and allowable velocity difference, then directly controlling the feed rate to match this parameter. This approach avoids complex control algorithms while achieving smooth velocity transition.
Data Source
AI summary
A numerical controller configured to control a machine tool for machining the workpiece on the basis of a machining program composed of a plurality of blocks includes a corner multiple curves inserting unit. This corner multiple curves inserting unit inserts, between consecutive two blocks, three cubic polynomial curves in which a position, a direction and a curvature are continuous and the distances from these two blocks are within a prescribed allowable tolerance, if a direction or a curvature between these two blocks is discontinuous in the machining program.