CNC Look-Ahead Control for Stable Feed Rate on Short Blocks
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Solution Overview
Problem
High-quality machining programs with short minute straight lines and fast command speeds lead to insufficient look-ahead blocks for determining acceleration/deceleration operations, resulting in unstable speed and reduced processing power, especially in multi-axis machining systems.
Innovation Solution
A numerical controller with a program execution unit, look-ahead unit, look-ahead blocks calculation unit, exhaustion block detection unit, and command speed update unit that detects and addresses the position of insufficient look-ahead blocks by calculating and updating the command speed to secure stable feed rates and cutting speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If machining programs use short minute straight lines and fast command speeds to achieve high-quality machining, then machining precision and surface finish are improved, but the look-ahead blocks required for determining acceleration/deceleration operations become insufficient
Solution Approach 1:
The system performs look-ahead processing in advance to analyze upcoming machining blocks and determine acceleration/deceleration operations before execution. By calculating the required look-ahead blocks in advance based on program characteristics, the system ensures sufficient data is available for stable speed control even with short minute straight lines and fast command speeds.
Solution Approach 2:
The system dynamically adjusts the number of look-ahead blocks based on the specific machining program characteristics, such as command speed and block length. This dynamic adaptation allows the system to maintain sufficient look-ahead processing capacity for high-precision machining while optimizing performance for different program types.
2Productivity
If the processing time for executing the program is shorter than the time required for look-ahead processing, then productivity is improved, but the look-ahead blocks required for stable acceleration/deceleration operations cannot be secured
Solution Approach 1:
The system changes the parameter of look-ahead block quantity dynamically based on program characteristics. By adjusting the number of look-ahead blocks according to command speed and block length, the system ensures sufficient processing time for stable acceleration/deceleration while maintaining high productivity through optimized processing parameters.
3Manufacturing precision
If the numerical controller increases processing power to handle look-ahead processing and program execution simultaneously, then machining quality is improved, but device complexity and cost increase
Solution Approach 1:
The system applies partial look-ahead processing by determining the minimum required number of look-ahead blocks based on program characteristics. Instead of processing all possible blocks, the system processes only the necessary amount needed for stable acceleration/deceleration control, reducing computational complexity while maintaining machining quality.
4Productivity
If command speed is increased by making programs more detailed or updating machines, then productivity is improved, but the same problem of insufficient look-ahead blocks occurs
Solution Approach 1:
The system dynamically determines the required look-ahead blocks based on command speed and program characteristics. When command speed increases, the system automatically adjusts the number of look-ahead blocks to maintain sufficient processing capacity, enabling high productivity without sacrificing acceleration/deceleration stability.
Data Source
AI summary
To provide a numerical controller that can detect the position at which the look-ahead blocks used to determine an acceleration/deceleration operation is insufficient in a machining program in order to stabilize feed rate, cutting speed and other factors. A numerical controller includes a program execution unit that executes a machining program, a program look-ahead unit that looks ahead at the machining program in parallel with execution of the machining program, a look-ahead blocks calculation unit that calculates a look-ahead blocks, which is the difference between a first sequence number that is the number of a block being executed by the program execution unit and a second sequence number that is the number of a block that is looked ahead by the program look-ahead unit while the machining program is being executed, and an exhaustion block detection unit that detects an exhaustion block, which is a block at which the look-ahead blocks falls below a prescribed value.