CNC Look-Ahead Buffer Control for Stable Machining Speed
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Solution Overview
Problem
High-speed and high-precision machining programs face issues with unstable speed control due to insufficient look-ahead blocks, leading to acceleration/deceleration abnormalities, especially in machines with multiple axes, as the processing time for executing programs is shorter than the time required for look-ahead processing.
Innovation Solution
A numerical controller that detects positions in machining programs where look-ahead blocks are insufficient and supplements them by limiting execution or reducing operation speed until sufficient look-ahead blocks are available, ensuring stable feed rate and cutting speed through a program execution unit, look-ahead unit, look-ahead blocks calculation unit, required look-ahead blocks setting unit, and operation limitation unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the processing time for executing the program is increased, then the look-ahead blocks can be secured for stable acceleration/deceleration control, but the productivity decreases due to longer cycle times
Solution Approach 1:
The numerical controller performs look-ahead processing in advance by reading and analyzing multiple program blocks before execution, storing them in a buffer. This preliminary action ensures that acceleration/deceleration operations are determined ahead of time based on future program content, allowing stable speed control without extending the actual machining cycle time.
Solution Approach 2:
A buffer memory is introduced as an intermediary between the program storage and the execution unit. The buffer temporarily holds look-ahead blocks, allowing the controller to prepare acceleration/deceleration operations in advance while the main processor continues executing current blocks, thus decoupling the timing of look-ahead processing from program execution.
2Productivity
If the command speed is increased for high-speed machining, then the productivity improves, but the processing time becomes insufficient for look-ahead operations causing speed instability
Solution Approach 1:
The system reads and analyzes a predetermined number of program blocks in advance (look-ahead blocks) before execution, storing them in a buffer. This preliminary analysis allows the controller to calculate appropriate acceleration and decelereration operations ahead of time, ensuring stable speed control even at high command speeds where processing time is limited.
Solution Approach 2:
The numerical controller dynamically adjusts acceleration and deceleration operations based on the analyzed look-ahead blocks, adapting the speed profile to match the actual program content. This dynamic adjustment ensures stable speed control while maintaining high command speeds for improved productivity.
3Reliability
If more look-ahead blocks are analyzed for stable acceleration/deceleration control, then the speed control stability improves, but the processing load on the CPU increases
Solution Approach 1:
The system analyzes a predetermined number of program blocks (look-ahead blocks) in advance, which is sufficient to determine stable acceleration and deceleration operations without requiring analysis of the entire program. This partial action provides the necessary control stability while limiting the CPU processing load to a manageable level.
Solution Approach 2:
A buffer memory serves as an intermediary that stores the look-ahead blocks after analysis. This allows the CPU to perform the intensive analysis work once and then retrieve the pre-analyzed data during execution, reducing the ongoing processing load while maintaining stable acceleration/deceleration control.
Data Source
AI summary
To provide a numerical controller that can detect a position in a machining program at which a speed control abnormality is likely to occur due to an insufficient look-ahead blocks that are used to determine an acceleration/deceleration operation, and supplement the look-ahead blocks at that position in order to stabilize feed rate, cutting speed and other factors. A numerical controller includes a required look-ahead blocks setting unit that sets a required look-ahead blocks, which is a look-ahead blocks required to execute a machining program, and an operation limitation unit that compares a look-ahead blocks calculated by a look-ahead blocks calculation unit to the required look-ahead blocks and, if the look-ahead blocks is less than the required look-ahead blocks, limits execution of the machining program until the look-ahead blocks reach the required look-ahead blocks.