Spindle Feed Rate Control for Stable Drilling Load Recovery
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Solution Overview
Problem
Conventional drilling techniques face issues such as tool fracture, accuracy deterioration, and burr formation due to constant feed rates, which can lead to prolonged cycle times when attempting to reduce tool load.
Innovation Solution
A numerical controller with an acceleration/deceleration start position calculation unit that decelerates the spindle feed rate in the bite and penetration portions to lower velocities, and a spindle load measurement unit to identify and manage increased loads, allowing for optimal velocity drilling while minimizing tool load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the feed rate is decreased to prevent tool fracture and accuracy deterioration, then tool reliability and manufacturing precision are improved, but cycle time is prolonged
Solution Approach 1:
The patent applies dynamics by transitioning from a static constant feed rate to a dynamic variable feed rate that changes throughout the drilling process. The feed rate is automatically adjusted based on real-time spindle load measurements, allowing the system to optimize between tool protection and productivity without manual intervention.
Solution Approach 2:
The patent changes the feed rate parameter dynamically during the drilling process. By monitoring spindle load and adjusting the feed rate accordingly (decreasing when load increases, increasing when load decreases), the system optimizes both tool reliability and cycle time without requiring fixed conservative parameters.
2Reliability
If the feed rate is decreased in the bite portion to prevent tool fracture, then tool reliability is improved, but the duration of low feed rate increases unnecessarily
Solution Approach 1:
The patent implements feedback control by continuously monitoring spindle load and using this information to adjust the feed rate in real-time. The acceleration/deceleration start position calculation unit receives feedback from the spindle load measurement unit to determine optimal feed rate adjustments, ensuring the low feed rate is maintained only as long as necessary.
Solution Approach 2:
The patent applies preliminary action by calculating and preparing the acceleration/deceleration start positions in advance based on predicted bite portions. This allows the system to minimize the duration of low feed rate by precisely timing when to decelerate before the bite and accelerate after, rather than maintaining low speed for a fixed extended period.
3Ease of operation
If a fixed bite distance is used for low feed rate travel, then ease of operation is improved, but productivity deteriorates due to non-optimal values
Solution Approach 1:
The patent applies self-service by enabling the system to automatically determine optimal bite distances without requiring manual trial and error. The acceleration/deceleration start position calculation unit autonomously calculates the appropriate low feed rate duration based on real-time spindle load feedback, making the system self-optimizing.
Solution Approach 2:
The patent replaces the mechanical trial-and-error adjustment method with an automated control system. Instead of manually adjusting fixed bite distances through repeated testing, the system uses computational algorithms and real-time sensor feedback to automatically optimize the low feed rate duration.
Data Source
AI summary
A numerical controller decelerates a spindle feed rate in a bite portion to a bite velocity lower than a commanded feed rate when drilling is carried out and then, after passage through a velocity recovery point where a measured spindle load is made substantially constant, accelerates the spindle feed rate from the bite velocity to the commanded feed rate.