CNC Drilling Dwell Control for Hole Bottom Accuracy
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Solution Overview
Problem
Existing numerical controllers face challenges in optimizing dwell time at the hole bottom during drilling, leading to inadequate machining accuracy due to insufficient or excessive dwell time, and require cumbersome manual adjustments to minimize cycle time.
Innovation Solution
A numerical controller with a dwell computation unit that calculates dwell time based on a specified rotation amount and accounts for machine delay, ensuring the dwell time is adequate at the hole bottom position, allowing for precise control of spindle rotation and efficient drilling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the dwell time at the hole bottom is increased to improve machining accuracy, then the machining accuracy is improved, but the cycle time becomes longer
Solution Approach 1:
The patent applies dynamics by making the dwell time variable rather than fixed. The control unit dynamically adjusts the dwell time based on the actual spindle speed and rotation amount, allowing the system to optimize between machining accuracy and cycle time for each specific machining condition. This resolves the contradiction by enabling adaptive dwell time selection that improves accuracy when needed while minimizing cycle time when possible.
Solution Approach 2:
The patent changes the parameter of dwell time from a static prescribed value to a dynamically calculated value based on actual machining conditions. By calculating dwell time as a function of spindle speed and required rotation amount, the system can adjust this parameter in real-time to achieve optimal machining accuracy without unnecessarily extending cycle time.
2Ease of operation
If a uniform dwell time is commanded to simplify programming, then the programming complexity is reduced, but the cycle time cannot be minimized
Solution Approach 1:
The system applies self-service by automatically calculating the appropriate dwell time based on the prescribed rotation amount and actual spindle speed, eliminating the need for manual dwell time programming. The control unit serves itself by computing the optimal dwell time internally, thus maintaining programming simplicity while enabling cycle time optimization through automated calculation.
Solution Approach 2:
The patent changes the approach from specifying absolute dwell time to specifying rotation amount. This parameter change allows the system to automatically convert the rotation requirement into an appropriate time value based on actual spindle speed, simplifying programming while optimizing cycle time through dynamic calculation.
3Device complexity
If the dwell time is commanded without accounting for machine delay, then the programming is simpler, but the actual dwell time at hole bottom is insufficient causing uncut parts
Solution Approach 1:
The patent applies preliminary action by having the control unit pre-calculate the dwell time to include compensation for machine delay. By anticipating the delay between command issuance and actual tool arrival at the hole bottom, the system proactively adjusts the dwell time command to ensure sufficient actual dwell time, preventing uncut parts while maintaining straightforward programming.
Solution Approach 2:
The system uses feedback by incorporating the actual spindle speed measurement into the dwell time calculation. The control unit receives feedback on the real spindle speed and uses this information to calculate the appropriate dwell time that accounts for machine delay, ensuring accurate hole bottom machining without increasing programming complexity.
Data Source
AI summary
A drilling machine performs a feed operation while rotating a spindle, suspends the feed operation of the spindle for a predetermined dwell time at a predetermined hole bottom position, and then performs drilling by retreating the spindle. A controller for controlling the drilling machine calculates the dwell time based on a prescribed rotation amount in response to specification of the prescribed rotation amount (dwell rotation amount) at the hole bottom position.