Chuck Closing-Time Sensing for Stable Gripping Force Control
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Solution Overview
Problem
The holding force of a chuck in a machine tool is difficult to measure directly, and the relationship between the control amount and the holding force is not consistent due to factors like chuck wear and lubrication changes.
Innovation Solution
A method and system for detecting the holding force of a chuck by measuring the time difference between when a control signal is sent to close the chuck and when it is fully closed, using sensors and a control unit to adjust the tightening amount and maintain a desired holding force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the holding force is determined from the control amount of the open/close mechanism, then the control is simple, but the measurement precision deteriorates due to inconsistent relationship caused by chuck wear and lubrication changes
Solution Approach 1:
The patent replaces the mechanical control-amount-based holding force determination with a time-based measurement system. By measuring the time from when the chuck contacts the workpiece to when the holding force is generated, the system substitutes mechanical parameter measurement with temporal parameter measurement, which remains consistent despite wear and lubrication changes.
Solution Approach 2:
The patent introduces time as an intermediary parameter to indirectly measure holding force. Instead of directly measuring the difficult-to-obtain holding force or relying on inconsistent mechanical control amounts, the system uses time as a mediator that can be precisely measured and correlates reliably with holding force generation.
2Device complexity
If the holding force is determined from control amount, then no additional measurement system is needed, but the reliability deteriorates due to varying relationship between control amount and actual holding force
Solution Approach 1:
The patent substitutes the unreliable mechanical control-amount-based determination with a time-based determination system. This substitution adds minimal complexity (timing measurement) while significantly improving reliability, as time measurement is not affected by chuck wear or lubrication conditions.
Solution Approach 2:
The patent implements a feedback mechanism where the measured time is used to determine actual holding force, which can then be used to adjust control parameters. This closed-loop feedback ensures reliable holding force control by continuously verifying the actual state rather than assuming it based on control amount alone.
3Measurement precision
If direct measurement of holding force is attempted, then measurement precision would improve, but device complexity increases significantly
Solution Approach 1:
The patent uses time as an intermediary that is easy to measure with standard control system components. This intermediary provides accurate holding force information without requiring complex force sensors or measurement apparatus, thus achieving high measurement precision with minimal added complexity.
Solution Approach 2:
The patent replaces complex mechanical force measurement systems with a simple time-based measurement approach. By measuring temporal parameters instead of direct mechanical forces, the system achieves accurate holding force determination using standard control system timing capabilities rather than specialized force sensing equipment.
Data Source
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AI summary
Provided is technology which enables suitable control of a chuck gripping force. In this machine tool comprising a main shaft provided with a chuck for gripping a workpiece, when an open/close mechanism has performed a closing operation on the chuck such that the chuck enters a closed state from an open state, a gripping force of the chuck on the workpiece in the closed state is acquired on the basis of the magnitude of a difference between a first time taken from when a control unit emits a control signal for the closing operation to the open/close mechanism to when a sensor detects that the chuck is no longer in the open state, and a second time taken from when the control unit emits a control signal in an open/close period to when the sensor detects that the chuck has entered the closed state.