Wire EDM Tension Estimation Using Feed Motor Torque Signals
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Solution Overview
Problem
Wire electrical discharge machines require tension sensors to detect wire electrode tension, which complicates their mechanical structure and increases costs.
Innovation Solution
A control device and estimation method that estimates wire electrode tension using information from motors in the feeding mechanism, eliminating the need for tension sensors by acquiring disturbance loads or torque commands and controlling motors to maintain wire tension between rollers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a tension sensor is used to detect wire electrode tension, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical tension sensor with a control system that calculates tension indirectly using motor drive current and torque command data. The arithmetic operation unit computes wire tension based on the relationship between motor output torque and wire tension, eliminating the need for direct mechanical sensing while maintaining measurement capability.
Solution Approach 2:
The patent introduces motor drive current and torque command as intermediary parameters to infer wire tension. Instead of directly measuring tension with a sensor, the system uses these intermediate electrical parameters that correlate with mechanical tension through the motor's torque characteristics, enabling indirect measurement without additional mechanical components.
2Measurement precision
If a tension sensor is installed to monitor wire electrode tension, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent enables the control system to perform tension measurement functionality using its existing computational resources and available motor data. The arithmetic operation unit leverages data already being collected for motor control (drive current and torque commands) to simultaneously derive tension information, making the system self-sufficient without requiring external sensing hardware.
Solution Approach 2:
The patent makes the control system multi-functional by enabling it to perform both motor control and tension measurement functions using the same hardware resources. The control unit processes motor drive data for its primary control function while simultaneously calculating wire tension, allowing one system to serve multiple purposes and eliminate the need for dedicated tension sensing equipment.
3Measurement precision
If existing tension detection methods are used, then measurement precision is improved, but loss of information occurs due to inability to detect tension during certain operational phases
Solution Approach 1:
The patent enables continuous tension measurement throughout all operational phases by continuously monitoring motor drive current and torque command data. Unlike sensor-based methods that may fail during certain operations, this calculation-based approach maintains tension information availability across the entire wire feeding process, from unwinding through machining to collection.
Data Source
AI summary
Provided are an estimation method. and a control device for a wire electrical discharge machine, the method and device being for estimating the tension of a wire electrode on the basis of information obtained from a motor included in a feed mechanism of the wire electrode. A control device for a wire electrical discharge machine provided with a first motor and a second motor that induce rotation of a first roller and a second roller for feeding a wire electrode, the control device including: an acquisition unit that acquires a noise load and/or a torque command from one of the first motor and the second motor; a feed motor control unit that controls the first motor and the second motor so that the wire electrode is tensioned; and an estimation unit that estimates the tension on the basis of the noise load and/or the torque command for the time when the wire electrode is tensioned.