Wire-cut EDM Tension Control Switching Torque to Speed
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Solution Overview
Problem
Wire electrodes in wire-cut electric discharge machines often break due to unstable tension control during the initial travel phase, especially when manually handled or replaced, leading to excessive load and potential breakage.
Innovation Solution
A wire-cut electric discharge machine with a tension control system that switches from torque control to speed control after a preset time or when tension stabilizes, using motors with integrated tension detection and control mechanisms to maintain a preset tension, reducing the risk of electrode breakage during machining and manual handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If speed control is applied to the motor during initial wire electrode travel, then the wire electrode tension becomes unstable due to static friction and inertial forces, but if no control is applied, the wire electrode breaks due to excessive tension
Solution Approach 1:
The control method dynamically switches between torque control and speed control modes based on the operational phase. During initial travel and manual handling, torque control is applied to maintain stable tension. During normal machining, speed control is applied for precise wire feed. This dynamic adaptation resolves the contradiction by optimizing control parameters for each operational stage.
Solution Approach 2:
The invention changes the control parameter from speed to torque during initial travel and manual handling phases, then switches back to speed control during normal machining. This parameter transformation allows the system to accommodate the unique requirements of each phase: torque control provides tension stability during vulnerable operations, while speed control ensures precise wire feed during machining.
2Device complexity
If the motor drive is stopped for manual wire electrode delivery, then costs and structure are simplified, but a considerable force is required for manual delivery
Solution Approach 1:
The motor provides assisted torque during manual wire delivery without requiring full drive activation. The operator simply guides the wire while the motor supplies sufficient torque to overcome friction and inertia, eliminating the need for complete motor shutdown and reducing the force burden on the operator while maintaining system simplicity.
3Reliability
If torque control is applied during initial travel, then wire electrode tension stability is improved, but the control system complexity increases
Solution Approach 1:
The control system operates in periodic phases: torque control during initial travel and manual handling, then switching to speed control during normal machining. This periodic alternation between control modes allows the system to maintain high reliability when needed while keeping overall system complexity manageable through clear phase-based control logic.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents electrode breakage by stabilizing tension during initial travel and machining, allowing for easier manual handling and reducing the risk of excessive load, thereby ensuring consistent operation and extending electrode lifespan.
Implementation Method 1
a tension detector 6 which is located between the workpiece and the feed roller and detects a tension on the wire electrode
Implementation Method 2
a feed motor M1 for feeding the wire electrode 1 to a workpiece 2 to be machined, and a delivery motor M2 for delivering the wire electrode from the workpiece
Implementation Method 3
the tension is applied to the electrode by using a brake roller that is provided with resistance applying means, such as a powder brake, for controlling torque
Data Source
AI summary
When a wire electrode is arranged along a traveling path by manual operation, a motor M1 for feeding the wire electrode to a workpiece is driven in response to a predetermined torque command from a control section with a switch SW1 on a side a. The wire electrode is connected, and a motor M2 for delivering the electrode from the wire is driven at a predetermined speed, whereby the electrode is run. Then, the switch SW1 is shifted to a side b and a switch SW2 to the side a, and the motor M1 is subjected to torque control such that a tension on the wire electrode detected by a tension detector is equal to a command tension. When a variation of the tension on the wire electrode is converged, the switches SW1 and SW2 are shifted to the side b, speed control of the motor M1 is performed so that detected tension is equal to the command tension, and electric discharge machining is started.