**1. EDM Cutting Machine Fault Diagnosis Principles**
**1.1 Start from the Outside, Not the Inside**
With the continuous advancement of EDM machine control systems, the likelihood of internal control failures has significantly decreased. Most issues are not caused by the mainboard or core control circuits but rather by external components such as damaged wiring or faulty devices. Therefore, maintenance personnel should begin their inspection from the outside and proceed step by step. Avoid disassembling the trigger circuit board, changing system parameters, or altering the operating mode, as these actions could introduce new faults.
**1.2 Combine Mechanical and Electrical Checks**
EDM machines are prone to mechanical failures, which are often hard to detect. Wear and tear on parts is a common cause. Maintenance staff should first inspect the mechanical components around the failure area, checking for cracks, looseness, or fractures. Instead of immediately checking for electrical issues like open circuits or component damage, they should focus on the mechanical side first, as some problems may be misdiagnosed if approached from the wrong angle.
**1.3 Practice After Theory**
Although the control circuits in EDM machines are not overly complex, some technicians skip analyzing the root cause and jump straight into live repairs. This can worsen the fault. It’s essential for maintenance personnel to first understand the symptoms, analyze the possible causes, and develop a theoretical solution before implementing any fixes.
**1.4 Simple Before Complex**
Some failures result from multiple factors. In such cases, it's best to start with the simplest solutions first, addressing the most obvious issues before moving on to more complex ones. By solving simpler problems, the underlying causes of more complicated issues may also become clearer, leading to a more effective and efficient repair process.
**2. Troubleshooting Methods for Wire EDM Cutting Machines**
**2.1 Routine Inspection Method**
Routine inspections are performed by maintenance staff before starting the equipment. These checks include:
(1) **Power Supply**
Check whether the voltage fluctuation is within ±10%, assess the level of harmonics, and ensure the power factor is acceptable. Also, verify if a stabilizer is installed.
(2) **Wire Cutting Fluid**
The fluid serves cooling, cleaning, and chip removal. If it appears dark or has an odor, it may have degraded, leading to frequent wire breaks. Replace it if necessary.
(3) **Electrode Wire (Molybdenum Wire)**
Ensure the wire is properly selected and tensioned. A loose wire can lead to breakage, while a tight one increases internal stress. Check for wear, oxidation, or improper storage conditions that may affect its performance.
(4) **Control Cabinet**
Dust buildup can cause corrosion, short circuits, or damage to components. Regular cleaning is essential to prevent such issues.
*Example 1:* A wire cutter experienced intermittent wire breaks. Upon inspection, the cutting fluid was found to be too dirty, causing poor insulation and irregular breaks. Replacing the fluid resolved the issue.
**2.2 Consumables Inspection Method**
This method involves checking wearing parts after the machine is in operation. Common consumables include guide wheels, wire blocks, conductive blocks, and travel switches.
(1) **Guide Wheel**
A misaligned or worn guide wheel can cause excessive friction and wire breakage. Inspect the surface for grooves or damage.
(2) **Wire Blocking Device**
Check if the wire column is close to the molybdenum wire and if there are any grooves or overlaps on the drum.
(3) **Broken Wire Protection Block**
Ensure the switch is in the correct position. If it’s not closed, adjust the block to restore normal function.
(4) **Conductive Blocks**
Oxidation or deep grooves can cause poor contact, affecting the current flow. Clean or replace as needed.
(5) **Cushion**
Listen for abnormal sounds during direction changes. A damaged cushion can cause vibration and instability.
(6) **Travel Switch**
Check for proper contact and functionality. Malfunctioning switches can cause issues with reversing or cutting high frequency.
*Example 2:* A machine kept running at high frequency even after reversing. The broken wire protection block had deep grooves, causing the microswitch to open and fail to cut off the high-frequency signal. Replacing the block fixed the problem.
**2.3 Principle Analysis Method**
This approach involves understanding the working principle of the WEDM to identify and solve the fault. Techniques include:
(1) **Divide and Conquer**
Break the system into main and control circuits. Analyze each part to narrow down the fault location.
(2) **Reverse Analysis**
Assume certain parts are faulty and simulate what would happen, helping to pinpoint the actual issue.
(3) **Circuit Simulation**
Use software to simulate the circuit and determine if components are damaged, especially when visual inspection is not sufficient.
(4) **Component Replacement**
If diagrams are unavailable, replace suspected components with spares to quickly restore machine operation.
*Example 3:* A machine showed no change in high-frequency output and slow cutting speed. After analysis, the adjustment circuit was identified as faulty. Re-welding the connection restored normal function.
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