Printed from Kezuriba (kezuriba.net/en/maintenance/edm/troubles/)
EDM machine troubleshooting quick reference
Look up likely causes, what to check, and remedies from the symptom. Intervals, set values and oil types follow the machine manufacturer's instruction manual, which takes priority; the values here are examples from published sources. EDM machines that use a hazardous material as the machining fluid fall under municipal fire prevention ordinances in Japan, so follow the guidance of the local fire department on installation notification and handling of stored quantities
Wire breaks oftenWire
| Likely cause | What to check | Action |
|---|---|---|
| Discharge energy is too high, or flushing (jet) is insufficient | Machining conditions, jet pressure and flow rate | Lower the energy input, for example by lengthening the off time. Raise the fluid flow and pressure (with thin workpieces, take care that the water pressure does not move them)[1][2][3] |
| Upper nozzle is away from the workpiece (workpiece with steps or unevenness) | Gap between upper nozzle and workpiece (about 0.05–0.10 mm is recommended for close-contact machining) | Bring the nozzle as close to the workpiece as possible. For a stepped workpiece, use the machine's machining mode for thin plates and steps, or consider a method that keeps the gap smallIn a test by Kyoto Prefecture, wire breaks were more likely with a high upper nozzle, low flow rate, and a step below the workpiece. Breaks at a step are caused by concentrated discharge from excessive conditions and similar causes[4][3][2] |
| Plate is thick, so machining fluid hardly reaches the gap | Plate thickness, machining conditions, wire diameter | Strengthen flushing and reduce the energy input. A thicker wire is less likely to break (but the minimum corner radius becomes larger)[1](1 source, for reference) |
| Bubbles collect in the gap and the wire stops being cooled locally | Whether short circuits have increased | Raise the servo reference voltage to widen the gap between wire and workpiece, and slow the table feed at the same time[2](1 source, for reference) |
Automatic threading fails, machine stops repeatedlyWire
| Likely cause | What to check | Action |
|---|---|---|
| Sludge has collected in the machining tank or nozzle hole | Bottom of the machining tank, holes of the upper and lower nozzles | Clean out the sludge regularly (Mitsubishi Electric's instruction manual recommends once a week)[5][6](1 source, for reference) |
| Wire curl is strong near the center of the bobbin | Remaining wire | Replace a bobbin early once it is running low[1](1 source, for reference) |
| Dirt on the automatic threading device or misadjustment | Automatic threading device, brake roller, tension | Clean and adjust the automatic threading device, then measure the tension and set it[7](1 source, for reference) |
Waviness or streaks on the machined surfaceWire
| Likely cause | What to check | Action |
|---|---|---|
| The gap between the upper nozzle (upper guide) and the workpiece is large, and bubbles make the wire vibrate | Gap between nozzle and workpiece | Reduce the gap (nozzle in contact with the workpiece)[4](1 source, for reference) |
| Poor wire roundness | Wire brand and lot | Use a wire with controlled roundness and high surface accuracy (in OKI Electric Cable's example, waviness improved by about 30%)[8](1 source, for reference) |
Middle of the plate thickness bulges or is dented (barrel shape)Wire
| Likely cause | What to check | Action |
|---|---|---|
| Dielectric does not reach the middle of the plate thickness, debris concentration rises, and secondary discharge occurs | Plate thickness, nozzle contact, flushing pressure, tension | Adjust the wire tension, reduce the machining energy, and set the flushing pressure with the nozzle in contact with the workpiece[1][4] |
Dimensions or shape are offWire
| Likely cause | What to check | Action |
|---|---|---|
| Thermal displacement of the upper and lower arms, etc. | Changes in room temperature; dimensional change with time of day of machining | Stabilize the temperature environment (for high-accuracy work, 20±1℃ is recommended in some cases)[1][9] |
| The 1st cut releases internal stress in the material and the workpiece distorts | Dimensions after the 1st cut | Stress-relieve after the 1st cut before finishing. Provide the start hole so that no distortion arises during machining[1][10] |
| Wire is not vertical | Wire verticality with a verticality jig | Redo the verticality adjustment[10][11] |
| Wire guide diameter does not match or the guide is dirty | Guide diameter and contamination | Use a guide of the specified diameter and clean it[12](1 source, for reference) |
| When finishing the uncut part, the part being cut off moves | Fixing of the uncut part | Secure it with a fixing jig, wire, copper plate, etc. before finishing[1](1 source, for reference) |
Resistivity will not rise (conductivity will not fall), resin is used up quicklyWire
| Likely cause | What to check | Action |
|---|---|---|
| The ion-exchange resin has lost its exchange capacity | Resistivity meter reading (Sodick recommends replacement when it falls below 50,000 Ω) | Replace the ion-exchange resin[12][13] |
| Resistivity is set high (conductivity set low) | Set value | Match it to the value the machining needs. The lower the conductivity, the faster the resin is used upMitsubishi Electric states that lowering the conductivity extends resin life but worsens surface roughness (a trade-off between resin life and surface roughness)[13](1 source, for reference) |
Workpiece or fixture rusts or discolorsWire
| Likely cause | What to check | Action |
|---|---|---|
| Electrolytic corrosion in water | Conductivity, power supply type, time left standing after machining | Do not raise the conductivity more than necessary. Suppress it with a bipolar circuit, sacrificial electrode, additives, removal of machining debris, etc. Anti-corrosion ion-exchange resin is another option[1][14] |
| Contact between dissimilar metals (galvanic corrosion) | Materials of the workpiece and fixture | Do not leave metals of different potential in contact in water[1](1 source, for reference) |
| Cobalt in cemented carbide dissolves electrolytically in water | Workpiece material (cemented carbide) | Wire EDM in oil dielectric is said to prevent electrolytic dissolution of cobalt[15](1 source, for reference) |
| Water is left in the machine during a long shutdown | Shutdown period | For a long shutdown, drain the water, clean the tank, and apply rust preventive to bare metal surfaces[16](1 source, for reference) |
Machining becomes unstable, speed or surface quality dropsCommon
| Likely cause | What to check | Action |
|---|---|---|
| Machining debris (EDM chips) accumulates in the gap | State of dielectric handling (flushing, suction, jump) | Review the dielectric handling[1](1 source, for reference) |
| Dielectric quality is poor because of clogged filters | Filter pressure gauge | Replace the filter when the pressure exceeds the specified value[1][12][6] |
| Resistivity deviates from the set value | Resistivity meter | Return it to the set value, for example by replacing the resin[1](1 source, for reference) |
| The contact surface of the power feed contact is worn | Record of power feed contact position changes | Change the position of the power feed contact (indexing)[17](1 source, for reference) |
Abnormal arcing or abnormal discharge occursDie-sinking
| Likely cause | What to check | Action |
|---|---|---|
| Debris accumulates locally; flushing is insufficient | Flushing direction and volume, electrode jump settings | Flush the dielectric sufficiently. Use a longer electrode jump stroke and a higher jump speed[18][1] |
| Off time for roughing is too short or the average machining current is too high | Machining conditions | Lengthen the off time and reduce the average machining current[18](1 source, for reference) |
| Carbonized products are growing between the electrode and the workpiece | Operation of the abnormal-machining detector; state of electrode and workpiece | Set it so that machining stops automatically when an abnormality is detected. If left alone, the carbide grows up to the liquid surface, discharges there, and ignites the oil[19][20][21] |
Machining oil caught fire (fire, small fire)Die-sinking
| Likely cause | What to check | Action |
|---|---|---|
| Machined with the liquid level too low (including an incorrect level setting) | Liquid level setting and level detector | Set the level to stay at least 50 mm above the top of the workpiece, and confirm that the machine stops automatically when the level drops[20][21][22] |
| Machined while spraying dielectric on the workpiece, or with the level detector disabled | Machining method, state of safety devices | Do not machine by spraying, do not run empty discharge with the tank empty, and do not machine with safety devices removed (prohibited by ordinance)There is a case where pliers were inserted into the level detector to hold it fixed, and machining without dielectric caused a fire[20][22][23] |
| Abnormal discharge grew carbide, which discharged at the liquid surface | Abnormal-machining detector | Check the operation of the abnormal-machining detector regularly. In one case, dielectric leaked from the electrode flushing hole mounting, the flushing pressure dropped, and carbide accumulated[20][21] |
| Circulation was poor because of clogged filters, and the dielectric did not cool | Filter pressure, dielectric circulation | Replace the filter and check circulation and fluid temperature[20](1 source, for reference) |
| The temperature sensor was dirty and did not work | Cleaning and operation of the fluid temperature detector | Inspect and clean regularly[21](1 source, for reference) |
| Oil with a low flash point (such as kerosene) was used | Flash point of the dielectric in use | Use EDM oil with a flash point of 70℃ or higher (ordinance prohibits oil below 70℃)Of the cases collected by the Japan Association for Safety Technology of Hazardous Materials (JASTHM), 2 used kerosene (Class 2 petroleum)[20][21][24] |
| The extinguishing agent in the automatic fire extinguisher was not refilled after the previous activation | Amount of extinguishing agent | Always refill after it operates and inspect its function regularly[20](1 source, for reference) |
Electrode wear is highDie-sinking
| Likely cause | What to check | Action |
|---|---|---|
| Machining conditions cause high electrode wear | Pulse width, polarity, energy | Use near-no-wear conditions (oil dielectric with discharge energy above a certain level). Very low-energy finishing tends to increase wear[1](1 source, for reference) |
| Electrode material is not suited to the machining | Combination of electrode material and workpiece; corner wear | Choose an electrode material with high strength and heat resistance (the key is to limit corner wear)[25][1] |
| Wear is concentrated at the corners | Corner shape | Orbiting (orbital machining) can reduce corner wear[1](1 source, for reference) |
Cracks (microcracks) appear on the machined surface, or the die cracksDie-sinking
| Likely cause | What to check | Action |
|---|---|---|
| Microcracks on the EDM surface and insufficient finish polishing | Observation of the machined surface | Use electrode jump or orbiting. Finish with low-current pulses at positive polarity. Remove the recast layer by lapping or blasting[18][1] |
| Roughing discharge energy is high or the material has residual stress | Roughing conditions, heat treatment (tempering temperature) | Reduce the roughing energy and lengthen the off time. Round the edges and corners of the roughing electrode. Use high-temperature tempered material[18](1 source, for reference) |
Pinholes or streak patterns appear on the machined surfaceDie-sinking
| Likely cause | What to check | Action |
|---|---|---|
| Abnormal structure or non-metallic inclusions in the workpiece | Lap the stock before machining and check its structure | Review the material[18](1 source, for reference) |
Electrode jams in the guide, or the hole is crookedSmall-hole
| Likely cause | What to check | Action |
|---|---|---|
| Carbon built up on the electrode tip, thickening it, and the shortened tip was pulled up into the guide | Electrode tip and guide position | Use an operating sequence in which the guide is raised as the electrode is raised. Start machining with weak conditions[26](1 source, for reference) |
| A long electrode wobbles or bends | Electrode overhang length, presence of an intermediate guide | Support the electrode with an intermediate guide[11][27] |
Causes on the side of machining conditions and tools are covered in the Machining Troubleshooting Encyclopedia .
📚Sources
Items without a mark are those on which two or more materials from different publishers agree. Values and intervals are governed by each machine's specifications. The text is summarized in Kezuriba's own words.
- Sodick, "Frequently asked questions (wire EDM and die-sinking EDM)" (in Japanese)
- Osaka University, Joining and Welding Research Institute, technical report "Technical survey (wire EDM): why does the wire break?" (2022)
- Kyoto Prefectural Technology Center for Small and Medium Enterprises, research report (FY2014), "Measures to prevent wire breakage in wire EDM: wire EDM of thin plates with a concave cross-section"
- Nagoya University, technical report "Development of scanning wire EDM by Z-axis feed control" (Technical Center, Nagoya University)
- Mitsubishi Electric, "The Art of Manufacturing [Wire EDM MG series], Part 3: What mattered was the frequency of maintenance" (in Japanese)
- Mitsubishi Electric, "Mitsubishi Denki Giho Vol. 100 No. 4 (2026), New wire EDM machine 'MG series'" (in Japanese)
- FANUC Europe (FANUC's European subsidiary), "ROBOCUT Preventive Maintenance (contents and intervals of preventive maintenance)"
- Oki Electric Industry (OKI Technical Review; written by group company OKI Electric Cable), "OKI Technical Review No. 237 (2021): Electrode wire for EDM machines achieving high-accuracy machining of metal surfaces" (in Japanese)
- FANUC, "Wire-cut EDM ROBOCUT α-CiC series catalog (RCUT-CiC(J)-07)" (in Japanese)
- Niigata University, "Faculty of Engineering, Machine Practice Textbook, Chapter 5 Electrical Discharge Machining (Wire EDM precautions and electric shock)" (in Japanese)
- Sodick, "Supplies and peripheral equipment (verticality jig, wire tension meter, ultrasonic cleaner, intermediate guide, etc.)" (in Japanese)
- Sodick, "Frequently asked questions (supplies): wire guides, filters, ion-exchange resin, pipe electrodes, machining fluid" (in Japanese)
- Mitsubishi Electric, "The Art of Manufacturing, feature article: World-strategy wire EDM machine 'MV series', Part 3 (running cost: filters and ion-exchange resin)" (in Japanese)
- Iwate University, "Research Seeds Mechanical-12: Corrosion protection of ferrous metals in water (corrosion protection of wire EDM machining water)" (in Japanese)
- Okayama University, thesis abstract "Study on optimizing oil dielectric characteristics for high-performance wire EDM"
- Makino Inc. (the U.S. subsidiary of Makino), "Machine layup suggestions (23 March 2020; recommendations for long-term shutdown, including die-sinking and wire EDM machines)"
- Makino Inc. (the U.S. subsidiary of Makino), "Tech Tip - Simple & Quick Energizer Indexing on Makino Wire EDM Machines"
- Osaka Research Institute of Industrial Science and Technology, Technical Sheet No.98018 "Troubles on EDM surfaces in die making and countermeasures"
- Hazardous Materials Safety Techniques Association, "Safety & Tomorrow No. 148 (2013), Explanation of hazardous materials terms (Part 23): EDM machines" (in Japanese)
- Hazardous Materials Safety Techniques Association, "Report on the review of test and confirmation standards for EDM machines (March 2016)" (in Japanese)
- Sapporo City Fire Department, "Purpose and explanation of the Sapporo Fire Prevention Ordinance Article 14-2 (EDM machines)" (in Japanese)
- Funabashi City Fire Department, "Section 16 Operation of the ordinance on EDM machines (Ordinance Article 10-2)" (in Japanese)
- Hiroshima City Fire Department, "Explanation of the Hiroshima Fire Prevention Ordinance Article 11-2 (EDM machines)" (in Japanese)
- Fire and Disaster Management Agency, Ministry of Internal Affairs and Communications, "Fire Prevention Notice No. 198 (30 September 1991), Partial amendment of the model fire prevention ordinance (new standard for EDM machines)" (in Japanese)
- Entegris (POCO Graphite), "An Added Layer of EDM Knowledge (choosing electrode material and wear)"
- Iwate Industrial Technology Center, "Research report (FY2007): Improving the accuracy of fine holes by generating EDM" (in Japanese)
- Makino Inc. (the U.S. subsidiary of Makino), "EDBV3 (small-hole EDM machine; simultaneous exchange of die guide and electrode, intermediate guide, deionized water management)"