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EDM machine inspection checklist

20 maintenance checks for EDM machines (wire EDM, die-sinking EDM, small-hole EDM): 5 common, 6 die-sinking, 8 wire, 1 small-hole. Compiled by interval from machine manufacturers' instruction and maintenance manuals and from published material from parts and oil manufacturers, standards and regulations. What you check off is saved only in this browser.

Intervals differ by machine.
First, check your machine's
manual!

CautionIntervals, 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

Daily (including before start of shift)

Check the machining fluid (EDM oil) level and the level settingDie-sinkingBefore start of shiftWhat to checkMachining tank, level detector (float switch)GuidelineThe fluid surface must be at least 50 mm above the top of the workpiece. Set the machine to stop automatically if the level falls below thatProcedureReview the fluid level setting each time, when the workpiece is raised during setup or replaced with a thicker oneSparks near the fluid surface easily ignite the vaporized oil. There was a fire that injured 2 people when machining continued with the level setting wrongly left below the machined surface. The operating standards of municipal fire prevention ordinances (which apply to EDM machines using a hazardous material as machining fluid) set 50 mm or more. Machines using water-based machining fluid are not covered by the ordinances^{[1][2][3][4][5][6]}
Check the fluid temperature and the temperature setting of the device that stops machining on fluid temperatureDie-sinkingBefore start of shiftWhat to checkFluid temperature detector in the machining tank, machining fluid cooling unitGuidelineThe temperature setting at which machining stops should be 60 °C or lessIn long continuous machining the fluid temperature rises and the ignition risk increases. The maximum allowable fluid temperature is set at 60 °C or less on the assumption that oil with a flash point of 70 °C or more is used. Near-miss cases have been reported in which the machining fluid cooling unit failed, the fluid temperature rose, and a warning was issued and the machine stopped (survey by the Hazardous Materials Safety Techniques Association)^{[1][2][3][5][6]}
Check the tool electrode mounting and the clearance around the electrode headDie-sinkingBefore start of shiftWhat to checkElectrode mounting section, workpiece clamping boltsGuidelineMake sure the electrode is clamped securely. Before starting, check that there is enough clearance so that protrusions such as clamping bolts do not touch the head or spark against itPoor mounting can cause a discharge between the fixture and the electrode that ignites the oil. The ordinances also require the electrode to be mounted securely to prevent abnormal discharge^[2][3][5][7]
Check housekeeping, open flames and ventilation around the machineDie-sinkingBefore start of shiftWhat to checkEDM machine installation siteGuidelineNo heaters, welders, grinders or other ignition sources in use nearby. The ventilation system that removes flammable vapor is running. A no-open-flame sign is postedThe ordinances apply the standards for spark-producing equipment (housekeeping, ban on open flames, ventilation) to EDM machines as well^[2][5][3]
Check that the automatic fire extinguishing system is in working order (extinguishing agent, sensor, indicators)Die-sinkingBefore start of shiftWhat to checkExtinguishing system main unit, sensors, discharge nozzlesGuidelineThe extinguishing agent is at the specified quantity (always refill after it has operated once). The sensors are not dirty. The system's markings (type and quantity of agent, maximum protected area, etc.) are legibleThere have been cases where the agent was not refilled after the system operated in an earlier fire, so it did not operate in the next fire. Cases are also cited where a dirty temperature sensor failed to work and the heated oil ignited^[5][2]
Check the resistivity (conductivity) reading of the machining fluid (water)WireBefore start of shiftWhat to checkResistivity meter reading, ion-exchange resin containerGuidelineIt is held at the machine's set value. When it no longer returns to the set value, the ion-exchange resin has reached the end of its life (Sodick recommends replacing it when resistivity falls below 50,000 Ω in typical metal machining)Keeping the resistivity constant stabilizes machining speed, shape accuracy and surface roughness. Lowering it (raising conductivity) makes the resin last longer but worsens surface roughness^[8][9][10]
Read the pressure gauge of the machining fluid filterCommonBefore start of shiftWhat to checkFilter (filtration unit) pressure gaugeGuidelineReplace it when the specified pressure is exceeded (Sodick: roughly 0.2 MPa). How fast clogging progresses depends on the workpiece and the machining, so do not decide by timeA clogged filter degrades the machining fluid and worsens accuracy and surface roughness. In die-sinking, there was a fire where a clogged filter disrupted circulation and left cooling insufficient^[9][8][5]
Check the remaining wire electrode and the condition of the bobbinWireBefore start of shiftWhat to checkWire bobbin (supply side)GuidelineEnough remains to finish the day's machiningA wire break in the middle of machining affects the machined surface. Near the center of the bobbin the winding radius is small and the wire curl is strong, so automatic threading fails more often^[8](1 source, for reference)
Check the temperature, humidity and vibration of the installation siteCommonDailyWhat to checkSurroundings of the machineGuidelineFANUC example: ambient temperature 15–30 °C, humidity 75% RH or less without condensation; 20 ± 1 °C is recommended for high-accuracy machining. No oil mist or dust. Floor vibration of 2 µm amplitude or less at 10–20 Hz is recommendedThermal displacement of the upper and lower arms and other parts changes the wire's attitude and affects accuracy. Stabilizing the temperature environment is important^[11][8]

Weekly

Clean out the sludge (machining debris) that has collected in the machining tankWireWhat to checkMachining tank, upper and lower nozzlesGuidelineMitsubishi Electric's instruction manual recommends cleaning once a weekIf sludge is left to accumulate, it clogs the nozzle hole the wire passes through, automatic threading fails, and the machine stops repeatedly. Mitsubishi Electric has released a new model whose mechanism was redesigned so that threading still works with some sludge buildup, cutting the number of maintenance tasks to one sixth of the previous model. Check the interval for each model in its instruction manual^[12][13](1 source, for reference)

Annual

Have the machine manufacturer carry out preventive maintenance (periodic inspection)CommonWhat to checkWhole machine (lubrication, safety devices, collision protection, automatic threading device, NC, machining tank, etc.)GuidelineFANUC example: decided according to usage, but roughly every 2,000 operating hours or once a yearCovers lubrication of each axis, safety devices, alignment of each axis, and replacement of wear parts such as seals and bearings, all together^[16](1 source, for reference)

Other (as needed, first time, etc.)

Clean the wire guides (diamond guides)WireEvery 50 machining hoursWhat to checkUpper and lower wire guides and their surroundingsGuidelineSodick recommends every 50 hours of machining time (operating time). No brass powder or dirt on themProcedureSoak in a diluted industrial acid solution to remove deposits. An ultrasonic cleaner removes finer depositsBrass chips, brass powder and dirt build up on the diamond part and around it. The clearance between guide and wire greatly affects machining accuracy^[9][14](1 source, for reference)
Move (index) the power feed contact to a new position and clean itWirePeriodicWhat to checkPower feed contacts of the upper and lower headsGuidelineRe-position it at the interval and by the procedure set by the machine manufacturerThe power feed contact (energizer) carries the machining current to the wire, and re-positioning it keeps machining in good condition (Makino's explanation). No numerical values for the re-positioning or replacement interval were found in published material. Check the instruction manual for the model^[15](1 source, for reference)
Clean and adjust the automatic wire threading device (AWF) and measure the wire tensionWirePeriodicWhat to checkAutomatic threading device, brake roller, tension sensorGuidelineThe brake roller is normal. Measure the tension and adjust it if it is offProcedureMeasure the tension with a wire tension meter (Sodick peripheral equipment)Automatic threading failure is a major cause of interrupted unattended running. Tension is controlled to suppress wire vibration from discharge reaction force and keep the wire straight^[16][14][8]
Inspect and clean the machining tank door seal, seal plate and level switchWirePeriodicWhat to checkMachining tank door, seal plate (arm pass-through), float switch (water level sensor)GuidelineThe door seal is undamaged. The seal plate is in firm contact. The water level is detected correctlyMachining debris on the seals increases friction and lowers machining accuracy. FANUC uses a structure that resists debris buildup and a transparent seal plate that is easy to disassemble and clean^[16][11](1 source, for reference)
Check and record the operation of the fire-prevention safety devices and the automatic fire extinguishing systemDie-sinkingPeriodicWhat to checkFluid temperature detection, level detection and abnormal machining (carbonized product) detection devices; automatic fire extinguishing systemGuidelineMachining stops when fluid temperature, set level, and abnormal machining are each detected. The extinguishing system's fire detection, alarm and machining stop, and their interlock, all work. Record the results, and if there is a defect, fix it before useThe ordinances require the necessary inspection and maintenance. In most accident cases the safety devices were not fitted or did not work, while cases where the devices worked ended in successful extinguishing. The Hazardous Materials Safety Techniques Association's new draft standard also adds a periodic visual inspection to find problems such as clogged filters^[5][2][3]
Replace the NC batteries and back up the machine data and NC dataCommonPeriodicWhat to checkNC unit and servo batteriesGuidelineBatteries have been replaced as specified. A backup copy of the data existsData may be lost if the battery runs out. FANUC includes battery replacement and backup in preventive maintenance, and Makino also recommends doing so before shutting the machine down for a long time^[16][17]
Fit a guide (anti-runout guide, intermediate guide) that matches the pipe electrode diameterSmall-holeAt setupWhat to checkElectrode guide (die guide), intermediate guideGuidelineThe guide hole diameter matches the electrode diameter, with little playThe less play in the guide, the more efficiently the machining energy goes into drilling (with a φ0.08 mm electrode, a φ0.08 mm guide drilled deeper than a φ0.1 mm one). Supporting a long electrode with an intermediate guide prevents wobble and bending. Makino's small-hole EDM machines exchange the die guide and electrode as a pair^[18][14][19]
Check the wire verticality (squaring up)WireAt setupWhat to checkWire, upper and lower guidesGuidelinePlace the verticality jig on a reference verified to be flat; the wire is verticalIf the wire is tilted, the squareness and dimensions of the machined surface are off^[20][14]
When shutting the machine down for a long time, apply rust prevention and cut and lock out the powerCommonLong-term shutdownWhat to checkWhole machineGuidelineMakino example: for die-sinking, leave the EDM oil in (the oil acts as rust prevention). For wire, if shutting down fully, clean the wire path and remove the bobbin; if stopping with periodic checks, drain the water and clean the tank. In both cases, apply rust preventive to bare metal surfaces, confirm that grease has reached each axis and ball screw, back up the data, then switch off the power and lock it outLeftover water or machining debris causes rust and seizure^[17](1 source, for reference)

📚Sources

Items without a mark are those confirmed by two or more sources from different publishers. Intervals, oil types and values: the specification for each machine takes priority. The text is summarized in Kezuriba's own words.