Machining center inspection checklist (before start-up, daily, weekly, monthly, annual) and maintenance

Daily (including before start of shift)

Check the lubricating oil, coolant oil, and hydraulic oil levelsCommonBefore start of shiftWhat to checkSlideway lubrication (automatic oiler) tank, spindle lubricating oil and spindle cooling oil temperature controller (oil controller), hydraulic unit, ATC oil level gaugeGuidelineWithin the oil level gauge range. Makino's spindle lubricating oil: at or above the lower limit (red line) while running, and at least 1/2 while stopped. If low, top up to the upper limit.ProcedureTop up only after turning the power off and applying lockout/tagout. Do not remove the cylindrical filter at the filler port. Do not use any oil other than the one specified (do not mix oils of different brands, even at the same viscosity).Running the pump without oil damages the unit. Neglecting replacement and top-up shortens the life of the spindle and machine without being noticed in daily use (Makino). If the oil level drops abnormally, suspect a leak or failure (Makino). In Haas's VMC maintenance schedule, the axis lubrication and spindle lubrication tank levels are checked "monthly", not daily.^{[1][2][3][4][5]}
Check the pressure of the pneumatic unit (air control unit, FRL)CommonBefore start of shiftWhat to checkRegulator and pressure gauge at the machine air inletGuidelineThe specified pressure for each machine. If adjusting does not bring it to the specified value, check the factory-side compressor and piping (Makino).Air is used to drive the ATC arm and shutter, to unclamp the spindle tool, to seal the inside of the spindle and scales, and to clean the spindle taper. Insufficient pressure or flow leads to ATC and clamping faults.^[4][1][6][7]
Clean the spindle taperCommonBefore start of shiftWhat to checkSpindle taper boreGuidelineNo chips, dirt, or rust. Hurco says to wipe it with a cloth moistened with clean light oil, and if the machine will sit idle, to wrap the taper in a cloth moistened with the oil from the automatic oiler.ProcedureUse the supplied cleaning tool or a lint-free cloth. Do not use an air gun (chips and coolant get into the spindle and damage the seals = Makino; it ruins the bearings of a built-in spindle = Hurco).Dirt, scratches, and misalignment of the taper worsen machining accuracy and surface finish (Haas). The interval differs by source: Hurco daily, Makino before using the machine, Haas's procedure monthly ("as needed" in maintenance schedule RD0080).^[4][5][8]
Check the coolant levelCommonBefore start of shiftWhat to checkCoolant tank level gaugeGuidelineWithin range. Top up if low. Do not fill above the upper limit (the liquid returning with the chips will overflow = Makino). Hurco says to check every 8 hours if running more than 8 hours. Haas's maintenance schedule says weekly.^{[4][9][10][11]}
Warm up the machine before machiningCommonBefore start of shiftWhat to checkSpindle and all feed axesGuidelineHurco: for a machine that has been stopped for 8 hours, run the warm-up cycle (raise the spindle speed in steps and move the axes too) before cutting. Makino: as an example after a long stoppage or right at the start of the day, about S1000 for the spindle and about F1000–2000 for the feed, over the full stroke, for about 30 minutes.Prevents part damage and poor machining accuracy from sudden movement (Makino). Spreads the lubricant and stabilizes the temperature of the main components (Hurco). Makino notes that its example is not a warm-up for high accuracy. The Machine Tool Engineering Foundation (Japan) says it has generally been thought to take 2 hours or more to reach thermal stability, and that a warm-up of about 20–120 minutes has been considered necessary.^{[4][5][12][13]}
Walk around the machine and look for oil leaksCommonBefore start of shiftWhat to checkUnder the machine and around the unitsGuidelineNo pools of oil^[4][5]
Check the window for damage and the operation of the door interlockCommonDailyWhat to checkFront and side door windows (polycarbonate) and interlocksGuidelineNo scratches, cracks, or deformation in the window. Automatic operation is not possible with the door open, and the door does not open during operation.The window protects the operator from flying tools and workpieces. Hurco says impact resistance drops by up to 10% per year from cutting fluid, lubricants, and ultraviolet light, and recommends replacement within 3 years. There has been a fatal accident in which a worker was caught between the table and the frame on a machine whose interlock had been disabled by modification (Ministry of Health, Labour and Welfare (MHLW) (Japan) case 101204).^[11][4][14]
Check the wipers and telescopic covers on the sliding parts for damageCommonDailyWhat to checkWipers on the feed axis covers, surface of the telescopic coversGuidelineNo chips stuck to the wipers, and no scratches, cracks, or gaps. No large scratches or dents in the covers.Damaged wipers let chips and coolant into the covers and quickly damage the linear guides, ball screws, and wiring (Makino). Okuma America says to check the wipers daily and replace them every 1–2 years. Makino says to follow each model's periodic maintenance manual for the replacement interval.^{[4][5][15][16]}
Clean the toolholder taper and flange and check for damageCommonDailyWhat to checkHolder taper, flange, pull studGuidelineNo dirt, rust, or dents. Hurco wipes and inspects the tools daily, and each holder weekly, with a cloth with light machine oil, then returns it to the magazine.The taper of a damaged holder transfers the damage to the spindle taper during machining (Okuma, Haas).^{[4][17][15][18]}
Clean the tool lock pins and gripper fingers of the ATC armCommonDailyWhat to checkThe two lock pins at the center of the top of the ATC arm, and the gripper fingers at both endsGuidelineNo chips or debrisChips keep the lock pins and fingers from working properly.^[4](1 source, for reference)
Remove chips from the machining area, covers, ATC, and conveyorCommonDailyWhat to checkAround the table, feed axis covers, ATC (arm and shutter), chip conveyor, chip screenGuidelineNo chips piled upProcedurePut a holder with no cutting tool on the spindle and turn the power off first. Do not blow chips away with an air gun. Remove large debris by hand and wear protective gloves (Makino).Piled-up chips get in through gaps in the covers and cause failures of the ball screws, bearings, feed axis covers, ATC shutter, and the conveyor inside the machine. Left alone, they pack down and become hard to remove (Makino). In Haas's maintenance schedule, chip cleaning of the ATC is weekly.^{[4][19][9][11]}
Watch for chips accumulating on the table and workpieceVerticalDailyWhat to checkTop surfaces of the table, fixtures, and workpieceGuidelineNo chips piled upOn a vertical machine the workpiece is cut from above, so chips tend to build up. On a horizontal machine the cut is from the side, so chips fall away naturally and the risk of tool breakage is also lower (Makino). Makino's article "What is a machining center" says a vertical machine needs routine chip removal with air or coolant, while its cleaning article warns against blowing chips away with an air gun (read these as separate: chip evacuation during machining versus cleaning work).^[20](1 source, for reference)
Feel the guideways to check for an oil filmCommonDailyWhat to checkGuideways of each axisGuidelineA thin film of oil on the guide surfaces of all axesLets you notice an automatic oiler fault before an alarm appears.^[4](1 source, for reference)
Move each axis through its full stroke and turn the spindle by handCommonDailyWhat to checkX, Y, and Z axes, spindleGuidelineThe axes move smoothly and the limit switches work correctly. With the power off, the spindle turns easily by hand.Finds binding, abnormal noise, and limit faults before machining.^[4](1 source, for reference)
Run the spindle at various speeds and check the sound and vibrationCommonDailyWhat to checkSpindleGuidelineStart, stop, and rotation are smooth from lowest to highest speed. Hurco says to loop a tapping motion at 800 min⁻¹ and check for no abnormal noise or vibration and smooth speed changes.Abnormal spindle noise can be a sign of a problem with the drive belt, encoder belt, lubrication, or the like (Haas).^[4][21]
Pre-lubrication and warm-up cycle for high-speed built-in spindlesCommonDailyWhat to checkHigh-speed (e.g. 18000 min⁻¹) built-in spindles and motorized spindlesGuidelineHurco's example: 60 minutes after the spindle stops (90 minutes for an electrospindle), run the pre-lubrication and warm-up cycle.In a spindle with oil-air lubrication, the oil film in the bearings runs short while it is stopped.^[4](1 source, for reference)
Check around the spindle for leaks and seal damageCommonDailyWhat to checkSpindle nose and spindle sealsGuidelineNo oil leaks, damage, or wear^[4][5]

Weekly

Measure the tool clamping force (pull-in force, drawbar force)CommonWhat to checkSpindle clamping mechanism (disc springs, drawbar)GuidelineInsert a pull-in force gauge in the spindle, measure, and compare with the manufacturer's value. Haas says to suspect cracked or broken disc springs if it has dropped to about 50% of nominal.A drop in pull-in force can cause fretting of the holder, chatter, tools coming loose, and tools dropping during ATC. The interval differs greatly: Hurco weekly, Haas annually. See the table on the "Toolholders and spindle taper" page for values.^[4][11]
Measure and record the coolant concentrationCommonWhat to checkWater-soluble cutting fluidGuidelineThe proper concentration for each product. The example in Makino's article is 5–15%. Concentration = refractometer reading × the product's conversion factor. Measure the fluid coming out of the nozzle, not the fluid at the tank surface (to avoid the effect of tramp oil).Low concentration causes reduced cutting performance, rust, and spoilage; too high causes foaming, stickiness, gelling, and skin irritation (Makino). Haas says to write it in the log sheet weekly. For details on coolant management, also see the data in the "Common" category.^[11][22][10]
Check the pressure of the spindle air regulatorCommonWhat to checkSpindle air regulatorGuidelineThe specified pressure for each model^[11](1 source, for reference)
Clean the filters of the control cabinet heat exchanger and fans, and the vents of the driveCommonWhat to checkHeat exchanger on top of or on the door of the control cabinet, vents of the vector drive (servo amplifier)GuidelineNo dust buildup. Hurco says to remove the filter, wash it with water, dry it, and put it back.To let heat escape from the cabinet. Makino gives an example where the fans got dirty after years of use and stopped, triggering a "radiator cooling fan stopped" alarm. Hurco weekly, Haas monthly.^[4][11][23]
Remove chips from the ATC and magazineCommonWhat to checkSide-mount and umbrella tool changersGuidelineNo chipsChips interfere with the proximity sensors and the movement of the shuttle, causing a tool change alarm (Haas's umbrella changer diagnostic table).^[11][4]
Check the oil cup of the unclamp cylinderCommonWhat to checkOil cup of the spindle tool unclamp cylinder (Hurco models)GuidelineISO VG32 oil, filled to 1/3 (not more than 1/2)^[4](1 source, for reference)
Remove chips from the APC (pallet changer) and its receiving side, and clean the locating pins, bushings, and tapersHorizontalWhat to checkPallet receiving side, locating pins and bushings, the table-side taper cones and the pallet-side tapers, pallet clamp switchesGuidelineNo chipsProcedureMakino's example: in maintenance mode, raise the APC arm and wipe the taper cones and the pallet-side tapers with a clean rag. Do not use an air gun, as it may make things worse.If chips piled up at pallet change collapse and get caught in the taper, a pallet seating fault appears (Makino). Haas checks the optional APC at the same interval even on a vertical machine. Greasing the plungers is also weekly.^[11][24]

Monthly

Inspect and lubricate the telescopic covers (way covers)CommonWhat to checkTelescopic covers of each axisGuidelineNo damage or binding, and they extend and retract smoothly Hurco includes scratches and excessive wear of the covers in its daily check items.^[11][4]
Grease the ball screws and linear guides that have grease nipples (manually lubricated machines)CommonWhat to checkGrease nipples of each axisGuidelineHaas: monthly (weekly if cutting materials that absorb water). Makino: every 2000 hours or 1 year for manually lubricated machines. For automatically greased machines, watch for the cartridge-level and pressure-drop warnings.ProcedurePlace the grease gun tip squarely on the nipple (Makino).Running with insufficient lubrication rapidly accelerates wear of parts and lowers machining accuracy (Makino). The interval differs greatly by machine (see also the lubrication points table).^[11][25][4]
Check the pressure of the spindle head counterbalance (hydraulic or pneumatic)CommonWhat to checkPressure gauge of the Z-axis (spindle head) balance cylinderGuidelineThe specified pressure for each model^[11](1 source, for reference)
Check the oil level of the spindle gearbox (geared spindles)CommonWhat to checkOil gauge on the spindle gearboxGuidelineWithin range. Replace annually (Haas).^[11](1 source, for reference)
Check limit switches and dogs for damage and tightnessCommonWhat to checkLimit switches and dogs of each axisGuidelineNo looseness, damage, or dirt. Tighten loose ones to the specified torque with a hex key.Parts that serve as the reference for stroke ends and the home position^[4](1 source, for reference)
Check wiring and connectors outside the machine for fraying, cracks, and loosenessCommonWhat to checkConduits, connectors, cablesGuidelineNo fraying, cracks, or looseness^[4](1 source, for reference)
Check the oil level and oil color in the spindle lubrication tankCommonWhat to checkSpindle lubrication tank (oil-air, jet, etc.)GuidelineHaas: oil level monthly, spindle lubrication test every 6 months. Makino: spindle lubricating oil and cooling oil level daily. A brown color comes from oxidation of the additives and is not a problem, but if there is marked discoloration or cloudiness, replace the oil instead of topping it up.Continuing to use discolored or cloudy oil stops the machine with a clogged-filter alarm (Makino). The interval differs by machine (Haas monthly, Makino daily).^[11][3]

3 months

Check the oil level of the ATC (arm, cam box)CommonWhat to checkOil cup and round sight gauge of the tool changerGuidelineHurco: the middle of the sight gauge. If low, top up with ISO VG150–220 (every 500 hours). Haas: check the cam box oil level of side-mount changers every 3 months. Replacement: Hurco annually (2000 hours; sooner if it turns dark); Haas oil type Mobil 1 75W-90^[4][11]
Inspect and replace the pneumatic filter element and drainCommonWhat to checkFRL unit (filter, regulator, lubricator), auto drainGuidelineNo clogging or discoloration of the element. No water or oil mixed in the drain.ProcedureReplace only after turning the power off and releasing the pressure in the unit.Continuing to use a dirty element lets moisture, oil, and sludge pass through, causing malfunction of air cylinders and solenoid valves, scale reading errors, and rust (Makino). Hurco says to drain the line every 3 months. Makino says to follow the periodic maintenance manual for the replacement interval.^[4][26][7]
Measure ground resistanceCommonWhat to checkGround terminal inside the control cabinet (near the main switch)Guideline— (Hurco calls for a measurement but gives no value)^[4](1 source, for reference)
Inspect and replace the through-spindle coolant (CTS/TSC) filterCommonWhat to checkPump filter of the through-spindle coolantGuidelineHurco: inspect weekly and clean if needed, replace every 3 months. Haas: every 6 months, clean the pump filter and check for hose cracks and the operation of the auto-clean.^[4][11]

Every 6 months

Grease the chain, drum, and arm of the ATC magazineCommonWhat to checkMagazine chain, between the pockets of a drum magazine, nipples of the tool change arm, roller track of the carouselGuidelineHurco: every 6 months (1000 hours), apply a thin layer of NLGI 1 to the chain and 5 cc of NLGI 2 to the nipples. Do not let grease build up. Haas: for side-mount changers, every 6 months clean and lubricate the pocket plungers and the track, and annually grease the cam. For umbrella changers, grease the guide rail and extractor fingers monthly.The chain section of the ATC magazine is lubricated with grease (Makino).^[4][11][25]
Check the machine levelCommonWhat to checkTable top surfaceGuidelineHurco: place a precision level with 0.020 mm/m resolution in the X direction, then the Y direction, and read at nine table positions. No 3-axis machine may exceed 0.020 mm/m (if it does, call service). Monthly for the first 6 months after installation, every 6 months after that.Level is the foundation of all accuracy and changes with things like foundation settlement (Okuma America). Okuma America includes it in the annual check items. Haas's paid inspection (HFO) also includes a level check.^[4][15][27]
Check the axis lubrication, air, and auxiliary filter hoses for cracksCommonWhat to checkLubrication piping, air hoses, coolant hosesGuidelineNo cracks, kinks, or leaks^[11](1 source, for reference)
Run an operation test of the axis lubrication and spindle lubricationCommonWhat to checkAutomatic oiler and spindle lubrication unitGuidelineOil is delivered as described in the manufacturer's test procedure (Haas).Too much or too little oil, or the wrong type, in the spindle bearings causes spindle overheating (Haas's spindle diagnostic table).^[11][21](1 source, for reference)
Clean the coolant tank completely and replace the fluidCommonWhat to checkCoolant tank (dirty tank and clean tank), mesh filterGuidelineRemove sludge, chips, and tramp oil from the bottom. Haas replaces the fluid and filter every 6 months, Hurco every 3 months.ProcedureFill with fresh fluid only after cleaning the tank. When diluting, add water first, then the concentrate (the other way around tends to gel). Do not top up with water alone (Makino).Neglecting cleaning lets sludge harden, causing blockage of the return path, pump failure, tool breakage, and holes in the tank from electrolytic corrosion (Makino).^{[11][10][19][22][4]}
Check the batteries and calibration of the touch probe and tool length measuring deviceCommonWhat to checkWorkpiece probe and tool setterGuidelineBattery level, calibration values (Haas)^[11](1 source, for reference)
Clean the condenser and filter of the oil controller (spindle chiller)CommonWhat to checkAir filter and condenser fins of the oil controllerGuidelineNo dust. Hurco's spindle chiller: inspect the tank air filter and water filter weekly, and wash the tank and replace the fluid annually.ProcedureTurn the power off. Vacuum the filter, or if very dirty, wash it with water and neutral detergent and dry it. Clean the fins with a brush. Do not spray water on the unit itself (electric shock or failure). Wear protective gloves so the fin edges do not cut your hands (Makino).If left dirty, the load on it makes the life of the oil controller extremely short (Makino). Makino gives no interval ("periodically"); "6 months" is used here for convenience.^[28][4]

Annual

Replace the hydraulic oil and filter, and clean the cooler and strainer of the hydraulic unitCommonWhat to checkHydraulic unit (tank, suction strainer, fan cooler)GuidelineMakino: every 2000 hours, clean the fan cooler, wash the suction strainer, and replace the hydraulic oil. Hurco: replace the hydraulic oil and filter annually (2000 hours), and check the level every 3 months. Yuken decides by testing the oil's properties.ProcedureTurn the power off and attach a warning tag. Wash the strainer with kerosene or diesel fuel (do not use thinners or compressed air, per Makino's caution). Do not mix oils of different brands.Continuing to use old hydraulic oil leads to spindle clamp faults and ATC malfunction. A clogged cooler raises the oil temperature, and a clogged strainer lowers the pressure (Makino). The HPU of Haas horizontal machines with a pallet pool: change the oil every 3 years. Hurco checks daily that the hydraulic pressure is 40–50 bar.^{[30][4][31][32]}
Check the parts of the tool pockets (springs, plungers, fingers) for wearCommonWhat to checkTool pockets of the magazineGuidelineReplace any that are worn or damaged (Haas: annually for side-mount changers)Worn springs, plungers, and fingers let tools fall out of the magazine (Haas's diagnostic table).^[11][33][34](1 source, for reference)
Clean the automatic lubrication tank and suction filterCommonWhat to checkTank, suction filter, and filler port filter of the slideway lubrication (axis lubrication)GuidelineHurco: annually (2000 hours) clean the tank and suction filter, and check the filler port filter screen monthly.^[4](1 source, for reference)
Replace the batteries (absolute encoder and NC memory backup)CommonWhat to checkBatteries for the absolute pulse coder (absolute position of each axis) and for the memory of the NC unit and panelGuidelineMakino: for absolute position, every 2000 hours of use or 1 year; for NC memory, every 1 year; both before a long holiday and whenever a low-voltage alarm appears. Brother: if not replaced in over a year, replace before a long shutdown.ProcedureReplace the absolute position battery with the NC power on and all machine motion stopped (if you turn the power off and remove it, the position data is lost = Makino, Brother). The NC memory battery procedure differs by model; in Makino's example, replace it within the time limit (30 minutes or the like) and save the SRAM contents beforehand.When it runs out, the home position (machine coordinates) of each axis is lost and manual homing is needed, and the NC memory contents are lost too. If the power is turned off with low voltage and left for a week, the memory is erased (Makino). Seiko Instruments (grinding machine maintenance news) gives a battery life of 5 years and advises replacing by the year of manufacture on the side of the unit (differs by model and use).^{[35][36][37][38][39][40]}
Replace the oil in the spindle gearbox and ATCCommonWhat to checkGearbox of a geared spindle, ATC transmissionGuidelineHaas: gearbox oil annually (for the No. 50 16DP-C type, also clean the pump suction screen every 6 months). Hurco: ATC oil annually (2000 hours; sooner if it turns dark).^[11][4]

Other (as needed, first time, etc.)

Visually check the drum filter and backwash of the lift-up chip conveyorCommonPeriodicWhat to checkDrum unit in the coolant tankGuidelineNo chips clinging around the drum. Fluid comes out of the cleaning nozzles inside.Clogging makes the dirty tank overflow, and a torn filter clogs the pump suction (Makino). Makino says "visually, periodically" (it does not say daily). Replace the drum filter annually.^[29](1 source, for reference)
Replace the polycarbonate windows of the doorsCommon3 yearsWhat to checkFront and side door windowsGuidelineWithin 3 years (depends on usage and how much cutting fluid reaches them)Cutting fluid, lubricants, and ultraviolet light reduce impact resistance by up to 10% per year. Some windows are marked with a manufacture or installation date.^[4](1 source, for reference)
Preparation before a long shutdownCommonBefore a long shutdownWhat to checkWhole machineGuidelineBrother: (1) grease the X, Y, and Z axes and run them through the full stroke about 3 times; (2) remove the holder from the spindle; (3) save programs and data to USB or a PC; (4) apply rust-preventive oil or grease to the table and fixtures; (5) replace the batteries; (6) park the axes at a fixed position that makes it easy to re-establish home, and turn the power off.Prevents loss of the home position, rust, and holders seizing during the shutdown. Hurco says to add a rust inhibitor to the automatic oiler if the machine will be stopped for 30 days or more. Haas also says it is better to remove the holder from the spindle when not in use.^{[39][4][8][35]}
Start-up after a long shutdownCommonAfter a long shutdownWhat to checkWhole machine, air supplyGuidelineBrother: run the full stroke about 3 times at low speed, break in the spindle (5 minutes each at 500 min⁻¹, then 1000, 2000, 4000, 6000 and so on up to the maximum), stir the coolant and check its concentration and pH, and check that the spindle motor and control cabinet fans are running. Hurco: for a spindle that has been stopped more than 30 days, run a break-in (bearing temperature 55°C or less; if exceeded, stop and let it cool, then start again from that speed). After a long stop or an oil change, operate the automatic oiler by hand before turning the power on.ProcedureMakino: after starting the compressor, open the machine-side regulator little by little from "closed" (applying full pressure at once can crack the regulator bowl or break the auto drain). When the room is cold, the lubricating oil and coolant get too cold and trigger alarms, so check the room temperature before turning the power on.Sudden high-speed movement causes damage. After a shutdown, faults such as air leaks from a cracked auto drain on the air dryer and a stopped radiator fan are common (Makino).^{[39][4][5][23]}

📚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.