Grinding machine inspection checklist (pre-shift, daily, weekly, monthly, annual) and maintenance

Daily (including before start of shift)

Before starting the day's work, run the wheel for at least 1 minuteCommonBefore start of shiftWhat to checkGrinding wheel and wheel spindleGuidelineRun for at least 1 minute with no abnormal vibration, noise or runout. After changing a wheel, at least 3 minutes (the trial run after a change is a separate item)ProcedureClose the guard before turning it on. During the trial run, do not stand in front of the wheel in its direction of rotation (the direction fragments fly) (Noritake)Required by Article 118 of the Industrial Safety and Health Regulations (Japan). There is a fatal accident in which a wheel burst at a workplace that did not do trial runs (case from the Ministry of Health, Labour and Welfare (MHLW))^[1][2][3][4]
Check the wheel for cracks, chips and loose mountingCommonBefore start of shiftWhat to checkWheel periphery and sides, boundary with the flangeGuidelineNo cracks or chips. Do not use a wheel that has been hit or dropped, or one that shows an abnormality in inspectionA damaged wheel can break and fly apart while rotating. UNITED GRINDING also lists wheel runout, mounting and cutting ability as inspection items. The visual and ring-test inspection when changing a wheel is covered in the wheel care items^[2][5][6]
Confirm the wheel guard (cover) is in place and closedCommonBefore start of shiftWhat to checkWheel guard, guard door and removable side plateGuidelineThe guard is properly fitted and closed. No deformation, cracks, or holes drilled that weaken it. The guard carries a marking for the maximum operating speed, thickness and diameter of wheels it can be used withThe guard is the only thing that catches fragments when a wheel breaks. In one case on a CNC cylindrical grinder, the guard was open to check the contact during dressing and fragments of a burst wheel hit the operator (MHLW). A guard is required by Article 117 of the Industrial Safety and Health Regulations (Japan), except for wheels under 50 mm in diameter. The Structural Standard for Grinding Machines (Japan) exempts internal grinders from the guard provisions. Do not turn the wheel before the guard is fitted (Noritake)^[1][7][2][6]
Check the air pressure and the hydraulic fluid level (hydraulic unit)CommonBefore start of shiftWhat to checkPressure gauge of the pneumatic unit, oil level gauge of the hydraulic tankGuidelineThe specified pressure for each machine. The oil level is near the reference levelWhen the oil level drops, bubbles form and the oil temperature rises, leading to oil degradation and failure (Yuken). UNITED GRINDING includes air pressure, the water tank and the hydraulic oil level in its 10-minute daily check^[5][8]
Check the amount and condition of the grinding fluid (concentration, discoloration, smell)CommonBefore start of shiftWhat to checkCoolant tankGuidelineThe level is within the specification. For water-soluble fluid, the concentration is within the recommended range, with no discoloration or rotten smellProcedureMeasure the concentration with a handheld refractometer. When it drops, add fresh fluid at the same or a slightly weaker dilution. Managing the dilution ratio of the make-up fluid carefully is what works best (Noritake)Grinding fluid cools the grinding point, lubricates it and flushes away swarf. Low concentration causes chatter and wheel glazing (JTEKT). For general management of grinding fluid (concentration, pH, spoilage), see also the common section of equipment maintenance^[5][9][10]
Check that the grinding fluid nozzle points at the grinding pointCommonBefore start of shiftWhat to checkGrinding fluid nozzleGuidelineThe fluid hits the grinding point (where the wheel meets the workpiece) in a solid stream that does not entrain airAccording to UNITED GRINDING, even when things go well only about 10% of the fluid reaches the grinding point. If the nozzle is misaimed, cooling and lubrication fall short, causing burn and chatter. An SME article (by a Norton engineer) says to match the fluid flow velocity to the wheel peripheral speed and, for conditions that have not been tested, to start at 25 gallons per minute per inch of width^{[5][11][10][12]}
Clean the magnetic chuck surface and confirm that the workpiece is held securelyFlat surfaceBefore start of shiftWhat to checkMagnetic chuck holding surface, workpieceGuidelineNo chips, burrs or scratches on the holding surface. Place the workpiece so it spans the N and S poles, across the separatorIf the hold is weak, the workpiece shifts during grinding and a large force acts on the wheel, which can break it. In one surface grinder case, stands held by magnets shifted and the wheel burst (MHLW). Kanetec says workpieces about 2–4 times the pole pitch in thickness hold best, and the edges of the holding surface need to be at least 3 times the pitch^[13][14][15]
Warm up the machine and start machining once dimensions are stableCommonBefore start of shiftWhat to checkWheel spindle, table and feed axes, grinding fluidGuidelineFollow the machine's specified warm-up time and warm-up programDimensions of a grinder change with machine thermal displacement (the headstock and bed move with temperature) and with workpiece expansion from grinding heat (JTEKT). JTEKT presents a model that shortened warm-up time with a cover that keeps grinding fluid heat away from the bed and with cooling of the wheel spindle bearing oil. UNITED GRINDING gives a difference between grinding fluid and room temperature of within ±1°C as ideal^[16][17][18]
Check that the door interlocks and emergency stop workCommonDailyWhat to checkMachine door and cover interlocks, emergency stop buttonGuidelineOpening a door stops hazardous motion or keeps it from starting. The emergency stop halts the wheel spindle and the feedsJIS B 6033 (safety of grinding machines) treats disabling an interlock so the operator can see better as "reasonably foreseeable misuse". Article 29 of the Industrial Safety and Health Regulations (Japan) prohibits removing safety devices or making them ineffective^[5][19][1]
Check the way covers (telescopic covers, bellows) for cracks or holesCommonDailyWhat to checkWay covers of the table, saddle and wheelheadGuidelineNo cracks, holes or curlingThese covers protect the ways from grinding fluid and grinding swarf, so repair cracks or holes early. UNITED GRINDING includes this item in its 10-minute daily check^[5](1 source, for reference)
Check the wheel spindle for any change in sound, temperature or vibrationCommonDailyWhat to checkWheel spindle, wheelheadGuidelineNo increase in abnormal noise, heat or vibration compared with usualLoss of wheel spindle rotational accuracy shows up as worse roundness, waviness and poorer surface finish (JTEKT). Running it unbalanced lets vibration reach the bearings and eventually damages the machine itself (Marposs). UNITED GRINDING's periodic inspection compares operating temperature and vibration with their tolerances. JTEKT includes "signs of abnormal noise, heat and vibration" in its checklist for deciding on equipment replacement^[17][20][21]
Check the table and feeds for sticking, play or abnormal noiseCommonDailyWhat to checkFeeds of the table (left-right), saddle (front-back) and wheelhead (up-down)GuidelineMoves smoothly even at low speed (no stick-slip, the repeated sticking and slipping). No large shock at reversalWhen the ball screw, support bearings and ways that drive the table deteriorate, defects such as poor straightness, roundness, surface finish and concentricity, and dimensional scatter, become likely (Seiko Instruments). Accuracy inspection standards such as JIS B 6213 assume that the running test for vibration, abnormal noise and stick-slip is done before the accuracy inspection^[22][23][24]
Check the dresser tip and mountingCommonDailyWhat to checkTip of single-point and multi-point dressers, dresser holderGuidelineNo cracks in the diamond. The tip is not worn flat. The holder is not loose. The shank is not projecting too farA dresser with a flat tip generates heat, which can crack the diamond, and the wheel face also glazes and cuts worse (Noritake). Dresser heat and wear can also cause feed marks (UNITED GRINDING)^[25][9][26]
Clean inside the machine at the end of the shiftCommonDailyWhat to checkInside the machine, around the table, covers, around proximity sensors, windowsGuidelineNo grinding swarf or sludge built up. No swarf sitting on the proximity sensorsCompacted grinding swarf can jam moving parts and require disassembly and cleaning (Seiko Instruments). Swarf on a sensor causes malfunction. UNITED GRINDING says to clean the machine at the end of each day's work^[5][27][28]

Monthly

Clean or replace the hydraulic filtersCommonWhat to checkHydraulic unit filters (suction, return, line)GuidelineIf there is a clogging indicator, follow it. If there is no indicator, clean or replace about once a month (Yuken)ProcedureWhen changing the filter, always stop the pump and release the residual pressure in the lines and equipment firstDirty hydraulic oil leads to pump failure and shorter life. Yuken's general hydraulic unit specifies a contamination level within NAS class 10 (18/15 in ISO 4406)^[8][29]

Annual

Carry out the voluntary inspection of local exhaust ventilation and dust collectors (if installed as a dust countermeasure)CommonWhat to checkHoods, ducts, fans, belts, dust collectorGuidelineWear, corrosion and dents in hoods, ducts and fans; dust accumulation in the ducts and exhaust fan; loose connections; belt condition; intake and exhaust capacityThe Ordinance on Prevention of Dust Hazards (Japan), Article 17, requires a periodic voluntary inspection at least once every year. Keep the records for 3 years (Article 18). Inspect before first use and after disassembly, modification or repair (Article 19)^[40](1 source, for reference)

Other (as needed, first time, etc.)

Remove sludge from the coolant tank and settling tankCommonPeriodicWhat to checkCoolant tank, settling tank, chip conveyorGuidelineNo sludge built up. Not much tramp oil floating on the fluid (way oil, etc.)Letting sludge build up in the settling tank causes poor surface finish (UNITED GRINDING). Dirty grinding fluid causes feed marks and scratches (JTEKT). If the fluid is discolored, smells rotten, has a low pH or has a large buildup of sludge, replace it. When changing it, also remove dirt from the tank, pump, piping and the back of the wheel guard (Noritake)^[5][9][30]
Check that the grinding fluid filtration equipment (magnetic separator, paper filter, etc.) is workingCommonPeriodicWhat to checkMagnetic separator, paper filter, filtration unit dischargeGuidelineSludge is being collected and clean fluid is returning to the tankWhen particles floating in the fluid are pressed into the grinding point, short comma-shaped scratches appear at random (UNITED GRINDING). Noritake recommends a high-capacity magnetic separator for individual tanks. No primary source was found that gives replacement intervals for parts (scrapers, rollers, filter paper, etc.). Follow the equipment's instruction manual^{[9][18][26][30]}
Check that temperature control of the grinding fluid and hydraulic oil is workingCommonPeriodicWhat to checkCoolant chiller (cooling unit), hydraulic oil temperature controllerGuidelineThe maker's recommended temperature. A difference of within ±1°C between grinding fluid and room temperature is ideal (UNITED GRINDING)When the temperature changes, workpiece dimensions change too. Grinding at the micron level requires keeping the temperature constant. Okamoto's US subsidiary includes a hydraulic oil temperature controller as standard on its column grinders^[18][5][31]
Test the hydraulic oil properties and drain water from the tankCommonPeriodicWhat to checkHydraulic tank (reservoir) drain, hydraulic oilGuidelineGuideline for changing oil in Yuken's general hydraulic unit: replace when any one of these applies: change in kinematic viscosity at 40°C of ±10%, change in total acid number of 0.5–1.0 mgKOH/g, or water content of 0.2 vol% or moreProcedureDrain water about once a month, while the machine is stopped. Test the oil properties every 3 months for the first half year, then every 6 months (Yuken). When replacing, drain the old oil completely, clean the tank, then fill with the same brandMost hydraulic equipment failures and malfunctions come from poor hydraulic oil management (Yuken). Seiko Instruments also strongly recommends servicing the hydrostatic blocks (or replacing them with serviced ones) on machines where the hydraulic oil and filters are being changed for the first time in a long while. The replacement interval for each grinder model is in the instruction manual^[8][29]
Check the oil output (flow rate) of the hydrostatic ways and hydrostatic bearingsCommonPeriodicWhat to checkHydrostatic blocks (hydrostatic parts of the table, wheelhead and spindle)GuidelineNot just pressure; the flow also comes out as specifiedWithout servicing, the flow changes even when the pressure is normal, and oil output from the hydrostatic block gets worse (clogging). Then machining accuracy falls, and in the worst case the table moves without fully floating and seizes (Seiko Instruments). Large machines and grinders often use hydrostatic ways, which have low friction and no stick-slip (ENEOS). JTEKT's cylindrical grinders use bearings that combine hydrostatic and hydrodynamic action^[29][23][17]
Clean the control cabinet fans, filters and heat exchanger, and check that they are runningCommonPeriodicWhat to checkBox fan and filter on the control cabinet door, fans inside the cabinet, intake of the heat exchanger (cooling unit)GuidelineFilters are not clogged. Fans are running. The temperature of electrical parts in the cabinet is below 55°C (UNITED GRINDING's inspection criterion)The life of electrical parts (especially electrolytic capacitors) is said to halve for every 10°C rise in ambient temperature (Seiko Instruments). A single fan failure can overheat capacitors and burn out the CNC unit (UNITED GRINDING). Seiko Instruments recommends doing this before summer and before long holidays^{[32][33][34][28][35]}
Replace the CNC and servo amplifier batteries before they expireCommonPeriodicWhat to checkBatteries of the servo amplifiers and CNC in the control cabinetGuidelineOn Seiko Instruments machines, battery life is 5 years (the year of manufacture is printed on the side of the unit)ProcedureReplace with the power on (UNITED GRINDING). If you do not remember when it was last replaced, replace it before a long shutdownWhen the voltage drops, a "battery low" warning appears; when it drops further, the home position data is lost and the machining data has to be re-entered^{[36][27][37][35]}
Check and clean the flexible metal conduits (flexible metal tubes protecting wiring and piping) for fastening and cracksCommonPeriodicWhat to checkFlexible metal conduits connected to moving partsGuidelineProperly fastened. No cracks or breaksProcedureWear gloves when checking, so you do not cut your hands on broken edgesWhen a flexible metal conduit breaks, the wiring inside is exposed to oil such as grinding fluid. Clean them regularly to keep them flexible (Seiko Instruments)^[38](1 source, for reference)
Have the maker's periodic inspection done (geometric accuracy, vibration, temperature, electrical, safety devices)CommonPeriodicWhat to checkWhole machineGuidelineUNITED GRINDING recommends one every 2080 operating hours (one year at one shift a day, five days a week; every six months at two shifts). It says the inspection interval can be chosen from 4, 6, 12, 18 or 24 monthsMissing early signs of wear leads to long, costly downtime. The inspection starts with checking geometric accuracy and alignment, and goes on to operating temperature and vibration, electrical and safety devices, and replacement of consumable parts and oil (UNITED GRINDING). Okamoto offers on-site static accuracy inspection, machine correction and designated oil changes as after-sales services^[21][35][39]
Inspect the mist collector (oil mist dust collector)CommonPeriodicWhat to checkMist collector, filtersGuidelineSuction has not dropped. Filters are not cloggedAuxiliary equipment such as the mist collector also strongly affects the machine's condition if not maintained, and can cause damage (UNITED GRINDING). No primary source was found that gives a filter replacement interval^[5](1 source, for reference)
Check the centers, center holes and tailstock pressureCylinderAt setupWhat to checkHeadstock and tailstock centers, workpiece center holes, tailstockGuidelineNo scratches or foreign matter in the center holes. The pressure is correctPoor center hole accuracy or trapped foreign matter causes runout in rotation and poor roundness. If the pressure is wrong, the workpiece deflects (JTEKT). Noritake lists regrinding the center holes as a countermeasure for poor roundness^[41][17][42]
Set the steady rest position and contact allowanceCylinderAt setupWhat to checkSteady restGuidelineIt supports a low-rigidity workpiece. The contact allowance is correctInsufficient support causes chatter (UNITED GRINDING). The position of the steady rest also affects cylindricity (Noritake)^[26][42][41]
Check that the high-frequency spindle for internal grinding is used under the specified conditionsInternalAt setupWhat to checkInternal grinding spindle (high-frequency spindle) power supply (inverter), lubrication air and oil, cooling waterGuidelineMatches the spindle's specification sheet: rated voltage and frequency, lubrication method, air pressure, air flow, lubricating oil and oil quantity, cooling water flow and temperatureUsing a voltage different from the specification prevents full performance, causes trouble, and greatly shortens spindle life (Seiko Instruments gives the example of running a spindle rated at 230 V on 200 V). If it is not used as specified, repairs can be charged for even within the warranty period (Seiko Instruments)^[43](1 source, for reference)
Carry out the procedure before a long shutdownCommonBefore a long shutdownWhat to checkWhole machineGuidelineUNITED GRINDING's complete shutdown procedure: (1) drain the grinding fluid and let the fluid remaining in the piping out (especially water-soluble); (2) spin the wheel for at least 20 minutes to dry it, then remove it (ordinary wheels); (3) clean the tank and conveyor and spray on rust preventive; (4) clean and rust-proof bare metal surfaces, spindle ends and flanges, and the headstock and tailstock tapers; (5) wipe sludge off the covers and windows; (6) send each axis to home; (7) replace the batteries with the power on; (8) back up all machine data, CNC data and machining programsAfter a long shutdown, ball screws can rust and grinding swarf can harden, causing stops or overload errors when the machine is moved (Seiko Instruments; take particular care with machines using water-soluble grinding fluid). Seiko Instruments also recommends cleaning inside the machine, checking the batteries and backing up programs before the shutdown^{[37][27][44][34]}
Run the machine from time to time while it is idle, and circulate the grinding fluidCommonDuring a long shutdownWhat to checkEach axis and the wheel spindle, grinding fluid tankGuidelineSeiko Instruments: warm up or run dry for one day (about 8 hours) per week. UNITED GRINDING (for a partial shutdown): run a warm-up cycle of each axis and the spindle for 1 hour dailyThis spreads lubricating oil over moving surfaces and prevents swarf from sticking. It also serves to charge devices that have no battery (Seiko Instruments). When resting without draining the grinding fluid, keep the circulation pump or aeration pump running so the fluid does not rot (UNITED GRINDING, water-soluble)^[27][37]
After a shutdown, move the machine slowly and check for abnormalities before machiningCommonAfter a long shutdownWhat to checkEach feed axis, wheel spindle, control unitGuidelineMoves at low speed with no overload or stop. No battery-low or lost-home-position warning. Trial run of at least 3 minutes (when the wheel has been changed) or at least 1 minute (before the day's work)If a machine using water-soluble grinding fluid is stopped for a long time, abrasive dust around the moving parts can harden and increase the drive load, causing a servo motor "overload" alarm (Seiko Instruments)^[36][44][1]

📚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.