Machining center troubleshooting quick reference (spindle heat, abnormal noise, chatter, dimensional drift)

Spindle runs hotCommon

Haas: after the lubrication test and warm-up, install a dummy tool and run a 40-minute test program; measure the temperature at the spindle front, which must not exceed 60 °C. Hurco: during break-in, bearing-area temperature 55 °C or less (50 °C for an electric spindle that has been stopped for 3 months or more)^[1][2]

Likely cause	What to check	Action
Too much or too little spindle lubricating oil, or the wrong oil type	Oil level in the spindle lubrication tank, clogging of the lubrication pump, whether it is the specified oil	Switch to the specified oil and correct the lubrication amount. Look for leaks in piping and fittings^[1][2][3]
The spindle front cap has shifted from a crash and is rubbing the spindle	Insert a 0.025 mm shim around the front cap and check the clearance all the way around	Loosen the cap, center it, and tighten it again^[1](1 source, for reference)
Dirty condenser or filter in the spindle chiller (oil controller / chiller), or low coolant	Dust on the filter and fins; chiller fluid level	Clean and refill. Makino says that neglecting cleaning drastically shortens the life of the oil controller.^[4][2]
Faulty bearing preload, clearance, or mounting; damage	Whether there is a high-pitched sound; vibration measurement	Ask the manufacturer to diagnose and repair^[5][6]

Abnormal noise, vibration, or chatter from the spindleCommon

Likely cause	What to check	Action
Wear or damage of the spindle drive belt, or of the encoder pulley and belt (belt-driven spindles)	Fraying, stretching, or missing teeth on the belt; wear of the pulley	Replace or adjust the tension (after turning off the power and locking it out)^[1](1 source, for reference)
Imbalance of the tool (holder + cutter)	Rotation speed and balance grade (Hurco: G6.3 up to 12000 min⁻¹, G2.5 above)	Balance the tool with it assembled. If it cannot be balanced, replace it^[1][2]
Tool stickout is long	Ratio of stickout to diameter	Use a shorter tool (Haas: stickout no more than 3 times the diameter). Reduce the depth of cut^[1][7]
Insufficient drawbar force, or fretting of the holder	Measure the pull-in force. Check the holder taper for rub marks (fretting)	If the disc springs are damaged, replace the drawbar (the whole spindle unit for built-in spindles)^[1][8](1 source, for reference)
Spindle bearing damage	Vibration analysis	Ask the manufacturer to diagnose and repair^[1][5]
The fixture does not support the workpiece enough	Setup	Strengthen the fixture. Reduce the cutting load^[1](1 source, for reference)

Tool (holder) is hard to remove from the spindle, or comes out with a popCommon

Likely cause	What to check	Action
A tool was left in the spindle while the machine was stopped (a cold holder put into a warm spindle sticks as the temperatures equalize)	Whether tools are removed at the end of the day	When not in use, remove the holder from the spindle^[1][9]
No grease on the pull stud	Pull stud surface	Apply a thin coat of grease (Haas monthly, weekly with TSC; Hurco monthly)^[1][10][2]
Dirt or scratches on the holder and spindle taper	Dirt and dents on the taper	Clean it, and do not use a damaged holder^[8][1](1 source, for reference)
Insufficient air pressure or flow to the tool release piston (TRP), or a shifted TRP sensor	TRP pressure (Haas 6.21 bar); whether the pressure drop during a tool change is within 0.7 bar	Improve the supply air; adjust the sensor^[8][11](1 source, for reference)
The drawbar retention balls are dry	—	Grease the retention balls^[8](1 source, for reference)
A coolant containing paraffin-based components is being used for through-spindle coolant	Type of coolant	Try a different coolant^[1](1 source, for reference)

Tools fall in the ATC / magazineCommon

Likely cause	What to check	Action
Wear or damage of the pocket fingers, springs, or plungers	Wear of pocket parts	Reassemble the pocket or replace parts^[12][11](1 source, for reference)
The pull stud or holder does not match the machine's specification	Pull stud shape	Replace with the shape the machine specifies^[12][11](1 source, for reference)
Tool is too heavy or too long, or the pocket moves too fast with a heavy tool	Tool weight and length versus the magazine's allowance	Bring it within the allowance. Heavy-tool setting (Haas H flag) or deceleration part^[12][11](1 source, for reference)
The holder falls before the ATC grips it: insufficient clamp force, or a wrong TRP precharge pressure setting	Pull-in force; precharge air pressure	Adjust or repair^[8](1 source, for reference)

Tool change stops partway, or an ATC alarm appearsCommon

Likely cause	What to check	Action
Chips are interfering with the proximity sensors, guide rails, or pocket slides	Chips on the sensors, rails, and ATC shutter	Clean. Makino gives an example of an ATC shutter failure caused by leaving chips in place.^[12][11][13]
Insufficient air pressure or flow	Pressure gauge drop during a tool change (Haas: within 0.7 bar); source air pressure	Review the hose size and the compressor. The ATC arm and shutter are air-driven (Makino)^[11][14][15]
Spindle orientation (fixed-position stop) is off or weak	Orientation settings, belt tension, supply voltage, loose wiring	Reset the settings; tighten the wiring^[12](1 source, for reference)
Worn motor brushes, coolant intrusion, broken or poorly contacting cable, faulty relay	Motor voltage and resistance, brushes, cables (especially if the fault occurs during operation or is intermittent)	Clean or replace parts^[12](1 source, for reference)
Old hydraulic fluid has been used for too long (hydraulically driven ATC)	Hydraulic fluid change interval	Change the hydraulic fluid (Makino: 2000 hours)^[16](1 source, for reference)
The previous tool change was interrupted partway, or a tool change was attempted with the pocket down	State of the tool change at the interruption	Perform a manual tool-change recovery^[11](1 source, for reference)

Spindle clamp failure (tool is pulled out, or clamp alarm)Common

Likely cause	What to check	Action
Pull-in force dropped because of cracked or broken disc (Belleville) springs	Pull-in force (if it has dropped to about 50% of nominal, this is the fault)	Replace the drawbar (the whole unit for built-in spindles)^[8][17](1 source, for reference)
Old hydraulic fluid has been used for too long (machines that unclamp the tool hydraulically)	Condition of the hydraulic fluid and change interval	Change the hydraulic fluid^[16](1 source, for reference)
Not enough grease on the collet and sleeve of an HSK spindle	Greasing interval (Makino 500 hours)	Grease the collet. Tool seating and tool presence detection errors can also come from this.^[18](1 source, for reference)
Insufficient air capacity	Supply air volume and pressure	Meet the machine's required air supply^[8][1](1 source, for reference)

Feed-axis noise, position error, or worsening machining accuracyCommon

Likely cause	What to check	Action
A deteriorated or broken wiper let chips and coolant into the cover	Scratches, cracks, and gaps in the wiper; scratches on the cover	Replace the wiper (replace the cover too if the damage is large). Inspect the linear guides, ball screws, and wiring^[19][13][20]
Insufficient lubrication, or different oils or greases were mixed	Lubrication / greasing records; oil level	Lubricate with the specified oil. Do not mix oils or greases of different brands^[21][22][23]
Backlash (axial play of the ball screw)	Step in the ballbar trace	Adjust or compensate through the maker or distributor^[24][25]
Dirty air got into the scale (position detector) and caused read errors	Discoloration or clogging of the air filter; water or oil in the piping	Improve the air quality and replace the filter^[14][26](1 source, for reference)
The machine's level has drifted	Precision level	Re-level (Hurco: call service if it exceeds 0.020 mm/m)^[2][20]
A machine using water-soluble fluid was left stopped for a long time, and abrasive dust and sludge stuck to the moving parts and increased the load	Servo overload alarm	Warm up and run the machine dry periodically even while it is stopped (example from a Seiko Instruments grinder)^[27](1 source, for reference)

Lubrication / oil level alarm appearsCommon

Likely cause	What to check	Action
Low oil level or leak	Oil level gauge; oil puddles around the machine	Top up. If the level drops abnormally fast, suspect a leak or a fault and contact the maker^[28][2]
Clogged line filter in the spindle lubricating oil	Clogging indicator of the line filter	Replace the element (Makino recommends keeping spares). Do not top up discolored or cloudy oil; replace it^[29][30][31](1 source, for reference)
The automatic grease unit's cartridge is empty	"Low pressure" and "cartridge replacement required" warnings	Replace the cartridge^[21](1 source, for reference)
Dirty automatic lubrication tank or suction filter	Filter screen at the filler port (monthly)	Clean the tank and suction filter (once a year)^[2](1 source, for reference)

Coolant does not come out, overflows, or chips clogCommon

Likely cause	What to check	Action
Clogged drum filter of the lift-up conveyor, or the backwash nozzle is not discharging	Chips around the drum; backwash discharge	Clean out the chips, inspect the drum filter (replace it every year), and adjust the backwash volume^[32](1 source, for reference)
Sludge has built up and stuck in the tank	Tank bottom; mesh filter	Clean the tank (mobile sludge removal units also exist)^[33][34](1 source, for reference)
Clogged through-spindle coolant filter	Pump filter	Clean or replace^[35][2]
Tank is overfilled	Level gauge	Do not fill above the upper limit (returning fluid makes it overflow)^[36](1 source, for reference)
Foaming (high concentration, or soft dilution water)	Concentration; water quality	Correct the concentration^[34](1 source, for reference)

Dimensions differ between morning and afternoon, or drift during machining (thermal displacement)Common

Likely cause	What to check	Action
Temperature changes around the machine (outside air, direct sunlight, air-conditioning drafts)	Room temperature record; installation location	Stabilize the temperature. On machines with thermal displacement compensation, use that function^[37][38]
The machine has not been warmed up (heat generated by the machine itself, such as the spindle)	Whether the machine was warmed up at start-up or after stopping during setup	Warm up before machining or measuring^{[2][39][40][38]}

Home return request or home position lost alarm appears at power-onCommon

Likely cause	What to check	Action
The battery voltage of the absolute encoder (pulse coder) is low, or the battery is dead	Low-battery alarm history; replacement date	Replace the battery, and if the home position was lost, perform a manual home return (contact service if that is not possible)^[41][42][27]
The battery was removed with the power off	Replacement procedure	Replace it with the NC power on^[41][42]
The power was left off for a long time	Idle period	Before a long shutdown, replace the battery and position the axes where it is easy to re-establish the home position, then turn the power off^[42][9](1 source, for reference)

NC parameters or programs have disappearedCommon

Likely cause	What to check	Action
Low voltage in the NC memory backup battery	Battery alarm; replacement interval (Makino: every 1 year)	Replace it. Save the SRAM and programs before replacing. Brother advises saving the data to USB or a PC.^[43][44][42]

Air cylinder malfunction, scale read error, or air leakCommon

Likely cause	What to check	Action
Compressed air contains water, oil, or dirt	Water and oil in the drain; discoloration of piping; dirt on the quick-connect couplers; whether water or oil comes out of the air blow	Drain the compressor, replace filters, and review the piping (1/100 slope on the main line, branch lines taken from the top of the main, an automatic drain at the end)^[15][14][26](1 source, for reference)
Cracked cup or fitting on the air dryer's automatic drain (common after holidays)	Location of the air leak	Replace the cup. After starting the compressor, open the regulator slowly^[45][46](1 source, for reference)

Alarm or no movement after a long holidayCommon

Likely cause	What to check	Action
Room temperature is low, and the lubricating oil and coolant are too cold, triggering an oil controller alarm	Room temperature	Bring the room to the right temperature, then reset the alarm^[46](1 source, for reference)
The cooling fan of the control cabinet heat exchanger has stopped (dirt or failure)	Fan stop alarm	Clean or replace^[45](1 source, for reference)
Low battery / home position lost	Alarm	Replace the battery, adjust the home position^[27][9]

Pallet change gives a seating or clamp errorHorizontal

Likely cause	What to check	Action
Chips caught in the pallet-area taper or clamp switch	Taper cone, pallet-side taper, clamp switch	Clean with a rag (do not use an air gun). Haas lists this as a weekly cleaning item^[47][35]

Large tool runout or poor finished surfaceCommon

Likely cause	What to check	Action
Dirt on the spindle taper or holder	Taper surface	Clean (do not use an air gun)^[48][49][2]
Scratches on the holder or spindle taper	Dents; fretting	Do not use a damaged holder. Have the spindle taper repaired by the maker^[8][20]
Bearing preload is off (after all other checks have been done)	Spindle deflection test	Ask the maker^[1](1 source, for reference)

📚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.