Hurco CNC Fault Codes — Complete Troubleshooting Guide

Hurco CNC machines — the VM, VMX, TM, and TMX series — run the WinMax control system. When a fault fires, WinMax displays an error code, a descriptive text message, and in most cases, enough context to diagnose the problem on the machine floor without a service call. This guide covers the fault codes technicians encounter most often across the Hurco mill and lathe lines, how to read fault history, and what to do when the alarm screen isn’t telling you the whole story.

Jump to Section

• How WinMax Fault Codes Work
• Accessing Fault History
• Servo and Drive Fault Codes
• Axis Fault Codes
• Spindle Fault Codes
• ATC / Tool Changer Fault Codes
• Encoder Fault Codes
• E-Stop Fault Codes
• Coolant Fault Codes
• Communication Error Codes
• Parameter Error Codes
• WinMax Error Code Reference Table
• Parts Reference Table

How WinMax Fault Codes Work

WinMax uses three parallel alarm systems that can fire simultaneously:

1. Numeric Error Codes (1–9999) — hardware-level faults from the motion controller, drives, and I/O. These appear in the Error Code field and are documented in the WinMax Help Center.
2. Text Error Messages — descriptive strings like “ATC FAULT – ATC DOOR DID NOT OPEN” that explain the fault in plain language.
3. NavErr Records — a diagnostic log capture that WinMax creates automatically on many fault conditions. NavErr files package the fault state, machine parameters, and I/O status into a compressed file that Hurco Service can analyze remotely. When calling Hurco support at 800-638-1849, having a NavErr ready dramatically speeds diagnosis.

On the machine, alarms display at the bottom of the WinMax screen. Multiple alarms can stack — clear from the bottom of the stack (most recent) upward. Clearing an alarm that has an unresolved root cause will result in the alarm returning on the next motion attempt.

Accessing Fault History

1. Press F10 (Setup) from the main WinMax screen, or navigate to Setup > Utilities > Log Files.
2. Select Active Error Listing to see current latched faults.
3. Select Active Status Listing for system state information.
4. To retrieve the full log: Setup > Utilities > Log Files > Retrieve Log and Diagnostic Files. This generates a .zip file that can be transferred via USB or network share.
5. For NavErr capture: Hurco service may ask you to go to Maintenance > NavErr and save the current diagnostic record.

Error entries include a timestamp, error code number, error text, and the axis or subsystem that reported the fault.

Servo and Drive Fault Codes

Servo drive faults on Hurco machines are generated by the Yaskawa or Bosch Rexroth servo amplifiers (depending on machine vintage) and reported through the WinMax motion controller. The WinMax error code maps to an underlying drive fault code.

Error 32 — Parameter Checksum Error

What it means: The servo drive’s internal parameter memory failed a checksum validation. The stored parameter set is corrupted.

Causes:

• Power loss during a parameter write operation
• Drive memory fault (internal flash/EEPROM degradation)
• Static discharge during drive service

Fix: Reload the servo drive parameters from backup. Contact Hurco service for the correct parameter set for your machine’s drive configuration. Do not attempt to manually edit servo parameters without the machine-specific parameter file.

Error 33 / 34 — Parameter Format Error

What it means: Drive parameters exist but are in an incorrect format — version mismatch between firmware and parameter file, or corrupted initialization.

Fix: Same as Error 32. Requires drive parameter reload. If the error persists after parameter reload, the drive may require firmware update or replacement.

Error 41 — Motor Parameter Checksum Error

What it means: The motor parameter table (motor-specific settings like rated current, encoder type, pole count) failed checksum.

Causes:

• Motor swapped without updating drive parameters
• Drive memory corruption

Fix: Re-initialize motor parameters. This requires Hurco’s machine-specific motor parameter file matching the installed servo motor. Verify motor nameplate against parameter set before loading.

Error 44 — Converter Parameter Checksum Error

What it means: The converter/regenerative unit (shared DC bus power supply on some machine configurations) has a parameter checksum fault.

Fix: Reload converter parameters. This is separate from the servo axis drive parameters. On machines with a common DC bus (VMX series and larger), the converter parameters control the regenerative braking and bus voltage management.

Error 48 — Main Circuit Detector Error

What it means: The servo drive cannot detect the main circuit power supply. The DC bus is not energizing properly.

Causes:

1. Main power contactor not closing (blown fuse, contactor coil fault, control voltage issue)
2. Main circuit fuses blown
3. AC input power problem (phase loss, low voltage)
4. Drive hardware fault (rectifier section)

Diagnosis:

• Check the main input fuses at the drive. Use a multimeter to verify continuity.
• Check control voltage (24 VDC typically) to the main contactor coil.
• Measure AC input voltage at the drive terminals — verify all three phases present and within tolerance (typically ±10% of rated).
• If power is confirmed and the error persists, suspect drive rectifier failure.

Error 64 / 66 — Parameter Setting / Combination Error

What it means: A servo drive parameter value is out of range (Error 64) or two parameter settings are mutually incompatible (Error 66).

Causes:

• Parameters loaded from a different machine type
• Manual parameter edit with an invalid value
• Firmware update changed valid parameter ranges

Fix: Restore factory default parameters for the drive, then reload the machine-specific parameter set. Do not clear to factory defaults without having the Hurco parameter backup for your machine.

Axis Fault Codes

Error 3866 — Converter AC Power Supply Open Phase

What it means: One phase of the AC input to the common DC bus converter is missing.

Causes:

1. Blown input fuse (most common)
2. Loose or failed wire at the input terminal block
3. Upstream circuit breaker tripped
4. Utility supply issue

Diagnosis:

1. Check the three-phase input at the converter unit — measure all three legs.
2. Inspect input fuses — visually and with a continuity tester.
3. Check the main circuit breaker for the machine.

Error 3868 / 3883 — Converter AC Power Supply Frequency Error / Detection Time Exceeded

What it means: The AC input frequency is out of tolerance, or the frequency detector took too long to lock on startup.

Causes:

• Poor power quality (generator power, UPS output, utility frequency instability)
• Intermittent phase loss causing detection loop failure
• Drive hardware fault in the frequency detection circuit

Fix: Verify supply frequency with a power quality meter. These faults are common when machines are moved and run on generator power during installation.

Error 3882 — Converter AC Power Supply Phase Sequence Error

What it means: The AC input phase sequence (rotation) does not match what the drive expects.

Fix: Swap any two of the three AC input phases at the machine main disconnect or input terminals. Power down completely before swapping phases.

Overtravel Fault — Axis Hardware/Software Limit

Display message: “AXIS OVERTRAVEL – [AXIS] POSITIVE LIMIT” or “NEGATIVE LIMIT”

What it means: An axis reached its hardware travel limit switch or exceeded its software travel limit in WinMax.

Causes:

• Program error — incorrect zero offset, wrong work coordinate
• Home position not established before running a program
• Limit switch fault — switch damaged or misaligned

Diagnosis:

1. If hardware limit: jog the axis in the opposite direction to clear the limit. If the machine won’t jog, use Maintenance > Jog Override to move off the limit switch.
2. If software limit: check the work coordinate system — verify G54/G55 offset and program zero location.
3. If the machine trips the limit repeatably at the same position without program error, inspect the limit switch and actuating cam.

Spindle Fault Codes

Spindle Drive Fault — No Load / Overload

Display message: “SPINDLE DRIVE FAULT” or “SPINDLE OVERLOAD”

What it means: The spindle drive (Hitachi, Yaskawa, or Mitsubishi depending on machine and vintage) reported an internal fault.

Causes (in order of frequency):

1. Cutting overload — aggressive depth of cut or feed rate for the material
2. Spindle bearing damage — increased drag causes overcurrent
3. Drive overtemperature — insufficient cabinet cooling
4. Tool holder or drawbar issue — tool not clamping correctly causes vibration and load spikes
5. Drive hardware fault — power component failure

Diagnosis:

1. Run the spindle at low RPM with no load — listen for bearing noise (rumble, grinding).
2. Check spindle drive cabinet temperature and cooling fan operation.
3. Check the spindle drive fault code on the drive’s own display (not just the WinMax message). The drive may show a sub-code (e.g., OC — overcurrent, OT — overheat, OV — overvoltage).
4. Inspect drawbar spring pack — worn springs cause tool pull issues and vibration.
5. Measure spindle motor resistance phase-to-phase — asymmetry indicates winding fault.

Error — Spindle Not At Speed / Spindle Orientation Fault

Display message: “SPINDLE NOT AT SPEED” or “SPINDLE ORIENTATION FAULT”

What it means: After a speed command, the spindle did not reach target RPM within the allowed time. Or the spindle failed to orient to the correct angle for a tool change.

Causes:

1. Encoder fault or loose encoder connector — feedback loss causes speed regulation failure
2. Spindle belt slipping or broken
3. Drive parameter mismatch after service
4. Spindle load too high to reach commanded speed

Fix:

• Check encoder connector seating and cable routing for damage.
• Inspect spindle belt tension and condition.
• If orientation-specific, check the orientation sensor and its target.

ATC / Tool Changer Fault Codes

ATC FAULT — ATC DOOR DID NOT OPEN

What it means: The ATC (Automatic Tool Changer) door failed to open within the timeout period. The door sensor did not confirm open state.

Causes (in order of frequency):

1. Loss of air pressure — the ATC door is pneumatically actuated
2. Debris blocking the door — chip accumulation on the door or mechanism
3. Solenoid valve fault — air valve for the door not actuating
4. Door sensor (proximity switch) fault — door opened but sensor not seeing it

Diagnosis:

1. Check machine air pressure at the regulator — should be 80–100 PSI (verify in Hurco documentation for your model).
2. Clean the ATC area thoroughly — chip accumulation in the door track is the most common cause on high-production machines.
3. Listen for the solenoid valve clicking when the door open command is sent.
4. Check the door proximity sensor with a multimeter — verify it switches when manually actuated.

Reset: Clear the alarm, ensure air pressure is correct, and retry. If persistent, enter the ATC maintenance mode (Setup > Maintenance > ATC) to manually step through the tool change sequence and identify the step where it fails.

ATC FAULT — X,Y AXES MOVE FAILED

What it means: During a tool change, the axes failed to move to the tool change position within the allowed time.

Causes:

1. Servo fault on X or Y axis during the move
2. Workpiece or fixture extending into the tool change path
3. Axes not homed before attempting a tool change

Fix: Verify axes are homed. Check for obstructions in the machine envelope. Check servo status for the affected axis.

ATC FAULT — TOOL NOT CLAMPED / UNCLAMPED

What it means: After a clamp or unclamp command, the drawbar sensor did not confirm the expected state.

Causes:

1. Drawbar spring pack worn — insufficient clamping force
2. Air pressure fault — unclamping uses pneumatic actuation; low air prevents unclamp
3. Drawbar sensor fault — sensor not detecting collet/tool holder position
4. Tool holder retention knob issue — worn or incorrect retention knob style

Diagnosis:

1. Check drawbar clamping force with a pull-stud force gauge. Minimum force varies by spindle taper but typically 1,500–2,500 lbf for CAT/BT 40.
2. Verify air pressure at the drawbar cylinder.
3. Inspect the proximity sensors at the drawbar — usually two sensors (clamped and unclamped positions).
4. Inspect pull studs for wear or wrong style.

Encoder Fault Codes

Error — Encoder Communication Error / Feedback Loss

Display message: “ENCODER FEEDBACK LOSS – [AXIS]” or “SERIAL ENCODER COMMUNICATION ERROR”

What it means: The motion controller lost communication with the rotary or linear encoder on the affected axis. This causes an immediate servo shutdown to prevent uncontrolled motion.

Causes (in order of frequency):

1. Encoder cable damage — kinked, pinched, or cut cable in a moving cable track
2. Connector fault — connector at motor end or drive end loose or contaminated
3. Encoder failure — internal encoder electronics damaged by shock, contamination, or age
4. Drive feedback card fault — encoder interface hardware on the servo drive

Diagnosis:

1. With the machine powered down, trace the encoder cable through the cable track. Look for kinks, abrasion, or crush damage.
2. Clean and reseat all encoder connectors. Check pins for corrosion or bent contacts.
3. Swap the encoder feedback cable with a known-good spare if available. If the fault moves to the new axis, the cable is the problem.
4. If fault persists with confirmed-good cabling, the encoder or drive interface card may need replacement.

Note on Hurco linear encoders: Some VMX and BX series machines use Heidenhain linear glass scales. These are sensitive to coolant contamination. Verify scale covers are intact and seals are not compromised if a linear scale machine starts throwing feedback errors.

E-Stop Fault Codes

E-STOP ACTIVATED

What it means: The emergency stop circuit is open. The machine has halted all motion and the servo drives have been disabled.

Causes:

1. E-stop button pressed (operator or pendant)
2. Safety door interlock open
3. Wiring fault in the E-stop safety chain
4. Safety relay module fault
5. External device (robot, gantry) activating the E-stop input

Diagnosis:

1. Verify all E-stop buttons are released (twist and pull to release on most machines).
2. Close all machine doors and verify door interlock switches are making contact.
3. Check external devices connected to the E-stop chain.
4. If buttons are released and doors closed but E-stop remains active, use a multimeter to trace continuity through the safety chain to find the open contact.
5. Check the safety relay module (Pilz PNOZ or equivalent) — indicator LEDs show channel status.

Reset: After clearing the condition, press the machine Reset button on the operator panel. The control will re-enable servo power and restore ready state.

Coolant Fault Codes

COOLANT FAULT / COOLANT LEVEL LOW

What it means: The coolant system has a fault — low level in the coolant tank, pump fault, or flow switch not confirming flow.

Causes:

1. Coolant tank level below minimum sensor
2. Coolant pump motor overload tripped (check overload relay in panel)
3. Clogged coolant line or nozzle
4. Flow switch fault

Diagnosis:

1. Check coolant level in the reservoir — refill as needed.
2. Locate the coolant pump overload relay in the electrical cabinet — check for trip indicator and reset.
3. Inspect coolant lines and nozzles for blockage.
4. Verify flow switch operation — bypass the switch temporarily to confirm the fault is switch-related vs actual no-flow.

Communication Error Codes

Error — CAN Bus / SERCOS Communication Fault

Display message: “SERCOS COMMUNICATION ERROR” or “CAN BUS FAULT”

What it means: WinMax lost communication with one or more servo drives over the SERCOS (fiber optic ring) or CAN bus communication network.

Causes:

1. Fiber optic cable damaged or disconnected (SERCOS systems)
2. Drive powered off or failed mid-ring
3. Termination connector missing on the ring
4. Drive firmware version mismatch

Diagnosis:

1. For SERCOS: inspect all fiber optic cables for bent or crushed sections. Fiber doesn’t survive tight bends — the minimum bend radius is typically 30mm.
2. Verify all drives in the ring are powered and showing ready status.
3. Check that the ring termination connector is installed on the last drive in the ring.
4. For CAN bus: check CAN bus termination (120-ohm resistors at each end of the bus).

Parameter Error Codes

WinMax Error Code Reference Table

Parts Reference Table

Contact Hurco at 800-638-1849 or [email protected] for machine-specific part numbers. Hurco’s WinMax Help Center at support.hurco.com has a searchable error code database with current resolution procedures.

Technician Notes

• NavErr first: Before calling Hurco service, save a NavErr diagnostic record. It captures the exact machine state at fault time and saves diagnostic time on the call.
• Parameter backups are critical: If you don’t have a parameter backup for your machine, request one from Hurco service before any drive work. Restoring a machine from scratch without parameters is a multi-day job.
• ATC recovery mode: When the ATC jams mid-cycle, never use brute force. WinMax has an ATC recovery mode (Setup > Maintenance > ATC Recovery) that lets you step through the cycle one step at a time to find the stuck point and safely recover.
• Fiber optic handling: On SERCOS machines, never bend fiber cables tightly or route them in cable tracks without proper service loops. Fiber damage is the most common cause of mystery communication faults.
• Encoder cable tracks: Inspect encoder cable tracks annually on high-cycle machines. The encoder cables are the most failure-prone component on production Hurco machines because they flex thousands of times per shift.

Where to Buy Replacement Parts

Find replacement parts for Hurco CNC machines on Amazon:

• Hurco CNC Machine Parts
• SERCOS Fiber Optic Cable CNC Replacement
• CNC Servo Drive Encoder Cable Track