What causes Haas alarm 231?

Damaged or worn jog handle MPG encoder internal components including cracked encoder disk, contaminated optical sensor, or failing LED/phototransistor elements. Loose or intermittent connection in jog handle cable between pendant and IOCON board causing signal dropouts during handle rotation. Electrical noise induced into jog handle encoder signals from damaged cable shielding, improper cable routing, or proximity to motor power cables and VFD outputs. Contamination inside jog handle assembly including metal chips, coolant, or debris interfering with encoder disk rotation or optical path. IOCON board encoder input circuit failure or damaged connector pins causing incorrect signal levels or noise susceptibility on jog handle inputs.

How do I fix Haas alarm 231?

1. Step 1: Disconnect jog handle cable at control pendant connection, inspect connector pins for damage, corrosion, or bent pins, clean connector contacts and firmly reseat cable 2. Step 2: Access Diagnostics page and monitor jog handle encoder count values while slowly rotating handle in both directions, watch for erratic counts, missing counts, or unexpected reversals 3. Step 3: Inspect jog handle cable along entire length for damage to outer jacket or shielding, verify cable routing avoids sharp bends and is separated from AC power and spindle motor cables 4. Step 4: If machine has removable jog handle, carefully disassemble handle housing and clean internal MPG encoder disk and optical sensors with compressed air and lint-free cloth dampened with isopropyl alcohol 5. Step 5: Substitute known good jog handle assembly or swap with working machine if available to isolate whether fault is in handle MPG encoder versus cable or IOCON board inputs 6. Step 6: Replace jog handle assembly if encoder is confirmed failed, or check IOCON board connector and encoder input circuitry if fault persists with known good handle, contact Haas support for IOCON board repair or replacement if board-level fault confirmed

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Haas Controller

System · Intermediate · 30 minutes - 4 hours

Alarm 231

Haas 231 - JOG HANDLE TRANSITION FAULT | Haas CNC Alarm

Alarm 231 Y-Axis Following Error occurs when the Y-axis encoder feedback position deviates from the commanded position beyond the threshold set in Parameter 29 (Following Error Limit). This safety alarm prevents crashes by immediately faulting the axis when it cannot maintain proper position tracking during motion or at rest.

HaasSystemIntermediate30 minutes - 4 hours

231

Haas 231 - JOG HANDLE TRANSITION FAULT | Haas CNC Alarm

JOG HANDLE TRANSITION FAULT

Root Cause Summary

Alarm 231 Y-Axis Following Error occurs when the Y-axis encoder feedback position deviates from the commanded position beyond the threshold set in Parameter 29 (Following Error Limit). This safety alarm prevents crashes by immediately faulting the axis when it cannot maintain proper position tracking during motion or at rest.

Safety

Power off machine before manual axis inspection
Check for mechanical damage before restarting operation
Ensure the machine is properly grounded before performing any electrical troubleshooting.
Disconnect power to the machine before working on any electrical components.
Be aware of potential pinch points and moving parts when manually moving the axis.
Support the axis to prevent it from dropping unexpectedly if components are removed.
Consult the machine tool builder's documentation before making any adjustments to servo parameters.
Wear appropriate personal protective equipment (PPE), such as safety glasses and gloves.
Never bypass safety interlocks or attempt to operate the machine with known safety hazards.
Always power down and lock out the machine before performing mechanical checks.

Causes and Fixes

1
Check Y-Axis Manual Movement
Press EMERGENCY STOP, then manually move Y-axis by hand. Feel for binding, rough spots, or excessive resistance throughout the travel range.
Ensure spindle is stopped and machine is in emergency stop before manual movement
2
Inspect Ball Screw and Linear Ways
Remove Y-axis covers and visually inspect ball screw for damage, contamination, or lack of lubrication. Check linear guide rails for chips, debris, or worn bearing blocks.
Look for metal shavings or discoloration on the ball screw indicating wear or overheating
3
Verify Lubrication System
Check automatic lubrication system operation and verify proper grease distribution to Y-axis components. Manually lubricate if system is not functioning.
Check Parameter 31 (Lubrication Timer) to ensure proper lubrication intervals
4
Test Axis Movement
After addressing mechanical issues, jog Y-axis at slow feed rates (10-50 IPM) and monitor for smooth operation before returning to normal speeds.

DIY Feasiblemedium confidence

Call a technician if:

·Servo amplifier replacement needed
·Encoder replacement required
·Ball screw replacement necessary
·Servo parameter tuning required

Prevention

Maintain proper lubrication schedules
Keep way covers intact and sealed
Regular cleaning of axis components
Monitor servo load percentages during operation
Avoid crash conditions through proper programming

Common Mistakes

Adjusting Parameter 29 without addressing root cause
Ignoring mechanical binding issues
Not checking for contamination in encoder
Overlooking loose motor connections
Failing to verify proper lubrication system operation

Related Alarms

230 232 233 410 411

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Always verify with your machine manual or a certified technician before performing service procedures.