ALARM 304 Z AXIS LIMIT + occurs when the Z-axis travels beyond its positive software or hardware limit, triggering Input 33 on the I/O diagnostics. This protective alarm immediately stops all motion to prevent collision with the machine column or spindle head assembly.
HaasOvertravel/LimitBasic5-15 minutes
304
Haas Alarm 304 - Z Positive Limit
Z AXIS LIMIT +
This alarm activates when the Z-axis travels or attempts to travel beyond the positive software or hardware travel limit during rapid positioning, feed moves, or manual jogging. The MOCON continuously monitors Z-axis encoder position feedback against the travel limit values in Settings 42 and 43. When the limit is exceeded, all axis motion halts immediately to protect the spindle head, column ways, and prevent upward collision with mechanical stops.
Root Cause Summary
ALARM 304 Z AXIS LIMIT + occurs when the Z-axis travels beyond its positive software or hardware limit, triggering Input 33 on the I/O diagnostics. This protective alarm immediately stops all motion to prevent collision with the machine column or spindle head assembly.
Safety
Jog slowly away from limit
Causes and Fixes
1
Check Active Work Coordinate System
Press OFFSET/SETTING, then WORK to view current work coordinates. Note which coordinate system is active (G54, G55, etc.) and check the Z-axis offset value.
The active coordinate system is shown in the position display area
2
Verify Z-offset Against Machine Limits
Compare the Z-offset value to Parameter 221 (Z+ Software Limit). Ensure the offset doesn't cause programmed moves to exceed this limit.
Never set work coordinates that would cause the spindle to crash into the column
3
Correct Work Coordinate Z-offset
If offset is incorrect, re-establish work coordinates using proper touch-off procedures or manually adjust the Z-offset value in the work coordinate table.
4
Test with Cautious Movement
Use JOG mode with reduced feed rate override to verify the corrected coordinates allow safe Z-axis travel within limits.
1
Access Software Limit Parameters
Press OFFSET/SETTING, then PARAMETERS. Navigate to Parameter 221 (Z+ Software Limit) and verify the current value against machine specifications.
Parameter changes require proper authorization level and machine manufacturer specifications
2
Compare to Machine Travel Specifications
Check the machine data plate or manual for actual Z-axis travel limits. Parameter 221 should be set slightly less than the physical limit switch position.
Typically set software limits 0.1-0.2 inches before hardware limits
3
Verify Hardware Limit Switch Position
Manually jog Z-axis upward slowly while monitoring I/O diagnostics (SETTING, then I/O DIAG) to see when Input 33 (+Z Limit) activates.
Use extreme caution and low jog speeds when approaching limit switches
4
Adjust Parameter if Necessary
If parameter is incorrect, adjust Parameter 221 to appropriate value based on physical measurements and reboot the control (EMERGENCY STOP, then power cycle).
1
Check I/O Diagnostics Status
Press SETTING, then I/O DIAG. Locate Input 33 (+Z Limit) and observe its status. It should be OFF when Z-axis is away from the positive limit.
Input status should change from OFF to ON only when the limit switch is physically actuated
2
Inspect Limit Switch Physically
Visually inspect the +Z limit switch for damage, proper mounting, and correct positioning. Check that the switch actuator arm moves freely and contacts the machine properly.
Ensure machine is powered off and locked out before physical inspection
3
Test Switch Continuity
Using a multimeter, test the limit switch for proper continuity when actuated and open circuit when released. Check wiring connections for tightness and corrosion.
Haas typically uses normally-open limit switches that close when actuated
4
Replace or Adjust Switch
If switch is faulty, replace with identical Haas part number. If positioning is incorrect, adjust mounting to ensure proper actuation point before hardware damage occurs.
1
Review Program at Alarm Line
Press PROGRAM, then use cursor to locate the line number where the alarm occurred. Look for Z-coordinates in the current and previous blocks that may exceed travel limits.
Check both the current block and any active modal commands from previous blocks
2
Verify Post-Processor Settings
If using CAM software, check that the post-processor is configured for the correct Haas machine model with proper travel limits and work coordinate setup.
Incorrect post-processor settings are a common cause of limit overtravel
3
Simulate Program Path
Use the control's graphics simulation (GRAPHICS button) to visualize the tool path and identify where the Z-axis exceeds safe travel limits.
Graphics mode shows tool path relative to current work coordinates
4
Correct Program Coordinates
Edit the program to use appropriate Z-coordinates within machine limits, or adjust work coordinate system to accommodate the programmed moves safely.
1
Check Reference Position Status
Look for 'REF' indicator in the position display. If missing, the machine needs to be re-referenced before normal operation.
Never operate the machine without proper reference position established
2
Clear Alarm and Reference Machine
Press RESET to clear the alarm, then press POWER UP/RESTART. Follow the on-screen prompts to reference all axes, starting with Z-axis if possible.
Some Haas controls allow individual axis referencing through the jog panel
3
Verify Encoder Feedback
After referencing, check that position displays update smoothly during manual jogging. Erratic position readings indicate encoder problems.
Encoder issues require immediate attention to prevent crashes
4
Test Normal Operation
Perform test movements in JOG mode to verify proper position tracking and limit detection before resuming automatic operation.
