1A1-0044

Access machine parameters

Press MOD key, enter machine parameter access code if required, select 'Machine Parameters' and navigate to the axis parameters section. Identify the rotary axis showing the alarm (check error log for axis designation).

Use the search function (MP NUMBER field) to jump directly to parameter 1020 for faster navigation on controls with many installed axes.

Verify MP1020 modulo setting

For the affected axis, check MP1020.x (where x is axis number). If value = 1, the axis is configured as roll-over/modulo. Confirm this matches your machine design - typically C-axes, rotary tables, and indexers use modulo = 1.

Document current value before changes. Some rotary axes on mill-turn machines may intentionally NOT use modulo if mechanical stops are present.

Check software limit parameters

Navigate to MP1410.x (negative software limit) and MP1411.x (positive software limit) for the same axis. Record current values. If these show anything other than 9E99 (or 9.9E99 depending on TNC generation), they are active and causing the conflict.

Do not change parameters while programs are running or axes are in motion. Ensure machine is in a safe state.

Disable software limits for modulo axis

Set MP1410.x = 9E99 and MP1411.x = 9E99 for the roll-over axis. This disables software limit checking which is incompatible with modulo operation. Save parameters and perform a control reboot (not just reset).

After reboot, verify axis display shows proper modulo behavior - position should wrap from 359.999° to 0.000° rather than incrementing indefinitely.

Test axis operation

In manual mode (handwheel or axis keys), rotate the axis through multiple revolutions in both directions. Verify no limit violations occur and position display wraps correctly. Test programmed G-code with multi-revolution movements.

Execute a test program with both shortest-path (M126) and direction-specific (M127) rotary moves to ensure modulo calculations work correctly.

Review parameter backup source

Check the date and origin of the last parameter backup loaded. Compare the machine configuration document to determine if axis types match. Look specifically at whether rotary axes should be modulo or limited.

Keep separate backup files labeled with machine model and date. Parameters from a 3-axis mill are not directly compatible with a 5-axis machine without review.

Verify mechanical axis configuration

Physically inspect the rotary axis in question. Determine if it has mechanical limit switches, hard stops, or is designed for continuous rotation. This dictates whether modulo operation is appropriate.

If unsure about mechanical limits, consult machine documentation or OEM before enabling unlimited rotation - collision damage may result.

Set correct MP1020 for axis type

For continuous rotation axes (trunnion tables, spindle C-axis): set MP1020.x = 1. For limited rotation axes (tilting heads with mechanical stops): set MP1020.x = 0. This must match physical machine capability.

Common configurations: C-axis (spindle) = modulo 1, A-axis (trunnion) = modulo 1, B-axis (tilting head) = often modulo 0 with ±120° limits.

Configure limits or disable appropriately

If MP1020.x = 0 (non-modulo), set MP1410/MP1411 to actual mechanical travel limits. If MP1020.x = 1 (modulo), set both MP1410.x and MP1411.x = 9E99. Save and reboot control.

For non-modulo rotary axes, leave 2-5° safety margin between MP limits and actual mechanical stops for deceleration distance.

Update PLC program if necessary

If PLC program monitors software limits or modulo status, verify logic matches new configuration. Check PLC markers associated with axis limit switches (typically M40xx range depending on TNC model).

On iTNC 530 and TNC 640, use PLC Programming Station to search for references to the axis number in limit switch monitoring logic.