1A0-0194

Access machine parameters in service mode

Enter MOD function, select 'Machine Parameters', and authenticate with appropriate password level (typically OEM or service level required for MP access)

Document all existing parameter values before making changes. Incorrect machine parameters can cause machine damage or unexpected behavior.

Identify the affected modulo axis

Review the alarm context or check MP1010 for all axes. The affected axis will have MP1010.x set to a non-zero value (e.g., 360 for degrees, 400 for gon). Note the axis number/letter (x = axis index).

Check and clear software limit parameters

For the identified axis, check MP1020.x (positive software limit) and MP1030.x (negative software limit). For modulo axes, these MUST be set to inactive values. Set MP1020.x = 9999999999 and MP1030.x = -9999999999 (or per machine manufacturer specification).

Some machine manufacturers use different inactive values. Check MP documentation or compare with other known-good modulo axes on the same machine model.

Save parameters and restart control

Save the modified machine parameters, exit the parameter editor, and perform a full control restart (power cycle or controlled restart via MOD functions) to ensure parameters take effect.

Ensure all machine motion is stopped and safe before restarting the control.

Verify axis configuration

After restart, navigate to Test -> Axis diagnostic and verify the affected axis shows as 'Modulo' type with no limit switch indicators active. Test axis motion across the modulo boundary (e.g., move from 350° to 10°).

Use MDI mode to execute a controlled test move that crosses the modulo rollover point to confirm proper continuous rotation without limit interference.

Check limit switch input assignment

Access MOD -> I/O Test or Input/Output configuration. Identify which digital inputs are assigned to hardware limit switches for the affected axis. Note the input numbers and their current states.

Do not manually activate limit switch inputs during testing without ensuring the machine is in a safe state.

Review PLC program limit switch handling

If a custom PLC program is in use, check the PLC source code (typically accessible via MOD -> PLC if permissions allow) for references to limit switch inputs for the modulo axis. Look for M/I input processing related to the axis.

Standard Heidenhain PLC templates automatically handle limit switches. If using manufacturer-customized PLC, contact the machine builder for PLC documentation specific to modulo axis handling.

Physically verify and disconnect limit switches

With machine power OFF and locked out, trace the wiring for the modulo axis limit switches. If the axis is truly intended as modulo (continuous rotation), these switches should not be present. Disconnect the switches or leave inputs open.

Follow lockout/tagout procedures. Only qualified electrical personnel should modify machine wiring. Verify machine builder specifications before removing safety-related switches.

Disable limit switch inputs in configuration

If physical removal is not possible, access the input configuration parameters (specific MP numbers vary by TNC model and version) and disable or unassign the limit switch inputs for the modulo axis. Set input function to 'not used' or equivalent.

On iTNC 530 and TNC 620/640, limit switch input assignments are typically in MP6xxx range. Consult the machine parameter manual specific to your control version.

Test and verify axis operation

After changes, restart control and verify no limit switch indicators appear in axis diagnostics for the modulo axis. Perform full-rotation test moves to confirm unlimited continuous rotation without alarm recurrence.