The C axis disappears from the operator screen after MP10 changes from 31 to 10111, and the control stops requesting its reference move. Disconnecting the motor still produces errors because the visible NC-axis configuration and the electrical drive channel are separate layers.
What is the screen telling you?
The successful screen change proves that MP10, labeled Aktive Achsen, controls which axes the NC exposes as active. It does not prove that the associated motor, feedback device, drive channel, and PLC interlocks have been removed from monitoring.
| Observation | Configuration layer | What it proves |
|---|---|---|
| C axis vanishes from the display | NC active-axis definition | The NC no longer presents C as an operating axis. |
| C axis no longer requests referencing | NC motion sequence | The reference routine excludes C. |
| Errors appear after the motor is unplugged | Drive, feedback, or PLC monitoring | At least one lower-level function still expects the C-axis hardware. |
| B axis must also be removed | NC, drive, and PLC configuration | Repeat the same end-to-end checks for B; the demonstrated MP10 result applies specifically to C. |
The tag is right; the binding is incomplete. Changing the active-axis field removes the NC representation, while the drive system can continue checking channel readiness, motor feedback, temperature circuits, or contactor state.
Which disabling approach fits the maintenance job?
Two configurations can support maintenance, but they solve different problems. Choose by whether the motor and its feedback wiring must be physically disconnected.
| Approach | Setting or action | Physical motor connection | Effect | Use when |
|---|---|---|---|---|
| Logical axis removal | Remove the axis from MP10
|
Leave connected | Hides the axis and removes its reference request; drive monitoring may remain active | The machine must run tests while the axis stays electrically intact |
| Complete channel decommissioning | Remove the axis from MP10, disable its drive and feedback channel, and revise related PLC checks |
May be disconnected after all monitoring is removed | Removes both the operator-level axis and lower-level hardware expectations | The machine is partially dismantled and the motor or feedback cable must be unplugged |
For operation with the motor still installed, logical removal is the smaller and more reversible change. For an unplugged B or C motor, use complete channel decommissioning. An MP10-only change cannot meet that requirement.
Why does unplugging the motor still create errors?
An NC axis normally spans several independent functions: the operator display, NC coordinate processing, PLC permissives, the servo drive channel, and motor feedback. Removing an axis from the coordinate system affects only the layers governed by the active-axis definition.
When power returns, the drive subsystem can still poll the assigned channel. An open motor or feedback circuit then prevents the channel from reaching its expected state. PLC logic may also wait for a drive-ready signal even though the axis is absent from the NC screen.
| Diagnostic symptom | Likely origin | Check at the control |
|---|---|---|
| Alarm appears immediately during startup | Drive-channel hardware or feedback monitoring | Read the first chronological alarm and identify the reporting subsystem |
| Startup completes but machine enable remains blocked | PLC permissive or drive-ready chain | Trace the B- or C-channel ready input through the PLC diagnostics |
| Axis is absent but a channel remains listed in drive diagnostics | Drive assignment remains commissioned | Compare the commissioned drive channels with the active NC axes |
| Error begins only after a connector is removed | Motor, feedback, thermal, or wiring supervision | Use the alarm text and drive diagnostic page to identify the open circuit being monitored |
Work from the first alarm rather than secondary machine-enable messages. One missing drive-ready condition can generate several downstream symptoms.
What must be recorded before changing the configuration?
- Back up the complete machine-parameter and PLC configuration using the control's supported service method.
- Record the original
MP10value of31and the tested value of10111. - Record how the parameter editor represents
MP10. Do not reinterpret10111as decimal, binary, or a digit mask unless the control documentation identifies that representation. - Capture the first alarm produced with each motor connected, disconnected, and reconnected. Record its reporting subsystem and sequence, not only the final machine-stop message.
- List every B- and C-axis connection being removed: motor power, motor feedback, thermal monitoring, brake wiring, and any separate limit or reference inputs actually fitted.
- Identify the drive channels assigned to B and C, then locate the PLC signals that consume their ready, fault, enable, or reference states.
The machine builder's parameter list and PLC documentation decide which lower-level settings belong to these channels. No additional parameter identifier can be derived from MP10 alone.
How do you disable B and C end to end?
- Return to the documented baseline and confirm that the connected machine starts in its original configuration. This separates existing faults from configuration changes.
- Remove B and C from the NC active-axis definition. Apply the demonstrated
MP10edit only with the control's documented value representation. - Restart through the configuration-activation method required by the control, then confirm that both axes are absent from the position display and reference sequence.
- Open the drive diagnostics and locate the channels formerly assigned to B and C. Disable or decommission those channels using the machine-specific drive configuration. Do not redirect them to another installed axis.
- Remove or bypass only the PLC conditions that belong exclusively to the decommissioned channels. Preserve shared emergency-stop, guarding, lubrication, spindle, and machine-enable logic.
- With power isolated according to the machine's service procedure, disconnect the intended motor and feedback circuits. Do not install improvised electrical substitutes unless the drive and machine documentation explicitly defines them.
- Restore power and inspect the first diagnostic event. If a B- or C-related drive channel is still polled, return to its drive assignment. If all drive channels are ready but machine enable remains blocked, trace the remaining PLC permissive.
- Repeat the process one axis at a time. Decommission C and verify it before applying the equivalent documented changes to B.
Separating the axes makes diagnosis deterministic. Removing both simultaneously can hide which drive assignment or PLC branch still references each channel.
How do you verify the maintenance configuration?
| Verification point | Pass condition |
|---|---|
| Operator display | B and C are absent; remaining axes retain the intended labels and coordinates |
| Reference sequence | No B- or C-axis reference request appears |
| Drive diagnostics | No commissioned channel expects the disconnected B or C hardware |
| PLC diagnostics | No B- or C-ready condition blocks the intended maintenance operating mode |
| Alarm history | No new motor, feedback, drive-ready, or axis-assignment alarm appears after startup |
| Remaining motion | Each retained axis moves only under the correct command and reports the correct position |
Test at reduced maintenance conditions permitted by the machine documentation. If axis labels, directions, or feedback assignments change, stop and restore the backup; a drive-channel mapping was altered rather than merely decommissioned.
Frequently Asked Questions
Why does the C axis disappear but the disconnected motor still causes an error?
MP10 removes C from the active NC axes, while the drive or PLC can still monitor its motor, feedback, or ready state. Decommission the associated drive channel and remove its exclusive PLC dependency before disconnecting the hardware.
Why can I not use the same MP10 change as proof that B is disabled?
The observed change from 31 to 10111 demonstrated C-axis removal only. Identify how B is encoded in the documented MP10 representation, then verify B separately at the display, reference, drive, and PLC layers.
Why should I disable one axis at a time?
One-at-a-time changes identify exactly which drive assignment or PLC permissive belongs to each axis. After each change, restart the control, confirm the axis is absent from the reference sequence, and verify that the disconnected channel produces no new alarm.