301716

Navigate to Diagnostics > Parameter > Machine Data (MD) and locate MD20100 (MEASURING_SYSTEM_TYPE) for the affected axis. Verify the current value corresponds to SSI-only configuration (typically value 13 or similar depending on control version).

Confirm encoder type in MD20101 (ENC_TYPE) and MD20102 (ENC_INCREMENTS_PER_REV). If encoder is physically SSI/INC hybrid, change MD20100 to hybrid SSI+incremental type (e.g., value 12 or 14) rather than pure SSI.

Do not modify MD values without halting all axis motion and ensuring machine is in safe state.

If encoder is pure SSI absolute type, contact Siemens support to verify drive module firmware version supports SSI-only feedback. Check via HMI > System Information > Drive Firmware or use STARTER software to read drive parameters.

After correcting MD20100, perform a hardware reset (power cycle control and drives) and verify alarm clears during axis homing cycle (reference point approach).

Identify the drive module model and firmware version. In STARTER or via HMI Diagnostics, navigate to Drive Parameters (p-level) and note the drive type (e.g., 6SN1123, 6SN1145) and firmware release version (typically displayed as vX.XX).

Consult Siemens SINUMERIK 840D drive documentation (Function Manual for your specific drive) to confirm SSI-only operation support matrix. Cross-reference firmware version against known limitations; SSI-only support was added in later firmware revisions for some drive types.

If firmware is outdated, use STARTER software to update drive firmware to the latest stable release that explicitly supports SSI absolute feedback without incremental signals. Download firmware from Siemens support portal for your drive model.

Firmware updates require controlled network access to drive and must not be interrupted; allow 10-15 minutes for completion.

Power down the machine and locate the encoder connector on the drive module (typically a circular M12 or rectangular 25-pin connector). Inspect for proper seating and visual damage to pins or cable jacket.

Ensure motor is de-energized and brake (if present) is engaged before accessing connectors.

Cross-reference the encoder cable pinout against the drive connection diagram in the SINUMERIK 840D Hardware Manual. Verify that incremental channels (A, B, Z) are wired to the correct pins if hybrid encoder is installed. SSI-only encoders will have fewer wires (typically 4: SSI_CK, SSI_DATA, GND, +5V).

If incremental wires are missing or misconnected, rewire the encoder cable to include all required channels. Consult encoder manufacturer datasheet to confirm wire assignments (e.g., brown=+5V, blue=GND, white/black=A/A-bar). Use shielded twisted pair for incremental lines to minimize EMI.