Omron CJ1W-NC434 4‑Axis Position Control Unit for CJ Series PLCs

The Omron CJ1W-NC434 is a high‑performance position control unit (PCU) for the CJ1, CJ2, and CJ2M series programmable logic controllers. It provides four independent axes of pulse train output (open collector or line driver) to drive stepper motor drivers or servo amplifiers. The unit supports up to 500 kpps output frequency, enabling high‑speed positioning for pick‑and‑place, assembly, and packaging machinery. Each axis can perform trapezoidal or S‑curve acceleration/deceleration, linear interpolation between two axes, and positioning in both absolute and incremental modes. The CJ1W-NC434 includes a built‑in encoder input for each axis, allowing simple closed‑loop control with external encoders.

Technical Specifications

Functional Description

The CJ1W-NC434 executes positioning sequences stored in its internal buffer memory. The user’s PLC program writes target positions, speeds, and acceleration times to the PCU’s data registers. The unit then generates pulse trains according to the configured motion profile. It monitors the encoder feedback (if used) to correct position errors. The PCU also processes hardware limits (POT, NOT) and home proximity sensors directly, responding faster than the PLC scan. The unit supports a “torque limit” output (TL) for servo drives and an “emergency stop” input per axis.

Positioning Modes

The NC434 supports several positioning modes:

• Positioning (PTP): Move to absolute or incremental target position.

• Interpolation: Linear interpolation between two axes (X‑Y, X‑Z, Y‑Z).

• Speed control: Continuous rotation at constant speed until a stop command.

• Pulse train output: Direct pulse count without position loop.

For homing, the unit can perform several sequences: return to sensor, limit switch, encoder Z‑phase, or a combination.

Wiring and Connections

The CJ1W-NC434 uses two 40‑pin connectors (MIL type) for the four axes. Each axis has output signals: pulse train (CW/CCW) and direction control, plus inputs for home, limit +/-, and encoder (A/B/Z). A separate 24V DC power supply is required for the output circuits; the unit draws minimal current from the PLC backplane. The cable should be shielded, and the shield grounded at the drive end only. Maximum cable length: 10 meters (for open collector) or 50 meters (line driver).

Programming and Configuration

The unit is configured using CX‑Position Control software (part of CX‑One). Parameters include axis operating mode, electronic gear ratio, backlash compensation, and acceleration/deceleration curves. Positioning data (target positions, speeds) can be created offline and downloaded to the unit. The PLC program uses dedicated motion instructions (e.g., START, STOP, HOME) from the CJ1W‑NC library. The unit also provides status flags and error codes accessible via I/O memory.

Diagnostic Features

LED indicators on the unit’s front panel show power, run, and axis errors. The unit stores error history, and error codes can be read from the status word. Common errors include encoder signal loss, limit overtravel, and driver alarm detection. The PCU can also detect pulse output short circuits.

Applications

The CJ1W-NC434 is used in pick‑and‑place machines (gantry robots), printed circuit board assembly, drilling/routing tables, labeling machines, and packaging equipment (carton erectors, case packers). It is suitable for retrofitting older machines with modern pulse‑train servo drives.

Conclusion

The Omron CJ1W-NC434 provides a powerful, 4‑axis motion control solution for CJ series PLCs, combining flexible pulse output, encoder feedback, and interpolation capabilities in a compact module.