MPL-A420P-HJ22AA - Allen-Bradley X-axis servo motor (motor only)

Allen-Bradley MPL-A420P-HJ22AA X-axis servo motor – motor only

The MPL-A420P-HJ22AA servo motor is the X-axis drive motor, which moves the print carriage back and forth over the media. It is sold here on its own, without a gearbox or pulley, complete with its encoder feedback and power cables.

This is the Allen-Bradley / Kinetix MP-Series brushless AC servomotor (Rockwell P/N 7042-00-1202, Series A), a low-inertia motor controlled in a closed-loop system by the Kinetix drive, with absolute encoder feedback. Its low rotor inertia enables it to withstand direction changes at the end of its travel without losing position, which determines the consistency of the scanning speed and therefore the quality of the droplet deposition.

The motor alone is the most common cause of failure on this axis: the motor usually fails due to overheating, whilst the right-angle gearbox remains intact. If the gearbox rotates freely, without noise or play, replacing the motor alone is sufficient to restore the axis to working order. If the gearbox is also faulty, refer to the complete motor and gearbox assembly.

Technical specifications

• Catalogue reference: MPL-A420P-HJ22AA
• Rockwell P/N: 7042-00-1202 – Series A
• Manufacturer: Allen-Bradley (Rockwell Automation) – Kinetix MP-Series range
• Part type: motor only, without gearbox or pulley – supplied with feedback and power cables
• Motor type: low-inertia brushless AC servomotor, with integrated absolute encoder
• Axis concerned: X-axis – print carriage drive
• Power supply: 230 V RMS between phases, three-phase – frequency 0 to 333 Hz
• Power: 2.0 kW / 2.8 HP – continuous duty
• Maximum speed: 5,000 rpm
• Continuous holding torque: 4.74 Nm (42 lb.in)
• 0-peak continuous current: 12.7 A
• Voltage constant Ke: 53 V 0-peak between phases per 1,000 rpm
• Resistance between phases: 0.96 Ω at 25 °C
• Insulation class: 180 (H) – permissible ambient temperature 40 °C
• Protection rating: IP66 with shaft seal
• Control: Kinetix drive – voltage PWM control

Identification before ordering

• Note the full catalogue number from the nameplate on the existing motor
• The suffix must match exactly: MPL-A420P-HJ22AA
• The variants MPL-A420P-HJ72AA and MPL-A420P-SJ72AA are available: they differ in terms of the encoder feedback, the shaft or the presence of a brake, and are not interchangeable without verification
• Check the shaft diameter and the mounting method on the gearbox side
• Check the type of connectors and the length of the feedback and power cables
• If in doubt, please send us a photo of the motor’s nameplate: we will confirm the compatibility before dispatch

Function

• Drives the print carriage back and forth along the X-axis via the right-angle gearbox and the carriage belt
• Maintains a constant scanning speed across the entire print width
• Handles acceleration and direction changes at the end of the travel without any positional drift
• Reports the actual position to the Kinetix drive via its integrated absolute encoder
• Receives the torque and speed setpoints from the drive via voltage PWM control

Possible symptoms of wear

• X-axis fault or servo error on start-up; carriage fails to initialise
• Abnormal motor overheating and thermal shutdown after a few hours of production
• Carriage jerks, moves in fits and starts or runs at an irregular speed during scanning
• Vertical stripes and registration misalignment between passes
• Encoder feedback error or loss of position signalled by the drive
• Rumbling noise coming from the motor, distinct from the gearbox noise
• Overcurrent detected by the inverter on the affected axis

Replacing the motor alone restores the axis to working order at a lower cost when the right-angle gearbox is in good condition. As overheating is the primary cause of failure on this axis, it is recommended that the ventilation and correct operation of the X-axis motor cooling kit be checked at the same time; otherwise, the replacement motor will be subjected to the same thermal stresses.

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