Service Home Sigma 5 / 7 - Axis Servo Motor and Cables - Troubleshooting Guide - NGC

Sigma 5 / 7 - Axis Servo Motor and Cables - Troubleshooting Guide - NGC

Last updated: 04/21/2022

Sigma 5 / 7 - Axis Servo Motor and Cables - Troubleshooting Guide - NGC

Download and fillout the Servo Motor Inspection Report Checklist below before replacing any parts.

Servo Motor Inspection Report Checklist

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Electrical Safety

 Caution: When you do maintenance or repair on CNC machines and their components, you must always follow basic safety precautions. This decreases the risk of injury and mechanical damage.

  • Set the main circuit breaker to the [OFF] position.

 Danger: Before beginning any work inside the control cabinet the High Voltage indicator light on the 320V Power Supply / Vector Drive must have been off for at least 5 minutes.

Some service procedures can be dangerous or life-threatening. DO NOT attempt a procedure that you do not fully understand. If you have any doubts about doing a procedure contact your Haas Factory Outlet (HFO) and schedule a service visit.

Symptom Table

Symptom Probable Cause Corrective Action
Alarm 9719 SERIAL ENCODER FAULT Encoder signals are affected by noise from high power cables. Refer to Serial Data Communication Faults / Electrical Noise section below.
Alarm 9918 SERIAL ENCODER INTERNAL DATA ERROR Faulty servo motor encoder. Check for the servo motor for coolant contamination.
Alarms 9930 SERIAL ENCODER POOR COMMUNICATION Encoder signals are affected by noise from high power cables. Refer to Serial Data Communication Faults / Electrical Noise section below.
Alarms 9959 SERIAL ENCODER DISCONNECT Cables are not connected correctly or encoder is faulty. Inspect the cables and connectors. Refer to the Main Processor/Encoder Cable section below. 
Alarms 161 AXIS DRIVE FAULT
 Faulty servo amplifier. Check the corresponding amplifier assembly.

Refer to Servo Amplifier - Troubleshooting Guide to troubleshoot the amplifier.
Alarm 217 AXIS PHASING ERROR Cables are not connected correctly  Inspect the cables and connectors. Refer to the Main Processor/Encoder Cable section below. 
The wrong type of motor has been installed. Check that the correct motor type has been installed.  (Sigma-5 or Sigma-7)
Alarm 645 AMPLIFIER GROUND FAULT Faulty power cable. Check the corresponding servo motor. Refer to Servo Motor section below.
Faulty servo motor. Check the corresponding servo motor. Refer to Servo Motor section below.
Alarm 993 SHORT CIRCUIT Faulty power cable. Inspect the cables and connectors. Refer to Servo Motor section below.
Faulty servo motor. Check the corresponding servo motor. Refer to Servo Motor section below.
Alarm 103 AXIS SERVO ERROR TOO LARGE Encoder signals are affected by noise from high power cables. Or Faulty encoder. Refer to Serial Data Communication Faults / Electrical Noise section below. Check the encoder steps/revolution versus and ball screw pitch and verify the encoder counts are accurate per each rotation.
The axis motor brake, is not disengaging when servos are enabled. See the Motor Brake section below:
The axis ballscrew is damaged. Check the corresponding axis ballscrew.

Refer to Ballscrew - Troubleshooting Guide to troubleshoot the ballscrew.
Alarm 103 AXIS SERVO ERROR TOO LARGE, during the zero return process. The axis zero returns in the wrong direction. The home sensor is being made during the zero return process causing the axis to zero return in the opposite direction. Check the axis home switch to make sure there are no metal chips on top of the sensor.
Alarm 552 TRIPPED CIRCUIT BREAKER (on UMC-1000) Damaged wire conduit and wires within conduit. Remove back panel. Inspect wire conduit. If damaged, contact Haas Service Department for assistance.
The machine servos make a humming noise while sitting idle, jogging, or on a rapid. The axis grid offset needs to be adjusted. Perform the Axis Grid Offset adjustment procedure.
The ballscrew is not aligned. Verify that the ballscrew does not bind during travel and that it is correctly aligned.
Outdated parameters. Download the latest configuration files. If the axis servo continues to hum, contact your local HFO for more troubleshooting information.
Alarm 9804 240 VAC GROUND FAULT gets generated when I zero return an Axis.
 There is a short circuit on the cable or motor. Check for a short circuit on the corresponding servo motor and cable. Watch the Servo Power Cable and Motor Inspection Videos.

Note:  If alarm gets generated on a ST machine when the A-axis is zero returned the LT axis cable and motor must also be check for a short circuit condition.

Serial Data Communication Faults / Electrical Noise

Sigma-5 servo motors, non-contact encoders output serial data signal to the control. If the serial data signal is missing or becomes unreliable the control will generate a serial data communication error. Electrical noise can cause the serial data signal from the encoder to become unreliable and cause false alarms. Follow the troubleshooting guide below to help eliminate the noise in the system.

  1. Incorrect machine grounding. Make sure the ground wire size is correct. Also the ground wire should run all the way back to the electrical panel.
  2. Noise from other equipment. Make sure the machine does not share it's electrical service with another machine.
  3. Loose encoder data connectors at PCB or at the motor encoder, can cause the serial data to become unreliable. Refer to the Main Processor / Encoder Cable section.
  4. Loose ground or high voltage power connectors will induce noise into the system.
    • electrical cabinet check for loose connection at all the ground and high voltage power terminals (vector drive, wye-delta contactors, transformer..etc).
    • pendant check for loose terminal connectors.
    • spindle head check for loose ground and motor power terminals.
  5. The ferrite filters suppress high frequency noise produced by the amplifiers and vector drive, when servos are on. Make sure they are installed in:
    • Encoder data cables. Make sure there is a ferrite filter P/N 64 1252 installed in all the encoder data cables.
    • Axis motor power cables. Make sure there is a ferrite filter P/N 64-1252 installed in X, Y, Z axis motor power cables [1].
    • Spindle motor cables. Make sure there is a ferrite filter installed in the motor output of the vector drive.

      For a 40HP vector with 6 wire leads [1] use ferrite P/N 64-1254.

      For a 40HP vector with 3 wire leads [2] use ferrite P/N 64-1252.

      For a 20HP vector drive with 6 or 3 wire leads [3, 4] use ferrite P/N 64-1252.

  6. Cable routing. Make sure that the encoder cable is separated from high power spindle/axis/pump cables.

Maincon PCB / Encoder Cable

Corrective Action:

Examine the connector [1] on the Maincon. Make sure it is not damaged.

Examine the cable. Look for signs of damage or stiffness. The connector [4] has two housings [2,3] for the cable pins.

If the pins have been pushed into the motor, you must replace the motor and cable together.

Make sure the cable is firmly connected at both ends. Reseat both connections. Make sure the cable is installed in the correct connector at the Maincon or MOCON PCB.

Servo Motor

Corrective Action:

Make sure the cables are connected correctly to the corresponding amplifier. Inspect the connector at the motor. Look for loose connections or contamination.

Look for signs of damage or stiffness on the cable. Disconnect the power cable from the amplifier and motor. Measure the resistance from leg to leg, and from leg to ground. Make sure the measurements result in an open connection. Check each leg from one end of the cable to the corresponding leg on the other end of the cable for continuity. If there is an open connection, there is a problem with the cable.

Make sure the motor's connectors are not contaminated. Disconnect and inspect the power cable connector at the motor. Make sure that there is no coolant contamination. Coolant contamination can generate drive fault alarms and damage the amplifier. Measure the resistance from the pins labeled A, B and C at the motor connector to chassis ground.

  • The reading must show an open circuit.
  • If the reading does not show an open circuit, the servo motor is at fault.

Motor Brake

Corrective Action:

Reseat the the connection for connectors P3, P4, or P5 on the I/O PCB.

Measure the voltage across the red and black cables.

Press [EMERGENCY STOP]. There should be no voltage.

Press [RESET] to clear the alarms. The voltage should be between 20-30 VDC.

Examine the connection at the motor's brake [2] and power connectors [3] for contamination. Reseat the connections.

If no voltage is present, refer to:

Electrical Diagrams

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