5.1 c-axis service procedures

C-Axis - Service Procedures

Procedure Description
C-Axis Motor Replacement - ST-15-35 Lathe - NGC This procedure will show you how to replace the C-Axis motor on ST-15-35 machines.

5.2 c-axis engagement offset

C-Axis - Engagement Offset Procedures

Procedure Description
C-Axis - Engagement Offset - Lathe - ST-15-35 - NGC This procedure tells you how to set the C Axis engagement on ST-15 through ST-35 NGC lathes.
C-Axis - Engagement Offset - Lathe - ST-35/40 - NGC This procedure tells you how to set the C Axis engagement on ST-35/40 NGC lathes.

5.3 c-axis troubleshooting

C-Axis - ST-15-35 - NGC - Troubleshooting Guide

TG0042

Revision A - 05/2026

Lathe C-Axis Inspection Report

Download and fillout the C-Axis Inspection Report Checklist below before replacing any parts.

Lathe C axis Inspection Report Checklist

Introduction

  1. C-Axis Brake Caliper
  2. C-Axis Gear/Brake Disc
  3. C-Axis Servo Motor
  4. C-Axis Actuator

 

Symptom Table

Symptom Possible Cause Corrective Action
C-Axis Alarms 7.993, 7.103, and 7.9959 The servo motor has a fault. Refer to the Sigma 5 Servo Motor Troubleshooting Guide.
The amplifier has a fault.

Refer to the Amplifier Troubleshooting Guide.

Note: If a short-circuit is found, inspect the cable and motor for a short circuit before installing a new amplifier.
Noise/Vibration The C-Axis Engagement is out of alignment. Set the C-Axis Engagement.
  • Non-repeatable spindle orients between power cycles.
  • C-Axis engagement alarms.
  • Re-running taps and threads between power cycles.

ST-15/20/25 lathes and variants built from 8/1/2022 switched the 5.6" Non-Contact Encoder mounted on the spindle to a 3" NCE on the motor output shaft. A home switch was added to the spindle to ensure repeatable spindle orientation at power up. This home switch was not enabled by parameters for these machines.

The home switch was also not enabled by parameters for all NGC ST-50/55 machines built 1/1/2021 and later.

Update the machine to the latest software version and download and load the latest configuration files from the service portal.

HSG-A  02-7-2023
Alarm 7.9821 The C Axis failed to move off the engage input in the time allowed while trying to disengage.  Press RESET and try again. Check the C-Axis Disengage Move off Input Timeout parameter in the error report. This value should be a reasonable value.
Alarm 7.9989 C-Axis Failed to Engage. The C-Axis Engagement is out of alignment. Set the C-Axis Engagement.
C-Axis Failed to Engage. The machine parameters are not tuned for the part or workholding installed. Calibrate the Spindle Load with Setting 413. See Setting 413 Main Spindle Load Type section below.
Alarm 7.9992 C-Axis Failed to Disengage. The C-Axis Engagement is out of alignment. Set the C-Axis Engagement.
Alarm 7.9719 C-AXIS SERIAL ENCODER FAULT Oil lubricant for the C-axis is leaking into the motor through the shaft. This damages the encoder causing the machine to generate ALARM 7.9719 C-AXIS SERIAL ENCODER FAULT. Refer to HBC-A-03/26/2025 for the corrective action. 

Setting 413 – Main Spindle Load Type

Setting 413 is available for machines with the New Mocon enabled and with software version 100.21.000.1111 or greater. The New Mocon, is a Motion Control algorithm that uses more parameters to better control the axis of the machine. Press Diagnostic and navigate to the System tab. The Mocon version will be in the Software section. Mocon version 1.16  .S. is the New Mocon. If the Mocon Version is 1.16 or 1.16  .K, then you have the old Mocon Version. 

 Note: At this time we are not updating machines to New Mocon in the field.