Service Home How To Procedures VMC - X/Y - Axis Servo Motor - Replacement - AD0656
Last updated: 07/01/2026

VMC - X/Y - Axis Servo Motor - Replacement

Revision 1

AD0656

Revision A - 07/2026

Introduction

This procedure tells you how to replace the servo motors on the horizontal axis. This procedure is applicable for VMC X and Y axis that has a solid coupling. Refer to the Ballscrew - Flex Coupling - Replacement if your machine has the flex coupling.

 Caution: You should not do machine repairs or service procedures unless you are qualified and knowledgeable about the processes. Serious damage to the machine components can result in costly repairs. The service technicians at your Haas Factory Outlet (HFO) have the training and experience, and are certified to do these tasks safely and correctly. The repair and service work performed by your HFO is protected with a limited warranty.

This procedure applies to all X or Y axis servo replacement kits for milling machines. Review the BOM of a specific machine for the specific kit numbers. 

Important: If a motor is replaced and the motor mount did not already have a cover, then refer to the VF/VR - X/Y Motor Mount Cover - Reference document to find out if a motor mount is compatible with your motor. To further protect the motor, a motor seal should be added to the compatible motor. Refer to VMC - X/Y Servo Motor Seal - Installation for motor seal installation. Failing to install a motor mount cover and/or motor seal on a compatible motor can result in coolant intrusion.

Note: Starting in 2026, Haas may send Yaskawa servo motors as service replacements for machines that were built with Mitsubishi servo motors. To facilitate this, patches will be included with the replacement kits; however, if only one axis is replaced, either alarm X.9959  SERIAL ENCODER CABLE FAULT or alarm X.9719 SERIAL ENCODER FAULT will be triggered with sub codes 0x4 and 0x5. See the section "Mitsubishi to Yaskawa conversion" for details and how to manage the patch files. 

Replacement

1

If possible, position table to be in the front right corner for easy access to servo motors. 

Power the machine OFF.

Remove all of the sheet metal parts that are obstructing the access to the servo motor.

For the Y-Axis, the enclosure on the back of the column needs to be removed. For the X-Axis, the saddle's left waycover needs to be removed. 

Peel back the coupler access gasket [1] from the servo motor housing for both axes using a putty knife if needed. 

IMPORTANT: Work on one axis at a time. Once the first servo motor is replaced, then repeat procedure on the remaining axis. 

2

Remove the Servo Motor

Loosen the lower coupler clamping bolt [1].

Disconnect the power cabel from the motor. Note the orientation of the cable connectors.

Remove the bolts [2] that secure the servo motor to the housing.

Pull the servo motor straight out, as square as possible to the housing, until the coupler disengages the end of the ballscrew and remove it from the machine.

Loosen the upper coupler clamping bolt [3] and remove the coupler from the motor.

Note: Make sure you retain the shaft key from the ballscrew [4] and the servo motor shaft [5].

Note the orientation of the servo motor shaft.

3

Install the Servo Motor

 Important: When installing the coupler and the servo motor make sure that the shaft keys are in place during the process. It is possible for the key to fall out during installation. Missing key will result in positioning accuracy errors.

Hand rotate the servo motor shaft until orientation of the new servo motor shaft matches the orientation of the old servo motor shaft.

Install the shaft key [1] in the keyway on the end of the ballscrew.

Install the coupler [2] on the end of the ballscrew.

 Note: Leave the clamping bolt loose at this time.

Orient the motor so the cable connectors are facing the same direction as the old servo motor.

Align the key [3] on the servo motor shaft with the keyway in the coupler and push the servo motor into the housing.

Install the servo motor mounting bolts [4] and torque them.

Center the coupler [5] between the ballscrew and the servo motor and torque the clamping bolts [5]. Refer to HAAS FASTNER TORQUE SPECIFICATIONS.

Apply a new coupler access gasket [6].

IMPORTANT: Make sure the housing surface is cleaned with acetone before applying the gasket. 

4

Install Servo Motor Cables

IMPORTANT: All axis cables and connectors should have dielectric grease on contact points. Before connecting, check if dielectric grease needs to be reapplied, make sure to only place grease on on the contact points of the connectors. Do not apply excess grease to the entire face of the connector. This can cause damage to the servo motor. 

Motor Power Cable:  Connect the motor power cable to the motor by lining up the amphenol key slot and turning the amphenol until the connector is fully secured.

Motor Encoder Cable:  Connect the encoder cable into the motor encoder connector by lining up the arrows and pushing the connector until it locks in place.  After the connector is locked slightly pull on the cable to make sure the connector is secured..   

IMPORTANT: The video on this step shows the correct method of installing the encoder cable.

Home Sensor:  Connect the axis home sensor by lining up the key slot and turning the connector until is fully secured.

 

5

Attach all of the sheet metal parts that were removed for servo motor access. 

Reset the axis grid offset. Refer to the Axis Grid Offset - Mill 13.14 or Higher and Lathe 6.11 or Higher for CHC and Next Generation Control - Axis Grid Offset for the NGC.

Reset the axis tool change offset. Refer to VMC - Side-Mount Tool Changer - Set Parameter 64 - Z-Axis Tool Change Offset, Umbrella Tool Changer - Set Parameter 64 - Z-Axis Tool Change Offset for the CHC and the Next Generation Control - Side-Mount Tool Changer - Z-Axis Tool Change Offset, Next Generation Control - Umbrella Tool Changer - Z-Axis Tool Change Offset for the NGC.

Refer to the Haas Fastener Torque Specifications for the torque values.

For the ballscrew specific tooling and torque values refer to the Ballscrew - Installation Tools and Torque Specifications.

Mitsubishi to Yaskawa Conversion

Starting in 2026, Haas may send Yaskawa servo motors as service replacements for machines that were built with Mitsubishi servo motors. Converting from Mitsubishi to Yaskawa servo motors requires changing parameters and tunes.

All of the 93 kits will come with a patch for all three linear axes (X, Y, and Z). This means that the axis that still has Mitsubishi servo motors will have patches applied to them and those extra patches will need to be removed. 

Patches will be included in the replacement kits; however, if only one axis is replaced, either alarm X.9959 SERIAL ENCODER CABLE FAULT or alarm X.9719 SERIAL ENCODER FAULT will be triggered with sub codes 0x4 and 0x5

For the alarm X.9717 or X.9959, the X will show up as any of the following:

  • 1: for the X axis
  • 2: for the Y axis
  • 3: for the Z axis. 

See the table for the list of affected part numbers.

Note: If configurations were applied and extra patches are not removed, X.9719 SERIAL ENCODER FAULT will generate on the other axis that did not have its motors swapped.

Note: If configurations were not applied and none of the patches are present X.9959 SERIAL ENCODER CABLE FAULT will be generated on 

Mitsubishi Motor Part number Yaskawa replacement kit  part number
SRVOMTR MITS HF 09 62-0087 SIGMA-V 09 MOTOR W/SEAL 93-6076
SRVOMTR MITS HF 13 62-0089 SIGMA-V 13 MOTOR 93-6078
SRVOMTR MITS HF 20 62-0096 SIGMA-V 20 MOTOR W/SEAL 93-6081

1

After the Mitsubishi motor has been removed and the replacement Yaskawa has been installed, load configurations Configuration File - Download/Load - NGC.

 After the configuration has been loaded and the machine is power cycled, there will be encoder alarms X.9717 will be generated on the axes that were not replaced. Follow the procedure How To Delete Patch Files - NGC. 

2

After the patches have been deleted, only the patches of the axis that had their Mitsubishi motors with Yaskawa will be listed.

Note: This process will need to be repeated any time the machines has its cofigurations updated.