Service Home How To Procedures 50-Taper - Non-Contact Encoder - Replacement - AD0180
Last updated: 07/30/2025

50-Taper - Non-Contact Encoder - Replacement

AD0180

Revision A - 7/2025

Introduction

This procedure tells you how to replace a non-contact encoder.

If you have one of these conditions:

  • You must replace the read head for a non-contact encoder.
  • You must replace a 50-Taper spindle that has a non-contact encoder.

 Important: When replacing a non-contact encoder under warranty, make sure the old part is returned in the replacement part packaging or the warranty may be voided.

Non-Contact Encoder - Identification

Generation 1 and Generation 2 non-contact encoders are not compatible, and will not communicate with each other. If you are upgrading from a Generation 1 NCE to a Generation 2 NCE, the read head and encoder ring will both need to be replaced. 

Generation 2 non-contact encoders can be identified by the pigtail cable attached to the side of the read head [1]. Generation 1 encoders do not have this cable. 

50-Taper - Non-Contact Encoder - Replacement

1

Push [POWER OFF].

Set the main circuit breaker to the OFF position.

Lock the main circuit breaker. Use an approved lock with an approved safety tag.

Close the primary air valve. This stops the air supply to the machine.

2

Remove the Tool Release Piston. Refer to VMC - 50-Taper - TRP - Replacement.

Disconnect the encoder cable and the ground cable [2] from the encoder read-head [1].

3

If you must replace the read head for a non-contact encoder:

Remove the (2) screws [1].

Remove the encoder read-head [2].

Go to Step 5.

4

If you must replace the spindle:

Remove the (4) screws. Remove the encoder ring assembly [1].

Remove the (3) screws. Remove the encoder read-head assembly [2].

Replace the spindle. Refer to VMC - 50-Taper - Spindle - Replacement.

IMPORTANT: Do not dispose of the read head mount. It will be re-installed.

5

Install the encoder ring [1] onto the replacement spindle.

Measure the total indicated runout (TIR) on the encoder ring [1]. Set the TIR as close to .0005" (0.01 mm) as possible, do not exceed 0.002" (0.05 mm).

Torque the (4) screws to 56 in-lb (633 N-cm).

Make sure to install the ground cable.

Install the encoder read-head assembly [2] onto the replacement spindle being sure to use (2) WASHER FLAT 0.170ID X 0.400OD. Make sure the ground cable sits on top of the washer (not under) before installing read head mounting screws.

Torque the (3) screws to 12 ft-lb (16 N-m).

Loosen the (2) screws [3] for the encoder read-head [4].

6

 Note: Before this step, make sure you adjust the drive belts to the correct tension.

For the RLS type encoder:

Put a 0.3 mm plastic shim [2] between the encoder read-head [1] and the encoder ring [3].

Push the encoder read-head toward the encoder ring.

Make sure there is a uniform air gap [4] between the encoder read-head and the encoder ring.

Tighten the (2) screws [6] for the encoder read-head. Remove the shim.

Connect the encoder cable [5] to the encoder read-head.

Mill Encoder Ring to Read Head Alignment

Generation 2 Alignment: Proper alignment of the read head to the encoder ring is critical.  Check that the axial alignment and running gap of the encoder ring are correct.

[A] 0.000 +/- 0.045

[B] 0.012 + 0.008 - 0.004

 

 Note: If the read head and encoder cannot be aligned, the alignment bracket may need to be replaced. See Replace Alignment Bracket below. 

Note: For Generation 1 encoders, use the chart below. 

Generation 1 Alignment: Proper alignment of the read head to the encoder ring is critical. The alignment will vary based on the brand of encoder.  Use the chart provided to make sure the encoder ring and read head are properly aligned.

VENDOR                               RLS                                    BAUMER

A                              0.020" +0.020 / -0.039                 0.0453" +/- 0.019

B                              0.0118" +0.0079 / -0.0039           0.0118" +/- 0.0039

C                                           0.362"                                     0.360"

Incorrect installation of the spindle may axially misalign the motor shaft.  Measure the distance from the top of the motor shaft to the top of the motor TSC mounting hole surfaces.  It should be 1.291 ± .005.

If the shaft is axially misaligned the spindle motor must be replaced.

50-Taper - Non-Contact Encoder - Test

1

To make sure [ORIENT SPINDLE] operates correctly in a Haas Classic Control Machine:

  1. Set the main circuit breaker to the ON position.
  2. Push [POWER ON].
  3. Push [MDI]. Push [ORIENT SPINDLE].
  4. Look at the position of the spindle dogs [1].
  5. Push [RESET].
  6. Manually turn the spindle dogs to a different position [2]. Push [ORIENT SPINDLE] again.
  7. Make sure the spindle dogs stop at the same position [3].

Repeat this process several times to make sure the spindle always orients to the same position.

If the spindle does not orient correctly, the gap between the encoder ring and the read head is not correct. Repeat Step 5 of the replacement procedure.

2

To make sure ORIENT SPINDLE operates correctly in a Haas Next Gen Control Machine:

  1. Set the main circuit breaker to the ON position.
  2. Push [POWER ON].
  3. Push [MDI]. 
  4. Enter M19 
  5. Push [CYCLE START]
  6. Look at the position of the spindle dogs [1].
  7. Push [RESET].
  8. Manually turn the spindle dogs to a different position [2].
  9. Push [MDI]. 
  10. Enter M19 
  11. Push [CYCLE START]
  12. Make sure the spindle dogs stop at the same position [3].

Repeat this process several times to make sure the spindle always orients to the same position.

If the spindle does not orient correctly, the gap between the encoder ring and the read head is not correct. Repeat Step 5 of the replacement procedure.

3

To make sure that the spindle operates correctly:

Operate the spindle at 25% [1], 50% [2], and 100% [3] of the maximum speed.

 Note: In this example the maximum speed is 7500 RPM.

4

Make sure the spindle speed in the code [1] is the same as the spindle speed on the display [2].

If these spindle speeds are not the same, make sure the encoder parameters are correct.