Case Study: Brevettato NDX13A/40 Spindle Rebuild After Severe Moisture & Oil Contamination

Spindle Make: Brevettato
Model: NDX13A/40 ISO 40
Serial Number: 02529/19
Condition at Arrival: Locked Up
Service Performed: Full Precision Rebuild + Pneumatic System Restoration

This Brevettato NDX13A/40 spindle was received in a locked condition and unable to rotate. Initial inspection revealed significant contamination from the compressed air system combined with missing internal components in the rotary coolant coupling.

The level of internal damage confirmed prolonged moisture and compressor oil exposure.

Condition at Receipt

Upon arrival, the spindle exhibited:

  • Complete lock-up
  • Rotary coolant coupling missing internal components
  • Evidence of severe contamination

The customer will replace the rotary coolant coupling before returning the spindle to production.

Disassembly Findings

Full teardown revealed multiple critical issues.

1️⃣ Bearing Failure Due to Grease Washout

All internal grease had been washed out of the bearings.

The bearings installed originally were open (non-sealed) steel ball bearings:

  • KH60092RZETAP4+DUL
  • KH6014-2RZCTAP4+DUL

Without grease protection, contamination entered the bearing paths, causing:

  • Lubrication breakdown
  • Increased friction
  • Bearing seizure

This led directly to spindle lock-up.

2️⃣ Moisture & Compressor Oil Contamination

A black, gooey residue was found throughout the spindle assembly. Analysis strongly indicated a mixture of:

  • Moisture/water from compressed air supply
  • Compressor oil carryover

This contamination was present:

  • Inside the bearing cavities
  • On internal components
  • Within the stator laminations

Moisture inside a spindle assembly accelerates corrosion and destroys lubrication integrity.

3️⃣ Internal Rust Formation

Significant rust was found on internal components.

This confirms prolonged exposure to moisture within the compressed air system. Rust inside a precision spindle affects:

  • Bearing seats
  • Shaft surfaces
  • Tool retention components
  • Dynamic balance stability

4️⃣ Stator Contamination & Recovery

The stator was filled with the same black residue.

To restore electrical integrity:

  • The stator was washed multiple times
  • It was baked in our precision oven for over 18 continuous hours
  • Air-cooled gradually
  • Tested after reaching room temperature

After bake-out and testing, the stator returned to 100% acceptable condition.

This prevented a costly motor replacement.

Additional Mechanical Findings

🔹 Drawbar Actuator Rebuild

The drawbar actuator/unclamp cylinder was completely disassembled, cleaned, inspected, and rebuilt.

🔹 Gripper Damage

Surface cracks were discovered around two gripper ball pockets.

Special Notation:
The gripper must be replaced due to cracking around the ball pocket areas.

Operating with cracked gripper pockets risks catastrophic tool retention failure.

Rebuild Process

Due to contamination severity, a full rebuild was required.

✔ Component Restoration

Each component was:

  • Cleaned
  • Media blasted
  • Polished
  • Inspected
  • Re-qualified or replaced

Additional labor hours were required due to extensive contamination cleanup.

✔ Bearing Upgrade

New sealed steel ball bearings were installed to replace the original open bearings.

Sealed bearings provide improved protection against:

  • Moisture intrusion
  • Oil contamination
  • Grease washout

This upgrade significantly increases resistance to compressed air system contamination.

✔ Dynamic Balancing

All rotating components were dynamically balanced:

  • Prior to final assembly
  • After complete assembly

This ensures high-RPM stability.

✔ Clean Room Assembly

Final cleaning, preparation, and assembly were performed in our Class 10,000 clean room environment to ensure contamination-free precision assembly.

Final Testing & Certification

After assembly:

  • Spindle was run and broken-in
  • Performance testing completed
  • Drawbar retention force verified and recorded
  • Tool eject / EM dimension preset and recorded
  • Final assembly and testing completed in clean room

The spindle was packaged for shipment after full certification.

Root Cause Summary

The primary failure driver was contaminated compressed air containing:

  • Moisture
  • Compressor oil

This caused:

  • Grease washout
  • Bearing seizure
  • Rust formation
  • Stator contamination
  • Drawbar actuator contamination

Compressed air system maintenance is critical for protecting spindle longevity.

Key Lessons

1️⃣ Open Bearings + Contaminated Air = Accelerated Failure

Sealed bearings provide improved protection in high-moisture environments.

2️⃣ Moisture Causes Internal Rust

Even small amounts of water in compressed air can cause corrosion inside precision assemblies.

3️⃣ Oil & Moisture Can Reach the Motor

Stator contamination can lead to expensive electrical failures if not addressed quickly.

4️⃣ Early Intervention Prevents Motor Replacement

The stator bake-out procedure restored functionality before permanent damage occurred.

Final Takeaway

This Brevettato NDX13A/40 spindle was saved from catastrophic failure due to timely intervention.

However, unless the compressed air system contamination issue is corrected, recurrence risk remains high.

Protecting compressed air quality protects:

  • Bearings
  • Tool retention systems
  • Electrical components
  • Overall spindle life