Customer Requirement & Industry Challenge

A leading metro train manufacturer required high-precision sensor discs for their traction motor assemblies. These discs play a crucial role in providing real-time speed and position feedback, ensuring smooth acceleration, braking, and energy efficiency.

Key Customer Requirements:

  • Tight dimensional tolerance (±5 microns) to ensure accurate alignment with the motor shaft.
  • Precisely machined sensor slots and mounting holes for accurate signal detection.
  • ENP (Electroless Nickel Plating) with uniform thickness for wear resistance and corrosion protection.
  • Minimal warpage and flatness deviation within 10 microns to ensure stability during high-speed rotation.

The customer faced several challenges with their existing supplier, including:

  • Inconsistent bore diameter tolerances, leading to misalignment.
  • Variation in ENP coating thickness, causing signal interference.
  • Flatness deviations, resulting in sensor reading errors and increased maintenance costs.

Given the high safety and reliability standards in metro applications, the customer needed a precision machining partner capable of delivering sensor discs with flawless quality and repeatability.

Challenges in Machining Sensor Discs for Traction Motors

1. Achieving ±5 Micron Bore & Slot Tolerance

  • Sensor discs have tight-fitting bores and precision slots that require micron-level accuracy.
  • Tool deflection during boring can lead to out-of-tolerance dimensions, affecting disc alignment.
  • Achieving this level of precision on a 4-axis VMC without secondary operations posed a significant challenge.

2. ENP (Electroless Nickel Plating) Thickness Control

  • The ENP layer must be uniform (10-12 microns) across the surface to ensure corrosion resistance and accurate sensor readings.
  • Variations in plating thickness can result in signal distortion, material buildup in critical areas, and coating failure under stress.

3. Maintaining Flatness & Structural Integrity

  • The sensor disc rotates at high speeds, requiring precise flatness to prevent imbalance and vibrations.
  • Improper clamping or uneven machining stress can lead to warpage, causing sensor misalignment and inaccurate readings.

Qualicom’s Precision Machining Approach

1. High-Precision Boring & Slot Machining on 4-Axis VMC

  • Used customized boring tools with adaptive feed rate control to maintain bore diameters within ±5 microns.
  • Designed specialized carbide end mills for slot machining, ensuring sharp, burr-free sensor slots.
  • Developed rigid fixturing techniques to eliminate deflection and ensure repeatable accuracy.

2. ENP Coating with Thickness Consistency & Adhesion Control

  • Partnered with an ISO-certified ENP facility to ensure precise plating thickness across all batches.
  • Implemented post-plating dimensional checks using CMM scanning to verify uniformity.
  • Conducted adhesion testing to confirm coating durability under operational stress.

3. Flatness & Warpage Prevention Techniques

  • Applied stress-relief machining sequences to minimize material distortion after cutting.
  • Used controlled clamping pressure to prevent unwanted deformation during VMC operations.
  • Conducted final flatness inspection with CMM and laser measurement tools, ensuring minimal deviation.

Final Outcomes & Business Impact

By implementing precision machining strategies, plating control, and rigorous quality assurance, Qualicom successfully delivered high-performance sensor discs that met the customer’s expectations.

Key Achievements:

✅ Dimensional accuracy improved to ±5 microns, ensuring superior fit and function.
✅ ENP coating thickness controlled at 10-12 microns for consistent corrosion protection.
✅ Flatness deviation reduced, eliminating warpage issues.
✅ Rejection rate reduced significantly, improving overall quality and reliability.
✅ Customer secured a long-term supply agreement for metro traction components.

By delivering precision-machined sensor discs with flawless plating and structural integrity, Qualicom has reinforced its position as a trusted machining partner for the railway and metro industry.

Why Choose Qualicom for High-Precision Railway Components?

✔ Tight-tolerance CNC/VMC machining for critical railway applications.
✔ Expertise in machining and coating processes like ENP plating.
✔ CMM-based quality inspection for consistent accuracy.
✔ Efficient process optimization for cost-effective production.

Looking for high-precision traction motor components? Contact Qualicom today to discuss your machining needs.