Stator Hairpin Welding Inspection Application

Because stators interact with the rotor to produce torque, they are fundamental to driving motor shafts and propelling vehicles. This application focuses on the inspection of stator windings that utilize the hairpin wire winding methodology.

What manufacturing defects occur?

Many manufacturing defects can occur during hairpin welding, such as:

Defect Description Consequence
Contamination / Inclusions Foreign material trapped within weld metal Can act as stress concentrators, making joint more susceptible to cracking
Welding Gap Gap between welded components beyond acceptable tolerance that leads to a weak joint May fail under stress, resulting in poor electrical connectivity
Insufficient Weld The weld does not completely fuse the hairpins together, leading to weak joints May fail under stress, resulting in poor electrical connectivity
Warping Heat from welding process causes warping of the hairpins Alters alignment within the motor, potentially impacting mechanical and electrical performance
Porosity Small cavities within the weld due to trapped gasses Reduces the strength and conductivity of the weld, potentially leading to failure
Cracking Cracks in the weld, often due to rapid cooling and thermal stresses Significantly weakens the weld, potentially leading to joint failure

These defects can significantly affect the performance, efficiency, and reliability of electric motors and manufacturers should implement quality control measures to prevent them.

However, these defects can be difficult to detect– copper hairpin surfaces may reflect light in a way that masks defects. And many hairpin welding defects are subtle and hard to image, especially if the defect’s contrast to the background is low. Traditional machine vision systems struggle to capture clear images and distinguish between actual defects, reflective surfaces, and the background, ultimately missing defects or causing false rejections.

Hairpin welds can be complex and irregular in shape, varying from one weld to another.

And in high-volume manufacturing environments, hairpin welds must be inspected quickly to keep up with production rates. Traditional machine vision products may fail to keep up with required cycle times.

The Solution

UnitX’s AI-powered inspection effectively inspects hairpin welds where other solutions fail.

First, the OptiX imaging system illuminates and images the hairpin welds. Then, the CorteX Central AI platform is trained on hairpin weld defects. Lastly, those AI models are deployed to the CorteX Edge inference system to detect and classify defects in-line.

Alternatively, manufacturers can use just CorteX AI if they have existing imaging systems. For example, if a manufacturer wants to detect internal hairpin weld defects below the surface or within the weld bead, they can deploy just CorteX AI and integrate it with existing X-Ray and CT Scanners for fast deployment of improved defect detection.

Why UnitX for hairpin weld inspection?

OptiX provides superior images that minimize reflectivity while maximizing defect visibility. It has 32 independently controllable lighting sources that can be optimized for hairpin weld surfaces and various defects via software. Its computational imaging capability can be used to take multiple shots and eliminate hotspots caused by highly reflective hairpin weld surfaces. And its lighting dome design supports a very acute incidence angle of projected light, causing even very tiny defects to cast shadows which increase their visibility.

CorteX accurately detects random, complex defects. It automatically normalizes for variability in positions and orientations and recognizes defects down to the pixel-level. It reduces false positives that lead to scrap and wasted product.

CorteX supports fast AI model development, deployment, and iteration. CorteX AI models are sample efficient– they only require a few images to train on new defect types.

UnitX optimizes yield. In CorteX, can tune quality criteria and visualize the impact on yield before rolling those changes to production.  Manufacturers can indicate acceptable tolerances with hairpin weld defects as not to overreact parts.

UnitX provides rapid, 100% inline inspection. OptiX has bright LEDs and fast fly capture speeds of 1m/s for high speed imaging. And CorteX Edge supports high inference speeds (up to 100 MP) to quickly output an OK/NG decision, seamlessly communicating that decision via integration to all major PLC, MES, and FTP systems.

Manufacturers who use UnitX to automate hairpin weld inspection are able to:

  • Prevent quality escapes that impact automobile reliability, performance, and safety
  • Reduce scrap by minimizing false rejection rates common with traditional machine vision
  • Improve yield by analyzing production and quality data for process improvement opportunities
  • Automate inspection at the speed of their production to increase stator manufacturing throughput

To learn more about how UnitX can automate inspection for you, please contact us here