Automated 3D measurement for bolt hole geometry

Sizector 3D measures flange thickness for safer car hubs

The bolt holes on a vehicle hub are far more than mere openings. They are the critical interface connecting the wheel to the axle. Any deviation in flange thickness can lead to loose bolts, structural deformation, or catastrophic vibrations, directly compromising vehicle stability and passenger safety.

To address these high-stakes manufacturing challenges, Mega Phase Technology introduces a robust 3D inline measurement solution. With two Sizector 3D cameras, we provide a high-speed, high-precision safety barrier that ensures every hub meets the most stringent automotive standards.

During inspection, Sizector projects light and snaps a wheel hub to get thickness data for a vision system.

Project requirements

Accurate 2D localization

Identify and locate bolt holes on the shiny flange surface.

Confirm the hole quantity.

Thickness measurement

The tolerance is set as 0.4 mm. To ensure the quality, measurement accuracy is required to be 0.04 mm.

Close-up of a bolt hole with a deep counterbore structure and glossy inner walls

Technical challenges: precision in a complex environment

Automotive production lines demand a balance between extreme accuracy and high-speed throughput. Standard inspection methods often struggle with:

High-mix Hub Model: Modern lines must seamlessly switch between 5-hole, 6-hole, and 8-hole hub designs without downtime.

Environmental Factors: Temperature drift in a factory setting can easily degrade measurement stability if not properly managed.

The "Shiny Object" Problem: The smooth, machined surfaces of bolt holes (counterbores/countersinks) create intense interreflection and occlusions, which typically "blind" standard 3D sensors.

Model selection

Camera model: S028240

Resolution: 2.8 megapixels

Regional Z-axis Repeatability: 0.21 um

Frame rate of full cycle time: 20.3 FPS @0.7 MP, 8.7 FPS @ 2.9M

Pixel pitch: 0.123 mm

Depth of view (DOF): ±60 mm

(Two fans)

A streamlined 3D measurement workflow

Dual-camera synchronization for precise thickness measurement

01Setup and calibration

As shown in the diagram, align the top and bottom cameras to cover the same Field of View (FOV) for the same measurement area. Unify the coordinate systems via our SDK to ensure the thickness is measured as a single, cohesive data point.

02 Acquisition and point cloud optimization

Capture the point clouds of hub bolt holes. Apply hardware features, such as ROI segmentation and partition projection, to suppress interreflection interference from highly reflective inner walls of the counterbore. All this effectively improves point cloud quality.

03 Real-time data processing

Stitch the point clouds and measure thickness in the SDK.

Proven results: exceptional stability

As shown in the figure below, our Sizectors capture complete data successfully on both sides of the flange. The data is qualified by a rigorous validation test of 500 continuous measurements. 

Raw images and crisp point cloud data of both spotface and counterbore

Stability Test: Line graph of 500 measurement cycles showing a stable thickness range (P-V) of only 0.0305 mm

A total of 500 measurements were taken for the bolt hole thickness.

Max Value: 8.7837 mm
Min Value: 8.7532 mm
Range (Peak-to-Valley): 0.0305 mm

This result meets the required accuracy specifications.

Why system designer choose Nega Phase Technology 3D solutions

High flexibility & efficiency 

The S028240’s wide Field of View (FOV) allows for single-shot coverage of standard bolt holes. This eliminates the need for complex motion stages, making the system adaptable to various hub models with zero mechanical changeover.

Integrated 2D + 3D measurement

Why use two systems when one will do? Our solution utilizes 2D localization to identify hole positions and quantities, which then guides the 3D sensors just in the camera for thickness measurement. This all-in-one workstation reduces footprint and integration costs

Tackle challenging objects with ease

This 3D industrial camera effectively suppresses interreflection from shiny bolt holes with its built-in hardware functions like partition projection and ROI Segmentation. Effectively eliminating the ghosting and data noise caused by metallic reflections, the result is a reliable, high-quality data stream that ensures no defective part ever leaves the factory.