Two-Sizector^® 3D setup for thickness measurement of hub bolt holes

Two-Sizector^® 3D setup for thickness measurement of hub bolt holes

Crisp point clouds provided by two Sizector 3D cameras empower wheel hub manufacturing and quality control.

Project requirements

Accurate 2D localization: Identify and locate bolt holes; confirm hole quantity.

Thickness measurement: Tolerances of 0.4 mm with a required measurement accuracy of 0.04 mm.

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

Alt-text: Close-up view of a wheel hub bolt hole showing metallic glare and counterbore depth.

Technical challenges

High-mix Hub Model: 5-hole, 6-hole, and 8-hole...The wide variety of wheel hub types requires a flexible and adaptable measurement solution.

Temperature Drift: Measurement accuracy is susceptible to temperature drift.

Interreflection and occlusion: Designed as counterbores (or countersinks), the hub bolt holes feature smooth surfaces and deep structure, which introduces interreflection and occlusions from lighting.

Model selection

Cameras

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 Sizectors aligned for precise thickness measurement

Alt-text: Diagram of a two-camera 3D measurement setup with cameras positioned above and below the wheel hub.

Measurement procedure

Two Sizectors aligned for precise thickness measurement

Alt-text: Diagram of a two-camera 3D measurement setup with cameras positioned above and below the wheel hub.

01 Setup 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 of both cameras in the SDK using a calibration target for subsequent measurements.

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 Data processing

Stitch the point clouds and measure thickness in the SDK.

Result and accuracy

Inner and outer faces raw images and crisp point clouds

Alt-text: front and rear views of wheel hub. It consists of raw images and crisp point clouds that immune from interreflection and occlusions.

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

Alt-text: Line graph plotting wheel hub thickness variation over 500 measurement cycles

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.

Solution advantages

High flexibility & efficiency 

The Sizector® 3D Camera S028240 achieves single-shot coverage for standard wheel bolt holes, so it effectively solves challenges posed by various hub designs. Our proprietary hardware computational imaging technology (HWCI) for in-camera imaging delivers the high accuracy and frame rates essential for high-throughput production lines.

Integrated 2D + 3D measurement

The camera setup serves as a unified solution where 2D localization precisely identifies bolt hole positions to guide partition projection and ROI settings, while accurate 3D thickness measurement is simultaneously executed in a single workstation.

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. Furthermore, robust post-processing algorithms reliably ensure exceptional point cloud quality and data stability.