Battery Tray Feature Check: Multi-Camera Plus 3D at 88 s
A battery tray is the load-bearing structure of a traction battery, typically larger than 1.8 m by 1.5 m by 0.3 m, and a single tray carries more than a thousand measurement points. Its surface is covered with dozens of feature types: rivet holes, threaded holes, stud holes, coolant nozzle holes, thin-wall holes, chamfered holes and stamped parts. This cell combines multi-camera vision with 3D measurement, completing hole position, surface profile, flatness, linear position and missing or wrong assembly inspection within an 88 second cycle, subject to site acceptance results.
Dozens of features, one template will not do
Rivet, threaded and nozzle holes have different contour forms, thin-wall and chamfered holes have different edge characteristics, and stamped parts are solid outlines. One template for all of them guarantees boundary misjudgment. Features are grouped by type and extracted with a matching method per group.
Which items need the 3D unit
Hole position and linear position can be computed in a 2D field. Surface profile and flatness cannot, because they describe how a surface rises and falls in 3D space. A 3D measurement unit owns those two item families and fuses its results with the multi-camera output to form a complete feature list.
Zone views and one joint calibration
Multiple cameras are arranged by feature distribution, splitting the oversized part into vision zones. Dense feature areas get more cameras and higher per-point resolution; sparse areas get less redundant imaging. Overlap between adjacent zones takes part in stitching verification so cross-zone features are neither duplicated nor missed.
Cameras and the 3D unit must be calibrated jointly into the workpiece frame before zone results can be stitched and compared. A systematic calibration error can leave every zone passing internally while hole spacing across zones shifts as a whole.
Presence and tolerance need separate verdicts
A missing stud or an absent stamped part is a different problem from a dimension out of tolerance: one is a required object not being there, the other an object being there but in the wrong place or size. The cell runs presence judgment and dimensional measurement separately, each with its own conclusion, so a missing part is not reported as a tolerance failure and a tolerance failure is not reported as a missing part.
How 88 seconds is spent
When the tray arrives on the line, cameras and the 3D unit trigger together and capture all feature images and point clouds in one station entry. Each vision zone computes independently, the controller aggregates, and the whole-part verdict is issued within 88 seconds. Synchronized triggering ensures all cameras see the same instant of the tray, avoiding measurement error from small movements during capture.
The sensor mix follows the feature mix
Where features are dominated by planar hole positions, the multi-camera share can be higher. Where surface profile and flatness carry more weight, the 3D unit must be configured alongside. Selection should set the ratio from the actual feature composition of the workpiece.
Points raised in the feature review
Why multi-camera plus 3D rather than one method?
The tray needs hole position, surface profile and flatness together. Multi-camera covers hole families and linear position, while 3D handles profile and flatness; only fusion covers dozens of feature types.
Can a thousand points be measured in 88 seconds?
Cameras are zoned by feature area, capture simultaneously and compute in parallel, turning a thousand points into zone units processed together before aggregation. The cycle is subject to site acceptance results.
How is hole position computed from an image?
Hole contour and similar features are extracted, transformed into the workpiece frame using the joint calibration, compared with the theoretical position, and checked against the drawing tolerance band.
Can a missing stud be confused with a hole diameter error?
No. Presence judgment and dimensional measurement run separately: a missing feature yields a missing-part verdict, while a present feature beyond tolerance yields a dimensional verdict.
Can similar welded assemblies reuse the cell?
It applies to battery trays and similar large welded assemblies, but camera count must be reconfigured for feature type and point count, with a 3D channel reserved. It cannot be copied line for line.