Martorell, Spain — Seat's Martorell plant is now catching up to 1% of automotive blanks per batch that ship out of welding with missing bolts. The detection comes from a 3D vision and RFID stack built by STT Systems, LMI Technologies, and Stemmer Imaging.

The Volkswagen Group facility near Barcelona runs thousands of blanks a day. Before the system went in, a missing fastener usually surfaced downstream, sometimes at final assembly. Now it gets flagged the instant the blank leaves the weld cell.

What's actually being inspected?

Bolts. That's it. After blanks clear the welder, a missing fastener is the most common reason a sound body panel gets sent back for rework. The new line scans each blank from multiple angles using Gocator 2490 and 2380 sensors from LMI Technologies. The sensors build high-resolution 3D point clouds that resolve individual bolt heads.

If a head is missing, the system tells the line's PLC to divert the blank for manual touch-up. If the count is right, the blank moves on.

Takeaway: bolts are cheap, but a missing one at final trim is not.

Who built the stack?

Three vendors. STT Systems, founded in 1998 in San Sebastián, handled integration and machine vision through its Visio division. LMI Technologies supplied the Gocator hardware. Stemmer Imaging, a machine vision distributor, brought system expertise.

RFID antennas along the line read a tag embedded in each blank, so every inspection result lands in a centralized database tied to a specific unit. The plant can now trace any panel's quality record back through the line.

What did Seat get out of it?

The vendor pitch is strong. STT Systems CEO Iker Urgandarin said: "The automated bolt inspection system has dramatically improved Seat Martorell's production efficiency. By detecting missing bolts early in the process, they've minimized costly delays and rework, while boosting overall equipment efficiency and reducing labor costs."

The reported gains, stripped down:

• Up to 1% of blanks per batch flagged as defective, which Seat used to absorb as downstream rework.
• Manual inspection reduced to the exception, not the default.
• Per-blank traceability for statistical process control.

Takeaway: catching a bolt at the weld cell costs seconds. Catching it at final trim costs minutes per unit and possibly a line stop.

What to watch next?

The architecture is built to scale. STT says the same stack can absorb more complex inspections as Martorell's quality requirements grow. The next real questions: does the defect catch rate fall below 1% as the system learns its own data, and does VW Group port the setup to other body shops?

Martorell is the proof point. Puebla, Wolfsburg, and Bratislava would be the followers, if and when.

One thing Seat won't say: the price tag. Vendor case studies rarely do.