Systems Integration: 3D vision system inspects connector pin height

G2 Technologies developed an automated connector inspection system that is built on the PXI platform from National Instruments and combines a machine-vision based non-contact 3D inspection system, a cleaning station, electrical test and engraving stations.

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A faulty connector that ends up in the final assembly and is buried deep within an automotive subsystem could endanger the consumer and prove very costly to the connector manufacturer.

If a tier-1 automotive supplier, for example, integrates a bad connector into an Engine Control Unit (ECU), and that ECU gets sold to an automotive manufacturer, is installed in vehicles and results in a recall, much of the associated cost will likely be charged back to the connector manufacturer.

In order to minimize the risk of faulty connectors making it into the supply chain, one major US connector manufacturer gave engineers at G2 Technologies (Apex, NC, USA; www.g2tek.com) the nod to develop an automated connector inspection system. The system, built on the PXI platform from National Instruments (NI; Austin, TX, USA; www.ni.com/vision), combines a machine-vision based non-contact 3D inspection system, a cleaning station, electrical test and engraving stations.

Before connectors enter the 3D vision system for board-side scanning, they are inspected to verify that the correct part is present and that it's in the proper orientation.

"Inspectors can see bent and missing pins all day long, but it's easy to miss a faulty connector with a pin that's just too short," explains Craig Borsack, President of G2 Technologies. "This application is a huge improvement. By offering noncontact inspection and the ability to spot these type of flaws that were previously making it through the process, our non-contact inspection system could save this connector manufacturer and others millions of dollars or more each year."

The inspection system is installed after stitching, a process that accumulates contact pins and inserts them into molded connector housings. Stitched connectors enter on an input conveyor and pass under a Genie Nano M1920 GigE Vision camera from Teledyne DALSA (Waterloo, ON, Canada; www.teledynedalsa.com).

An image of the connector is acquired with illumination provided by a DL 194 diffuse dome light from Advanced illumination (Rochester, VT, USA; www.advancedillumination.com). The image is then analyzed to verify that the correct part is present and that it's in the proper orientation to proceed through the inspection process. If the part is not correct or is improperly oriented, the system diverts it into a reject bin.

Parts deemed correct and that are properly aligned proceed to an orientation wheel that repositions the part board-side down, for the next station, which is board-side inspection. At this station, a scanCONTROL 2650-25 laser line profiler from Micro Epsilon (Ortenburg, Germany; www.micro-epsilon.com) scans the entire board side of the connector.

Metal clips (1, 2, 3, and 4) on the connector create a reference plane from which the system measures the height of the contacts. Two posts (T and U) on the connector provide a datum for measuring the position information for each contact. The 3D view (right) shows a close up of post U and contact 5 and 6.

After board-side inspection, connector-side inspection takes place. Due to cycle time requirements, and the need to scan the part from both directions, inspection of the mating side of the connector is performed at two stations by two additional laser line profilers.

"Two scans are required due to shadowing effects created by the connector shell as the part is scanned from one side," explains Borsack. "In order to get a complete 3D point cloud, the part must be scanned from both directions, then the images are combined to mask out the shadows."

The system scans from both sides and creates a plane based on a pad (feature) on the bottom of the mate side connector. This plane will be used to measure true position and pin height of the contacts.

Borsack said his company is proud of the 3D inspection system it has developed and hopes other connector manufacturers will consider exploring this for their companies.

"It's a small price to pay when you look at the potential savings it offers. Not only can this inspection system help protect a manufacturer from being sued for millions of dollars in damages in a recall situation," Borsack said. "It could also absolutely save lives."

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