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Publication Date: 12/1/2011
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Vision System Helps Connector Maker Achieve Zero Defects

Based in Waukegan, IL, JST manufactures electrical and electronic connectors, with a focus on achieving world-class levels of quality. Recently, JST was able to improve on its already extremely high levels of quality by implementing a vision system that measures parts to an accuracy of 0.1mm — better than could be achieved in the past with a human inspector. The vision system also identifies variations much faster than human inspectors, making it possible to adjust machine parameters quickly enough to avoid production defects. The result is that the number of nonconformances in the latest measurement period was reduced to 0 ppm, well below the extremely tough six-sigma quality benchmark of 3.4 ppm.

JST makes more than 30,000 different types of connectors including surface mount, flat flexible circuit, EMI shielded, IC memory card connectors and many others. For most standard terminals, the company uses oxygen-free copper, which has high electroconductivity and inherent toughness and can be brazed with no chance of hydrogen embrittlement. Standard products are all galvanized and treated with a special method that ensures maximum adhesion of electroplating, further reducing electrical resistance and enhancing corrosion resistance.

Tight Dimensional Tolerances
JST's 2.54-mm pitch HCM solderless terminal is used in the automotive industry to attach wires to a printed circuit board (PCB) using crimp-style connectors. The two primary components are the housing and retainer. The user inserts the wires into one side of the housing, then pushes the retainer into an opening on the other side. The user pushes a tab on the retainer to lock it to the housing. Both the housing and retainer are produced by injection molding to tight dimensional tolerances. But while the injection molding process is extremely accurate, there is a small risk that a problem in the process conditions might cause the mold to be incompletely filled — a so-called "short shot" that could cause the part not to work but would be easily visible with the naked eye. However, JST's tough quality specifications prohibit even much smaller short shots that cause only 0.1mm of material to be missing — smaller than could be detected with the naked eye. Defects this small have no effect on the performance of the part, but they are still unacceptable to JST.

Manual Inspection used in past
JST maintained high levels of quality by devoting considerable time and resources to manual inspection. "We spent a lot of time continually checking these parts," said Nate Hoselton, Facilities Manager for JST. "Often problems were not detected until a day or two after the parts had been molded. In that case, we had to go back and re-inspect a considerable number of parts. It was sometimes difficult after the fact to identify the problem with the molding machine. We maintained records for the process conditions, materials, machine parameters, etc., but the operator might have difficulty remembering anything unusual that had happened during the run. As a result, it typically took us several days and about $1,500 to investigate each nonconformance."

Hoselton identified this application as a good one for machine vision. "We have long used machine vision in this plant because of our intense focus on quality. In fact, we have systems from all three of the leading suppliers of machine vision systems. For this project, we selected the Cognex In-Sight vision system because it is easy and fast to program."

Hoselton selected an In-Sight 5600 vision system because it provides a complete solution in a modular package and does not require any additional hardware or other equipment. The 60 x 110 x 80mm package of the vision system easily fits within the tight confines of the manufacturing plant. The In-Sight 5600 model offers a resolution of 1600 x 1200 pixels and an image acquisition time of 15 frames per second. Cognex EasyBuilder? software walks the user step-by-step through the process of setting up a vision application.

The In-Sight vision system has improved the company"s already high quality levels. Manufacturing personnel receive immediate feedback from the vision system for even tiny variations, which are far too small to affect performance and too small to be seen with the naked eye. The assembly machine operator immediately gathers the parts along with the inspection information and takes them to the quality control department. Quality control takes the parts to the molding technician where the issue is addressed. As a result, the time required to determine the root cause and address the manufacturing variation has been reduced to one day and the cost reduced from $1500 to $100.

Most important, the ability to detect and correct even the smallest variations has resulted in JST exceeding demanding six sigma quality objectives. In the most recent measurement period, there was not a single defect in several million parts produced by the company. JST managers attribute this to the implementation of the machine vision system. Hoselton concluded, "Machine vision has helped us make significant improvements by helping us detect variation faster so we can make corrections before defects occur."

Contact: Cognex Corp., One Vision Dr., Natick, MA 01760-2059 877-264-6391 or 508-650-3000 fax: 508-650-3333 Web: 

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