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A better view of manufacturing: vision-based system helps Ausco Products ensure assembly quality of braking systems.

It is a basic truism that a product or component is only as good as the manufacturing system that produced it. Indeed, history is full of examples of highly engineered, well-designed products that didn't make the grade commercially because of quality or assembly issues on the shop floor that ultimately couldn't be effectively hurdled.

It is also generally accepted that much of a product's success or failure depends on how efficiently it can be manufactured. An elaborate or complicated assembly process can result in wasted time, wasted money and even quality issues with a product that can ultimately cause headaches on the warranty side.

As a result, the drive toward better manufacturing processes and techniques is a never-ending march and most companies are continually assessing and evaluating every aspect of their manufacturing procedures to squeeze every last bit of effectiveness out of them.

A good example is Ausco Products, Benton Harbor, Mich. A manufacturer of brake systems and components for off-highway equipment, Ausco recently adopted new vision-based technology designed to ensure product quality through the manufacturing and assembly process.

"Before production starts on a new brake program at Ausco, a PFMEA (process failure mode and effects analysis) team assesses what could go wrong," said Rick Layer, senior manufacturing engineer at Ausco. "The team determines how to prevent it from going wrong, and to detect any and all potential problems."

As an example, Layer cited the EZTorque mechanical ball ramp caliper the company introduced to the zero-turn radius mower market. During its PFMEA, a potential failure mode--the possibility for an assembler to miss one or two ball bearings in the assembly process--was identified. "The team investigated various methods of fault-proofing or inspection to eliminate this potential failure mode," Layer noted. "But no effective conventional methods were identified."

Ausco then opted to examine different technologies that could meet its requirements, and machine vision systems came to the fore as an option. Machine vision systems are a growing segment of manufacturing technology in which digital optical systems and imaging programs are used to visually inspect components and subassemblies and even finished products to ensure complete assembly quality. An increasing number of manufacturers in industries such as automotive, electronics and semiconductors have adopted machine vision systems to provide high-speed, high-magnification visual inspections. While vision systems do not in all cases possess the discernment and capability of human inspection, they are also not subject to the same problems as human inspectors, such as distractions, illness, etc.

Ausco investigated machine vision systems and suppliers and found what appeared to be an excellent option in Cognex Corp., a Natick, Mass.-headquartered supplier of machine vision technology. The company's DVT Intellect vision systems can be used to automatically identify products, inspect for defects, gauge part dimensions, and guide robotic equipment at up to thousands of parts per minute.

Cognex provided a demo system incorporating a camera and a computer. The camera inspects the assembly and feeds the information to the computer. The computer has a user-defined inspection program that uses key parameters as a benchmark. If the benchmarks are not present or not correct, the system notifies the operator of a fault. "Essentially, it is a visual inspector that never gets tired, never becomes distracted and never gets bored," Layer noted.

After reviewing the vision technology and working with some of its own components through it, Ausco realized that a machine vision system could be a valuable tool for its assembly process. The company sent several components back to Cognex for further evaluation. Cognex developed a report and a quote for a vision system.

Along with that, Ausco engineers attended a two-day training seminar in which they learned basic vision applications, how to write inspection programs in the DVT Intellect software--the programming is designed to be similar to Windows--and how to physically set up the system. After returning from the seminar, Ausco began installing its vision inspection system.

The company saw a range of potential benefits to the system well beyond its original concerns, Layer indicated. "Not only can the system look for missing ball bearings in the brake, but it can also inspect for other items," he said. "These inspections remove manual inspection operations, saving time, improving throughput, and increasing accuracy and quality."

To take advantage of those additional capabilities, Ausco widened the scope of the project and began using the vision system to inspect for seven different assembly errors in the ball ramp calipers--missing ball bearings, upside-down brake pads, incorrect stationary actuators, missing inboard sleeves and incorrect levers.

The vision system was operated in a prove-out phase and the equipment performed flawlessly. "It proved 100% accurate on identifying rejections on incorrectly assembled brakes and 100% accurate on acceptance of correctly assembled brakes," Layer said. "Since its implementation, thousands of assemblies have been looked at by the vision system. It has caught two assemblies with upside-down stators and one unit with a missing ball bearing.

"One of the most important features of this system is its ability to watch and identify problems with new employees," Layer added. "With growth in sales, Ausco has hired new employees. With any new employee, there is a learning curve. As the new employee is learning, the vision system signals their mistakes. This makes vision an excellent safety net for new hires. It not only is a tireless inspector, but it is also a tireless trainer."

The vision system is now an integral part of Ausco's manufacturing infrastructure. "With the understating and implementation of the vision system," Layer noted, "Ausco now has yet another tool to use in its continuing efforts to maintain its position at the forefront of off-highway braking systems."
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Publication:Diesel Progress North American Edition
Date:Aug 1, 2007
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