Vision the Smart Way

Experienced automation specialists are accepting the maturity of machine vision technology and its suitability for the shop floor, says Ajay Varma.

Some of the most loyal users of machine vision were, earlier, also its fiercest critics. Before the advent of specialized inspection systems, these experienced and skillful production and quality managers could effortlessly automate the most complex of inspections using not much more than a handful of sensors. The very mention of using a camera instinctively drew a sneer from these automation stalwarts.

Of course, it hardly helped that the primitive vision systems of that time looked menacingly complex, and occupied unacceptable amounts of space. In their eyes, the enormous price disadvantage of a vision system could never be offset by an increase in reliability, no matter how great the camera sales person claimed this gain would be. It was only whenthey started encountering situations where sensor based solutions were impractical or impossible, didthey start giving machine vision a serious thought..

Over time, however, the cost of a vision-based inspection system has dropped steadily. Vision systems are also increasingly infused with design that is sensitive to the needs of the factory floor. The day is not far when vision systems will offer full functionality with simple push-button operarability. With these developments and with the visibility of better products on the horizon, experienced automation specialists are finally accepting the maturity of machine vision technology and its suitability for the shop floor.

Becoming feasible
One of our clients recently shared with us one of its initial experiences with vision-based inspection. This anecdote shows how manufacturers eventually realize that the strength of machine vision lies specifically in addressing applications that were previously declared unfeasible due to either price or reliability constraints.

The client in question is an export-driven manufacturer of small motors, and consequently, it is of the topmost priority to every one of their production line managers to ensure that the quality of the products measures up to the high standards of their customers.

In this case, the need for an automated inspection system was established when quality inspectors noted that one of the parts of a motor assembly, a small printed circuit board (PCB), was particularly prone to operational defects.

The root cause of the defect was traced back to an operation where a thin coating of glue is applied onto the surface of the PCB. A later operation, the assembly of a heat-sink fixture, depended critically on the correctness of this operation. Any unevenness in the application of glue, or even the deposition of glue directly onto the central IC, resulted in an inability to position the fixture correctly.

Although this defect was instantly recognizable visually by the operator, it was surprisingly difficult to automate the component’s inspection using conventional sensors. The inspection requirements were further complicated by the fact that the appearance of the glued surface was markedlydifferent before and after drying.

Vision solution When our engineer was called to the scene, it was immediately evident to him that the inspection would have to be vision based. Samples of good and defective assemblies were sent to the Application Engineering team, where a feasibility study identified a smart vision system as a suitable solution.

Smart vision systems do not require the presence of a computer after the configuration stage, which makes them ideal for the conditions that exist on the shop floor. Also, since programming is generally a simple drag-and-drop affair, a basic training usually proves sufficient for the system operator.

Both these features were greatly appreciated by the customer, and the automated inspection system was speedily commissioned. Needless to say, after this incident, the manager started reviewing every application that had earlier been deemed infeasible, in order to see whether vision could help him where other conventional systems had failed.

We are glad to report that he is currently delighting his global customers as well as his senior management by continuously cutting production costs, while simultaneously increasing the reliability ofhis line.

Getting smart
Many a time, machine vision loses out to other sensing technologies due to the perception of a steeper learning curve in understanding the technology. Modern smart cameras like the Spot-It v2 – an integrated unit which houses both the camera and the processor – are fighting this perception by introducing simpler and more intuitive programming interfaces, and by consciously designing the hardware to be operator-friendly.

It is now very possible for any manufacturer to train a small team of his engineers in machine vision and reap the real benefits of this technology - flexibility, reconfigurability and ease of integration. Vision-based poka-yoke provides manufacturers with a versatile tool to instantly detect defects at source, in a variety of different operations, and also to cut wastages arising out of value addition on defective products.

Which makes it all the more important to remember, that the next time you get a chance to get trained in machine vision, make sure you spare some space in your toolbox.

Ajay Varma, is Architect - Product Marketing, Soliton Technologies, an Indian manufacturer of machine vision systems.

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Clarity for Glass Inspection

A smart camera system proves to be an economic and effective solution for glass bottle inspection.

Thorsten Gonschior, president and founder of Spectral Process, was confident he could provide a lower-cost alternative when one of his customers asked him to retrofit an existing glass bottle inspection machine.

“That original system had an optical component to locate the defects, but no processor,” he says. “Since the component was no longer available on the market, we thought about completely replacing its part of the inspection process with a scalable subsystem.”

The subsystem takes over inspecting the sealing surface at the bottle’s opening. Bottle openings are particularly critical because any defect in the sealing surface can prevent the cap from making an airtight seal. When that happens, carbonated beverages go flat, and burrs, chips, or sharp edges may injure consumers.

A number of technologies can evaluate bottle-opening quality. Some plants, for example, rely on mechanical inspection systems that directly contact the container, such as filling the bottle with compressed air and plugging it with a gauge to look for leaks. Those techniques, however, are slow, marginally reliable, and potentially can damage bottles.

While high-end, camera-based inspection systems can catch defects more reliably, Gonschior explains that many glass manufacturing plants worldwide cannot afford to spend hundreds of thousands of dollars for a high-end inspection system. Even though they are under pressure to maintain quality control, cost is an issue.

Manufacturers are caught between a rock and a hard place. They must maintain high quality standards. They also must improve the production process if they want to maintain a competitive edge. On the other hand, they cannot allow highequipment costs to make operations unprofitable.

Finding an opening
These considerations motivated Gonschior to develop his Opening Inspector system. It uses advanced machine vision technology to check openings of hollow glass containers (like bottles) for cracks, inclusions (bubbles), and pressed artifacts.

The system can be retrofitted for a wide variety of glass inspection machinery. It consists of a Matrox Iris P-Series smart camera, a custom-designed light source, and a power supply.

Using a smart camera eliminates a lot of what Gonschior calls “additional engineering” – developing the housing, computer, electrical connections, etc. Software functions built into smart cameras can also reduce software development costs – a major component of embedded-system cost.

As the core of the system, the smart camera performs visual inspection while acquiring data from other sensors, and controlling actuators. The software application uses a number of modules in the Matrox Imaging Library (MIL), in particular blob analysis, edge finding, and metrology. These functions are critical to measuring inner and outer diameters, as well as locatinginclusions, cracks, and over-pressed structures.

Further integration
A number of complex subsystems can be integrated into the Opening Inspector with Ethernet connections. For example, Gonschior is planning to use a 2D actuator with high resolution to control a labeling arm. “Integrating network-capable third party devices into the Matrox Iris network is easy and straightforward,” notes Gonschior.

“Glass has a bad reputation when it comes to illumination,” notes Gonschior. Indeed, both the material and its shape create illumination challenges.

Gonschior developed a custom lighting solution to resolve many of these issues. The key was a diffuse light that concentrates reflections at damaged spots. “It sounds easy, but the development was anything but,” he recalls.

Gonschior says smart-camera technology makes it possible to offer the system at a fraction of the cost of many competing glass-inspection systems. Moreover, the scalable design makes it possible to simply add cameras to accommodateincreased throughput.

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Visions of Safety

Machine vision creates a sophisticated 3D imaging technology solution that trumps traditional guarding technologies for flexibility and reliability.

Unauthorized human activity is one of the most common causes of machine-safety system failures. For example, poorly designed safety systems often make maintenance and repair activities difficult or impossible such that after attempting to work within poorly designed safety-system constraints, workers may disable the safety system to complete their tasks more efficiently. The safety system is therefore disabled just when it’s most needed. Resulting accidents and injuries then count as safety-system failures.

Recognizing that traditional mechanical and barrier methods for machine guarding are only as safe as the people using them, machine safety equipment maker Castell decided to used machine vision to create a sophisticated 3D imaging technology solution that trumps traditional guarding technologies for flexibility and reliability. Called the QuadCam system, the company says it virtually eliminates the potential for human error andtampering.

Defining zones
This vision-based safety system allows users to define warning and shutdown zones through a computerized user interface. When a “warning zone” is breached, a controller provides visual and audible warnings to workers and sends a signal to the machinecontrol system to slow the equipment to a “safe speed.”

Safe-speed systems constrain machine movements to speeds slow enough for humans to escape accidental collisions. Humans can react within about a quarter second to perceived danger from moving equipment. Machine structures should move slowly enough so that a human working in close proximity can see the movement, search his or her surroundings for a safe exit, and get out of the way before being struck.

If the person or object (such as an automated forklift) enters a “shutdown zone”, the system sends a signal to halt the machinery. Warning and shutdown signals are sent within milliseconds of an intrusion, fast enough to prevent accidents and equipmentdamage. Once shut down, machinery can’t be restarted until thedetection zone is clear of unauthorized objects and people.

View from above
Castell’s 3D detection technology triangulates images from four smart cameras to identify objects and people moving in and around the work zone, distinguishing between one, two, or more targets, with real-time tracking of all targets within the system’s field of view.

Mounted high above the machinery, the imagers can view multiple potentially dangerous areas of human and machine interaction, and are tamper-resistant.

By combining cues based on object size, shape, and movement, the detection system can distinguish between targets representing potential safety issues, and unimportant background objects. Ignoring background objects avoids nuisance alarms, which is another major cause of safety-system failures.

The company says its system is designed for user flexibility. During initial installation, plug-and-go harnesses enable simple imager installation, wiring, and even relocation of imagers when necessary. Reconfiguring the system is simple via a Microsoft- Windows-based PC interface. Warning and shutdown zones can be quickly redrawn with the click and drag of a mouse.

When mounted 3.3 meters above the floor, one imager can protect a zone measuring up to 2.4 m x 3 m. Up to 10 imagers, creating 10 protection zones, can be managed by a single controller monitoring up to 72 square meters. Smart camera technology, which makes it possible to distribute image processing work whereit’s needed, makes the system feasible.

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