Machine Vision and
Flexible Manufacturing

Rapid changes in product lines and manufacturing environments
demand greater flexibility on the line—especially when it
comes to machine vision.

Evan Lubofsky

How flexible does vision have to be? The answer, of course, depends on the user’s particular requirements. For instance, one manufacturer making products with short life cycles may need a vision product that can accommodate frequent product changeovers on the fly, while another may require a product with a broad set of software tools for solving a variety of tasks. Clearly, a number of factors must be considered when integrating vision into a flexible manufacturing line.

Breadth of Vision Tools

In flexible manufacturing, the inspection problem you are solving today might not be the same one you will need to solve tomorrow. Whether it is a result of product design changes, or the need to inspect for new types of defects on the same part, the picture is constantly changing on the line and the vision product of choice should be able to accommodate these changes (see Photo 1).

Photo 1. The In-Sight processor features an advanced DSP for high-speed image processing and a compact, low-profile design for flexible mounting options. The industrial-hardened enclosure provides a standard VGA output for live video display, and communication ports for connectivity to PLCs, robots, and other factory equipment. In-Sight also includes a high-performance digital camera with built-in triggering port and electronic shuttering, and a handheld control pad. (Photo by Joe Greene.)

For example, you may need to verify the presence of a white feature on a black part. The vision product you are considering might offer only a few vision tools, but it handles your inspection task reliably and without problems—during the evaluation period. Once the parts are deployed on the production line, though, the white feature isn’t so white and the black surface of the part is now shiny. All of a sudden, the application requirements have changed and the basic tools that worked just fine during evaluation are no longer up to the job.

Choosing a vision product with a wide range of image processing and analysis tools gives you more application headroom to contend with changes introduced at runtime. You will also be able to handle future, potentially unforeseen changes such as the use of new materials to produce the part, resulting in different part surface colors, textures, and characteristics.

Configurability

While many programmable vision systems offer a great deal of flexibility in developing applications, many potential users of machine vision do not have programming experience. Systems with point-and-click user interfaces help shorten the development cycle but typically sacrifice flexibility in order to make things easier for the user.

Vision interfaces that combine the flexibility of programmable systems with point-and-click simplicity work best in flexible manufacturing environments. One example is a new vision spreadsheet interface offered with Cognex’s In-Sight vision sensor, which gives those with only basic spreadsheet skills the ability to easily configure vision applications without writing a line of code. It enables the user to select vision tools and parameters from menus, and automatically enters tool results into worksheet cells. Cells can then be easily linked together to perform the desired task (see Figure 1).

Figure 1. In-Sight, a new type of machine vision sensor, provides vision technology in an affordable, stand-alone package that requires no programming or PC. The sensors can easily be deployed at various key points on the manufacturing line, allowing personnel to monitor processes and quickly respond to problems as they arise. A comprehensive library of Cognex vision software tools and a vision spreadsheet interface enables fast, easy application configuration. The interface menu text can be displayed in a variety of languages including English, Japanese, and French.

In addition to simplifying things during application development, configurable interfaces enable users to rapidly respond to new product changeovers at runtime. Product changeovers have typically meant having to take the time to reprogram the vision system to recognize the new part. Configurable interfaces allow users to make modifications to the application, on the fly, without the downtime associated with reprogramming.

Robust Pattern-Matching Capability

Many vision systems have difficulty in recognizing parts, or in matching patterns, if the objects being inspected rotate from their original “trained” position, or their appearance changes due to variations in optical scale, poor lighting, or overlapping parts. Manufacturers have typically overcompensated for these problems by ensuring that parts are well fixtured on the line and that lighting and other environmental conditions are closely controlled. Mechanical fixturing and elaborate lighting systems are often extremely costly, though, and require extensive maintenance. The result is reduced flexibility.

Vision products with robust pattern matching tools can loosen the strictures on fixturing and lighting requirements and can adapt to constantly changing conditions on the line. The benefits are greater flexibility and reduced manufacturing costs.

Stand-Alone Operation

Vision products featuring a stand-alone form factor can be advantageous in a flexible manufacturing environment. To be considered truly stand-alone, the vision product should not require the use of an external PC during application development or at runtime. Such stand-alone products typically feature a compact, low-profile design that provides manufacturers with great flexibility with respect to mounting options.

Affordability

Many manufacturing processes could benefit from automated inspection, but the high price of vision systems has often proved a deterrent. Where vision systems are used, they are often deployed at the end of the line after a product has undergone numerous value-adding stages of production. Vision sensors, because they are affordable, lend themselves well to flexible manufacturing. Instead of being reserved for end-of-the-line part checking, vision can now be deployed at various key process points along the way. This gives manufacturers great flexibility in terms of places on the line to use vision, while enabling line operators to carefully monitor the manufacturing process further upstream and respond quickly to problems as they arise.

Summary

While there is no exact recipe for what constitutes machine vision flexibility, products that best complement a flexible manufacturing line typically demonstrate a few key characteristics:

• They are adaptable to changing conditions on the line, whether they are product-related or environmental.

• They are typically more accessible to a broader pool of manufacturing engineers from both a cost and usability standpoint.

• The most flexible vision platforms are those that, due to their compact, stand-alone form factor and low cost, can be used virtually anywhere in the manufacturing process where value is being added.