Five Edge Inspection Techniques in Machine Vision Technology

blue banner of digital colorful edges

Finding an edge is one of the most critical functions in machine vision systems, whose algorithms comb through the pixels in a digital image in search of lines, arcs and geometric shapes. Software translates this data into edges, which tell machine vision software which areas to focus on and which ones to ignore.

Thus, edge-inspection tools bear a substantial responsibility for the accuracy and efficiency of machine vision systems. The fundamentals of edge inspection tools illustrate some of the core functions of machine vision.

How Edge Detection Works in a Factory Setting

Here’s a common edge-inspection scenario based on Cognex’s machine vision software:

A completed piston assembly must be inserted into a V-8 engine block. A machine vision application takes a photograph of the piston assembly and uses machine vision algorithms to identify its edges. Another picture finds the edges within the engine to block that reveal the piston assembly’s installation location.

Edge-inspection tools are configured to direct the machine vision system to focus its attention on specific areas of the piston assembly and engine block while filtering out everything else. This is crucial because computer processors must scan every pixel within an image, which requires processing time and energy. The system runs best if it scans only the required pixels.

In our example, a machine vision system uses edge inspection data to set up a quality-control application that scans images of the piston assembly and engine block for evidence of defects. Once they pass inspection, they proceed down the assembly line to a robot arm that uses edge-inspection data to tell the robot exactly where to place the piston within the engine block.

Operations like this play out in almost infinite variety, given the widespread prevalence of machine vision technology in distribution centers and factory automation.

5 Tools for Acquiring Accurate Edge Inspection Data

A machine vision system sets up a series of parameters to determine if an item being scanned should progress through the production environment or be rerouted to an area for addressing defects. Every item photographed or scanned gets a pass or fail rating.

Edge inspections can be configured to establish tolerances. Any object falling outside these tolerances can be rejected, while everything within the tolerances passes.

To visualize how edge inspections work, imagine a modern-day factory creating reproductions of old-fashioned wagon wheels, which have three principal parts: the outer rim, the spokes and the hub. Edge inspection parameters are critical to using industrial robots to automate the manufacturing process.

These five edge inspection techniques come into play:

  • Distance. In a wagon wheel, the distance between spokes, rims and hubs must fall within tight tolerances. Edge inspection tools measure the distance between these components in a scanned image, enabling both quality control and alignment for robotic production.
  • Angle. Each spoke of the wagon wheel has to be installed at an exact angle. An angle edge inspection tool gives the robot accurate guidance on spoke alignment.
  • Circle diameter. Manufacturing or distribution flaws might deliver the wrong rims or hubs to the robot. A circle diameter edge inspection measures the distance from the center to the edge, creating data for flagging production errors.
  • Circle concentricity. The wagon wheel’s rim and hub share the same center, which makes them concentric. A circle concentricity edge inspection helps the robot align the rims and hubs.
  • Radius. The radius of each rim and hub provides more data to ensure that the robotic automation gets them into precise alignment.

Manufactured components as simple as a wagon wheel or as complex as a smartphone circuit board all benefit from these kinds of edge inspection applications.

Choosing the Right Edge Inspection Technology 

At Cognex, we’ve been perfecting the art and science of machine vision for decades. Our InspectEdge tool is one of the core assets in our machine vision software suite, which was designed to make it easy for anybody to set up a vision application, even if they don’t have advanced certifications or college degrees.

Other tools in our software suite accomplish essential tasks like bead inspection, pattern matching, identification and image processing. Whether you’re running a distribution center or automating a factory environment, these tools will give you an edge in quality control and efficiency.

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