Assembly in Action: Machine Vision Solves Seal Inspection Problems
Phasor Ltd. (Sunderland, Tyne & Wear, U.K.) specializes in applying vision technology and has completed a state-of-the-art inspection machine that checks every surface of shock absorber seals. The seals are rubber moldings, and they are checked for marks and surface blemishes, inclusions and imperfections, such as incomplete moldings.
"This machine will check literally thousands of seals every day, each getting a thorough going over," says Peter Hage, head of design at Phasor. "It would have been easy to design and build a machine had cost and cycle time not been part of the equation, but as they were key criteria, we knew we would have to come up with a radically new solution."
Knowing that Omron Electronics (Schaumburg, IL) had some low-cost vision technology, Hage invited Omron to a brainstorming session, in which some concept designs would be developed and explored. "We had used Omron's F150 vision sensor in the past and were pleased with the results. This is an order of magnitude cheaper than a full-blown vision system. But it achieves fantastic results in applications where the operating environment is virtually stable," says Hage.
Until recently, Phasor's requirements for high-speed 3D inspection would have required a top-flight vision system. However, Omron suggested using its F150-3, a third-generation enhancement of the F150. Most importantly to Phasor, the F150-3 includes a high-performance surface defect algorithm.
Phasor's machine feeds individual seals along an input conveyor to a pneumatic arm that transfers them one at a time to a rotating spindle, which forms the first of two inspection stations. Here, one F150-3 focuses on the main seal lip, one on the main body and one on the side of the seal. Each camera views a 30-degree segment of the seal, while the spindle rotates around in discrete steps, so that the entire seal is viewed in a series of 12 images.
The sensor uses a pixel comparison technique to detect imperfections of the seal in each of the 36 different images. Each image analysis is executed in less than 110 milliseconds. After this, a second pneumatic transfer mechanism inverts the seal onto a 12-step rotating spindle. A camera then searches the underside of the seal for surface blemishes.
Hage was concerned about having to program the controlling software for the image analysis so that each seal was associated with the correct 48 images. Simultaneous with the launch of the F150-3, Omron introduced Vision Composer software that automatically marries images and objects.
The four sensors are controlled by an Omron CPM1A microcontroller, and the image analysis data is fed from the cameras to an Omron CQM1H programmable logic controller that controls the safety switches, conveyor drives and pneumatics. The CQM1H also controls the pneumatically powered reject gate, which flies open to divert any defective seals as identified by the image analysis to the recycle bin.
"Not only did Omron have the right vision technology for our needs, but its control and automation equipment suited us too," says Hage. "We are scheduled to make a series of these machines for installation around Europe and possibly elsewhere. By specifying Omron throughout, we can be confident that we will get technical support no matter where the machines are located."
For more information about vision systems, call 847-843-7900 or visit www.omron.com/oei.