Vision systems help seal success

At machine-builder Phasor (Sunderland, England), four separate vision systems have been integrated into one fully automated machine to inspect the surface of oil seals for shock absorbers. The rubber-molded seals are checked for scratches, marks and surface blemishes, inclusions, and imperfections.

A shock-absorber-seal inspection system incorporates four image sensors from Omron to inspect thousands of seals per day. (Photo courtesy of Phasor)

Peter Hage, Phasor's head of design, developed the system using the Omron (Schaumberg, IL) F150-3 vision sensor because of the device's surface-defect algorithm. In its final form, 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, three F150-3 cameras focus on the main seal lip, the main body, and the side of the seal.

Each camera views a 30° segment of the seal, and the spindle rotates around in discrete steps, so that the whole of the seal is viewed in a series of 12 images. The F150-3 uses pixel-counting techniques to detect imperfections of the seal in each of the 36 different images. Each image is analyzed in 110 ms.

Next, a second pneumatic transfer mechanism inverts the seal onto another 12-step rotating spindle. A single camera searches the underside of the seal for surface blemishes. The machine is set so that both spindles are loaded and analyzing seals simultaneously, achieving a cycle time of less than 4 s per seal. This requires analyzing 48 different images in 4 s.

So that each seal is associated with the correct 48 images, Omron's Vision Composer marries image and object data. Four F150-3s are controlled by an Omron CPM1 microcontroller. Image-analysis data from the cameras are fed to an Omron CQM1 programmable logic controller that controls safety switches, conveyor drives, and the systems' pneumatics. Omron's CQM1 also controls a pneumatically powered reject gate to divert any defective seals to a recycle bin.