Engine rings inspection
Case History Puffin Automation
The application goal is to detect surface defects of engine rings of different sizes (over 1500 parts), especially defects such as small cracks or voids as small as 200 μm located anywhere on the inner diameter. The rings range from 25 mm to 76 mm in diameter and 4 mm to 20 mm in height.
Opto Engineering® PCHI series is the perfect solution to image the inner surface of objects in one shot, thus eliminating the need for part rotation and speeding up the inspection process. A wide range of hole diameters (from 10 mm to 120 mm) can be easily inspected. Coupled with OE high power dome or ring lights and high performance LED strobe controllers, these lenses are perfectly suited for high speed inspections with exposure times as low as tens of microseconds. Cylinders, cones, holes, bottles or threaded objects are just a few examples of the items that can be inspected.
The solution
The system developed by Puffin Automation is based on several different preset configurations so that cameras, lighting and optics are automatically positioned for each unique inspection step. Once a particular configuration is loaded, cameras, lights, focusing and part positioning are all automatically adjusted to ensure that the best image is captured for each part. There are more than 120 parameters associated with each part, including light position and intensity, camera position, exposure, regions of Interest (ROI) location and size, etc. Thanks to the large view angle (>82°) and innovative optical design, PCHI023 is in fact compatible with a wide range of hole diameters (from approximately 10 mm to 120 mm) such as cylinders, cones, holes, bottles or threaded objects. The whole system consists of six vision stations that check for defects on the internal surface, on the outside surface, on the top surface, the concentricity of the part and (after the part is flipped) also on the bottom surface. For the inspection of the inner surface Puffin Automation selected Opto Engineering PCHI023 hole inspection optics for 2/3” detectors and 360° inside view in perfect focus.
For this specific inspection task, PCHI023 is used together with a 5 Megapixel monochrome camera (2448 x 2050) and with two different lights to properly illuminate the parts: a backlight positioned underneath the conveyor belt and a dome light positioned over the top of the part. Both lights were selected in blue color because short wavelengths are scattered more easily than longer ones (such as red) and are therefore more suited for scratch and surface inspection where they provide better contrast, as in this case with metal engine rings.
Why Opto Engineering®?
In the previous inspection system, line scan cameras were employed to inspect the inner and outer surfaces of the part: each part had to be rotated in front of line scan cameras using large, costly and time consuming rotary disks. Opto Engineering PCHI lens eliminated the need for part rotation speeding up the whole process. Additionally PCHI provided the largest viewing angle (> 82°) when inspecting inside the part diameter so that defects were clearly focused and identified. Thanks to PCHI lens, parts could be inspected continuously without having to actuate a probe inside the part to find defects and stop the conveyor belt.
