How to automate optical part flaw detection
As part quality has gone up, it has become essential to provide not only the most complete dimensional data on a given part, but also other detectable data like simple contamination, porosities, scratches, discolorations, cracks, and other types of potential surface defects… especially in automotive powertrains. In the past, flaw detection has been accomplished using simple visual methods like the naked human eye, or even manual bore scopes using specialized video equipment.
Automated flaw detection is a field that has been growing steadily over the last decade, due in no small part to the inherent limitations of using manual visual inspection. One major limitation of manual visual inspection generally involves checking small sub-sections of the parts produced, where-as automated optical solutions can perform 100% part inspection on 100% of the parts produced. Another major factor in the growth of automated flaw detection, is that newer style optical systems can also detect surface flaws invisible to the naked eye, far faster than a trained operator can with a manual bore scope.
When automating your part flaw detection, as with any quality endeavor, the first step starts with determining what exactly needs to be quantified. In this case what constitutes a flaw vs. an acceptable manufacturing anomaly. The minimum size of an unacceptable defect usually depends on the location and function of the surfaces inspected and can dictate the minimum resolution of the device required. Consideration must also be given to background noise (machining, material, etc.) and contamination.
Now that you have determined what constitutes a surface flaw, you have to decide on how to evaluate it using the available optical solutions. Optical technology has drastically changed in the last decade, including the development of higher resolution CMOS sensors, faster data point acquisition, 3D technology, even sensor sizes that allow evaluation of diameters down to 5.5mm.
Cylinder bores are a good example because surface finish characteristics are a critical component in achieving optimal engine performance. Using the latest in CMOS sensor technology, the IPS-B100 can scan a bore in high speed, creating an undistorted hi-resolution image of the scanned surface. Depending on the ratio of pixels to surface area scanned, defects as small as 50um can be detected, although consideration must be given to surface structure (machining, material, etc.) and contamination. This technology can be utilized on other manufactured parts as well, including crank cases, transmission housings, steering housings and piston rods. In addition to standard sensors, thermal spray on cylinder liners add a whole new element, leading to the development of a sensor system for evaluating dovetail micro profiles in cylinder bores.
Flat machined surfaces have been getting some attention from optical flaw detection as well. The IPS F100 3D has been designed to inspect flat surfaces, such as engine block decks, cylinder heads, BMI liners and more. This technology uses a unique high contrast image production called “Shape from shading” in identifying valleys and raised areas, as well as adaptive, dynamic masking to reliably establish the edge positions. This allows the generation of a very dense 3D point cloud that permits the detection of common surface defects as well, like pores, scratches, hit marks, edge distortion, staining, and more.
Investing in automated optical flaw detection technologies that offer a wide degree of flexibility and speed, allow manufacturers to perform 100% part inspection in a fraction of the time possible using manual systems, improving your manufacturing process and your part quality at the same time.
By: Scott Lukomski, Sales Director