Digital radiography (DR) allows the volumetric inspection of the part under inspection and usually reveals more information about a part than any other inspection technique. Just over two years ago Dr Mihai Iovea of Accent Pro 2000 s.r.l., and co-ordinator of two European-funded consortiums AutoInspect and PlastronicsSpec, invited TWI Technology Centre (Wales) to become involved in the radiography development of two completely different inspection applications aimed at different industry sectors.
The AutoInspect system has been developed for the inspection of powder metallurgy (PM) parts, while the PlastronicsSpec system has been developed for the plastic electronics market.
In the PM industry, PM parts can suffer from porosity and cracking; hence the need for an automated inspection to ensure 100% quality of parts. The use of digital X-ray radiography allows parts to be inspected without being destructed.
The AutoInspect consortium has developed a digital radiographic system for the online inspection of sintered powder metallurgy and metal injection moulded parts.
Side view of the AutoInspect prototype automated DR inspection system
The main features of the AutoInspect system are:
- a digital radiography inspection technique, able to inspect powder metallurgy parts in seconds
- embedded time-delay integration (TDI) linear X-ray detectors that allow the supply conveyor to run continuously, while a row of parts is simultaneously scanned. The TDI technique creates very low-noise X-ray images with resolution up to 10μm pixel size, depending on X-ray set-up magnification
- a dedicated image analysis algorithm for the automatic detection of defects recognition with pre/post processing and an enhancement algorithm are used to sentence good/bad components.
This technique has been developed to detect small cracks, flaws and density variations in-line during the manufacturing process of PM parts produced in a factory environment.
AutoInspect X-ray image showing porosity in PM ring samples from the automotive industry. Red circles indicate defective areas
For the plastic electronics industry, organic light emitting diodes (OLEDs) used in digital displays need to be checked for quality. Specifically, the end user in the PlastronicsSpec consortium produced OLEDs by inkjet printing. This OLED inkjet printing process can result in defective pixels, resulting from cracks, chips, pin holes and misaligned layers. The objective of the developed PlastronicsSpec system is to perform rapid and high resolution inspection of printed plastic flat panels or reel-to-reel flexible electronics sheet using real-time digital radiographic imaging. This enables the automatic detection and instant rejection of defective products with minimum wastage and the elimination of human error in data interpretation.
The main features of the PlastronicsSpec system are:
- a microfocus X-ray source and a 2D flat panel digital detector which generates radiographs with up to 1.2µm resolution at high magnification
- prototype can accommodate a 600mm2 flat OLED panel and can be adapted to handle roll-to-roll (R2R) flexible electronic samples
- novel multimode signal processing options have been used to detect the smallest possible image differences. Various image filtering techniques have been integrated to achieve optimum pattern recognition and accurately size defects. The software allows automatic sentencing of parts as good or bad.
PlastronicsSpec system showing the X-ray source, digital detector and the OLED panel from OTS (consortium partner-SME)
PlastronicsSpec X-ray image of a flat OLED (red box indicates a defective area)
TWI Technology Centre (Wales) developed, optimised and automated the digital X-ray inspection based techniques for both projects. TWI first simulated the radiography environment to optimise the placement of the X-ray source and detector, surveyed the market for the appropriate source and detector, and finally procured the most suitable X-ray source and detectors for the intended applications.
The two applications could not be more different in terms of radiography. For the PM samples the team identified high energy (160-200kV) to penetrate the material, whereas for the OLED inspection the energies had to be low (55kV) to avoid being destructive to the OLED panels. For the PM parts the goal was to inspect defects such as cracking to 25μm resolution, whereas with OLED display inspection the requirement was to resolve flaws down to 2-4μm.
Project co-ordinator Dr Mihai Iovea thanks TWI and states that, because of the contribution of TWI and other collaborators, he is in a very good position to commercially exploit the completed prototypes.
TWI can develop one-off automated inspection prototypes and solutions for its Members. If you think you might have an inspection requirement where digital radiography can be deployed, or you need to inspect a component using radiography, please contact email@example.com.
More information about the projects can be found at www.autoinspectproject.eu and www.plastronicsspec.eu
The PlastronicsSpec project has received funding from the European Union under grant agreement no. 286531. The AutoInspect project received funding from the European Union under grant agreement no. 286007.
TWI Ltd (The Welding Institute)