X-Ray- It is an electromagnetic wave of high energy and very short wavelength, which is able to pass through many materials opaque to light. X-rays are like visible light waves like visible light but they have a higher energy level and therefore can pass through different materials. When an X-ray transmits rays through the human body and onto a film, bones, fat, muscles and other tissues absorb the rays with different degrees. Most X-rays have a wavelength ranging from 10 picometres to 10 nanometres, corresponding to frequencies in the range 30 petahertz to 30 exahertz (3×1016 Hz to 3×1019 Hz) and energies in the range 100eV to 200keV. X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays. Because of shorter wavelength and high energy X-rays can penetrate into the object can detect gaps and breakings, this makes X-Rays suitable for the non-destructive testing inn various domains. Like the optical NDT method x-ray can’t provide the colour image of the object, it can provide the black and white image.
Automated X-Ray Inspection System
Automated X-ray inspection (AXI) is a technology based on the same principles as automated optical inspection (AOI). It uses X-rays as its source, instead of visible light, to automatically inspect features, which are typically hidden from view.
Automated X-ray inspection is used in a wide range of industries and applications, predominantly with two major goals:
- Process optimization- The results of the inspection are used to optimize following processing steps.
- Anomaly detection- The result of the inspection to serve as a criterion to reject a part (for scrap or re-work).
While optical inspection produces full colour images of the surface of the object, x-ray inspection transmits x-rays through the object and records grey scale images of the shadows cast. The image is then processed by image processing software that detects the position and size/ shape of expected features (for process optimization) or presence/ absence of unexpected/ unintended objects or features (for anomaly detection).
X-rays are generated by an x-ray tube, usually located directly above or below the object under inspection. A detector located the opposite side of the object records an image of the x-rays transmitted through the object. The detector either converts the x-rays first into visible light which is imaged by an optical camera, or detects directly using an x-ray sensor array. The object under inspection may be imaged at higher magnification by moving the object closer to the x-ray tube, or at lower magnification closer to the detector.
Since the image is produced due to the different absorption of x-rays when passing through the object, it can reveal structures inside the object that are hidden from outside view.
Application of AXI
X-Ray inspection system is a method of NDT, and it had specific applications mainly in electronics manufacturing industry and automobile industry because of its high operational cost. With the development in technology and wider adaptation of the technology the operations cost reduced and it is being used in many industries like food packaging etc. The first applications started off in industries where the safety aspect of components demanded a careful inspection of each part produced (e.g. welding seams for metal parts in nuclear power stations) because the technology was expectedly very expensive in the beginning.
Now a days AXI has huge market in below mentioned fields
- Automobile Components
- Aluminium Die-Cast Components
- Pipe Weld Inspection
- Aviation Components
- Heavy Engineering Components
- Defence and Aerospace
- Ceramic structures and Vacuum Interrupter
In mass production of complex items (e.g. in electronics manufacturing), an early detection of defects can drastically reduce overall cost, because it prevents defective parts from being used in subsequent manufacturing steps. This results in three major benefits:
- It provides feedback at the earliest possible state that materials are defective or process parameters got out of control.
- It prevents adding value to components that are already defective and therefore reduces the overall cost of a defect, and
- it increases the likelihood of field defects of the final product, because the defect may not be detected at later stages in quality inspection or during functional testing due to the limited set of test patterns.