Introduction to basic industrial X-ray techniques

Tasks
Investigate industrial objects for

· Cracks in welding joints
· Defects and porosity in castings
· Precision/completion of assemblies
· Character and type of material etc.

Goals
· Assurance of the quality of the product
· Increasing the reliability
· Control and optimisation of the process
· Cost reduction by means of automation

Solution
X-ray inspection in development, manufacturing and service.

Depending on the requirements of the customer, an X-ray inspection system may be combined of the following basic modules:

· X-ray source with necessary power supply
· Detector for X-ray detection/image generation
· Manipulator for positioning of object in X-ray beam
· Radiation protection cabinet
· Controller for requested image-manipulation, analysis, and control of
 manipulator

X-ray source
The X-ray systems are basically distinguished by the type of X-ray tube, being utilised in the systems; especially the so-called focal spot size is of importance. This decides what resolution can be achieved, i.e. how small an anomaly may be recognised. YXLON International has a variety of different X-ray tubes in its product range, ranging from micro-focus tubes for inspection of electronic components with small details up to very powerful tubes with high penetration ability for inspection of complete containers.

Detection system
X-rays penetrating the object must be detected and displayed. An image of the object must be created in order to analyse the details inside. This image is created by means of a so-called detector, e.g. an image intensifier system. We are all familiar with the use of X-ray film. However, the use of film is only necessary when heavy penetration has to be done over a period of time under difficult environmental conditions, such as pipe-line inspection, in ship-building or power plants. In serial production a real-time image is often needed.

Industrial serial production as, for instance, in the automotive industry, asks for a fast, digital detector which can create an image with adequate quality for computer-aided analysis and diagnosis. YXLON International is the leading supplier of fully-automated X-ray inspection systems. The latest detection technology combined with most powerful computer technology is used.

Manipulators
The object to be inspected must be positioned and moved within the beam from the
X-ray tube – the object must be manipulated until the best position for inspecting a certain area is found. The characteristics of the manipulator are very important, as it must be able to move fast, and to handle the object size- and weight-wise, and the precision of the positioning must be very accurate. In addition to standard solutions for frequent part sizes, YXLON International also designs and supplies customer specified system solutions.

Radiation protection
The radiation shielding cabinet is indispensable. It serves the protection of the operators as well as the environment against risk of radiation. It is the aim of YXLON International always to be well below the permissible limits for radiation doses. And this is always the case with any X-ray solution delivered.

Innovative methods
Besides the above described ‘Through Transmission’ X-ray technology, which requires an imaging or detection device on the back of the object under examination, there are innovative physical and mathematical methods which offer additional, more detailed information. YXLON International consequently concentrates research and development activities on the exploration and further development of these new X-ray methods. One example is the so-called ‘Backscatter or Compton Technology’ which allows the ‘one-side’ inspection of an aircraft fuselage or wing for hidden corrosion. This innovation has awarded the ‘Silver Medal for Innovation’ of the German Industry. A further examples is Computer Tomography (CT) which is one of the new focus areas of YXLON International.

Computed Tomography
A wide variety of objects to be inspected can be examined using computed tomography (CT). Alongside non-destructive material testing, tasks involving measurement and geometric modeling can also be accomplished with certainty.

Using CT, defects in objects to be inspected can be depicted almost independent of their shape and size, thus enabling an assured analysis of both materials and defects. For example, the three-dimensional depiction free of overlapping segments makes it possible to clearly identify flaws. Results like these supply valuable knowledge for the further utilization of the inspected item within the production process. Above and beyond
that, the production process itself can also be reguided via defect recognition.

The basic setup of a CT system consists of an X-ray source for beam generation, a manipulator to position the object to be inspected, a detector to capture the radioscopic image and a computer unit for image generation (reconstruction), image depiction and analysis. In the case of computed tomography, radioscopic images of the object to be inspected are generated with the help of X-ray beams from several angles. Those images are subsequently computed to create a three-dimensional image. The manipulation system must therefore make sure that either the inspected object or the X-ray tube / detector unit can rotate around a 360° axis as well as be vertically adjustable. A high degree of precision and stability is necessary hereby in order to obtain reproducible images. Depending on the inspection task involved, either line or flat-panel detectors are utilized to record the image. With each rotation the line detector records absorption profiles of precisely one cross-section of the object. These profiles are then computed to create a highly accurate tomogram. After having scanned the entire inspection object, a compilation of the tomograms generated in this manner with respect to their positions is calculated to form a 3D depiction displaying a high detail identification factor. In contrast, with each rotation of the inspected object the flat-panel detector simultaneously records several cross-sections of that object. The multiple images are subsequently computed into a 3D depiction. This method enables inspection objects to be scanned as a whole and outputted as three-dimensional data models within the shortest of time spans.