Industrial computed tomography
Industrial computed tomography ( ICT) - precisely here X-ray computed - (short: CT ) offers resistance to medical CT, which is mainly dealt in Article computed tomography, some significant differences. In the medical field is the object of investigation (the person) of relatively uniform size (about 1.5 to 2.0 m) and composition ( about 63 % water, a few heavy elements ). In the industrial sector that is not the case. Here objects from a few millimeters to many meters and homogeneous (eg pure metals ) and completely inhomogeneous components must be (eg fiber composites ) were investigated and displayed in three dimensions. Therefore, the requirements for industrial CT systems, and their types are sometimes significantly different and diverse compared to medical CT systems.
The industrial CT can be, depending on the criteria used to classify a variety of ways. Commonly used are divisions on the geometry of the recording system or detail detectability of the systems.
- 6.1 Macro - CT
- 6.2 Micro-CT
- 6.3 Sub - Micro-CT and nano - CT
Operation
A special feature, in which the industrial CT differs from the medical, lies in the often different imaging geometry compared to medical systems. There, the patient is usually cooperative and motionless, X-ray source (s ) and detector ( s) being coupled to one another go around it. In the industrial sector, where yes only inanimate objects have to be examined, x-ray source and detector can be fixed in position and only the object under examination be rotated, which is mechanically simpler.
Sequence of an industrial computer tomography
When using the industrial computed tomography of the specimens can be started before the production of the components of the preparation of the metrological evaluation and measurement. The CAD data used by the development department to design the component for the creation of the ICT test plan to be used by determining the reference and alignment points of the component and the individual measurement points are defined. Once the first seriennah produced component is completed, it is scanned into the ICT system, converted into 3D volume data and read into an evaluation software. Then, the 3D model of the scanned part is aligned with the CAD design data about the software and performed the measurement using the test plan already created. The measurement errors are displayed in a log, shown in different colors according to their degree of deviation and statistically analyzed as desired.
Mapping the entire inner life of a component
With the ICT analysis, the user sees the complete interior and exterior geometry of its workpiece in all details. The slightest deviations and component faults are accurately located. The range of analyzes ranging from wall thicknesses and Porositätsanalysen, the defect and assembly control to verification of properties that is not possible with conventional measuring methods. You can now, make measurements to determine precisely even soft materials such as elastomers or rubber parts. Due to the detection and measurement of the undestroyed test specimen and volume of air inclusions, holes or fluids are measured using the ICT.
Finite element calculation on reverse engineering possible
The tomographic measurement of the component also offers a further advantage. With the resulting data can be first performed at the "real" component by reverse engineering a finite element calculation. That is, the resulting ICT data of the real component are converted into CAD data and then determined using the FEM weaknesses. This was previously only possible on the constructive and freely created process-related errors CAD data.
View the geometry of the recording system
Two-dimensional CT
A single layer of the object is analyzed and reconstructed. This is done by all sides by beams and detection of X-ray radiation with a line detector. The X-ray source is sending the a fan beam. The layer structure of the object is reconstructed numerically using the recorded X-ray projections.
Advantages:
- High detail resolution
- Little interference by scattered radiation
Cons:
- Long measurement times for volume measurements
- The object must be penetrable by all sides
This method is mainly used for:
- Maßhaltigkeitsprüfungen
- Error checking
- Dimensional Measurement
Three-dimensional CT
Here, the entire volume of an object is analyzed by irradiating all sides. The X-ray source emits a cone beam is detected with a flat detector ( flat panel, flat panel detector ).
Advantages:
- Direct generation of a volume model
- Short measuring times (down to 25 s for a volume )
- Automatic volume data analysis possible
Cons:
- Object must be penetrable by all sides
- Technically complex and therefore expensive
- Reduced data quality on the basis of scattered radiation
Applications for
- Visualization and dimensioning of internal structures
- 3D distribution of material properties (such as density, porosity )
- Error checking
Helical CT
This process is very similar to the method now mainly used in medicine, but here again, with the difference that the X-ray source and detector stand still and moves the test object. However, not only in a plane, but with the simultaneous movement in the longitudinal direction, which taken as a whole from the object means a helical movement.
Advantages:
- Reduction of artifacts ( Feldkamp algorithm )
Cons:
- Mechanically -consuming ( because of the additional axis of movement )
Areas of application:
- Measurement
- Investigation of long objects
Laminography / tomosynthesis
Here happens the layered investigation and reconstruction mainly flat objects which are not accessible from all sides if necessary. The process can in turn be divided:
- Translational laminography: Here the object between the X-ray source and detector is pushed. Due to the lateral offset to the inside can be reconstructed in three dimensions.
- Rotary laminography: Here rotate X-ray source and / or detector above and below the object. The information obtained from the different angles of incidence, the object can be reconstructed in three dimensions.
The laminography has the following advantages:
- Production of depth information without all-round access
- Possibility of a cut - CT
Cons:
- The depth information obtained are of limited precision
Laminographic procedures are often used for:
- The audit of board materials
- Testing of electronic printed circuit boards
- The study of large -scale components without all-round access.
Classification by size
A sub - micro - CT system. Right tube, left the detector. Very close to the tube and very small, the test object on a needle on a turntable.
Building a micro - CT system; in the foreground the X-ray tube, in the center of the object on a turntable, behind the flat-panel detector
It is also possible to divide recording systems according to the size of objects or the recognition of detail:
Macro - CT
This is about the investigation of large objects ( meter range ). These so-called X-ray sources are used with macro focus, achieve the detail Erkennbarkeiten in the millimeter range. Such systems are often used for investigation of castings ( engine blocks, cylinder heads, etc. ) are used, but also for ceramics.
Micro-CT
These systems work with microfocus tubes that allow a detail detectability in the micrometer range. The available tubes, as well as requirements for meaningful recording times, confine the object size to about 20 cm. Applications include plastic parts, metal parts made of lightweight materials ( eg aluminum) and also ceramic pieces of suitable size.
Sub - micro CT and nano - CT
Such systems achieve the highest resolutions of conventional CT scanners. Here is working with special X-ray sources that have very small focal spots. Also, detectors are used with high resolution, as well as working under high geometric magnification. This detail Erkennbarkeiten are accessible down to about 500 nm. These orders of magnitude but the object size is limited to a few millimeters. Such systems are therefore often used in materials characterization, for highly accurate investigation of electronic components, or for biological samples ( eg insects, plant seeds, etc.).
In addition, there also exist Classifications to stationary or mobile, on the application ( error detection and measurement techniques) or by X-ray energy used (multi - energy method).
Exemplary applications of ICT
Apart from the advanced engineering opportunities may be realized with the Industrial Computed time-and cost-related advantages for a wide range of products. The technology lends itself to the analysis of workpieces with complex internal geometry as well as components made from different materials. The applications include:
- Supplying all of the automotive industry,
- The plastics and electronics industry
- Parts produced by casting
- Measurement of assembled or composite assemblies
Examples
Pine cones. Shown with "CT Alpha " by Procon X -Ray. Seeds in red.
Flight through a CT image stack in the Z (vertical ) direction. The ear plugs pictured is in a simulated ear canal from styrofoam and adapts its shape.
Disposable salt mill with plastic grinder in a helical CT
Flight through a 3D reconstruction of a helical CT in a one- Pepper Mill