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Specifications and Acceptance Tests – 3

The operating parameters must be precisely specified for the length measurement error as well. The parameters must also be specified and tested for the operating modes measurement “in the image” and measurement “at the image” (e.g. raster tomography). It is […]

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Specifications and Acceptance Tests – 2

The use of multidimensional standards, such as spatial arrays of spheres on pins, is particularly efficient.  This  type of standard can be used to check many or even  all  of  the  lengths  required  to  test the  coordinate  measuring machine against […]

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Specifications And Acceptance Tests – 1

Starting with the DIN EN ISO 10360 international series of standards, the Association of German Engineers (Verein  Deutscher  Ingenieure: VDI) has developed a guideline for acceptance testing of coordinate measuring machines  with  X-ray  tomography. This has  been  integrated  both  in […]

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Spiral Tomography

Using spiral (better helical) tomography, the cone beam artifacts that arise in conventional cone beam tomography can be prevented.  This works by moving the measured object along the rotary axis as it rotates.  In spiral tomography, each layer of the […]

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Dual-Spectra Tomography

In coordinate measuring technology with computed tomography, the dimensional analysis of work pieces made of  multiple materials is particularly challenging.  Multi-material work pieces are often metal and plastic components, such as assembled plug connectors.  The measurement task is typically to […]

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Eccentric, Region of Interest, and Multi-ROI Tomography

Eccentric Tomography (a) now makes it possible to place the work piece arbitrarily on the rotary table.  This eliminates the laborious and time consuming alignment of the work piece, making measurements more convenient and efficient.  The measuring software automatically calculates […]

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Noise

The basic physical effect of the working principle of X-ray sensors is the conversion of light energy into electrical charge. This conversion occurs due to the photoelectric effect. Because this is a statistical process, not every photon is converted into […]

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Resolution

When discussing resolution in the field of coordinate measuring technology, two categories must be fundamentally differentiated: structural (or spatial) resolution and positional (or metrological) resolution. The structural resolution defines how small structures on the measured object can be and still […]

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Cone Beam Geometry – 2

Cone beam artifacts can be completely avoided with the use of spiral  tomography. In this special process, a translational motion is performed in the direction of the rotary axis at the same time as the rotation of the object. The […]

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Cone Beam Geometry – 1

For cone beam tomography, the ideal beam geometry (fan beam) is purposefully altered to increase energy efficiency and reduce measurement time. This means that the ideal beam geometry is found only in the center plane. It is defined as the […]

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Scattered Radiation

When the X-rays are attenuated in the material, due to Compton scattering, incident X- ray photons are deflected (scattered) from their original direction of travel by electrons of the penetrated material and are therefore subject to a loss of energy […]

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Beam Hardening – 2

Beam hardening is not considered in the mathematical principle of X-ray tomography.  The measurement errors that result from this are known as beam hardening artifacts.  Their magnitude depends on the material and geometry of the measured object. Beam hardening can […]

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Beam Hardening – 1

The radiation generated in an X-ray tube is not monochromatic.  Similar to the visible light of an incandescent lamp, it is a continuous radiation spectrum with a particular bandwidth (bremsstrahlung or “braking radiation” from German “bremsen”: to brake and Strahlung”: […]

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Inspecting the Material Structure – 4

With special software, assemblies can also be inspected. Assembly errors can be easily detected or the assembly can be shown in various functional states. It is also possible to virtually disassemble the components and to investigate them (e.g. to analyze […]

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Inspecting the Material Structure – 3

Software tools exist for crack testing, for example.  Material irregularities of fibers can also be visualized.  To analyze the flow behavior of glass fibers, very high resolution is required.

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Inspecting the Material Structure – 2

Special software tools are used to automatically identify voids and cracks inside measured objects. These can be detected, classified by size, and counted according to their classification. Fully automatic analysis, with tolerance, can be performed. The voids that have been […]

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Inspecting the Material Structure – 1

To provide a way for users of coordinate measuring machines with X-ray tomography to perform material inspections, as known from earlier tomography inspection systems, suitable software tools are provided for material analysis. They are based on direct analysis of the […]

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Autocorrection – 3

The reproducibility of the measured diameters of such a spray hole, using sections at intervals of about 20µm and measured five times (a). The reproducibility results are better than 1µm. If these results are compared to calibration measurements (b), systematic […]

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Autocorrection – 2

When measuring injector components for diesel engines, for example, diameter tolerances of better than 5µm are required. To measure these tolerances reliably (measurement process capability), it is necessary to ensure measurement errors less than 0.5 µm. One prerequisite for achieving […]

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Autocorrection – 1

Objects made of materials that are relatively easy to penetrate with dimensions that are not too large and with average precision requirements can be measured using X-ray tomography with sufficient accuracy. For special tasks, such as measuring components with tight […]

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Multisensor Measurements – 3

Prior to measuring with several sensors on one coordinate measuring machine, the offset positions of the sensors must be determined. A standard is measured using all the sensors that will be used. The material of this standard must reflect optical […]

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Multisensor Measurements – 2

A similar approach can be used as an alternative to the Dual-Spectra Tomography for economically measuring plastic parts with embedded metal. In this case, only the internal metallic components are measured with the X-ray sensor, using high energy X-rays.  The […]

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Multisensor Measurements – 1

The combination of X-ray sensors and tactile or optical sensors in one coordinate measuring machine results in new potential applications.  For various measurement tasks, other sensors besides the X-ray sensor can be integrated in the measurement programs. The image processing sensor, […]

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Measurement and Comparison in Sections – 3

As an alternative approach 2D measurements can be taken directly in the X-ray image for certain work pieces. To do this, it is necessary to determine the local magnification in the X-ray beam path as precisely as possible. Geometric elements […]

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Measurement and Comparison in Sections – 2

For analyzing the 2D dimensional cross sections that are generated, the same software functions are used as for analyzing contours scanned by image processing or with a probe. Individual contour segments can be selected by drawing windows. Standard geometric elements, […]

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Measurement and Comparison in Sections – 1

In practice, it is common to define drawing dimensions in 2D views and sections. This situation must also be considered when analyzing tomographically generated measurement data. The data for analysis must be extracted from the 3D data set as a […]

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3D Nominal to Actual Comparison – 2

The comparison of the measured point cloud to CAD or master part data can also be used directly to correct injection molds. To do this, the nominal to actual deviation calculation is performed as a first step. The deviation data […]

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3D Nominal to Actual Comparison – 1

A direct comparison of the actual work piece geometry to the nominal geometry, such as CAD data or previously measured master parts, is particularly useful when measuring free form surfaces. However, even form deviations of standard geometric elements or paired […]

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Calculating Dimensions – 3

It is more effective to set up measurement sequences using 3D CAD data. By simply selecting the CAD patches that describe the areas of interest (e.g. a cylinder or plane), the corresponding measurement points are selected automatically. There are two […]

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Calculating Dimensions – 2

For classic coordinate measuring machines, all measurement points required for analyzing the required features must be precisely defined before, or no later than during, the measurement process. This is not necessary for tomography. Because the entire work piece is captured, […]

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Calculating Dimensions – 1

For various applications, the entire work piece geometry must be dimensionally analyzed. To document the quality of a mold for plastic injection molded parts, for example, a sample part must be measured completely (first article inspection). Particularly for medical component […]

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Set-up and X-ray Imaging – 4

The  number  of  rotary  steps  should  be  between 400 and 1600 per 360° revolution. By using a function for image averaging, several images can be overlaid for each rotary position. Thus, noise can be reduced at the cost of measurement […]

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Set-up and X-ray Imaging – 3

The radiation spectrum can also be optimized with the use of filters, made of aluminum, tin, or gold, at the output window of the X-ray tube.  The  use  of  such filters,  however, results in lower radiation intensities, which must be […]

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Set-up and X-ray Imaging – 2

By selecting the voltage and current of the X-ray tubes, the image brightness can be changed.  The voltage changes the frequency spectrum of the radiation at the same time, and must therefore be optimized for the material of the measurement object. […]

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Set-up and X-ray Imaging – 1

Prior to tomography of a work piece, the right imaging scale (magnification) must be selected for the measuring machine. The desired detail resolution must be considered. It must also be ensured that the desired area of the work piece, or […]

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Radiation Safeguards

  The hazardous health effects of X-rays must be considered when using this radiation for measurements.  Coordinate measuring machines with X-ray tomography that meet the requirements for fully protected machines under the X-ray regulations have lead shielding in the machine […]

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Linear Axes – 4

For measuring machines with a precision of a few micrometers, the linear axes can have mechanical bearings.  For higher precision requirements, in the sub-micro- meter range, air bearings are used due to the better repeatability. As is typical for coordinate […]

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Linear Axes – 3

Various sensors can then be selected from the palette of multisensor coordinate measuring machines and used with this interface.  Figure shows such a tilting joint with an image processing measurement head. This measurement head can optionally be equipped with a […]

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Linear Axes – 2

To hold the magnification constant when changing the distance between the source and sensor, the rotary axis must be shifted accordingly in the direction of the sensor. The increased cone angle can cause measurement errors in the lower and upper […]

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Linear Axes – 1

If a measuring machine is not designed specifically for a dedicated application, but is intended to have flexibility, linear axes are needed in addition to the rotary axis. They serve to adjust the magnification to position the work piece and […]

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X-Ray Sensor – 4

The image scale between the object plane and the sensor (usually, but not entirely accurately, referred to as the magnification) is in principle greater for large sensors with large pixels, because a greater distance is needed to form an image […]

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X-Ray Sensor – 3

The scintillator converts the X-rays that strike the sensor into light. The high-energy photons of the X-rays excite particles of the scintillator material as they pass through it. These particles then emit light in the visible frequency spectrum. This makes […]

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X-Ray Sensor – 2

The smaller the cone angle, the lower these measurement errors. This means that it makes sense to design high precision machines with a greater distance between the X-ray source and the sensor. However, this reduces the efficiency of the X-ray […]

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X-Ray Sensor – 1

X-ray sensors are available both as line sensors and area sensors. From a purely geometric standpoint, line sensors would be perfect. Synchronized movement of the X-ray source and the line sensor relative to the measured object in the direction of […]

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X-Ray Source – 3

The construction of an X-ray tube is very complex in detail. In addition to the electrodes and the target, it has a large number of components for focusing the beam, electrode heating, and other functions.  Due to the required   measurement […]

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X-Ray Source – 2

The targets of X-ray tubes are fundamentally classified as reflection targets and transmission targets. The difference when using reflection or transmission targets is in the available radiation power, and therefore the measurement time in conjunction with the available minimum focal […]

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X-ray Source – 1

The tubes used to generate X-rays are a core component of X-ray tomography machines. They operate on the basic principle of electron beam tubes. Free electrons are generated in a vacuum by thermionic emission, and accelerated by an electrical field […]

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Raster Tomography – 5

If the diameter of the enveloping circle of the measured object is larger than the sensor size in the work piece plane (e. g. disc shaped parts), the rastering must be done perpendicular to the rotary axis (seen in above image).  […]

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Raster Tomography – 4

This figure shows an example of rastering along the rotary axis. However, this can be used only for relatively slim objects, such as long connectors. In this example, without raster tomography a voxel size of 0.25 mm is achieved with […]

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Raster Tomography – 3

Another application for raster tomography is to increase spatial resolution, if the sensor does not have sufficient resolution to measure small details of larger work pieces “in the picture”.  In this case, the appropriate magnification level is selected to achieve […]

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