In order to guarantee the best quality of the results achieved in analyses, tests and inspections, optimum conditions are required. This is why Microvista relies on a combination computed tomograph from Varian, which is one of the most powerful industrial computed tomographs. In the year 2011, we also installed an inline CT pilot system. For evaluation of the 3D volume data acquired by CT, Microvista amongst others uses the software VG Studio Max from Volume Graphics.


Picture 1: Inline-CT pilot system

Picture 1 shows the inline CT pilot system of Microvista GmbH. Picture 2 and 3 3 show a view of the interior of the lead-cladded radiation protection cabin of the lab CT and of the „heart“ of the system at Microvista GmbH. In Picture 2 both X-ray tubes can be seen, which are used depending on the task at hand. The 450 keV minifocus tube is on the right side of the picture, the 225 keV microfocus tube is on the left side.

         
Picture 2: Minifocus and microfocus tube            Picture 3: Rotary table with linear axes, 
                                                                                             F
flat panel and linear array detector

In the midst of Picture 3, one can see a test specimen on the rotary table. The component mounting device is movable in all three axes for optimal component positioning between X-ray source and detector. Behind you can see both detectors, with the line array detector to the left and the flat panel detector to the right.

Technical Data:

 Manufacturer::  Varian
 Type:  BIR 800-450/225 CT/DR
 Minifocus tube:  450 keV
 Microfocus tube:  225 keV
 Flat panel detector:  2048 × 2048 Pixel @ 200 µm Pitch, 16 Bit
 ADC
 Linear array detector:  1024 channels  @ 385 µm Pitch, 18 Bit ADC

Machine combination:

The fact that two different tubes and detectors are available for measuring and testing allows to choose from various device combinations. Depending on the task, component sizes, material and overall radiography depth, the more powerful minifocus tube can either be used with the line array or flat panel detector. The microfocus tube is only used with the flat panel detector. For the minifocus tube, there is also the option of choosing between two different focal spot sizes. In this context, the following general interdependency applies: The smaller the focal spot, the more focused the images.

Technology in action:

The following ca. video of about three minutes length shows the installed equipment (lab CT) in use and conveys a good impression of Microvista GmbH’s possibilities.

Microvista GmbH’s equipment allows responding in a very flexible manner to the client’s requirements for component testing. No matter how innovative industrial computed tomography may be, there are natural and design-specific limits to its performance. The following section states the limits of the used equipment with regard to component dimensions and weight. It also states the radiography depth for various material types, up to which the required resolution of detail can be ensured.

  Laboratory CT Inline-CT
CT parameters    
Machine type BIR 800-450/225 CT/DR   Siemens Definition AS+
Energy max. 225 keV/ 450 keV max. 140 keV
Performance (peak) 1,5 kW 100 kW
Resolution > 80 µm > 240 µm

Maximum component dimensions and maximum weight:

With Microvista’s industrial computed tomography systems, it is possible to scan components of different sizes, geometries and weight. However, there are dimensional limits. Independent of component material, the following values are maximum values.

  Laboratory CT Inline-CT
Geometry and mass    
Envelope circle < 525 mm < 750 mm
Length < 1600 mm < 2000 mm
Mass < 100 kg < 100 kg

Maximum radiography depth:

Practice shows that limitations in most cases are not posed by component dimensions. More frequently, it is the cumulated wall thicknesses to be radiographed that prevent CT scanning.
The explanation: Due to the CT’s rotating movement, certain component areas are not solely radiographed at a right angle. Thus, “CT wall thicknesses” can increase to a multiple of cumulated nominal wall thickness. Therefore, the below stated maximum radiography depths are only for reference. Generally, precise statements can only be made after the component has been assessed and maybe has been subjected to a trial scan.
 
  Laboratory CT Inline CT
Suitable for radiography    
Plastic 500 mm 750 mm
Aluminium 380 mm 350 mm
Titanium 190 mm 100 mm
Iron 100 mm

On principle, CT can be used to examine all organic and inorganic materials. Artificial or composite material, ceramics and light metal such as aluminium or magnesium are excellently suited for tomography. Components made from iron or steel or from non-ferrous and heavy metal (e.g. copper, zinc) and their alloys (e.g. bronze, brass) require a more intense X-ray energy, which in turn affects resolution of detail.