Coordinate measuring machines with X-ray tomography

Figure 48a images a basic machine design derived from the machines with horizontal ram described above. The linear axes can be mechanical or air bearing, depending on the accuracy requirements. They are used to adjust the magnification of the X-ray sensors, for scanning tomographically and, in the case of multi-sensor machines, also for measurement with tactile and optical sensors. For the latter task, the various sensors already described can be used with the associated changing devices. To ensure collision-free operation, the X-ray sensors and the other sensors are each arranged on separate rams.

Figure 48b images an alternative design for larger measuring objects. Here, the vertical relative movement between sensors and rotary table or measuring object, e.g. for scanning, is realised by moving the X-ray tube and detector. Scanning perpendicular to the rotary axis is realised by moving the rotary table with the object, while the magnification is set by moving the rotary table along the beam direction. X-ray tubes are changed by separate vertical adjustment and different beam properties are selected automatically. The cone angle is set by moving the X-ray tubes horizontally. The tactile and/or optical sensors are used by interacting the vertical sensor axis with the axes of the table. With the Werth TomoScope® (Fig. 36), this principle was realised for the first time worldwide as a CT coordinate measuring machine. The mechanical components and thus also the machine accuracy correspond to those of the ScopeCheck® machines (see coordinate measuring machines with rotary axes, p. 67 ff.).

By selecting the appropriate X-ray components (voltage range, type of X-ray tube and sensor), the machine can be optimally configured for different workpiece materials. For example, low tube voltages are useful for measuring plastic parts that are easy to X-ray, while high tube voltages are useful for measuring metal parts that are more difficult to X-ray. Figure 49 shows a machine for large components up to 1000 mm in length and 500 mm in diameter. Higher accuracies can also be achieved in tomography scans with air bearing machines (e.g. Werth TomoCheck®).