## 2 Instruments and Technological Equipment
### Technological Equipment under Study  
Figure 2 shows an example of a multi-purpose CNC lathe CA700K10F2 (JSC \"SASTA\", Russian Federation), where the accelerometers are fixed to the base of the turret and the spindle headstock body using a threaded stud.  
Figure 2 depicts two accelerometers, the analysis of the signals of which showed that the signals recorded on the spindle headstock are significantly less informative about the cutting process compared to the accelerometer mounted on the base of the turret. However, the signals received from the surface of the spindle head contain more diagnostic information regarding the condition of the bearings of the front spindle support [26; 51]. Figure 3 shows the locations of the vibration sensors on a flat-grinding machine. Since, in this case, the tool was rotating, the sensors were located on the side of the workpiece. The figure shows that in addition to the accelerometer, an acoustic emission sensor and a 3-component dynamometer by Kistler were used in the experiment. Two identical workpieces made of heat-resistant steel Inconel 718 were mounted on the machine using screws.  
Figure 4 shows another example of installing an accelerometer on a magnet on the support of a universal lathe for experiments with turning and boring operations on workpieces made of 41 Cr54 steel (DIN, EN standards). The accelerometer was located on the support sufficiently far from the processing area.  
When conducting studies of AE signals on machines processing with concentrated energy flows, the installation of an accelerometer encountered specific difficulties. The more significant difficulties arose when monitoring AE during electron beam doping in a vacuum chamber. Inserting the accelerometer into the chamber was impossible due to powerful  
Figure 2: Locations of accelerometers on a CNC lathe: 1—turret; 2—accelerometer on the turret base; 3—accelerometer on the spindle headstock body.  
electromagnetic interference and challenges in introducing cables to the sensor through vacuum inlets. To obtain information about the VA signal when applying an electron pulse, it was necessary to use a wire waveguide [50]. Figure 5 shows the vacuum chamber of the \"RITM-SP\" installation [52] with an open hatch, where the irradiated workpiece with an attached waveguide in the form of a copper wire with a cross-section of 2.1 mm\({}^{2}\) is visible. The exact figure shows a scheme for recording AE signals, where a receiving plate (position 3) is installed at the end of the waveguide on which the accelerometer is mounted.  
When studying AE signals on WEDM machines, the problem was that the workpiece was immersed in the working fluid during processing. The laboratory equipment was not intended to work in a liquid environment; therefore, the accelerometers were installed on additional stands on the machine worktable. When immersed in the working fluid, the upper part of the stand, along with the accelerometer, remained in the air. Figure 6 shows the installation of the accelerometer in the processing area of the CUT30P WEDM machine (GF Agie Charmilles, Basel, Switzerland).  
Figure 4: Installation of an accelerometer on a universal lathe for experiments with turning and boring operations: 1—boring cutter; 2—straight-turning cutter; 3—workpiece; 4—accelerometer mounted on a magnet.  
Figure 3: Experimental stand based on a flat-grinding machine with vibration sensors: 1—grinding wheel with electroorundum grains with a solid bundle; 2—two workpieces; 3—KD-35 accelerometer; 4—acoustic emission sensor; 5—Kistler dynamometer table.