Reducing Noise Levels Caused by Multi-tool Automatic Lathes as a Measure to Reduce Occupational Risk

The work of machine operators is affected by occupational factors, one of which is noise caused by process equipment. Among technological operations performed by automatic lathes of longitudinal turning in terms of sound radiation intensity, external longitudinal turning, thread cutting, and chisel threading can be specifically mentioned. The study analyzes the noise caused by multi-tool automatic lathes and proposes measures to reduce the noise levels. To select engineering solutions for noise protection equipment, the theoretical calculation of octave levels of sound pressure is performed at the design stage. The possibility of replacing the main motion gear drive with a variable drive has determined the structure of the spindle assembly. The structure of supports has been determined based on the requirements for spindle blocks: by outrun at the front face plane of the spindle in radial and axial directions and by the rigidity of the spindle block (determined by the elastic motions of the spindle’s front face plane). The analysis of noise spectra caused by the machine with modernized spindle assembly has shown that the sound pressure levels within the frequency interval of 250–8000 Hz have been reduced by 10 dB. Unlike a prefabricated part, it is almost impossible to reduce the intensity of sound radiation of support; however, the structure of supports can use vibration and sound protection systems with magnetically charged rubber. The advantages of the latter are the magnetic drag to the metal base and high rubber density. The plate is installed directly on the upper planes of supports fully covering them. The only noise source whose sound radiation intensity has remained at the same level is the prefabricated part, as the cutting process provides no possibility of reducing its level in the source. However, the calculations of sound pressure levels, considering the time protection, have demonstrated their complete compliance with the maximum permissible values within the entire frequency interval.