Silent machines
No one on earth can escape the sounds of noise- an unwanted, disturbing sound that causes annoyance, sleeplessness, fright, or any other stress reaction. In the past 30 years, noise in all areas, especially in urban areas, has been increasing rapidly. The acknowledgement that noise pollution has already become an environmental problem has resulted in a number of European directives aiming to regulate noise levels. The NOISELESS project aimed to sharply reduce noise emission from machine tools through the development of innovative machines producing techniques combined with novel damping and absorbent devices. The project has already produced tangible results since a prototype noiseless punching machine has been developed. The ineffective approach of reducing noise levels by completely enclosing the machine has been abandoned. In contrast, design modifications and extra equipment integrated in the punching machine resulted in the desired noise reduction. Linear motors for both the X and the Y axis were used. Therefore the machine dispensed with rotary motor, belt, bearings and ballscrew. Linear motors substantially reduced the noise produced in transmission at fast speeds. The axis, driven by the linear motor, was guided by re-circulating caged balls resulting in further noise reduction. Structural noise on the other hand was minimised through the use of active dampers. The installed active mass damper has its first mode of vibration at 900Hz, an obstacle in facilitating further noise reduction via the damper strategy. The prototype punching machine can work at different constant speeds of the punching unit and is equipped with new tool holders. Recent scientific health evidence suggests that workers may be succumbing to disease through the insidious effects of chronic noise exposure. Therefore, the development of such noiseless machines, apart from the expected economic benefits, will also reduce incidence of workers' physical and psychological injury.
