A manufacturer of artificial limbs was concerned with noise levels produced by a small bumping machine used for hand-forming sheet metal components of complex shapes. Unformed sheets were held over a steel ball and then pressed into a curve by an elastic pad on the end of an arm. The arm was repeatedly and rapidly raised and lowered by a mechanical drive, resulting in A-weighted noise levels in the range 91 to 93 dB.
The noise generating mechanisms were identified as the rigidly-mounted drive assembly, badly worn bearings, excessive clearances and the drive-belt guard.
The following modifications were made to the machine:
A noise reduction of between 16 and 21 dB, depending on whether the machine was idling or in full operation. An additional benefit was to extend the life of the bearings from six months to three years. (1995)
Report supplied by ISVR Consultancy Services.