Improvements to a bumping machine

The problem

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 solution

The following modifications were made to the machine:

• replacing the sheet metal drive-belt guard with wire mesh;
• using bobbin mounts to isolate the drive motor bed plate from the main casting;
• cutting holes in the bed plate to reduce its area and hence noise radiation;
• pre-loading the drive mechanism to reduce rattle;
• replacing plain bronze bearings with accurately loaded taper roller bearings;
• reforming the steel anvil ball socket for a tighter fit.

The cost

About £800.

The result

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)

Source

Report supplied by ISVR Consultancy Services.