High speed press noise - modifying safety guarding

The problem

A health care company manufacturing medical containers used a process of multi-stage forming on high-speed, automatic, coil-feed transfer presses. The presses consisted of a number of cam-driven, mechanical hammers mounted on heavy steel base frames, factory fitted with enclosures acting both as a safety guard and to reduce some noise emission.

It was impossible to change the noise generating mechanism of the press, nor would increasing the acoustic absorption have resulted in sufficient noise reduction. In addition, the shop ran on 24-hour shifts, preventing any prolonged acoustic examination of a given press running in isolation.

The solution

A sound intensity survey of each press was carried out, enabling the acoustic energy output of any selected part of the machine to be measured in isolation.

The survey identified those presses that were the major contributors to overall shop noise and how that output was distributed over the various panels of the machine. The noise sources and resulting treatment were as follows:

• the press base-frame was clad with preformed acoustic panels;
• acoustic covers were placed over the slots provided for raising the access doors on the roof;
• lightweight polymer glazing on the access doors was replaced by double-skin polycarbonate;
• the enclosure was isolated from its base by pads of anti-vibration material;
• hinged acoustic enclosures were fitted over the coil feed slot.

The cost

About £2000 per press. (1995)

The result

A noise reduction of up to 11 dB per press.

Source

Photographs courtesy of 3M Neotechnic Limited. Noise control survey conducted by Ian Sharland Limited.