Kaizen is a method for continuous improvement used in Lean Production. In traditional thinking processes become less efficient, and produce lower quality, as the machinery and equipment ages. The idea of Kaizen is to not only maintain the equipment to keep it as good as new, but to continue to make minor modifications that tailor it better to the process, for example making it interface better with upstream and downstream handling, part supplies and so on.
The workforce should be involved in Kaizen improvements through suggestion schemes and team based activities.
See also Kaizen Blitz.