The 4M change simply means that people, machines, methods and materials have changed, that is, the four elements of people, machines, methods and materials have changed.

In industrial production, any one of the four elements of human, machine, law and material often changes, which will have a great impact on the whole production process and even lead to the decline of product quality. Therefore, as the person in charge of the factory, especially foreign companies, they attach great importance to the change of 4M, so they often let people maintain and inspect the machines and materials to ensure the normal production.