Products and processes are two important outputs of engineering. Industrial engineering (IE) is productivity improvement activity. When IE is applied to products and processes, it is termed product IE and process IE respectively.
Frank Gilbreth suggested the involvement of operators in process analysis and improvement in 1921 in an article on process charts. Hence, formal and structured involvement of operators in process improvement was started by the industrial engineering and scientific management professions in the decade of 1911 to 1920 itself. But the practice got more systematized by Alan Mogensen in 1929 with the publication of his book The Commen Sense Approach to Improvement.
Toyota started its cost reduction improvements after second world war and made the front line kaizen a best practice and fruitful. People know more about the front line kaizen of Toyota and less about the contribution of engineers and especially industrial engineers in Toyota's success.
We have to make use of available resources. Instead of lamenting on the unavailability of the IE activities of engineers in Toyota, we have to learn about the best practice of Toyota front line kaizen and try to implement in our organizations. We have to learn about industrial engineer's best practices from some other organization.
Some references about Toyota's suggestion scheme successes are given below.
Chapter 6 Toyota Kaizen Methods - Art Smalley