what a bunch of cynics we are... although I agree that slogans don't do much.
"Quality is Job One" will motivate no one unless it's a reminder that there will actually be rewards for good quality work in the form of promotion, pay increases, etc. Otherwise they become demotivators and are sneered at with "I work my butt off, produce no defectives, but still haven't gotten a raise in 2 years"
I'd suggest if you feel the need to post anything either:
a)post your quality policy and then spend time regularly explaining to operators and supervisors how their job supports the quality policy and enables their own personal growth.
b) post actual metrics on the how the department and company is doing and have weekly meetings to review how these metrics impact the employees.