First of all, I would always ask what is wrong with the current system. There might be all sorts of interesting findings coming from this question. And I'd ask this question throughout the company up and down the hierarchy tree.
Once I have an overview over people's opinions, a more thorough analysis has to be undertaken. What I did in a project once was to write down every single minute of a day on an excel sheet and mark off the minutes during which a respective production line was busy and not. This gives a nice picture of the situation - it shows break times (which are not covered), change-over times where the machine is stopped, and generally times when the plant is shut down. This is a nice base for a capacity calculation. After this, I'd observe the line to verify break times and other non-productive times. Maybe a new shift system is not needed but only some management tools?
Now, one thing is very important, for capacity reasons a day has 24 hours and not just day time hours. And a week has 5 or 7 times 24 hours; ideally both for comparisons. This is important to know as 7 x 24 is the maximum capacity available (5x24 in case of weekend closure). From that, cleaning and maintenance times need to be subtracted in order to get from a theoretical to a practical capacity. Once we know the amount of time of availability we are well prepared for a later scenario calculation.
The next thing I would look at are financial indicators. How much overtime did the company accrue and pay in the last year? What is the pay rate of the workers? How much does the company pay for temps and what is their rate compared to the ones of the employees? How high is the productivity of a temp as opposed to an employee?
And then, the IT evaluation: Are our systems ready for a switch? This is a discussion to be done with the IT department. Never assume IT is not an issue, it always is! And IT issues take time and money to solve.
Once, the analysis of the current situation is done I'd sit down and work on possible scenarios. This has to be done line by line and we need to answer the following question: How many people do we need in order to get a certain amount of output? This is particularly important when the company is faced with seasonalities. Any new shift system needs to be able to adjust to any seasonality without making financial losses.
Here, one needs to bear in mind how much staff a line needs in order to achieve maximum output. There must be some scenarios of what happens outputwise if less people are manned at a line. Those scenarios must cover high and low seasons, and a middle season, too. This is quite a nightmare and takes so much time! Be prepared!
What comes along with those scenarios is the question whether all staff is trained to accomplish such a shift change. How flexible are the employees and can they work at different lines? How much flexibility and cross-training does a new shift system require?
And finally, HR need to add their comments informing Operations about the legal situation of whether and how contracts can be changed, whether there are any strikes to be anticipated, etc. HR need to know who is loosing out and who is gaining from a new shift system.
The Finance Department needs to sort out the budget for the new year bearing in mind the scenarios in combination with any expected output. This has to be done with Operations.
After all the preparation the workers need to be informed and the bomb is going to burst..... But it is a good bomb and a good and modern shift system is worth going through the initial pain of preparation.
