It’s been written extensively in this space that by reducing the lean process wastes through applying the lean tools you can streamline your operations and make better use of your scarceresources.
However, the ideal lean scenario is to meet your customers’ expectations by providing just what they need right when they need it and as efficiently (and cost-effectively) as possible. This means having a smooth-flowing operation that is flexible enough to handle changes in demand with little pain and frustration.
To that end, lean focuses on reducing more than just the process wastes. There are two other facets of operational flow lean can optimize:
The best way for me to explain this is through an example. Going back to an earlier topic, let’s say you have 50 toys to build. The process of making the toys includes collecting the parts from previous steps, assembling them together, attaching them together with screws, and placing the completed toy into packaging.
It’s natural for people to want to complete certain steps of the process all at once for all 50 toys – getting all of the necessary parts, assembling all 5o toys together, moving on to screwing all the parts together, and then putting the completed toys into packaging. It provides the benefit of not needing to shift operations every time you move to a new step with a single unit – you need not remove the screwdriver from your hand or you might reduce a lot of walking time by standing in one place .
While true, start-and-go (also known as mura) causes a few other unseen issues. First, this is what is called batching. As Toyota Way Principle #2 tells us, the ideal lean production state is through continuous flow or one-piece flow – making one unit at a time reduces waiting time and optimizes operational flow. It is difficult to achieve, but once it is in place it features very limited waste activities.
Think about making cookies – baking is a batching operation because you’re completing steps for all soon-to-be-cookies at one time. In essence, the end user doesn’t get a cookie until all cookies are done baking, but a smooth continuous flow operation (where cookie ingredients are split by what one cookie requires and mixed together to make one cookie) means one cookie is received when one cookie is requested.
Batching is a delicate balance that must be examined. With cookies, it’s pretty difficult to do one-piece-flow and have the ingredients for a single cookie ready to go. However, what if one wanted to make 1,000 cookies? Would it make sense to mix the ingredients for 1,000 cookies together at one time and put 1,000 cookie batter spoonfuls into a giant oven at one time? No! You’d probably make 25 cookies at a time and repeat that procedure 40 times (or some other quantity and repetition).
In addition to batching, constant starting-and-going prevents flexibility and reduces the opportunity for smooth operational flow. It’s difficult to find a rhythm when operations expect upstream process to start and go at their production whim. With level loading and smooth predictable downstream operations, upstream operations can become more predictable and thusly smoother. Smoothness and predictability reduces frustration and operational headaches.
So what are some strategies to reduce stop-and-go-and-stop-again? Well, in the toy example, instead of having one person complete all four process steps in a certain amount of time, what if continuous flow was created with four operators, each one handling one of the process steps? Yes, it uses more operators but the work is completed in a quarter of the time (if process steps each take the same amount of time) and once the work is done the operators can move on to something else.
We’ve all had a boss or a coach tell us to “Work harder!” or “Work faster!” even though we are giving the best effort we possibly could. When you’re working at 100% and it’s still not good enough, there’s a problem.
Lean provides the opportunity to not only establish operations more in line with customer expectations but also provides an examination of how processes are completed in the environment available. Multiple lean process wastes (excess motion, excess transportation, overprocessing) tie directly to the overburden of operators (also known as muri) that can facilitate physical exhaustion.
Think about the conditions that suggest overburden of operators – repetitive motion, excess walking around, high temperatures, safety concerns, ergonomics issues – and consider where they would have an impact on production. Remember, production should be smooth and not full of stop-and-go but process tasks should be easy to complete and not wholly burdensome.
And beyond that, tasks that are dangerous and difficult could become much more costly when someone ends up missing work or, worse yet, in the hospital.
Process owners and managers need to have a keen sense to identify lean process wastes, but also the evidence of overburden and constant start-and-go through batching or not following standardized processes.