I want to explain in more detail the productivity gains that are possible through Mixed Model Manufacturing, since they can be huge. Too big to be believed, in fact, unless we explain clearly how this can happen. So let’s break it down and look at how a 30% productivity gain could be possible.
PRODUCTIVITY STRATEGY #1: STANDARDIZATION AS A REQUIREMENT
The term we use for process documentation is “Standard Work Definitions”. Documenting the “One Best Way” to do work, at the product and process level, is a foundational requirement for Mixed Model Manufacturing, or for any Lean strategy for that matter. The goal here is to document the detailed work steps, work times, quality checks, material requirements, tooling and fixtures, and so on, for every product and every process. This is a big job if you don’t do this already!
How does this impact productivity? In the process of standardizing you can identify work steps as Value-Adding or Non-Value-Adding, and eliminate the Non-Value-Adding steps. You can do this right away, or conduct process improvement work if it’s needed. When you take out Non-Value-Adding work, productivity goes up.
PRODUCTIVITY STRATEGY #2: DESIGNING OPTIMUM WORK FLOW
If you record a work flow you’ll probably notice that a certain percentage of the time the workers are not able to work. Typically it’s for one of two reasons: they have nothing to work on, or they have finished their work but they can’t move the product out of their station. Balancing work flow better is how you reduce this waiting time, so that workers can add value more consistently, and be more productive. A part of the balancing effort also includes the skillful use of buffers, or In Process Kanbans, as a balancing tools.
PRODUCTIVITY STRATEGY #3: FORMAL CHECK-DO-CHECK PRACTICE
Obviously having to redo work will detract from productivity. One of the goals of your Standard Work Definition is to analyze and remove quality risks. This is called Poke-Yoke in Lean-speak. But what about workmanship errors that you cannot error-proof? Another technique, which won’t eliminate errors completely but will help to catch them sooner, is called Check-Do-Check. Check the work coming to you for quality issues, do your work, then check your own work. Just this simple practice can cause a boost in productivity by 1. Sensitizing operators to when errors can occur and 2. Catching errors quickly, rather than letting them proceed down the line.
What are the numbers?
PRODUCTIVITY STRATEGY #4: OPTIMUM SEQUENCING PLAN
For Mixed Model Manufacturing, optimal sequencing is a must. Since different models have different work content time, this variation will lead to increased starving and blocking of the work flow, which leads to lower productivity. The optimum sequencing strategy is developed during the line design process, based on product knowledge and often with computer simulation tools.
PRODUCTIVITY STRATEGY #5: OPTIMUM MATERIAL FLOW SYSTEM AND PRESENTATION
Productivity is going to drop like a rock, even with the best-designed line in the world, if the materials needed are not delivered on-time, with the right part to the right location. Operators will be waiting for needed material. Today companies are exploring the idea of strategic kitting to give a further boost to operator productivity by reducing the time and quality risk associated with part selection.
PRODUCTIVITY STRATEGY #6: FLEXING AS A WAY OF LIFE
I saved the best for last. The practice of flexing, or moving to the work, can be a huge productivity boost. Remember that even if you do everything right and apply strategies 1-5, a Mixed Model line still must deal with work content time and process variation. This will always exist, and it can’t be overcome completely. But if operators are willing and able to move to where the work needs to be done, they can continue to add value more consistently, and productivity will take a major jump up. This flexing is not “free form”, but instead is based on a set of clear rules for when to move (and where) and when to stay and work. Operators need to be trained in flexing. It won’t happen organically.
Paying close attention to productivity, and to a deep understanding of the factors that will hinder it, is an important part of the Mixed Model Line Design method. Variability is the challenge, and by applying these 6 strategies, you will do a lot to overcome it.
