Changeover sequencing is simply creating a production sequence that reduces the changeover effort. For example, in injection molding, colors are often changed from light to dark to reduce the cleaning effort. However, like all production sequencing (like leveling, lot sizing, prioritization,….), it adds to the replenishment time. Especially if you are using pull production, a consistent replenishment time reduces fluctuations, whereas an inconsistent replenishment time increases fluctuations and hence waste. But how can we get a more consistent replenishment time?
SMED
How to Prioritize in Changeover Sequencing
Changeovers take away time from production, and often require larger lot sizes as well. The best response would be of course to reduce changeover times, but this is a lot of work and may not always be possible. Another frequent option is to sequence the changeovers to reduce the overall changeover time. This post looks at a way to sequence production while also being able to prioritize production.
Changeover Sequencing – Part 1
The sequence of your changeover can have quite an impact on the duration of the changeover. In this series of posts I will show some approaches on how to improve your changeover durations by carefully sequencing the products. This was initially intended to be one post, but as so often happens, it turned out to be more complex than initially thought, and hence I have split it into two posts. The next post will appear next week.
On Running Changeovers
Changeover times and their reduction are popular topics in lean manufacturing. In this post I would like to introduce the idea of running changeovers for production lines. The idea behind it is simple, and probably many of you do it already. Nevertheless, I have found little info on it online. I also would like to go into more detail on the benefits of a running changeover in comparison to the alternatives.
The Phases of a Changeover
A changeover is changing the set-up of a process from one product to the next. Reducing changeover times is a common and popular way to decrease inventory or to increase available work time (see SMED). Ideally, the changeover time should be zero, allowing true one-piece flow. In reality, however, it is often not zero. This post looks in more detail at the different phases of a changeover to help you understand the process better and to reduce your changeover times.
What to Do with SMED: Reduce Lot Size or Increase Work Time?
SMED (Single Minute Exchange of Die) is a very useful tool to reduce changeover time. Reducing changeover time will free up time for other uses. Western management often wants to use this time to produce more goods. However, the rule of thumb at Toyota is to use this newly available time to do more changeovers rather than more products. This increase in changeover has the potential to significantly reduce the lot size, which often has much larger benefits than the additional work time. In this blog post I want to look in more detail at this relation between changeover duration, productivity, and lot size.
SMED – Creative Quick Changeover Exercises and Training
One popular approach to battle waste is to streamline changeovers. Changing machines from one setup to another is often a time-consuming exercise. Hence, in lean manufacturing, reducing changeover times is a well-known method for improving efficiency. This post will show a number of examples where these quick changeovers (also known as SMED) can be practiced in an unusual environment.