Changeover in a manufacturing setting is an unavoidable type of downtime. At the same time, it can and should be optimized according to lean production standards.
A changeover process is when machines, people, or products are changed between – or even during – manufacturing processes. Downtime is a lean manufacturing “waste” since time is spent waiting for production lines or machines to boot back up to full efficiency.
The problem with simply “optimizing” changeover is that there are so many types of changeover: tools and materials changes, machinery settings changes, product changes, shift changes, sanitizing equipment, etc.
If you try to treat changeover as a singular issue by just counting downtime alone, you’re missing all the other workflow issues you could be optimizing independently.
Let’s get into the details of how to really analyze your operation’s approach to changeover optimization by explaining 3 different ways to properly reduce unnecessary changeover downtime.
Planning Your Audit: Identifying the “3 Ups” of Changeover
Most people casually refer to changeover as the necessary set-up for systems to run properly. However, “set-up” is just one of the three types of changeover common in almost every manufacturing plant.
It’s an important first step to truly delineate the types of changeover processes that occur on your shop floor. Then, you can inspect each type with full attention.
After all, each type of changeover includes separate actions performed by workers, and it’s best to be specific in your SOPs and work instructions or workers will have to improvise, leading to human error.
Set-Up Changeover
Set-up changeover includes switching out equipment for other types of equipment. Sometimes that includes workers physically moving specialized machinery to and from different workstations as needed.
This also includes swapping out mechanical parts that are required for producing separate product lines that cannot be adjusted after start-up.
The best way to optimize this type of changeover is to map out planned procedures and coordinate the work that must be done between production line jobs. An example of this is prepping tools and gathering materials. One great tool for optimizing this type of changeover is value stream mapping.
Start-Up Changeover
Start-up changeover includes fine-tuning machinery after it has been turned on. Types of start-up adjustments are jams, blockages, and quality check changes.
Most of the issues that cause start-up changeover are due to variability within production. There are many lean tools to help eliminate variability, but a reliable one to start with is OEE, or overall equipment effectiveness. OEE tracking makes sure that process errors caused by faulty equipment are fixed immediately.
Clean-Up Changeover
Clean-up changeover includes changing materials, components, and products from the line. It can be as simple as swapping out a domestic product label for an international label in a different language.
On the other hand, clean-up can be extensive, including disassembly and sterilization of equipment after handling active pharmaceutical ingredients.
Depending on your type of production, there are health and safety standards that must be strictly adhered to for the product quality and reliability. Revisit cGMP, or current good manufacturing processes, as well as ISO requirements for your industry.
Applying the SMED Technique
SMED stands for Single Method Exchange of Die. It was created by Toyota Production System’s Shigeo Shingo, the godfather of lean manufacturing. SMED is a slightly more involved process with 7 separate steps, but you will often hear it mentioned in combination with changeover because it is specifically designed to address those related needs.
Here are the 7 basic steps of SMED, simplified for comprehension:
1. Observe the Current Methodology
This should be familiar to anyone who has read about TPS’s lean methodologies: simply put, genchi genbutsu, or “Go and see!”
Active inspection of your factory’s current practices is the best way to get a high-level overview of your strengths and weaknesses, hands down. See how changeover processes actually play out across a whole work day, and you will gain an understanding of practical limitations.
2. Separate Internal & External Activities
“Internal” activities are only performed when production is paused. “External” activities can be performed simultaneously with the last batch of a job or during start-up of the first batch of the next job.
A good example of an external activity is fetching required manual tools, like wrenches or welding torches, before the previous assembly step is finished.
3. Convert Internal activities into External ones
You may not be able to convert all activities, and don’t try to complicate it if that is the case. Instead, only convert where it is possible and it makes sense.
For example, a good conversion is pre-heating tools so that they are ready exactly when they need to be used.
4. Simplify Remaining Internal Activities
The optimization is in the details – Shigeo Shingo once said that only the last turn of a bolt is the one that tightens assembly. The previous turning of the bolt is just movement necessary to reach that final torque. In other words, simplify movement required on the line by making assembly as integrated a process as possible.
If a worker just needs to check torque values to ensure quality, don’t require the worker to manually install each bolt one after the other from start to finish. Just require the worker to test the torque values of the bolts after automatic assembly.
5. Streamline External Activities
This step is similar to the previous step – streamline your external activities with the same diligence as you did your internal activities. This is so that they are of the same scale to internal activities both in effort, movement, and function.
6. Record Your New Documentation
Since this step-by-step process is rooted in the details, you need to be documenting the process improvements you are making so that you don’t miss anything critical the first time through.
This is also important for establishing standardized improvements within your workforce, which is discussed more in-depth in the final section of this article.
7. Rinse & Repeat
Shigeo Shingo reported that for each iteration of the SMED method, you should expect a 45% improvement in set-up times. Ideally, changeover should be under 10 minutes.
This may take several iterations as you experiment with the practicality of your workflow changes, so don’t stress if you don’t reach that mark immediately.
Implementing Standardized Changeover Practices
Often when reducing changeover, manufacturers implement the previous methods – SMED and addressing the 3 Ups – and stop there. This is a mistake.
Unfortunately this means that their revolutionary improvements in production are short-term. Over time, the updated standards erode due to lack of documentation, confusion over best practices, and reliance upon habitual shortcuts that come more naturally to workers.
To fix this, your documentation must go beyond recording data and stretch down to the shop floor where it can be useful for just-in-time learning.
Value Stream Mapping
Optimizing manufacturing processes involves a coordination of workflows that resembles a finely-tuned symphony of mechanical instruments. It’s easy to concentrate too much on one instrument when you should be listening to the entire orchestral chord.
In other words, don’t let one production line outshine or hold-up your other production lines because you’re trying to optimize one spot at a time instead of the whole ecosystem.
“A manufacturing facility can improve its operations capabilities efficiently by identifying critical operations that affect the overall production, quality, and delivery of the facility. After identifying these operations, each of them can be examined individually in terms of developing a process map with the purpose of understanding the important characteristics of a manufacturing facility.”
Improving Production Changeovers and the Optimization. Procedia Manufacturing Vol. 11, 2017, pp 2042-2050.
This is where value-stream mapping comes in. It’s great to have detailed procedures for each individual production process. It’s even better to pair that fine-tuned work with a cohesive roadmap of coordinated workflows over the entire factory. This way you can see your whole shop floor at-a-glance so you can make adjustments just-in-time.
Work Instructions
Finally but perhaps most importantly, you must communicate your improvements to your workforce. You can do all the optimizing in the world on paper, but you need accurate and consistent follow-through in order to actually see the results you are forecasting.
The best way to do this is through visual and interactive work instructions for every sub-task that happens on the shop floor. Some manufacturers prefer to do this through their MES or ERP, but when you are designing detailed work instructions, instructions shouldn’t be an afterthought or simple addendum to your existing digital platform.
This is because any deviation or lack of clarity is a major pain point in assembly for your workers, and this is where errors (and potentially even more downtime!) can occur.
Here are a few things that are extremely important to explain with words and visuals for total comprehension and compliance:
- Using intermediate jigs when possible
- Fueling parallel operations for little downtime
- Eliminating the need for constant adjustments
- Using functional clamps or eliminating fasteners
- Fully understanding function of work processes
That was a lot of information, but if you truly want to revolutionize practical use of changeover in a factory setting, it’s worth the effort of fully auditing your operations. Luckily, each of these 3 methods has many lean tools to help you along your journey of continuous improvement.
