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Knowledge Base/SMED Implementation Case Study: A Stamping Plant Reduces Changeover Time from 90 Minutes to 15 Minutes
Lean Production6 min read

SMED Implementation Case Study: A Stamping Plant Reduces Changeover Time from 90 Minutes to 15 Minutes

This practical article shares an experience where the author, upon arriving at a stamping plant, observed a die changeover taking 90 minutes, causing significant production line downtime and frustration. Recognizing this as a classic SMED case, the article explains in an accessible manner the reasons behind long changeover times and introduces SMED's core concepts, clearly differentiating "internal operations" and "external operations." Readers will gain a fresh perspective on how to significantly shorten changeover durations.

That Day, the Die Change Took Forever, and the Production Line Manager's Face Turned Green

I still remember one time when I was seconded from a wafer fab to the group's stamping plant to help implement Lean Production. At that time, they were preparing to produce a new part number and needed to change a die. I stood by watching, thinking to myself, "This is pretty much like changing a cassette on our machines." Guess what happened? From the removal of the old die to the locking in of the new die, adjusting parameters, and then getting the first-piece inspection OK, it took a full 90 minutes! 90 minutes! You could drive from Hsinchu to Taipei in that time. The production line manager's face turned green because, during those 90 minutes, the production line was completely idle. Talk about a loss! At that moment, I thought, isn't this a classic SMED case?

What Was the Problem? Why Did the Die Change Take So Long?

Simply put, the core concept of SMED (Single-Minute Exchange of Die) is to shorten "changeover time" to a single-digit minute. It sounds mysterious, but the principle is actually very simple: convert "internal operations" as much as possible into "external operations." What are internal operations? They are "things that can only be done when the machine is stopped." And external operations? They are "things that can be prepared in advance while the machine is running." If you think about it from another perspective, it's like getting ready for work in the morning. If everything has to be prepared only at the moment you leave, wouldn't you be late? But if you prepare your clothes and bag the night before, you save a lot of time in the morning, right? In the stamping plant's 90-minute changeover, most of the time was spent doing things that could have been prepared in advance, all while the machine was stopped.

How Was It Actually Done? Reducing 90 Minutes to 15 Minutes!

Alright, let's look at how we actually cut the 90 minutes down to 15 minutes. The first and most crucial step is "video recording." You heard that right, just use your phone to record. Record the entire changeover process from beginning to end. Then, we break down the video into every small action and analyze them one by one.

  1. Distinguish Internal and External Operations: We found that much of the time spent unscrewing, moving dies, and finding tools only began after the machine had stopped. These are typical internal operations. However, toolboxes can be prepared in advance, dies can be moved to the side of the machine beforehand, and screws can be sorted in advance – all of these can be external operations.
  2. Externalize Internal Operations: Previously, finding the new die in the warehouse only started after the old die was removed. Now, the new die is already positioned next to the machine, waiting, while the old die is still in production. Before, changing dies required wrenches of various sizes, and they had to be searched for every time. Now, we've created a dedicated toolbox containing only the tools needed for the current die change, with their positions clearly labeled. Just these two points alone saved nearly 30 minutes!
  3. Shorten Internal Operations Time: Some actions truly can only be done when the machine is stopped, so we tried to shorten them. For example, we replaced the fastening method that originally required screwing multiple bolts with quick clamps, which operate with a single press, like a seatbelt. Also, the manual adjustment of die alignment pins was changed to quick positioning. Before, it required careful alignment; now, it's in place instantly. This saved another 20 minutes.

After several rounds of improvement, the stamping plant's die changeover time directly dropped from 90 minutes to 15 minutes, and the DPMO value also decreased from the original 6210 to 3192! The production line manager was all smiles then.

The Most Common Pitfalls: Human Inertia and the "Good Enough" Mindset

Frankly, the most common pitfalls encountered when promoting SMED are not technical issues, but "people." Many experienced technicians would say, "I've been doing it this way for decades, what's the problem?" or "This is 'good enough,' no need to be so picky." At this point, you need data, you need video recording. Video is the best evidence; quantifying the time for each action helps them understand that these "good enough" moments accumulate into enormous waste. Another pitfall is the "achieve perfection in one go" mindset. Many people want to do it perfectly on the first try. To be honest, SMED is a continuous improvement process; you can't go from 90 minutes to 5 minutes on the first attempt. Start from 90 to 60, then from 60 to 30, step by step, making small improvements each time, and the cumulative effect will be significant.

One Thing You Can Do Today

Pick up your phone and record the material change or die change process on your production line, that's it!

Article Category: Lean Production

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