Lean Foundations — Lesson 4: SMED: Quick Changeover — Smaller Batches Without Losing Capacity

Lean Foundations · 4 min read · 22.09.2026

Welcome to the fourth lesson in the Lean Basics series. Today we're looking at changeover — the moment when the machine sits idle and the line waits. You'll learn to tell internal and external setup apart, cut machine changeover time by up to half, and produce smaller batches without losing capacity. For the exercise you need only a phone and two hours of observation on the shop floor.

Why Large Batches Get Made

In the first lesson, we described the seven types of waste. Two of them — overproduction and inventory — often share a common root: a long changeover. When a press changeover takes three hours, the foreman does the one sensible thing. He runs five thousand pieces at a time, paying for those three hours only once.

Batch size is therefore tied to changeover time. The longer the changeover takes, the larger the batch that “pays off.” You know the consequences from the lesson on value stream mapping: intermediate storage, tied-up capital, long lead times. If the customer changes an order, half the batch ends up on a shelf; a defect means 5,000 faulty pieces instead of 300.

SMED (Single Minute Exchange of Die), quick changeover, attacks the cause. Shigeo Shingo developed the method while working on press changeovers in Japanese automotive plants. The name states the goal: a changeover in single-digit minutes. That's when producing in smaller batches pays off. Same machine, same capacity — shorter flow and lower inventory.

Internal and External Setup

The method rests on one distinction. During a changeover, you perform two kinds of activities:

• Internal setup requires the machine to be stopped: removing the tool, mounting the new one, centering, the first test piece.
• External setup can be handled while production is running: preparing and checking the tool, hunting for wrenches, paperwork, preheating material.

For every activity one key question applies: does the machine have to stand still?

In projects at Foreast, we keep seeing the same picture. We film a changeover the foreman calls “two hours, that's just how it is.” On the video we measure 40 minutes of actual work and 80 minutes of walking, searching, and waiting for the crane. The machine didn't have to stand still for those 80 minutes. Half of the supposed changeover was poorly organized work around the machine.

The first wave requires no investment in technology. It's enough to move the external activities to before the machine stops. Quick-release clamps and universal holders come in the second wave — for what's left.

Changeover time is not a property of the machine. It is the sum of habits — and habits can be changed.

Four Steps to a Fast Changeover

1. Film the current process. Phone on a tripod, one complete changeover. Without video, you remember your own version, not reality.
2. Divide up every minute. Internal, or external? Record the waiting times too — for a second person, the crane, material.
3. Turn internal into external. Tool prepared and checked before the machine stops, tool cart in place, setting values written down.
4. Simplify the remaining internal setup. Two operators working in parallel, quick-lock clamping instead of bolting, the same mounting heights on all tools.

At a mid-sized supplier's press shop, this procedure shortened a changeover from 180 to 35 minutes. The single technical change was identical mounting bases for all dies. The rest came from a preparation checklist and splitting tasks between two people, so the exchange runs in parallel, not in sequence. The company then moved to batches of 800 pieces instead of 4,000, and the intermediate stock in front of the press fell by 70 percent. The same approach works on presses, injection molding machines, and welding — anything that stops the machine counts.

This Week's Exercise

Pick the machine that gets changed over most often and film one complete changeover. Shoot from the last piece of the previous batch to the first good piece of the new one. Divide the activities into internal and external and count the minutes in both groups. Write the time spent searching and waiting separately — those are your cheapest minutes.

Then make a single intervention: at the next changeover, have the team ready a tool basket and a checked tool while the machine is still running. Measure the new time and compare. Most teams find the first attempt saves 20 to 40 minutes without any investment. With ten changeovers a month, half an hour saved means five hours of capacity a month — for free.

Shortening the changeover, however, is only half the job. The other half is sustaining the new procedure — the same at every change, not just in the hands of whoever filmed it. On projects we see that improvement without a standard fades away within a few weeks. That's exactly what the next lesson in the series is about: standardized work, the best known method for everyone. If you'd like to work through SMED on your machines with our consultants, take a look at our e-learning offer.

Quiz — test your knowledge