Lean, TPM or TOC
Which Would Fix This Line First?

Ask three improvement schools what to fix first on the same line and you get three different answers. Each one follows a sound rule. We scored all three on a validated ReliaSim® model of a bottling line. None of them found the move that adds the most output, and the model could test every one of them on equal terms.

The line

Five machines in a row: a Filler, a Capper, a Labeler, a Case Packer and a Palletizer, fed from bulk storage and feeding a warehouse. Every machine runs at 100 bottles a minute, so on paper there is no slow machine to blame. Running 24/7 with no stops, the line would make 129,600 pallets in 90 days.

It doesn’t. Thirty-six different interrupts stop it, each with its own pattern of how long the machine runs before it stops and how long it stays down, fitted from the line’s own stop data. Across ten randomized 90-day runs the line delivers 54.3% of what it could. The model matches the line’s own uptime interrupt by interrupt before anyone trusts what it says.

Each school gets one move, starting from the line as it is: fix one problem, or add buffers between the machines.

What each school recommends

Lean: cut the biggest waste

Lean ranks the losses and goes after the biggest one on the downtime chart. Here that’s the Capper’s Upper Plow Area, which kept the line down 198 hours in 90 days, more than any other interrupt. Lean also treats buffers as inventory, and inventory as waste, so it adds none.

TPM: fix the worst machine

Total Productive Maintenance looks after the equipment and goes after chronic losses on the machine that’s down the most. That’s the Capper, available 75.9% of the time, and its most frequent stop is its micro stops: 5,816 of them in 90 days. TPM’s pick is the Capper’s minor stops.

TOC: protect the constraint

The Theory of Constraints finds the constraint and protects it. With every machine at the same speed, the constraint is the machine that’s down the most, again the Capper. TOC protects it with a buffer: all four buffer slots right after the Capper.

How each one scored

Each recommendation went into the same model and ran ten times, 90 days each, with every other stop on the line still in place. The score is line efficiency: pallets made, as a share of the 129,600 a line that never stops would make.

All three schools improve the line. None of them finds the best move. The model tried every one of the 36 fixes and every legal way to place the buffers, and its best move beats the best school by 3.5 points, on the same line, with the same one move. We leave that move out here, because it’s the answer to the game.

Why each rule stops short

The biggest loss isn’t the costliest

Lean’s chart counts hours down. On a line with no buffers, what an hour costs depends on what the stop does to the machines around it. The Upper Plow Area is a sound pick, and still not the best fix: removing a different interrupt, one that costs fewer hours, gives back more. A downtime chart ranks occurrence; the line ranks what each stop does to output. See which loss to fix first.

The worst machine isn’t where the best fix is

TPM goes to the machine with the lowest availability, and to the most frequent stop on it. Frequency is real, but the Capper’s micro stops are short, and fixing them moves the line only from 54.3% to 57.1%, the lowest of the three. Looking after the equipment is right; choosing the target by availability alone is what misleads it here. See micro stops vs breakdowns.

TOC is right about the constraint, not about the buffer

TOC protects the right machine and scores best of the three schools. What it doesn’t say is how much buffer, or where. Putting all of it straight after the Capper is a fair reading of “protect the constraint”, and the model shows a better placement exists. With every machine at the same speed, the constraint also moves from stop to stop. See theory of constraints simulation and how big should a buffer be?

Not a fourth school: a test bench for all of them

ReliaSim doesn’t compete with Lean, TPM or TOC. It doesn’t ask you to drop the method your plant runs on. It gives that method a place to be tested before the line pays for it.

Whatever the rule says, the model can run it. Cut a waste and the interrupt comes out of the model. Do a maintenance project and the failure pattern changes: stops come less often, or end sooner. Protect the constraint and a buffer goes in where the rule puts it, at the size it calls for. A SMED project shortens a changeover, a speed-up raises a rate, and a new shift pattern changes the calendar. Each one is a change to the model, and each runs on the same line with every other stop still in place.

That also means the schools stop being an argument. A Lean team, a maintenance team and a TOC advocate can each bring their first move, and the line scores all of them the same way: what each one gives back in output. The rule that wins on one line can lose on the next. Testing is how you learn which one holds on yours.

Try it on this line

Beat the Bottleneck runs this exact comparison. You get one move on the same line, it’s scored over ten 90-day runs, and then you see what Lean, TPM and TOC would have done.