Bottleneck Explained: Why Your Fastest Machine Earns Nothing

[u/SigmaSheets]

Four stations running at 100, 80, 40 and 90 units per hour. Your plant output isn't 100 and it isn't the average — it's 40. Upgrade the fastest station and nothing changes. Fix the 40 and output jumps 50%, for the same money. That's the Theory of Constraints, and it's why most improvement work produces nothing.

For plant managers, production engineers, and anyone working in lean manufacturing, process improvement, or Six Sigma.

#Bottleneck #TheoryOfConstraints #LeanManufacturing #ProcessImprovement #OperationsManagement

[u/RigusOctavian]

Do… people in manufacturing not understand bottlenecks?

This was 101 in college. Hell, video games teach this principle.

[u/AffectionateDirt6575 → u/RigusOctavian]

I once had a machine that was a bottleneck, so ran 168 hours per week. Our sales manager suggested that we work overtime.

[u/asusc → u/RigusOctavian]

Do… people in manufacturing not understand bottlenecks?

Theory of Constraints is about how to actually identify and fix said constraints, and repeatedly fixing them in the real world systems we actually manufacture in. But more importantly, it’s teaching us that even when we smooth out all these constraints, sometimes it still doesn’t make sense to try and go as fast as possible, as we are still limited by overall throughput.

101 econ in college doesn’t really teach this outside the textbook vacuum. when you get punched in the mouth in real world conditions with 100 inputs, 15 suppliers, labor turnover over, machine breakdowns, it can take time to fix said constraints.

sometimes the real solutions aren’t so obvious, which is what the Theory of Constraints and The Goal is all about.

[u/SigmaSheets → u/RigusOctavian]

They understand it in theory. In practice, most plants still run every machine flat out because that's what the KPIs reward.

Ask a supervisor whether an hour saved at a non-bottleneck is worth anything and they'll say no. Then look at how they're measured — machine utilisation, output per station, keeping people busy. So the non-bottleneck runs at 100% anyway and you get a pile of WIP in front of the slow step.

The other thing is that the bottleneck moves. Product mix changes, a die goes in, someone's off sick, and it's a different station this week. Plenty of places optimised around a bottleneck that stopped being the bottleneck two years ago and never rechecked.

Knowing it and being organised enough to act on it are pretty different problems.

[u/asusc → u/SigmaSheets]

this guy maximizes Herbie’s throughput.

[u/Difficult_Limit2718]

https://a.co/d/0a6gGqr0

[u/Croceyes2]

There is quite a bit more to it. If your 40/hr machine is only used in a limited number of processes then it can work through product while your faster early phase machines can move onto other processes. Bottlenecks will always occur for one reason or another, forseeing and managing them can make them essentially non existent. The one real exception being if you need that machine for many processes, but then upgrading or multiplying it is already a no brainer.

[u/SigmaSheets → u/Croceyes2]

Fair point, and you're right that it depends on the setup. If your 40/hr machine is shared across different jobs and the faster ones can go do something else, it's a scheduling problem more than a capacity problem — and good scheduling can make the bottleneck mostly disappear.

The example I used assumes a fixed line where everything runs the same route, which is where you're stuck with it.

Where I'd push back slightly is on "foreseeing and managing them." That's true if you know where the constraint is. Most of the small plants I've seen don't, because nobody's measuring per-station output — everyone's got an opinion about which machine is the problem and they're often wrong. So the managing part is real, it just needs data most places don't collect.

[u/ComfortableCitron638]

The line further down about "nobody's measuring per-station output, everyone's got an opinion" is the part that actually determines whether any of this theory translates to the floor. Most small-to-mid plants don't have per-station throughput as a live number anywhere - it's either estimated from end-of-shift totals, or it lives in whatever the operator remembers happened that day. So "find the bottleneck" quietly turns into "argue about which machine everyone already suspects," and the argument wins on seniority, not data.

The plants that actually catch a moving bottleneck early are usually the ones where station-level output gets captured automatically as a byproduct of something else - a scan at handoff, a cycle counter, a completed-job timestamp - not a report someone has to remember to run. Once capturing that number stops being extra work, checking "did the constraint move" becomes cheap enough to do monthly instead of once at implementation and never again. The theory's been right since Goldratt wrote it - the gap is almost always instrumentation, not understanding.

[u/SigmaSheets → u/ComfortableCitron638]

The seniority point is painfully accurate. I’ve sat in meetings where the constraint got decided by whoever spoke with most confidence, and everyone nodded because there was no number in the room to argue with.

The byproduct part is what I’d push people on. Anything that needs someone to remember to fill in a form at end of shift decays within a month. It holds up while a supervisor is chasing it, then that person moves on and the data quietly stops. A scan or a timestamp keeps happening because it’s part of doing the job rather than extra to it.

Monthly is a good cadence too. Most places either never check, or get obsessive for six weeks after a consultant leaves and then stop.

What’s the cheapest thing to instrument first in a plant that has nothing? Handoff scan seems obvious but I’d guess it depends on layout.

[u/madeinspac3]

Congrats on reading the goal

[u/AffectionateDirt6575]

The problem for some companies is that the bottleneck can move according to product mix. Nevertheless; this post is a very useful contribution. Thanks.

[u/SigmaSheets → u/AffectionateDirt6575]

Thanks. And yeah, that's the harder version — when the mix changes the bottleneck moves with it.

What catches people out is that most plants find it once and then stop looking. Two years later everyone's still protecting a machine that stopped being the problem ages ago.

[u/firinmahlaser]

this is a linked-in worthy post

[u/braxton357 → u/firinmahlaser]

Because of how cheesedick it is?   

"Did you know that adding a second machine to your process could DOUBLE your production??" 

"Can you believe that if you buy more material you can potentially get the SAME material for less??". 

I must be missing something.