Chapter 17: Analysing Machine Utilisation — The Three Numbers That Expose Your Hidden Capacity
In the last chapter, we established your Takt Time: the precise beat your production line must hit to meet demand without overproducing or falling behind. We landed on a working example — a 22kg roaster needing to drop a finished batch every 11 minutes to satisfy 4,500kg of weekly demand.
That number is a target. This chapter is about whether your machine can actually hit it — and the answer almost always reveals that the capacity you're about to spend six figures to buy is already sitting on your floor, unused.
To find it, we use the single most clarifying metric in manufacturing: Overall Equipment Effectiveness.
What OEE Actually Measures
OEE is not a vanity number. It is a brutally honest multiplication of three separate realities, each expressed as a percentage:
OEE = Availability × Performance × Quality
Each factor answers a different question, and because they're multiplied together, a weakness in any one of them collapses the whole score. This is what makes OEE so revealing — it punishes the hidden losses that single metrics conveniently hide.
- Availability asks: Of the time the machine was scheduled to run, how much was it actually roasting? This is where unplanned stops live — waiting on green to be staged, a cooling tray that hasn't cleared, an operator pulled away, a burner relight. Every minute the drum is hot but empty is an availability loss.
- Performance asks: When it was running, did it run at its ideal pace? A roaster nursed through slow, cautious profiles, or held back by a destoner that can't keep up, is bleeding performance even while it's technically "working."
- Quality asks: Of what it produced, how much was actually sellable? Scorched batches, tipping, underdeveloped roasts, and bean defects that should have been sorted out upstream all erode this figure.
The Math That Stops a Bad Purchase
Here's why OEE is so dangerous to a machinery salesman. Let's take a roastery that feels maxed out:
- Availability: The drum is scheduled for 7 hours, but staging delays, slow tray turnarounds, and between-batch gaps mean it's only actually roasting for 4.5 of them. That's 64%.
- Performance: When running, cautious profiles and a lagging destoner mean it hits only 80% of its ideal batch pace.
- Quality: A solid 95% of output is sellable.
Multiply them: 0.64 × 0.80 × 0.95 = just under 49%.
That roaster — the one the owner is convinced is too small — is delivering less than half its true potential. The machine isn't the constraint. The process around it is. World-class OEE sits around 85%. Closing even part of that gap can effectively double output without a single new bolt of steel.
The Lean Angle: OEE Exposes the Six Big Losses
In Lean and TPM (Total Productive Maintenance), OEE isn't just a scorecard — it's a map. Each of the three factors points to a specific family of waste. Low availability points to breakdowns and changeover losses. Low performance points to minor stops and reduced speed. Low quality points to defects and start-up rejects. You cannot fix what you refuse to measure, and OEE forces you to confront exactly where your hours are leaking.
The bigger machine doesn't fix any of these losses. It simply scales them up — you buy a larger drum and inherit the same 49% efficiency, now wrapped around a much bigger loan repayment.
The Specialist Technician's Action Plan
To find your hidden capacity before signing any purchase order, work through these steps:
- Track One Week of Real Run-Time: For five working days, log the actual minutes your drum spends roasting versus the minutes it's scheduled to run. Be ruthless about counting "hot but empty" time as a loss. This single number — your Availability — is usually the biggest shock.
- Benchmark Your Ideal Cycle: Establish the genuine fastest stable batch cycle your machine can run for your core profiles. Compare your real average against it to calculate Performance. The gap is almost always larger than operators believe.
- Audit Your Reject Rate Honestly: Count every batch or portion downgraded, blended off, or binned over a week to find your true Quality figure. Don't round up out of pride.
- Multiply, Then Hunt the Biggest Loss: Calculate your OEE, then attack the lowest of the three factors first. That single number is your cheapest, fastest path to more capacity — and it costs nothing but attention.
The Tech Note: "The first time I run an OEE audit with an owner, the number almost always comes back under 50%, and there's usually a long silence in the room. Then I point at the cooling tray, or the manual green staging, or the destoner that can't keep up — and I tell them the bigger roaster they were quoting would have done absolutely nothing except make the same problem more expensive. Your capacity isn't missing. It's hiding in plain sight." — JG