What is speed loss in OEE?

Speed loss is any time a machine runs slower than its ideal cycle time while it is up and running. It is the fourth of the six big losses and one of the two Performance losses. If the ideal rate is one part every two seconds and you are averaging one every 2.5 seconds, that 20 percent difference is speed loss, produced with no logged stop, which is why it hides.

What is the difference between speed loss and minor stops?

Both are Performance losses, but reduced speed means the machine runs continuously below rate, while a minor stop means it briefly halts and restarts. In the count stream, speed loss shows as a rate steadily below ideal with no gaps, and minor stops show as frequent short gaps. They are fixed differently, so the first step in diagnosis is telling them apart.

Why does a machine run below its rated speed?

Usually one of three causes: worn or degraded equipment such as dull tooling or slipping drives, a conservative setting or informal derate left in place from an old problem, or a starved infeed or blocked outfeed where the real constraint is elsewhere on the line. Each has a different fix, so identifying the family before acting matters.

What is a ghost derate?

A ghost derate is a speed setting someone reduced during a past problem and never restored, even though the reason is long gone. It is one of the most common causes of speed loss and one of the cheapest to fix: restore the rate under supervision, and if the line runs clean, the derate was costing output for nothing. If a defect reappears, you have surfaced the real problem to fix.

How much OEE can fixing speed loss recover?

Often more than any other loss, because it is invisible to downtime logs. A line running at 80 percent of ideal rate carries a 20-point Performance loss with no stops recorded. Closing half of it lifts Performance about 10 points, which flows straight through the OEE calculation into 10 points of overall score without adding any run time.

Diagnosing Speed Loss

Q: How do you measure actual cycle time?

Divide run time by total count over a window when the machine was up. A single counter on the discharge plus an honest record of run time gives the actual rate, and comparing that to the ideal cycle time gives the speed loss. You do not need a sensor on every axis, you need a clean count and a clean run-time number.

The machine never stops, so nobody logs it, and the line quietly leaves units on the table every minute. Here is how to find out why it runs slow.

Speed loss is the gap between how fast a machine could run at its ideal cycle time and how fast it actually runs. Diagnosing it means isolating one of three causes, worn parts, conservative settings, or a starved or blocked flow, by testing them in order instead of guessing. Speed loss lives in the Performance factor of OEE.

Speed loss is the quietest of the six big losses because the machine never stops. It runs, parts come off, the shift feels productive, and all the while the line is leaving units on the table every minute. Nobody logs it because nothing failed. That is exactly why it needs a method: you cannot see reduced speed by watching the line, only by comparing the count you got to the count the machine is capable of.

What is speed loss?

Speed loss is any time the machine runs slower than its ideal cycle time while it is up and running. It is the fourth of the six big losses and one of the two Performance losses, alongside minor stops. The math is a direct comparison: your ideal cycle time says the machine should make a part every 2.0 seconds, your counts say you are averaging 2.5, and that 0.5 second per part, 20 percent, is pure speed loss, produced without a single logged stop.

Keep speed loss separate from minor stops even though both hit Performance. A minor stop is a brief halt, a jam cleared in seconds, a sensor fault, where the machine actually stops. Reduced speed is the machine running continuously but slow. They feel identical in the OEE number and they are fixed differently, so the first job of diagnosis is telling them apart: minor stops show as gaps in the count stream, reduced speed shows as a count rate that is steadily below ideal with no gaps.

Speed loss is the shaded band: real output running steadily under the ideal rate with no stops to log. It is invisible on paper and only appears when you compare counts to ideal cycle time.

Why do machines run below rate?

Almost every case falls into one of three families, and they have completely different fixes. Guessing which family you are in is how plants waste a maintenance weekend on a machine that was simply set to run slow.

Worn or degraded equipment. Dull tooling, slipping drives, buildup on rollers, worn bearings adding drag, misaligned guides that force a slower feed. The machine cannot hit rate anymore because it is not in the condition it was specified for. This is where machine monitoring and condition data earn their keep.
Conservative settings and informal derates. The rate is dialed down and left there. "We always run it at 80 percent because it jams at full speed." Sometimes that derate is hiding a real defect; often it is a ghost, a setting someone reduced during a bad batch two years ago that nobody ever restored. Every informal derate is either a fixable problem or a wrong standard.
A starved infeed or a blocked outfeed. The machine itself is fine, but it cannot run at rate because the upstream station is not feeding it or the downstream station cannot take its output. The constraint is somewhere else on the line, and the slow machine is just where the symptom shows. This is a bottleneck question, not a machine question.

How do you diagnose speed loss step by step?

Work from the cheapest, most reversible test to the most invasive. The order matters, checking the setting takes a minute, tearing into the gearbox takes a shift:

Confirm it is really speed loss. Pull the count stream. Steady counts below ideal rate with no gaps means reduced speed; frequent short gaps means you are chasing minor stops instead, which is a different fix. Do not diagnose speed until you have ruled out stops.
Check the set rate first. Read the actual speed setting on the machine and compare it to the design rate behind your ideal cycle time. If someone has dialed it down, you have found a candidate in sixty seconds, now ask why, and whether the reason still exists.
Test for starve and block. Watch the infeed and outfeed for one full cycle at rate. Is the machine ever waiting for parts, or backing up because it cannot discharge? If so, the constraint is upstream or downstream and the slow machine is innocent.
Look for the derate's reason. If the rate is set low with no starve or block, try restoring it under supervision. If it runs clean at full rate, the derate was a ghost. If it jams or defects at rate, you have surfaced the real defect the derate was hiding, now you have something to fix.
Inspect the mechanical condition. Only now go after wear: tooling sharpness, drive tension, roller and guide condition, bearing drag, alignment. Compare against the machine's spec, not against "how it usually runs," because how it usually runs is the thing you are trying to fix.
Restore, then re-measure. After any change, re-pull the counts and confirm the actual rate moved toward ideal. A fix you cannot see in the count stream did not fix the speed loss, whatever else it accomplished.

The measurement behind every step above:

The OEE Performance factor is defined as ideal cycle time multiplied by total count, divided by run time, equivalently, ideal rate divided by actual rate. That formula and the treatment of reduced speed as a Performance loss are documented in the OEE calculation reference at OEE.com's calculating-OEE guide. Speed loss is simply Performance falling below 100 percent for reasons other than short stops.
Reduced speed is one of the classic six big losses catalogued from Seiichi Nakajima's TPM work; the taxonomy that separates reduced speed from idling and minor stops is laid out in the six big losses reference. Both are Performance losses, which is why they blur together in the OEE number and must be separated by hand.

What does each cause look like, and how do you fix it?

The table maps the three families to the symptom you will see, the test that confirms it, and the fix. Run the tests in the order above; do not skip to the expensive column.

Cause family	Symptom	Confirming test	Fix
Conservative setting / derate	Set speed below design rate	Restore rate; runs clean	Update the standard; retrain
Hidden defect behind a derate	Set speed low; jams at full rate	Restore rate; defect appears	Root-cause the defect, then restore
Starved infeed	Machine waits for parts	Watch infeed one cycle	Fix the upstream constraint
Blocked outfeed	Machine backs up, cannot discharge	Watch outfeed one cycle	Fix the downstream constraint
Worn tooling / drives	Rate drifts down as tools age	Compare condition to spec	Replace, tension, align, clean

Match the fix to the confirmed cause. The two most common findings, a ghost derate and a downstream starve, cost nothing to test and nothing to fix.

How do you measure actual cycle time without a fleet of sensors?

You do not need a sensor per axis, you need a good count and a clean run-time number. Actual cycle time is just run time divided by total count over a window where the machine was up. A single counter on the discharge and an honest record of when the machine was running gives you the actual rate; comparing that to your ideal cycle time gives you the speed loss. The full comparison, and the traps in setting the ideal number, are covered in theoretical vs actual cycle time.

The one number that makes or breaks the whole diagnosis is the ideal cycle time you measure against. Set it too slow, to a rate the line has been quietly running for years, and real speed loss vanishes into a comfortable standard. Set it to the manufacturer's nameplate for a machine that will never see those conditions again and every shift looks like a failure. Anchor the ideal to a demonstrated best sustained rate, and revisit it, or you are diagnosing against a moving target. This is one of the common OEE mistakes that quietly corrupts a program.

Cheapest test first. Two of the four checks cost only a minute of watching, and they catch the two most common causes before anyone opens a gearbox.

How does fixing speed loss move OEE?

Straight into Performance, and it is often the largest untapped gain on the board. A line running at 80 percent of ideal rate is carrying a 20-point Performance loss that no downtime log will ever show. Close half of it and Performance climbs 10 points, which flows through the OEE multiplication into 10 points of overall score, without adding an hour of run time. You can price the exact gain for your line with the OEE calculator or the full OEE calculation method.

Speed loss belongs on the same Pareto as every other loss. It is the fourth of the six big losses and it competes with breakdowns, setups, and minor stops for your improvement hours, so it should be tracked as one of your manufacturing KPIs and funded by its size, not its drama. The catch is that you cannot Pareto what you cannot see, and speed loss is invisible to paper logs by definition. Plants that stream counts and run time straight off the line, the way Harmony's machine-data intelligence does (see the platform), surface reduced-speed losses that clipboards had rounded away for years. The units were never being made. Nobody could prove it until the count told on the machine.