Why is my planned output never achieved?

Nine times out of ten the availability figure. It is the input a plan is most sensitive to and the one most often taken from a good period, and because this page multiplies by scheduled hours the error is amplified into a daily commitment. Measure it over a quarter rather than a week, and include the things nobody logs. Waiting for material, warming up after a restart, the last ten minutes of a shift.

Should downtime come out of scheduled hours or availability?

Availability, and only availability. Scheduled hours is the shift pattern; availability is what survives inside it. Taking it out of both is the commonest double-count here and it compounds, because two 15% deductions leave 72% rather than 85%.

Why don't the recovery rows add up to the shortfall?

Because availability and yield multiply. Some parts would have been rejected during time the line was not running, and that overlap is not recovered by either fix alone. It is small when both figures are good and grows quickly when they are not. At 65% availability and 90% yield it is over 180 parts a day, which is more than the whole yield-alone recovery.

Which project should I fund?

Compare the two single-fix rows against what each costs. On a line with cure under control, availability usually dominates by a wide margin, which is the finding here. But the ranking is a property of your numbers, not a rule. A line with a marginal cure window can easily invert it, and that is exactly why the two figures are reported separately rather than summarised.

Does this include rework?

No. Parts recovered by re-curing are not first-pass good, so they belong in the reject side here with their cost on the rework page. Counting them as good on this page and also costing them there records the same parts twice and flatters both numbers.

Is the cure station my constraint?

This page cannot tell you, and the question decides what its answer is worth. If a downstream step is slower, the line ships at that step's rate and improving cure capacity buys nothing but work-in-progress. Establish the constraint first; a capacity figure for a non-bottleneck describes potential, not output.

UV Curing calculator

UV Line Capacity Calculator: Daily Output and What Each Fix Returns

Turn an hourly production rate into a daily figure a plan can be built on, and see what each improvement would really return. Enter the cured parts per hour at running speed, the scheduled hours, line availability and first-pass cure yield. The calculator returns gross and net daily output, then splits the shortfall three ways: availability alone, yield alone, and the part that only arrives if both are fixed. the earlier version published two loss rows that added up neatly to the total, which they can only do if one of them has absorbed an overlap belonging to neither.

What this calculator does

Turn an hourly cured-part rate and a schedule into daily good output, with an honest split of the shortfall between availability, yield, and the overlap that needs both.
Use it for building a daily production plan from a line rate, ranking an availability project against a cure-yield project, testing how sensitive a plan is to the availability assumption, estimating the output of a second shift, explaining why two improvement estimates cannot be added.
Turn an hourly cured-part rate and a schedule into daily good output, with an honest split of the shortfall between availability, yield, and the overlap that needs both.

Formula used

Gross daily capacity = cured parts per hour × scheduled hours per day
Net good parts/day = gross × availability × first-pass yield
Recovered by fixing availability alone = gross × (1 − availability) × yield
Recovered by fixing yield alone = gross × availability × (1 − yield)
Recovered only by fixing both = gross × (1 − availability) × (1 − yield)

Inputs explained

Cured parts per hour at speed: Rate the line produces at while genuinely running, at a speed that delivers the required dose.
Scheduled run hours per day: Hours the line is scheduled to run. Availability handles what is lost inside them, so do not deduct downtime here as well.
Line availability / uptime: Share of scheduled hours the line actually runs, after changeovers, breakdowns, material waits and lamp warm-up.
First-pass cure yield: Share of parts passing on cure at the first attempt. Cure defects only.

How to use the result

Best suited to building a daily production plan from a line rate, ranking an availability project against a cure-yield project, testing how sensitive a plan is to the availability assumption, estimating the output of a second shift, explaining why two improvement estimates cannot be added.
Cannot verify the hourly rate cures. A line running above its cure window makes this number and no good parts. Assumes availability and yield are independent, when a line that stops frequently often also runs unstable. Averages availability across the day, so a line that runs perfectly and then stops for three hours reads the same as one that stutters all day: very different for scheduling. Excludes rework, which can return some rejects to good output at a cost carried elsewhere. Says nothing about whether the cure station is the constraint; it may not be the slowest step in the line.

Common questions

Why is my planned output never achieved? Nine times out of ten the availability figure. It is the input a plan is most sensitive to and the one most often taken from a good period, and because this page multiplies by scheduled hours the error is amplified into a daily commitment. Measure it over a quarter rather than a week, and include the things nobody logs. Waiting for material, warming up after a restart, the last ten minutes of a shift.
Should downtime come out of scheduled hours or availability? Availability, and only availability. Scheduled hours is the shift pattern; availability is what survives inside it. Taking it out of both is the commonest double-count here and it compounds, because two 15% deductions leave 72% rather than 85%.
Why don't the recovery rows add up to the shortfall? Because availability and yield multiply. Some parts would have been rejected during time the line was not running, and that overlap is not recovered by either fix alone. It is small when both figures are good and grows quickly when they are not. At 65% availability and 90% yield it is over 180 parts a day, which is more than the whole yield-alone recovery.
Which project should I fund? Compare the two single-fix rows against what each costs. On a line with cure under control, availability usually dominates by a wide margin, which is the finding here. But the ranking is a property of your numbers, not a rule. A line with a marginal cure window can easily invert it, and that is exactly why the two figures are reported separately rather than summarised.
Does this include rework? No. Parts recovered by re-curing are not first-pass good, so they belong in the reject side here with their cost on the rework page. Counting them as good on this page and also costing them there records the same parts twice and flatters both numbers.

Last reviewed 2026-08-25.