Capacity verification calculator

Enter your line configuration and measured cycle time. This calculator returns net available time, effective cycle time, demonstrated capacity, utilization against your required rate, and a pass or fail verdict. It runs the same math as the RateProof app.

How to read the result

Two things are measured, and the higher of the two governs. Part capability utilization asks what share of an operation's output the requirement consumes. Machine utilization asks what share of its available time the operation consumes once downtime and the overproduction needed to cover scrap are both paid for. An operation can have plenty of output headroom and still be bound by time, so the binding figure is whichever is larger.

Below 85 percent the operation runs with headroom. From 85 percent it is worth watching. From 90 percent it passes with no margin for a bad shift, which is high risk. At 100 percent or beyond it cannot meet the requirement and fails. Separately, if planned downtime consumes the entire scheduled budget the operation has no time to run at all, which is reported as its own failure rather than as a shortfall.

When a study has several operations, the one with the highest governing utilization sets the capacity of the whole line. That operation is the constraint. It is not always the one with the least output: downstream scrap and downtime burden both move it.

Each operation also carries its own requirement, which is higher than the contracted rate whenever later operations scrap parts. An operation feeding a step that scraps 10 percent must produce about 11 percent more than the contracted figure, because roughly a tenth of what it makes never ships.

What each input means

Shifts per day and hours per shift

Scheduled production time before any downtime is subtracted. Fractional values are accepted, so a two and a half shift pattern is entered as 2.5.

Parallel machines

The number of machines running this same operation at the same time. Net available time is multiplied by this count, because two identical machines give you twice the available time.

Parts per cycle

How many parts one machine cycle produces. A four cavity tool produces four parts per cycle, so the effective cycle time per part is a quarter of the measured cycle time.

Planned downtime per machine

The total downtime allowance for the operation, in minutes, per machine. Include scheduled breaks and lunch, changeovers, planned maintenance, any other downtime, and your estimated unplanned allowance. The app totals those same five figures into the number it uses here, so leaving the unplanned allowance out would give you more capacity on this page than the app reports for the same study.

What does not belong here is downtime you actually observe hour by hour once the run is under way. That goes in the production run tally, where it is used differently. It normalizes the live projection to productive time rather than reducing it: logging an hour with 10 minutes of downtime tells the app you produced those parts in 50 running minutes, not 60, so your rate is measured over the time you were actually running. At a steady productive rate, recording downtime leaves the projection unchanged.

Average cycle time

The measured time for one machine cycle, in seconds. This should come from timing real cycles during production, not from the quoted or theoretical cycle time.

Scrap rate

The percentage of produced parts that are not sellable. Demonstrated capacity is reduced by this yield loss, because parts you scrap do not count toward the required rate.

Worked example

A line runs three shifts a day at eight hours a shift, which is 1,440 scheduled minutes per machine. Planned downtime is 200 minutes per machine, leaving 1,240 minutes. Two machines run this operation in parallel, so net available time is 2,480 minutes.

The measured cycle time is 30 seconds and the tool produces two parts per cycle, so the effective cycle time is 15 seconds per part. That gives 2,480 minutes times 60, divided by 15, which is 9,920 parts. A scrap rate of 5 percent reduces that to a demonstrated capacity of 9,424 parts per day.

Against a required rate of 9,000 parts per day, part capability utilization is 95.5 percent. Machine utilization is higher and therefore governs: the 400 minutes of downtime plus the 2,362.5 minutes needed to produce 9,000 parts at 5 percent scrap consume 95.9 percent of the 2,880 gross minutes available. The result is high risk. There is very little room between what this line demonstrated and what the customer requires, and the time based measure shows even less room than the output based one.

What this calculator does not do

This page does the arithmetic. It does not time cycles for you on the floor, tally good parts, scrap and downtime hour by hour through a production run, or produce the report your customer expects to receive.

That is what RateProof does. It runs this same math on an iPhone or iPad at the line, with a full screen stopwatch, a live production run tally, and audit ready PDF and Excel exports. The math on this page is the app's math, so what you see here is what the app will calculate.