RateProof Capacity Study
Capacity study template, field by field
Every capacity study needs the same fields and the same formulas, whether it lives on paper, in a spreadsheet or in an app. This page lists them, fills them in for a three operation line, and explains why a copied spreadsheet slowly stops computing what it claims to.
Need it working now? The free capacity verification calculator is this template with the formulas running. Enter your operations and it works out net available time, effective cycle time, demonstrated capacity, the requirement at each operation, both utilization measures, the risk band and the constraint.
The fields a study needs
A template has three parts: what the study is about, what you enter for each operation, and what the formulas make of it. When and how to collect the inputs is covered in how to run a capacity verification study.
About the study
- Part number and name
- The part the study covers. Several part numbers built on the same line add their daily volumes together.
- Supplier, site and engineer
- Who ran the study, at which plant.
- Date of the run
- When the cycles were timed and the run was tallied.
- Required parts per day
- The customer's contracted volume, converted to a daily rate over the working pattern the line runs.
- Notes
- Anything a reviewer needs to judge the evidence: crew, material, anything unusual about the run.
Entered for each operation
| Field | Unit | What goes in it |
|---|---|---|
| Operation | name | In process order, the final operation last. |
| Shifts per day | count | Fractions are allowed: two and a half shifts is 2.5. |
| Hours per shift | hours | Scheduled hours, before any downtime. |
| Parallel machines | count | Machines running this same operation at the same time. |
| Parts per cycle | count | Cavities, nests or basket size. |
| Breaks and lunch | minutes | Per machine per day, whenever the machine stops for them. |
| Changeover | minutes, days | Minutes for one changeover and the days between them. One 45 minute changeover every two days costs 22.5 minutes a day. |
| Planned maintenance | minutes | Per machine per day. |
| Other planned downtime | minutes | Start up, material changes, meetings: any other scheduled stop. |
| Unplanned allowance | minutes | An honest estimate of unplanned stops. Never zero. |
| Measured cycle time | seconds | The average of cycles timed at the line, with the timed cycles kept as evidence. |
| Scrap rate | percent | Parts this operation makes that cannot ship. |
Calculated for each operation
Scrap rates enter these formulas as fractions: 1.5 percent is 0.015.
- Scheduled minutes
- Shifts per day × hours per shift × 60, for each machine.
- Planned downtime
- Breaks and lunch + changeover minutes ÷ days between changeovers + planned maintenance + other planned downtime + unplanned allowance, for each machine.
- Net available time
- (Scheduled minutes minus planned downtime) × parallel machines, and never below zero.
- Effective cycle time
- Measured cycle time ÷ parts per cycle.
- Demonstrated capacity
- Net available time × 60 ÷ effective cycle time × (1 minus scrap rate).
- Downstream scrap
- The scrap rates of every later operation, added together.
- Requirement here
- Required parts per day ÷ (1 minus downstream scrap), shown rounded up to a whole part. When downstream scrap reaches 100 percent no requirement is attainable, and the operation fails.
- Part capability utilization
- Requirement here ÷ demonstrated capacity.
- Machine utilization
- (Planned downtime of all machines + required parts per day × (1 + own scrap + downstream scrap) × effective cycle time ÷ 60) ÷ scheduled minutes of all machines. The scrap terms are an overproduction allowance added to the required rate.
- Governing utilization
- The higher of the two, named, because the remedies differ: more output for one, less downtime or less overproduction for the other.
- Risk band
- Low risk below 85 percent, medium from 85, high from 90, fail at 100 or more. An operation whose downtime consumes its whole schedule fails with no time available.
- Constraint
- The operation with the highest governing utilization. It sets the capacity of the line.
Two inputs are carried at a fixed resolution before any arithmetic: required parts per day to a thousandth of a part, and each scrap rate to a thousandth of a percent, both rounded up so a study never rests on less demand or less scrap than was entered. After that, rounding applies only to the figures shown. Requirements are shown rounded up, capacities rounded down, and utilization truncated to one decimal, so a figure on the page never crosses a band the line has not reached.
The template, filled in
A bracket line runs molding on two presses with four cavity tools, then an ultrasonic weld cell, then final inspection. The customer requires 2,400 parts per day.
| Bracket line, 2,400 parts per day | Molding | Ultrasonic weld | Final inspection |
|---|---|---|---|
| Entered | |||
| Shifts per day | 2 | 2 | 2 |
| Hours per shift | 8 | 8 | 8 |
| Parallel machines | 2 | 1 | 1 |
| Parts per cycle | 4 | 1 | 1 |
| Breaks and lunch, minutes | 60 | 60 | 60 |
| Changeover, minutes | 45 every 2 days | 0 | 0 |
| Planned maintenance, minutes | 30 | 20 | 0 |
| Other planned downtime, minutes | 30 | 0 | 0 |
| Unplanned allowance, minutes | 30 | 20 | 20 |
| Measured cycle time, seconds | 38 | 20 | 19 |
| Scrap rate, percent | 1.5 | 1 | 0.5 |
| Calculated | |||
| Planned downtime per machine, minutes | 172.5 | 100 | 80 |
| Net available time, minutes | 1,575 | 860 | 880 |
| Effective cycle time, seconds | 9.5 | 20 | 19 |
| Demonstrated capacity, parts per day | 9,798 | 2,554 | 2,765 |
| Downstream scrap | 1.5% | 0.5% | 0% |
| Requirement here, parts per day | 2,437 | 2,413 | 2,400 |
| Part capability utilization | 24.8% | 94.4% | 86.7% |
| Machine utilization | 38.3% | 94.9% | 87.8% |
| Governing utilization | 38.3%machine | 94.9%machine | 87.8%machine |
| Risk band | LOW RISK | HIGH RISK | MEDIUM RISK |
| Constraint | No | Yes | No |
Read the molding column first. Its part capability utilization is only 24.8 percent, yet its machine utilization is 38.3 percent, because 345 of the presses' 1,920 scheduled minutes go to planned downtime before a part is made. Still low risk, but the gap is why a template needs both measures: on a tighter line, time binds long before output does.
The weld cell is the constraint at 94.9 percent. The line passes, at high risk: one bad shift at the weld and the day's requirement is missed, so a study that ends here should carry an action for the weld cell.
To check the example yourself, enter it in the capacity calculator. The calculator takes downtime as one total, so put 172.5 minutes in the molding downtime field.
Why a spreadsheet template drifts
Most capacity templates start as a good spreadsheet. The trouble starts around the tenth copy.
- Formulas get typed over. One study needs a quick fix, a value replaces a formula, and every later copy inherits a cell that no longer computes.
- Ranges stop at the old last row. An operation inserted below a sum or a lookup sits outside it, and the total quietly leaves it out.
- Downstream scrap is applied by hand, or not at all. Each operation's requirement depends on the scrap after it, and that chain is the first thing to break when operations are added or reordered.
- Units drift. Downtime per line or per machine, per shift or per day, cycle time in seconds or minutes: one mismatched cell changes the verdict without changing how the sheet looks.
- Rounding goes the wrong way. A requirement rounded to the nearest part understates demand, and a capacity rounded to the nearest part can overstate it.
- The cycle evidence lives somewhere else. Times written on paper and typed in later lose the samples behind the average, and an outlier deleted from a column leaves no trace.
- Versions multiply. The copy the customer reviewed is not always the copy the plant updated.
How the app replaces the spreadsheet
RateProof Capacity Study runs the formulas on this page, fixed and tested, so a study cannot drift away from its own arithmetic.
- Cycles go straight into the study. A full screen stopwatch with a giant lap button saves every lap when you tap, and an outlier is discarded without being hidden.
- Downtime is entered as the five allowances and totaled for you. A changeover that comes every few days goes in as its daily share.
- Downstream scrap propagates on its own, so every operation carries its own requirement.
- Both utilization measures are computed, the governing one named, with five risk bands and the constraint flagged.
- A live run tally records good parts, scrap and downtime by hour, then sets planned against observed once the run is over.
- PDF and Excel exports. The workbook holds real numeric cells, so your customer can still compute on it.
Studies stay on your iPhone or iPad, and a report leaves the device only when you share it.