Time Study and the Process Capacity Sheet
A Process Capacity Sheet is only as good as the observation behind it. Time study is not clerical data collection — it is how you understand the current method and what each process can actually produce.
Standardized work is built from observation, not from memory or office estimates. This section covers the groundwork that comes before the forms — breaking a job into work elements, defining measuring points, and timing the work — and then the first of the three major forms: the Process Capacity Sheet.
1Time reflects method
The time required to do a job is not fixed. It changes with the method, layout, tools, preparation, sequence, and skill. Before you can improve work, you have to understand the current method accurately — and time is how the method becomes visible.
The purpose is not to pressure people to work faster. It is to see the work clearly enough to remove waste, imbalance, and unnecessary difficulty.
Do not fill out a Process Capacity Sheet from memory. Use actual parts, actual equipment, actual work, and actual observation at the worksite.
2Work elements and measuring points
A job must be broken into work elements before it can be timed well. A useful element is large enough to teach and observe, but small enough to understand and improve. Then, for each element, define a measuring point — a visible or audible moment where the element starts and ends. If observers use different measuring points, the data will not be reliable.
Very short motions are hard to time cleanly. In practice a brief element is combined with the longer one next to it — picking up a tool, for instance, folds into the element where the tool is used — so each measured element is long enough to read reliably.
| # | Work element | Starts when… | Ends when… |
|---|---|---|---|
| 1 | Pick up part | hand touches part | part lifts from bin |
| 2 | Set part in fixture | part lifts from bin | part seated in fixture |
| 3 | Start machine | part seated | cycle-start button pressed |
| 4 | Remove finished part | machine cycle ends | part clears the fixture |
| 5 | Place part in tray | part clears fixture | part released in tray |
Each element has a clear start and end tied to something observable — a hand touching a part, a button pressed, a part leaving a fixture.
What to notice: the measuring point is what makes timing repeatable. Two observers timing the same job should get nearly the same numbers.
3Continuous timing
Toyota-style time observation usually uses a continuous stopwatch method. The watch runs without stopping, and the observer records the elapsed (cumulative) reading at each measuring point. Each element's time is then calculated by subtraction. This avoids the errors that come from repeatedly starting and stopping the watch.
Time several cycles, not one. A single pass can be unrepresentative — a fumble, a hesitation, or an unusually clean run. Recording several cycles and reconciling them gives a time you can trust as the basis for every form that follows.
The watch never stops. Readings are cumulative; each element time is the gap between one reading and the next.
What to notice: recording cumulative times and subtracting afterward is more accurate than starting and stopping the watch for every element.
4The Process Capacity Sheet
The Process Capacity Sheet shows the production capacity of each process involved in making a part. For every step it captures the process and machine, the manual and automatic times, the total cycle time, how often tools are changed and how long that takes, and the resulting capacity per shift. It is the form that exposes the least-capable process in a line, and it feeds the Standardized Work Combination Table that comes next.
The three time columns are not interchangeable. Manual time is what the operator does by hand — loading, unloading, tightening, setting a part. Automatic time runs from the moment the machine begins its cycle, through processing, until it returns to its home position and stops. Total cycle time is normally the two added together. These are measured at the worksite with actual parts, not estimated — the basic time is the foundation every other standardized-work form is built on.
| Step # | Process Name | Machine Number | Manual Time | Auto Time | Total CT | # Pcs. / Change | Time to Change | Time Per Pc. | Shift Capacity |
|---|---|---|---|---|---|---|---|---|---|
One row per process step. Total cycle time and shift capacity are calculated, not estimated.
| Step # | Process Name | Machine Number | Manual Time | Auto Time | Total CT | # Pcs. / Change | Time to Change | Time Per Pc. | Shift Capacity |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Gear Cut | GC614 | 5″ | 38″ | 43″ | 300 | 120″ | 0.4″ | 635 |
| 2 | Chamfer | CH228 | 6″ | 7″ | 13″ | 300 | 120″ | 0.4″ | 2059 |
| 3 | Gear Cut | GC1444 | 6″ | 38″ | 44″ | 300 | 120″ | 0.4″ | 621 |
| 4 | Gear Cut | GC1445 | 6″ | 30″ | 36″ | 300 | 120″ | 0.4″ | 758 |
| 5 | Test | TS1110 | 7″ | 3″ | 10″ | 300 | 120″ | 0.4″ | 2653 |
Capacity constraint of the line — the least-capable process sets the line's pace.
Five machining steps. Step 3 (Gear Cut, GC1444) has the lowest shift capacity at 621 pieces, so it constrains the whole line.
What to notice: capacity is driven by total cycle time and tool-change frequency, not manual time alone. Steps 1 and 3 both run a 38″ auto cut, but small differences compound into the binding constraint.
5Reading capacity and the constraint
The capacity of each step follows from its cycle time and how tool changes are spread across the pieces produced:
Shift capacity = available shift time ÷ (total cycle time + tool-change time per piece)
- Total CT = Manual Time + Auto Time for the step.
- Time Per Pc. spreads each tool change across the pieces it produces:
Time to Change ÷ # Pcs. per Change. - Shift Capacity = available shift time ÷ (Total CT + Time Per Pc.).
- The lowest Shift Capacity across all steps is the line's capacity constraint.
The slowest machine is not automatically a bottleneck. A process is a constraint only when its capacity falls below the production actually required. If demand is well under 621 pieces a shift, Step 3 limits the line but does not yet hurt you.
6When to use it
The Process Capacity Sheet earns its place when equipment or machine processing capacity matters — multiple machines, meaningful automatic time, and tool changes. For purely manual work, where no machine sets the limit, it is usually not the right form; the analysis moves straight to combining human work against takt time, which is the subject of the next section.
And record only the work that bears on machine capacity. Simple material handling — taking a part off a pallet by hand, setting a finished part down — does not belong in the time columns. The sheet measures what the equipment can process, so manual handling that does not gate the machine is left out.
Section summary
Time study is how the current method becomes visible. Break the job into work elements, fix a clear measuring point for each, and time continuously — recording cumulative readings and subtracting to get element times.
The Process Capacity Sheet turns that observation into the capacity of each process and exposes the least-capable step. That step constrains the line only when its capacity falls below required production. The sheet then feeds the Standardized Work Combination Table.