Definition
The Process Capacity Sheet (工程別能力表, kōtei-betsu nōryoku hyō) is a calculation form that determines the production capacity of each individual process or machine in a production line. For each process, it records the manual work time, machine automatic cycle time, and any tool change time allowances, then calculates the maximum number of parts that process can produce in a given period. By listing every process on one sheet, it reveals which process is the bottleneck — the constraint that limits the capacity of the entire line.
This is the first document created when establishing standardized work. Before you can design an operator’s work cycle (Combination Table) or draw the floor layout (Standardized Work Chart), you must know what each machine is capable of and where the constraint is.
Japanese Origin
工程 (kōtei) means “process” or “manufacturing step.” 別 (betsu) means “by” or “according to” — it indicates a breakdown by category. 能力 (nōryoku) means “capacity” or “capability.” 表 (hyō) means “table” or “chart.” Together: “capacity table by process” — a table that shows the capacity of each process individually.
History at Toyota
The Process Capacity Sheet is rooted in the same era as the other standardized work documents — Toyota’s transformation from batch production with isolated machines to connected multi-machine cells in the 1950s and 1960s.
When Ohno began combining manual machine tools into cells, the first practical question was capacity: can this set of machines, arranged in this configuration, produce enough parts to meet customer demand? Each machine had different cycle times, different tool change frequencies, and different manual handling requirements. The Process Capacity Sheet was the tool that answered this question systematically — machine by machine, process by process.
The sheet is deliberately simple in its math. For each process, it calculates: given the available production time per shift, how many parts can this machine produce after accounting for manual handling time, machine cycle time, and periodic tool changes? The process with the lowest number is the bottleneck. If the bottleneck capacity falls below the required production quantity (derived from takt time), the line cannot meet demand without improvement — either reducing the bottleneck’s cycle time, reducing tool change time, or adding capacity.
How It Works
Data Collected Per Process
For each machine or process in the line, the sheet records:
- Process number and name — the sequential position in the production flow and the operation performed (e.g., “Process 3: Drilling”)
- Machine number — the specific machine used
- Manual time (手作業時間) — the time the operator spends on hands-on work at this machine per cycle: loading the part, clamping, starting the machine, unclamping, unloading, inspecting. Measured by stopwatch observation.
- Machine automatic time (自動送り時間) — the time the machine runs its cycle unattended after the operator starts it. Taken from machine specifications or measured directly.
- Completion time per piece — manual time plus machine automatic time for one complete cycle at this process
- Tool change time and frequency — how long a tool change takes and how often it occurs (e.g., every 500 pieces). This is converted to a per-piece time allowance and added to the completion time.
- Capacity per shift — available production time per shift divided by the adjusted completion time per piece. This is the maximum output of this process.
Identifying the Bottleneck
With all processes listed on one sheet, the bottleneck is immediately visible: it is the process with the lowest capacity per shift. This number determines the maximum output of the entire line — no downstream process can produce more than what the bottleneck feeds it.
The sheet also shows takt-based required output for comparison. If the bottleneck capacity is below the required output, the gap must be closed before standardized work can be established. Common countermeasures include reducing machine cycle time, improving tool change speed (SMED), reducing manual handling time through better fixturing, or separating the bottleneck operation into parallel machines.
Why Tool Change Time Matters
Tool change time is explicitly included because it can be a significant hidden capacity loss, especially in machining operations. A tool change that takes 5 minutes every 200 parts adds 1.5 seconds per piece — which may not sound like much, but in a 60-second takt time operation, that is 2.5% of capacity. Multiple processes each losing a few percent to tool changes can add up to a meaningful gap between theoretical capacity and actual throughput.
Including tool change allowances in the capacity calculation ensures that the bottleneck identification reflects real operating conditions, not ideal conditions that assume tools never need changing.
How It Relates to the Other Standardized Work Documents
The Process Capacity Sheet is the first of three core standardized work documents:
- Process Capacity Sheet — calculated first to determine each machine’s capacity and find the bottleneck
- Standardized Work Combination Table — created second, using the time data from the capacity sheet to design the operator’s cycle
- Standardized Work Chart — created last as the visual summary
The sequence is important. The capacity sheet answers the question “Can this line meet demand?” The Combination Table answers “How does the operator run it?” The Standardized Work Chart answers “What does it look like on the floor?” You cannot answer the second question without the first, or the third without the second.
Common Mistakes
Skipping the capacity sheet and going straight to the Combination Table. Without knowing each machine’s capacity and where the bottleneck is, you risk designing an operator cycle for a line that cannot meet demand. The capacity sheet is the reality check that must come first.
Omitting tool change time. Capacity calculations that ignore tool changes overstate what the line can actually produce. The gap between calculated capacity and actual output is often traceable to tool change allowances that were never accounted for.
Calculating capacity under ideal conditions. The capacity sheet must reflect actual operating conditions — measured manual times from real operators, actual machine cycle times (which may differ from nameplate specs due to wear or settings), and real tool change frequencies. Using engineering estimates instead of observed data produces a sheet that describes the intended process, not the actual one.
Confusing the capacity sheet with line balancing. The Process Capacity Sheet determines the capacity of each process and identifies the bottleneck. It does not balance work across operators — that is the function of the Combination Table. The capacity sheet tells you what the machines can do; the Combination Table tells you what the operators should do.
Treating it as a one-time calculation. Capacity changes when machine conditions change, when tool life changes, when product specifications change, or when improvements are made. The sheet must be recalculated whenever conditions change — it is a living document that reflects the current state of the line.