Standard work combination sheet: how to create one
In one sentence
A standard work combination sheet places human work, automatic processing, walking and waiting on one timeline; the cycle is read from the interval between recurrences of the same state.
By the end of this lesson
- Place human work, automatic processing and walking in separate rows according to their resources.
- Calculate the overlap of 25 s of human work, 50 s of automatic time and 5 s of walking, showing intermediate results.
- Close the cycle by checking the worker's return and machine readiness together.
- Reject a proposed overlap that supervision or precedence conditions make infeasible.
Why it matters
If K01 can prepare the next part while an automatic process runs, the two tasks share the same seconds. Blindly adding human work time and machine time overstates elapsed time. Conversely, choosing only the longest duration is not always correct; loading may be required before automatic processing can start. A standard work combination sheet prevents both errors by showing when tasks start and end. The decisive factor is where the rows sit in time, rather than each row's duration. Human workload, machine workload and cycle time answer different questions. The same data can explain all of them; however, they are not all found by the same addition.
Automatic time is only the portion the machine performs without the worker's continuous involvement. If K01 holds the part, watches for hazards or continuously monitors the result while the machine runs, this time cannot be freely assigned to other work. Verify the conditions for safely leaving the machine first. The sheet does not physically create these conditions; it makes the overlap permitted by the current method visible. Two manual tasks or walking intervals for the same person cannot overlap in the human lane. In the machine lane, automatic processing cannot start before loading ends. Work performed away from the machine can overlap with it, but walking also uses the worker's time. Forgetting the return route makes an infeasible assignment look suitable.
The cycle boundary does not have to be defined only by pressing a button. It can run from the start of loading to the next start of loading; what matters is returning to the same work state at both boundaries. If the worker returns before the machine finishes, there is waiting. If the machine has finished but the next part is not ready, the cycle still cannot start. Readiness conditions must therefore be examined together. Also state which cycle will use the part prepared in a cycle. A steady-production sheet must not hide initial preparation; define preparation of the first part as a separate startup task. Steady repetition and initial production startup are different time windows and are not added together without explanation.
A combination sheet must not become a race to fill gaps. Waiting may arise from the inherent relationship between automatic time and human work. If adding a task delays quality inspection or disrupts a safe return, empty space on the sheet is not sufficient justification. The takt line shows the demand interval; it does not show that every apparently free second can be used safely. Examine the necessity, sequence and safe feasibility of the work first. Then measure the alternatives under the same starting conditions. Report reduced human workload, reduced cycle time and increased output as separate results. This distinction also explains why a more orderly sheet does not always produce a shorter cycle; the machine may still set the limit.
Formula
Human workload (s/cycle) = Union of manual work, walking and required supervision intervals (overlapping involvement counted once)
Union of two time intervals (s) = First duration + Second duration − Overlapping duration
Cycle time (s/cycle) = Next identical start time − Previous start time
Operator waiting (s/cycle) = Cycle time − Human workload
Time remaining to takt (s/unit) = Takt − Cycle time producing one unit
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- Step-by-step instructions
- Worked example with real numbers
- Where the method misleads
- Common mistakes