Reading a Production Line Chart to Find the Bottleneck
A plant runs three workstations in series: Cutting, Assembly, and Packing. A bar chart shows each station's capacity in units per hour: Cutting = 120, Assembly = 95, Packing = 110. The chart has no labels for units and the vertical axis starts at 80 rather than 0, so the bars look much more different than they really are. Last week the line produced 4,200 units over 50 scheduled hours. The supervisor wants to raise output to 5,000 units per week without adding a workstation, and asks whether the truncated axis is hiding anything important about where to focus.
1. What is the true limiting throughput of the line, and how does the truncated axis distort the picture?
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The line moves in series, so throughput is set by the slowest station: Assembly at 95 units/hour. The truncated axis (starting at 80) exaggerates the visual gap between bars. In true proportion, Cutting is 120/95 ≈ 1.26× Assembly, not the dramatic difference the chart implies. The ordering is still correct, but a reader who trusts bar height would badly overestimate how much faster Cutting is.
2. Can the line reach 5,000 units/week at 50 hours? Where should effort go?
Read the worked answer
Required rate = 5,000 / 50 = 100 units/hour. Current bottleneck is 95/hr, so the line cannot reach the target as-is. Last week's 4,200/50 = 84/hr was below even the bottleneck, suggesting downtime or starvation, not a capacity ceiling. Effort should go first to Assembly (raise 95 → 100+, e.g., reduce changeover or add a short shift) and to recovering the lost 11 units/hr of actual-vs-capacity gap.