Reading a Production Line Chart for a Bottleneck
A packaging line has four stations in series. A posted throughput chart (units per hour, by station) shows: Filler 480, Capper 420, Labeler 600, Case Packer 500. A second chart shows downtime minutes per 8-hour shift: Filler 20, Capper 55, Labeler 10, Case Packer 25. The line's target is 400 finished units per hour. A supervisor proposes buying a second capper to raise its rated speed to 840 units/hr. The capper's downtime is caused by jams that occur when upstream units arrive faster than it can seat caps.
1. Identify the bottleneck and explain whether the capper's rated speed is the real limit.
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The capper is the bottleneck: lowest rated throughput (420) and highest downtime (55 min/shift). But note the capper's downtime is caused by upstream overfeed - jams happen when units arrive faster than it can seat caps. So the capper's effective rate is even lower than 420, and adding a second capper addresses capacity but not the jam cause unless feed is regulated.
Effective hourly rate ≈ rated × (available minutes / total minutes). For the capper: 420 × (480−55)/480 ≈ 420 × 0.885 ≈ 372 units/hr - already below the 400 target. That's the real limit, and it's a combination of rated speed and jam-driven downtime, not rated speed alone.
2. The supervisor wants to buy a second capper. Evaluate that proposal against a cheaper alternative and recommend.
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A second capper raises rated speed to 840, but the jam cause (overfeed) remains, and the line is still gated by the case packer at 500 and the filler at 480 once the capper is fixed. Spending capital to lift the capper far above 500 yields little because the next station caps the line.
Better first move: regulate feed into the capper (buffer/accumulation table or rate-limit upstream) to cut the 55 min of jam downtime. If downtime drops to ~25 min like the packer, capper effective ≈ 420 × (455/480) ≈ 398 units/hr - roughly at target, at far lower cost. Then reassess whether the case packer (500 rated, 25 min downtime → ~474 effective) or filler becomes the next constraint. Recommend the low-cost feed fix first; revisit the second capper only if demand exceeds ~474 after that.