Chocolate A — parallel assembly flow
2 parallel manufacturing lines (Roasting → Grinding → Molding) converging on a single packaging station.
8:00 AM
0.0 min of a 8-hour shift
Problem statementExample 1
A chocolate maker runs identical manufacturing lines. Each line performs Roasting & Winnowing, then Grinding, then Blending & Molding. Every line feeds the same single packaging station, which is the only exit from the plant.
Given
- ·X Roasting & Winnowing: 15 units/hr per line
- ·Y Grinding: 20 units/hr per line
- ·Z Blending & Molding: 15 units/hr per line
- ·Packaging: 24 units/hr, shared by all lines
- ·Two parallel manufacturing lines, 8-hour day
- ·Maximum daily demand 200 units; contribution margin $1.25/unit
Find
- What is the cycle time for a single unit through the flow?
- How many units are completed in an 8-hour day?
- Which resource is the bottleneck, and what is the steady-state rate?
- Why is the early part of the day slower than the steady state?
0%
Process map — Chocolate A
2 parallel manufacturing lines (X → Y → Z) converging into one packaging station.
Manufacturing 30/hr → Packaging 24/hr
Line 1· 15/hr
XRoasting & Winnowing
15 /hr
YGrinding
20 /hr
ZBlending & Molding
15 /hr
1
→
Line 2· 15/hr
XRoasting & Winnowing
15 /hr
YGrinding
20 /hr
ZBlending & Molding
15 /hr
2
→
all lines converge ↓ (0 waiting)
Packaging queue
PPackaging
24 /hr
Completed
0
last: —
Live readout
Completed units
0
of 200 demand
Recent throughput
0.0
units/hr, trailing 60 min
Average throughput
0.0
units/hr since opening
Total WIP
2
units inside the system
Cycle time (last unit)
—
fastest possible 13.5 min
Bottleneck
Packaging
system capacity 24/hr
WIP by stage
2
X
0
Y
0
Z
0
P-queue
0
Packing
Utilization
X · Roasting & Winnowing
0%
Y · Grinding
0%
Z · Blending & Molding
0%
Packaging
0%
Capacity arithmetic
| Per-line capacity (min of X, Y, Z) | 15 /hr |
| Manufacturing (2 lines) | 30 /hr |
| Packaging | 24 /hr |
| System capacity | 24 /hr |
| Demand rate | 25.0 /hr |
| Theoretical output in 8h | 192 units |
| Contribution at $1.25/unit | $240.00 |
Effective output is limited by the smallest of manufacturing capacity, packaging capacity and demand.
Scenario parameters
Changing a parameter rebuilds and restarts the simulation.
What are we learning?
- Cycle time — how long one individual unit takes to pass through the whole flow (13.5 min in an empty system, longer once queues form).
- Throughput — how many units leave the system over the 8-hour schedule. It is set by capacity, not by cycle time.
- Steady state — after the pipeline fills, the output rate settles at the bottleneck rate (24/hr). Before that, output is in a transient ramp-up.
Instructor view — what to point out
- Parallel capacity: adding a line multiplies manufacturing capacity, not line speed.
- Synchronization: both lines converge on one packaging server — arrivals interleave.
- Bottleneck: queue growth in front of packaging is the visual signature.
- Cycle time ≠ throughput: the first unit is fast; the 100th waits in queue.
- Transient vs steady state: watch the recent-throughput number settle.
- Demand constraint: capacity above demand simply produces idle time.
Try this
- · Drop to 1 manufacturing line — who becomes the bottleneck?
- · Raise packaging to 30/hr — does output rise to 30?
- · Raise demand to 300 — does output change, and why not?
- · Set Y (Grinding) to 12/hr — the bottleneck moves inside the line.
- · Add a 3rd line and watch the packaging queue explode.
Event log
- 8:00 AMUnit #2 (line 2) entered X
- 8:00 AMUnit #1 (line 1) entered X