What is the bottleneck in a packaging line?
The bottleneck is the process step or recurring condition that limits sustained acceptable output over the relevant production period. It can be a machine cycle, a manual task, product supply, pack transfer, inspection, changeover, refill, cleaning or repeated short stops rather than the machine with the lowest brochure speed.
Identify the constraint by measuring good output and state time during the actual product and format mix. A bottleneck can move when a format, operator, product or downstream requirement changes.
Why do individual machine speeds fail to predict line output?
Individual speeds usually describe a machine under defined conditions, while line output includes transfer, spacing, rejects, refills, stops, recovery, inspection, manual loading and interaction between machines. A line with nominally faster components can deliver less good product if those components repeatedly block or starve one another.
Specify sustained good output over an agreed run, not the fastest observed instantaneous rate. Record the accepted product and pack criteria used to count good output.
When does accumulation improve a packaging line?
Accumulation helps when one part of the line needs to continue through short downstream stops, controlled process variation or brief manual interventions. It provides time or pack capacity between machines, but only if the packs can accumulate without tipping, scuffing, locking together, losing orientation or affecting product quality.
Define the disturbance duration to absorb, the pack rate, the usable accumulation density, discharge behaviour and the control states. Physical conveyor length alone does not equal useful accumulation.
When will more conveyor accumulation not solve the problem?
More accumulation will not solve a permanent capacity shortfall, frequent long faults, poor pack quality, an undersized operator task, inadequate product supply or a machine that cannot restart reliably. It may merely delay the same stoppage and increase work-in-progress, recovery time or damage risk.
Correct the root cause where the loss is structural. Use accumulation only where the control objective and maximum expected disturbance are defined.
How should blocked and starved states be controlled?
Each machine should have agreed signals and timing for downstream blocked, upstream starved, permissive-to-run, fault, emergency stop and restart. The sequence should prevent uncontrolled pack build-up, dry running, empty cycles, mixed product and unsafe automatic recovery.
Define which machine owns line speed, how speed reference is shared, where packs are detected, and what happens after a reject or manual removal. Test repeated stops and recovery rather than only steady running.
What data should be collected before changing the line?
Collect time-stamped good output, machine states, stop reason, duration, product and format, operator intervention, refill and changeover data. Add a simple line observation showing where packs queue, where machines wait and whether the constraint changes over the shift.
A short video of representative stops can help identify transfer and recovery problems. Protect confidential data and follow site safety rules when observing or recording machinery.
