The context
Connecting a tube to cleaning equipment looks like a minor task. Repeated throughout a production shift, it becomes a useful place to investigate lost capacity.
Atakan Gerger and Ali Rıza Firuzan documented an aerospace manufacturer’s alkaline tube-cleaning project in their published case study. The manufacturer was anonymized as XYZ Company. Backlogs and handling difficulties prompted a Black Belt-led improvement effort covering cleaning, rinsing and drying.
This analysis isolates the tube-connection task as a Green Belt-sized project. The proposed scope, statistical checks and control plan below are teaching extensions. They are not reported activities of a separate Green Belt team, and this was not a Lean Six Sigma International client project.
The problem
The study’s measurement work identified heavy adapters and a tube-to-adapter connection time of 26 seconds. Its analysis also described connection problems associated with the cleaning equipment.
The useful project question is specific: how much connection time could be removed while preserving secure attachment and acceptable cleaning? That framing gives the team a measurable response and a quality safeguard. It also creates a boundary around a task that operators, manufacturing engineering and quality can examine together.
How a Green Belt would scope it
A suitable charter would cover one cleaning cell and a defined tube family, starting when the operator picks up the adapter and ending when the connection is ready for loading. Cleaning chemistry, treatment duration and downstream acceptance requirements would remain unchanged.
I would plan this as a part-time assignment over roughly three months, with scheduled access to an operator, a tooling engineer and a quality representative. The Green Belt would coordinate observation, analysis and pilot evaluation. Engineering would retain responsibility for approving any adapter modification.
The primary measure would be connection time per tube. Companion measures would capture failed connections, reconnections and cleaning acceptance. These would make the pilot decision explicit: a faster method would proceed only with acceptable attachment and cleaning performance.
The tools applied phase by phase
Define: map the connection task
A detailed process map would separate adapter selection, positioning, fastening, checking and any repeated attempt. Walking and searching would appear as separate activities, even if they occurred between those steps.
That separation matters for this proposed project. An improved adapter might shorten fastening while leaving selection delays untouched. Recording the elements separately would let the team explain where the change acted and whether another task absorbed the time released.
Measure: establish a defensible baseline
The measurement sheet would include tube family, adapter size, operator, connection time and any failed attempt. Two observers would first time the same connections and reconcile disagreements about start and finish points. Otherwise, the team could mistake a change in timing practice for an improvement.
Observations would retain their production order. An individuals and moving-range chart would be a candidate for examining stability when observations are individual measurements, following the structure described in NIST’s control-chart guidance. The team would review the sampling arrangement before pooling different operating conditions.
Capability analysis would need an agreed operational upper limit for connection time, derived from the cell’s capacity requirement. NIST defines capability through comparison of a stable process with specification limits. Without that limit, this project could report timing performance but could not defensibly claim a capability index.
A conventional normal-distribution capability calculation would also require checking the distribution and having sufficient independent observations, as NIST explains. For this proposed one-sided requirement, the analysis would use the upper capability index only if those conditions were defensible. No capability value can be reconstructed from the published connection-time figures alone.
Analyze: connect the delay to a mechanism
The authors attributed difficulty with the existing screwed connections to thermal expansion of the threads and introduced a cam-based connection design, according to the improvement section.
For the scoped project, a cause-and-effect discussion would turn that explanation into observable questions. Does the delay occur during fastening? Does it change with adapter condition or operating temperature? Are repeated attempts concentrated in particular sizes? Direct observation would help distinguish competing explanations before a pilot was authorized.
Statistical validation would compare connection times under the existing and proposed methods. A two-sample t-test could assess a difference in means for independent samples; genuinely matched observations would call for a paired analysis, consistent with NIST’s guidance on test selection. The analysis plan would specify the comparison before collecting pilot data.
Improve: pilot the approved method
The pilot would cover representative operators and adapter sizes, with an agreed sequence that limits learning and production-mix effects. Its record would include unsuccessful attempts and quality checks alongside elapsed time.
A confidence interval for the mean difference would help the sponsor judge the likely operational benefit. The team would also examine the slowest recurring situations. A method that performs well only with one experienced operator would need further development before handover.
Control: make the response practical
After an accepted pilot, the team would establish a stable post-change baseline. An individuals chart would track elapsed times, with the moving-range chart tracking successive differences, using the NIST chart structure.
| Control item | Owner | Response |
|---|---|---|
| Connection-time signal | Cell lead | Investigate adapter, tube family and work method. |
| Failed attachment | Operator and quality | Hold affected work and follow approved disposition. |
| Adapter condition | Tooling technician | Remove suspect tooling for assessment. |
| Method revision | Manufacturing engineering | Approve changes and update operator instructions. |
The documented result
The authors reported connection time falling from 26 seconds to 3 seconds with the new design. That result belongs to their broader project. It does not establish the outcome of the proposed Green Belt validation described here.
What a trainee should take from it
The demanding judgment in this assignment would be deciding what evidence justifies handover. Your project file would need a reproducible timing definition, an approved tooling change, a comparison that accounts for operating conditions, and a named response owner. At the final review, the cell lead should be able to explain what happens when a connection becomes slow again or fails its check.
