An OEM charger programme has three workstreams — mechanical, certification and packaging — and they interfere with each other if they run in parallel without the right hand-offs. The sequence below is the one that minimises waiting.
Step 1: mechanical design freeze
Before anything else, the housing, port layout and plug mechanism are fixed. Certification needs the final configuration, and packaging needs the final dimensions. Starting either before the freeze guarantees rework.
Step 2: tooling and engineering samples
Trial shots, corrections, then a sample of the production configuration. Certification cannot start on a unit built with a temporary tool, so this is the gate that everything else waits on.
Step 3: certification in parallel with packaging artwork
Once the mechanical configuration is fixed, the lab can start and the packaging artwork can start on the same day. These two genuinely run in parallel: the lab tests the product, the designer draws the carton. Two weeks are saved here on almost every programme.
Step 4: packaging proof and branded sample
The carton proof is approved on production board stock, and the branded sample is approved with the packaging in place. Approve them together, not separately — the accessory set and manual are part of the product.
Step 5: pilot run, then bulk
The pilot run is the last gate: production components, production tooling, the test report that the bulk run will be compared against.
Where the schedule usually breaks
Two places. Artwork starting before the tooling is frozen, which produces a carton that does not fit the product; and certification starting on an engineering sample, which produces a report that has to be repeated. Both are avoidable, and both cost weeks rather than days.
What to put in the project plan
Five dated milestones: design freeze, T1, pilot sample approved, lab reports issued, packaging proof approved. Everything else is a task; those five are decisions.