3P in Lean: design the process before committing to the equipment
Learn the Production Preparation Process through a kit-packing design example. Compare concepts, prototype the work and check requirements before buying equipment.
The team has permission to design a new kit-packing area. Its first proposal copies the existing line and adds a conveyor.
Before discussing the conveyor price, it should ask whether the new area needs the same sequence of work.
3P means Production Preparation Process. It is a Lean approach to designing a product or process by developing and testing alternative ways to meet the requirement before committing to a design. The US EPA's explanation distinguishes that design work from improving a process whose basic arrangement is taken as given.
For this fictional team, that means trying different ways to prepare and check a kit before choosing equipment.
Start with the function the process must perform
The area must prepare the correct parts, verify kit contents, close the package and preserve a traceable record. Assume demand requires 60 kits per operating hour: one kit per minute of available time, before allowing for losses or other constraints.
That is a design requirement to test, not evidence that any proposed layout can achieve it. The takt-time guide explains how customer demand and available time establish the required pace.
Quality requires correct contents and identification. Safety requires an acceptable working method, access and handling. The design also needs maintainability, waste handling and a realistic energy and material requirement.
Writing those needs first lets the team question how each function is performed. It avoids turning “we need a conveyor” into the requirement itself.
Develop different process concepts
The team sketches three alternatives. A short workshop can use drawings, simple models and observation of how other mechanisms perform similar functions. A mock-up lets people test reach and sequence before a purchase makes changes expensive.
| Concept | How it would work | Question to test |
|---|---|---|
| Straight transfer line | Separate preparation, verification and closing stations, connected by a conveyor | Does transfer create waiting or make exceptions harder to recover? |
| Compact manual cell | Present parts near the operator and verify contents before closing | Can the required work fit the pace with acceptable reach and handling? |
| Prepared trays with assisted verification | Supply defined part positions and verify the tray before packing | Can wrong or incomplete trays be detected, and who replenishes them? |
The third option changes how the content check is designed. It is more than moving the same counting job to a different desk. It may reduce some counting work while adding tray preparation and controls upstream. Include that work in the comparison.
Prototype the difficult cases
Use representative kits, including the awkward combinations and exceptions. Check the work with the people who would do it, and involve the specialists responsible for safety, quality and maintenance.
Record the sequence, reaching and lifting, error detection, changeover, cleaning and recovery when a part is missing. Time the whole cycle repeatedly, rather than the fastest demonstration.
| Requirement | Evidence the design review needs |
|---|---|
| Correct kit | Tests of missing, wrong and extra parts, with a recorded response |
| Required pace | Complete cycles under representative conditions and realistic interruptions |
| Safe work | Qualified assessment of handling, access and equipment risks |
| Environmental performance | Material waste, energy and cleaning needs across the proposed process |
| Maintainable operation | Access, support needs, spares and recovery from faults |
The EPA cautions that a design can worsen environmental impacts when those risks are left outside the process. A smaller footprint does not automatically establish lower energy use or waste.
3P and Kaizen have different starting points
A Kaizen activity might improve the existing packing handoff or reduce repeated searching. A 3P study can question the product presentation, process sequence and equipment concept before the new area exists.
Both involve people testing changes. The difference is how much of the design is open: the 3P study can reconsider functions and equipment that an improvement to the existing line may have to retain.
The Kaizen, Lean and Six Sigma comparison explains their relationships. Value-stream mapping can reveal the wider route; mistake proofing helps examine how a design prevents or detects an error.
Select a concept, then define the delivery work
Compare the tested alternatives against the agreed requirements and whole-process costs. Document the conditions under which the preferred concept works and the questions still open. Do not assign a precise return on investment to a sketch.
If the compact cell meets the requirements, it can proceed into detailed design and an implementation plan. If it misses the pace or creates unsafe handling, revise or reject it. A cheaper layout is no bargain if the team cannot run it correctly.
The NPV and payback guide becomes useful once the alternatives have supportable costs, timing and benefits. The prototype results provide the cycle times, staffing assumptions and equipment requirements that estimate needs.
Sources and example notes
- US EPA: Lean thinking and methods, 3P, design alternatives, prototypes, review and environmental considerations, updated 25 November 2025.
The packing area, concepts and 60-kit hourly requirement are fictional. The sketches have no scale. No measured cycle time, staffing reduction or financial return is claimed.