Lean manufacturing is an engineering approach for designing production systems that deliver customer value with the least waste. It matters because waste consumes time, labor, floor space, energy, and money without improving the product. A lean factory aims to make problems visible so teams can remove root causes rather than work around them.
The 8 wastes are often remembered with the acronym DOWNTIME.
Key Facts
- DOWNTIME = Defects, Overproduction, Waiting, Non-utilized talent, Transportation, Inventory, Motion, Extra-processing.
- Value-added work changes the product in a way the customer is willing to pay for.
- Non-value-added work uses resources but does not increase customer value, such as searching, rework, or unnecessary movement.
- Value-added ratio = value-added time / total lead time.
- Cycle time = production time available / customer demand.
- 5S = Sort, Set in order, Shine, Standardize, Sustain.
Vocabulary
- Lean manufacturing
- Lean manufacturing is a system for improving flow and reducing waste while delivering what the customer values.
- Waste
- Waste is any activity, material, delay, or movement that uses resources without adding customer value.
- Continuous flow
- Continuous flow is the movement of work through process steps with minimal waiting, batching, or interruption.
- Kaizen
- Kaizen means continuous improvement through small, practical changes made by the people who do the work.
- 5S
- 5S is a workplace organization method that makes tools, materials, and problems easy to see and manage.
Common Mistakes to Avoid
- Treating lean as only cost cutting is wrong because lean focuses on increasing customer value while removing waste from the process.
- Counting busy motion as productive work is wrong because walking, reaching, searching, and rearranging do not necessarily transform the product.
- Producing extra parts just to keep machines running is wrong because overproduction creates inventory, hides defects, and increases lead time.
- Skipping worker input during improvement projects is wrong because operators often know the real causes of delays, defects, and awkward motion.
Practice Questions
- 1 A product spends 12 minutes being machined, 3 minutes being inspected, and 45 minutes waiting between stations. If only machining is value-added, what is the value-added ratio?
- 2 A factory has 420 minutes of production time per shift and customer demand is 140 units per shift. What cycle time is needed to meet demand?
- 3 A team moves tools closer to the workstation, labels storage locations, and removes unused fixtures. Explain which lean idea this supports and which wastes it can reduce.