Reducing or eliminating waste is one of the major principles of lean manufacturing, practiced by Solar Innovations, Inc.. Waste is often considered synonymous with trash; however, in lean manufacturing, it is categorized into seven areas:
Transportation: Though required and nearly impossible to eliminate, the movement of products between manufacturing functions can often be reduced by re-organizing the process flow.Inventory: Attempting to run large batches, as is the case with traditional manufacturing, requires stocking vast inventories for both raw materials and work in progress (WIP).Motion: Any unnecessary movement, whether lifting, walking, or transferring components should be reduced or eliminated whenever possible.Waiting: Any idle time for either employees or equipment, caused by a host of problems, is considered waste and should be eliminated.Overproduction: Completing finished products before the order has been placed or producing more than will be ordered leads to significant waste in a number of areas.Over-Processing: Completing extra, unnecessary work that adds no value to the final product.Defects: Any defect that leads to rework, waste, delivery delays, excess paperwork, and time for investigations.There are two useful mnemonics to help you remember these ideas: TIM WOOD and WORM PIT:| T | – Transport | W | – Waiting | |
| I | – Inventory | O | – Overproduction | |
| M | – Motion | R | – Rejects | |
| W | – Waiting | M | – Motion | |
| O | – Overproduction | P | – Processing | |
| O | – Over-processing | I | – Inventory | |
| D | – Defects | T | – Transport |