Less Waste = More Lean
Over production: producing more material than is needed before it is needed is the fundamental waste in lean manufacturing; material stops flowing.
Producing defective products: defective products impede flow and lead to wasteful handling, time and effort.
Inventories: material sits taking up space, costing money and potentially being damaged. Problems are not visible.
Motion: any motion that does not add value to the product is waste.
Processing: extra processing not essential to value-added from the customer point of view is waste.
Transportation: moving material does not enhance the value of the product to the customer.
Waiting: material waiting is not material flowing through value-added operations.
Source: Optiprise Inc.