Early production of products is also considered as "Excess finished goods inventory" in lean wastes. If early production is considered in both types of wastes such as 'overproduction' and 'Inventory', there will be the chance of recurrence of same waste in different categories. How to avoid this duplication?
I feel like SWIMTOOT or USWIMTOO is just a way of identifying waste. Whether the waste is identified as excess inventory or over production is negligible as you have identified the waste anyway. Which ever you pick you want to set that as a standard is your company so people are identifying it as the other type of waste.
Personally anything that is planned production i.e. if you plan early production of products, you've planned to make these so I wouldn't class them as over production.
If I think of castings. The first few off Aluminium Die Cast parts are usually scrap. This is because your trying to get the die up to temperature. The parts are unusable so they cant be classed as inventory. You've planned to manufacture them as part of running the machine in, so you cant class it as over production as you haven't created excess parts, they are un-useable so are scrap.
Martin McKie In case of Aluminum die cast, first few parts will be considered in "Defect" category. Those unuseable parts will neither be considered in "Overproduction" nor in "Inventory".
Muhammad Huzaifa Raza agreed. Within the SWIMTOOT model a defect if unreworkable would be considered scrap, as in the casting example. I suppose if they could be re-worked back to a saleable standard they would be considered within SWIMTOOT as Over Processing.