How to calculate the effective time waste rate?

1) waste degree = MLT/VT. We can use the ratio of manufacturing cycle time (MLT) to value-added operation time (VT) to evaluate the degree of waste in the manufacturing process. The greater the proportion, the greater the waste. Because the value-added operation time is a standard value under certain conditions and periods, we can only eliminate waste by shortening circular-flow time continuously, which is the core of Toyota lean production.

2) Productivity: We can evaluate the productivity of an enterprise by the ratio of the working hours of value-added activities attached to products to the total working hours put into production: productivity = (output × product value-added working hours)/total working hours put into production.

3) Comprehensive Equipment Efficiency (OEE): We use the ratio of standard equipment time attached to qualified products to total equipment time put into production to evaluate the comprehensive equipment efficiency (OEE) of an enterprise: OEE = (number of qualified products ×σMCT)/ total equipment time put into production, where σ MCT is the sum of MCT of all processes for producing a product. When evaluating the OEE of a product line, only the MCT of the finished product is included, while the semi-finished product consumes equipment man-hours, but it is not an effective output. Therefore, reducing the production of WIP is beneficial to the improvement of OEE.

Classification of time:

1) Tark time) = rated running time/saleable quantity: takt time (TT) is equal to rated running time divided by saleable quantity. Among them, the rated working time of a day is the normal working time of a day, excluding overtime minus rest time.

2) Lead time: Lead time (LT) is the time from receiving the customer's order to delivering the goods that the customer wants, that is, lead time (LT)= processing time of order information+manufacturing process cycle time (MLT)+ goods transportation time.

3) Value-added time: To produce a unit product, the raw materials of the product need to be processed or assembled, inspected, transported and stored, and those operations that change the state or characteristics of the manufactured object are value-added operations.