Figures for measuring lean manufacturing

More and more enterprises count on lean processes and lean manufacturing. “[Lean] is a production practice that considers the expenditure of resources for any goal other than the creation of value for the end customer to be wasteful, and thus a target for elimination. Working from the perspective of the customer who consumes a product or service, “value” is defined as any action or process that a customer would be willing to pay for.” (Wikipedia: Lean manufacturing,
Lean manufacturing distinguishes by producing efficiently and effectively. There are some figures for measuring lean manufacturing. In the following I’ll concentrate on three numbers.

The first figure is the First-Time-Through capability FTT. This measures the percentage of the good units that go through the production process without being scrapped, reworked, rested, returned by the downstream operation, or diverted into an off-line repair area. FTT is the leading indicator of quality. The percentage of defects is calculated for each process. The target value of FTT is 100%, so there would be no poor units at all.
FTT=( Ninput- (Nscrapped+Nreworked+Nretested+Nrepaired) ) / Ninput * 100

Overall Equipment Efficiency OEE is used to determine the productivity at the equipment level function of a number of mutually exclusive components like availability, efficiency, performance and quality efficiency in order to quantify various types of productivity looses. Productivity looses are for example breakdowns, set-ups or adjustments. The OEE helps to identify the efficiency, to see to what extent specific equipment is used for the production of a concrete product type or group. The OEE should be high as possible.
OEE = (Tpt /Tst) * (Tc* Nfu)/ Tpt* (Nfu– Nd)/Nfu* 100

The Dock-to-Dock Time DTD is the time for turning raw materials into finished products. Improving the DTD time improves the company’s ability to deliver on-time and lowers the cost for warehousing as well as for material handling.
DTD= Tmi+ Tmct+ Tfi


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