To calculate the performance rate, the theoretical maximum speed is related to the actual speed.
|5.2||Time versus Quantity||
The maximum speed can be calculated in time or in number of product; i.e.
Nevertheless since OEE is primarily a shopfloor tool, and people on the shopfloor rather talk about ‘units being produced’ than ‘seconds it has taken to produce a unit’, it is preferred to register speed in units, not in time.
The parameters for Performance can be expressed in either TIME or QUANTITY, but QUANTITY is preferred
|5.3||Maximum speed of what?||
The maximum speed can be determined from the NPC, the Name Plate Capacity (Design speed). However, mostly there are several product(groups) on a machine with their own derived maximum speed. In such cases, special care has to be taken not to include hidden losses in the maximum speed due to ‘difficult products’ which might refer to ‘products which we don’t control the process for’
|5.4||Name Plate Capacity (NPC)||
The NPC should not be taken granted for. More than once it was discovered to include all kind of hidden losses. The manufacturer might have chosen a low NPC for reasons of liability or to ‘fit’ the equipment with other equipment in a line.
The standard is the theoretical maximum speed for a product(group) on the machine; thus the performance rate never exceeds 100%
The derivation of different maximum speeds for different products should be done in a mathematical manner.
The theoretical maximum speed for a product-machine combination is called ‘The Standard’. It is specifically not called Norm, since this word has negative associations related to piece work for many people in different countries.
At well chosen Standards, the performance rate will never exceed 100%, unless the product or the machine fundamentally changes
|5.6||How maximum is maximum speed?||
100% OEE = The theoretical maximum capacity of the equipment
This statement should be taken serious. If not done so, situations may (and do) occur where the shopfloor is filled with scrap, the machine is suffering one breakdown after the other and still accounts for 80% or more OEE. How?
70% Availability, 80 % Quality, 143% Performance = 80% OEE !
As soon as the performance rate goes over 100% (indicating the standard is chosen too low!) the beautiful balance of the OEE parameters is broken, and the focus may be taken away from what it is all about: identifying and reducing losses.
In cases where the maximum speed has to be determined based upon a Best Of Best analysis, it should be considered that this BOB is achieved under the former and current circumstances, including current losses.
A well chosen Standard will only change when the product or the machine fundamentally changes