How to define Maximum Speed: NPC and ‘Standard’
Defining the NPC
The Name Plate Capacity is the maximum production speed of the machine for which it has been designed. Use the following ways to determine the NPC:
- Ask the manufacturer of the machine for the NPC; keep on asking questions: Is this really the theoretical maximum or are all sorts of restrictions already included in this value?
- If the NPC is not available or not known, let the machine operate at maximum speed (‘turn all switches to the right’) for a number of cycles and without interruption, and measure the cycle time with a stopwatch. Subsequently, calculate the number of units per minute the machine can produce at that speed. If needed, do this with an empty machine.
- In some instances, it is possible to (have) calculate(d) the theoretical maximum speed; for example, chemical processes, curing times, heat transmissions, etc.
OEE Coach does not allow to set a higher speed than the NPC: So NPC is the highest possible speed for any product on this machine
Defining the ‘Standard’
The Standard is the theoretical maximum production speed for a specific product-machine combination, when the machine produces products at a different theoretical maximum speed than the NPC. When determining the Standard, pay particular attention to the following:
- If you are recording a machine’s Standard speed for each individual product the theoretical output is always a dependent variable of the produced products.
- Standards need to be selected carefully. If you want to make each product equally effective, the Standard would have to be equally derived for all those products even though the machine at this moment operates at a different speed for each product! Simply said: If 1 KG takes 1min, 0,5 Kg takes 0,5 min, etc. This is the only way to discover whether certain products display indeed a higher or a lower performance rate, which would be an indicator of the machine’s potential for improvement!
- Do not include any restrictions when assigning the machine its Name Plate Capacity, but base the speed purely on the physical limitations of the machine (for example, the speed of rotation, the capacity of a heating element, the maximum pressure, etc.).
- Try to resist the arguments that state that the speed must be set sufficiently low in order to stay within a ‘feasible’ range. Counteract those arguments by emphasizing that OEE is a methodology to quantify and eliminate losses. Keep in mind that the aim is not to end up with a perfect 100%, but to narrow the gap between the present and the ideal situation as much as possible.
Impact of a too low maximum speed
If you are calculating a performance rate (and, therefore, the OEE value as well) based on a maximum speed (NPC or Standard) which is defined too low, you will NOT see the potential loss between what you defined to be the maximum speed and what it actually might be. In this, you hinder the effort to expose chronic performance rate losses.
Furthermore, it may (and will!) happen that the performance rate becomes higher than 100%, when the actual speed of the machine at one point becomes higher than the NPC or Standard (e.g. after improvements). This will influence the accuracy of the OEE.
So, when in doubt it is better to define the NPC or Standard too high rather than too low. In case of any doubt: add at least 10% or even 20% to the value. The only ‘problem’ could be now: your OEE is a bit too low. So what? At least in this way you are sure you do not hide any potential!
Using NPC to calculate OEE: OEE Top
OEE always uses the ‘Standard’ as a basis for its calculations. The Standard is the theoretical maximum speed for each product on this particular machine.
In addition, the ‘OEE Top’ can be calculated using the NPC. So now only ONE maximum speed is being used for EACH product on this particular machine. When the OEE Top is usually lower than the OEE, this might be an indicator to review your product allocation, since you may have allocated products to this machine that might have been more effectively produced on another one.