Nearly half of the performance efficiency (PE) can be lost due to micro-stops, speed loss, and slow speed alone. Speed targets are often set too low, which leads to performance efficiency exceeding 100%. This is a widespread issue among our clients, suggesting that the actual speed loss is often bigger than officially recorded.

When you want to assess the speed loss of a machine or system, you need to compare the actual speed of your operation to the maximum speed of that machine or line. Manufacturers have a few options for setting the maximum:

Theoretical maximum speed

Theoretically, a machine could run at its theoretical maximum speed if conditions were ideal and the machine was running to the very brink of its capabilities. But conditions aren’t ideal, so it would be very difficult for it to ever reach its theoretical maximum speed.

Nameplate capacity (NPC) or Design speed

Manufacturers often define the maximum speed of their equipment as the NPC (nameplate capacity). Although the number may vary from one machine to another, it’s common for suppliers to provide a more realistic number in order to meet customers’ expectations.

Ideal cycle time

Cycle time is the amount of time it takes to complete a process, such as producing one product. For example, if the theoretical maximum speed of a machine is 6 products per minute, then its cycle time is 10 seconds per one product.

Ideal cycle time is a software setting that defines the maximum speed at which calculations can be performed. It is based either on theoretical maximum speed or NPC.

When you calculate estimated speed loss, how can you determine the maximum speed of your equipment?

Based on the theory, you can use the theoretical maximum speed to calculate OEE and speed loss. When you focus on reducing speed loss as much as possible, the theoretical maximum speed is the fastest speed among all the speed definitions that we discussed, making this a sensible approach.

However, manufacturers are worried that setting such a high target could mean that staff will have to rush their work, which would reduce the quality of the product and cause equipment to wear out faster.

As a result, factories often set a slightly lower maximum speed. Finding that balance between exposing as much of your hidden loss as possible, while not sacrificing other aspects of your production, is an exercise in compromise.

It’s time for lean specialists to spread the word about the advantages of increasing maximum production speed while keeping all other OEE factors in balance.

Note: It is often necessary to determine maximum speed when the theoretical maximum speed isn’t known or when the nameplate capacity hasn’t been provided by your machine’s supplier.

How can you tell if a speed loss is due to slow speed or micro stops?

Most OEE systems don’t distinguish between slow-speed and micro stops. They include both problems in the same metric and report it as one number, the Performance Efficiency.

The first potential reason for this is the difficulty of differentiating between slow speed and micro stops.

Another potential reason is lack of demand due to insufficient education about speed loss.

While some manufacturers still track slow speed and micro stops together, others are beginning to realize the benefits of tracking these issues separately.

There are a couple of ways to track slow speed and micro stops separately:

• The simple way to check for slow speed or micro stops is to use a sensor to count products as they pass by. If the frequency is lower than expected, the system runs an algorithm to determine whether the cause is slow speed or micro stops. The system works well under most conditions; however, there are exceptions.
• The best way to monitor a conveyor belt’s movement is to use a piece of hardware that can sense whether the conveyor is moving or not. You could attach a rotary sensor under the conveyor belt to register its movement, or you could use your PLC (programmable logic controller) to send information about the status of production.