The Six Big Losses provide an equipment-based perspective on lost production time. Just like OEE, the Six Big Losses have their roots in TPM (Total Productive Maintenance). In fact, one of the goals of TPM is to eliminate the Six Big Losses.
One of the most effective paths to improving OEE is through the Six Big Losses. Let’s spend a little time exploring ways to leverage the Six Big Losses as part of your improvement program.
Addressing equipment failure (i.e., Unplanned Stops) is critical to improving OEE. For most companies, Unplanned Stop time is the single largest source of lost production time.
A prerequisite to successfully addressing Unplanned Stops is to understand the nature of the problem. In other words, attribute each instance of an Unplanned Stop to a reason for the loss – through reason codes. This will enable you to apply Root Cause Analysis to your top losses.
Here are some tips for effective use of reason codes:
A highly effective process for reducing Unplanned Stop time is a focused improvement activity (sometimes called a kaizen blitz).
In a focused improvement activity a cross-functional team selects one type of loss to address (often from a top losses report). The team then applies OEE loss analysis via a Root Cause Analysis or a 5 Why Analysis to identify potential causes and fixes.
Once an issue is fixed, it is important to update related standardized work procedures to lock-in improvements (and avoid “same problem/different day” recurrences).
Another major source of lost production time for many manufacturers is setups (also called Changeovers or Make Ready). We recommend expanding the definition of Setup and Adjustments to cover all planned stops (e.g., including preventative maintenance) that occur during planned production time. After all, any time that could productively be used for manufacturing is an opportunity for improvement.
A good starting point for Setup and Adjustments is to make sure you are consistent in how you measure Setup Time (to ensure you have an accurate information foundation). For example, your policy might be:
Some companies prefer to include startup or warmup time as part of Setup, in which case your policy might be:
Either way is fine – just make sure to document your policy and apply it consistently.
A well-established and highly effective way to address setup loss is SMED (Single-Minute Exchange of Die).
SMED is a collection of techniques for dramatically reducing the time it takes to complete a setup. The goal of SMED is to reduce setup times to less than 10 minutes (i.e., single-digit minutes). Each element of the setup is analyzed to see if it can be:
Here are several examples of changes that are often made as part of a SMED program:
While it is fairly easy to manually calculate performance loss, breaking it down into the underlying Six Big Losses (Idling and Minor Stops and Reduced Speed) is considerably more difficult. For most manufacturing processes, accurate and detailed measurement requires an automated system that measures individual cycles.
The root causes of Idling and Minor Stops and Reduced Speed are typically quite different, which is why they are independent elements of Six Big Loss analysis. This section does not make a distinction since many manufacturing operations do not have the capability of differentiating between Idling and Minor Stops (small stops) and Reduced Speed (slow cycles).
A good starting point for addressing performance loss is to validate ideal cycle times (to ensure you have an accurate information foundation).
Ideal cycle times should be available for every part and should represent the maximum theoretical speed of the equipment for that part (NOT ‘budget’ or ‘standard’ speeds that are slower than the maximum).
If your OEE Performance is ever higher than 100%, carefully review the ideal cycle time. You are likely to find that it is too high (and masking lost production time).
Look for patterns of significant performance loss (i.e., an unusual number of slow cycles or small stops). For example, performance loss may be more prevalent:
Once your team identifies a pattern apply Root Cause Analysis or 5 Why Analysis to identify potential causes and fixes.
Once a problem is fixed, it is important to update related standardized work procedures to lock-in improvements (and to avoid “same problem/different day” recurrences).
For high-speed equipment it may be worth purchasing a high-speed camera to capture cycles with enough resolution to see potential problems that would otherwise be invisible.
Some common countermeasures for performance loss are:
Process Defects and Reduced Yield occur during different stages of production, which is why they are independent elements of the Six Big Losses:
Note that the Six Big Losses capture lost time. They do not capture lost material when product is scrapped.
One of the most effective countermeasures to quality problems is to reduce variation (one of the central goals of Six Sigma). Variation is one of the reasons that there is often a higher rate of defects during startup – there is more variation in the process.
A very effective way to reduce variation is to pay close attention to equipment settings and materials:
These same countermeasures are also often effective for performance loss (e.g., resulting in fewer jams).
SIC (Short Interval Control) is a factory-floor process for driving production improvements during the shift. Each shift is split into short intervals of time (typically two to four hours), within which plant-floor employees use data to identify and implement improvement actions. These improvement actions may be countermeasures to ongoing or emerging problems, or they may be actions to improve existing production.
SIC can be very effective for all types of losses, because it dramatically shortens the time between a problem occurring and a countermeasure being proposed.
Even a fairly simple TPM (Total Productive Maintenance) program can have a significant positive impact on the Six Big Losses. Taking a “going back to basics” philosophy, when TPM was first introduced in Japan, many companies achieved significant improvements in OEE through various combinations of: