Efficient production processes are central to the success of a manufacturing company. Therefore, downtime or machine stoppages are often the greatest enemy. To better understand the impact of this on productivity and OEE (Overall Equipment Effectiveness) and to take appropriate actions, stoppages should be divided into different categories. Only in this way can an efficient increase in productivity on the shop floor be implemented.

Today, we highlight the different stoppage categories that have proven effective and point out what to look out for in order to keep stoppages on the shop floor under control.

Learn more about OEE software and the calculation of OEE in the linked articles.

What stoppage categories are there and how do they differ?

Stoppages can be divided into the following three categories:

• No production planned

• Planned stoppages

• Unplanned stoppages

We will now take a closer look at these individual categories and clarify how stoppages can be assigned to these categories.

No production planned

The category “No production planned” considers the periods when the facility was not scheduled for production. The facility is stopped, but from the production perspective, this does not present a problem. This distinction is important, as stoppages in the category of “No production planned” have no negative effect on the OEE.

Typical reasons for this type of stoppages include:

• Shift model - Often there is no night shift or production is not scheduled over the weekend.

• Company holidays - Some companies have company holidays during which operations are fully halted.

• Lack of orders - Shutting down some facilities due to low order volume.

Stoppages in the category “No production planned” do not lead to a reduction in availability, are not part of the “6 Big Losses”, and therefore do not result in a reduction in OEE.

The reason for this is that the OEE is a metric for production and should thus be influenced by production. The time in which “No production planned” is scheduled is mainly determined by production planning and order volume. Therefore, the production team itself has no influence over these losses, which is why they are not considered in the OEE metric.

If you are not yet familiar with the OEE concept and 6 Big Losses, feel free to check out the linked articles.

The following chart further clarifies the role of production time and time not scheduled for production concerning OEE:

The gray hatched area (far right) corresponds to the period during which the facility stands still because no production was planned. Thus, it represents the period of the category “No production planned”.

For the determination of OEE (green bar at the bottom) and availability (yellow bar), only the actual shift time is considered. The period of “No production planned” is not taken into account.

Planned stoppages

Planned stoppages are considered in the production planning and are calculated for a specific time. During this time, the facility is intentionally stopped. Set-up time for a facility, for example, is a typical planned stoppage. A simple rule of thumb: If the stoppage is not a surprise to anyone, it is a planned stoppage.

Typical planned stoppages are thus:

• Planned maintenance and inspections: Production facilities need to be regularly maintained. This includes cleaning, maintenance, calibration, and parts replacement. If this maintenance is planned in advance and ideally recorded in the production schedule, it constitutes a planned stoppage.

• Changeovers and set-up times: When production is shifted from one product to another, facilities often need to be reconfigured. This includes changing tools, resetting parameters, or modifying the physical setup.

• Breaks and shift changes: For break times, it matters how these are scheduled. If it is planned that the facility should continue operating during a break or a shift change, then these times should be recorded as planned stoppages, resulting in a loss of availability and thus OEE. If the break period is explicitly scheduled as a stoppage, then these stoppages should be assigned to the category No production planned. We recommend recording these times as planned stoppages to create an incentive to “keep running”.

Planned stoppages lead to productivity losses, but can never be completely eliminated. Rather, the goal is to strategically plan planned stoppages and ensure that they have minimal impact on the overall productivity of the site.

Practical tips for dealing with planned stoppages

Some points to keep in mind to minimize the impact of planned stoppages:

Minimizing effects on upstream and downstream processes:

It should be ensured that a planned stoppage has no or minimal impact on other processes. The upstream or downstream processes should continue to operate without losses, meaning that the buffers from upstream steps should never overflow, and the downstream processes should always be supplied with enough material so they do not “starve”.

Coordinating stoppages across the entire facility

Stoppages should be coordinated and distributed across all facilities to achieve an optimization of the entire site. This includes, for example, scheduling planned maintenance during periods outside of peak times.

Investment calculations for adjustments to machines for faster changeover times

A clean data collection of stoppages provides an ideal data basis to calculate valid scenarios and to validate new investments in the facility with an accurate ROI calculation.

Unplanned stoppages

Unplanned stoppages are the nightmare of an efficient operation. These stoppages occur unexpectedly and can have catastrophic consequences for production planning. In addition, unplanned stoppages have a significant impact on upstream and downstream processes, which can lead to enormous costs on the shop floor.

Typical unplanned stoppages include:

• Technical defect: A sudden technical failure or malfunction of machines unexpectedly halts production and requires unplanned repairs.

• Process defects: Problems can arise during processes that necessitate shutting down and cleaning the facility.

• Resource shortages: Inadequate supply of raw materials, delays in material delivery, or personnel shortages can cause production to come to a halt.

• Other unexpected events that cannot be clearly assigned to a specific group, such as power outages, human error, emergency stops, operator errors, etc.

The problem with unplanned stoppages is that they occur spontaneously and can disrupt the entire shop floor. Unplanned stoppages lead to increased waste due to unnecessary re-ramping, higher probabilities of an operational accident due to rush, and an increase in labor costs due to overtime needed to catch up on the production schedule.

To prevent and reduce unplanned stoppages, accurate monitoring of stoppages combined with suitable analytical tools can work wonders.

Differences between stoppages in the category Planned Stoppages and No Production Planned?

In practice, there are often difficulties in deciding whether a reason for stoppage should be assigned to the category “Planned Stoppages” or the category “No Production Planned”.

The OEE theory states: Stoppages that cannot be influenced by production should not be considered as availability losses in terms of OEE. This means, for example, that lengthy maintenance stoppages and larger facility overhauls (“turnarounds”) should not be classified as “Planned Stoppage” but rather as “No Production Planned”, thereby having NO negative impact on OEE. The same applies when facilities are shut down and shifts adjusted due to lack of demand (order shortages) or seasonal conditions.

It should be ensured that only reasons that can be influenced by production are recorded in the category “Planned Stoppages”. However, this does not mean that all unavoidable stoppages should be assigned to the category “Unplanned Time”.

An example helps to clarify the concept:

Stoppages due to set-up and changeover from one product to another are unavoidable. Therefore, it often happens that these are considered as not influenced by production and thus defined not as planned stoppages but as “No Production Planned”.

But what if the times for changeover vary? Sometimes 20 minutes are needed, sometimes 30, and sometimes 40 minutes? The fluctuations in these times should be captured in OEE, as they can largely be influenced by the production workers.

This often leads to discussions, as the OEE metric becomes significantly worse than expected. It is important not to see the OEE as an absolute number. It is more important to create comparability of the development of productivity and efficiency by establishing OEE. Goals and successes should be defined and celebrated based on the change in OEE over time.

Thus, the goal should never be: “We want to achieve an OEE of 90%!” but rather “We want to increase OEE by 10% over the next 12 months!”

Why categorize stoppages into different categories?

Now that we have examined the different stoppage categories, let us look at the benefits of using stoppage categories.

Reason 1: Stoppages in the category “No Production Planned” do not affect the availability factor of OEE.

As stated above, stoppages in the category “No Production Planned” should not lead to a reduction in the availability factor and thus not in OEE either. Without introducing the category “No Production Planned”, a distinction is not possible, and all stoppages would lead to a reduction in OEE.

Reason 2: Quick filtering during later analysis

The rough subdivision into categories helps quickly narrow down relevant error areas during analysis, recognize clusters, and filter data to quickly gain an overview.

Reason 3: Structure for the stoppage catalog

The categories help quickly find the right reason from the stoppage catalog when stoppages occur. The challenge with a stoppage catalog lies in ensuring stoppage reasons are detailed enough for meaningful root cause analysis. However, there should not be so many reasons recorded that finding and selecting the appropriate reason incurs too much effort.

If you have further questions about stoppage recording and stoppage management, please feel free to contact us at any time or book a demo. Here, you can get advice from one of our experts on your specific challenges.