Definition(s) of AVAILABILITY
How is TIME being used - Where did we lost TIME?Availability
A machine should be available when it is planned to be:
When and Why was it NOT available?
100% Availability
What is 100% when calculating availability depends on the KPI we want to use.
- In TEEP it is at 24 x 7: thus ALL the time there is.
- In OOE it is ALL shift time, including the unscheduled time
- In OEE it is ALL the shift time, excluding the shift time that was un-scheduled
This is described in detail in the Effectiveness KPI section
Loading Time
Loading Time in this definition is referred to as Scheduled Time: The time where we want to have an as high as possible Availability.
Categories of TIME
Was the machine running or not?
Being available, or not, can have multiple main reasons; each requiring a different approach.
| Type | Name | Definition |
|---|---|---|
| P |
= Running time |
Something is coming out of the equipment, regardless of the amount, speed or quality. A machine, spinning at top speed, not generating output therefore is not running…. Caution; batch producing equipment (like cookers, brick-ovens) are considered to run during their batch processing time. |
| F |
=Breakdown time |
The machine is not having output due to a machine related technical problem. |
| W |
= Idle time |
The machine is not producing output because it has to wait for something (like a setup, or raw material) Therefore, waiting for a technician during a breakdown is not Failure time but Waiting time! |
| L | Line Restraint |
The equipment can not generate output because it gets no input from the line (buffer empty), or can not give its output downstream (buffer full). Can be used at: Machines technically connected (by conveyers or pipelines) Non technical connections (cells, chain of equipment) Logistic connections, internally and/or externally A Line restraint is directly connected to the flow in the valuestream. It can reveal unbalanced lines as well as value-stream issues. |
| – | Unscheduled |
The equipment was scheduled yet is unscheduled from the total operations time for reasons beyond the scope of the production team. Usually this is time taken out of the regular shift-plan. (E.g. Christmas-eve)
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| X | Not Scheduled |
Time where no operations-activities where scheduled at all. ‘The factory is closed, the lights are out’. This is the time that was never taken into the shift schedule. (E.g. weekend)
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Definition of Production
A machine is running when there is output,
regardless of the quantity or quality.
Activities in
Production
| No | Time Usage | Time Type | ||||
| 1 | Production | P | F | W | L | – |
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‘Something is coming out of the machine’ regardless the speed and its quality. In batch producing equipment: From the start of the batch processing time until the end of the processing time. While loading or unloading the equipment, the product is not being processed thus the equipment is NOT running! It is waiting to be loaded. |
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| 2 | Reworking | P | F | W | L | – |
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The equipment is running to (re-)process product that was not produced first time right. Although this is normal production time in terms of OEE, in some cases it is useful to split the different types of production runs to make them visible in the Pareto of time-usage. |
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| 3 | Reduced Speed Run | P | F | W | L | – |
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The equipment is running at reduced speed; the equipment output is deliberately slowed down to balance a line or to execute an inline setup. Although this is normal production time in terms of OEE, in some cases it is useful to split the different types of production runs to make them visible in the pareto of time-usage. |
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Principles
Whether a machine is running or not, is always determined at the same spot and the same moment.
Why?
Products have a certain throughput time from entering- till exiting the machine.
This means that when at one point in the machine there is no more output (by definition the machine now stopped), it can be that at a later point there is still output (and vice versa when starting a machine.) So at another point the machine is still running.
In order to achieve a correct OEE, this time-shift should be prevented.
Definition of Failure
Failure Time:
The machine is not able to produce due to a machine related technical malfunction/failure/breakdown
Activities in
Failure
| No | Time Usage | Time Type | ||||
| 10 | Failure [function x] | P | F | W | L | – |
|
A failure (=breakdown) prevents production due to a technical reason in the machine. The categories should be chosen process oriented and should describe the phenomenon, not the cause. Choosing functional categories (like Electric, Mechanical, Pneumatic) is not supporting the cross-functional production team efforts. |
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| 11 | (Re)Adjustment | P | F | W | L | – |
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The machine is stopped WHILE A BATCH RUNS because adjustment is needed, to keep/get a product in spec. It is seen as a failure because at a certain point the equipment is no longer capable of producing the right spec due to a technical malfunction that needs to be corrected. The process is not capable of a stable operation. The technical reason causing this ‘drifting away’ needs to be eliminated. Adjustment and calibration after setup belong to startup. |
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Principles
Failure-Time categories should be PROCESS related rather than FUNCTION related.
What does it mean?
It doesn’t makes sense for OEE to make a decomposition of the machine and track every component for failures. You might do that in a CMMS system.
Case: In the course of a year, three bearings, two chain, one axis and one e-motor and 18 other components have lead to Failure time in OEE. What do you know now when generating a Pareto chart?
This is what we mean by a functional definition. When making a Process related definition, it could look like
- Entry Section Failure
- Turntable section Failure
- Filling section Failure
Why?
When making a Pareto Analysis now, it might turn out that the majority of the problems seem to occur in the Entry Section. This would now gain our full attention: what is going on there? Even without any further detailed information it could be we discover the maximum weight of a new product is higher then the equipment can handle in this section. We now can discuss our options for a solution.
Definition of Waiting
Waiting Time:
Although the machine in it selves -technically speaking- would be able to run, it (is) stopped and has to wait for something.
It has to wait for something to become in order before it can produce again.
Activities in
Waiting
| No | Time Usage | Time Type | ||||
| 20 | Setup | P | F | W | L | – |
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A setup in terms of OEE lasts from the last product X until the first product Y, regardless its quality. Caution: This is different from the SMED definition: Last GOOD product until first GOOD product! Depending the situation it might be useful to precede or succeed the setup time by a shutdown and startup category, to visualize in a Pareto where the main losses of setup are to be eliminated. |
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| 21 | Startup/Shutdown | P | F | W | L | – |
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The machine is not producing due to the fact that it has no vertical startup or shutdown. This can occur at beginning or ending of shift but also before or after a setup or repair works. This time is defined separately from the main reason to shut down the machine. Cleaning belongs here if it is part of the startup or shutdown activity, including startup of a new product (process-cleaning). |
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| 22 | No Operator at machine | P | F | W | L | – |
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The machine is available, but is not running because the operator is not operating it for example during his break, a training or a meeting. | |||||
| 23 | Quality problems – Process disturbance | P | F | W | L | – |
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The machine cannot run because the process cannot meet up with the specifications for (at that moment) unknown reasons. If the reason is known (i.e. bad raw material), it should be registered as such (Bad raw material = Waiting for correct material). |
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| 24 | Refill/Replace | P | F | W | L | – |
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The machine is stopped for refilling or replacing auxiliary, e.g. cutting blades, coolants, ink, oil, etc.
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| 25 | Loading | P | F | W | L | – |
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The machine is stopped while refilling/loading raw material, e.g. packaging materials, foils, and other raw materials.
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| 26 | Handling | P | F | W | L | – |
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The machine is waiting while required material is being handled.
This is a more specific situation from the ‘Waiting’ block.
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| 27 | Waiting | P | F | W | L | – |
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The machine is not running because the correct raw material or a tool is not present at the moment it is needed, or an action cannot be performed. In this block we find reasons for waiting that are caused by a weak planning. In the block ‘No Resources and No Personnel’ the reasons are ‘Force Majeure’. Consider carefully to define lack of raw materials as Line Restraint to reveal line-balancing and supply chain problems! Is it a capacity (=balancing) problem or just a handling or organizing issue? |
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It might occur we forgot to schedule or replace an operator.
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| 28 | Autonomous Maintenance & Cleaning | P | F | W | L | – |
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The main reason why the machine was stopped was due to AM activities, including cleaning. When a machine is being cleaned in the time it was standing due to another reason (i.e. waiting for raw material) the primary reason why the machine is standing is being registered. Process cleaning (like rinsing between two products) belongs to startup-shutdown. |
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| 29 | Preventive Maintenance during Loading Time | P | F | W | L | – |
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Scheduled time to perform PM. | |||||
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The machine is stopped at a not scheduled moment to perform PM or the machine is stopped at a scheduled moment but exceeding the scheduled time to perform PM during a scheduled time. PM happens ‘in process’; it is scheduled in the production sequence and needs to have a balance between enough and not too much. If well performed, the planned maintenance time will reduce the unplanned breakdown time. And most important: It is predictable time. |
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Paralell Activities
Quite commonly, one activity is being performed during the time something else occured. E.g. Cleaning is done while waiting at raw materials. Which of the two activities should be registered now?
Since we want to know EQUIPMENT losses; the real reason why the machine stands, is to be registered.
Principles
If two or more time-usages occur at the same time,
the primary reason for stopping is being registered.
What does it mean?
Example: Cleaning while changeover: The changeover is the primary reason to stop
Definition of
Line Restraint
Line Restraint Time
The machine is fully functional but cannot run due to receiving no input from the upstream process or being not able to get rid of its output due to a problem somewhere downstream.
Activities in
Line Restraint
| No | Time Usage | Time Type | ||||
| 50 | No Input (in Line process) | P | F | W | L | – |
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The machine stands still due to no input from a preceding process that has a technical link, e.g. a conveyer. In lines it can be useful to get an overview in the Pareto to show what process decreases the effectiveness from this machine the most. In that case the time usage is split in two or more items like; ‘no input due to process x’. |
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| 51 | No Output (in Line process) | P | F | W | L | – |
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The machine stands still due to the fact it cannot get rid of its output; mostly due to a stop in a succeeding process that has a technical link, e.g. a conveyer. Also see block No Input. |
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Strict or Extended use
- A line can be thought of literally: several machines tied together with conveyors, pipes etc.
- However, applying Lean-Principles, those categories can be very well used to detect unbalanced situations between machines not technically tied together, e.g. in a cell or between several departments.
- It can also being used to detect flaws in the supply-chain.
a (L)ean or (L)ogistic restraint.
OEE Solitair
To detect how well the machine would have performed would it not be restraint by the rest of the line, it is possible to calculate the “OEE Solitaire” (See ‘Effectiveness Definitions’). In OEE Solitaire, all Line Restraint time is excluded from the total time.
Warning
Remember: Every product on a machine has a certain theoretical maximum speed, regardless the fact this might be too high for the line it is in.
- The machine has a structural over-capacity while it is not a bottleneck.
Do not try to ‘mathematically’ balance the line by reducing the Standard (the maximum speed for a product on a machine). By doing so you will hide a potential loss (the unused over-capacity of the machine). - Do not try to run a line restrained machine as fast as possible! Although the performance rate would go up, the availability will go down due to line restraints and worse: it will de-stabilize the flow in the line! Slowing down this machine will NOT reduce the OEE, however it will run smoother and as result the OEE might even raise!
Definition of
Unscheduled
Unscheduled Time:
During the operations time, the equipment is taken out of operation (un-scheduled)
Reasons to un-schedule the equipment could be:
- the product is not needed (over-capacity);
- it is not allowed to run (due to Governmental regulations or contracts);
- ‘Force Majeur’ (catastrophe’s outside of the company);
- the equipment is ‘handed over’ to an other party (e.g. R&D).
Remember: There was a shift planned, yet it was unscheduled.
Don’t confuse this with NOT scheduled.
During ‘Unscheduled time’ no regular crew is present.
If there is, register this time as ‘Waiting time’!
Activities in
Unscheduled
| No | Time Usage | Time Type | ||||
| 60 | No Orders | P | F | W | L | – |
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The machine is not required to run due to a lack of customer orders; the capacity is not needed. (customer = the one who pays for the product!) Beware! A warehouse will never be ‘the customer’! Do not hide over-production! |
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| 61 | No Personnel Available | P | F | W | L | – |
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The machine is not scheduled for production because there is no operator present due to ‘force majeure’ like
If there is no operator available due to a lack of planning (so the machine was supposed to run), choose ‘no operator at machine’ or ‘wait for operator’ (both (W)aiting). |
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| 62 | No Resources | P | F | W | L | – |
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The machine is not scheduled for production because a resource is not available due to reasons OUTSIDE of the company, including energy; thus reasons other than lack of planning or handling (in such cases: Waiting).
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| 63 | Legal Constraints | P | F | W | L | – |
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The machine is not scheduled for production due to legal constraints which do not allow the machine to be operated.
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| 64 | Test Production | P | F | W | L | – |
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The machine is not scheduled for production to make it available for product development, testing new products or processes etc.
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Principles
The goal of the machine in not ‘to run’;
The goal is to fulfill the demand.
What does it mean?
It is better to stop a machine when there is no demand than keeping it running.
Unscheduling will NOT affect the OEE, however it will reduce the OOE and TEEP
Definition of
Waiting while Unscheduled
Waiting Time registered as ‘Unscheduled’
Activities that normally would have been performed during loading time, can sometimes be scheduled outside loading time.
In a two-shift operation, the machine might be setup or cleaned during the night or in the weekend, in absence of the regular crew.
- Preventive Maintenance could be carried out at a moment no production was scheduled. In a 3 shift operation from Monday to Friday, the PM could be scheduled in the weekend, thus not affecting the loading time.
- The activity is necessary to perform the scheduled production; thus cannot be skipped. This means the OEE is artificially high. When Loading Time needs to be extended (e.g. more capacity is needed) and 2 shift becomes 3 shift, or 3 becomes 5 shift, those activities automatically will fall into the loading time, thus dropping the OEE to its real value!
- Usually, outside the loading time, there is no pressure to get the machine up and running; this might result in a less effective performance of the activity scheduled outside of the loading time.
- The effect of these activities on the OEE (“by doing more PM, less failures occur”) is not clear.
Activities in
Waiting while Unscheduled
| No | Time Usage | Time Type | ||||
| 70 | Preventive Maintenance outside Loading Time | P | F | W | L | – |
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PM necessary to maintain a high availability of the equipment, being performed outside of the normal Loading Time. In a 3 shift operation from Monday to Friday, the PM could be scheduled in the weekend, thus not affecting the regular loading time. Overhaul is a specific form of preventive maintenance. If the machine is unscheduled for a longer period of time to be completely overhauled, it should be considered ‘PM during loading time‘ thus (W)aiting. Only if the overhaul is performed at a moment the equipment would anyway not be running (e.g. because the facility is closed) it belongs in this block. If it is done in a period where there are no orders, ‘No Orders’ is the reason for stopping the machine, and not the overhaul. Thus No Orders is registered! To identify PM during No Orders, make a separate category: PM during No Orders. |
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PM during loading time can take longer than originally planned, and continues outside loading time; this can be made visible here. If PM in Loading Time takes more time than planned and is being continued outside Loading Time it becomes Unplanned PM Outside Loading Time. |
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| 71 | Activities performed outside Loading Time | P | F | W | L | – |
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Activities that normally would have been performed during loading time, are now performed outside loading time. In a two-shift operation, the machine might be setup or cleaned during the night or in the weekend, in absence of the regular crew. |
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Principles
OEE visualizes ALL potential losses,
even when they are clever or ‘cheap’ organized!
Definition of
Not Scheduled
Not Scheduled
All time the machine is not being used or touched for operation, maintenance, cleaning etc. “The light is out”
OEE typically registers ALL scheduled shift time, including ALL downtime (planned and unplanned), all unscheduled time AND all time spent outside scheduled shift time.
The remaining time is Not Scheduled and needs not to be registered to calculate OEE.
However, OEE data can be used to calculate Operations Effectiveness, Asset Utilization, TEEP etc. (See Effectiveness KPIs)
To visualize losses due to not scheduling the equipment, reasons for not scheduling might be registered. They might also be calculated: Total time – Registered time)
Activities in
Not Scheduled
| No | Activity | Category | |||||
| 90 | No 24×7 Capacity needed to fulfill regular demand | P | F | W | L | – | X |
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At incidental fluctuations in demand use ‘unscheduled’; regular shifts have to be unscheduled due to non-regular or incidental fluctuations in demand.
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Principles
A machine scheduled for a 1 shift service,
is ‘not scheduled’ the other potential (4) shifts
If shifts have to be taken out of the normal production schedule, register it as ‘Unscheduled’ due to its reason, i.e. ‘No Orders’ or ‘Lack of personnel in the region’.
Bottom line, having equipment not scheduled means: Capacity not fully utilized. In other words: Not enough orders…
OEE Definitions
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