All you want to know about
PERFORMANCE (SPEED) in OEE
17 Questions about Performance (Speed) in OEE
1. What is Ideal Cycle Time (or 'Standard Cycle Time', 'Maximum Speed')?
The Ideal Cycle Time, also called the
- Standard or
- Standard Cycle Time or
- Maximum Speed,
is the theoretical maximum speed of a specific product on a machine.
The Ideal Cycle Time, is used to calulate the Performance Rate of a machine.
Theoretical Maximum has to be taken seriously:It means thisproduct can NEVER be made faster on this equipment. (Unless the equipment or the product is being modified)
2. Why is the Ideal Cycle Time (or 'Standard Cycle Time') so important?
Q: Why is the ‘Ideal Cycle Time’ (=’Standard’ or Theoretical maximum speed) so important? Why can’t we just use our current running speed, we go very fast!
Daniel Högfeldt • This is probably the most important part of the OEE calculation. The formula that gives the performance, always includes an ideal cycle time or an ideal rate. To get the cycle time from the rate just divide 1 by the rate and vice versa.
Standard Cycle Time
The standard cycle time or speed rate should be the best speed or cycle time achievable for that particular job. For instance the best cycle time achieved in the past could be a good standard cycle time to use in the OEE calculation. If the machine after a while has to run slower due to for instance an old die, then that would show in the performance rate as it would drop.
Arno Koch • Even what the machine has proven to be capable of in the last years, usually is not what it could have been doing under ideal circumstances. So carefull! Always seek what it couldhave been doing THEORETICALLY. If possible; do the math. Make a heat transition calculation, usethe maximum pump capacity or rotation speed and never ask whether that speed would be ‘Realistic’. Today it is not, otherwise we would run it! The goal is NOT to acive this speed,wejust need a fixed refference point for the KPI!
Daniel Högfeldt • Changing the standard (making it too low) would just hide the fact that the machine is running slower than it theoretically could.
If no standard cycle time or rate is available for the job, a generated value from the best couple of days from the past year could be used. That way you would know that that rate once have been achieved and therefore it should be achievable again.
Arno Koch • I would even strongly suggest to add an extra 10-20% on top of that. It is absolutely not rare to see that this speed is broken relatively soon.
The Standard in the OEE Calculation
It is very important to find a good standard rate to get a good OEE value, since in its basic form, OEE can be measured just by using the formula: OEE = Good Pieces Produced * Standard Cycle Time / Loading Time. That formula would give the same result as the three ratios; Availability, Performance and Quality rate multiplied together. All information needed for the simplest OEE calculation is:
- How many products meeting specifications was made?
- How much time was scheduled or allowed for production of that product? (Loading Time)
- What is the ideal or expected cycle time or speed for units of that product?
Example: OEE calculation using its simplest form.
A. Loading Time : 360 Hrs
B. Good parts made: 15.000 Parts
C. Standard Cycle Time: 0.9 min/part
OEE (B*C/A) = 15000*0.9/(60*360)=0.625 360 hours 15000 parts 0.9 min/part
This is an easy way of checking if the OEE calculation made was accurate or not, but it does not reveal where the lost time was in the process. It could be a way for plants without good data collection to get accurate OEE.
For getting an accurate OEE the key elements are
- how to define Loading Time and
- that a good Standard Cycle Time is chosen.
If the cycle time is set to long according to what it is achievable of doing, the risk is that wasted time is overlooked in downtime or/and producing scrap. For example, if a machine have an OEE of 90% that looks very good. When looking at the three ratios it could look like this if a too high standard cycle time was used: Availability = 70%, Performance Efficiency = 143% and Quality Rate = 90%. This would mean that during a shift of 8 hours the machine was down for 144 minutes and was producing scrap for 33.6 minutes (100 scrap parts * 20.16 sec/part actual cycle time) with a total of 177.6 minutes of wasted time. If only looking at the OEE the wasted time would be 480 minutes * 0.2 = 96 minutes of wasted time. That would mean 81.6 minutes of “forgotten” waste.
If instead the standard cycle time was corrected to a performance rate of 100% (which might not be true, but it is still more accurate than 143% and could be corrected further as time will tell what the standard time should be), in this case that would mean 20.16 seconds per part. Then the OEE would be: 70% * 100% * 90% = 63%. That would mean a lost time of 480 minutes * (1-0.63) = 177.6 minutes. In real life the machine might be able to run at an even faster speed and then there would be even more losses in time not revealed because of the standard cycle time was set to high (speed rate was set to low).
Importance of correct ideal cycle time
The conclusion of this is that it is very important to have a correct ideal cycle time to compare to the actual cycle time to get a good performance result. For every different product the machine is running, a different ideal cycle time could be used. Another approach could be to use the same cycle time (best cycle time) for the entire product family run on the machine.
On those parts where the rate has to be lowered the reason should be pointed out in a comment column on the OEE sheet, so the loss due to difficult parts to manufacture can be recognized.
3. How to determine the maximum speed (Ideal Cycle Time)?
How can I calculate maximum (Theoretical) speed of my machine when no manufacturer data is available?
Arno Koch • The most important thing here is not to set the maximum speed too low; otherwise whenever your actual speed will exceed the maximum speed, your OEE calculation is no longer valid.
How to determine the maximum speed?
There are 3 possible solutions in this situation:
Per product group (ie one color, two colors, three colors) ask the following questions.
- Do we know what determines the THEORETICAL maximum speed (so limited by laws of nature…). If so, I would suggest this is your maximum speed. Even if it seems to be impossible to achieve now. No problem; it will just lower your OEE, remember; it is not your goal to have a high OEE, it is your goal to find ALL potential losses!
- What was the highest ever ran speed in the last two years? Take this and add an extra 20% to make sure not to go over the max speed in the next years.
- If there is a possibility to run the machine empty, try what it can do. Again; you are looking for a THEORETICAL maximum speed, to be used as a reference point for the next years; it is NOT your goal to be achieved. Your goal is to stabilize your machine and improve it step by step.
4. How to determine the Ideal Cycle Time when a machine has to be (un)loaded?
Q: At my company we are currently doing a book study using your book ‘OEE for the Production Team‘. As we work through the book we came across a question; When calculating OEE do you (the calculation) account for the loading and unloading of material in the machine? We have been calculating the OEE using TAKT time (19 seconds) but the machine cycle time is only (13 seconds). Is this important? Because if there is improvement it will be realized in both versions, correct? In Chapter 9 the exercises do not include load/unload time. Your feedback would be appreciated since material loading is a fundamental function in our facility.
Thank you, Pat Holden
Arno Koch • When defining the maximum speed for the equipment, many issues come together.
OEE visualizes https://oee.coach/performance-definition/ALL effectiveness losses
Let’s start with our a basic statement why we use OEE:
In OEE we want to uncompromisingly visualize ALL potential equipment effectiveness losses.
So when looking at ‘speed’ we have to ask: ‘Speed of what?’ Yes of course, speed of the equipment, since this is what OEE is measuring. Not the speed of the operator nor the line nor logistics. We want to know “What could the machine theoretically do if it was not restrain in ANY way, versus what is it actually running (due to hundreds of reasons that might become subject to study by kaizen teams etc.) and what is restraining it, where could we improve?
What determines ‘maximum speed’?
Then we find out: The theoretical maximum speed is not determined by the machine alone, but by the combination of the machine and the product it is making. Example: Theoretically it would take 3 times longer to fill a 1 liter bottle than to fill a 33cl bottle, right?
Name Plate Capacity
Now we can talk about the Name Plate Capacity, which is the design speed of the equipment, usually defined based on one ‘norm product’. But the NPC is not suitable for our day to day operation where we run a certain product mix with different characteristics.
We now need to define different speed-groups: products with the same characteristics, having the same maximum speed on the equipment. This maximum is called the “Standard” (the theoretical maximum speed for this product on this machine)
Again: This is the speed the machine could theoretically run this product, would it not have been restraint in ANY way. You will soon end up looking for physical limitations like the amount of energy that could be transferred etc.
The ‘standard’ has NOTHING to do with whatever you think is realistic or realized in practice. It is a reference point that will be stable for the next couple of years until the product or the machine is fundamentally changed.
How will we see (un)loading in the OEE?
Imagine your ‘machine cycle’ (the time the machine theoretically needs to do the actual conversion) is 7 seconds, but before and after this conversion the operator needs time to handle the product: 9 seconds before and 12 seconds after. The ‘product cycle’ is now 9+7+12=28 seconds. Before and after each product, the machine is suffering a minor stop. This will pop-up in the OEE as a speed-loss. When the machine is set to run at 7 second speed, we will now find out your speed-rate will not exceed 25%! And this of course is true: The machine, even when it is ‘running’, still waits 75% of its time for handling! A huge potential is waiting to be found and improved!
I hope this answers your question?
5. What is the 'Theoretical maximum speed' when manually unloading?
Q: According to the fundamentals of ‘method-time measurement’, the standard time of an operation includes some fatigue allowance when the machine is loaded / unloaded manually by an operator.
Should I consider this standard time as theoretical maximum speed? Or should I eliminate the fatigue allowance from the standard time to find the theoretical maximum speed?
Arno Koch • By definition, OEE identifies and visualizes ALL potential EQUIPMENT losses; so also the time the equipment has to wait for the loading/unloading. This might be a subject for an improvement activity.
OEE measures against THEORETICAL maximum speed, not ‘CURRENTLY assumed to be the best possible’.
Hint: When your OEE drops down due to difficult loading and unloading, causing operators to become fatigue; then improve the loading and unloading instead of hiding this by taking it out of the OEE!
6. How to approach resistance against an Ideal Cycle Time?
Q: I am arguing with our management about the definition of the maximum speed. They are afraid our OEE will become too low..? How do I proceed?
Arno Koch • The definition of the maximum speed is mostly a ‘hot’ discussion. So my dear, you are in good company…
100% OEE is a reference, not a target
It takes quite a paradigm shift to stop seeing 100% OEE as ‘a target’ or even as something that could be achieved.
I see OEE as no more than a reference point. Compare it to your compass when going for a walk in the mountains. The needle should at all circumstances point to the north. Is north your target? Will you always walk north? Of course not. Does it come handy to have a reference point, so you will always know what directions you are heading? Sure yes!
For many it helped to start seeing 100% OEE as their ‘north’; no more than a reference point that will stay the same for the next couple of years so you can walk your improvement-expedition; taking the directions you can and need at the moment. And keep on track, also during the storms of heavy operations….
Theoretical Maximum Speed
Typically the ‘standard’ (the theoretical maximum speed for a specific product on machine) is rather defined too low than too high, resulting at some moment in a performance rate over 100%, making the beautiful balanced calculation of OEE rather silly not to say worthless.
Now what is the worst that may happen when you really put the standard too high?
Well, your OEE will never become 100%… Or will consequently be somewhat lower. So what??
The target of OEE is not to become 100% and the value it selves is not of much relevance since it even cannot be compared against it selves. The relevance is in the under laying loss structure. The more losses you are willing to reveal by defining OEE smartly, the more improvement potential you will find and see.
OEE Industry Standard
To help you doing so there is an OEE Industry Standard that recently has been completely redone and can be found here: OEE Industry Standard
Having discussions about OEE definitions in your company is great because it may lead you to the reasons why the losses are still there; so listen careful to all the arguments why “it can’t be done”.
When turning those arguments around, you’ll know what needs to be done! It works like this:
Invite your partners to give as many as possible reasons why a certain speed, or quality, or uptime is ‘not realistic’; why it cannot be done. Make a list. And give it this title: TO DO.
You might be astonished how much we are sometimes caught in our own assumptions.
I hope this helps a little. Good Luck on your Journey!
7. Is the maximum speed 'realistic'?
Is the maximum speed ‘realistic’?
Many people are afraid to define this theoretical maximum speed, since ‘this is not realistic, we will never achieve this’.
Well, I do not know if you will never achieve this. I do know that out there are tons of machines that after years, even without TPM, run far over their design capacity! So who knows how far we will get!
It is precisely the goal in this definition that we will not easily trespass the 100% limit of the performance rate, so we will keep a fixed reference point, allowing us to determine over the years whether and how much we are improving.
So the maximum speed value is merely like the north on our compass: It helps us to keep direction, rather than defining we have to go there! Think carefully about this, since it has quite some consequences.
Ok, now you understand why handling is NOT included in the ‘standard’. But how are we going to see ‘handling’ in the OEE?
8. Why can I not just use realistic values for Maximum Speed...?
Arno Koch • The definition of the maximum speed is in most companies ‘hot’. So you are alone… It takes quite a paradigm shift to stop seeing 100% OEE as ‘a target’ or even as something that could be achieved.
100% OEE is NOT a target!
Try to see 100% OEE as no more than a reference point. Compare it to your compass when going for a walk in the mountains. The needle should at all circumstances point to the north. Is north your target? Will you always walk north? Of course not. Does it come handy to have a reference point, so you will always know what direction you are heading? Sure yes!
For many it helped to start seeing 100% OEE as their ‘north’; no more than a reference point that will stay the same for the next couple of years so you can walk your improvement-expedition; taking the directions you can and need at the moment. And keep on track, also during the storms of heavy operations….
Typically the ‘standard’ (the maximum speed for a specific product on machine) is rather defined too low than too high, resulting at some moment in a performance rate over 100%, making the beautiful balanced calculation of OEE rather silly not to say worthless. Now what is the worst that may happen when you really put the standard too high? Well, your OEE will never become 100%… Or will consequently be somewhat lower.
Higher maximum speed gives lower OEE
So what?? The target of OEE is not to become 100% and the value it selves is not of much relevance since it even cannot be compared against it selves. The relevance is in the under laying loss structure. The more losses you are willing to reveal by defining OEE smartly, the more improvement potential you will find and see.
Use the right definitions!
To help you doing so there is an ‘OEE Industry Standard’ that has been completely redone in 2020 and can be found here:
OEE Industry Standard (Feedback is highly appreciated)
Turn resistance into action!
Having discussions about OEE definitions in your company is great, because it may lead you to the reasons why the losses are still there; so listen careful to all the arguments why “it can’t be done”.
When turning those arguments around, you’ll know what needs to be done! It works like this: Invite your partners to give as many as possible reasons why a certain speed, or quality, or uptime is ‘not realistic’; why it cannot be done. Make a list. And give this list the title: TO DO.
You might be astonished how much we are sometimes caught in our own assumptions. I hope this helps a little. Good Luck on your Journey! Best, Arno Koch
9. How to measure OEE for different products & different cycle times...
Q: We have lathes and machining centers that we use where we have multiple set ups and many different parts with multiple cycle times run on those machines. We will be applying OEE to these machines and I am curious what others have done when the cycle time for the parts always changes. When a process has a constant cycle time, Performance measures also remain constant. Averaging cycle times will not provide accurate information.
Arno Koch • This type of equipment indeed challenges a proper OEE implementation…
I Agree, averaging cycle times is not the way to go. What then? First of all it helps when the variation is not too wide.
Determining the theoretical maximum speed
To determine the theoretical maximum speed, the maximum cutting speed multiplied with the amount of material to cut has to be determined. Different types of raw material (Alu, V2A, Bronze, Nylon etc) have different maximum cutting speeds, and the amount of material to be removed can be different per product. (Two physical limited parameters)
(The complexity of the product is not a ‘maximum speed inhibitor’ since theoretically this can be overcome).
Probably the 80-20 rule is hidden somewhere! In other words, usually it is possible to divide the product portfolio into a limited amount of ‘maximum speed groups’;
Now the operator can go through a simple ‘questionnaire’ or ‘decision matrix’ to determine the maximum speed of his next product and uses this as the ‘standard’ against what the performance rate is calculated. (Example: Vertical axis the material determining the cutting speed, horizontal axis the class/group of amount of cutting needed).
The goal is not to have a 100% correct calculation. The goal should be to give the operator an indicator, showing him where improvement potential is hidden. This is most likely not in maximizing the actual (cutting) speed. And if it is, it is enough to know this is the place to look for optimization.
I am curious if there are other solutions being used in similar situations… Please let us know!
10. How to determine the Ideal Cycle Time for multiple parts/cycle times?
Daniel Högfeldt • On machines where more than one job number is made during the day a volume weighted ideal cycle time has to be calculated. That is because a straight average would not take into account for how long that job number was run. A volume weighted average (Honda 2000) looks at how long it should take to make the pieces that was produced and is then divided by the total number of pieces produced. See table 8.
Incorrect Method Straight Cycle Time Average = (23+42+51+29+36)/5 = 36.2 sec.
11. (When) could we change the Maximum Speed?
Q: After what time could we change the maximum speed, that results in 100% performance?
Arno Koch • The maximum speed should be a reference point to OEE. It should not change unless after reengineering the equipment. Therefore, the maximum speed should be derived from the THEORETICAL maximum speed of the equipment.
In case of an extruder this should be not too difficult:
- Find out: what is the maximum amount of KG raw material the extruder can extrude “without die”. Bluntly said, the “pumping capacity” of the extruder.
- Now determine the weight of the product and (questionably including spreaders and runners) calculate how many product could be made with this amount of raw material.
This is your base-value per product for the maximum speed.
You might find out you have a not so profitable product allocations on this machine due to different cooling time. DO NOT try to ‘correct’ this in the maximum speed, yet let the different performance rates show the different effectiveness for those product!
IF you apply the ‘best of best over time’ method, as a rule of thumb at least raise the highest found values with 20 or 25%. Chances are high now maybe you are in the direction of the real value (experience based on analyses of more than 1000 machines)
12. (How) Can Performance go over 100%? What's wrong?
Q: How can the Performance Rate OEE go over 100%?
The Performance of OEE can go over 100% when there was more output produced than theoretically possible according to your definition.
Arno Koch: There are three ways this could happen:
1. ‘Maximum Speed’ defined too low
The most common way to produce more output than possible according to your definition happens in cases where the defined maximum speed is lower than the real maximum speed.
This is the reason why the THEORETICAL maximum speed should be defined as the 100% value of performance. Do not use some ‘practical or actual maximum’ that is just practical for the moment but can be improved in time. If the machine CAN go faster it WILL go faster one moment or the other.
The golden rule for Maximum Speed in OEE:
The real maximum speed can only be improved by re-engineering the machine or product.
2. Making a data entry-mistake
Another possibility to have more than 100% performance is when somebody made a data-entry mistake, where the entered actual output might be higher than the maximum output (Time x Maximum Speed).
In this case the performance rate would go over 100%
3. Registering less Production time than actually happened.
Imagine someone states there was 2 Hrs mainenance performed, but actually it was just one hour. The other hour the machine was running. Now there was a production volume for two hours yet only one hour is being registered. In that case the output most probably is higher than theoretically possible in this one hour.
Whenever this occurs it is important to find out WHY this was done? What was trying to be achieved?
Consequences of a too high performance rate
- Imagine you make 20% scrap (Quality = 80%) and the machine is idling 30% of its time, (Availability = 70%) but due to a too low standard, your performance is 150%. You end up with a world class OEE of 70% x 150% x 80% = 84%. Of course that is nonsense and leading away the focus of the losses being present!
- Several graphs and analyses would get distorted, since OEE is a balanced system, with 100% as maximum.
13. What are 'Minor Stops'?
Arno Koch • A machine that is not running is not ‘available’, thus it is suffering an availability loss. However the question may be: when is a machine not running? If it has a 1 second hick-up, did it stop? The ‘minor stops’ concept solves this dilemma.
Stop, Small Stops or Minor Stops?
By definition, many OEE registrations have a threshold somewhere between 1 and 10 minutes, to detect a machine stop. This means: when the machine stops longer than the threshold value (usually 5 minutes) the stop is considered to be an availability loss and needs to be identified. The operator assigns the stop to e.g. a failure- or a waiting- code. If the stop is shorter than the threshold, it is considered to be a ‘minor stop’. A minor stop will not be identified with a stop-code.
Stops: Individually identified or not
This means minor stops do not pop up as individually identified stops. They are not seen as availability losses, but they show as a speed-loss. This makes sense, because if we ask the operator to tell us the reason for each machine stop, even the very small ones, the registration-stress will become unbearable.
14. How to visualize all speedlosses, including Minor Stops?
Q: We tried to measure speed losses and minor stops electronically, yet although tons of data where gathered, it was difficult to see what we needed to do. How can I visualize all speed losses, including minor stops, in a way that we can reduce them?
Arno Koch • Electronic data acquisition to detect minor stops and other speed losses, usually consumes quite some effort. And indeed, enormous amounts of data are being gathered. The typical assumption in such an IT approach is that when there is data, this will lead to information, in this case: information what to do. This is at least doubtful, as you discovered. Such systems more often lead to focus on the data, and not at the information that should lead to the needed improvement…
The question I will try to answer here is:
How to proceed with OEE to reduce speed losses?
1. First find the reduced speed losses:
1.1 Define the theoretical maximum speed of the equipment
1.2 Allow the operator to register the ‘Set Speed’; this is the speed he sets the machine to work at
1.3 The difference between the theoretical maximum speed and the set speed will result in ‘reduced speed loss’
The machine has a theoretical maximum of 100 units/min
The operator sets the machine on a set-speed of 80 units/min
Now 20 units will not be produced due to the deliberately reduced speed of the equipment.
2. Discover the causes of “Reduced Speed Losses”
The operator will reduce the speed of his equipment when he experiences
- Quality problems
- Process disturbances
- Technical failures
- Timing problems
An experienced operator might typically tell you: “If I set the equipment to run at 80 units/min, I will have the highest output and few problems”
3. Find ‘visible minor stops’
By definition, many OEE registrations have a threshold somewhere between 1 and 10 minutes, to detect a machine stop. If the machine stops longer than the threshold value (usually 5 minutes) the stop is considered to be an availability loss and needs to be identified with i.e. a failure- or an idling- code. If the stop is shorter than the threshold, it is considered to be a minor stop and will not be identified with a stop-code. This makes sense, because if we ask the operator to tell us the reason for each machine stop, even the very small ones, the registration-stress will become unbearable.
4. Find the ‘Invisible Minor Stops’
In the next topic, I describe a method to approach Minor stops in ore detail, assuming you have good OEE Software
15. How to visualize (part of) 'Minor Stops' in the Availability Rate?
Can Minor Stops be visualized in Availability?
The amount of minor stops can be really frightening high. Since many machines are loaded with sensors we can pull a nifty little trick. We can bring the majority of such short stops to the availability rate without bothering the operator. This is how:
1. Determine (minor) stops thresholds
1.1 Define a threshold that is small enough in order to see as many as possible stops as ‘Waiting’ in the Availability analysis, yet large enough to prevent operator stress. In doubt: 5 minutes will mostly do.
1.2 Define a second threshold at e.g. 1 minute. If there is an automatic data collection, allow every stop between (in this example) 1 and 5 minutes to be gathered as a separate time category in the availability losses. When running a Pareto analysis on time losses, one category will be ‘Small stops between 1 and 5 min’.
2. Grasp the bulk of short stops in availability
2.1 You now created a time category that collects all kind of stops with potentially many different reasons. However: when they occur you cannot miss them. This is relevant because the machine each time really stops for a considerable time-span.
2.2 If this category pops up high in your Pareto, you know what to do: Go to Gemba and talk to the production team; ask the operator, teamleader, technicians and for all: make your own observations. In the vast majority of the situations I investigated, this gave enough input to start eliminating the right root-causes.
3. The real minor stops go into Performance
3.1 Stops smaller than the lower threshold can of course also be registered by your automated data collection system. The problem is: What do you know if the system tells you there were 7856 stops between 0,11 sec and 1 min…?
And what if the machine did not really go to a speed of zero, when it just drops back in speed and goes up again? Your sensor may not even noticed an actual stop, yet you miss output against what was expected!
3.2 Of course you NEED to know there where a lot of such minor stops. However I see no value in the precise registration of those minor stops. They can occur anywhere in the equipment and have a multitude of reasons. You an register the signals with historian databases, but you stillwill not know the real reasons; this information is simply not present, so do not even start trying it…(been there, seen it all). So let’s look at a better alternative:
4. Calculate the real minor stops!
4.1 If you know the speed the machine was set to run, and you know the time the machine was running, it is easy to calculate how much output could be expected during the time the machine was running at this set speed. If the actual output is less, the difference can only be explained by the presence of minor stops. Simple and 100% accurate!
The machine was running 10 minutes at a set speed of 80 units/min. We now expect an output of 10 x 80 = 800 units If the actual output was 780 unit, we lost 20 units in minimal 1 minor stop of 15 seconds (at a set speed of 80 per min it takes 15 sec to make 20 units) and maximal 20 stops of 0,75 seconds
4.2 If the minor stops are really stops, this is visible and often audible if you go to the machine. Even at high speed machines like a filler in a bottling line where 700 or more bottles per minute pass by, the empty positions that represent a minor stop of 0,085 seconds (!) can be seen.
4.3 As soon as you can see what happens, you can start a Small Group Activity (‘kaizen team’) to observe the phenomena and make a root cause analysis.
5. Find ‘invisible minor stops’
5.1 If the machine is set to run 80 units per minute, and no single stop can be seen or identified, and yet only 78 units come out, we have to find the invisible minor stops.
1. Is the set speed (that you read on the scale or display) really the speed the machine runs? Calibrate this setting if you like to be sure.
2. If the machine is really set to 80, there are no stops and yet only 78 units come out, the only explanation can be the machine is not running at a constant speed. Due to fluctuations in friction, electricity, pressure etc. the speed incidentally goes a little down, resulting in the end in some lost cycles.
3. Solve root causes instead of registering more of the same
6. Understand ‘Heinrichs Piramyd’
In all the 3 stages I described here, there is an opportunity to find ‘small irregularities’. Those lead to a process which is not fully stable.
Make sure to understand the power of ‘Heinrichs Piramyd’ (or Burt’s Law).
If so, you know that whenever you solve a detail that popped up in your ‘gemba walks’ (searching for speed losses), you not only solve that detail.
Much more: you are eliminating the chance of other problems that will occur when this detail comes in conjunction with some other details, leading to a potentially bigger problem.
7. The learnings:
- Do not spend too much time on trying to detect each and every minor stop.
- Detecting that Minor Stops are present is enough. This should be the signal to go at the machine and LOOK, observe, feel and hear.
- Any irregularity you observe is an indicator for process disturbances and should be eliminated.
- Start picking the majority of minor stops as low hanging fruits by applying plain standardization of those process topics that seem to have irregular behavior.
16. What is the difference between Name Plate Capacity and Maximum Speed?
Q: I am having a problem changing the Name Plate capacity (NPC) on one of my lines. The line in the past was 3.153pcs/min and now needs to be changed to 2.685pcs/min. When I change the Name Plate Capacity of the Machine settings to the new value and enter the Production for the line I still get the 3.153pcs/min. Should I not use the new, lower settings now?
Arno Koch • It is not the Name Plate Capacity (NPC) that determines the OEE but the ‘Standard’, which is the theoretical maximum speed of a certain product(group) on that equipment.
Name Plate capacity versus the Standard
The NPC is used to calculate the OEE Top value; meaning the OEE regardless differences in product.
The Standard (=Standard Cycle Time, Ideal Cycle Time) is the Theoretical Maximum Speed of a specific product on a certain machine. (Read more here)
So what you are probably looking for is to change ‘the Standard’, the maximum speed of a product on a machine.
When change the Name Plate Capacity or Maximum Speed?
1. When the machine or product have been changed
If the machine or the product was modified, leading to a higher speed, the value should be changed. From that moment on, the next calculations will use the new speed, older calculations will use the old speed.
2. The speed was set wrong form the beginning
In cases where the maximum speed was wrongly defined from the beginning, all calculations need to be recalculated retrospective, to correct this error.
OEE Coach software has a feature that allows you to do this all at once.
Why to lower the maximum speed?
My question here would be; Why would you lower your maximum speed? To raise the OEE? Having a too high maximum speed can’t harm. Your OEE will be a bit lower; so what. Important is that your operators keep looking for losses and thus potential improvement.
Setting the maximum speed definition lower than theoretical possible speed means there will be a day you go over it; thus having a performance rate over 100%. Of course that is ‘impossible’, meaning at that point you will have to change the speed again…
The shame of a high OEE
My advise; in case of doubt ALWAYS set speed higher than whatever you think is possible, NEVER build in hidden losses by lowering the maximum speed. It is not a shame to have an OEE that is not 85% because it will lead you to improvement.
It is a shame having a high OEE while the machine is running far below real maximum capacity and nobody is looking for improvement because the number says it is ok….!
There are no excuses for not being perfect.
There are only causes to be removed!
17. What is the use of the Name Plate Capacity (NPC)?
Q: What is the use of the Name Plate Capacity (NPC)? When defining OEE, you tell us we have to define the maximum speed per product per machine (the ‘Standard’).
Arno Koch • The NPC (Name Plate Capacity or Design Speed of the machine) is what the manufacturer of the equipment defined to be its maximum speed. Usually it is defined at a specified situation and a specified product.
There is only ONE Name Plate Capacity (NPC). The NPC nevertheless is usually not equal to the theoretical maximum speed of the machine.
Suppliers take safety margin
If the supplier reports the machine can run at maximum 100 strokes, it is not unusual to discover it can run at 110 or more. Obviously suppliers take a certain margin. Liability or covering deviations between machines is probably the reason.
Adjust Name Plate Capacity when needed
Do not be afraid to adjust your NPC to this higher level. Even if you are not going to run the machine at this speed. In this way you prevent the performance rate ever to go over 100%. In this way you make visible there is a hidden potential in this machine which later might be approached as a chronic loss.
The Ideal Situation versus Reality
In the ideal situation, the Maximum Speed for all your products would be the same as the NPC. The product-mix you are running on a machine determines whether this is true. You bought an expensive machine, because it has a NPC of 480 Mtrs/min. But it is running products that can not go over 240 mtr/min. In that case you might as well have bought a cheaper machine with a maximum capacity (NPC) of 240 mtr/min. Or maybe you might decide to run this products on another, lower capacity machine.
In real live, different product are being produced in different situations.
Different products, different speed
Imagine a machine that has a NPC of 60 strokes per minute. Thin product A can be cut in one stroke. The standard (maximum speed) for this product A on this machine would be 60 products per minute.
The standard is the theoretical maximum speed per product(group) on a machine
The thicker product B be can be cut in two strokes. This means the standard for product B on this machine is 30 products per minute.
So running 60 product A per minute means a performance rate of 100% while running 30 products B also results in 100% performance.
The difference between NPC and Maximum Speed
The NPC is the maximum speed of the machine. Not taking into account possible limitations for a product on that machine. I.e. a cutting machine might be able to cut 4 plies of 80 grams paper at a speed of 150 mtr/min, but only 2 plies of 120 grams paper. ‘The standard‘ is the maximum speed for a certain product on a certain machine. For printing and laminating equipment, it is not unusual to have different speeds for different foils (i.e. paper, aluminium or PE foil) and even for different thickness of foils. The NPC is then determined by the rotation speed of the engine, and the standard by i.e. the strength of the foil.
To make the difference visible between the effectiveness based upon NPC versus effectiveness based upon the maximum speed per product, the OEE-Top value is being used.
In the OEE, the performance rate is calculated based upon the Standard (maximum speed per product). In the OEE-Top, every product’s performance is calculated against the NPC. If you see large and frequent differences in OEE and OEE Top, this might be an indicator for reviewing the allocation of your product-mix.
Name Plate Capacity should be the highest possible speed
The NPC should be the highest possible speed for this machine (thus standards never can be higher!). Nevertheless one should consider carefully if this is really true. Don’t feel surprised when you sit besides the machine with a stopwatch and it turns out to be faster than NPC…
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