How to Start Measuring OEE and Define What and Where Are Your Problems?
How to start measuring OEE and what you can do with these numbers to improve the output of your line.
I do refer to my article What can OEE do for you (1) in which I explained what OEE means and why, when you want to increase your margin, it makes more sense to try to improve OEE than make savings on a cost items. Please note, that the abbreviation OEE stands for OVERALL EQUIPMENT EFFECTIVENESS.
Please take the word OVERALL literally. If you embark on the trip to get to the best level OEE, it will affect Everything in your company. It is a process that not only involves Production, also engineering and maintenance, also sourcing, also Personal, also administration also Management. No-one can say that it will not affect his job or how that job is done. Doing it only partially will deliver in the end only a partial result. Getting over 80% OEE will require efforts form everyone.
Once Management supports this, and is aware it will also affect het, go ahead on this Rat Race.
Step 1: Where do we stand.
OEE means to measure what you produce in relation what could be produced. Simple: Your oven can produce 500 Kg/hour. You run the line 48 hours. In those 48 hours you could produce 48 * 500 = 24 tons. Now check how much was effectively produced (number of pallets delivered by the product weight on each pallet). If that is 13 tons, your OEE is 13/24 = 0.729 or 54%. Mid-range.
Make sure that in the calculation you use the full planned production time.
Step 2: Where did the difference (11 tons) of biscuits go?
To start we need a first impression. There are several measuring points that will give information. First look at the process
- Have there been interruptions in the delivery of dough to the molding / oven?
- Were there interruptions in lifting the scrap dough or
- Was the cutting insufficient and were products lifted together with the scrap dough
- Were there problems at the rotary molder.
After the oven there are many things that can go wrong.
- Losing the proper laning in the turns of the cooling belt
- Due to this, incorrect guiding of biscuits at the dribble board resulting in overloading some lanes while others are starved
- Overloaded lanes may lead to popping up of products in such lanes
- Starving lanes may cause gaps in the feeding or stop such lanes
- Too fast cooling or excessive pressure in the vibratory chutes may lead to cracks in the products. That may lead to breaking of the biscuits in the feeding process leading to loss of products, what again leads to underweight packages being ejected at the check weigher
- In the wrapper there can be issues like
- unproper tracking of the film leading to open packs
- In slug packing, broken biscuits falling over and ending up in the end seal causing bad seal or no cut resulting in a twin pack
- Packs have been rejected by the packaging machine.
Check which data are available such as
- Good- and over- and underweight packs (data are on the check weigher)
- Ejected packs on the wrapper due to splices in the film or double packs or due to
- Incorrect position of the registered print on the pack (most wrappers do have that data
If you have such data, please see to what extend you can calculate quality losses
Check the oven speed for differences with the original specification. That will result in performance losses. Please make an estimate of the 3 different components of the OEE. This creates awareness.
Step 3: Observation
In order to be able to define what you see; knowledge of the line is required. It is advisable to have knowledge of the packaging system; otherwise wrong conclusion will be made. On the process side, you also must be knowledgeable to be able to find the causes for interruption or speed reduction. Take time to observe the line.
I prefer a higher position, where I can see the whole line. See if you find a position that allows you to observe the operators on the packaging line. Stay in that position for at least an hour and observe where the operators stand during production. Where they stand is an area of problems. Experienced operators stand close to the area with the most frequent problems. This allows them to act quickly and avoid losing time to have to go there.
This gives you a hint where the most urgent problems are
Step 4: Analysis
Now move to these locations and discuss with the operators what happens at that spot. Stay there until a jam or another problem occurs so you see yourself what is happening. Then ask the operator’s opinion. Let them tell you what they see as the problem. Let them make suggestions for improvement. It may be necessary to make a high-speed video to understand what is happening. Make your analysis of each pain point.
I have experienced that the operators correctly observe the problem. They may have reported this already and they may feel frustrated when nothing has been done.
I also experienced that they see that there is a problem but have no solution, or the suggested solution is not the right way to solve the issue. Still take their opinion and suggestions seriously.
Start at the end of the line and work backwards.
The following picture shows a simplified system with only 3 machines and some additional equipment. It is important to make a distinction between machine caused stops (jam, break down etc. of that machine) and being idle. A machine is idle when it is ready to work but receives no product from the machine up stream. Another stop is a forced stop. If machine 2 stops, machine 1 must stop too, while it cannot get rid of its products.
Observing Machine 1 you may see 70 stops. The first reaction could be that this machine is the problem. It cannot idle as it is the first in line and is not waiting for input (exception is that is does not receive products from the process)
Observing machine 2, again you will these 70 stops, but it is easy to define when it is idle as no product arrived from machine 1. (let’s assume 20 are due to idle)
If we observe machine 3, again you will the 70 stops, but now you can define that 30 of these stops are due to idle. This seems to point to 40 stops being caused by machine 3.
Now you must distinguish the stops caused by the Checkweigher (CW) and the Labeler positioned before machine 3. The checkweigher will eject over- and underweight packs (that leads to idling of machine 3). The labeler may incorrectly label packs. These may lead to jams at the infeed of machine 3. (idling)
Taking these aspects into account, it shows that machine 1 was forced to stops 50 of the 70 stops. These stops were not caused by machine 1. That leaves 20 stops are caused by machine 1. This is a different story from the 70 where we started.
Idle stops are easy to measure. Idling of a machine is most important at the last machine in a line. It will only work if all the upstream machines are working perfectly. Each error up stream will lead to a stop at machine 3
In order to be able to distinguish where there are problems at machine 1, we must assure that it runs as continuous as possible. Therefore, we must eliminate the forced stops by assuring that the downstream machines are working perfectly.
At the last machine, you can easily separate idle stops from other stops. Now analyze these stops and check carefully which are caused by the upstream equipment and which are caused by the machine itself. In this process the labeler can be a cause due to improper placement of the label.
Once you solve the issues at machine 3, the line will make only 30 stops. Now go to machine 2 and go over the same process as for machine 3.
Once that is solved, the analysis of machine 1 becomes simpler as the number of stops is down to 20. In a perfect world, machine 2 and 3 run uninterrupted, so any stop of machine 1 is caused by a problem in machine 1 itself.
You may have to use Ishikawa analysis method to find the root causes.
Analyze each defect considering the 6 causes, Machines, Man(power), Method, Material, , Measurement, as well as Environment. In each of these 6 arms you can mark sub causes. For Personal: lack of training material, lack of trained operators etc. The same for materials: incorrect packaging material, incorrect storage of packaging material causing deterioration. Methods may include badly prepared splices; wrong logistics leading to missing packaging material. Etc. etc.
Step 5: Action
Solve the issue you have selected. Involve the operators in the solution and make them feel that they have been important in finding the solution for the problem. Track the changes and see if you can detect the effect on the OEE by solving this issue. In the next articles I will describe these actions.
Step 6: Persistence
Now comes the most difficult part. Continue and stay with the steps that are outlined in the next articles. In them I describe also the small steps, and the controls. Make sure that you create a certain rhythm that you can keep up. Make sure to communicate with your personal on each problem and inform them what is done, what are the effects. See that you can communicate any improvement.
Once you have done your analysis, working your way from the end of the line upstream, you have an understanding where you lose production time and products.
It helps to classify these losses (next article)
It probably will be clear from the analysis you have done, that the problems have to do with a few basic aspects.
- The technical status of the machines and equipment. If a machine is not working properly, you cannot expect it to produce a good product or produce at full speed
- Understand, that the way your operators work with the machines may not be optimal, and in order to get the best result, everyone on the line must have the required level of knowledge.
- Procedures may not be optimal, so you have to define or develop procedures and systemize these in writing and train all personal in these procedures.
Finally, your operators must see the production line as THEIR Baby. When they feel proud of what they are doing, they get involved, they will cooperate to develop best practices and they will learn and apply what is developed. In total, this will result in higher volume, improved quality and more job security.
This is a management task. I cannot give rules, but I can advise to get everyone involved, to listen, and to invest in these teams. I am sure you will see a good return on your investment.
In the next article I will give tips how to define where to start and how to improve the performance with the methodology of 5S and TPM
Related articles:
What Can Do for You? What OEE means and why, when you want to increase your margin
Where to Start Mending: 5S and TPM - What Can OEE Do for You?
Where to Start With the Overall Equipment Effectiveness?
