A well-known expert in manufacturing systems and the founders of the Toyota Production System, Shigeo Shingo made a visit to a factory during the production
a banner in the field is objected. The banner “Eliminate Lost.” He writes.
In the first place, the factory management accompanying Shingo can not understand the reason for the objection, but Shingo explains why he objected afterwards. To eliminate losses primarily that tells them the right to know and the slogan “Get Lost.” Expresses that.
How do we find good losses? How big is our ice? Besides the problems we see, how much do we not see? Where are our problems?
In order to find answers to these questions, we must first correctly measure the effectiveness of our machines. The accuracy of the data we use for this is important. The accuracy of our data collection method is key to accurate measurement of effectiveness. As will be data collection method in the conventional manner with the form filling method has the technological infrastructure D C A S such systems can be used. Because measurements made with incorrect data do not lead us to the end.
” You have to know them first to remove the losses from the center. ”
D C A S : simultaneously allowing the production area is an integrated data collection and data collection system that can communicate with other ERP system.
OEE (Overall Equipment Effectiveness – Total Equipment Effectiveness) developed by Seiichi Nakajima, founder of TPM (Total Productive Maintenance) method in 1960,Is one of the most important performance indicators in Japan Management Systems focused on loss. OEE is a mathematical metric developed to measure and monitor machine positions, performances and quality losses with a single parameter. OEE shows us how well and efficiently we use our machines. This indicator can be followed for a single machine as well as for the line or section. OEE, which is clearly evident in the calculation method, is one of the most important indicators calculated all over the world and used for the same purpose. With this indicator,
Worldwide companies’ machine utilization performance is around 50% when measured by the OEE method. This means that you can not use the remaining 50% of your machines time.
With the KAIZEN work to reduce your losses, even raising the OEE rate to 60% will give you 20% capacity increase without spending any money.
The best OEE value that can be applied is accepted as 85% and these level companies are referred to as “World Class”manufacturing companies. Companies in the world standard will try to meet their capacity needs by increasing OEE performance. They thus protect themselves from additional investment, additional space usage, additional labor, excess inventory, excess energy use, poor quality and financing costs.
OEE aims to reduce by focusing on loss. It prioritizes the losses and ensures that they are made KAIZEN in the right places. The machine shows your performance, but the difference from 100% indicates which loss is based. The graph shows how the equipment losses that lower the OEE value are classified.
For the KAIZEN studies to be effective, the correct definition and understanding of the losses is very important. Shutdown loss TEEP ( Total Equipment Effectiveness Performance – Overall Equipment Effectiveness Performance ) when calculating are used. Seven major losses are clearly shown in the OEE charts, and as a result of the analyzes made, prioritization is done and KAIZEN studies are planned. Not all of these losses can be found in some business areas. For him to know what we need to know about our losses, right from the point of view of the right loss class. For example; Setup and set-up period, fill-up time and machine preparation times (warm-up)although it is not exactly removed, the minimum level is the targeted times. Because of this, the unplanned stopping should be accepted in the class and should be included in the OEE account in this way.
KAIZEN : In Japanese, Kai is the name of a continuous healing philosophy of ‘change’ and Zen: a combination of two lambs that means ‘better’.
How is OEE calculated?
The OEE account begins with defining the time that the production facility is open. This process is called “Calendar Time” . “Scheduled Production Time” is calculated by subtracting scheduled planned postings from the schedule during the calendar . The “Run Time” is calculated during the planned production period by taking unplanned stops that were not planned beforehand and which were experienced during production . In case of speed losses and small postures that affect production speed negatively and away from theoretical production speed during the period of working which is deemed to be actual production, “Net Working Time”calculated. “Effective Working Time” is calculated in the case where we subtract the expended time for products that are not produced correctly during the first time produced from the production made within the net working time .
OEE Calculation Period and Sharing Principles
It provides detailed information and timely intervention on how we use our machines to monitor OEE instantaneously. DCAS software and automation solutions can be used for instant monitoring and data analysis. However, if such solutions can not be used, manual calculation and follow-up periods can be defined. For periods, we can make shifts, days, weeks, months, and so on. The recommended and most used time frame is available, but the process and production requirements can also be tracked on a daily basis. Also, OEE can be calculated not only for a time slot but also for a work order. When we continuously monitor OEE value, it can determine KAIZEN issues for open areas to improve by looking at OEE value, working at every level from machine operators to senior managers. Also OEE value, is the best tool to track the success of your KAIZEN work. Even if software and automation solutions are used following the OEE values, we can understand at what level our OEE performance is,sharing with everyone with visual management tools , exhibiting them in easily visible places or providing information with periodical informants, OEE management is important.
OEE aims to maximize the effective working time.
Points to note when calculating OEE
Companies’ point of view on OEE account is very important. Because OEE accounts should be shaped and shaped according to each company’s own processes and cultural traditions. What we should not forget here is what we are … Our goal is to artificially raise the values and behave as if there are no problems, or should we make real improvements and developments by taking the problems and taking permanent measures to them?
The most dangerous type of loss is the type of loss we do not know or do not know about.
– Shigeo Shingo
In order to be aware of our losses, we want to draw your attention to some points that we should pay attention to.
We do not know the theoretical cycle speeds are very vital for OEE calculation. The OEE values continue to be high when we are experiencing a lot of losses in our machines if erroneous theoretical cycle rates are set.
Theoretical cycle speeds may vary between machine, mold and version.
If we can not measure the speed loss or if we can not keep a record of the small downtimes, we need the right theoretical cycle speed to calculate the net working time and the performance ratio. Because we calculate the performance rate at theoretical speed.
Various sampling and measurement methods can be used to accurately calculate the theoretical cycle time of the machine or line. When the machine is first picked up, the machine manufacturer or production, maintenance specialists determine the theoretical cycle time. However, this time
may have changed by factors such as machine and mold wear, machine age, cooling water temperature, changes you make and raw materials used . For this reason, the measurements that we will make the theoretical cycle time should be determined by taking the opinions of production and maintenance experts. Measurements can be taken either from the machine system or manually with the stopwatch. This measurement is based on product, machine, line,
, the theoretical cycle time can be calculated. When determining this value, care must be taken that the performance ratio does not exceed 100%.
All setups and adjustments we made due to the product range are considered lost in the OEE account. Because there is a preparatory activity to create value instead of an activity that creates value at that time. These activities can be considered as the reason why we consider the losses necessary for the production. However,
it should not be forgotten. At this point the SMED8 method is an important tool for the implementation of improvement activities. Although SMED’s theory is intended to reduce the setup times to less than 10 minutes, any activity that reduces setup times can be considered within this scope. Also, at the point where the SMED method interacts with the quality component,
KAIZEN studies should be carried out in the areas of initial product approval and serial production pass immediately after setup.
Some of the operations that need to be done within the planned production period may be out of this time period or the problems that are going on are shown in the planned stopping status. These impressions appear to be higher than they should be due to OEE values.
a factory that operates 2 shifts, the machine will be out of the time-scheduled production time used if the machine is being prepared for the new product in the 3rd shift or on a non-working weekend.
A plant with 10 machines is operating an 8 machine. If the other 2 machines are closed and one of the closed machines for the new product is being prepared, then the time allocated for this preparation will be outside the planned production period.
A planned production machine for 2nd shift may be broken during production and cut at half. The machine may be out of production due to the spare parts problem and may remain closed for a long time. In this case, it means that loss, planned posture, and loss of our losses by saying that maintenance is planned for the machine.
In some businesses and processes, some machines also work in meals and in the malls with employees working alternately. This is the opposite of what we have come up with to calculate our OEE value as if eating and stopping, and closing our losses.
Closure losses are not included in OEE accounts, even if they are seen as loss. There is nothing the field staff can do to eliminate these losses. For example;
We must pay attention to these cases in our calculations, as we have said at the beginning that we do not artificially raise OEE value and trick ourselves. The calculations made in this way lead to the following problems;
There is no error in OEE calculations as long as we store the actual causes in the database together with the time spent. Note that we will be sufficient for further analysis and calculations. A detailed and accurate examination of the losses is also possible with the correct classification and identification. If we make an incorrect or incomplete description, it will mislead us in the selection of KAIZEN topics.
Nothing is hard, let alone knowing it is a small piece.
– Henry FORD
Example-1: If the
mold failure rate is high, we must follow the definition of the breakdown of the machine separately from the description of the machine failure.
there is no stock in the factory and the planning closes the machine by informing you about the raw material, the time that the machine is closed and the machine is closed is not included in the OEE account. However, if there is an unannounced stop due to a stock fault, the time until the necessary organization (the time spent for the workforce to be evaluated elsewhere and to close the machine) must be included in the OEE account as an unplanned stoppage (empty waiting or replenishment).
If stock is in stock, is expected to be serviced, or is expected to be ready for raw material preparation, it should be included in the OEE account as unplanned downtime (replenishment and filling) and KAIZEN work should be done to shorten the replenishment period.
In some cases it is expected that care or housekeeping personnel will intervene accidentally. This time must be monitored separately from the repair time and recorded as unplanned stop (idle standby).
In the calculation of the quality component, the point to be noted is the correct production rate in the first pass. The time, workmanship, raw material we spend on products that we can not make the right production for the first time should be considered completely lost.
|Number of Production||480|
|Number of Scrap||30|
|Available to Sell as a Class 2 Product||33|
If we calculate the OEE quality component according to the above production information, as the correctly produced pieces in the first time;
= 480 – (30 + 20 + 33) = 397
OEE Quality components;
= (397/480) x 100 = 82.7%
HOW OEE IS EVALUATED?
The OEE value can mislead us when it is handled alone. For example, if we examine the following table;
|OEE Components||1. Machine||2. Machine|
When we look at only the OEE value, we see that the 1st machine is more successful, but when we look at the quality ratio, we see that there is a 3 point deterioration. The better the OEE, the greater the availability. For this reason, it is not enough to look at the OEE value by itself, we should examine the losses in detail. It would be misleading to put OEE as a single value for a plant with many different machine parks and processes. Instead, it is a more accurate guideline to follow the OEE’s of departments that have the same-like type of machinery and equipment.
The OEE of a machine park can be created by the following methods.
You can get the arithmetic average of your OEE values.
You can use the weighted average of your machines.
You can accept your OEE values as the OEE value of the plant that has the remaining value after the order
It should not be forgotten that OEE value is a production indicator. OEE value does not indicate the efficiency of employees, but
focuses only on the effectiveness of machinery or equipment . OEE value should not be used as a means of indictment. When used, employees can enter the psychology of defending themselves and defending their losses.
How should OEE be improved?
The value for the OEE value is considered to be a high performance of 85%, according to the investigations and expert opinions, although it is wrong to say the following or that. However, this value may vary due to sectoral differences.