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In this post we will present a simple method to calculate a truly weighted OEE, including weighted factors Availability, Performance, and Quality.
The QUICK weighted OEE method:
Recalling our original definition of OEE, we are measuring how effectively our planned production time (net available time) is used to make a quality (saleable) product. The weighted OEE then is the total time required to make a quality product divided by the total net available time.
From our examples in the “Calculating OEE” post, the following table summarizes the time required to produce quality products ONLY for machines A, B, and C:
Machine A: 365 minutes
Machine B: 318.75 minutes
Machine C: 254.34 minutes
The total time to produce good quality (saleable) products is 938.09 minutes.
The total net available time for the three machines is 1365 minutes (3 * 455 minutes).
The total weighted OEE for the 3 machines = 938.09 / 1365 = 68.72%
Calculating the Weighted Factors:
A similar process to the one described above can be applied to the individual factors. It stands to reason that when the individual factors are multiplied together that we should get the same result. We will use this to check our answer.
Availability measures machine uptime efficiency. The definition applied to an individual process also applies to the total of all the machines. Availability is calculated using the formula:
Availability: Net Operating Time / Net Available Time
From our examples in the “Calculating OEE” post, the following table summarizes the Net Operating Times for machines A, B, and C:
Machine A: 423 minutes
Machine B: 437 minutes
Machine C: 433 minutes
The total Net Operating Time = 1293 minutes.
The total Net Available Time for the three machines is 1365 minutes (3 * 455 minutes).
The weighted AVAILABILITY for the 3 machines = 1293 / 1365 = 94.73%
Performance measures machine operating time efficiency when compared to the “ideal” cycle or operating time. The definition applied to an individual process also applies to the total of all the machines. Performance is calculated using the formula:
Performance: Ideal Operating Time / Net Operating Time
From our examples in the “Calculating OEE” post, the following table summarizes the Ideal Operating Times for machines A, B, and C:
Machine A: 373.33 minutes
Machine B: 337.50 minutes
Machine C: 267.17 minutes
The total Ideal Operating Time to produce ALL parts = 978 minutes.
The total Net Operating Time for the three machines is 1293 minutes (See Availability Calculations Above).
The weighted PERFORMANCE for the 3 machines = 978 / 1293 = 75.64%
Quality measures how efficiently the “ideal” operating time is used to produce quality (saleable) products. Again, the definition applied to an individual process also applies to the total of all the machines. Quality is calculated using the formula:
Quality: Ideal Operating Time to Make Quality Parts / Ideal Operating Time
From our examples in the “Calculating OEE” post, the following table summarizes the Ideal Operating Time to produce Quality Parts ONLY for machines A, B, and C:
Machine A: 365.00 minutes
Machine B: 318.75 minutes
Machine C: 254.34 minutes
The total Ideal Operating Time for Good Parts = 938.09 minutes.
The total Ideal Operating Time to produce ALL parts for the three machines is 978 minutes (See Performance Calculations Above).
The weighted Quality for the 3 machines = 938.09 / 978.0 = 95.92%
Weighted OEE cross check:
Let’s compare the results. From the calculations above, the results are summarized as follows:
Weighted Availability: 94.73%
Weighted Performance: 75.64%
Weighted Quality: 95.92%
Now, we multiply the individual weighted OEE factors together:
OEE = 94.73% * 75.64% * 95.92% = 68.73%
You will see the result is the same as the Quick check introduced at the start of this post.
In our next post we will show you how to calculate the weighted factors for each individual process and introduce yet another way to confirm the weighted OEE calculation.
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We have received several inquiries regarding equipment down time – periods of time when the machine is not scheduled to run. We consider this to be scheduled down time or idle time and does not affect Overall Equipment Effectiveness (OEE), since no production was planned during this period.
OEE measures overall equipment effectiveness during planned production or SCHEDULED up time. Do not confuse idle time with tooling or material change over as these activities should be part of the scheduled machine time – periods where the machine is not scheduled to run. After hours or weekends are examples of idle time.
TEEP or Total Equipment Effectiveness Performance is another variable, similar to OEE, and measures the Total Equipment Effectiveness Performance based on calendar time – the total time the equipment is “present”. If process “A” is in your plant for 24 hours a day, 7 days a week, then the total time required to make good parts is divided by the time the asset, process, or equipment is “present” and is therefore “technically available” for the time frame being considered. Typically this is based on calendar time – 24 hours per day and 7 days per week.
Another way to view TEEP is to consider it as a measure of how effectively the total capacity of a process or machine is being utilized to make GOOD parts. In short, TEEP could be defined as a measure of Equipment Capacity Utilization Effectiveness.
TEEP Calculation Example:
In the metal stamping business, raw coil steel is processed through a die that runs in a stamping press to manufacture the parts. The ideal cycle time for may be 30 strokes (or parts) per minute. While the press may be scheduled to run for 16 hours, it is technically “present” or available 24 hours. If, in a given day, a total of 18,000 GOOD parts were produced over 16 hours of scheduled production time, the OEE is easily calculated.
We will first calculate the IDEAL hours required to produce 18,000 parts at 30 spm. The IDEAL rate per hour is 1,800 parts (30 spm * 60 minutes / hour). Therefore the IDEAL time to produce 18,000 good parts is 10 hours (18,000 parts / 1,800 per hour).
If this is a two shift operation, the net available time is 16 hours (scheduled) and the OEE for the day is calculated as 10 / 16 = 62.5 %.
Since the press is always present, 24 hours per day – 7 days per week, the Daily Equipment Effectiveness Performance (DEEP) in this case is 10 / 24 = 41.7 %. While this example only represents a single 24 hour day, the basis for calculation is the same. If the time frame is one week, one month, one quarter, the Total Equipment Effectiveness Performance for that time frame is calculated using the following formula:
TEEP = Total IDEAL Time to Produce Good Parts / Total Gross Time Available
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