The main reasons for the impact of the overall efficiency of the equipment is the loss of downtime, loss of speed and loss of scrap. They are reflected by the time start rate, performance start rate and qualified rate, so get the following equipment integrated efficiency formula:
Equipment integrated efficiency = time start rate × performance start rate × qualified rate
Here, the load time for the specified operating time minus the daily downtime, that is
Load time = total working time -Scheduled downtime
The working time is the load time minus those unscheduled downtime, such as breakdown downtime, equipment adjustment and replacement of tools, fixtures downtime, etc.
Example 1 If the total working time is 8h, the pre-shift scheduled downtime is 20min, while the breakdown downtime is 20min, the installation of jigs and fixtures time is 20min, adjust the equipment time is 20min. so
Load time = 480-20 = 460min
Start time = 460-20-20 = 400min
Time start time = 460-20-20 = 400min
Time start time = 460-20-20 = 400min
Time start time = 460-20-20 = 400min
Time start time = 460-20-20 = 400min
Time start rate = speed start rate × net start rate
Here, the theoretical machining cycle is calculated according to the standard machining feed rate, and the actual machining cycle is generally longer than the theoretical machining cycle. The start time is the time that the equipment is actually used for processing, that is, the working time minus the planned shutdown and unplanned shutdown time, or load time minus unplanned shutdown time.
In fact
Calculatorically, the same result can be obtained with a simplified formula. The reason for using Speed Start Rate and Net Start Rate*** together to represent Performance Start Rate is that it is easier to see the cause of the loss of Performance Start Rate from the calculation process.
Example 2 there are 400 pieces of parts processing, theoretical machining cycle time is 0.5min, the actual machining cycle time is 0.8min. then
net start rate = 0.8 × 400/400 = 80%
speed start rate = 0.5/0.8 = 62.5%
performance start rate = 80% × 62.5% = 50%
(B) Planned downtime per day (production, maintenance schedules, morning meetings, etc.) = 20min.(C) Load time per day = A-B = 460min.
(D) Loss of downtime per day = 60min (of which breakdown shutdowns = 20min, setup preparations = 20min, adjustments = 20min ).
(E) Start-up time per day = C-D = 400min.
(F) Production quantity per day = 400 pieces.
(G) Pass rate = 98%.
(H) Theoretical cycle time = 0. 5min/piece.
(I) Actual cycle time = 0. 8min / piece.
(J) Actual machining time = I × F = 0. 8 × 400 = 320min.
(K) Time start rate = (E/C) × 100% = (400/460) × 100% = 87%.
(L) speed start rate = (H / I) × 100% = (0. 5 / 0.8) × 100% = 62.5%.
(M) Net opening rate = (J/E) × 100% = (320/400) × 100% = 80%.
(N) Performance start rate = L × M × 100% = 0. 625 × 0. 80 × 100% = 50%.
Finally, the
equipment efficiency (full efficiency) = K × N × G × 100% = 0.87 × 0.50 × 0.98 × 100% = 42.6%
Japan's full production and maintenance system, the requirements of the enterprise's equipment time start rate of not less than 90%, the performance of the start rate of not less than 95%, the rate of qualified products of not less than 99%, so that the equipment Comprehensive efficiency is not less than 85%. This is also the TPM requirements to achieve the goal.
As mentioned earlier, to improve the overall efficiency of the equipment mainly by reducing the six major losses.
Due to different sources, the translation of the English words in the comprehensive efficiency of equipment is not the same. In order to facilitate the reader to cross-reference, now give the above calculations appear in a variety of terms in the original English language.
Total working time -- total available time
Planned down time -- planned down time
Loading time --loading time
Working time -- operation time
Downtime -- down time
Time on rate -- availability
Performance on rate -- performance efficiency
Net operation rate -theoretical cycle time
Actual processing cycle time
Processed amount
Net operation rate
processed amount
Qualified products rate - rate of quality products
Equipment comprehensive efficiency - overall equipment efficiency (effectiveness)
The results of the calculation of the overall efficiency of equipment (OEE) can be used as a basis for the assessment of the level of equipment management. More importantly, the reason why it unfolds into the form of a complex product is to help us analyze the factors that affect the overall equipment efficiency, we can also combine the fishbone analysis to analyze the factors that affect the OEE, as shown in Figure 1-2.
Further, we can also use PM analysis to search deeper and find out the deeper causes that affect OEE, as shown in Figure 1-3. In the calculation shown in Figure 1-3, if the time-on rate is not high (partially boxed out), it means that the likely factor is equipment failure. Work mold replacement or adjustment downtime is too long, the test found to be a fault downtime is too long. Further analysis down the line revealed that it was neither the bearings nor the thrusters that were the cause, but a seal leak. Why did the seal leakage occur? Inspection results found to be due to the impact of damage to the cyclone.
So layer by layer down the analysis, until find out the answer can be solved. Reducing the six losses should pay attention to the following issues:
(1) Failure and short downtime is an obstacle, you should strengthen the inspection of the equipment, starting from small. For example, previously mentioned the Japanese Nishio pump factory has proposed: no one (chemical) management begins with no dust.
(2) Prevent equipment deterioration. Gryllotalpa, although small, can break the dike, equipment deterioration often starts from the dust. Dust adheres to the equipment, resulting in scratches, easy to corrode, gradually loosening, followed by vibration, which is the beginning of deterioration. In addition to routine tightening of screws, attention should be paid to preventive maintenance. Figure 1-4 illustrates the relationship between preventive maintenance and preventive medicine.
The top half of Figure 1-5 shows the equipment failure rate bathtub curve, and the bottom half shows the main causes of failure and treatment countermeasures at different times.
(3) Treatment countermeasures for zero failures. Failure is the peak of the iceberg, eliminating failures should start small. For example: ① strictly maintain the original basic state of the equipment (by cleaning, lubrication and tightening screws); ② comply with operating procedures; ③ timely eradication of deterioration; ④ improve the equipment design defects; ⑤ improve the operation and maintenance skills.
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Figure 1-3 Using PM analysis to find deep-rooted causes
Figure 1-4 Preventive maintenance vs. preventive medicine
Figure 1-5 Equipment failure rate bathtub curves and treatment countermeasures
Figure 1-6 describes the five categories of measures to control failures and prevent potential failures from progressing to functional failures and the related sectors.
Calculating the overall efficiency of equipment is not the goal; the goal is to clarify the sources of loss through the calculation and take countermeasures to improve equipment efficiency. The comprehensive efficiency of the equipment can also be used as an important indicator to measure and evaluate the level of equipment management.