IQE OFFERINGS
| 8 Metrics of Process Performance | Takt Time | First Time Quality | Overall Equipment Efficiency |
This section includes offerings from IQE to assist any organization on the journey to World Class status.
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8 Metrics of Process Performance
|
Process Cp, Cpk |
% of |
Process +/-Sigma |
Yield % |
Defect % |
1 Defect in Every "n" Parts |
Defective |
Probobility of Exceeding Eng'g. Limits |
| 0.33 | 303 | 1 | 67.77 | 32.23 | 1.1 | 880,669 | 44.03 |
| 0.67 | 149 | 2 | 95.56 | 4.44 | 22 | 45,455 | 2,221 |
| 1.00 | 100 | 3 | 99.73 | 0.27 | 370 | 2,700 | 0.1349 |
| 1.33 | 75 | 4 | 99.993 | 0.006 | 15,152 | 66 | 0.0033 |
| 1.67 | 60 | 5 | 99.99995 | 0.00005 | 2,000,000 | 0.05 | 0.000027 |
| 2.00 | 50 | 6 | 99.9999998 | 0.0000002 | 500,000,000 | 0.002 | 0.000000098 |
ALL RIGHTS RESERVED IQE, c. IQE 1994. This information is provided for personal use only and may not be copied, distributed or sold. Contact IQE if interested in the IQE reference series.
TAKT Time is a measure of the desired or target process cycle time and is defined as Total Operating time available (in seconds) divided by the total units scheduled to be produces daily.
First Time Quality is the % first time pass rate, or yield through each operation of the defined chain of operations. Data will include both PROCESS and PRODUCT failures at each operation. Any scrap, rework, or sorting must be included in the calculation. P charts, Pareto Charts, etc. are needed to define opportunities for improvement. Example: The following example is for 1 shift with the bottom of the table showing how to calculate the Combined FTQ for all shifts.
| Total of the Process Rejects = | 122 |
| Total of the Product Rejects = | 44 |
| Total Rejects = | 166 |
| Process Input = | 800 |
| Process Input Minus Total Rejects = 800-166 = | 634 |
| (Input-Rejects)/Input = (800-166)/800 = | .79 |
| First Time Quality = .79 x 100 = | 79% |
| NOTE: Combined FTQ = ((Input All Shifts- Rejects All Shifts)/Input All Shifts)x 100 |
Overall Equipment Efficiency (OEE)
Overall Operating Efficiency, also known as OEE or AQP, is a comprehensive measure expressed as a percentage that takes into account Process Availiability, Through Put Performance and Product Quality. It is determined using the following formula: Availability (A) x Quality (Q) x Performance (P) x 100 = %. An initial target is 85% or better for the total plant.
Availability (A) = (available time - downtime)/available time. Available time is the shift time less break time, downtime is time for change overs, machine downtime, and unplanned downtime.
Quality (Q) = (number of parts produced - number of defects)/number of parts produced.
Performance (P) = (MCT x number of parts produced)/operating time. MCT is the theoretical mean cycle time or the machine's calculated cycle time. Operating time is the time the machine was actually running and producing parts.
"If you can improve it today, there's no excuse for waiting until tomorrow..."
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Last updated on 05/16/97
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