3. Part X requires machining on a milling machine (operations A and B are requir
ID: 369421 • Letter: 3
Question
3. Part X requires machining on a milling machine (operations A and B are required) Find the number of machines required to produce 3000 parts per week. Assume the company will be operating 5 days per week, 18 hours per day. The following information is known: Efficiency 95% 95% Operation Standard Time 3 min 5 min Reliability 95% 90% Scrap 2% 5% Note: The milling machine requires tool changes and preventive maintenance after every lot of 500 parts. These changes require 30 minutes. 4. Part A is produced in machines 1 and 2. Part B is produced in machines 3 and 4. Part A and B are assembled in workstation 5 to create C. Assembly C is painted in process 6. Given the scrap percentages p1, p2, p3,..., p6, determine an equation that can be used to calculate the required input quantity to machine 1.Explanation / Answer
We have been given three parameters of an operation
1. Efficiency or Performance - Converting input into output
2. Reliability or Availability - How long an operation can run without issues
3. Scrap or Quality - What is the percent of waste
OEE or Overall Equipment Effectiveness equation connects all three parameters to give one single measure of total operation.
OEE = Performance*Availability*Quality
OEE for a set of operation can also be measured as OEE = Output of operation/Input of operation
For Operation A
Performance or Efficiency = 95%
Reliability = 95%
Quality = 98%
OEE = 0.95*0.95*0.98 = 88.44%...................................(1)
For Operation B
Performance = 95%
Reliability = 90%
Quality = 95%
OEE = 0.95*0.9*0.95 = 81.22%..............................(2)
For complete operation, OEE = 0.8844*0.8122 = 71.84%........................................(3)
To produce 3000 units, we must then process 4176 units
OEE = Output/Input
Input = Output/OEE = 3000/0.7184 = 4176 units.......................................................(4)
To process 4176 units, at total processing time of 8 (3+5) minutes, we would need = 4176*8 = 33408 minutes.....(5)
After processing of 500 units, scheduled down time of 30 minutes is taken.
Total minutes of downtime = 30*(4176/500) = 270 minutes................................(6)
Total time required = 33408+270 = 33678 minutes.
Total time available = 5 days*18 hoours per day * 60 minutes per hour = 5400 minutes
Total milling machines required = 33678/5400 ~= 7 machines
Q4) p1, p2, p3, p4, p5, p6 are scrap percentages
Total scrap percentage of the complete operation = p1*p2*p3*p4*p5*p6
Total efficiency of the operation = 1 - (p1*p2*p3*p4*p5*p6)
Total Efficiency = Output/Input
Input = Output/Total Efficiency
Input = Output/(1 - (p1*p2*p3*p4*p5*p6))
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