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6/3/2014 IENG 471 Facilities Planning 1 IENG Lecture Schedule Design: The Sequels Sequel

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6/3/2014IENG 471 Facilities Planning 2 Agenda Assignments Schedule Design – Part 3: Operator/Machine Assignments Ideal Assignment Total Cycle Time Operation Times Operator Idle Time Machine Idle Time Estimating Cost per Unit Questions & Issues

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6/3/2014IENG 471 Facilities Planning 3 Assignments Current Assignment: HW:(HW 3) See Assignment Link required input for each of the workstations equipment necessary for each machine steady state cycle time for each machine ideal machine assignment for each machine compute the idle time unit cost at each workstation total cost per good unit square footage for each workstation and the total space required We will use class time next period to work this problem So sit with the people that you want to work with on this assignment!

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6/3/2014IENG 471 Facilities Planning 4 Ex: Injection Mold Rubber Feet We obtain one set of feet per cycle Machine time is 35 s (steady state) after the operator starts the process At the start of each cycle, the operator will spend 5 s unloading moldings from the machine and spraying release agent on the mold halves before starting a machine cycle During automatic injection cycle, operator trims feet (15 s) and feeds re-grind & virgin material into machine hopper (10 s)

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6/3/2014IENG 471 Facilities Planning 5 Ideal Machine Assignment Neglects idle time: Where: a = concurrent activity time (both op & mach tied up) b = independent operator activity time t = independent machine activity time

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6/3/2014IENG 471 Facilities Planning 6 Cycle Time: Cycle time ( T c ): Where: a = concurrent activity time (both op & mach tied up) b = independent operator activity time t = independent machine activity time m = number of identical machines assigned to op. n = ideal number of identical machines assigned to op.

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6/3/2014IENG 471 Facilities Planning 7 Idle Machine Time: Idle time for machine ( I m ): Where: a = concurrent activity time (both op & mach tied up) b = independent operator activity time t = independent machine activity time m = number of identical machines assigned to op. n = ideal number of identical machines assigned to op.

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6/3/2014IENG 471 Facilities Planning 8 Idle Operator Time: Idle time for operator ( I o ): Where: a = concurrent activity time (both op & mach tied up) b = independent operator activity time t = independent machine activity time m = number of identical machines assigned to op. n = ideal number of identical machines assigned to op.

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6/3/2014IENG 471 Facilities Planning 9 Total Cost per Unit: Based on assigning m machines per operator, total cost ( TC(m) ) is: Where: C o = cost per operator-hour C m = cost per machine-hour a = concurrent activity time (both operator & machine tied up) b = independent operator activity time t = independent machine activity time m = number of identical machines assigned to operator n = ideal number of identical machines assigned to operator Add this to the material cost total from the BOM!

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6/3/2014IENG 471 Facilities Planning 10 Idle & Costing Example (cont.) Assume t = 35s Case A: Operator is assigned 1 machine Case B: Operator is assigned 2 machines Case C: Operator is assigned 1.3 machines

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6/3/2014IENG 471 Facilities Planning 11 Example: Ideal Machine Assign. Neglecting idle time: Where: a = 5s (load/unload) b = 15s (trimming) + 10s (feeding) = 25s t = 40s (cycle time) – 5s (load/unload) = 35s

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6/3/2014IENG 471 Facilities Planning 12 Cycle Time: 1 Machine/Operator Cycle time ( T c ): Where: a = 5s b = 25s t = 35s m = 1 n = 1.3 M#1

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6/3/2014IENG 471 Facilities Planning 13 Cycle Time: 2 Machines/Operator Cycle time ( T c ): Where: a = 5s b = 25s t = 35s m = 2 n = 1.3 M#2 M#1

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6/3/2014IENG 471 Facilities Planning 14 Cycle Time: 1.3 Machines/Operator Cycle time ( T c ): Where: a = 5s b = 25s t = 35s m = 1.3 n = machines 3 operators M#3 M#1 = 1.3

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6/3/2014IENG 471 Facilities Planning 15 Idle Machine Time: 1 Mach/Op Idle time for machine ( I m ): Where: a = 5s b = 25s t = 35s m = 1 n = 1.3 M#1 Im faster than one machine, so the machine is always busy!

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6/3/2014IENG 471 Facilities Planning 16 Idle Machine Time: 2 Mach/Op Idle time for machine ( I m ): Where: a = 5s b = 25s t = 35s m = 2 n = 1.3 M#2 M#1 Im slower than two machines, so now Im always busy!

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6/3/2014IENG 471 Facilities Planning 17 Idle Machine Time: 1.3 Mach/Op Idle time for machine ( I m ): Where: a = 5s b = 25s t = 35s m = 1 n = machines 3 operators M#3 M#1 = of us are just as fast as 4 machines, so everything is always busy!

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6/3/2014IENG 471 Facilities Planning 18 Idle & Costing Example (cont.) Assume the Following Costs: Operator Wage = $15/hr Operator Overhead = 40% Electricity Cost/Machine = $6/hr Maintenance Cost/Machine = $1/hr Computing the Cost per Unit Components: C o = Cost per Operator-Hour: $15/hr + (.40)($15/hr) = $21/hr C m = Cost per Machine-Hour: $6/hr + $1/hr = $7/hr

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6/3/2014IENG 471 Facilities Planning 19 Total Cost per Unit: Based on assigning 1 machine per operator: Where: C o = cost per operator-hour C m = cost per machine-hour

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6/3/2014IENG 471 Facilities Planning 20 Total Cost per Unit: Based on assigning 2 machines per operator: Where: C o = cost per operator-hour C m = cost per machine-hour

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6/3/2014IENG 471 Facilities Planning 21 Total Cost per Unit: Based on assigning 1.3 machines per operator: Where: C o = cost per operator-hour C m = cost per machine-hour

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