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IENG 471 - Lecture 04 - 3

Learn to optimize workstations by assigning ideal machines, calculating idle time, cost per unit, and space requirements. Collaborate in class for hands-on experience.

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IENG 471 - Lecture 04 - 3

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  1. IENG 471 - Lecture 04 - 3 Schedule Design: The Sequel’s Sequel IENG 471 Facilities Planning

  2. 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! IENG 471 Facilities Planning

  3. 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) IENG 471 Facilities Planning

  4. 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 IENG 471 Facilities Planning

  5. Cycle Time: • Cycle time (Tc): • 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. IENG 471 Facilities Planning

  6. Idle Machine Time: • Idle time for machine (Im): • 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. IENG 471 Facilities Planning

  7. Idle Operator Time: • Idle time for operator (Io): • 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. IENG 471 Facilities Planning

  8. Total Cost per Unit: • Based on assigning m machines per operator, total cost (TC(m)) is: • Where: • Co = cost per operator-hour • Cm = 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! IENG 471 Facilities Planning

  9. 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 IENG 471 Facilities Planning

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

  11. Cycle Time: 1 Machine/Operator • Cycle time (Tc): • Where: • a = 5s • b = 25s • t = 35s • m = 1 • n’ = 1.3 M#1 IENG 471 Facilities Planning

  12. Cycle Time: 2 Machines/Operator • Cycle time (Tc): • Where: • a = 5s • b = 25s • t = 35s • m = 2 • n’ = 1.3 M#1 M#2 IENG 471 Facilities Planning

  13. Cycle Time: 1.3 Machines/Operator • Cycle time (Tc): • Where: • a = 5s • b = 25s • t = 35s • m = 1.3 • n’ = 1.3 4 machines 3 operators = 1.3 M#1 M#2 M#4 M#3 IENG 471 Facilities Planning

  14. Idle Machine Time: 1 Mach/Op • Idle time for machine (Im): • Where: • a = 5s • b = 25s • t = 35s • m = 1 • n’ = 1.3 I’m faster than one machine, so the machine is always busy! M#1 M#1 IENG 471 Facilities Planning

  15. Idle Machine Time: 2 Mach/Op • Idle time for machine (Im): • Where: • a = 5s • b = 25s • t = 35s • m = 2 • n’ = 1.3 M#1 I’m slower than two machines, so now I’m always busy! M#2 IENG 471 Facilities Planning

  16. Idle Machine Time: 1.3 Mach/Op • Idle time for machine (Im): • Where: • a = 5s • b = 25s • t = 35s • m = 1 • n’ = 1.3 4 machines 3 operators = 1.3 M#1 M#2 M#4 M#3 3 of us are just as fast as 4 machines, so everything is always busy! IENG 471 Facilities Planning

  17. 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: • Co = Cost per Operator-Hour: $15/hr + (.40)($15/hr) = $21/hr • Cm = Cost per Machine-Hour: $6/hr + $1/hr = $7/hr IENG 471 Facilities Planning

  18. Total Cost per Unit: • Based on assigning 1 machine per operator: • Where: • Co = cost per operator-hour • Cm = cost per machine-hour IENG 471 Facilities Planning

  19. Total Cost per Unit: • Based on assigning 2 machines per operator: • Where: • Co = cost per operator-hour • Cm = cost per machine-hour IENG 471 Facilities Planning

  20. Total Cost per Unit: • Based on assigning 1.3 machines per operator: • Where: • Co = cost per operator-hour • Cm = cost per machine-hour IENG 471 Facilities Planning

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