IENG 471 - Lecture 04 - 3

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IENG 471 - Lecture 04 - 3

• Schedule Design
• The Sequels Sequel

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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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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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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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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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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.

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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.

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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.

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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!
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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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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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Cycle Time 1 Machine/Operator

• Cycle time (Tc)
• Where
• a 5s
• b 25s
• t 35s
• m 1
• n 1.3

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Cycle Time 2 Machines/Operator

• Cycle time (Tc)
• Where
• a 5s
• b 25s
• t 35s
• m 2
• n 1.3

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Cycle Time 1.3 Machines/Operator

• Cycle time (Tc)
• Where
• a 5s
• b 25s
• t 35s
• m 1.3
• n 1.3

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Idle Machine Time 1 Mach/Op

• Idle time for machine (Im)
• Where
• a 5s
• b 25s
• t 35s
• m 1
• n 1.3

Im faster than one machine, so the machine is
always busy!
M1
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Idle Machine Time 2 Mach/Op

• Idle time for machine (Im)
• Where
• a 5s
• b 25s
• t 35s
• m 2
• n 1.3

Im slower than two machines, so now Im always
busy!
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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
M1
M2
M4
M3
3 of us are just as fast as 4 machines, so
everything is always busy!
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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

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Total Cost per Unit

• Based on assigning 1 machine per operator
• Where
• Co cost per operator-hour
• Cm cost per machine-hour

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Total Cost per Unit

• Based on assigning 2 machines per operator
• Where
• Co cost per operator-hour
• Cm cost per machine-hour

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Total Cost per Unit

• Based on assigning 1.3 machines per operator
• Where
• Co cost per operator-hour
• Cm cost per machine-hour