1. Chapter 6 Batching & Flow Interruptions Setup Times & EOQ

2. The Cost Minimizing Order Quantity
C(Q) Q

3. The Impact of Set-ups on Capacity
Production cycle
Batch of 12
Production cycle
Batch of 60
Batch of 120
Batch of 300
Time [minutes] 60
120
180
240
300
Produce steer supports (1 box holds 12 units = 12 scooters)
Set-up from ribs to steer support
Produce ribs (1 box holds 24 units = 12 scooters)
Set-up from steer support to ribs

4. Process Analysis with Batching
Capacity calculation changes: Note: Capacity increases with batch size…
… and so does inventory (and thus flow time)
Common in low volume manufacturing (including a lot of high-tech)
Also: transportation, education / training
Creates an inherent mismatch between demand and supply
Capacity
0.5
1/p
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
Batch Size 10 50 90
130
170
210
250
290
330
370
410
450
490
530
570
610
650

5. Batch Flow Operations Carry a Lot of Inventory
Production with large batches
Production with large batches
Production with large batches
Production with large batches
Production with small batches
Production with small batches
Production with small batches
Production with small batches
Cycle
Cycle
Cycle
Cycle
Cycle
Cycle
Cycle
Cycle
Inventory
Inventory
Inventory
Inventory
Inventory
Inventory
Inventory
Inventory
Produce Sedan
Produce Station wagon
Produce Sedan
Produce Sedan
Produce Sedan
ISedan
IWagon
Produce Station wagon
Produce Station wagon
Produce Station wagon
ISedan
IWagon
Beginning of
Beginning of
Beginning of
Beginning of
End of
End of
End of
End of
Beginning of
Beginning of
Beginning of
Beginning of
End of
End of
End of
End of
Month
Month
Month
Month
Month
Month
Month
Month
Month
Month
Month
Month
Month
Month
Month
Month
Movie theater vs. a room full of DVD players
SMED (Single minute exchange of die): reduce set-up times

6. 6.1 Metal window boxes are manufactured in two process steps: stamping and assembly. Each window box is made of 3 pieces: base A and two side Bs. These parts are fabricated by a stamping machine with a setup time of 2 hours whenever switching between the two part types. Once the machine is set up, the activity time for part A is one minute and for part B is 30 seconds. The current rotation is 360 As to 720 Bs. Completed parts move from stamping to assembly once a batch is complete. At assembly, one A, two Bs and some purchased parts are required per finished unit. Each product requires 27 minutes of labor to assemble; there are 12 workers in assembly; there is sufficient demand to sell every box produced.
What’s the capacity at stamping?
What should the batch size be?

7. 6.3 Consider the following batch-flow process consisting of 3 process steps performed by 3 machines. Work is processed in batches at each step. Before a batch is processed at a step, the machine must be set up during which it is unable to produce. Each machine has a dedicated setup operator.
What is the capacity of step 1 if the batch size is 35?
For what batch sizes is step 1 (2,3) the bottleneck?
Step 1
Step 2
Step 3
Activity Time
0.25 min/part
Setup Time 30 min
0.20 min/part
Setup Time 20 min
0.15 min/part
Setup Time 45 min