STONEHAVEN
STONEHAVEN
STONEHAVEN
1.0 What are the daily capacities and ManufacturingLead Time of Cutting Stitching and LastingLead Time of Cutting, Stitching and LastingDepartment considering a
100 i b t h100 pair batch10 pair batch?
CUTTING DEPARTMENT
100 pair batchCapacity, CT and MLT
CUTTING DEPARTMENT
Cutting Shoe leather4* (5 25 + 100*0 05) = 41
100 pair batch4 (5.25 + 100 0.05) 41
minutes
LeatherSheets
Cut Linings4* (5.00 + 100*0.05) = 40
minutes
Cut insole4* (4 00 100*0 04) 324* (4.00 + 100*0.04) = 32
minutes
There are three parallel operations each of which cuts 100 of four different ShoeThere are three parallel operations, each of which cuts 100 of four different Shoecomponents (creating 1200 pieces in 100 pair batch), each of which requiresFour die changes
CUTTING DEPARTMENT
Cutting Shoe leather4* (5 25 + 100*0 05) = 41
100 pair batch4 (5.25 + 100 0.05) 41
minutes
LeatherSheets
Cut Linings4* (5.00 + 100*0.05) = 40
minutes
Cut insole4* (4 00 100*0 04) 324* (4.00 + 100*0.04) = 32
minutes
Capacity = 480/41 = 11 7 batches = 1170 pairs of shoe per shiftCapacity 480/41 11.7 batches 1170 pairs of shoe per shiftMLT = 41 minutes. Cycle time = 41 minutes
CUTTING DEPARTMENT
10 pair batchCapacity, CT and MLT
CUTTING DEPARTMENT
Cutting Shoe leather4* (5 25 + 10 * 0 05) =
10 pair batch4 (5.25 + 10 0.05)
23 minutes
LeatherSheets
Cut Linings4* (5.00 + 10 * 0.05) = 22
minutes
Cut insole4* (4 00 10 * 0 04)4* (4.00 + 10 * 0.04) =
17.6 minutes
Capacity = 480/23 = 20 9 batches = 209 pairs of shoe per shiftCapacity 480/23 20.9 batches 209 pairs of shoe per shiftMLT = 23 minutes. Cycle Time = 23 minutes
CUTTING DEPARTMENT
While changing from a 100 pair batch to a 10 pairbatch the MLT declines 44 % but the capacitybatch, the MLT declines 44 %, but the capacitydeclines a whooping 82 % - function of the setups,which are relatively long compared to the run times?y g p
STITCHING DEPARTMENT
STITCHING DEPARTMENT
Despite the strange back and forth flow of baskets toand from workers and supervisors in stitching this isand from workers and supervisors in stitching, this isa classic worker-paced line, with operations insequence.q
STITCHING DEPARTMENT
100 pair batchCapacity, CT and MLT
STITCHING DEPARTMENT
100 pair batch
Joining3 k
Prefit4 k
Ornament2 k3 workers4 workers 2 workers
5 minTime/pair 2.5 min3 min
Task Time 500 mins 300 mins 250 mins
Operation 500/4= 300/3= 250/2=Operation 500/4= 300/3= 250/2=Cycle Time 125 mins 100 mins 125 mins
STITCHING DEPARTMENT
100 pair batch
Joining3 workers
Prefit4 workers
Ornament2 workers
Task Time 500 mins 300 mins 250 mins
Operation 500/4 300/3 250/2Cycle Time 125 mins 100 mins 125 mins
Cycle Time for the department is 125 minutesThe Capacity is 480 / 125 = 3.84 batches = 384 shoes per shiftp y p
STITCHING DEPARTMENT
100 pair batch
What is the Manufacturing Lead Time?
STITCHING DEPARTMENT
100 pair batch
What is the Manufacturing Lead Time?
Use Little’s Law
Little’s LawManufacturing Lead Time = Work in Process * Cycle Time
STITCHING DEPARTMENT
100 pair batch
Joining3 workers
Prefit4 workers
Ornament2 workers
Task Time 500 mins 300 mins 250 mins
Operation 500/4 300/3 250/2Cycle Time 125 mins 100 mins 125 mins
Manufacturing Lead Time: Easy way is to use Little’s LawWIP = 9 workers each with 2 batches (one in process and one as buffer) = 18 batches( p )
MLT = 18 batches * 125 mins = 2250 minutes
STITCHING DEPARTMENT
10 pair batch
10 pair batchCapacity, CT and MLT
STITCHING DEPARTMENT
10 pair batch
Joining3 workers
Prefit4 workers
Ornament2 workers
Task Time 50 mins 30 mins 25 mins
Operation 50/4 30/3 25/2Cycle Time 12.5 mins 10 mins 12.5 mins
Cycle Time for the department is 12.5 minutesThe Capacity is 480 / 12.5 = 38.4 batches = 384 shoes per shiftp y p
STITCHING DEPARTMENT
10 pair batch
Joining3 workers
Prefit4 workers
Ornament2 workers
Task Time 50 mins 30 mins 25 mins
Operation 50/4 30/3 25/2Cycle Time 12.5 mins 10 mins 12.5 mins
Manufacturing Lead Time: Easy way is to use Little’s LawWIP = 9 workers with 2 batches (one being worked on and one as buffer) = 18 batches( g )
MLT = 18 batches * 12.5 mins = 225 minutes
STITCHING DEPARTMENT
With batches of ten pairs, cycle time drops to 12.5minutes and the capacity remains unchanged at 384minutes, and the capacity remains unchanged at 384pairs of shoes.A lt f t i d f b t hAs a result of no setups required for a new batch,the capacity remains unchanged when batch sizesare reduced However a 90% reduction in batch sizeare reduced. However a 90% reduction in batch sizeleads to a 90% cut in MLT
LASTING DEPARTMENT
LASTING DEPARTMENT
100 pair batchCapacity and MLT
LASTING DEPARTMENT
100 pair batch
Rough Sole1.0 mins
Staple Sole0.7 mins
Seat Lasts0.6 mins
Cement Sole
0 9 mins
Inspect & Pack
0 3 mins0.9 mins 0.3 mins
Cycle Time is one minute per pair, driven by the Bottleneck “Rough Sole”y p p y gThe conveyor belt must be paced at one minute per operation.
First pair comes out at 5 minutes ( 1 min each for the 5 operations)The second pair comes off the line at 6 minutes, the third at 7 mins (“cycle time”)((n + 4) mins, where n = batch number)
Th th MLT f th b t h f 100 i i 104 i t (100 + 4)Thus the MLT for the batch of 100 pairs is 104 minutes (100 + 4)With one batch allowed at one time, the Capacity is 480 / 104=4.62 batches=462 shoes
LASTING DEPARTMENT
10 pair batchCapacity CT and MLTCapacity, CT and MLT
LASTING DEPARTMENT
10 pair batch
Rough Sole1.0 mins
Staple Sole0.7 mins
Seat Lasts0.6 mins
Cement Sole
0 9 mins
Inspect & Pack
0 3 mins0.9 mins 0.3 mins
Cycle Time is one minute per pair, driven by the Bottleneck “Rough Sole”y p p y gThe conveyor belt must be paced at one minute per operation.
First pair comes out at 5 minutes ( 1 min each for the 5 operations)The second pair comes off the line at 6 minutes, the third at 7 mins (“cycle time”)((n + 4) mins, where n = batch number)
Th th MLT f th b t h f 10 i i 14 i t (10 + 4)Thus the MLT for the batch of 10 pairs is 14 minutes (10 + 4)With one batch allowed at one time, the Capacity is 480 / 14=34.3 batches=343 shoes
LASTING DEPARTMENT
Effect of the of policy of allowing only one batch in the Department
Rough Sole1.0 mins
Staple Sole0.7 mins
Seat Lasts0.6 mins
Cement Sole
0 9 mins
Inspect & Pack
0 3 mins0.9 mins 0.3 mins
Since one batch is allowed at one time, there will be a time at the end of the batch when the beginning of the operations in the conveyor are idle.
LASTING DEPARTMENT
Rough SoleStaple Sole Seat Last Cement Sole
Inspect & Pack
100 99 98 97 96
Minute by Minute snapshot of the Shoe Assembly line from T=99 to 103
Rough Sole1.0 mins
Staple SoleIDLE
Seat Lasts Cement Sole
Inspect & Pack
Sole Pack0
100 99 98 97
Rough Sole1.0 mins
Staple SoleIDLE
Seat LastsIDLE
Cement Sole
Inspect & Pack
100 99 98.0 s So e ac
Rough SoleIDLE
Staple SoleIDLE
Seat LastsIDLE
Cement Sole
Inspect & Pack
0
100
99IDLEIDLE IDLE Sole Pack
Rough SoleIDLE
Staple SoleIDLE
Seat LastsIDLE
Cement IDLE
Inspect & Pack
100
0
IDLEIDLE IDLE IDLE Pack
96 Shoe : 96th shoe in a batch of 100Legend
0
LASTING DEPARTMENT
This is not much an issue for large batches (100 pair)For example, Station 1 is idle for 4/104 % = 3.8%
For small batches, this is an issue (10 pair)For example, Station 1 is idle for 4/14% = 28.5%
This will be significant, if Lasting Department is theThis will be significant, if Lasting Department is the Bottleneck of the entire shop
THE ENTIRE FACTORY’S CAPACITY
THE ENTIRE FACTORY’S CAPACITY
Department 100 pair batch 10 pair batch
Cap CT MLT Cap CT MLT
Cutting 1170 41 41 209 23 23
Stitching 384 125 2250 384 12.5 225
Lasting 462 104 104 343 14 14Lasting 462 104 104 343 14 14
MLT, CT in minutes and Capacity in no of Shoes
THE ENTIRE FACTORY’S CAPACITY
100 pair batch
The Operating System is constrained by the lowest orThe Operating System is constrained by the lowest orSlowest capacity operation, this is StitchingHence it is 3 84 batches or 384 shoesHence, it is 3.84 batches or 384 shoes
The steamer’s six hours does not enter into calculationsThe steamer s six hours does not enter into calculationsThe case states it has ‘significant excess capacity’
THE ENTIRE FACTORY’S MLT
THE ENTIRE FACTORY’S MLT
What is the Manufacturing Lead Time?
Use Little’s Law
Little’s LawManufacturing Lead Time = Work in Process * Cycle Time
THE ENTIRE FACTORY’S MLT
Use Little’s law
Each department cannot run at its own maximum speedp pEvery department must run on a 125 minute cycle
It would be physically impossible for the product to Flow at different (average) rates in different depts for( g ) pLong.
Hence, we need to consider the system as a whole
THE ENTIRE FACTORY’S MLT
100 pair batch All figs in # of batches
Use Little’s law20 2 6 6 4 8
StitchingCutting Kitting Steaming Lasting FGLeather
20 2 6 6 4 8
WIPWithin 1 1 18 3 1Depts
WIP b f d ft d t t T bl 2 f CWIP before and after departments : Table 2 of Case,WIP within department from Case facts, except for Steaming (not given)
If batches are required to be in steamer for 6 hours then there must beIf batches are required to be in steamer for 6 hours, then there must be((6 * 60)/ 125) = 3 batches inside the Steamer at any time (assumed)
THE ENTIRE FACTORY’S MLT
100 pair batch All figs in # of batches
Use Little’s law
Stit hiC tti Kitti St i L ti FGL th
20 2 6 6 4 8StitchingCutting Kitting Steaming Lasting
WIPWithin 1 1 18 3 1
FGLeather
Depts
WIP = 1 + 2 + 1 + 6 + 18 + 6 + 3 + 4 + 1 = 42 batches (100 pair)MLT = 42 * 125 = 5250 mins = 87.5 hours = 11 daysy
We ignored WIP of Leather and FG. Normally, WIP should not include Raw Material Inv and FG as they are not WIPIn the case it is an MTO co, Raw Matl is procured on receipt of order and hence has to wait before the 20 batches, then we need to add 20 in the WIP
THE APPROPRIATE BATCH SIZE FOR THE STONEHAVENSTONEHAVEN
THE APPROPRIATE BATCH SIZE
In Cutting, we have significant excess capacity wheng g p yBatches are set at 100 pairs.Thus, if we cut down on batch size, Cutting’s capacityg p yWill reduce, but NOT the System’s Capacity
Let B be the batch size
4*5.25 + 4*0.05*B = 1.25*BSolving for B, we get B = 20 pairsWith batch size below 20, system loses CAPACITY
THE APPROPRIATE BATCH SIZE
As we change batches MLT and Cycle time getsAs we change batches, MLT and Cycle time gets affected
400
Cap
0
Batch Size0 10 20 30 40 50 60 70 80 90
THE APPROPRIATE BATCH SIZE
As we change batches MLT and Cycle time getsAs we change batches, MLT and Cycle time gets affected
9000
MLT
1000
Batch Size0 10 20 30 40 50 60 70 80 90
THE APPROPRIATE BATCH SIZE
Small Batch Big BatchFlexibility to Product Variety InflexibleHigh Material Handling Low Material HandlingInformation flow will be excessive
Information flow simpler
Easier to Spot Quality Problems: Tracing easy
Quality problems detected later
Less repetition, leading to lower efficiency. “ Learning P lt ”
Greater repetition enabling use of learning curve:
t ffi iPenalty” greater efficiency
THE APPROPRIATE BATCH SIZE
For reasons of ease of Information Flow, material Handling and to avoid a ‘learning penalty, it would be Best to keep the batch size at 20 pairsp p
THE TOP PRIORITIES
THE TOP PRIORITIES
What would be the priorities for improvement?
THE TOP PRIORITIES
Reducing Manufacturing Lead TimeReducing Manufacturing Lead Time
Cut batch size to 20 retaining capacityCut batch size to 20, retaining capacity
The shoes are transported trans Atlantic byThe shoes are transported trans-Atlantic byShips, taking weeks, would it make sensesaving a few days at the plant ??saving a few days at the plant ??
THE TOP PRIORITIES
Push to Pull might reduce WIP also ?Push to Pull might reduce WIP also ?
Line Balancing how? Why not?Line Balancing how? Why not?
STITCHING DEPARTMENT
Paced Line: parts moving through a Conveyor.The Bottleneck of such a line is not the sloweststation but the line-moving mechanism.g
In Flow lines, stations are essentially independent.
Balancing is more relevant to paced lines than flow.This is because of HR issues of fairness andThis is because of HR issues of fairness andcapacity can be increased in fine increments
LINE BALANCING
Rough Sole1 0 mins
Making the ConveyorU Shaped, makes1.0 mins
Seat Lasts0 6 i
Cement Sole
Line balancingEasier. The triangle is a
0.6 mins Sole0.9 mins
I t &
Cell
Staple Sole0.7 mins
Inspect & Pack
0.3 mins
LINE BALANCING – WHY NOT?
22
24
18
20
22
12
14
16
Tim
e (h
rs)
6
8
10
Cyc
le
High Variability
Low
0
2
4Capacity
Low Variability
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2
Release Rate (entities/hr)
LINE BALANCING – WHY NOT?
Non linear increase after 80% utilization
MLTMLT
0 80 100Utilization
TOOLS AND TECHNIQUES
What if you were the visitors to this plant and notWhat if you were the visitors to this plant and notUS students? How would you collect this information?How would you collect this information?
TOOLS AND TECHNIQUES
T t l hi h h l “t ”Two tools which help us “to see”“Learning to see” tools
Rapid Plant Assessment (RPA)V l St M i (VSM)Value Stream Mapping (VSM)
Staple yourself to an Order