Stone Haven

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


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


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




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


100 pair batch

Joining3 workers

Prefit4 workers

Ornament2 workers


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


100 pair batch

What is the Manufacturing Lead Time?


100 pair batch


Use Little’s Law

Little’s LawManufacturing Lead Time = Work in Process * Cycle Time


100 pair batch

Joining3 workers

Prefit4 workers

Ornament2 workers


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


10 pair batch



10 pair batch

Joining3 workers

Prefit4 workers

Ornament2 workers


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


10 pair batch

Joining3 workers

Prefit4 workers

Ornament2 workers


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


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


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


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


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


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



Use Little’s Law

Little’s LawManufacturing Lead Time = Work in Process * Cycle Time


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


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)


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


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


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


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


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?


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

Documents

Stone Haven