Stone Haven

STONEHAVEN

STONEHAVEN

1.0 What are the daily capacities and Manufacturing Lead Time of Cutting, Cutting Stitching and Lasting Department considering a 100 pair i batch b t h 10 pair batch?

CUTTING DEPARTMENT

100 pair batch Capacity, CT and MLT

CUTTING DEPARTMENT 100 pair batch

Cutting Shoe leather 4* (5.25 4 (5 25 + 100 100*0 0.05) 05) = 41 minutes

Leathe rSheets

Cut Linings 4* (5.00 + 100*0.05) = 40 minutes Cut insole 4* (4 (4.00 00 + 100*0.04) 100*0 04) = 32 minutes

There are three parallel operations, operations each of which cuts 100 of four different Shoe components (creating 1200 pieces in 100 pair batch), each of which requires Four die changes

CUTTING DEPARTMENT 100 pair batch

Cutting Shoe leather 4* (5.25 4 (5 25 + 100 100*0 0.05) 05) = 41 minutes

Leathe rSheets

Cut Linings 4* (5.00 + 100*0.05) = 40 minutes Cut insole 4* (4 (4.00 00 + 100*0.04) 100*0 04) = 32 minutes

Capacity = 480/41 = 11.7 11 7 batches = 1170 pairs of shoe per shift MLT = 41 minutes. Cycle time = 41 minutes

CUTTING DEPARTMENT

10 pair batch Capacity, CT and MLT

CUTTING DEPARTMENT 10 pair batch

Cutting Shoe leather 4* (5.25 4 (5 25 + 10 * 0.05) 0 05) = 23 minutes

Leathe rSheets

Cut Linings 4* (5.00 + 10 * 0.05) = 22 minutes Cut insole 4* (4 (4.00 00 + 10 * 0.04) 0 04) = 17.6 minutes

Capacity = 480/23 = 20.9 20 9 batches = 209 pairs of shoe per shift MLT = 23 minutes. Cycle Time = 23 minutes

CUTTING DEPARTMENT

While changing from a 100 pair batch to a 10 pair batch the MLT declines 44 %, batch, % but the capacity declines a whooping 82 % - function of the setups, y long g compared p to the run times? which are relatively

STITCHING DEPARTMENT

STITCHING DEPARTMENT

Despite the strange back and forth flow of baskets to and from workers and supervisors in stitching, stitching this is a classic worker-paced line, with operations in q sequence.

STITCHING DEPARTMENT

100 pair batch Capacity, CT and MLT

STITCHING DEPARTMENT 100 pair batch

Prefit 4 workers k

Joining 3 workers k

Ornament 2 workers k

Time/pair

5 min

3 min

2.5 min

Task Time

500 mins

300 mins

250 mins

Operation Cycle Time

500/4= 125 mins

300/3= 100 mins

250/2= 125 mins

STITCHING DEPARTMENT 100 pair batch

Prefit 4 workers

Joining 3 workers

Ornament 2 workers

Task Time

500 mins

300 mins

250 mins

Operation Cycle Time

500/4 125 mins

300/3 100 mins

250/2 125 mins

Cycle Time for the department is 125 minutes p y is 480 / 125 = 3.84 batches = 384 shoes pper shift The Capacity

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 Law Manufacturing Lead Time = Work in Process * Cycle Time

STITCHING DEPARTMENT 100 pair batch

Prefit 4 workers

Joining 3 workers

Ornament 2 workers

Task Time

500 mins

300 mins

250 mins

Operation Cycle Time

500/4 125 mins

300/3 100 mins

250/2 125 mins

Manufacturing Lead Time: Easy way is to use Little’s Law WIP = 9 workers each with 2 batches ((one in pprocess and one as buffer)) = 18 batches MLT = 18 batches * 125 mins = 2250 minutes

STITCHING DEPARTMENT 10 pair batch

10 pair batch Capacity, CT and MLT

STITCHING DEPARTMENT 10 pair batch

Prefit 4 workers

Joining 3 workers

Ornament 2 workers

Task Time

50 mins

30 mins

25 mins

Operation Cycle Time

50/4 12.5 mins

30/3 10 mins

25/2 12.5 mins

Cycle Time for the department is 12.5 minutes p y is 480 / 12.5 = 38.4 batches = 384 shoes pper shift The Capacity

STITCHING DEPARTMENT 10 pair batch

Prefit 4 workers

Joining 3 workers

Ornament 2 workers

Task Time

50 mins

30 mins

25 mins

Operation Cycle Time

50/4 12.5 mins

30/3 10 mins

25/2 12.5 mins

Manufacturing Lead Time: Easy way is to use Little’s Law g worked on and one as buffer)) = 18 batches WIP = 9 workers with 2 batches ((one being MLT = 18 batches * 12.5 mins = 225 minutes

STITCHING DEPARTMENT

With batches of ten pairs, cycle time drops to 12.5 minutes and the capacity remains unchanged at 384 minutes, pairs of shoes. As a result A lt off no setups t required i d for f a new batch, b t h the capacity remains unchanged when batch sizes are reduced. reduced However a 90% reduction in batch size leads to a 90% cut in MLT

LASTING DEPARTMENT

LASTING DEPARTMENT

100 pair batch Capacity and MLT

LASTING DEPARTMENT 100 pair batch

Staple Sole 0.7 mins

Seat Lasts 0.6 mins

Rough Sole 1.0 mins

Cement Sole 0 9 mins 0.9

Inspect & Pack 0 3 mins 0.3

Cycle y Time is one minute per p ppair, driven by y the Bottleneck “Rough g Sole” The 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) Thus the Th th MLT for f the th batch b t h off 100 pairs i is i 104 minutes i t (100 + 4) With one batch allowed at one time, the Capacity is 480 / 104=4.62 batches=462 shoes

LASTING DEPARTMENT

10 pair batch Capacity CT and MLT Capacity,

LASTING DEPARTMENT 10 pair batch

Staple Sole 0.7 mins

Seat Lasts 0.6 mins

Rough Sole 1.0 mins

Cement Sole 0 9 mins 0.9

Inspect & Pack 0 3 mins 0.3

Cycle y Time is one minute per p ppair, driven by y the Bottleneck “Rough g Sole” The 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) Thus the Th th MLT for f the th batch b t h off 10 pairs i is i 14 minutes i t (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

Staple Sole 0.7 mins

Seat Lasts 0.6 mins

Rough Sole 1.0 mins

Cement Sole 0 9 mins 0.9

Inspect & Pack 0 3 mins 0.3

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 Minute by Minute snapshot of the Shoe Assembly line from T=99 to 103 Staple Sole

10 0

Seat Last 99

Rough Sole 98

Cement 97 Sole

Inspect & 96 Pack

Staple Sole IDLE

Seat10Lasts 0

Rough 99 Sole 1.0 mins

Cement 98 Sole

Inspect & 97 Pack

Staple Sole IDLE

Seat Lasts IDLE

Rough 10 Sole 1.0 .0 0minss

Cement 99 Solee So

Inspect & 98 Pack ac

Staple Sole IDLE

Seat Lasts IDLE

Rough Sole IDLE

Cement 10 Sole 0

Inspect 99 & Pack

Staple Sole IDLE

Seat Lasts IDLE

Rough Sole IDLE

Cement IDLE

Inspect 10 & Pack 0

Legend

96

Shoe : 96th shoe in a batch of 100

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 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

Stitching

384

125 2250 384 12.5 225

Lasting

462

104

41

209 23

104 343 14

MLT, CT in minutes and Capacity in no of Shoes

23

14

THE ENTIRE FACTORY’S CAPACITY 100 pair batch

The Operating System is constrained by the lowest or Slowest capacity operation, this is Stitching Hence it is 3.84 Hence, 3 84 batches or 384 shoes The steamer steamer’ss six hours does not enter into calculations The 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 Law Manufacturing Lead Time = Work in Process * Cycle Time

THE ENTIRE FACTORY’S MLT Use Little’s law Each department p cannot run at its own maximum speed p Every department must run on a 125 minute cycle It would be physically impossible for the product to g ) rates in different depts p for Flow at different ((average) Long. 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 law 20 Leather

WIP Within Depts

2 Cutting 1

6

6

Kitting

Stitching

1

18

4 Steaming 3

8 Lasting 1

WIP bbefore f and d after ft departments d t t : Table T bl 2 off Case, C WIP within department from Case facts, except for Steaming (not given) If batches are required to be in steamer for 6 hours, hours then there must be ((6 * 60)/ 125) = 3 batches inside the Steamer at any time (assumed)

FG

THE ENTIRE FACTORY’S MLT 100 pair batch

All figs in # of batches

Use Little’s law 20 L th Leather

WIP Within Depts

2 C tti Cutting 1

6

6

Kitti Kitting

Stit hi Stitching

1

18

4 St Steaming i

8 L ti Lasting

3

FG

1

WIP = 1 + 2 + 1 + 6 + 18 + 6 + 3 + 4 + 1 = 42 batches (100 pair) MLT = 42 * 125 = 5250 mins = 87.5 hours = 11 days y We ignored WIP of Leather and FG. Normally, WIP should not include Raw Material Inv and FG as they are not WIP In 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 STONEHAVEN

THE APPROPRIATE BATCH SIZE In Cutting, g we have significant g excess capacity p y when Batches are set at 100 pairs. g capacity p y Thus, if we cut down on batch size, Cutting’s Will reduce, but NOT the System’s Capacity Let B be the batch size 4*5.25 + 4*0.05*B = 1.25*B Solving for B, we get B = 20 pairs With batch size below 20, system loses CAPACITY

THE APPROPRIATE BATCH SIZE

As we change batches batches, MLT and Cycle time gets affected 400

Cap

0 0

10

20

30 40 50 Batch Size

60

70

80

90

THE APPROPRIATE BATCH SIZE

As we change batches batches, MLT and Cycle time gets affected 9000

MLT

1000 0

10

20

30 40 50 Batch Size

60

70

80

90

THE APPROPRIATE BATCH SIZE Small Batch Flexibility to Product Variety High Material Handling Information flow will be excessive Easier to Spot Quality Problems: Tracing easy Less repetition, leading to lower efficiency. “ Learning P lt ” Penalty”

Big Batch Inflexible Low Material Handling Information flow simpler Quality problems detected later Greater repetition enabling use of learning curve: greater t efficiency ffi i

THE APPROPRIATE BATCH SIZE For reasons of ease of Information Flow, material Handling and to avoid a ‘learning penalty, it would be p the batch size at 20 pairs p Best to keep

THE TOP PRIORITIES

THE TOP PRIORITIES

What would be the priorities for improvement?

THE TOP PRIORITIES

¾Reducing Manufacturing Lead Time ¾Cut batch size to 20, 20 retaining capacity ¾The shoes are transported trans-Atlantic trans Atlantic by Ships, taking weeks, would it make sense saving a few days at the plant ??

THE TOP PRIORITIES

¾Push to Pull might reduce WIP also ? ¾Line Balancing how? Why not?

STITCHING DEPARTMENT Paced Line: parts moving through a Conveyor. The Bottleneck of such a line is not the slowest g mechanism. station but the line-moving In Flow lines, stations are essentially independent. Balancing is more relevant to paced lines than flow. This is because of HR issues of fairness and capacity can be increased in fine increments

LINE BALANCING

Rough Sole 1 0 mins 1.0 Seat Lasts 0 6 mins 0.6 i

Cement Sole 0.9 mins

Staple Sole 0.7 mins

IInspectt & Pack 0.3 mins

Making the Conveyor U Shaped, makes Line balancing Easier. The triangle is a Cell

LINE BALANCING – WHY NOT? 24 22 20

Cycle Time (hrs)

18 16 14 12 High Variability

10 8 6

Low Variability

4

Capacity

2 0 0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Release Rate (entities/hr)

0.9

1

1.1

1.2

LINE BALANCING – WHY NOT?

Non linear increase after 80% utilization

MLT

0

80 Utilization

100

TOOLS AND TECHNIQUES

What if you were the visitors to this plant and not US students? How would you collect this information?

TOOLS AND TECHNIQUES

T tools Two t l which hi h help h l us “to “t see”” “Learning to see” tools Rapid Plant Assessment (RPA) V l Stream Value St Mapping M i (VSM) Staple yourself to an Order