STONEHAVEN

STONEHAVEN

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

CUTTING DEPARTMENT

100 pair batch Capacity, CT and MLT

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

Leathe rSheets

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

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

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

Leathe rSheets

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

Capacity = 480/41 = 11 7 batches = 1170 pairs of shoe per shift 11.7 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 00 + 10 * 0.04) = (4.00 0 04) 17.6 minutes

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

CUTTING DEPARTMENT

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

STITCHING DEPARTMENT

STITCHING DEPARTMENT

Despite the strange back and forth flow of baskets to and from workers and supervisors in stitching this is stitching, 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 Time/pair Task Time Operation Cycle Time 5 min 500 mins 500/4= 125 mins

Joining 3 workers k 3 min 300 mins 300/3= 100 mins

Ornament 2 workers k 2.5 min 250 mins 250/2= 125 mins

STITCHING DEPARTMENT
100 pair batch

Prefit 4 workers

Joining 3 workers

Ornament 2 workers

Task Time Operation Cycle Time

500 mins 500/4 125 mins

300 mins 300/3 100 mins

250 mins 250/2 125 mins

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

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 Task Time Operation Cycle Time 500 mins 500/4 125 mins

Joining 3 workers 300 mins 300/3 100 mins

Ornament 2 workers 250 mins 250/2 125 mins

Manufacturing Lead Time: Easy way is to use Little’s Law ( process and one as buffer) = 18 batches ) WIP = 9 workers each with 2 batches (one in p 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 Task Time Operation Cycle Time 50 mins 50/4 12.5 mins

Joining 3 workers 30 mins 30/3 10 mins

Ornament 2 workers 25 mins 25/2 12.5 mins

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

STITCHING DEPARTMENT
10 pair batch

Prefit 4 workers Task Time Operation Cycle Time 50 mins 50/4 12.5 mins

Joining 3 workers 30 mins 30/3 10 mins

Ornament 2 workers 25 mins 25/2 12.5 mins

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

STITCHING DEPARTMENT

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

LASTING DEPARTMENT

LASTING DEPARTMENT

100 pair batch Capacity and MLT

LASTING DEPARTMENT
100 pair batch Cement Sole 0.9 0 9 mins Inspect & Pack 0.3 0 3 mins

Staple Sole 0.7 mins

Seat Lasts 0.6 mins

Rough Sole 1.0 mins

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

LASTING DEPARTMENT

10 pair batch Capacity, Capacity CT and MLT

LASTING DEPARTMENT
10 pair batch Cement Sole 0.9 0 9 mins Inspect & Pack 0.3 0 3 mins

Staple Sole 0.7 mins

Seat Lasts 0.6 mins

Rough Sole 1.0 mins

Cycle Time is one minute per p y p pair, driven by the Bottleneck “Rough Sole” y g 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 th Th the MLT for the batch of 10 pairs is 14 minutes (10 + 4) f th b t h f i i i t 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 Cement Sole 0.9 0 9 mins Inspect & Pack 0.3 0 3 mins

Staple Sole 0.7 mins

Seat Lasts 0.6 mins

Rough Sole 1.0 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
Minute by Minute snapshot of the Shoe Assembly line from T=99 to 103
Staple Sole

10 0

Seat Last 99 10 Seat Lasts 0 Seat Lasts IDLE Seat Lasts IDLE Seat Lasts IDLE Legend 96

Rough Sole 98 Rough Sole 99 1.0 mins Rough Sole 10 1.0 0 s .0 mins Rough Sole IDLE Rough Sole IDLE

Cement 97 Sole Cement 98 Sole Cement 99 So e Sole Cement 10 Sole 0 Cement IDLE

Inspect & 96 Pack Inspect & 97 Pack Inspect & 98 Pack ac Inspect & 99 Pack Inspect & 10 Pack 0

Staple Sole IDLE Staple Sole IDLE Staple Sole IDLE Staple Sole IDLE

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 Cap Cutting Stitching Lasting 1170 384 462 10 pair batch

CT MLT Cap CT MLT 41 41 209 23 23

125 2250 384 12.5 225 104 104 343 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 or Slowest capacity operation, this is Stitching Hence, Hence it is 3.84 batches or 384 shoes 3 84 The steamer s six hours does not enter into calculations steamer’s 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 cannot run at its own maximum speed p p Every department must run on a 125 minute cycle It would be physically impossible for the product to ( g ) p Flow at different (average) rates in different depts for 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

2 Cutting 1 Kitting 1

6 Stitching 18

6 Steaming 3

4 Lasting 1

8 FG

WIP Within Depts

WIP b f before and after departments : Table 2 of Case, d ft d t t T bl fC 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 be hours ((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
20
Leather L th

2 Cutting C tti 1 Kitting Kitti 1

6 Stitching Stit hi 18

6 Steaming St i 3

4 Lasting L ti 1

8 FG

WIP Within Depts

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, we have significant excess capacity when g g p y Batches are set at 100 pairs. g p y Thus, if we cut down on batch size, Cutting’s capacity 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 MLT and Cycle time gets batches, affected
400

Cap

0 0 10 20 30 40 50 Batch Size 60 70 80 90

THE APPROPRIATE BATCH SIZE

As we change batches MLT and Cycle time gets batches, 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 Penalty” P lt ” Big Batch Inflexible Low Material Handling Information flow simpler Quality problems detected later Greater repetition enabling use of learning curve: greater efficiency t 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 p Best to keep the batch size at 20 pairs

THE TOP PRIORITIES

THE TOP PRIORITIES

What would be the priorities for improvement?

THE TOP PRIORITIES

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

THE TOP PRIORITIES

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

STITCHING DEPARTMENT Paced Line: parts moving through a Conveyor. The Bottleneck of such a line is not the slowest g station but the line-moving mechanism. 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 1 0 mins Seat Lasts 0.6 i 0 6 mins Cement Sole 0.9 mins Inspect & I t Pack 0.3 mins

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

Staple Sole 0.7 mins

LINE BALANCING – WHY NOT?
24 22 20 18

Cycle Time (hrs)

16 14 12 10 8 6 4 2 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 Low Variability Capacity High Variability

Release Rate (entities/hr)

LINE BALANCING – WHY NOT?

Non linear increase after 80% utilization

MLT

0 Utilization

80

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

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