1

2.810 Systems Summary

Nov 16, 2015 T. Gutowski

2

What we covered

1.  History, reoccurring problems in a new setting

2.  Time/Rate & unreliable machines/ buffers

3.  Additive Mfg 4.  TPS 5.  Supply Chain Issues

3

Early History

•  Interchangeable parts: Hounshell-intro – Technology, diffusion, cost

•  Model T Ford: Hounshell Ch 6 – Moving assembly, work force..

•  Model A Ford: Hounshell Ch 7 – Ford stumbles, GM model…

4

What conditions lead to a revolutionary new mfg system? Interchangable parts

Mass Production TPS/Lean (Page numbers from Machine that Changed the World)

Where/when US Armories 1794-1827 Springfield to certification

Ford 1908-1927 Model T start to finish

Toyota 1945-1975 Ohno

Need/ Opportunity

Military field repairs

Mobility alternative

Re-build after WWII

Financing U.S. Gov’n Ford reinvests Tokyo banks/ Keiretsu p 194

Workforce Scarce Yankees Yankee mechanics, immigrants

Unions/ p 54 lifetime employment

Enabling Technology

Mechanization of machining

Interchange-able parts, moving assembly & stamping

Work organization

5

Reoccurring Issues-Summary Issue US Armories Ford Toyota

Cost Effectiveness

Doubtful for long time

yes Long time

Social disruption

Tensions at Harper’s Ferry

$5/day & Harry Bennett

Avoid strike, but…

Standardization & flexibility

standardization More standardization

Still more…

Benefits & costs of inventory

Not mentioned Vertical integration & low inventories

JIT, low inventories…

Work organization

Hand craft to gauging

Centralized control

Push Vs pull - some local control

6

Time and Rate

•  Process Plans •  Little’s law: L = λ W •  M/M/1 Queue •  Unreliable machine •  Zero Buffer line: Buzacott’s result •  Infinite Buffer line: bottleneck •  Finite buffers (M/M/1) and time dependent

failures

7

Additive Mfg

•  Videos, no

•  Slides, yes

•  DFM; heat transfer

•  Speculation about future supply chains

~ 1 cm

8

Additive Mfg

9

Production Rate Stuck!

What did your homework tell you to do?

10

BAAM Additive Mfg

11

TPS

•  Overview and Data: Machine that changed… Ch 3 and Ch 4

•  Major components and philosophy •  Monden:

– Reduction of waste – Smooth flow – Produce to demand – Local control

12

TPS

•  TPS cell (JT. Black Ch 4) •  Note: mTi + MTi ≤ CT •  Problems with implementation •  McCoby

13

Standard Work for Cell PART:JT. Black Cell Operators:PROCESS# OPERATION Man Walk Auto1 Raw 32 Saw 15 3 603 L1 10 3 704 L2 12 3 505 HM 12 3 1206 VM1 20 3 707 VM2 20 3 608 G 15 3 509 F.I. 19 6

160 18060 80 100 120TIME {secs}

20 40 140

Cell produces one part every 153 sec

Note: machine time Max (MTj) < cycle time CT

i.e. 120+12 < 153

14

TPS Cell

1.  Production rate = λ

2.  WIP = L?

3.  Time in the system = W?

λ =1part

153 sec= 23.5 parts/hr

15

Machining Cell

1 2

3 4

5

6 7 8 9

10 11

12 13

Number of round trips; 13

Saw 3+15 + 153

#1 decoupler

1.5 +153

L1 1.5+ 10

+153

……. …….

Grind 1.5+ 15

+153

Manual and walk

19+3 out

150 153X13=1989

1989 + 150 = 2139

16

By Little’s Law L = (13 + 1) X (150/153) +

13 X (3/153) = 13.98 parts rate, λ = 1/153 parts/second W = 153 X 13.98 = 2139 sec

17

TPS Cell

Increase production rate:

a) add additional worker to cell

b) modify machine bottlenecks

18

Manual (Sec)

Walk to (Sec)

Machine (Sec)

Raw 3

Saw 15 3 60

L1 10 3+3 70

L2 12 3 50

HM 12 3 120

VM1 20 3 70

VM2 20 3+3 60

G 15 3 60

F.I. 19 3 + 3

Totals M+W = 159 490

Work 1 80

Work 2 79

WORKER 1

WORKER 2

To increase production rate add 2nd worker

19

What is the production rate for this new arrangement?

Check max(MTj) < CT

Worker 1; 80 = 80

Worker 2; 12+120 >79

One part every 132 seconds

We are limited by the HM (horizontal mill)

Can we shift work off of the HM to reduce the cycle time?

λ =1part

132 sec= 27.3 parts/hr

20

Manual (Sec)

Walk to (Sec)

Machine (Sec)

Raw 3

Saw 15 3 60

L1 10 3+3 70

L2 12 3 50

HM 12 3 120 80

VM1 20 3 70 80

VM2 20 3+3 60 90

G 15 3 60

F.I. 19 3 + 3

Totals M+W = 159 490

Work 1 80

Work 2 79

WORKER 1

WORKER 2

21

Standard Work for Worker #2 Rod Support Operators: Worker #2

PROCESSOPERATION Man Walk Auto

from decoupler 1.5L2 12 3 50HM 12 3 80VM1 20 3 80VM2 20 1.5 90

160 18060 80 100 120TIME {secs}

20 40 140

Cycle # 1 Cycle # 2

Operator waiting On machine

+3

22

What is the new production Rate?

Check max(MTj) < CT

Worker 1; 80 = 80 Worker 2; 110 > 79

Hence Worker #2 will be waiting on Vertical Mill #2

23

What is the new production Rate?

•  The new production rate is; one part every 110 sec

•  Pro and Cons; Worker “idle”, can’t speed up by adding additional worker

•  Design for flexibility make; Max(MTj) < CT/2

λ =1part

110 sec= 32.7 parts/hr

24

Manual (Sec)

Walk to (Sec)

Machine (Sec)

Raw 3

Saw 15 3 60

L1 10 3+3 70

L2 12 3 50

HM 12 3 120

VM1 20 3 70

VM2 20 3+3 60

G 15 3 60

F.I. 19 3 + 3

Totals M+W = 159 490

Work 1 80

Work 2 79

WORKER 1

WORKER 2

A B

Alternative solution add 2 HM’s

λ =1part90 sec

= 40 parts/hr

Almost double!

25

TPS cell summary

1.  Original cell - 23.5 parts/hr 2.  Additional worker- 27.3 parts/hr 3.  + Shift work- 32.7 parts/hr 4.  ++ add additional HM 40 parts/hr

26

Supply Chains

•  Safety Stocks •  “Crack the Code” •  See note from Prof Graves: •  Special Case: E(LT) = const, and •  σD are not correlated •  Reorder average demand + Safety •  Average grows like LT, and σD ~ √ LT

27

28

The Next System?

Mass Customization?

29

Speculation about Digital Mfg

•  Additive Mfg – Flexible – Fast for one-off – Some de-skilling of Mfg – Mfg close to home – …seamless digital mfg?