theory of constraints and lean thinking - sae international · drum-buffer-rope assembly buffer...

Working SmarterPutting Best Practices to Work:

Transforming Logistics Capability into Readiness at the Marine Corps

Maintenance Centers

Maj Don Humpert, USMChumpertde@matcom.usmc.mil

The Problem

• Example: MK-48 Power Unit– Fielded in ’85– Planned SLEP—never happened– Wearing Out– Of about 1700 fielded,

only 330 have been rebuiltor through enhanced IROAN

60%

65%

70%

75%

80%

85%

90%

95%

100%

1/7/00 4/7/00 7/7/00 10/7/00 1/7/01 4/7/01 7/7/01 10/7/01 1/7/02 4/7/02

Report Date

Rea

dine

ss (R

-Rat

ing)

Enhanced LVS Power Unit Non-Enhanced Power Unit (Minus MPS/NALMEB Fleet)

The Depot ContributionRebuilt/E-IROAN

No Depot/“Bare-Bones” IROAN

Average 12% Higher Readiness

And…

10

23

0

5

10

15

20

25

"Enhanced" "Non-Enhanced"

Average Annual OpFor Hours in Maintenance per Vehicle

But…

• Rebuild too expensive• E-IROAN not cheap either…• Production—(ahem)—sluggish

The Challenge

• Increase Throughput and make schedule without increasing Operating Expenses or sacrificing quality

TOC

ISO Lean

MRPII

Theory of Constraints**Five Focusing Steps**

1. Identify the Constraint

2. Exploit the Constraint

3. Subordinate everything else to the Constraint

4. Elevate the Constraint

5. Go back to step one (Avoid Inertia)

CONSTRAINT BUFFER

Process 1a Process 1b Process 1c

Process 2a Process 2b THECONSTRAINT

ASSEMBLY Process 3 SHIPMaterial Release

Drum-Buffer-RopeASSEMBLY BUFFER

SHIPPING BUFFER

Simplified DBR

Process 1a Process 1b Process 1c

Process 2a Process 2b Process 2c

ASSEMBLY Process 3 SHIPMaterial Release

OK Act

SHIPPING BUFFER

Production vs. Project• Production:

– Lots of queue time relative to touch time– Usually waiting for something to start– Usually decrease RCT by reducing time in queue

• Project:– Little queue time relative to touch time– Usually waiting for something to finish– Decrease RCT by removing safety time built into

individual tasks

Critical Chain Solution

• Use safety time for the whole project, not individual tasks

• Reduce WIP• Don’t batch inductions• Stop multi-tasking

• Buffer Management

Tasks

• Step 1: Tasks arranged in chronological order

20

161010

1616

Remove Safety Time

• Step 2: Safety time removed from individual tasks.

7 9

10

75 6

Resource Assignments

• Step 3: Resources are assigned to each task

7 9

10

75 6

Resource Sync

• Step 4: Resource demands are de-conflicted

7 9

10

75 6

Critical Chain

• Step 5: Critical Chain is identifiedCritical Chain

7 9

10

75 6

Project Buffer

• Step 6: Project Buffer added—50% of critical chain touch time, rule of thumb

Critical Chain7 9

10

75 6

17

Feeding Buffers

• Step 7: Feeding Buffers are placed between Critical Chain and non-Critical Chain activities

Feeding Buffer

17

7 9

10

75 66

Capacity Buffers

• “Drum resource” used to determine Capacity Buffer between projects

50% of Drum touch time (8 days) used as Capacity Buffer

7 9

10

75 66

7 9

10

75 66

7 9

10

75 66

17

17

17

Critical Chain + SDBR

Process 1a Process 1b Process 1c

Process 2a Process 2b Process 2c

ASSEMBLY Process 3 SHIP

New Materials

Feeding Buffer

Project Buffer

Shipping Buffer

7 9

1710

75 66

Capacity Buffer

1710

7 9

75 66

Production Management =(A)(Schedule) + (pull system)

• Critical Chain project management• Simplified Drum-Buffer-Rope production• Theory of Constraints “thinking”• MRPII “engine”

Implications for MRP

• Create Critical Chain in usual way • Modify item masters, routers and BOMs to reflect

the new lead times, routes and BOM indentures• Create Project Level Work Order and route using

the CC schedule• Run MRP to time phase materials and create a

dispatch list and shop orders with CC priorities• Create “Immediate Action” report for SDBR and

“Project Buffer Status” report for CC to manage by buffers

RCT

ResultPush (MRP)

WIP

Pull (MRPII+TOC)

Throughput

Maintenance Center Albany

Repair Cycle Time

020406080

100120140160180200220240

0 20 40 15 35 55 75 0 20 40 60 80Vehicle Number

Day

s

FY-00

FY-01

FY-02

Articulation Hitch Problems

Labor Hours

0125250375500625750875

1000112512501375150016251750

0 20 0 20 40 60 80 5 25 45 65 85

Vehicle Number

Hou

rs

FY-00

FY-01

FY-02

Engine RCT

0102030405060708090

100

0 20 0 20 40 60 80 5 25 45 65 85Vehicle Number

Day

s

FY-00

FY-01

FY-02

Engine Labor Hours

0255075

100125150175200225250275300325

0 20 0 20 40 60 80 1 21 41 61 81 101

Vehicle Number

Hou

rs

FY-00

FY-01

FY-02

• Sort: Get rid of what’s not needed. Be ruthless.• Straighten: Organize what belongs (Parts and

Materials).• Scrub: Clean everything (Equipment, Floors, and

Walls).• Standardize: Assign tasks. How will you keep your

shop clean and organized and who will do it?• Safety: + ALWAYS put safety first! +• Sustain: Audit shops. Create checklist.

Lean Thinking 6S Concept

Cable Shop—Before

Cable Shop—After

Body Shop—Before

Body Shop—After

MK-48 Readiness Contribution

“What-If” 2000• 6 per month per depot• 167 days/vehicle• $152K /vehicle

“General, for $137M we could raise readiness 12%, but it will take 19 years”

“What-If” 2003• 19 per month per depot• 51 days/vehicle• $120K /vehicle

“General, for $108M we could raise readiness 12%, in 2 years”

66***66**AAV – P & C Variants

146159213M88 Tank Retriever

3918No dataM149A2 Water Trailer

82282M970 Refueler

*63278M936 Wrecker

7048113M931 5-ton

49269MK17 Trailer

3822126MK16 Trailer

9569229MK15 Trailer

342356MK14 Trailer

111-16792-102180-240LAV

4853167MK48

ActualCritical ChainBeforeProduction Line

And Not Just MK-48s…

*No current production line.**AAV hull repair and assembly after receipt of hull from UDLP.***The AAV critical chain has been established to cover the work performed after the hull has been modified by UDLP.

9922AAV – C Variant

445AAV – P Variant

335M88 Tank Retriever

7717M149A2 Water Trailer

13**68M970 Refueler

0*06M936 Wrecker445M931 5-ton

123MK17 Trailer

122MK16 Trailer

122MK15 Trailer

338MK14 Trailer

7713LAV

393555MK48

ActualTOC TargetBeforeProduction Line

WIP Reduction

*Production line completed.**Awaiting one part to complete; received 23 Aug 02.

to be continued…

Maj Don Humpert, USMChumpertde@matcom.usmc.milDSN 567-7417, Comm (229) 639-7417

Questions?