Post on 29-Jun-2015
JIT and Lean operations
Chapter 16
Objectives1. Understand lean operations and its
differences with mass production.
2. Recognize the 7 wastes.
3. Learn the differences between push and pull systems
4. Describe how kanban works in a pull system.
5. Identify the ways of coping with variability in the production process
Making bespoke shoesA pair of bespoke shoes begins with a vision. I meet
personally with every client to take measurements and imprints of the feet, draft a design and select materials. [snip]
To make a pair of shoes by hand is an arduous process that requires over sixty hours of meticulous labor. The pattern must be drafted and perfected. The uppers must be cut and fashioned to the lasts. The infrastructure must be constructed, and the welts must be hand-sewn to the insole. My bespoke shoes are constructed entirely of leather and provide the foot unparalleled support; the result is strong, structurally sound footwear.
Before the shoe is soled, I meet again with the client. This additional fitting allows me to make whatever small revisions are necessary to achieve a flawless fit. The shoe is then soled and exquisitely finished with hand-painted London waists and natural waxes. When every detail is perfected, I will personally deliver or ship the finished shoes, along with custom trees and flannel bags, to the customer.
From http://www.perryercolino.com/bespoke_shoes.php
Craft production1 skilled worker does all tasksFocus: qualityPros
Workers engaged, interestedResponsibility for the final product improves
qualityCons
High wage workers (need to understand whole process)
Long lead timesWorker absences lower productionLong and risky training cycles
The next step – Mass productionWorkers do 1 or 2 simple tasksProducts built to forecastFocus: economies of scalePros
Low wage, easily trainable workersLarge quantities possible
ConsLong lead timesBoredomVariable qualityHigh WIPDependent on forecast
Large lotsPro
Economies of scaleLow setup costs on a per-unit basis
ConsNeed advance planning (overproduction)Need storage (queues waste time)Need financing (inventory waste)Transport and storage on floor (wasted
transportation and motion)Tracking complexity (over-processing)Lag in realizing defectsLot-wide defects
LeanPros
Still 1 or 2 tasks/workerWorkers engaged by process improvementWorkers goal-orientedProduce to customer demand, not forecastReduce inventory
Cons?
Lean focuses on waste elimination1. Overproduction through forecasting errors2. Queues3. Transportation4. Inventory5. Unneeded motion6. Over-processing (no-value added
processing)7. Defects
Variability as a source of wasteCons:
Increases WIP and lead time even in well-balanced processes
Decreases qualityCoping with variability
Junk defects and produce with overtimeShip to customers, pay warranty costsRigorous end-of-line testingAdapt designRoot-cause analysis
Perform experiments
Push versus pull systems
Push: “build it and they will come.” Plan. Then do.Needed if lead times are very longImmediate product availability
Pull: Don’t act until asked.Adapts to demand changesConfiguration is possibleUncovers quality problems more quickly. (Why?)
KanbanJapanese for “card”*What to produce when and in what quantitySteps
1. User takes product with a kanban attached.2. Kanban is sent to the producer as a signal
to restock product.3. Producer delivers product with kanban.
Doesn’t need to be a card http://www.youtube.com/watch?v=xPyEtuLT
BmM
* = Many lean terms are taken Japanese even if there are perfectly good English equivalents. Worse, redundancies like “kanban cards” are regularly used.
Lean operationsCons
Inventory can be a buffer to problems (also a pro)Barriers to implementation
Works best in already well controlled processes allowing experiments
Seemingly obvious (Examine further in Toyota case)
Day-to-day problems can soak up process improvement time
Requires managers give up some control to workers
“Plan. Then do.” is more intuitive.Traditional goal of production is plan execution, not
process improvement
JIT versus TPS versus LeanJust-in-time
Products available “just in time” for use.Toyota Production System
Perform repeatable experimentsSee the Toyota case and “Decoding the DNA
of the Toyota Production System” in HBR by Spear and Bowen (1999)
Lean operationsFocus on elimination of waste
Terms used interchangeably in practice
Objectives1. Understand lean operations and its
differences with mass production.
2. Recognize the 7 wastes.
3. Learn the differences between push and pull systems
4. Describe how kanban works in a pull system.
5. Identify the ways of coping with variability in the production process