LEAN system

Value That customer is willing to pay That changes products color, function, shape, other attributes so that the product is getting closer to the customers requirements That we do right at first time

Wastes Those processes which directly do not create value for customers (muda, mura, muri) : –that are not necessary, and must be eliminated –That are necessary, because these are supporting value-add processes, cannot be eliminated (like transporting) Muda – 7 wastes of lean Mura – not leveled workflow Muri – overloading of workers and assets

Lean thinking Operation Traditional improvement Lean improvement Non value-add process Value-add process

Supporting goals A balanced system, smooth, rapid flow of materials and/or work Supporting goals: –Eliminate disruption –Make the system flexible –eliminate waste, especially exess inventory

There are 7 wastes in LEAN (TIMWOOD): Inventory Overproduction Waiting Unnecessary transportation Processing waste Inefficient work methods Defects

JIT Building Blocks Process design Product design Personnel/organizational elements Manufacturing planning and control

Process Design Small lot sizes Setup time reduction Manufacturing cells Limited work in process Quality improvement Production flexibility Little inventory storage

Benefits of Small Lot Sizes Reduces inventory Less storage space Less rework Problems are more apparent Increases product flexibility Easier to balance operations

Setup time reducing changeover time ( because small lots require frequent setups) SMED (single minute exchange of die) –External –Internal activities.

Manufacturing cells In Functional Manufacturing similar machines are placed close together (e.g. lathes, millers, drills etc) In Cellular Manufacturing systems machines are grouped together according to the families of parts produced. The major advantage is that material flow is significantly improved, which reduces the distance travelled by materials, inventory and cumulative lead times.

Quality improvement Kaizen – continuous improvement of the system Jidoka (Autonomation) – automatic detection of defects during production. It consist two activities: –One for detecting defects when they occur –Another for stopping production to correct the cause of defects. Poka Yoke safeguards built into the process to reduce the possibility of errors.

Work flexibility Overall goal of lean is to achieve the ability to process mix of products in a smooth flow. One potential obstacle is bottlenecks, which occur when portions of the system become overloaded. Because of –The absence of workers  cross trained workers –Not leveled workflow  use takt time Example: –Total time per shift is 480 minutes per day –There are two shifts per day –There are two 20-minutes break and a 30 minutes lunch break per shift. –Daily demand is 80 pieces Net time available per day= 2*(480-20*2-30)=820minutes Takt time=820minutes/80 pieces=10,25 minutes If the actual cycle time is higher, our customers won’t get their needs, if the actual cycle time is lower, there will be overproduction, and we have to inventory surplus products.

Inventory storage Inventory storage is a waste, a buffer which can cover up problems, partly because inventory makes them seem less serious.

Product Design Standard parts – fewer parts to deal with  lower training costs Modular design – easy to satisfy different needs Highly capable production systems – quality is designed into the product and the production process Concurrent engineering

Personnel/Organizational Elements Workers as assets Cross-trained workers Continuous improvement Cost accounting Leadership/project management

Manufacturing Planning and Control Level loading Pull systems Visual systems Close vendor relationships Reduced transaction processing Preventive maintenance

Mixed model sequencing the sequence (on the base of setup time and setup cost – let it be now A,C,B) how many times the sequence should be repeated (determine the smallest integer) how many units to produce ModelDaily quantityUnits per cycle A1010/5=2 B1515/5=3 C55/5=1

Pull/Push Systems Pull system: System for moving work where a workstation pulls output from the preceding station as needed. (e.g. Kanban) Push system: System for moving work where output is pushed to the next station as it is completed

Visual system Kanban- a manual system responds to signals of the need for delivery of parts and materials (both to the factory and between the workstation) –Production kanban –Conveyance kanban

Traditional Supplier Network Buyer Supplier Figure 12.4a

Tiered Supplier Network Figure 12.4b Supplier Buyer Supplier First Tier Supplier Second Tier Supplier Third Tier Supplier

Comparison of JIT and Traditional FactorTraditionalJIT Inventory Much to offset forecast errors, late deliveries Minimal necessary to operate Deliveries Few, largeMany, small Lot sizes LargeSmall Setup; runs Few, long runsMany, short runs Vendors Long-term relationships are unusual Partners Workers Necessary to do the work Assets Table 12.3

Preventive maintenance Total Productive Maintenance – operators responsible for the equipments they use Housekeeping – 5S –Sort –Straighten –Sweep –Standardize –Self-discipline

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