simulation model from lean manf

8/7/2019 simulation model from lean maNF.

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y Lean manufacturing or lean production, is a productionpractice that considers the expenditure of resources for any goal other than the creation of value for the end customer tobe wasteful, and thus a target for elimination.

y W orking from the perspective of the customer whoconsumes a product or service, "value" is defined as any action or process that a customer would be willing to pay for.

y Basically, lean is centered on preserving value with lesswork.

y A s a production management tool , production theory describes a system that deliver s a finished product free fromdefects to a customer, in zero time, and with nothing left ininventory.



y Moreover ,it can be summarized into three mainpoints:

1.Eliminate or reduce all activities that do not add value to the final product.

2. Pull material through the process

3. Reduce variability by controlling uncertainties within the process.

y Lean manufacturing is a management philosophy derived mostly from the Toyota Production System(TPS) ,Taiici Ohno, an engineer working for Toyota,developed lean production theory.

y It is renowned for its focus on reduction of the originalToyota seven wastes to improve overall customer value,but there are varying perspectives on how this is bestachieved.



y primary goal of lean production theory is to reduce or eliminate theshare of f low activities in a project while increasing the efficiency of conversion activities.

The following list outlines key principles of lean production . Reduce the share of non value-adding activities.

Increase output value through a systematic consideration of customer requirements. Reduce variability. Reduce cycle times. Simplify by minimizing the number of steps, parts, or linkages. Increase output flexibility. Increase process transparency. Focus control on the overall process. Build continuous improvement into the process. Balance flow improvement with conversion improvement.

Benchmark.



y The procedure starts with identifying objectives. Objectivesare then documented and studied in details.

y The next step is to develop a value stream mapping toidentify material and information of the current and futurestates. The number of people needed to run each cell is

then determined.y The next step is to use ergonomic tools to evaluate the

proposed cells to ensure safe work environment. Simulationmodeling is then used to evaluate the performance of theproposed manufacturing cells.

y The simulation results will be used to identify down timefactors and constraints that reduce productivity.

y Possible solutions to reduce down time are then discussedand implemented. This process is continued until desired

results are achieved.



start

Set objective and identify

constraints

Develop value stream mapping

Determine manpower requiredto run the cells

Ergonomic evaluation

A ccepted

Cell evaluation usingsimulation

A chieved objective

implementation

no

yes

yes



y Objectives

The current production system has several limitations

including ergonomic, longer material handling, lower quality,less labor productivity, more floor space, More scrap, large

work-in-process and long setup and change over time. The

over all objective is to re-arrange the current production

system into manufacturing cells to overcome these

limitations.

1. Ergonomic

2. Quality 3. Traceability and accountability

4. Setup and change over time



y V alue stream mapping

The value stream mapping (VSM) one of the V MOS toolsused to identify material and information of manufacturing processes. A VSM is usually achieved intwo states; current state and future state. The current

VSM is used as a base line to identify activities thatrequired achieving the future state or manufacturing

cells.� Determine the manpower

The manpower required to run each manufacturing cell isdetermined at this stage. The measures used at this stageare the balance time between the operator and themachine, and the ergonomic constraints. The balancetime refers to the difference between the machine cycletime and the labor cycle time requires to load and unloadall machines in the cell.



y Ergonomic evaluation

A t this stage, ergonomic principles are implemented tofitting jobs to people. The Energy Expenditure andNOISH Composite Lifting Index tools are used toevaluate each layout and ensure safe work environment.

� Cell evaluation

The simulation technique is used at this stage to

evaluate the performance of the proposedmanufacturing cells required to run eachmanufacturing cell. Each manufacturing system issimulated using Simul8 simulation software. Simul8 isa simulation software that allows the user to create asimulation using elements that represent machines,conveyors, buffers and parts. It is powerful simulationsoftware that is remarkably easy to use and understand.



y Simulation is an extremely powerful tool that allows for apreview of how things will run in the real word, thus allowing fora decrease in cost, risk reduction, and preview of the possibility of failures.

y It also allows for a better understanding of the system being

studied and to perform different scenarios.y The simulation model allows possible changes to the system

before actually implemented. It also improves the utilization of technology by determining the throughput and manpowerrequired to run each manufacturing cell.

y Each manufacturing system is simulated using Simul8simulation software. Simul8 is a simulation software that allowsthe user to create a simulation using elements that representmachines, conveyors, buffers and parts. It is powerful simulationsoftware that is remarkably easy to use and understand.



The following are the assumptions used in the model:

It is assumed that there are 8 hours per shift, 3 shiftsper day and 5 days per week.

There are two breaks per shift and each break has 12min.

There is 20 min lunch per shift

The Exponential Probability Distribution is adopted for

theMean Time Between Failure (MTBF) and ErlangDistribution is adopted for theMean Time To Repair(MTTR).



The input parameters used in the model are the machine cycletime,MTBF and MTTR and change over and setup time.

y Machine cycle time, This factor refers to the time spent by apart at a certain operation. It includes the loading andunloading time and machine cycle time.

y Mean time between failure (MTBF), This factor refers to thetime a work center is expected to work without failing.

y Mean time to repair (MTTR), This factor refers to the timerequires to fix the work-center after any failure.

y Changeover and setup time, The manufacturing cellproduces several parts, which require different setup. Thisfactor involves the time required to changeover the cell.



y CellularManufacturing (CM) system is an applicationof lean manufacturing aims to partition manufacturingsystems into manufacturing cells .

y Studies have shown that manufacturing companies thatimplemented CM systems improved their productivity level by increased output, increased rate of return oninvestment, increased profit, improved quality,decreased setup time, overdue orders and work in-

process inventories, reduced material handling cost andreduced space requirements .

y So far, very few simulation models have been developedto evaluate the performance of cellular manufacturingsystems



Before the model could be constructed, data was needed.This data included the machine layout for the currentmanufacturing system and proposed manufacturing cells,the parts to be produced, the machine cycle and setuptimes, and production volumes. Data is then analyzed andthe model is constructed. Both manufacturing systems are

simulated and the model .was run for 40 hours.The results showed that the current manufacturing cellhad a productivity rate of 233 pcs/shift/man, and theproposed lean manufacturing showed a productivity rateof 349 pcs/shift/man. That is 49% increase per operator pershift over the traditional manufacturing system. The

cellular arrangement showed 35% decrease in labor, and30% decrees in scrap over the existing traditionalmanufacturing system.



Manufacturing system Machine efficiency (%) Labor productivity Labour utilization

(Pcs/Shift/Man)

Traditional 95 233 64

Cellular 95.3 349 84.4

Simulation results

simulation model from lean manf

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