simulation comparison parameters-final

8/7/2019 Simulation Comparison Parameters-Final

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SIMULATION COMPARISON PARAMETERS

1] Throughput and Make-span Objective: [Selected]

To maximize the throughput of the facility is one of the most general criteriaadapted in the industry. Throughput is equivalent to the output rate of the

facility. The output rate is frequently decided by the output rate of thebottleneck machine. Maximizing Throughput of the facility means

maximizing output of the bottleneck machine. The objective is that Thescheduler must try to ensure that the bottleneck machine is never idle.

Minimizing Make-span is also important, as its objective is closely related tothe objective of Throughput measure. The make-span is denoted my C max

and calculated as: n

Cmax = max {Cj} where, j = 1

Cj = Completion time of Job j.

Make span = Max [PED (Opn) PSD (Op1)] MO

It is the difference of planned end date of last operation and planned start date

of first operation, over all MO scheduled.

PSD (Op1)] PED (Opn)

Make Span


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2] Average Production Cycle:

This parameter defines average production cycle per MO. The Make spanonly shows the start and end of the scheduled MOs globally, where as it is

not indicating anything about quantum of MO processed during this span.

It may happen that with different set of MO, make span is more or lesssame, but one schedule is able to produce higher number of MOs thenothers. This criterion is also important, when production environment havelarge number of MOs and of similar priorities.

Average Production Cycle = [Cycle time for MO] / number of MOs all MO

(CT [1]+CT [2]+.+CT [n])

APC =n

3] Lateness or Tardiness: [Selected]

CT [1]

CT [2]

CT [n-r]

CT [n]


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The lateness of the job j is defined as:

L j = [Cj - dj ] here dj = Due date of job j

And Cj = Actual Completion Date

a] Total Lateness can be defined as:

Summation of all the lateness for all Manufacturing Orders.

Total Lateness = [L1 + L2 + L3 + + Ln]

b] Average Lateness can be defined as:

L1 + L2 + L3 + + LnTotal Lateness =

n

Another criteria related to due date is Tardiness. Tardiness means number of jobs those are

tardy in a given environment at a particular time, and it is not concerned with how much tardy ajob actual is.

The tardiness of a job j is defined as:

Tj = max {(Cj-dj), 0}

a] Total Tardiness can be defined as:

Total Tardiness = [T1 + T2 + T3 + + Tn]

b] Average Tardiness can be defined as:

T1 + T2 + T3 + + TnTotal Lateness =

n


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4] Total Weighted Delay:

Some time it may happen that though the total delay is quite large but thehigh contribution is from manufacturing orders, which are not with high

priority. This situation may be acceptable, as the MO with higher priority

has less delay.

It may be a god idea to calculate total weighted delay, which is an indexwith two parameters, namely delay and priority of manufacturing order.

a] Total Weighted Delay can be defined as:

Summation of all the weighted Delay / lateness for manufacturing orders.

Total Weighted Delay = [P1*L1 + P2*L2 + P3*L3 + + Pn*Ln]

b] Average Weighted Delay can be defined as:

[P1*L1 + P2*L2 + P3*L3 + + Pn*Ln]

Average Weighted Delay=

n

One can set standard indicator to compare these values and to find out whetherthe value of total weighted delay is good or not good.

For example:

Standard Indicator = [average priority]*[k*Average production cycle time]

Here k is a multiplication factor, which is nothing but the acceptable deviation aspercentage of average production cycle time.

5] Resource utilization: [Selected]


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The most common indicator used in practice is average resource utilization.

This indicator provides good overview of the shop performance.

The average resource utilization can be defined as:

[Resource utilization for all resources]Average resource utilization =

Number of Resources

6] Production Cost:

There can be multiple derivatives for calculating production cost and related

indicators. As at present, in Incoplan, only one cost parameter is defined,which is cost of resource usage, which in tern can provide a fraction of

production cost.

This value can be defined as production run cost or resource usage cost.The value can be defined as:

For all resources -

Resource usage cost = [Resource usage time*usage cost per unit time]

7] Q - Ratio: [Selected]


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The Q-ratio is also one of the good indicators about your schedule. This is

the ratio of work content to cycle time.

[Work content for all MOs]Q-ratio =

[Production Cycle time for all MOs]

There could be different methods, to calculate the terms defined in the

equation. Let us try to understand the meaning of these terms:

Take example of Green MO, in the following illustration:

Normally, following could be the guidelines: for value of the parameter-

Good Value between 1.00 and 0.75

Average Value between 0.75 and 0.50

Poor Value less then 0.50

8] Average WIP:

WCT1 WCT2 WCT3 WCT4

Production Cycle time


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The average WIP is being calculated on linear basis. For the current application

the idea could be to identify the event where inventory profile changes and takeaccount only these point to count and calculate average inventory.

The problem here is in Incoplan, we dont have information about value for these

inventories, and therefore it is difficult to measure shop wide average inventory,as unit of measure may not be same for all items.

It is possible to show the average inventory per item, but this information shall

not be of much use to the end user.

9] Time Ratio: [Selected]

There are numerous methods to define various ratios of time values, which

possibly evaluate the shop performance.

Ratio between following parameters can be defined

a] Total time Make spanb] Total set up time Sum of all set up time(s)

c] Total Run Time Sum of all run time(s)d] Total productive time Sum of all [internal setup+ run time]

e] Total unproductive Time Sum of all [external setup + move time]

Ratios those could be defined [some of them are as follows]

[Total Setup time / Total time] where set ups are important and costly too.

[Total run time / Total time] important for Capital Intensive Industry

[Total Productive time / Total unproductive time] general performance criteria


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There are many other parameters that can be defined. For example:

10] Total Penalty:

This is nothing but the multiplication of total delay and penalty per unit time, overall manufacturing orders those are scheduled.

11] Customer Service Level:

This criterion may very much helpful in todays competitive world. The question is

how to define an appropriate criterion for the evaluation.

The simplest solution could be to provide one parameter:

Number of Manufacturing Orders Delayed, orPercentage of Manufacturing Orders Delayed.

May be the second option is better.


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PRODUCT DESCRIPTIONManagement Information System

The Management Information System is a tool, which provides the symptoms of the

production system, to measure and evaluate identify the performance. Another use of thisManagement Information System is that user can compare two Simulations and / or

multiple simulations to identify the better Schedule and to know a priory the systembehavior.

1] Comparison of a Single Simulation:

The core idea behind comparison of single simulation is that user can find out the system

performance based on indicators or parameters defined. This provides values for thevarious parameters for the selected Schedule / Simulation.

The comparison of the single simulation shall be based on parameters defined. It shall

provide options to select one or multiple simulation parameters.


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The other option that could be given is:

The MIS shall provide different views, with reference to the options selected by the user.

One can visualize what graphics can be seen by the user, which is shown in the followingviews.

MO1 MO2 MO3 MO4 MO5 MO6 MO7 MO8 MO9

Single Simulation: Single Parameter [Delay] view per Manufacturing Order

The left side shows the contribution of individual manufacturing order in Total delay andright side shows the value of delay per manufacturing order.

Single Simulation Comparison

Single Parameter Multiple Parameters

Complete View [All Mos]

View per MO

View per Customer

View based on Parameters

Total Delay


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2] Comparison of a Multiple Simulation:

When user is comparing multiple simulations, he can have a wide flexibility to select theoptions, as primarily this is comparison of two or more simulations based on criteria

defined.

Again the options are with user to select a single parameter or multiple parameters for thesimulation comparison. If the user selects multiple parameters, it should be weighted to

produce a combined result based on relative importance of criterion selected by user.

The following view shows the actual view of simulation comparison for multiple simulations

and in the following example there are two simulations. The weights can be defined here.For example, in the view shown below, three criterions are selected, namely: Tardiness,

Lateness and Make span. User can select weight for each parameter between values zero

and hundred. This selection drives the process of calculating integrated result for thesimulations performed.

In this view, user can also see the individual simulations by exploring the left window for

each simulation. This helps to fine values for all parameters for a particular simulation.


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Other view that can be explored for future reference could be:

VIEW one:

This view compares the values for all parameters for all simulations, and in spite of this

provides a good vies for comparing individual values for parameter selected across allsimulations. And on the right side it provides, weighted combined value or Score for each

simulation.

The alternative view for this could be to show the weight selected for each parameter andcumulative values calculated for each simulation, using weight defined.


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This view is shown below:

Here, user can also select individual parameter to see the values for that parameter

across all the simulations.


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VIEW two:

This view provides the flexibility in terms of specific selection of the parameter and type ofgraph you would like to view. In the above example, user has selected only Total Delay

and Total Cost parameters to compare the simulations and in addition user has selectedLine chart as option.

Time

Cost

Performance

Total Delay

Make Span

Set up

Total Cost

Delay Cost

Utilization

No of MO delay

Bar Chart

Pie Chart

Line Chart

Chart TypeChart Type

ParameterParameter

GraphGraph

Simulations

Value

Total Delay

Total Cost


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Additional Parameters and comparison Methodology:

As the management is more or less interested in Economical performance of the factory, it

is quite essential to provide value added reports based on operating economics. Thesereports typically built on Cost and profit factors.

The cost are classified on two large segments:

Productive cost: Can be defined as any cost involving value addition on the product.

Non-productive cost: Can be defined as the cost which does not add any value to theproduct.

Management is typically interested in minimizing non-productive cost. The same

methodology applies to the time segment, as it can be clearly defined as productive andnon-productive times.

Display economic data translated into monetary terms:

Saving of X francs on the WIP, a saving of X francs on the set-up time: a manager istypically interested in economical data/figures! Refer also to the Excel file of Incoplanfeasibility (Ill send it to Sameer if he does not have it)

Display ratios of increase: for example:

The machine utilization rate has increased by X% per scenario

In addition to this, display the concept of optimization of performance: For example:Usage rate has increased by X, either percentage or actual values terms.

Setup time has reduced by X, either percentage or actual values terms.WIP has reduced by X %.

[All the above in monetary terms in francs and other currency]

Note: while translating into monetary terms, indicate the currency you are converting to!


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Global criteria for measurement:

1] Deviation with respect to the desired end date:Minimum deviation, average value, maximum deviation and standard deviation

(Variance = "standard deviation")

2] Weighted Analysis of the number of delayed MOs:This provides value of percentage Manufacturing order delayed over the totalnumber of manufacturing orders, to get the rate of service by filtering the MOs of

Finished products.

This is analysis of the number of days of delay of MOs: minimum, average and

maximum delay, standard deviation.

3] Analysis of cycle time:Calculate minimum, average and maximum with standard deviation.

4] Analysis of queues:

Calculate minimum, average and maximum with standard deviation.

5] Analysis of run-time compared with the cycle time:Calculate Minimum, average and maximum with variance [maximum minimum],

in percentage.

6] Analysis of the occupation time of machines: run-time as compared with free time:Calculate minimum, average and maximum, as a percentage.

7] Analysis of the setup time in comparison with run-time:

Calculate minimum, average and maximum as percentage.

8] Comparison of total working days against total days in make span:

Provides information about percentage working days over a horizon.

9] Number of days of delay in percentage, as compared to the total number of days,which is nothing but make span for that manufacturing order.

This can be calculated for each MO and can also be calculated for group of MO.This is a good indicator of Service Rate.

10] Time gained in setup grouping:Provides value for time saved for setup because of grouping of work tickets, in

absolute value and in percentage of total setup time for the schedule.

11] Value of a simulation:This is essentially the Cost of production for a particular simulation / schedule.

simulation comparison parameters-final

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