Manufacturing Cm Simplified

8/9/2019 Manufacturing Cm Simplified

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Manufacturing M&S Project, Simplified

Problem DescriptionProblem Statement

In a manufacturing plant, management is interested in automating the loading/unloading of components

into/from three machines as well as the movement of components between the machines with power

roller conveyors. Two conveyors unload components from the first machine, one for each of 2 types ofcomponent, and move the components for loading into two other machines (that each process one of the

component types). The length of these conveyors is limited and can lead to downtime in the first

machine when one of the conveyors becomes full.

Since lengthening the conveyors increases cost, management wishes to keep the lengths as short aspossible but maintain minimal downtime of the first machine.

SUI Details

A department in a manufacturing plant processes two streams of partially completed components (A and

B) using three different machines. The plant operates 24 hrs/day, 7days/week.

Plant Components and Resour ces

Components: The manufacturing plant process to types of components: A and B.

Machines: Three machines are used to process the components. Machine M1 processes both types ofcomponents, while machine M2 processes only type A components and machine M3 processes only

type B components. Figure 1 shows the layout of the three machines used to process the components.

Figure 1Current Layout of the Plant

A B

M1

M2

M3

B BA

A

A

B

A

B

B


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Conveyors: Power roller conveyors are being added to automate the loading/unloading of components

and moving components to and from the machines to improve throughput. Figure 2 shows the layout of

the plant with conveyors.

Figure 2Layout of the Plant with Power Roller Conveyors

Employees: Three employees are responsible for moving and loading components into the machines.

Processing Components

The components are first processed at machine M1 and upon completion each type of component flowsinto two separate paths so that A components are processed at machine M2 and B components are

processed at machine M3.

Current Operation: Moving components, loading components into machines and unloading

components out of the machines is done manually and currently the responsibility of 3 employees.

1) One employee is responsible for moving arriving components into machine M1. When themachine M1 has completed its operation the employee replaces the component with another (if

available) and the moves the component to machine M2 or M3 according to its type.

2) A second employee is responsible for Machine M2. When a type A component is available, the

employee loads machine M2 with the component and removes it when the machine hascompleted its processing and places it in pickup area.

3) A second employee is responsible for Machine M3. When a type B component is available, the

employee loads machine M3 with the component and removes it when the machine hascompleted its processing and places it in pickup area.

Operation with Conveyors: Conveyors for augmenting throughout will move components betweenmachines and load/unload components to/from machines automatically. The role of employees are to

load components onto the conveyor that brings components to machine M1 and remove components

from the conveyors that unloads components from machines M2 and M3. Thus one employee is

dedicated to load the conveyor leading to machine M1, while the other two employees unload the

conveyors moving components away from machines M2 and M3.The conveyors between machine M1 and machines M2 and M3 are of limited length. When one of

these conveyors is full, a component in machine M1 destined for that conveyor will remain in the

machine after processing until space becomes available in on the conveyor. This prevents furtherprocessing in machine M1 and slows down component processing.

M1

M2

M3A

A

B

BABBA

A

BB

B

A


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Project Goal

The goal of the simulation project is to determine the length of the conveyors between machine M1 and

the two machines M2 and M3 that minimizes the downtime for machine M1.

Parameters Q.Conveyors[M2].length: The maximum number of components the conveyor leading to

machine 2 can hold (3 to 10).

Q.Conveyors[M3].length: The maximum number of components the conveyor leading to

machine 3 can hold (3 to 10).

Experimentation

Study: Steady state study.

Observation Interval:

Time units areminutes

Cannot be predetermined because a steady state study is required

Experimentation: The length of each conveyor leading to machines M2 and M3 is initially set to 3components and can be lengthened to accommodate up to 10 components. The length of each conveyor

is increased using the following strategy.

Initially set the length of the conveyors to 3 components and use experimentation to determinethe percentage of time each conveyor is full and machine M1 is down.

The length of the conveyor with the largest percentage of time full in increased to accommodateone more component and a new experiment undertaken.

Experiments are repeated until the downtime of M1 less than 10%.

Output

percentTimeC2Full, percentTimeC3Full:Percentage of time conveyor between M1 and M2(Q.Conveyors[M2]) is full, and percentage of time the conveyor between M1 and M3

(Q.Conveyors[M3]) is full, respectively. This output is used to increase the length of eachconveyor between experiments and facilitates experimentation.

percentTimeDown: Percent of time M1 is down: Downtime is measured as the percentage of

time M1 contains a component and is not working (the component cannot be moved out of the

machine). Note that the machine with no component and not working is not considered to bedown.


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ABCmod Conceptual Model

High Level Conceptual Model

Simplifications

Employees are not modelled given that the focus on the study in on the length of the conveyorsbetween machine M1 and the other 2 machines.

The conveyor that brings components to machine M1 can be modelled as having an unlimited

length, given that an employee will feed any arriving components when space becomes free on

the conveyor.

Conveyors that remove components from machines M2 and M3 are not modelled. Given thatemployees are constantly removing components from these conveyors, it is not expected that theconveyors can become full. Thus when either machine finishes with a component, the

component is assumed to leave the SUI.

The time for conveyors to move components to the machines are considered negligible.

Structural View

Figure 1 Manufacturing Structural Diagram

Entity Structures1. iC.Component: represents the components processed by the department. The attribute type identifies

the component type (has a value ofAorB).

2. R.Machines: The set of machines that process the components. The symbols M1, M2 and M3 arethe identifiers of each member of the set. Thus the identifiers of the entities representing the

machines are:

a. Machine M1: R.Machines[M1]

b. Machine M2: R.Machines[M2]c. Machine M3: R.Machines[M3]

3. Q.Conveyors: The set of queues represent the three conveyors that feed each of the machines. The

symbols M1, M2, and M3 are also used to identify the members of the set. The queueQ.Conveyors[M1] represents the conveyor leading to machine M1 and has an unlimited length, sincean employee continuously feeds the conveyor when any components are available and space is

available on the conveyor (in fact the queue represents the conveyor and all components in the

department ready for processing by machine M1). The other two conveyors, Q.Conveyors[M2] andQ.Conveyors[M3], represent the conveyors that move components from R.Machines[M1] to

R.Machines[M2] and R.Machines[M3] respectively. The lengths of these queues are limited and

defined by parameters Q.Conveyors[M2].lengthand Q.Conveyors[M3].length.

Q.Conveyors[M1]R.Machines

[M1]

Q.Conveyors[M2]

Q.Conveyors[M3]

R.Machines

[M2]

R.Machines

[M3]

iC.Component

Legend


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Behavioural View

Component Lifecycle Machine M1 Lifecycle

Figure 2Manufacturing Behavioural DiagramScheduled Action Constructs:

CompArrivals: Arrivals of components to the department.

Conditional Action Constructs:

MoveCOutOfM1: This conditional action moves a component out of machine M1 when spaceis free in one of the conveyors M2 (if component in the machine is of type A) or M3 (if

component in the machine is of type B). The use of the conditional action are required since it is

possible that at the end of this activity, the component will remain in R.Machine[M1] becausethe destination conveyor (queue) is full. Machine M2 only processes A components while

machine M3 processes only B components.

Activity Constructs:CompProcessing: Processing of components at any of the three machines. In the case of

processing the component in machine M1, this activity does not move the components out of themachine. The conditional action performs this action when space is available on the appropriate

conveyors. For machines M2 and M3, the component leaves the system once processing is

completed (shown in the component life cycle diagram)

CompArrivals

CompProcessing

CompProcessing

MoveCOutOfM1

(Processing in

R.Machines[M1],

component left in

machine)

(Moves component onto

Q.Conveyors[M2] or

Q.Conveyors[M3]

(Component processing

in R.Machines[M2] or

R.Machines[M3])

CompProcessing

MoveCOutOfM1


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Input

Exogenous Input (Entity Streams)

Variable Description Domain

Sequence

Range Sequence

uCArr Input entity stream variable of

components.

RVP.DuArr() N/A1 component

arrives at eacharrival time.

Endogenous Input (Entity Streams)

Variable Description Values

iC.Component.uType The type of component that is

set upon arrival of the

component.

RVP.uCompType()

uProcTimeM1 Processing times for machine

M1. Dependent on the

machine type, A or B.

RVP.uProcTimeM1(type)

uProcTime Processing times in machine

M2 and M3. The time isdependent on the machine.

RVP.uProcTime(machine)


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Detailed Conceptual Model

Structural Components

Constants

Name Description ValueM1, M2, M3 Identifier for set categories R.Machines and

Q.Conveyors. The identifiers serve to

associate each Q.Conveyors entity to a

R.Machines entity/

0, 1, 2

Parameters

Name Description ValueQ.Conveyors[M2].length The maximum number of components that

the Q.Conveyor[M2] can hold.

3 to 10

Q.Conveyors[M3].length The maximum number of components that

the Q.Conveyor[M3] can hold.

3 to 10.

Consumer Class: Component

Components processed by the department.Attributes Description

type Set to A or B to reflect the type of component.

Resource Set[3]: MachinesThe 3 machines in the system. M1, M2 and M3 are the three identifiers of the machines.

Attributes Descriptionbusy Set to TRUE when the machine is processing a component and FALSE

otherwise.

component References a component entity being processed. Set to NOCOMP to indicate

component is not present in the machine (for machine M1).

Queue Set[3]: ConveyorsThe three conveyors in the model. M1, M2 and M3 are the three identifiers of the conveyors.

Attributes Descriptionn The number of components on the conveyor.

list The list of component entities on the conveyor.

length The length of the conveyor. The attribute is used for R.Conveyors[M2] and

R.Conveyors[M3]. The R.Conveyors[M1] is assumed to have an infinite

length.

Behavioural components

Time units: minutes

Observation interval: Steady state study determined during experimentation.

Action: Initialise

TimeSequence < 0 >

Event SCS FOR ix in M1 to M3

R.Machines[ix].busy FALSE

R.Machines[ix].component

NOCOMP

Q.Conveyors[ix].N 0

ENDFOR


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Action: Initialise

(the length attributes are assumed to be set)

Output

OUTPUTSTrajectory Sequences

Name DescriptionTRJ[M1Down] Trajectory set reflects the time that machine M1 is down. M1Down is 1 when

R.Machines[M1].busy is FALSE and R.Machines[M1].component is not NOCOMP and 0

otherwise.

TRJ[TimeConv2Full] Reflects the time that Q.Conveyors[M2] is full, that is, Q.Conveyors[M2].n =

Q.Conveyors[M2].length.

TRJ[TimeConv3Full] Reflects the time that Q.Conveyors[M3] is full, that is, Q.Conveyors[M3].n =

Q.Conveyors[M2].length.

Derived Scalar Output Variables (DSOV's)

Name Description Data Set Name OperatorpercentTimeDown Percentage of time the machine M1 is down. TRJ[M1Down] Average

percentTimeC2Full Percentage of time the conveyor leading to

machine M2 is full.

TRJ[TimeConv2Full] Average

percentTimeC3Full Percentage of time the conveyor leading to

machine M3 is full.

TRJ[TimeConv3Full] Average

User Defined ProceduresUser-Defined Procedures

Name Description

ConveyorReadyForComp() Returns the identifier of the Q.Conveyors set into which the component from

R.Machine[M1] can be moved into. The following conditions must be met to move a

component:

1)

R.Machines[M1].busy is FALSE

2)

R.Machines[M1].component must reference an iC.Component entity (i.e. not

NOCOMP).

3)

Space is available for on the conveyor for the component, either:

a.

R.Machines[M1].component.type = A (i.e. an A component is in the machine)

and Q.Conveyors[M2].n is less than Q.Conveyors[M2].length OR

b. R.Machines[M1].component.type = B (i.e. a B component is in the machine) and

Q.Conveyors[M3].n is less than Q.Conveyors[M3].length

If 3a is true, return M2, if 3b is true, return M3, otherwise return NONE (no component

can be moved).

MachineReadyForProcessing() Returns the identifier, id, of a member of the R.Machines category under the following

conditions:

1) R.Machines[id].busy is false

2) Q.Conveyors[id].n is non-zero

3) R.Machines[id].component is equal to NOCOMP

If no machine is ready for component processing, NONE is returned.


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Input Constructs

Random Variate Procedures

Name Description Data ModelDuCArr() Returns the next arrival time for a

component. Assumes that an arrival

has occurred at current time t.

t + Exponential(MEAN_INTER_ARR)

where

MEAN_INTER_ARR = 7.0 minutesuCompType() Returns the a component type A or

B.

Returns A, PERCENT_A of the time

Returns B, PERCENT_B of the time

Where PERCENT_A = 0.55, PERCENT_B = 0.45

uProcTime(machine, type) Provides the processing times for

machines M1, M2 and M3; machine

has one of the id values M1, M2, or

M3. The processing time for M1 is

dependent on the component type

given by type (set to A or B)

Machine is M1 and

typeis A: Exponential(MEAN_PROC_TIME_M1_A)

typeis B: Exponential(MEAN_PROC_TIME_M1_B)

where

MEAN_PROC_TIME_M1_A = 2.1 minutes

MEAN_PROC_TIME_M1_B = 4.2 minutes

machineis M2: Exponential(MEAN_PROC_TIME_M2)

machineis M3: Exponential(MEAN_PROC_TIME_M3)

where

MEAN_PROC_TIME_M2 = 9.4 minutes

MEAN_PROC_TIME_M3 = 10.5 minutes

Action: CompArrivalsArrival of A component.

TimeSequence RVP.DuCArr()

Event iC.Component SP.Derive(Component)

iC.Component.type RVP.uCompType()

SP.InsertQue(Q.Conveyors[M1], iC.Component)

Behavioural Constructs

Activity: CompProcessing

Processing components at any of the machines. The UDP.MachineReadForProcessing() determines whichmachine can start processing. Processing consists of removing a component from the Q.Conveyors[id] leading to

the machine, processing the component (duration determined by RVP.uProcTime(), and removing the component

from the machine. In the case of machines M2 and M3, the component leaves the system after processing. In the

case of machine M1, the component is left in the machine for removal by the conditional action.

Precondition UDP.MachineReadyForProcessing() NONE

Event id RVP.MachineReadyForProcessing()

R.Machines[id].busy TRUE

R.Machines[id].component Q.RemoveQue(Q.Conveyors[id])

Duration RVP.uProcTime(id, R.Machines[id].component.type)

Event R.Machines[id].busy FALSE

IF(id M1) THEN (Conditional action will remove component from machine M1)

R.Machines[id].component NOCOMP

SP.Leave(R.Machines[id].component)ENDIF

Action: MoveCOutOfM1Moving a component out of M1 when processing is complete and space is available on conveyor that

is to receive the component.

Precondition UDP.ConveyorReadyForComp() NONE

Event qid UDP. ConveyorReadyForComp()

SP.InsertQue(Q.Conveyors[qid], R.Machines[M1].component)

R.Machines[M1].component NOCOMP


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Annex AData Modelling

Data collection and analysis has been completed for the project with the following results.

Interarrival times for components are exponentially distributed with the following means:

o

A components: 12.7 minuteso B components: 15.4 minutes

o These have been revised to provide interarrival times for all components and a data

model for the type of the arriving component below.

Processing times in each machine are also exponentially distributed with the following means:

o Machine M1, A component: 2.1 minutes

o Machine M1, B component: 4.2 minutes

o Machine M2: 9.4 minutes

o Machine M3: 10.5 minutes

Time for moving components on the conveyors take only a few seconds.

Data model for Interarrival Time of Components

Only a single input entity stream is to be modelled with a second data model for the data type. Thus the

interarrival times are modelled as exponentially distributed with a mean of 7.0 minutes.

Data model for Component Types

Distribution of types for arriving components are as follows: 55% Type A Components, 45 % Type B

components.

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Manufacturing Cm Simplified