AMS 2022 – Experiment Material
PUSH & PULL
< Experiment result & analysis >
1. Report on simulation result for each model.
Order waiting time
product CT
product WIP
PUSH
PULL
2. A total of 4 Hold modules are used to implement the Pull system. Explain in detail what the
operating mechanic is.
< Discussion & conclusion >
(1) List as many the ways as possible that a company can set the WIP upper bound.
(2) Why is a Pull system more robust than a Push system? What practical results does this have on
the manufacturing floor?
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2022 Spring AMS Experiment Lecture note
Analysis of Manufacturing Systems
Experiment
Push and Pull
Intelligent Manufacturing Systems Lab
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2022 Spring AMS Experiment Lecture note
1. Experiment Overview
■ Title
Comparing PUSH and PULL system in production system
■ Objective
•
Understand the concept of PUSH and PULL system
•
Measure and compare the order waiting time, CT, WIP for each system
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2. Theoretical Background
■ Basic Terminology
•
PUSH systems schedule work releases based on demand, and PULL systems authorize
work releases based on system status.
•
In PUSH systems, a job is entered into the production process when it is required by
the work releases. The timing of input does not change depending on the process.
•
In PULL systems, a job is allowed to enter into the shop floor only when a signal
indicates that the changes in a production line occurs. The signal shows if a certain
job is finished in a production line like Kanban.
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3. Experiment Design
Yonsei Co. has a production line with 3 stations, and each machine processes one product at a
time. Information of each station is given below.
Workstation 1
Workstation 2
Workstation 3
# of Machine
(Resource Capacity)
1
1
1
Processing Time
EXPO(4)
min/job
EXPO(3)
min/job
EXPO(4)
min/job
Simulation runs for 1000 minutes, and for system stabilization and statistic accuracy, set warm-up
time as 100 minutes.
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4. Experimental Procedure
(1: push case)
■ Step 1-1. Creating a simulation model and resources setting
•
Basic simulation model is as the picture shown below
•
Modules used: 2 Create, 3 Process, 2 Assign, 1 Batch, 1 Separate, 1 Decide, 2 Dispose
Push Model
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4. Experimental Procedure
(1: push case)
■ Step 1-1. Creating a simulation model and resources setting
•
Click the resource icon in the Basic Process Panel, and ass resource by double-clicking
Module Settings UI.
•
Set up name and capacity (station ID and #of machine) of each resource (machine).
※ Capacity data Slide 4의 Table 참조
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4. Experimental Procedure
(1: push case)
■ Step 1-2. Create module settings (Double-click Create module)
•
Create module creates the entity going into the production system, and Yonsei Co.
has two different kinds of entity: raw material and order.
•
Time Between Arrivals sets the input rate of entity, and the values will be changed for
the further experiments. (1st Create: Raw material, 2nd Create: Order release)
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4. Experimental Procedure
(1: push case)
Step 1-3. Assign module settings (Double-click Assign module)
■
•
Place Assign modules for raw material Create module and order Create module
•
For raw material Assign module, define and add one variable and one attribute.
•
Remember that this is the process to match the order number and the product number.
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4. Experimental Procedure
(1: push case)
■ Step 1-3. Assign module settings (Double-click Assign module)
•
For order Assign module, define and add one variable and one attribute.
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4. Experimental Procedure
(1: push case)
■ Step 1-4. Process module settings (Double-click Process module)
•
Define 3 processes, and details are shown below.
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4. Experimental Procedure
(1: push case)
■ Step 1-5. Batch module settings (Double-click Batch module)
•
Set up Batch module as shown below, Batch size is 2.
•
When order comes in, it matches a manufactured product at that moment to the
order number and leaves the system as a batch of a order and a product.
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4. Experimental Procedure
(1: push case)
Step 1-6. Separate module settings (Double-click Separate module)
■
•
Separate module splits an order and a product which are batched together from the Batch
module.
•
It is a technical step to calculate the number of the order and products, and settings are
shown below.
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4. Experimental Procedure
(1: push case)
■ Step 1-7. Decide module settings (Double-click Decide module)
•
Decide module divides the order entity and product entity
•
As a result, order waiting time, product cycle time, system WIP information will be
shown in the report for each entity
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4. Experimental Procedure
(1: push case)
Step 1-8. Run Setup
■
•
100 minutes of Warm-up Period for system stabilization, 1000 minutes of actual simulation
time, total of 1100 minutes of the run time. (Run Tab Setup Replication parameters)
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4. Experimental Procedure
(2: pull case)
Step 2-1. Creating a simulation model and resources setting
■
•
Basic simulation model is as the picture shown below (Raw 1~3 & Finished goods module
= Hold module)
•
The system is divided into two parts where generating an order and actual production.
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4. Experimental Procedure
(2: pull case)
■ Step 2-2. Create module settings (Double-click Create module)
•
Create module has a setting similar to the PUSH case.
•
Time between arrivals of the raw material is changed to 1 minute.
(1st Create: Order release, 2nd Create: Raw material create)
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4. Experimental Procedure
(2: pull case)
■ Step 2-3. Assign module settings for order
•
Assign the attribute “number” to the order entity.
•
Once again! Remember that this is the process to match the order number and the
product number.
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4. Experimental Procedure
(2: pull case)
Step 2-4. Decide module settings (process of actual PULL production)
■
•
Arena is time-based simulation which cannot produce an entity with signal or specific condition,
so modeling of the PULL system is implemented in front of the actual production.
•
Raw material entity is moving to the buffer in front of the first process, assume that first
buffer(Raw 1) to arrive can only have less than 30 of the raw material.
•
Type in the constraint for Raw 1.Queue in Decide module.
•
Buffer in front of each process will be presented using Hold module (advanced process).
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4. Experimental Procedure
(2: pull case)
Step 2-5. Assign module settings for raw material
■
•
If queue of Raw 1 is less than 30, raw material entity is assigned with the attribute value.
•
Variable and attribute is defined and added to Assign 2 module just like Assign 1 module.
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4. Experimental Procedure
(2: pull case)
Step 2-6. Hold module settings
■
•
Buffer of each station is represented with the Hold module.
Due to the nature of the PULL production to transfer the entity in the buffer by the certain condition or
the signal.
Hold module is set up as shown below, and proceed with this process when process 1 is idle and
buffer(Raw 2) in front of the next process does not have any entity waiting.
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4. Experimental Procedure
(2: pull case)
Step 2-7. Assign module settings (Raw material Product)
■
•
Through Step 2-6 set up for the PULL system, CT and WIP of the actual production system needs
to be measured from this point.
•
Using the settings shown below to replace the entity from the raw material to product, and assign
TNOW value to measure the actual production time.
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4. Experimental Procedure
(2: pull case)
■ Step 2-8. Process module settings
•
Define 3 Process, and use simply Delay as action.
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4. Experimental Procedure
(2: pull case)
Step 2-9. Hold module settings
■
•
After Process 1, entity waits at Raw 2, and move on when process 2 is idle and buffer(Raw 3) in
front of the next process is empty.
•
After Process 2, entity waits at Raw 3, and move on when process 3 is idle and inventory of the
finished product is less than or equal to 5.
•
Completed entity waits at the Hold module “Finished goods” for an order, and it is processed
when an order entity arrives at the Batch module.
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4. Experimental Procedure
(2: pull case)
Step 2-10. Batch module settings
■
•
Order with an attribute assigned is sent to the Batch module, and it is processed right away if
there is a finished product, otherwise it waits at Batch module’s queue for a product to be finished.
•
Batch module is set up as shown below, and Batch size is 2.
•
It is to match a produced good with its order number at the moment of the order, and an order
and a product is bundled into one batch.
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4. Experimental Procedure
(2: pull case)
Step 2-11. Separate module settings
■
•
Separate module separates the bundle of an order and a product formed in Batch module.
•
It is a technical step to calculate the number of the order and products, and settings are shown
below.
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4. Experimental Procedure
(2: pull case)
Step 2-12. Decide module settings
■
•
To measure the CT of a product from inputting into the actual production until order is
processed, use the Decide module to separate the entity with entity type as product.
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4. Experimental Procedure
(2: pull case)
Step 2-13. Record module settings
■
•
TNOW for each entity assigned before passing Process 1 is used to calculate the Time
interval and record the Total product time.
•
Entity finished with recording time is disposed.
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4. Experimental Procedure
(2: pull case)
Step 2-14. Run Setup
■
•
100 minutes of Warm-up Period for system stabilization, 1000 minutes of actual simulation
time, total of 1100 minutes of the run time. (Run Tab Setup Replication parameters)
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Q&A
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