Class Document-extended introduction

Wroclaw University of Technology, Faculty of Mechanical Engineering

Simulation of Production Processes

Course tutors: PhD Eng. Arkadiusz Kowalski MSc. Eng. Michał Olejarczyk MSc. Eng. Andrzej Pawlak

Simulation of Production Processes - Course schedule INTRODUCTION EXERCISE 1

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Deterministic model – determination of arrival frequencies

EXERCISE 2

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Model evolution - Heat Treatment process

EXERCISE 3

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Model evolution – Quality control

EXERCISE 4

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Introduction to production plan diversification

EXERCISE 5

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Model evolution – Assembly process

EXERCISE 6

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Definition of different transport modes, and costs

EXERCISE 7

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Symulation of nondeterministic production plan model

EXERCISE 8

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Definition of downtimes during work and macros definition

EXERCISE 9

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Definition variables and attributes characterizing analysed manufacturing system

EXERCISE 10

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SimRunner software, first optimization

EXERCISE 11

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SimRunner software, second optimization

Introduction Building a simulation model in the ProModel environment consists of the following steps, corresponding to the modules available from the Build menu: Selecting the types of machines and other stations, where manufacturing processes will be run. (Locations), Defining the product (Entities), Adding the path of work (Path Networks), Determination of productive resources (Resources), Creating the process logic (Processing), Scheduling tide products. (Arrivals). Before creating a new model, you have to define the time and distance units as well as the Graphic Library to be used in your simulation (menu File/New/General Information or Build/General Information). There you also have the possibility to introduce logic conditions, which support the initiation and termination of the simulation process. This interface does not save your model, so make sure to save your file before commencing (menu File/Save As).

Fig. 1. Dialog box when opening a new model Another consideration before starting is the option to either create your own personal background upon which the system is going to be built (menu Build/Background Graphics/Front of Grid or Build/Background Graphics/Behind Grid) or import a graphic file (Edit/Import Graphic), ending in: *.bmp, *.pcx, *.gif or *.wmf. Next the grid parameters (View/Layout Settings/Grid Settings) should be determined, to match the spacing between grid lines with the real-world or predefined spacing.

Module Locations (picture below) allows the representation of the physical workstation, which will carry out technological operations and procedures, or where decisions are taken. Workstations are placed in the system simulation by selecting them from a graphical menu and inserting them into the

Layout window. The distances between Workstations are defined in the next steps. It is possible to describe devices that you insert and edit or scale them. Background image can represent, for example the modelled system.

Graphics library of machines and equipment can be extended with your own machinery and equipment, transport means using graphics editor (Graphics Editor). Parameters defining the machinery and equipment included: Icon, Name, Capacity, Units, DTs, Stats, Rules, Notes are located in the window Locations. Option Icon shows the icon used for the graphical representation of the working area during the simulation, the column Name contains its name. Capacity allows you to define performance of a machine (understood as the quantity of items, which also are subject to manipulation). Units option specifies the number of identical work places, and Stats generates statistics of different types (Time Series is the most detailed kind of statistics). Using the editor’s time breaks and exclusions DTs allow you to specify the times and conditions under which a temporary exclusion is to take place during the simulation machine. Here is used tpz time as the setup time (Setup downtimes). Define rules for incoming and outgoing parts of production equipment in the Rules window. There are listed possible ways of choosing items that are pending at the entrance: the oldest priority, random, the smallest available capacity, while at the exit can set the following priorities: no queues, FIFO, LIFO, "after the type." Module Entities (elements, units), which during the simulation process are the subject of action or decision taken, for example, product components, assemblies, products. We define the elements to transport the technology manipulation.

After selecting the graphic elements library you can edit the selected item and make changes such as its size. Options describing introduced elements: Icon, Name, Speed, Stats, Notes. Options Icon and Name clearly define an element in the system, Speed - the default speed at which items will be moved over the network (mpm - meter per minute, fpm - feet per minute). Path Network – path, the road along which production resources are moved. Is built using the mouse, double clicking allows you to create more network nodes. Options to create a network: Graphics, Name, Type, T / S, Path, Interfaces, Mapping, Nodes. To identify pathways in the system simulation the Graphics column is used (colour of the road) and Name. By selecting Type you can choose the type of the proposed network (Non-Passing, Passing, Crane), and column T / S type of unit in which the parameters of traffic in the created network. Location of equipment introduced from the keyboard as individual distances between network nodes - Path option.

The next step is to create interfaces between the network nodes and the various production units by selecting Interface and clicking on the node and then the selected work place. Interfaces allow the connection of network and equipment located on the modelled industrial hall. Mapping option determines the order of movement along the network, its branches, Nodes allows you to add additional nodes. In the module Resources we can select production resources, i.e. means of transport, staff and auxiliary tools and instruments. The parameters of any production are: Icon, Name, Units, DTs, Stats, Specs, Search, Logic, Points. Icon and Name options allow you to identify resources in the manufacturing system. Units option specifies the number of identical resources, DTs editor allows you to specify downtimes, Stats allows you to select the type of created statistics.

The next step is to attach the means of transport to the previously established network of movements in the options window of Specs (Specifications). We define the traffic speed of transportation resources with or without loads, accelerations, times, lifting and assembly of objects transported. Logic option allows you to add logic to move resources across nodes. With the help of Pts (Points) you can determine the location of graphics on the screen representing the productive resources at the time of their arrival at the specified node. The module Processing (technological process) defines the operations that take place on the selected workplaces and production resources required of these operations. Should also indicate the next workplace, for which there is a need to move the manufactured item to.

The first step to describe the technological process is to select the object in the Tools window, which will be subjected to machining processes. Then, indicate (by clicking in the window Layout) position (work place), which will be used for technological operation, then place another operation. To determine the time of operations and procedures, that production resources needed to carry out, click on the Operation bar... in the Processing window. In the wizard, select the commands needed to implement the process commands in the next popup window, give the necessary parameters and attributes, and paste the obtained form of order. After determining the details of the modelled operations, define the routing technology and the manner of movement produced by the system elements and production resources. To do this, click on the Move Logic bar in the window Routing for. A window will open where you can enter commands from the keyboard or to run the wizard. In the wizard, select resources and create logic of movement, and paste the obtained form of order. The module arrival (delivery schedule) refers to the supply plan for the workpieces.

First, in the Tools window select the object for which we set the parameters of supply at the entry to the system. Clicking on the Location... allows you to specify the place of batch delivery, Qty each... number of items in the series, First Time – The time of appearance of the first items upon the system’s entry, Occurrences – the number of batches, Frequency – the frequency of deliveries of batches of materials. Logic option allows you to add conditions to provide the next batch of materials and objects for processing, Disable allows the suspension of a process to provide lots of materials to the system.

Simulation and Final Report Among the options for the simulation (Simulation menu/Options) the available options are: length of the simulation being conducted, the accuracy of the system clock, types of the final report being generated. You can also enable / disable the display of graphics during the simulation, cost calculation, a pause at the start of the simulation. Animation speed can be adjusted by moving the slider located at the top of the screen. Following that, we can see the final report of the generated simulation.

The final report includes extensive statistics on all components of the modelled system. The simulation results are presented in the following groups: LOCATIONS [workplace], the name of the job, hours worked, volume, number of inputs, average time per entry, the average content, the maximum content, current content, the percentage of load. RESOURCES [Resources] resource name, units, hours worked, number of operations performed, the average time of use, the average transport time for operation, the average transportation time "to break", blocked in transport %, utilization %. FAILED ARRIVALS [Supply], which has not been delivered, name of the item, the workplace name, all items lost. ENTITY ACTIVITY [entity states] entity name, the number off each one, current number in the system, average time in the system, average time of transportation, average time of waiting for resources, average operation time.