Here Is What We Do...
What Is A Simulation Model?
A simulation model is a model, built on a computer, which represents a system or a process. Most simulation models have a graphical animation (preferably 3-D) representing what is modeled. Simulations are built using a simulation software package such as Simul8, SLX, GPSS, Witness, or AutoMod (our preferred package). A highly detailed simulation will accurately reflect what is modeled in order to make simulation runs or experiments to predict system performance and behavior.
Our discrete event simulations are developed with the AutoMod Software by Brooks Automation. This software allows a 3-dimensional animation to be created incorporating system characteristics. Data regarding customer throughput, volume and timeframes are incorporated to develop a working demonstration of system performance.
There is literally no limit to what can be simulated. Usually costly material handling or manufacturing systems are good candidates for simulation. The modeling efforts allow a system to be built and tested on a computer at a minimal cost compared to putting actual equipment out on the floor and testing it. Some examples of the types of systems for simulation modeling are explained below.
- Parts Production
- Operator or automated work cells
- Assembly processes
- Assembly systems
The simulation modeling of manufacturing systems is beneficial in determining and experimenting with production throughput capabilities. The systems capability for Jobs Per Hour (JPH) is key and simulation modeling will help in ensuring the highest rate of production for your system.
- Distribution centers
- Postal sortation
- Parcel and freight
- Storage and retrieval
Pieces Per Minute (PPM) is the key with these types of systems. Simulation modeling will help in creating smooth and balanced system operations. The system flow is tested and tweaked to ensure a high rate of system utilization during processing times. When a typical simulation model is built it will be based on actual system layouts, operations, and controls. The model will behave as the system does. The models can use real world data for a thorough analysis.
A 3-dimensional model is built that incorporates the system behavior from conveyor speed to controls algorithms. The model is built to scale and will accurately reflect hardware characteristics such as speed, space and rate. When real world data is plugged into a simulation we get real world results.
The Purpose of Simulation Modeling
The purpose of simulation modeling is to reduce risk and costs through efficient and accurate system installations that do not require expensive modifications when the systems are supposed to have already been up and running. Simulations serve a constructive purpose through the entire cycle of a system's life; from the original concepts to the observation of daily operations of an installed system. A proper simulation can be used for the testing of concepts or designs; providing animations of systems; examining systems operational characteristics or performing experimentation.
The role of simulation modeling can be divided in the three essential categories of Sales and Conception, Design Verification, and Experimentation.
- Emphasis on animation
- Animation allows proposed system to be seen in action
- A clear understanding of the system can be derived
- Proven concepts can be shown
- A rough verification can be performed on system design
- Highly detailed simulation model
- Emulates the system design and control to be as close to actual as possible
- Allows the system design to be tested to verify that it will meet throughput goals
- Statistics can be gathered on almost any aspect of the system ranging from overall throughput to specific machine or resource utilizations
- Actual data and schedules can be incorporated in simulation model
- The most valuable portion of a simulation study to customer and system design engineers
- "What if" scenarios can be built into the base simulation model
- Sensitivity analysis for equipment (sort machines, buffers, accumulation)
- Effects of changes in system design or control may be studied and viewed
- A user interface can be developed to allow easy manipulation of model input data and chart separate model results
The value of a valid and proper simulation model is priceless. When a system is run and understood via a simulation model it will save time and money for the system vendor and user. Having the right staff to build a simulation is the key. With the experience of PSC, you get that staff.
Simulation Model Development Methodology
The methodology used for simulation model building generally follows a four phase process. Each simulation project may have different goals in the overall scope of work, but Base Simulation model development is usually derived from the four phase process methodology. This process will ensure an accurate simulation model is created.
Phase 1 - Pre Model Activity
- Kick off meeting
- Definition of system goals
- Simulation scope of work
- List of clarifications and assumptions
- Develop functional specification
- Create data simulation to prove overall concept
The kickoff meeting is used to detail the goals that the simulation will accomplish. The Simulation Consultant, Systems Engineers, and Project Managers usually attend this meeting. The system is reviewed in detail and a scope of work is determined for the simulation effort.
A functional specification is then developed to outline goals of the simulation and to define modeling parameters. A description of operations, modeling assumptions, data requirements and definition are the core of the functional specification. A list of simulation deliverables is also included in the specification. The participants mentioned above approve the document to establish a common understanding for all involved in the project.
If appropriate, a data model is created. The data model will test volumes and processes. This is the first step in detecting operational or process difficulties. The data model is also a useful verification tool for the overall simulation model to test against.
Phase 2 - Base Simulation Model Development
- Convert AutoCAD drawings to an AutoMod format
- Input Graphics into AutoMod
A. Define and draw conveyor path
B. Create resources
C. Create product appearance
D. Input labels
E. Input robots – OPTIONAL
F. Define operators and walk paths – OPTIONAL
- Programming of AutoMod Simulation
A. AutoMod creation process
B. Read product arrival profiles
C. Function of resources and their processing rates
D. Emulate "Sequence of Operations"
E. Develop system scheduling (arrival & dispatch profile, personnel scheduling)
- Simulation Model Validation
A. Examine system throughput
B. Validate system with system design engineers
C. Uncover and expose possible errors in the simulation model
- Incorporate any changes required
The most challenging and time consuming process of simulation model creation is the actual programming. This is the point where all data and assumptions are applied to the system layout to determine validity of the design. If changes are required after a review of the simulation model inputs, they are implemented and Phase 3 begins.
Phase 3 - Simulation Model Analysis
- Conduct simulation model runs
- Examine throughput values
A. Interpret data
B. Verify output
- Collect data produced by model run
A. Create spreadsheets and graphs
B. Pinpoint system bottlenecks or starvation
- Create Simulation Report
This is the phase of the overall simulation procedure where the model is ready to be run. The model can simulate running the product through the system over a period of days. The period of time that the model simulates is a variable and depends on such items as production schedules, shift schedules, product mix, and varying system downtimes. After the model has been run the throughput is examined, the data collected and reports are generated. The Base Model Report will explain the simulation model results and include sections for conclusions and recommendations.
Phase #4 - Experimentation
- Define experimentation goals
- Incorporate changes to simulation model
A. Layout changes
B. Process changes
- Validation and verification
- Experimental simulation model runs
- Document data
- Update Final Report
After reviewing the results of the base simulation model and presenting the simulation to the customer, there are often "What If" scenarios to be considered. The experimentation phase takes these scenarios and incorporates them into the simulation model. This allows the customer, systems engineers, and the simulation consultant to adjust the system simulation to accommodate these other considerations.
In this phase an Excel based Graphical User Interface (GUI) should be developed to allow easy model input data and system parameter manipulation. This means the model can be quickly changed and run again to view the models output results.
Simulation modeling is a very important tool in delivering a total system that will meet the needs of the customer on the day of start up and well into the future.
Simulations Powered by:
