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RTMS; Realizing Virtual Manufacturing In simulation literature, simulation is defined as “The discipline of designing a model of an actual or theoretical physical system, executing the model on a digital computer and analyzing the execution output.” In the simulation model the key elements of the real system which provide service are defined as resources. Resources represent things like equipment and personnel. The behavior of resources including personnel in the simulation model is completely controlled by predetermined rules. These rules are set by the person who develops the simulation model. Thus, the result of the simulation will be a solution determined by the model constructed, and the precision and speed of the computer used to process the model. The glaring omission in this method is its inability to utilize the creativity and team work of the personnel “resources ”in the simulation model since they exist as nothing but ones and zeros traveling inside the computer ’s circuit boards. To this point, efforts to give life to these personnel have resulted in 3D animations of them; however, the real workers still have no power to participate in the decision making process during the development of the simulation model and its execution. What is the RTMS? The Real Time Machine Simulation (RTMS) system allows the participation of students in simulation modeling of a manufacturing cell and its execution. It is not designed to completely replace the computer simulation; however, it is an effective teaching and research tool. The RTMS system consists of a central computer, a set of machine simulators, plastic or wooden blocks to represent jobs, and student team to represent machine operators. The machine simulators, are devices which represent machines in manufacturing cells. A machine simulator has almost all the features of a typical machine and it is controlled by the central computer. Three basic features of the machine simulator are: (i) Operation related features, (ii) Availability related features, and (iii) Quality related features. The operation related features include operations usually required in processing a job on a machine. These operations are (i) loading operations, (ii) setup operations, (iii) processing operations, and (iv) unloading operations. A production cycle on a machine includes the above operations in sequence loading, setup, processing and unloading. In RTMS system each operation takes real time and is done automatically or by an operator (worker). The computer generates these times according to the input distribution and signals the RTMS to reflect the start or the end of each operation.
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How Does It Work?
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In
order to simulate a system, first the machine simulators must be placed on work
benches according to the layout of the system under study. Then the
characteristics of the system such as the number of machines, job routings,
probability distribution of each operation time on each machine, and so forth
must be defined for the RTMS software in the central computer. The student team,
which will work as machine operators, must then choose a policy which they
follow during the simulation. When the simulation starts, every time an operator
puts a job (a block) on a machine and pushes a button, say loading, the computer
immediately generates a loading time based on its probability distribution on
that machine, say 20 seconds. Since the loading operation requires the presence
of the operator, the operator must perform the loading operation until the
machine signals that the loading operation is completed (which will take 20
seconds). The operator (student) must then push the processing button on the
machine, and if the processing operation is automated he can switch to other
machines or wait for that machine to finish processing. When the processing time
generated by the computer is elapsed, the machine signals a light which means
that it is ready for the unloading operation. The machine will stay in that
state until an operator becomes available and starts the unloading operation.
While the simulation continues in this manner, the central computer keeps
records of all information and provides reports on performance measures such as
the average WIP, cycle times, delays and throughput of the system. At the end of
the simulation, the student must submit a report on the performance of their
design. The simulation experience provides a real understanding of problems
which might occur during the implementation of their design.