Virtual Manufacturing Systems
Published on Jan 10, 2016
The term Virtual Manufacturing is now widespread in literature but several definitions are attached to these words. First we have to define the objects that are studied. Virtual manufacturing concepts originate from machining operations and evolve in this manufacturing area.
However one can now find a lot of applications in different fields such as casting, forging, sheet metalworking and robotics (mechanisms). The general idea one can find behind most definitions is that “Virtual Manufacturing is nothing but manufacturing in the computer”. This short definition comprises two important notions: the process (manufacturing) and the environment (computer).
In [1, 2] VM is defined as “manufacture of virtual products defined as an aggregation of computer-based information that provide a representation of the properties and behaviours of an actualized product”.
Some researchers present VM with respect to virtual reality (VR). On one hand, in  VM is represented as a virtual world for manufacturing, on the other hand, one can consider virtual reality as a tool which offers visualization for VM  .
The most comprehensive definition has been proposed by the Institute for Systems Research, University of Maryland, and discussed in [5, 6] is “an integrated, synthetic manufacturing environment exercised to enhance all levels of decision and control”
A similar definition has been proposed: “Virtual Manufacturing is a system, in which the abstract prototypes of manufacturing objects, processes, activities, and principles evolve in a computer-based environment to enhance one or more attributes of the manufacturing process.”
One can also define VM focusing on available methods and tools that allow a continuous, experimental depiction of production processes and equipment using digital models. Areas that are concerned are (i) product and process design, (ii) process and production planning, (iii) machine tools, robots and manufacturing system and virtual reality applications in manufacturing.
The Scope of Virtual Manufacturing:
The scope of VM can be to define the product, processes and resources within cost, weight, investment, timing and quality constraints in the context of the plant in a collaborative environment. Three paradigms are proposed in :
a) Design-centered VM: provides manufacturing information to the designer during the design phase. In this case VM is the use of manufacturing-based simulations to optimize the design of product and processes for a specific manufacturing goal (DFA, quality, flexibility,) or the use of simulations of processes to evaluate many production scenarios at many levels of fidelity and scope to inform design and production decisions.
b) Production-centered VM: uses the simulation capability to modelize manufacturing processes with the purpose of allowing inexpensive, fast evaluation of many processing alternatives. From this point of view VM is the production based converse of Integrated Product Process Development (IPPD) which optimizes manufacturing processes and adds analytical production simulation to other integration and analysis technologies to allow high confidence validation of new processes and paradigms.
c) Control-centered VM: is the addition of simulations to control models and actual processes allowing for seamless simulation for optimization during the actual production cycle.
Another vision is proposed by Marinov in . The activities in manufacturing include design, material selection, planning, production, quality assurance, management, marketing, If the scope takes into account all these activities, we can consider this system as a Virtual Production System. A VM System includes only the part of the activities which leads to a change of the product attributes (geometrical or physical characteristics, mechanical properties,) and/or processes attributes (quality, cost, agility,). Then, the scope is viewed in two directions: horizontal scope along the manufacturing cycle, which involves two phases, design and production phases, and a vertical scope across the enterprise hierarchy. Within the manufacturing cycle, the design includes the part and process design and, the production phase includes part production and assembly.
We choose to define the objectives, scope and the domains concerned by the Virtual Manufacturing thanks to the 3D matrix represented in Fig. 2 which has been proposed by IWB, Munich.
The vertical planes represent the three main aspects of manufacturing today: Logistics, Productions and Assembly, which cover all aspects directly related to the manufacturing of industrial goods. The horizontal planes represent the different levels within the factory. At the lowest level (microscopic level), VM has to deal with unit operations, which include the behaviour and properties of material, the models of machine tool – cutting tool – workpiece-fixture system. These models are then encapsulated to become VM cells inheriting the characteristics of the lower level plus some extra characteristics from new objects such as a virtual robot. Finally, the macroscopic level (factory level) is derived from all relevant sub-systems. The last axis deals with the methods we can use to achieve VM systems.
Applications of VM
The attractive applications of VM include: analysis of the manufacturability of a part and a product; evaluating and validating the feasibility of the production and process plans; optimisation of the production process and the performance of the manufacturing system. Since a VM model is established based on real manufacturing facilities and processes, it does not only provide realistic information about the product and its manufacturing processes, but also allows
for the evaluation and the validation of them. Many iterations can be carried out to arrive at an optimal solution. The modelling and simulation technologies in VM enhance the production flexibility and reduce the ``Fixed costs'' since no physical conversion of materials to products is involved. Apart from these, VM can be used to reliably predict the business risks and this will support the management in decision making and strategic management of an enterprise.
Some typical applications of VM are as follows:
1. VM can be used in the evaluation of the feasibility of a product design, validation of a production plan, and optimisation of the product design and processes. These reduce the cost in product life cycle.
2. VM can be used to test and validate the accuracy of the product and process designs. For example, the outlook of a product design, dynamic characteristics analysis, checking for the tool path during machining process, NC program validation, checking for the collision problems in machining and assembly, etc.
3. With the use of VM on the Internet, it is possible to conduct training under a distributed virtual environment for the operators, technicians and management people on the use of manufacturing facilities. The costs of training and production can thus be reduced.
4. As a knowledge acquisition vehicle, VM can be used to acquire continuously the manufacturing know-how, traditional manufacturing processes, production data, etc. This can help to upgrade the level of intelligence of a manufacturing system.
1 . Iwata K., Onosato M., Teramoto K., Osaki S. A., Modeling and Simulation Architecture for Virtual Manufacturing System, Annals CIRP, 44, 1995, pp. 399-402
2. Lee D.E., Hahn H.T., Generic Modular Operations for Virtual Manufacturing Process, Proceedings of DETC’97, ASME Design EngineeringTechnical Conferences, 1997.
3. BowyerA., Bayliss G., Taylor R., Willis P., A virtual factory, International Journal of Shape Modeling, 2, N°4, 1996, pp215-226.
4 . Lin E., Minis I., Nau D.S., Regli W.C., The institute for System Research, CIM Lab, 25 March 1997, www.isr.umd.edu/Labs/CIM/vm/vmproject.html
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