The rapid development of networks and their derivative technologies are changing the existing work mode of the manufacturing industry. Whether it is supporting the system environment or the application technology, with the penetration and fusion of network technology, people in the information environment and the synergistic efficiency between group distribution members will increase significantly. Thus, the network-based synergy, sharing, remote operation, and distributed processing technologies are hot spots in various fields. The NCAD (NETWORK-CENTRIC CAD, "CAD-centered CAD-centered CAD) has also happened.
Since the 1990s, the focus of global competition has become how to use various new technologies that continue to emerge, develop high-performance, high quality, low-cost, high value-added products in the shortest time, and The fastest speed response market demand. With this wave of business globalization, the development of computer soft, hardware and network technology has greatly promoted the global design and production of products. The pace of this globalization has increased the demand for CAD supported by the network.
A complex product will involve different professional knowledge in concept design and detailed design, which not only emphasizes different design directions and styles, but also constructs and handles data models in different fields. From the technical level, the design of the product is more than just the interaction of designers and products, but also exchanges with other designers and environments. Design can be seen as a group of group activities with common ultimate destination, and design activities that interact through designers and environment is our collaborative design. Computer supported network CAD enables group members (including designers, producers, sellers and managers, etc.) to exchange product information in parallelism, collaboration in the product lifecycle, and design ideas, design processes, design organizations and Design information is coordinated and managed, which strengthens collaborative support between people.
A new discipline
Although the network CAD has no uniform definition, it is widely believed that the use of network and its derivative technology, through distribution of synergistic work mode, making product design reasonable or orderly, design, design resources and information models A new technology extensively shared, ensuring high performance, high quality, low cost and short cycling of CAD products.
There are many related methods for network CAD concepts, but most of them are based on network technology terms. A comparative authoritative proposed method appeared at an international conference in the 1997 AMERICAN SOCIETY OF Mechanical Engineers, and the concept of network CAD is called "CAD-centered CAD". In 1998, the International Famous CAD Magazine "Computer-Aided Design" issued the same concept on the network CAD, but also pointed out that the network-centric CAD technology is "an important and new cross-discipline study. The central area ", it involves" physical shape, calculation, database, distribution calculation and remote communication ", and is determined," The design and manufacturing environment of the 21st century relies on network CAD technology. "
Earlier in the DAC (Design Automation Conference) branch in ASME in 1996, a distributed CAD design system - WELD prototype system is introduced to participants, causing extensive attention. In 1997, the "NetWork-Centric Cad" research on the "NetWork-Centric Cad" in the ASME Design Engineering, marking the broad recognition of the international academia based on the network-based CAD technology. In 1998, the concept of network CAD is called "web-based design" and "Internet-based CAD". In 1999, it referred to as "Internet-Aided Design). It can be seen that network CAD technology is gradually become an emerging discipline, which mainly involves: distributed database, metadata, standard data exchange format, distribution application, network technology, data compression technology, computer support jobs. Treatment human machine integrated system
Currently, network CAD is primarily applied in the following aspects:
· CAD / CAM / CAE integrated CAD / CAM / CAE has become one of the important signs of the national science and technology modernization and industrial modernization. The purpose of CAD / CAM / CAE integration is to provide a design-based, more efficient design / manufacturing overall system that can be mainly stored in a certain type of product, to store and communicate the information required by each application. Reach software resources and information sharing to avoid unnecessary repetition and redundancy. Network CAD itself focuses on system environment sharing and software sharing control and management of information consistency, providing flexible integration from hardware integration and software integration for CAD / CAM / CAE.
· The competition of remote computing and design markets leads to the dispersibility and distribution of product resources. Network CAD uses network and web to seek design center (server) support and collaboration, providing remote CAD computing and design tools, off-site heterogeneous services, improved the working mode of remote design. Currently, remote CAD resource based on Web technology is a hot spot for network CAD research and application.
· A major development direction of workflow management and PDM network CAD is the cooperative automation of human-computer interaction events. Regardless of workflow management techniques or PDM systems, there is a certain design process management sharing and automation feature. The corresponding product information model is based on multi-user, multidisciplinary, multi-perspective, not only the needs of network CAD, but also conducive to product object workflow management and data management.
· Virtual product visualization virtual products refer to digital product information of computer expression. In the distribution environment, CAD collaboration work is made by virtual product visualization model, which is more conducive to optimizing design environments, improving collaborative efficacy, perceived design objects, and deepening sensibility. Virtual environments, visualization techniques, etc. also gradually cross the network CAD, construct more coordinated human-machine integration systems.
Looking forward to the unity of data standards
The research content of network CAD includes multiple levels such as technology, organizations and methods. From a technical speaking, it includes CAD, database, distribution calculation and network technology. From the organization, network CAD is a cross-discipline, and its product objects also involve multiple disciplines. The organization, sharing and integration of each subject and technology is the key to research. From the method, network CAD design relies on object-oriented technology, distributed object technology, facing intelligent programming technology, etc.
In recent years, the research on online CAD technology is very active, and the related research projects have been complicated, and the focus is different. Some famous research projects include: US MIT lead ADDFCAPAM project, MIT and STANFORD SCSS project; Stanford's PPP system, Sprint CAD system, Suprem 007 project; European Six countries jointly developed Visinet Project, EU Race funded MWORLD project and many more.
At present, the research and development of network CAD is mainly concentrated in the following areas:
· Web-based CAD CAD design has been applied to various industries. New challenges are not only a large number of different CAD systems and different user interfaces, as well as geographic dispersion of designers, tools and data. In recent years, software technology has developed rapidly, promoting the application of Internet online distributed user interface, but the use and development of remote off-site CAD tools is not enough, and the current Web-based core problem is how to use web technology to easily get and provide and provide CAD remote resources, including design tools, design data, design knowledge, and more. Web technology can link geographically different CAD systems, shortening people - people, people - machines, machine - machine distances. We face a severe problem is whether the existing CAD system resources can easily enter the virtual design environment constituted by Web and Java and is conveniently used, not big modifications or no re-develop. · Multi-discipline CAD Information Model Network CAD technology is based on the needs of shared data between different design applications. Its development is a collaboration for different design models, with a collaborative characteristics, and its product objects also involve multidisciplinary. In computer expression, virtual products should provide sufficient information to meet multidisciplinary, multi-perspective needs. The current method is mostly starting from the characteristic information of the product, constructs complete information and association information for different disciplines. This puts a high requirement for product data expression and exchange standards. Data standards such as STEP, IGES, DWG, DXF, DWF have no longer meet the above functions. How to construct new data standards or expand existing data criteria is one of the hotspots of research.
· Generalized CAD Generalized CAD is an extension of CAD in the network. It refers to some functions, such as: the word processing and tabulation of related files, design expressions, design execution Assess analysis, rendering database management with animation techniques, heterogeneous distribution information. In addition, it also includes multimedia technology, support for CSCW technology. Relatively speaking, generalized CAD considers more continuity and inheritance of the information room. An urgent problem to be solved is the flexibility of the related art.
· Agent-based distribution virtual design environment Construction based on Agent's virtual design environment is to create a relatively harmonious human machine collaboration environment, is a development direction of future network CAD. Agent-based approach, especially facing intelligent programming technology, is an improvement in object-oriented technology. Since the Agent-based distribution virtual design environment is quite high, the hardware requirements are quite high, the technology must truly enter the practical phase, and there is still a long way to go.
This can be asserted that the rapid development of the network and its derivative technologies makes the traditional CAD's quality leap, and is a new discipline. The development of online CAD technology is currently focused on remote resource sharing of multi-disciplines and multi-users. The ultimate goal is to create a harmonious human machine collaboration environment. The implementation of this goal also needs to do further a large number of related research work.
Related Links
CAD core modeling technology
Wireframe Model
As a geometric model that is commonly used in the late 1950s, it uses a line segment, circle, arc and some simple curves to describe the object, using the edges of the product body to represent the geometry of the product, which is typical. Two-dimensional computer drawing technology. Due to its own inherent defects, the wireframe model cannot effectively express the topological relationship between geometric data.
Surface model (SURFCE MODEL)
Describe the surface of the body surface, the collection of the surface of the shape is used to define the shape, thereby satisfying the surface of the surface, the wire blanking, bright and dark color chart, CNC machining, etc., enabling extensive engineering The application, but due to the surface information of the surface, it is still not possible to meet the demand for engineering optimization design.
Solid model
Compared with the line frame, the physical shape increases the explicit definition of the existence side of the entity, gives the topology information such as the inter-surface inter-surface, so that all the properties of the part can be accurately expressed, help unified CAD, CAM, CAE model expression Data loss can be reduced, and the integrity of the data can be maintained on the design and processing.
Feature Model
The first three types of modeling, for non-geometric information, such as size, material, tolerance, process, cost, etc., there is no reflection, so the information of the entity is incomplete, and the feature styling technology is present under this requirement. . It provides a richer information for various engineering applications, and the characteristics based on the characteristics of the characteristics as the basic unit defined by the part, and the part is described as a collection of features.
Parametric Technology
The key to parameterization design is the extraction and expression of geometric constraints, constraint solving and parameterized geometric model. Its main feature is: based on feature, full-size constraint, full data, size drive design modification, constraints refer to the relationship between elements constituting the entity using some rules or restrictions.
Variation Technology
Allowing the existence of size underdrawn, the designer can use the first-shape size design to satisfy the geometry of the design requirement, and it is relatively relatively relatively relatively relatively easy to consider the dimensional details. Variable design can be used for tolerance analysis, motion mechanism coordination, design optimization, preliminary design selection, etc., especially when making conceptual design.
