1. Introduction <br> <br> cover mold CAD technology has undergone considerable development time, wherein the process analysis calculations, as finite element analysis, mold design assembly, parts standard database management techniques have achieved good Development, but at the same time it shows an urgent need in two aspects. On the one hand, because the graphics workstations and PCs participate in the design of the cover molds, they are responsible for different design and processing tasks. These tasks have different requirements in terms of computing power, speed, and visualization. Some common design standards and data. Stored in a few privileged hosts, the result is that the resources and computing power configured in the mold design system are not uniform. This unequal phenomenon is necessary in the cover mold CAD system. On the other hand, due to the requirements of CIMS development, the design results of the mold CAD system need to be shared in all aspects of its life cycle. The CAD system should have parallel design and strong information access capabilities. These two requirements are integrated into the research of parallel and integrated design in the cover mold CAD.
The computer network provides designers with resource sharing and data communication means. The client/server (C/S) model provides a mechanism for the interaction between different hosts and different processes. In the network environment, a parallel mold design system can be established through the client/server model to meet the needs of the above development.
2. System structure
2.1 Applicability Analysis Parallel and integrated mold design systems should have the ability of design process collaboration, design data sharing, and automatic deployment of hardware and software design resources. In general, centralized, distributed, and C/S models all have structural conditions for implementing parallel design, but the computational structure based on the C/S model is most suitable. It is a parallel working system composed of multiple hardwares connected by the network. In the collaborative design, the application calling means on different hosts provided by the network protocol can be utilized to realize the communication between the applications. Apply C/S model to carry out cover mold CAD, share design standards, data, parts library and general design process data inventory on the server, select workstation, PC, etc. for graphic display, assembly, simulation analysis, calculation, design The operation of things, the output of graphics, the management of data, and the design of components are on different network nodes. The C/S model is particularly suitable for the collaborative work of the mold CAD, which can be discussed from its calling characteristics.
(1) Non-equivalent interactions. The client/server is in an unequal position, the server has the hardware and software resources and computing power that the customer does not have, the server provides the service, and the client requests the service. In the CAD system of the cover mold, there are a large number of objective phenomena such as uneven distribution of resources and computing power. Some hosts have a large amount of external memory, some have plotter and printer output, some have super computing power, and some are composed of a large number of PCs. On the other hand, in the CAD work, in order to save network resources, it is not necessary to maintain a design database copy for each host, but the public information exists in the form of a design database in a few privileged hosts. For content that changes dynamically in the design, this measure makes it easy to dynamically modify refresh operations, consistency maintenance, and more.
(2) Request driver service. When designing parts on different machines, there is neither a parent-child relationship nor a memory buffer between the processes communicating with each other, and no one knows who will initiate a process communication at each design node. The C/S model mechanism establishes a connection between the processes that prepare for communication, and provides synchronization for the data exchange between the two, which perfectly solves the above problems. Each interaction is initiated by the client requesting an information service or computing service. The request response model between the server and the server provides strong support for data transmission synchronization between the communication processes. The server receives the request and returns the processing result to the client over the network.
2.2 System structure and configuration The structure of the cover mold CAD system based on C/S model is shown in Figure 1. The hardware with high I/O throughput and powerful computing power is used as a server to store the mold design standards, the mold standard parts library, and the general design process that need to be shared. The client is configured according to the various needs and actual conditions of the CAD design. The graphic workstation is used for mold work profile design, mold assembly design and finite element analysis. Static design data management is performed on a PC. In addition, you need to configure output devices such as plotters and printers. The structure uses the C/S model to divide the hardware, and correspondingly divides the processing requests and assigns them to different hardware to fully utilize the capabilities of different hardware.
Fig.1 Structure of cover mold CAD system based on C/S model
The cover mold CAD system is composed of many functional modules, generally including product graphic input, process plan development, mold profile design, finite element analysis, mold structure design, mechanism motion simulation, assembly drawing and part drawing output, and mold standard parts. Modules such as library management have a relationship between parallel design, trigger execution, and inheritance design. Each functional module is completed by at least one process. The entire system has a more complex flow of information. In the design behavior, assembly design requires a better graphics terminal; finite element analysis requires hardware equipment with strong computing power; mechanism motion simulation is performed on the host where special software is installed; retrieval and calling of mold standard parts, Through the operation of the design database to complete; the design of each component, the drawing output, scattered on the ordinary node. There is a connection between design actions. The C/S model is used to better divide the design process to coordinate the execution of each process.
3. Key technology research
The traditional cover mold CAD has the problem of repeated storage of design resources, large design data access and update overhead, transmission of graphics, analysis results, system information, etc. in the design, and low efficiency. The cover mold CAD system using the C/S model can better solve these problems. However, the design and implementation of the system is more complicated because it requires uniform design coordination and the design behavior is not as flexible as stand-alone.
This article will focus on the implementation of the system application C / S model. The design technique of each functional module in the cover mold CAD is consistent with the content of the traditional CAD.
The characteristics of the client/server model determine the general principles of designing clients and servers. The client provides the user with an interactive interface that translates the user's input into commands that the server can understand. The client analyzes the results of the command execution sent by the server and describes it to the user. The server is driven by the event of the client, responds to user requests, and establishes a connection with the client to provide services.
The implementation of the C/S application framework is divided into two parts, namely the server program installed on the server side (C/SS) and the client application (C/SC) installed on each Clien t side. The application logic structure of the composition is shown in Figure 2.
Figure 2 Logical structure of C/S working framework program implementation
In the implementation of the C/S working framework, the above functions are mainly performed by modules such as a circular queue, a command transmitter, a network receiver and a transmitter, and a command executor.
The ring queues are the receive queue, the send queue, and the destination site queue. The command sender is essentially a subfunction provided to the function module call with the parameters of the command string to be sent and the address of the destination site.
When the C/S working framework is implemented in the Windows environment, the client window and the server window are respectively established on the client side and the server side. Interactions between them include establishing connections, sending and receiving service requests, sending and receiving operational results, and the like.
The author implements the above functions in a TCP/IP programming method. Taking the design of the drawing die of the cover as an example, in the structural design module, there are detailed design (such as convex and concave die design, beading ring design) and standard component matching. If the former is the main design process, it is identified by mainprocess; when the standard design process (identified by partprocess) on other hosts is executed, in the case of normal connection, the following loop can be used.
For(;;){partprocess=accept(mainprocess,...);/*block*/
If(partprocess<0)error("accept error");
If(fork( )<0){close(mainprocess);/*subprocess*/
Do(partprocess);/*Processing requests*/
Exit(0);}
Close(partproce ss);}/*parent process*/
The server's address includes the server host address and server port number, which can be retrieved through coordinated calls and populated into the data structure managed by the CAD system process.
4 Conclusion
The application of the client/server model in the CAD of the cover mold is mainly for the research of system software and hardware resource sharing, communication, process management and so on. This application enables the single-machine discrete cover mold CAD design module to be combined into a multi-faceted collaborative design of different models; multiple hardware devices with different performances and functions can cooperate to complete complex without leaving the product design process. Mold design task; give full play to the computing and graphics processing capabilities of the workstation, flexible and convenient performance of the PC transaction, parallel coordination work, logically become a design overall; application network means to achieve design resource sharing and product data, part graphics Transfer is automatically called.
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