机械设计类外文参考文献及翻译 第4页
system will check the security level of users, and determine which modules they can access or employ. According to authentication for the system, all usersa re to be divided into four categories: general users (without registration), potential clients, real clients, and system administrator. Received job requests from clients, the SB will perform firstly process planning which fulfills the task decomposition and selects the most suitable process methods. It is necessary for users to get the preliminary product quote and manufacturing time from the SB before the follow-up process continues. If such results may be accepted initially, The SB will negotiate further with users by Video-conferencing system. Once come to term each other, a contract is to be confirmed, and the user becomes a real client. The manufacturing tasks submitted by real clients had better be implemented in the SB. However, if the SB has no such manufacturing capabilities or can not accomplish then in time, it is an effective way that the SB takes full advantage of external sources to carry out the remaining tasks.
 The next step is to select the appropriate collaborative manufacturing enterprises to form a virtual enterprise to complete the tasks by the task assignment decision system. In addition, in order to monitor the manufacturing schedule to ensure smooth production, both collaborative manufacturing enterprises and SB itself must provide as quickly as possible the essential information related to production progress and schedule for the module of production monitor. So any companies falling behind schedule or failing to meet quality standards will be closely examined by SB and users to ensure that precautionary or remedial measures are made ahead of time or any damaging effects are predicted.
Referring to the workflow of networked service system above and the functional requirement of the digital teleservice system, the service system consists of nine functional modules: the technique research, typical cases, information consultation, ASP (application service provider) tool set, client management,
Electronic commerce, manufacturing service, system navigation. Its detailed structure is shown in Fig. 3.
These nine components work together seamlessly to achieve the common objectives, i.e. to provide an effective and prompt service platform to support the rapid product development of SMEs. One of the purposes of the technique research is to enable users to increase awareness of the relevant knowledge of rapid product development. In order to help users better understand and apply these new techniques, the system illustrates a number of real-life cases. Both the technique research and typical cases mainly provide self-help service for users. Depending on the predominance of specialty and expert, the SB can answer the queries of clients and communicate with novices to solve their problems by the information consultation module.
The ASP tool set provides five useful components below: the process planning of RE/RP/RT, STL checking and fixing, the optimization of part orientation, the support structure generation, and the optimization of part slicing. There are various process methods for RE, RP and RT as previously described, each of them has its characteristics and the scope of application. It is especially difficult for many novices to select the most suitable process methods according to the individual task requirement and condition. Three selectors based on ASP mode, namely, ‘‘RE selector’’, ‘‘RP selector’’, and ‘‘RT selector’’ have been developed to perform process planning automatically in the Web Serverside. In [38], Miller states that .STL files created from solid models have anomalies about 10% of the time and those created from surface models have problems about 90%of the time. Error rates in this range make it clear that automated error checking is important for all RP operations. Based on our experience with supplying network-based resources, we know that it is especially crucial to perform automatic error checking when the RP operation is not at the designer’s site. We have developed various algorithms to detect, and in some cases, automatically fix geometric and topological flaws. There are two ‘‘firewalls’’ to detect those flaws: one is integrated with the online pricing engine that will be operated by the user before the .STL file is submitted to the SB, while the other is to run on the SB’s Server-side after the .STL file is submitted. Because the function of fixing is quite restricted, if a .STL file has fatal flaws or loses some data during transferring, it would have to be uploaded again from the Client-side. Parts formed using RP technique can vary significantly in quality depending on the manufacturing process planning. The process planning of RP is performed to generate the tool paths and process parameters for a part that is to be built by a particular RP process. The steps required are the part orientation,

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