Today, companies often have operations distributed around the world, and production facilities and designers are often in different locations. Increased use of outsourcing and geographically dispersed supply chains further complicates the manufacturing world. The globalization of manufacturing business means that companies should be able to design, build, and maintain, anywhere at any time. Manufacturing engineers are seeking effective tools during planning to help improve production processes, plant designs, and tooling, and to allow earlier impact on product designs. Collaboration may exist in a number of activities such as (a) reviewing designs with the design team; (b) interfacing with tooling designers; (c) verifying tooling assembly and operation; (d) reviewing manufacturing process plans and factory layouts; and (e) discussing manufacturing problems with suppliers. In larger companies, collaboration is becoming increasingly important in design and manufacturing. Everyone knows something, but no one knows everything. There is an evolution from individuals working independently to functioning in workgroups, as well as enterprise collaboration and collaboration throughout a supply chain. Within a supply chain, sharing knowledge has become paramount. This chapter describes the methods of developing an Internet-enabled, integrated CAD, CAPP, CAM, and CNC system to support collaborative product development. The main goal is to provide a team environment enabling a group of designers and engineers to collaboratively develop a product in real time. STEP can be used to represent product data for heterogeneous application systems and data formats, and the Web-based Product Structure Manager developed can be an effective function module to co-ordinate collaborative activities.
A Collaborative Framework
The aim is to achieve a STEP-compliant system for collaborative manufacturing (Xu & Mao, 2004). Figure 1 shows the basic system architecture (Xu, 2006). The system used STEP (ISO 10303-21, 1994, ISO/TS 10303-28, 2003) and STEP-NC (ISO 10303-238, 2007) standards to construct a universal data model.
STEP-compliant collaborative manufacturing model
In the design phase, STEP (ISO 10303-203, 1994, or ISO 10303-214, 1994) is used as the neutral data format to exchange design data between different CAD systems or between CAD and CAPP systems. Two different manufacturing information databases (generic and native) are needed to support data exchange for collaborative manufacturing. The generic manufacturing databases are abstract information about machine tools and cutting tools of any kind to be used during manufacturing activities. Hence, process plans generated using generic manufacturing resources cannot be executed directly at the shop-floor. This is because a STEP-NC based process plan at this stage has only information about “what-to-do”, i.e. the tasks. Examples of what-to-do information include machining features and the description of requirements of machine tool(s) and cutting tool(s). At this stage, no information about selection and determination of specific machine tool(s) and cutting tool(s) is present in the program. The native manufacturing databases reflect the actual conditions of a shop-floor including existing machine tools and cutting tools that can be used for populating and optimizing a generic process plan or generating native process plans for final execution. To this end, a native manufacturing database can be considered as a “DNA” bank for all the available manufacturing facilities.
As aforementioned, the basic element of a STEP-NC file is Workingstep instead of cutter locations. Workingsteps are built based on machining features. The system can use inputs from CAD systems, feature recognizer, CAPP algorithms and manufacturing resources to generate a STEP-NC file. As the CAPP system is designed based on a three-tiered architecture, it has the ability to switch between different manufacturing databases to generate generic or native STEP-NC files to provide a maximal flexibility to support collaborative manufacturing. As shown in dashed lines in Figure 1, when the CAPP system is connected to a generic database, the output STEP-NC files will be universal and machine tool independent. Under this condition, the CAM system can later populate and optimize a generic STEP-NC file according to the native manufacturing database on the shop-floor to obtain a suitable STEP-NC file for a specific CNC machine. When the CAPP system is directly connected to a native manufacturing database, it will be able to optimize the machining sequence, select machine tools and cutting tools at the process planning stage and generate a STEP-NC file which can be directly used by a targeted CNC machine. Figure 2 shows the detailed information flow in the proposed system (Mao, 2003).
IDEF0 diagram of the STEP-compliant collaborative manufacturing model
In this scenario, CAM systems are more likely to be integrated with STEP-NC enabled CNC machines or rather their controllers. The main functions of a CAM system are therefore to optimize the generic STEP-NC information and offer data connections to a CAPP system instead of calculating tool trajectories and generating CNC programs, which will be handled by the built-in functions of the STEP-NC controller.Top
The abstract model of the proposed system is illustrated in Figure 3 (Xu, 2006). As can be seen, the system is of a three-tiered network hierarchy. This helps to set up an integrated collaborative manufacturing environment.
Abstract system model of the STEP compliant CAPP system