ادغام برنامه ریزی با برنامه ریزی فرایند به کمک کامپیوتر

Computer aided process planning (CAPP) and scheduling are two major activities in a modern manufacturing system. The existing CAPP systems have not taken account of shop floor conditions while developing process plans. This paper discusses the importance of integration of scheduling and CAPP and proposes a method for the same. There can be several methods to machine a part and several machines capable of performing the process required to complete the part. Based on this concept, this paper suggests a method of scheduling and its integration with CAPP, so that on-line process plan can be generated taking into account the availability of machines and alternative routes. A scheduling factor for an operation and machine combination has been defined taking into consideration the actual working conditions and capabilities of the machines. Finally operation–machine assignment is made on the basis of these actual scheduling factors. This helps in generating more realistic process plans and helps in improving the efficiency of the manufacturing system as a whole.

Computer aided process planning (CAPP) has been recognized as playing a key role in a computer integrated manufacturing (CIM) environment. Two of the major activities in a manufacturing system are process planning and scheduling. Process planning as defined by Chang and Wysk [1] and [2] is the act of preparing detailed operation instructions to transform an engineering design to final product. The detailed plan contains the route, processes, process parameters, machines and tools required for production. It generates operational details such as: sequence of operations, speeds, feeds, depths of cut, material removal rates, and job routes. Required inputs to the planning scheme include: geometric features, dimensional sizes, tolerances, materials and surface finishes. These inputs are analyzed and evaluated in order to select an appropriate sequence of processing operations based upon available machinery and workstations. Generation of good, consistent and accurate process plans requires the establishment and maintenance of standard databases and the implementation of an effective and efficient method to process the data. The computerization and the resultant automation of process planning has evolved due to a substantial need caused by the lack of qualified personnel, inconsistency in planning, and the need for the incorporation of knowledge on continually evolving new processes [3] and [4]. Scheduling is defined as the allocation of resources over time to perform a collection of tasks. The objective of scheduling is to assign specific task to specific machine in order to balance load distribution among different machines so that the available machines can be effectively utilized. This enhances efficiency and effectiveness of the machine shop [5].

Integration of CAPP and scheduling is vital for implementing a complete CIM system. In this paper a method has been proposed to incorporate on-line scheduling in a CAPP system. A scheduling factor has been proposed for assigning a machine to an operation. Actual scheduling factors for various alternative machines are computed after considering the machines breakdown condition, availability and capability. Finally, operations are assigned to the machines with highest value of actual scheduling factor. This helps in on-line determination and assignment of the shop load on various machines. This results into effective and efficient integration of CAPP with scheduling.