تخصیص ابزار در سیستم های تولید انعطاف پذیر با ابزار جایگزین

In this paper, a heuristic approach for tool selection in flexible manufacturing systems (FMS) is presented. The proposed approach utilizes the ratio of tool life over tool size (L/S) for tool selection and allocation. The proposed method selects tool types with high L/S ratios by considering tool alternatives for the operations assigned to each machine. The performance of the method is demonstrated in sample problems as static examples, as well as in a simulation study for further analysis. This study also presents a survey of several approaches related to loading and tool allocation problems in FMS, highlights the importance of tooling, and discusses the practical aspects of tool-oriented decision-making. An extended framework, which expands on the L/S concept, is also presented.

A flexible manufacturing system (FMS) consists of a computer-controlled, integrated configuration of numerically controlled machine tools with automated material handling systems. Combining the merits of job-shop and flow-shop production, an FMS provides a promising technology for mid-volume and mid-variety production. Problems related to flexible manufacturing technology are relatively complex compared to traditional manufacturing systems in which lead times are longer, inventory levels are higher, and utilization rates are lower. The difficulty originates primarily from the fundamental objective behind the FMS concept: be as efficient as a mass production facility and yet as flexible as a job shop facility. Since (1) each machine in an FMS is quite versatile and capable of performing many different operations; (2) the system can machine several part types simultaneously; and (3) each part may have alternate routes through the system, it becomes very complex to solve FMS planning, scheduling, and operational problems. Tool management is one of these types of problem.

In this paper, a heuristic for tool selection and allocation in FMS with cutting tool alternatives is presented. The heuristic is based on the Life-over-Size (L/S) ratio, which gives the virtual tool life per slot in a tool magazine. The L/S method leads to efficient use of space in tool magazines and shorter flow times since it reduces the tool changeovers. The performance of the proposed method has been demonstrated and an extended framework, which expands on the L/S concept, has also been described. Future work includes the implementation of the extended framework by incorporating different performance measures, such as tooling cost and tool availability, into the methodology. The L/S heuristic can be used as a complementary tool for various FMS loading, scheduling, and control methods in the FMS literature. Most of these models include tool allocation problem in connection with the operation assignments on machines by considering certain criteria, such as load balancing. On the other hand, due to complexity of the problem, these models ignore tool life and tool size, or simply assume a constant tool life and constant tool size for all the tools, while they consider tool magazine capacity as a constraint. Thus, the L/S heuristic can be combined with such methods in order to achieve realistic results, especially for random FMSs where the product mix is not known prior to production and real-time scheduling is the key.