Simulation-based Scheduling Research Articles

A simulation-based scheduler for flexible flowlines

Abstract A flexible flowline is a generalized production model employed in a wide variety of manufacturing assembly applications to produce a range of products in small batch quanitites. The MRP systems, which are commonly used in such environments, lack the detail to carry out daily scheduling. Recently, finite capacity planning tools have been suggested as a means of generating short-term production schedules. These tools employ techniques that take a global view of the problem and are based on static ‘snapshots’ of the manufacturing system. However, they ignore any inherent dynamics and therefore are inadequate in managing disruptions that can be very costly in terms of the inability to meet throughput requirements and prior delivery commitments. A simulation-based scheduler, on the contrary, is effective in accommodating the dynamic and/or stochastic nature of the system in arriving at a sheduling solution. In this paper, we introduce a simulation-based scheduler which is used to study a general class...

A heuristic rescheduling algorithm for computer-based production scheduling systems

Generation of new production schedules in response to changes that take place on a factory shop-floor is a common requirement in today's complex and flexible manufacturing environment. The current approaches use either a regeneration rescheduling method, which results in unsatisfactory response times or methods that need too much manual intervention for identifying the operations to be changed. We propose a new rescheduling algorithm to address these problems. Our algorithm is based on the construction of a scheduling binary tree and a net change concept adopted from MRP system. It revises schedules by rescheduling only those operations that need to be revised. Our algorithm can be embedded in existing simulation-based scheduling systems or electronic Gantt chart approaches to improve their effectiveness.

SIBS — a job shop simulation-based scheduler

The problem of finite capacity short-term scheduling in a modern CNC job shop is addressed. The application is an Israel Aircraft Industries (IAI) plant which is conceptually designed as a manufacturing cell. The cell contains six very large (bed length 451–452 inch) 3-head spindle, 5-axis CNC milling machines. A simulation-based scheduler based on SIMAN (a general purpose simulation package) is presented as the means for generating schedules. It is shown that shop performance measures such as lead times, throughput and machine utilizations are improved by an order of 30%, which represents a substantial saving due to the increased capacity of the manufacturing cell.

Simulation-based production schedule generation

Abstract While simulation has been used in manufacturing for many years, predominantly for facility design, it is within the last few years, that simulation languages have been developed to a point where they can be used on a day-to-day basis to generate schedules and predict their performance. This paper describes our use of different modelling techniques to develop a production schedule generation system. An example describing a system for a small- to medium-sized order producing company using SIMAN/CINEMA is included. While addressing the shortcomings of existing scheduling systems it is shown how the approach taken is a feasible way of creating a dynamic goal-driven simulation-based production scheduler. The paper does not aim to describe an ‘off the shelf’ scheduling system product, but rather to give an overview to methods, techniques and experiences which enable us rapidly to tailor a simulation-based scheduling system to the specific needs of a company.

Optimisation of crew size and repair policy in flexible manufacturing systems

This paper presents a simulation-based scheduling algorithm for evaluating the performance of different repair policies and computating the optimum size of repair-crews in flexible manufacturing systems. The simulation experiments were conducted for a system with numbers of machines ranging from six to twelve, processing 15 different types of parts. The experiments were planned according to the rules of central composite rotatable experiment design, and the system performance was optimised on the basis of minimum unit production cost. It has been concluded that for the particular system configuration studied, a repair policy based on shortest repair time yields the best results. It has been shown further that the optimum size of repair crews is much more sensitive to labour costs than to other production-associated costs.

A simulation-based scheduling and management information system for a machine shop

This paper describes the design, working, performance, costs and benefits of a computerized scheduling and management information system that has been developed for a large, generalized m/n machine shop which had previously been a bottleneck facility in the Cast Roll Manufacturing complex of Bethlehem Steel Corporation. A flexible discrete-event simulation model, at the heart of the computer system, generates two types of schedules: Planning Schedules for making long- and medium-term planning and operating decisions, and Production Schedules for sequencing approximately 1000 rolls on 40 machines on a day-to-day basis.A number of supporting programs perform data management, file management, and report-generation functions. Data-collection functions are deliberately performed manually to avoid the high costs associated with automatic data-collection equipment normally used in large computer systems. The computer programs are run in a time-sharing environment. A cathode ray tube and a medium-speed printer are the only hardware requirements of the system. With the implementation of the computer system, significant improvement is now being obtained as measured by productivity, labor and machine efficiencies, due date performance, and work-in-process inventory. The computer system is saving Bethlehem a substantial amount of money every year, and a notable feature of this system is its low annual operating cost.

A Simulation-Based Scheduling and Management Information System for a Machine Shop

This paper describes the design, working, performance, costs and benefits of a computerized scheduling and management information system that has been developed for a large, generalized m/n machine shop which had previously been a bottleneck facility in the Cast Roll Manufacturing complex of Bethlehem Steel Corporation. A flexible discrete-event simulation model, at the heart of the computer system, generates two types of schedules: Planning Schedules for making long- and medium-term planning and operating decisions, and Production Schedules for sequencing approximately 1,000 rolls on 40 machines on a day-to-day basis. A number of supporting programs perform data management, file management, and report-generation functions. Data-collection functions are deliberately performed manually to avoid the high costs associated with automatic data-collection equipment normally used in large computer systems. The computer programs are run in a time-sharing environment. A cathode ray tube and a medium-speed printer are the only hardware requirements of the system. With the implementation of the computer system, significant improvement is now being obtained as measured by productivity, labor and machine efficiencies, due date performance, and work-in-process inventory. The computer system is saving Bethlehem a substantial amount of money every year, and a notable feature of this system is its low annual operating cost.