Parallel Production Lines Research Articles

Price-based buffer sizing in assembly systems

Internal transfer pricing mechanism will be applied to the problem of buffer allocation in the context of interfacing an assembly line with multiple parallel production lines. Economic effect of buffer sizing iin assembly will be analyzed by means of internal transfer pricing. New internal transfer pricing scheme will be designed to increase the efficiency of assembly system globally not sub-optimally. This new approach will enhance the economic benefit of production channel between an assembly line and multiple production lines. This study will give the basic idea for the application of internal transfer pricing mechanism in various kinds of manufacturing system to increase economic efficiency globally.

Scheduling of batch digesters according to different control targets and servicing limitations

The scheduling problem for a set of batch digesters with cyclic repetition of phases is considered. The specific problem addressed is the on-line scheduling of pulp digesters that operate in two parallel production lines under common resource limitations. Each line has a storage tank which is installed after the batch section and feeds continuously operated line downstream. The problem of scheduling is to determine the digester sequence and the corresponding batch start and completion times in order to maintain continuous production downstream while also maximize batch cycle time to improve pulp quality and reduce energy consumption. The proposed solution procedure is based on a heuristic algorithm combining neighborhood search technique and linear programming. Searching for the batch sequence enables to set the production rate for each line individually. Using linear programming, the problem is formulated generally enough to be adapted to frequent changes of control requirements quickly and easily. The algorithm was first tested off-line for a set of different operating conditions. Also, it was included into a pulp cooking simulation package and tested as a part of control algorithms designed for computer automation.

A Low Cost Control Structure for Flexible Production Lines with Multitask Workcells

Flow-type organisation of production lines is often encountered in small and medium sized companies. In order to improve the through put, to ensure a high quality of the products and to reduce the manufacturing time, flexible automation is necessary, which naturally leads to the CIM approach. The paper describes a flow-type production line for can filling, which can be utilized both in the petrochemical and in the food industries. Considering the typical production line as a numerically controlled workcell, a parallel production structure with multitask workstations is proposed, leading thus to an efficient extension of the company’s shop floor. In such a parallel production line (PL) there are a number of identical multitask workcells (KTWC) which include a fixed number of workstations, seτeral Industrial Robots (IR) with interchangeable grippers and tools and diverting devices. The workstations perform all the necessary operations in order to obtain the final products. Thus the productivity of a PL is given by the sum of the productivities of its parallel branches. For such a process structure, the paper proposes a hierarchical control configuration. At the level of local automation, a number of Programmable Logic Controllers (PLC) are used. Product transfer and handling requires the connection of the PLCs with the controller of two IR, in order to ensure the proper material flow between the production branches. Manufacturing in the PL is integrated by a high-level computer, which analyses order entries, performs job scheduling for the branches which execute identical products, diverts products of different type, downloads programs and reference data to the local controllers, receives information concerning the current state of the production and modifies the job flow according to temporary stops or failures in the individual branches.

The Dynamic Line Allocation Problem

Consider a plant that has information about the arrival schedule of its “inputs” over a planning cycle. The plant has parallel production lines for processing multiple types of products. However, changeover cost and changeover time are incurred when a line changes from processing one type of products to a different type of products. We present a dynamic line allocation problem that determines an optimal line allocation so that the total relevant cost (changeover and waiting costs) is minimized. In this paper we analyze the complexity of the problem and develop three different heuristics for generating near-optimal allocations.

MINLP model for cyclic multiproduct scheduling on continuous parallel lines

This paper addresses the problem of cyclic multiproduct scheduling on continuous parallel production lines. This plant configuration is typically used in the manufacturing of specialty chemicals. The problem involves a combinatorial part (assignment of products to lines and their sequencing in each li and a continuous part (duration of production runs and frequency of production). To account for these two elements, a large-scale mixed integer nonline program (MINLP) is developed and an exact reformulation technique is applied to linearize it in the space of the integer variables. The Kuhn-Tucker optimality conditions are exploited in the resulting model in order to effectively apply generalized Benders decomposition. This avoids the explicit solution of extremely large nonlinear subproblems. At the same time, a computational scheme based on valid outer-approximations of the nonlinear part of the problem is proposed to strengthen the bounds of the master problem and therefore achieve fast convergence. Despite the nonlinear nature of the model, special but important cases are identified for which certain convexity conditions are satisfied and the suggested procedure guarantees the globa optimality of the solution. The proposed technique was applied to a real world problem for a polymer production plant. The corresponding MINLP containe 780 binary variables, 23,000 continuous variables and 3200 constraints.

General reordering algorithm for scheduling of batch processes.

A sequencing algorithm applicable to various scheduling problems is proposed. It consists of two reordering operations, the insertion of a job and the exchange of two jobs. We propose a new reordering algorithm which can be used to solve scheduling problems of multiproduct processes with network structure.The proposed reordering algorithm is applied to the scheduling problem of a multiproduct batch process consisting of parallel production lines with a shared unit. It is shown that the simultaneous reordering of several jobs effectively avoids becoming trapped in a bad local optimum. To execute simultaneous reordering of jobs, an algorithm consisting of two steps, the aggregation of jobs and the reordering of aggregated jobs, is proposed.

Dynamic routing in reentrant flexible manufacturing systems

Consider a flexible manufacturing system (FMS), with several parallel production lines. Each line is statistically balanced. Due to process time and yield variations, some workstations may be temporarily starved of parts during the FMS operation, while others may have too many. The purpose of the dynamic routing algorithm described here is to achieve real-time load balancing in a stochastic processing environment and thus to increase the performance of the system in throughput, workload balance and reduced work-in-process queues. We formulate the problem and develop an optimal stationary policy (for two lines that have a material handling transport between them) based on the input buffer state of each station.

Microcomputer Control of a Printing Ink Plant

The manufacturing of printing inks can be considered as a multi-product batch technological system. The production of more than 2000 products take place by charges with identical or similar sequence of identical procedures on the basis of the recipes containing the technological instructions. The available items of the different equipment types may be allocated to simultaneously operating parallel production lines according to the production program. The goal of the control system elaborated for the new processing area of the BUDACOLOR Paint Factory /Hungary/ is to ensure the stationary processing of high-quality products by the concept of recipe controlled sequencing and data recording for the analysis of the processing system. The control system is based on an MPC-Z80 microcomputer and involves two levels of the computer control. The process management level performs the recipe handling and production programming. On the process control level the functions of process control, operator interface and documentation are accomplished. Both control levels are executed separately and consequently by the use of the program overlay technique. The successful combination of the process management and control levels on the basis of a 8-bit microcomputer configuration can be interesting for other batch-type technologies.

Petri net approach to the analysis of a structured program : G. S. Hura. Microelectron. Reliab.22 (3), 429 (1982)

This paper addresses the simultaneous lotsizing and scheduling of several products on non-identical parallel production lines (heterogeneous machines). The limited capacity of the production lines may be further reduced by sequence dependent setup times. Deterministic, dynamic demand of standard products has to be met without back-logging with the objective of minimizing sequence dependent setup, holding and production costs.The problem is heuristically solved by combining the local search metastrategies threshold accepting (TA) and simulated annealing (SA), respectively, with dual reoptimization. Such a solution approach has already proved to be successful for the single machine case. The solution quality and computational performance of the new heuristics are tested by means of real-world problems gathered from industry.

A Production Scheduling Problem in the Glass-Container Industry

By means of a computer simulation we examine the problem of scheduling parallel production lines in the glass-container industry with a resource constraint imposed by the furnace melting rate. The results of the simulation model are combined with relevant aspects of scheduling theory to arrive at the conclusion that a shortest processing time based dispatching rule probably provides the most efficient operating policy.

Scheduling method synchronizing two lines of activities and minimizing waiting and pass-time

Abstract In this paper, methods are suggested for solving a common class of job-shop scheduling problem. The type of job-shops considered consists of two parallel production lines ended by a group work station. The methods use a domination principle at first, of one line over the other, defining a master—slave hierarchy in the workshops. The solutions obtained from the optimal scheduling of the master line form the constraint domain of the slave line, the optimal schedules of which are worked out in turn. Parametrization of economical functions permits the dynamic modification of the optimization criteria of the slave line.

Scheduling Parallel Production Lines with Changeover Costs: Practical Application of a Quadratic Assignment/LP Approach

Production orders for a number of products must be scheduled on a number of similar production lines so as to minimize the sum of product-dependent changeover costs, production costs, and time-constraint penalties. We treat the problem by a quadratic assignment algorithm with a linear programming adjustment, and describe a successful practical application for chemical reactor scheduling.