Marcin Zemczak

Preparatory Stages of the Production Scheduling of Complex and Multivariant Products Structures

The paper presents the way of creating a scheduling model for manufacturing systems where complex and multivariant structures of products are considered. Described method of scheduling tasks modelling, based on graphs, includes stages of building graphs of operations planning sequence of orders (taking into account their scheduling strategies and alternatives of realisation), input sequencing of the set of production orders and also creation of the aggregated graph of operations planning of the set of orders. The developed model is the basis for the implementation in the APS and simulation type of scheduling software, supporting production planning and scheduling. Because of NP-complete character of considered scheduling tasks, it is a potential application area of soft computing graph searching techniques.

Multi-assortment rhythmic production planning and control

A method for production planning in a repetitive manufacturing system which allows for estimating the possibility of processing work orders in due time is presented. The difference between two approaches are presented; the first one one-piece flow elaborated in Toyota and the second one elaborated by authors that consists in defining sufficient conditions to filter all solutions and providing a set of admissible solutions for both the client and the producer. In the paper attention is focused on the buffer allocation. Illustrative examples are presented.

Two-Stage orders sequencing system for mixed-model assembly

In the paper, the authors focus on the NP-hard problem of orders sequencing, formulated similarly to Car Sequencing Problem (CSP). The object of the research is the assembly line in an automotive industry company, on which few different models of products, each in a certain number of versions, are assembled on the shared resources, set in a line. Such production type is usually determined as a mixed-model production, and arose from the necessity of manufacturing customized products on the basis of very specific orders from single clients. The producers are nowadays obliged to provide each client the possibility to determine a huge amount of the features of the product they are willing to buy, as the competition in the automotive market is large. Due to the previously mentioned nature of the problem (NP-hard), in the given time period only satisfactory solutions are sought, as the optimal solution method has not yet been found. Most of the researchers that implemented inaccurate methods (e.g. evolutionary algorithms) to solving sequencing problems dropped the research after testing phase, as they were not able to obtain reproducible results, and met problems while determining the quality of the received solutions. Therefore a new approach to solving the problem, presented in this paper as a sequencing system is being developed. The sequencing system consists of a set of determined rules, implemented into computer environment. The system itself works in two stages. First of them is connected with the determination of a place in the storage buffer to which certain production orders should be sent. In the second stage of functioning, precise sets of sequences are determined and evaluated for certain parts of the storage buffer under certain criteria.

Multistage Sequencing System for Complex Mixed-Model Assembly Problems

The paper presents the concept of multistage sequencing system which main task is to aid the processes of production scheduling in modern assembly systems, mainly in automotive industry, but also in other industry branches, where mixed-model production is conducted. Because of NP-hard character of considered scheduling tasks, it is a potential application area of soft computing graph searching techniques. Described sequencing system is a tool for production scheduling optimizing the process in terms defined by the user (e.g. the number of cycle times exceeded on the assembly line stations as well as the average exceeding of the cycle time). The system structure is based on graph searching techniques, and may be implemented in many problems solving methods, including not only production scheduling but also others, e.g. project scheduling. The developed system model is the basis of its implementation in production planning software, creating the sequences of production orders in few different stages.

An Idea of the Continuous Flow for Concurrent Multi-Assortment Production

Nowadays in the era of advanced stage of Lean Manufacturing concept forces manufacturers to research of new idea of the production flow organization and to implement more and more innovative organizational solutions. The article presents the authors concept of implementation the combination of continuous flow and concurrent multi assortment production. Continuous flow is an approach to discrete manufacturing that contrast with batch production and is associated with just-in-time and Kanban production. The goal is an optimal balanced line. The paradigm aim is to achieve single-piece flow. For this purpose the similarity of the products that use the shared resources and start their production one by one in a predetermined sequence is searched. In addition, it is recommended to transform the internal setup into external one for eliminating investment in set-up times. This concept is similar to the group technology developed down in 70’s and based on the classification of products into four groups.

Application of Graph Theory for Production Orders Sequencing in Mixed-Model Production Systems

In this paper, problem of sequencing of production orders in mixed-model assembly systems is being analysed. The sequencing in such system is mostly addressed as a CSP problem (Car Sequencing Problem) and due to the fact that no optimal method of solution has yet been found it belongs to the NP-hard problems [1,2]. The NP-hardness of the problem has been proven in [3]. The problem connected with proper sequencing arises from the fact that nowadays it’s the clients who have the biggest influence on the sellers offer. The possibility to customize almost each and every product complicates the production management, as instead of having 10 different products, the number of them may grow up to few hundreds [4]. The problem may be especially observed in automotive industry, however recently it may be also met in household appliances industry, as mass customization can be also observed on that market. Each product may differ in labor-effectiveness, and due to the fact of carrying the assembly in linear assembly systems, each unevenness, each transgression of takt time on a single work-station may lead to the line stoppage.

Statistical Methods in the Automotive Industry

Controlling of the manufacturing processes is one of the key factors that allow companies to produce goods of high quality. In the article one of methods of the quality management - statistical process control (SPC) has been discussed. On the example of the car headrests manufacturing enterprise benefits from applying this method have been presented. Authors pointed out that the use of statistical methods in decision-making processes must not be difficult and time-consuming, if is being supported by a computer with using inexpensive tools.

Production Orders Sequencing in Mixed-Model Assembly Lines

The paper presents the production orders sequencing issue, which main aim is to establish a proper sequence of tasks, that would maximize the utilization of companys production capacity. According to the literature research, the sequencing problem considered in the paper, may be denoted as CSP (Car Sequencing Problem) and belongs to the NP-hard class, as has been proven by simple reduction from Hamiltonians Path problem [1]. Optimal method of solution has not yet been found, therefore only approximate solutions have been offered [2]. Approximate solutions are based mainly on the evolutionary algorithms. However certain problems, as lack of possibility to check the effectiveness of the solution or the possibility to reach twice the same solution are observed. Regardless of the structure of specific assembly system, while considering reception of new tasks into the execution, current review of the state of the system is obligatory in order to decide whether, when and which new order can be accepted for assembly. In this paper, the problem of task scheduling is limited to the specific existing mixed-model production system. The main goal is to determine the effective method of creation of task sequence.