Font Size: a A A

Research On Production Control Approach For Mould Manufacturing System Based On Workload Control Concept

Posted on:2012-10-14Degree:DoctorType:Dissertation
Country:ChinaCandidate:J J LiuFull Text:PDF
GTID:1112330368983091Subject:Mechanical and electrical engineering
Abstract/Summary:PDF Full Text Request
Mould is a kind of technological equipment in industrial productions, whose manufacturing abilities have been an important symbol to measure industrial production abilities of a country. Nevertheless, the production lead time of mould is often too long in our mould companies so that mould orders delay frequently. The problem influences seriously the reputation of companies, which is the key factor to restrict international competitiveness of our mould companies. The main reason is because mould companies lack an effective and proper production control approach. Most of classical production planning and control approaches derived from the repeat production environments, such as MRP and JIT. Both the literature and the practice have proved that these approaches are not suitable for mould industry. Workload control (WLC) concept is one of few PPC concepts that have been designed specifically for make-to-order (MTO) environments with high complexity. Based on the three control level of the WLC structure, it can conclude:the WLC is a feasible technology to achieve workload balance of manufacturing system. In mould production environment with highly stochastic and uncertain, achieving workload balance in mould companies is the key to insure the due dates of mould orders. Hence, the final aim of this paper is to design a WLC-based workload balance control system for mould manufacturing system.Due to the misalignment between theory and practice, very few successful implementations of WLC have been described in the literature. In this paper, we firstly identify these distinctive characteristics of mould production. The possible match between the distinguishing characteristics and the inherent characteristics of the WLC concept is analyzed, and, based on the resulting insights; this paper then refines the WLC structure, consequently to develop a multi-layer and hierarchical workload balance control structure for mould manufacturing system. At the same time, the relations between different control levels are considered. Finally, a software system for workload control is designed and implemented in a real-life mould company. The preliminary feedback from company managers about the system is encouraging. The main works of this paper are following:Firstly, two steps are used to evaluate the fit between the mould company and the WLC. The first step analyze whether it can align between the distinctive characteristics of mould production and the WLC in order to obtain an overall impression. Then the second step further use an evaluation framework to demonstrate WLC suitability in getting a detailed analysis. According to the evaluation, the hierarchical workload balance control structure for mould industry is proposed, which includes four levels:job dispatching level, job release level, order release level and order entry level. Both input-output workload control mechanisms for each of these levels are presented.Secondly, a decision-making structure for workload balance control in the order entry level is developed. Compared to the similar researches, a distinguishing feature of the structure is to take into consideration various uncertainties within mould production process via a stochastic state evolution model. In the decision-making flow, the evaluation method of mould importance rate is firstly presented. Then, a capacity check model for the new orders with fixed due dates and a due date setting algorithm for the new orders with negotiable due dates are developed. Moreover, the available capacity adjustments of enterprise layer in the above decision processes are defined. Finally, a numerical example of a real-life mould production system is studied and shown to be more suitable for a stochastic environment than related research.Thirdly, this paper presents three key strategies for order release control:determining the size of the order pool based on equivalent workload, calculating the aggregation workload of mould components and choosing the released components based on integer programming. Considering the characteristics of mould shop floor, the strategies for job release control are also developed, mainly including:calculating the already workload on work centers based on corrected atemporal method and determining the workload bound of shop floor based on simulation optimization method. Moreover, the simulation model for mould manufacturing system is established and, relevant simulation experiments are implemented to confirm the feasibility of the proposed approaches. Finally, the output workload control approaches for the production department layer and the shop floor layer are developed, mainly including:an optimization model for choosing the subcontracting jobs. A hybrid genetic algorithm for solving the problem is found and, its practicability is demonstrated by a real case.Fourthly, the job dispatching problems of the two types of working team in mould shop floor are firstly analyzed in the WLC-based environments. Then, for the mould heat-treatment shop floor, this paper develops its production control mechanism in dynamic environment and its multi-objective optimization model for job dispatching. A new batch process control strategy based on rolling-scheduling is proposed to solve this problem. Its time complexity is then presented. The potential features of the proposed strategy are demonstrated by an application example of a real-life mould production system finally.Finally, considering the real-life operation characteristics for our cooperative enterprise, the overall operation flow and systemic function of the workload control system are designed. Then the problems that occur in the starting stage of system implementation are summarized and, a simulation workload control system is advised to solve partial these problems. The design related to the simulation system is provided at the same time.Based on the above theory and application research, we argue that the workload balance problem for mould manufacturing system can solved initially. The relevant research conclusions of this paper can provide mould companies the theory and approach support for the effective production control.
Keywords/Search Tags:Mould Industry, Production Planning and Control, Workload Balance Control, Workload Control Concept, ETO
PDF Full Text Request
Related items