Hierarchical Load Control Method For The Blow Molding Machine Manufacturing Systems

Nowadays, plastic product is one of the most important new material that support the development of modern science technology information. It is an indispensable means of production for such important fields as energy, transportation, aerospace and marine development of the national economy. However, the bottle blowing machine, one of the main production machines in plastic manufacturing is characterized by its long manufacturing cycle, as well as the frequent tardiness for the orders, which has a great influence on the reputation both in enterprises and the all industry in China. The current situation that most of the bottle blowing machine manufacturers have low delivery rate but high cost of manufacture is a critical factor restricting the development of China’s bottle blowing manufacturing industry. Many investigations shows that the main reason of that situation is a lack of an effective production control method suitable for the characteristics of bottle blowing machines. Most of the traditional production control techniques are derived from the repeated production environment, such as MRP, JIT and so on, the theory and practice have proved that they are not suitable for bottle blowing machine manufacturing enterprises. Load control technology is a kind of special production control method to design a Make-to-Order enterprise complex production environment, from the three layer control structure which contains the we can get a preliminary conclusion:the technique is a feasible method to realize the system load balancing, while the key to ensure the delivery of bottle blowing machine lies in the realization of equalization of production load in the uncertain environment. e. In view of this, the aim of this paper is to research on the establishment of a production planning and controlling system suitable for the bottle blowing machine manufacturers, in order to enhancing the on-time delivery rate and lowering the manufacturing cost.Through many investigations of different bottle blowing manufacturers, the production management features of bottle blowing manufacturing systems can be concluded as follows:The orders arrive randomly and uncertainly in bottle blowing machine manufacturing enterprises; the bottle blowing machines have a great variety, they can be divided into ripe type and general type according to the popularity in market, while products of diverse popularity differ in their production organization; In the manufacturing process, the work pieces are highly flexible in technics, giving rise to the uncertainty in the technical routine of work pieces; In the manufacturing process, work pieces would be urgently repaired at random time with uncertain procedures. Those uncertain elements in the manufacturing process not only complicate the production management in bottle blowing machine manufacturing system, but also result in the high imbalance of work load in bottle blowing machine manufacturing system. After analysis, we can find that the problem of the low delivery date and high manufacturing cost mainly derive from the imbalance of work load in bottle blowing machine manufacturing system. Therefore, it is essential to adopt a production controlling method based on work load control theory to improve its on-time delivery capabilities and reduce its manufacturing costs.Because of the difference between theory and reality, workload control technology in the bottle blowing machine manufacturing enterprise application is very limited. So in this paper, the adaptability of workload control theory in bottle blowing machine manufacturing enterprises will be assessed firstly, concluding the real gap between theory and reality. Having taken full account of these gaps, a suited hierarchical workload balancing control structure can be established for bottle blowing machine manufacturing systems., Secondly, Considering the feature that bottle blowing machine manufacturing enterprise adopt a mixed production model combining pre-production and MTO, a suitable pre-cast orders mathematical model will be established for the bottle blowing machine manufacturing enterprises. Additionally, considering the procedures features of work pieces in bottle blowing machine, putting the work pieces with high process flexibility into the options of work piece job releasing, establish a mathematical model for the selection of work pieces job releasing of bottle blowing machine manufacturing enterprises. Finally, designing and implementing workload control and decision support system for the bottle blowing machine manufacturing enterprises. Based on the ideas stated above, the main research steps are summarized as follows:First of all, making a comprehensive assessment of the adaptability between theory and reality respectively from operational features of typical bottle blowing machine manufacturers. Based on the evaluation results, establish a suitable for bottle blowing machine manufacturing system, a multi-layers hierarchical workload balance control structure which contains order entrance layer, work piece job-releasing layer, work center procedure-shifting layer, and analyzing the input /output workload equalization control mechanisms mainly related to each structure, as well as the relationship between the layers. Secondly, Considering the mixed production mode in bottle blowing machine manufacturing enterprises that adopt a combination of MTO and ETO, the pre-cast order decision mainly depends on individual experience, lacking a scientific method to support the decision making, this paper mainly deals with the orders’ pre-casting decision. By researching on the order pre-cast decision problem, use the branch and bound algorithm for solving the mathematical model proposed, work out the optimal decision of the pre cast order combination.Thirdly, bottle blowing machine manufacturing workshop layer is mainly used for the realization of the comprehensive workload balance in the pre-casting period in the workshop. Considering the job releasing features of the blowing machine manufacturing enterprises, research on the three critical decisions, that is, the construction of task pool, the determination of job’s priority, estimation of the workload in work center, and job releasing selection based on the integer program. Take full account of the flexibility of the work piece procedure, establish a job releasing control strategy. Set up a mathematical model for job releasing selection, and use the branch and bound algorithm to work out the optimal job releasing combination as well as the optimal procedure routine. Fourthly, there are too many uncertain elements in real workshop, which will result in a deviation when the workload planning system transferring to the work center. Considering the variability of the actual environment in work shop, propose a procedure-shifting strategy, realizing the workload balance of each work center during the pre-cast period.Finally, based on theoretical research results obtained in the above steps, combined with the actual operation characteristics of the joint venture, design and develop a suitable production management system for bottle blowing machine manufacturing enterprise.