Development of simulation system for evaluating productivity and energy consumption in production lines including injection molding machine

Abstract

To improve productivity and energy efficiency, attention has been paid to practical methods to evaluate productivity and energy consumption in actual manufacturing processes. In the plastics industry, the injection molding machine is one of the common production machines for manufacturing plastic parts. It consumes a large amount of energy due to having injection molding processes such as melting the material. In addition, a production line including the injection molding machine generally has various auxiliary machines to improve productivity and maintain product quality. Since the states of each machine in the production line change based on production situations, the behavior of energy consumption in the production line becomes more complicated. Therefore, it is difficult to evaluate energy consumption in the production line while grasping dynamically changing the states of each machine. This paper proposes a simulation system that simultaneously evaluates productivity and energy consumption in the production lines including the injection molding machine for design and improvement of production line. To simulate productivity and energy consumption, we develop a state transition model in the production line. This model defines the interrelationship between state transitions and their sequence among the machines. Furthermore, by making a correlation between the machine state and its energy consumption, the state transition model enables to calculate energy consumption in various production scenarios. By implementing the state transition model in a discrete-event simulation, it is possible to evaluate the indicators of productivity and energy consumption such as throughput and specific energy consumption. To verify the effectiveness of the proposed simulation system, we show a case study of productivity and energy consumption when designing a new production line including an injection molding machine. The results show that we obtain the evaluation indicators of productivity and energy consumption regarding various production lines.

Simulated annealing based simulation method for minimizing electricity cost considering production line scheduling including injection molding machines

“…Previous research proposed state transition models for four kinds of machines (Takasaki et al, 2017;Kaifuku et al, 2019). By relating the proposed state transition models to the electric consumption of each machine, it is possible to simultaneously evaluate the productivity and energy consumption of the entire production line.…”

“…Additionally, to calculate the contract electric power and electric power consumption, data concerning the state of use of electric power are necessary. Therefore, we use a model of an injection molding line and a simulation in which the model is installed, as have been proposed by the previous research (Takasaki et al, 2017;Kaifuku et al, 2019).…”

“…STEP 1-1: calculate the contract electric energy and electric power consumption of the initial solution using the method proposed (Takasaki et al, 2017;Kaifuku et al, 2019). STEP 1-2: using the value calculated in STEP 1-1, calculate the electricity cost of the initial solution.…”

“…Subsequently, the initial solution is considered as the present solution. STEP 1-3: using the method proposed (Takasaki et al, 2017;Kaifuku et al, 2019), calculate the contract electric power and electric power consumption of the neighborhood solution. STEP 1-4: using the value calculated in STEP 1-3, calculate the electricity cost of the neighborhood solution.…”

“…Therefore, an energy evaluation of the entire production line including the injection molding machine was excluded. Recently, simulation-based methods have been proposed to evaluate the productivity and energy consumption of production lines including injection molding machines (Takasaki et al, 2017;Kaifuku et al, 2019). As a result, it is becoming possible to evaluate in advance the productivity and energy consumption of production lines including injection molding machines at a design stage.…”