Samenvatting

Energy usage is a fundamental property of injection molding machines. The development of these machines is accompanied by two contradictory objectives. On the one hand, a producer wants to produce as quickly as possible, cycle times must be as short as possible, and the number of products produced simultaneously must be as high as possible. On the other hand, the importance of energy-efficient production is increasing, but it is contrary to the previous desire. Energy usage in the industry is a hot topic, wherein energy consumption and grid load are crucial characteristics. The current hydraulic injection molding machine from Stork IMM has a lot of energy loss and thus consumption in comparison to a full electric molding machine. The electric drive can recover large amounts of energy by using the motor as a generator during braking hases. However, the electric drive components are very large to provide required peak powers, resulting in more rotational inertia and costs.
This report examines whether a hybrid drive is technically feasible, wherein the electric drive is constructed smaller and a separate hydraulic drive assists to provide peak powers.
The research starts with a thorough examination of the current injection molding machines. The current energy consumption and operating speeds are benchmarks for a new concept. Hereafter, concepts for a hybrid drive are designed. Considerations concerning the release, recovery, and storage of energy are assiduously examined and weighed. A calculation model is constructed to properly graph the behavior of the machines with changing masses, accelerations, and cycle times. In the extensive calculation model, many iterations are done in the aforementioned changing parameters. Interesting conclusions about energy and power users emerge from the calculation. The energy efficiency, technical integration, and costs are conclusively the parameters by which the new concept is compared with the current drive.
In the concept, an electric motor together with a hydraulic motor is mounted in parallel on the gearbox, in which the rotating movement is linearized with a gear rack. The opening and closing of the mold can be performed hybrid (fast) or fully electric (energy efficient). Both drives are required during the mold pressing phase to ensure enough closing power. The recovery of kinetic and rotational energy is carried out purely electrically. The recovered energy is passed between the electric and hydraulic drive frequency converters, hereafter the energy is stored in hydraulic accumulators. The new concept in electric mode is just as fast as the current drive, while half the size of the motor has been used. This reduces the rotational energy demand. In hybrid mode, the cycle time can be reduced. Energy consumption decreases by 7.7% and the concept has major consequences for the grid load. The peak return of energy on the grid and the peak usage of the hydraulic system cancel each other out and the energy is used directly within the limits of the machine. The lowering of the grid load and energy consumption makes the concept very interesting. Moreover, the concept is roughly equal in costs and even allows faster operation. In addition, it appeared that the current electrical cycle time can be reduced by 11 percent. This is just as fast as the hybrid concept in hybrid mode, but much more energy efficient.