By Kris Thacker, Technical Sales Manager, Sumitomo (SHI) Demag
It is widely accepted that drive controls play a pivotal role in injection moulding machines. However, there remains some ambiguity about how significantly they influence overall performance. Kris Thacker, Technical Sales Manager, Sumitomo (SHI) Demag clarifies that drive controls are unquestionably fundamental to the machine’s operational capabilities.
Over the years, drive technology has seen incremental improvements, leading to variations in performance across different models. Some drives are designed to achieve faster acceleration and enable quicker braking, enhancing productivity and cycle times. Others are engineered with a focus on energy efficiency, helping processors reduce power consumption and operational costs.
Ultimately, the choice of drive control can shape not only the speed and responsiveness of the machine, but also its energy profile and suitability for specific moulding applications. As drive technologies continue to evolve, understanding these distinctions becomes essential for optimising both performance and efficiency in injection moulding operations.
Tracking the evolution of efficiency
Controlling the injection pressure and process optimisation is essential for mouldability as this precise motion control is what the drive achieves. Much like a gearbox, the drive in every injection moulding machine transforms the rotational speed into a linear movement. The science is the same for all drives across the ages, whether it is hybrid, variable frequency, electric servos, electric belt, direct drives or all-electric drives.
The choice of drive in injection moulding used to be application dependent as the requirements for sector and processing applications need to factor in so many varying aspects. This included holding patterns, rapid changes in acceleration and deceleration, cooling times and component removal.
With the arrival of mass production and trade globalisation, the 1980s and 1990s machine hierarchy was characterised by widespread adoption of hydraulic drives. These were hydraulic fixed displacement or hydraulic variable displacement drives, and featured a motor, pump, valve and hydromotor. The fact many mould shops continue to use these machines is testament to their robustness and longevity.
However, a score of 0.46 for relative efficiency in today’s manufacturing climate is not great. It means that more than half of the input energy is being wasted. This could be improved by optimising processing parameters. Yet, given the elevated energy costs, a relative efficiency rating of 0.46 strongly suggests that your current machine may have reached a point of significant inefficiency.
Switching to a model with an all-electric belt drive or direct drive will reduce cycle time, save energy and improve moulding precision and part quality. Resulting in long-term operational savings.
Sitting between all-electric and hydraulics are servo hydraulic systems. These provide a high-performance and more energy-efficient alternative, while retaining the benefits of hydraulic force. Often achieving a relative efficiency rating of over 0.85, these moulding machines use a variable speed drive motor to drive either a fixed or variable displacement pump.
Found predominantly in advanced manufacturing, robotics, automotive and aerospace, the servo hydraulic market still supports manufacturers. Now, the focus is on the next generation of servo motors. These will be powered by drives that combine the power density of hydraulics with the precision, control, energy efficiency and smart connectivity of electric drives.
Optimised electric efficiency
At 0.92 relative efficiency, high torque electric direct drives represent the most consistent efficiency benchmark. Some of the highest performing machines with all electric drives can reduce energy consumption by over 80% compared to hydraulic technology. Additionally, the evolution of technologies now means that electric drives are increasingly viable for processing faster applications including caps and closures, as well as heavier loads such as automotive parts.
But even here, electric drive variants can and do vary. For example, an all-electric direct drive can be very different to a belt drive electric axis. A belt drive for example will typically couple the servo motor to the axis via a belt and ball screw assembly. Although noisy (from rotational velocity) and more complex to control, its relatively low mass and low inertia support quick and precise changes.
Conversely, an all-electric direct drive will couple the motor to the ball screw controls. This is especially important for controlling platen stiffness. These drives adapt especially well to velocity changes, with little overshoot. Marginally more energy efficient (~4-5%) than belt/ gear systems, all-electric direct drives can also perform several tasks simultaneously in parallel operation.
Sumitomo (SHI) Demag, the company that pioneered the drive concept a century ago, continues to distinguish itself in the market through its advanced electric direct drive technology. This too has a huge impact on efficiency and machine reliability.
Unlike other engineering companies, Sumitomo (SHI) Demag is the only known global firm in this field to design and manufacture its own drive motors entirely in-house. This means that all drives are tailored to meet the unique operational demands of injection moulding machines.
From the perspective of relative efficiency, this integrated process plays a significant role in improving operational performance, expanding production capacity and further advancing energy efficiency.
