Technical article
3 points where servo drives save resources
Whether it's the unspooling of closures and caps or the sealing of lids - servo technology already performs precise work in many areas of modern injection molding processes. For companies that are still hesitant about investing, it is worth looking at the cost savings and specific benefits in detail to make a far-sighted decision.
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Especially with injection molding machines, the choice of the drive system depends on many factors. In addition to considerations of cost-effectiveness, ecological issues are becoming increasingly important. Furthermore, not only should energy be saved, but at the same time cycle times should be shortened and downtime prevented.
This also applies to the choice of the drive solution for rotational and translational movements in injection molding tools. Additional aspects come into play here, such as availability, maintenance requirements, process reliability, etc. Especially for companies producing in large series, even small optimizations can have a noticeable impact. Let's take a closer look at the factors where servo technology can make the crucial difference compared to other drives.
1
Energy demand
Significantly lower power requirement for servo drives.
2
Maintenance required
Resource-efficient precision and cleanliness
3
Production efficiency
Servo drives score in speed.
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Energy demand - significantly lower power requirement with servo drive.
Energy savings are certainly one of the main reasons for purchasing a fully electric injection molding machine, as it only consumes power when opening and closing the injection mold and during injection. During the holding phases, energy consumption is practically zero. In fully hydraulic machines, on the other hand, the oil used for energy transfer must always be pressurized to the maximum pressure, which is why the motor of the hydraulic system operates with high power consumption – the result is significantly lower power requirements for electric machines. The same applies to the use of servo-electric drives in injection molding tools – these do not need to be connected to the hydraulic system of the injection molding machine and therefore operate completely independently of the operating status of the machine, with full power potential and low energy consumption at all times. This difference in energy efficiency was illustrated in a practical comparison between hydraulic, pneumatic, and electric drive units conducted at the University of Kassel. In this comparison, a load of 100 kg was moved using a pneumatic, a hydraulic, and an electric linear cylinder, and the energy required for this was measured. The measured energy consumption was then multiplied by a realistic number of annual operating hours (6000 hours in three-shift operation) and amounted to 8,380 kWh per year for the pneumatic cylinder, 3,602 kWh for the hydraulic cylinder, and 816 kWh for the electric cylinder. This meant that the linear cylinder showed savings of 77 percent compared to the hydraulic cylinder and as much as 90 percent compared to the pneumatic cylinder. In addition to cost savings, the higher energy efficiency also means significantly lower CO² emissions in production.
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Maintenance needs - Resource-saving precision and cleanliness
Where else can servoelectric drives score points besides high efficiency and low emissions? Thanks to their generally extremely high precision and repeatability—and thus minimal scrap and tool-friendly operation—the conservation of resources is already noticeable in lower raw material consumption, higher productivity, and lower maintenance requirements. In direct comparison to hydraulics, servo drives offer less torque for the same size – which is why the mechanics in a servo-driven system must be optimized and precisely tuned for maximum efficiency. However, the positive side effect is that there is little friction and stress during translational and rotational movements. Another aspect is the precise and optimally adjustable movement of servo-electric drives. Because lower mechanical forces are at work, servo-driven systems are also significantly gentler on tools, require less lubricant, and have longer maintenance cycles. Servo drives cannot leak and operate without consumables such as oil or filters, making them ideal for clean room conditions. But conventional production environments also benefit from the absence of oil, with significantly increased cleanliness and accelerated production start-up since no oil needs to be heated – in short: much fewer resources.
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Production efficiency - Servo drives score in speed.
Machines supported by servo drives not only work precisely and with high repeatability, but also quickly. The saving of cycle times, especially during threading or unthreading of thread cores, is significant compared to hydraulic motors. Times for unthreading thread cores are often reduced by more than half - and time savings can be realized by companies through parallel processes with the use of servo drives. This is often not possible with hydraulic drives, as there is only a limited oil flow rate available and the injection molding machine restricts the possibilities for additional parallel processes, for example during the opening movement. The continuous repeatability of the process additionally ensures higher production efficiency and, in total, a higher output.
The trend towards fully electric machines has been recognizable since the eighties and has been increasing in recent years. The logical consequence is to replace energy-intensive hydraulics with highly precise and efficient servo drives, even in processes such as those found in injection molding tools. In the long run, companies with high production volumes benefit from the savings that are present in every micron.
Especially in cleanroom environments, the trend clearly leans towards all-electric machines due to their low emissions, speed, precision, and energy-efficient operation. If you are considering using a servo-electric system to implement rotational and translational movements in your injection molding tool, it is best to consult experts to fully leverage the benefits of the technology with each movement.