Key Highlights:
- Over the past decade, high dynamic performance (HDP) electric motors have emerged as superior alternatives to their older DC counterparts in plastic processing.
- Plastic manufacturing faces challenges related to the limitations of traditional DC motors and standard AC motors.
- HDP motors offer advantages in plastic production, including low rotor inertia for faster cycling times, and high power density.
From cast film extrusion to injection moulding, blow moulding, blown film lines, and more, electric motors are critical at almost every step of plastic processing.
Due to rapid advancements in motor technology over the past decade, the newest high dynamic performance (HDP) electric motors have overcome numerous limitations of their older DC counterparts. They offer benefits in size, precision, and other critical areas, giving plastics OEM machine builders and end users a competitive edge in productivity.
Fausto Belotti, global segment manager, Rubber and Plastics, ABB Motion, dissects the industry challenges that HDP motors can address.
Mainstream challenges
Machine builders and users in plastic manufacturing are deeply immersed in digitalisation, having already progressed to the second era of this transformative process. Initially, they focused on establishing and managing manufacturing execution systems (MES). Now, in this second phase, they aim to drill deeper into the component aspect, such as motors, drives, PLCs, HMIs, and sensors.
Historically, plastics processing facilities relied on low-powered DC motors for motor-driven equipment despite their drawbacks. These motors are bulky, lack energy efficiency, and pose maintenance challenges, mainly due to the wear-prone carbon brushes, leading to shortened machinery lifespan.
In contrast, modern machinery employs AC motors, offering various advantages. Yet, standard AC motors come with their own set of limitations. The most significant is their high rotor inertia, which complicates their precise control. This presents a considerable challenge in the latest plastic applications, where high productivity levels are required in terms of pieces per hour, and consistent product quality demands such control.
The unit price of many items in plastic production is typically only a few cents, such as the plastic cap of a PET water bottle. Since the production cost is low, manufacturers must produce a high volume of pieces per hour to make it feasible. Therefore, high motor reliability is critical. Furthermore, in the plastics industry, labour costs are equivalent to electricity costs. To control the latter, machine builders and end users want motors that also offer superior energy efficiency.
Another major challenge facing plastic producers is the cost of downtime. For instance, a PET line can produce approximately 2,000 1.5L bottles per hour. During downtime, production halts, causing bottlenecks, and the entire 40m-long production line comes to a standstill. This downtime could result in losses amounting to several thousand dollars per hour.
Specialised AC motors – often called square frame induction motors, low inertia motors, or vector motors – offer a proven solution. Models like ABB’s HDP motors demonstrate substantially higher power density compared to conventional AC motors. The main features of HDP motors are their rectangular housing, light and robust construction, high dynamic performance, and excellent power-to-size ratio.
The benefits of HDP motors
HDP motors offer numerous advantages in plastic production applications. Their low rotor inertia, high overload capacity, and exceptional dynamic response translate into significant production benefits. The motor’s low rotor inertia allows faster cycling times, enabling controlled machinery movements and rotation with greater speed and precision. This advantage can lead to a productivity increase of up to 15% when compared to standard AC motors.
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Full range of machinery motors optimised for high power density
The high power density of HDP motors makes them notably more compact than other motor types. Consequently, they require a smaller installation area, allowing for a reduced footprint or accommodating more plastic lines within the same space. However, this compactness may restrict access space for maintenance, which is why the motor’s high-reliability design is crucial. Additionally, in regions where space is at a premium and costly, HDP motors offer an ideal solution, enabling higher production within the same confined space.
A noteworthy benefit for OEMs is that they have the flexibility to make late configurations to the HDP motors to suit their applications better, even if they’re already in their workshops.
Drives for precision control
A further advantage is that the HDP motors are part of a complete package with variable speed drives (VSDs). A VSD allows precise motor control by adjusting the supplied electricity’s voltage and frequency. Motor-drive packages provide significant precision advantages and are well-suited for applications like mixers, extruders, conveyors, injection moulders, and more. ABB VSDs are specifically designed to seamlessly integrate with HDP motors for the best possible performance solution.
Moreover, VSDs enhance energy efficiency in motors. Without VSD control, motors run at full speed, consuming more power. Even minor reductions in total speed, as seen in processes like extrusion, lead to significant energy savings. For example, reducing a motor’s speed by just 20 percent using a drive can cut its energy consumption by half.
Specifying the same brand of motor and drive enables additional optimisation, boosting the system’s energy efficiency while reducing harmful harmonics. Consequently, this allows the utilisation of lower cable cross-sections alongside a smaller transformer, reducing overall costs.
Reduced need for maintenance
HDP motors offer significant maintenance benefits since they are also designed for intensive work in applications where lots of plastic dust is present. The motors are brushless, containing fewer moving parts than DC motors. Although engineered for intensive use, they are, therefore, easier to maintain and inherently more reliable.
It's also possible to specify liquid-cooled solutions. Such an option provides a perfect seal, safeguarding the motor’s internal components from plastic dust that might cause wear or failure. Liquid cooling is also significantly more efficient than air cooling, enabling a further increase in power density compared to standard air-cooled HDP motors. In addition, liquid-cooled motors eliminate the need for fans aligned to the shaft, enhancing their efficiency.
The water jacket also diminishes motor noise, contributing to a more pleasant work environment. Liquid-cooled HDP motors are particularly advantageous in the plastics industry, where water is readily available in plants as part of the production process.
HDP motors can provide power output of up to 2 megawatts (MW). They are available in diverse frame sizes, ranging from 80 to 400, with different designs. This versatility simplifies the integration of HDP motors into various machine types. There are options for high-speed and liquid-cooled models, and HDP motors can be used with integrated mechanical brakes. HDP motors are also compatible with programmable encoders.
Suitable for new and existing installations
Machine builders can capitalise on the high power density of HDP motors in two ways. Due to their common frame sizes, they can be used to retrofit an existing machine. Even if there is no increase in the current operational speed, operators still gain advantages from the new motor’s improved inertial properties, overload capacity, and responsiveness.
In new installations, a facility can specify a smaller low-inertia HDP motor to achieve equivalent work as a larger, higher-inertia model. Even at the same IP rating, a new HDP model is generally at least one frame size smaller than a standard induction motor. Consequently, the machinery takes up less floor space, enabling the facility to accommodate more equipment and increase throughput.
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Plastic manufacturers can access the benefits of HDP motors in both retrofits and new installations
More power, better products
In the competitive plastics industry, machine builders and end users are under immense pressure to deliver high-quality products at affordable prices. The most effective approach to achieving this goal is investing in equipment that maximises throughput and increases product consistency.
Machine builders need to partner with a global player that offers comprehensive support worldwide, including easy access to spare parts procurement. Flexibility is another key aspect since machine builders require adaptable solutions, such as a single drive that can accommodate various shaft or axle requirements and formats.
HDP motors stand out due to their higher torque and smaller size in comparison to conventional AC motors. Additionally, they offer major advantages over the DC motors still in use at some facilities. This makes HDP motors the clear choice for upgrading existing systems and specifying new equipment within plastic facilities. A matching motor and drive package offers the complete solution.