Electric drive concept for injection molding machines

For many years now, Baumüller has placed an increased focus on the development of energy-efficient drive concepts for the injection molding industry. The efficient use of resources has always been an important issue at Baumüller. This is reflected not only in pioneering work in the field of direct drive technology, but also in the development of the first fully electric injection molding machine in Europe. This was implemented at the end of the 90s with drive technology from Baumüller. At that time, servo drives that were interconnected via a common DC link were already in use, allowing highly energy-efficient operation.

Building on this foundation, Baumüller continuously developed and expanded its solution portfolio for energy-efficient synchronous drive technology.

The result is a broad range of servo converters combined with regenerative systems, intelligent software and simulation solutions, as well as synchronous technology and direct drive technology. The products of drive technology make an important contribution to the energy-efficient and precise production of even highly complex plastic parts.

Baumüller offers a wide range of system solutions for the injection molding industry. The best choice of system depends primarily on the product manufactured by the machine and thus on the machine configuration. The number of axes to be electrified also plays an important role.

The flexible servo converter portfolio enables the combination of the required drive axes with a feed or regenerative feedback unit. In addition, it is also possible to combine the drive axes of the module system with a mono unit without a separate feed unit if, for example, a very powerful drive axis is required. In this case, the mono unit acts both as a feed unit for the axis group and as a servo drive. The respective systems work together in a common DC link, enabling energy-efficient operation.

Optionally, a capacity module can be integrated into the DC link for the intermediate storage of excess energy. This means that energy can be stored and freed up again as needed in the event of a power failure or when braking the drive axes. Furthermore, after a power failure or malfunction, it is possible to move the drive axes to a defined position depending on the available residual energy. This prevents damage and accelerates a machine restart.

In addition to supplying power to the power modules, the use of a regenerative feed unit also enables the sinusoidal feedback of excess braking energy into the mains. This regenerative system thereby makes an additional contribution to reducing energy consumption.

For servo-hydraulic machines with one electric axis, a powerful mono unit is used in combination with a compact and dynamic servo motor.

This combines the advantages of hydraulic power transmission with the control quality and dynamics of energy-efficient electric drive technology in conjunction with intelligent software. A great deal of energy can be saved with this configuration. In the field of plastic injection molding machines, the servo-hydraulic drive has already established itself as a standard.

All three drive solutions are both compact and scalable and allow high power density. Moreover, thanks to the identical controller firmware, the expenses for project planning, maintenance, and even service are reduced during the life cycle of the machine.   

Thanks to servo converter intelligence, it is still possible to work with extreme precision in the execution of highly dynamic movements and also to respond extremely quickly to error messages. In addition, the integrated programmable softdrivePLC allows easy links between digital I/Os, technology functions or data analyses to be implemented directly in the drive. One example is the servo hydraulics technology function, which enables highly dynamic and intelligent pressure and flow rate control. The advantages of drive-integrated intelligence and fast control can also be applied to electromechanical axes, such as gantry functions.

The use of ProSimulation also enables efficient drive dimensioning, shortened commissioning times, and improved service quality for the topologies mentioned above. Simultaneous engineering allows development times to be reduced and acquisition and life cycle costs to be lowered.

The topic of digitalization is also an important catalyst for achieving climate targets. Networking allows the potential of the drive technology and thus of injection molding machines to be fully realized. State-of-the-art communication interfaces are particularly important in this regard. Ethernet-based fieldbuses, for example, enable vertical integration into the machine’s control architecture. b maXX servo drives can be used for all commonly used bus systems.

In addition, numerous controller functionalities help to ensure that the injection molding machine delivers perfect results around the clock. High machine availability, better repeat accuracy during production, and a reduced use of materials thanks to shorter start-up times after tooling are solid advantages.

If the encoder fails during the process of closing the injection mold, major damage may occur to the cost-intensive closing tool of the injection molding machine as a result of the uncontrolled movement of the closing mechanism. Depending on the specific damage, this can result in a prolonged and expensive production downtime. The patent-pending “error response to encoder failure” function was developed to solve this very problem. The controller firmware in the servo converters checks the status of the encoder every microsecond.

In the event of an encoder failure, it automatically switches from closed-loop control to V/f operation. Depending on the parameterization of the controller, the system is then immediately braked and brought to a standstill. At the same time, information can be sent to the control unit via the fieldbus. This ensures that the machine shuts down in a controlled and synchronized manner. This way, the closing process is completed with no damage and the machine comes to a standstill.

In larger injection molding machines, two gantry axes are often employed to execute the movement of the injection axes. This allows the force to be divided between two axes. If one axis fails and the other continues to move, the injection axis will tilt. This can cause mechanical damage, bringing high repair costs and production losses in its wake. The “gantry function with synchronous error response” prevents tilting. Even if a fault occurs, both axes always act synchronously, i.e. they execute identical movements simultaneously. This happens automatically after an error is detected and with no time delay. As soon as the error has been eliminated, the axes can resume gantry operation. This fully excludes the possibility of mechanical damage.