End-to-end PC Control improves efficiency and quality in plastics processing | Efficiency, precision and reproducibility are fundamental requirements in plastics processing. Temperature control is, and always has been from the outset of plastics processing, a very important aspect. This topic is not in the least trivial, as it requires for relatively large cylinders, with their correspondingly high thermal inertia, to be heated. What is more, this thermal inertia must be managed and should be possible in the software, which is exactly what PC-based Control from Beckhoff was designed for. Packaging technology, characterised by the mass production of one-cent products and therefore demanding extremely productive and compact machinery, is one of the key applications for plastics.
In the plastics industry this means, above all, minimising non-productive time as, for instance, the time required for opening plastic moulds or for cooling. This can be achieved by deploying powerful control technology. It does, however, also demand correspondingly rapid actuator systems or drive technology, especially in handling.
PC-based control technology is able to process complex algorithms with sufficient speed while offering the detailed documentation required today. Examples of this technology are seen in TVs, PET bottles, etc. The flexible PC- and EtherCAT-based control technology is able to offer ideal automation solutions for injection moulding, blow molding and extrusion machines, as well as material handling systems.
The universal platform also seamlessly integrates safety and measurement technology alongside PLC, motion control and robotics functionalities. Plastics industry expertise from Beckhoff guarantees rapid and precise control of time-critical process variables such as speed and pressure, along with the control of hydraulic, electrical and hybrid drive systems. The servo motors and drives made by the company are particularly suitable for energy-efficient machine designs. Mention must also be made of the wide range of EtherCAT terminals for capturing energy data, e.g. for grid monitoring.
The information gathered by these I/O components can help initiate comprehensive energy management in conjunction with the relevant functions in TwinCAT automation software. Most plastics machines, meaning injection moulding machines, are still driven hydraulically as this allows high forces to be generated at relatively low cost. The trend here, however, towards greater precision, reproducibility and energy efficiency clearly favours electrical drive technology. This trend has been seen for some time now in areas that demand high precision or hygiene.
There is also a second aspect: servo hydraulics, i.e. hydraulic pumps driven by servo motors. Thanks to the advanced control characteristics – e.g. for stopping in a cooling phase – a great deal of energy can be saved with servo pumps of this kind compared with the combination of an asynchronous motor and a hydraulic variable displacement pump.
Handling is of particular importance when it comes to plastics machines and the AM8000 series by the company with highly dynamic servo motors and One Cable Technology (OCT) represents a notable innovation, especially in the motor-intensive handling sector. With this one cable solution, feedback signals are transmitted interference-free over a digital interface directly and together with the voltage supply through the motor connection cable.
The AX5000 series servo amplifiers supply higher power up to 170 A. Highly productive manufacturing cells require rapid handling systems, e.g. for in-mould labeling. TwinCAT is able to offer practical solutions for this with its powerful NC functions. This results in less expensive, more compact and, above all, more flexible machines.
The TwinCAT Kinematic Transformation software integrates a robot control system seamlessly into the TwinCAT automation suite and thus into standard control technology. As part of their scientific automation technology, the PLC, motion control, HMI, measurement technology and robotics can all run together on an industrial PC. The software is configured and programmed in a single Twin- CAT environment so that there is no need for special robotics tools, languages, or even a robot control system so engineering efforts can be significantly reduced.
Cartesian, articulated arm and SCARA robot types are implemented as kinematics systems. The software also offers tracking functionality to synchronise the robot with a moving object. Seamless integration is also supported by their hardware: robust IP 67 I/O components can be deployed outside of electrical cabinets, directly in the robotics environment. Here, the EP1816-3008 EtherCAT box, which can be installed directly on moving robot elements offers great advantages: it captures binary control signals with 16 digital inputs and also incorporates two three-axis acceleration sensors.
EtherCAT communication also plays a very important role when it comes to innovative plastics machines. On one hand, while machine builders in the plastics industry benefit from the openness and widespread market penetration of the EtherCAT standard, the choice of third-party components is practically unlimited. On the other hand, the extremely high performance of EtherCAT communication creates opportunities for innovations, particularly in the form of eXtreme Fast Control Technology (XFC).
XFC is based on an optimised control and communications architecture that consists of a modern industrial PC, ultrafast Ether- CAT terminals, EtherCAT itself and TwinCAT automation software. I/O response times better than 100 μs can be achieved with this seamlessly integrated system, opening up new possibilities for process optimisations. For example, very fast algorithms are required when injecting plastic into the mould in order to switch over to holding pressure at precisely the right moment during the injection process.
XFC enables the associated pressure curve to be resolved to an extremely high degree. Thanks to oversampling this can even be clearly below the minimum I/O response time and using distributed, synchronised clocks, at precisely defined times. This results in very precise process control, exact reproducibility and ultimately high quality and minimised consumption of raw materials. The outstanding features of the XFC technology and its potential for process optimisation have been proven in practical use with injection moulding applications.