Shenyang Machine Tool Co, the largest manufacturer of machine tools in China, has decided on EtherCAT as its bus system for the control platform of its latest intelligent CNC machine tool, the i5. EtherCAT was chosen not only for the master controller, but also on the slave side in all servo drives and I/O devices.
Shenyang Machine Tool Group is the largest manufacturer of machine tools in China. With over 300 machine types available in various versions, the company has become an important supplier on the global market. It covers all regions in China and exports to over 80 countries worldwide. The company is expected to continue leading the Chinese machinery industry in sales for years.
The Shanghai Research Institute, a subsidiary of Shenyang Machine Tool, has been engaged in innovative development in the fields of motion control and cloud-based manufacturing concepts since 2007. It concentrates on developing innovative motion and controller technologies for machine tools, product development and cloud-based manufacturing technology. This offers concrete benefits for Shenyang Machine Tool customers and their respective industries. The Shanghai Research Institute has developed a number of products for the business areas covered by Shenyang Machine Tool. These include CNC systems, servo drives and workshop information systems.
i5 intelligent CNC machine leverages EtherCAT for communication
The i5 intelligent CNC machine made its début in 2014 at the China CNC Machine Tools Fair. It boasts a variety of intelligent functions such as graphical diagnostics, real-time monitoring, remote diagnostics, 3D simulation and STEP programming. Due to its ability to offer individualised solutions, it is the perfect fit for the demands of today’s market.
The i5 name encompasses five features and terms that are embodied by the machine: industry, information, Internet, integrated management and intelligence.
The i5 control platform consisted of three component types: NC controller, HSHA series servo drives and I/O devices developed by the Shanghai Research Institute itself.
PC-based control technology, including the open, real-time industrial Ethernet protocol, EtherCAT formed the foundation for the i5 control platform. EtherCAT enabled Shenyang Machine Tool to create a CNC system with external servo drives that can also exchange data between I/Os and control at high speed and in real time. This offered users of this CNC machine tool a high performing control solution at a reasonable price through the use of cost-effective industrial Ethernet technologies.
Why EtherCAT?
Prior to the implementation of the device functionalities themselves, the Shanghai Research Institute carried out an extensive evaluation regarding the selection of a suitable bus system at the beginning of the i5 development process. The company decided on EtherCAT because, in addition to its performance, the i5 platform implements cloud connectivity via Ethernet. Because of its consistency, it was decided Ethernet should form the basis of the control bus system. This allowed Internet technologies to be integrated into the overall system seamlessly and made available at a reasonable price. In addition, the connection of a wide range of different devices was simplified.
The core technology of the i5 was the NC algorithm. Due to the high precision required of the high-end drive technology, the requirements for the bus system were very demanding. Besides ultra-short communication cycles, highly precise synchronisation was crucial. Additionally, achieving the smallest possible communication dead time regarding synchronisation was very important for Shenyang Machine Tool, as the process data communication of machine tools required a low deceleration to eliminate possible negative effects on NC characteristics by the bus performance. In addition to the enormously high communication speed achieved by EtherCAT with its processing on-the-fly principle, the mechanism of distributed clocks in EtherCAT also enabled the synchronisation of all slaves with a jitter of just 50 ns. Thus EtherCAT enabled the consistent movement of the feed axes during multi-axis contouring control, which reduced contouring errors dramatically. The EtherCAT slave controllers allowed the outputs to be set simultaneously and this simplified circuit design and the programming efforts for the real-time slave, leading to faster development and a shorter time to market.
EtherCAT’s mailbox protocol further accelerated the development process, particularly for complex applications and connections. Algorithms and parameters for function expansions, as well as firmware changes, could be integrated in the drives comfortably, even during application development. Furthermore, IT applications could be tunnelled through the mailbox via standard Internet technologies, simplifying the integration of high level management software.
Similar to other modern industries, manufacturers of CNC systems strive to offer higher performance machine functionality, while saving development and production costs. EtherCAT does not need any switches, routers or other active infrastructure components and requires little in the way of complex IT knowledge. No special, cost-intensive communication card is necessary for the CNC system and a standard Ethernet port is sufficient for data communication. The slave devices only required cost-effective EtherCAT Slave Controllers (ESCs) that could be integrated as an ASIC or IP core for FPGAs. The Shenyang Machine Tool i5 used ASIC chips from Beckhoff Automation for its servo drives and FPGA IP cores for its I/O panels to reduce costs effectively while simplifying the development process. With the decision to use EtherCAT, Shenyang Machine Tool did not need to invest in additional hardware and the performance of the i5 was enhanced enormously.
Especially in the field of complex CNC applications, user requirements for devices are very demanding. High availability, high precision, flexibility in programming, high efficiency and reliability are all very important. With EtherCAT these requirements can be met right down the line. Using EtherCAT instead of traditional analog data lines eliminates problems with electromagnetic interference and signal attenuation, significantly enhancing the reliability of the CNC system. Due to the environmental challenges in China, users require a high tolerance to temperature and humidity in their plants, especially in summer. EtherCAT eliminates the need for additional protection from electromagnetic influences in production facilities.
Saving time by increasing performance
After viewing the clear benefits of EtherCAT, Shenyang Machine Tool decided to implement EtherCAT-enabled PC-based control in its i5 intelligent machine tool.
The interpolation cycle was reduced from 4 down to 0,5 ms, increasing speed as well as the precision of the CNC system. The fast communication system reduced the response time of the PLC within the CNC system to one tenth of the original time. This enhanced the responsiveness of external devices and reduced processing time.
Production time and costs reduced
In traditional analog control methodology, each servo drive has to transmit an analog control signal to the CNC system and react to encoder signals. This requires the installation of a bus terminal, as well as a special cable for each drive in the CNC system. Since these cables are non-standard, manufacturers incur significant costs for material, installation and troubleshooting. In contrast, EtherCAT enables the use of standard Ethernet cables in all areas, which greatly reduces production time and costs.
Easier machine handling
EtherCAT enables a flexible and appropriate network topology that is easy to configure and diagnose. In one network, up to 65 535 EtherCAT devices can be connected without any topological restrictions. Servo drives, I/Os, operation panels, encoders and various sensors required for Shenyang Machine Tool’s i5 CNC system can be connected intelligently and problem-free with EtherCAT. The slave devices do not need an address switch for address configuration and EtherCAT’s protocol diagnostics can locate erroneous devices and signals with high speed and precise localisation.
For more information contact EtherCAT Technology Group, +49 911 540 56 226, [email protected], www.ethercat.org
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