Seamless automation, sustainability and digitalisation with Festo electric drives Whether to use a stepper or a servo drive can be a tricky decision for machine builders and design engineers. The high dynamics and controllability of servo control loops are useful in many automation applications. On the other hand, there are times when the pulse, lock, stay and cost characteristics of a stepper are the better choice. The development of a new range of extra-low voltage servo drives means that this dilemma is now easily solved. Innovation in stepper motor technology means the gap between stepper and servo technology is narrowing. In applications where the performance of a servo motor is not required, the stepper (with its choice of battery-less encoders and motor brakes) offers closed loop positioning performance and is particularly suited where high dynamic loads or speed demands aren’t required. These new devices are described as ‘extra-low’ voltage because they work at 24 or 48V DC offering open or closed loop positioning, they effectively bridge the gap between stepper and servo drives. Several new features distinguish this new generation of controllers from previous drives on the market to offer multiple benefits for users. Today, the humble stepper can offer surprising cost effectiveness with uncompromised performance at Automation lines and machinery are an amazing feat of integration of components and sub-systems from a vast range of suppliers. They meet ever increasing demands for lower cost, higher performance, sustainability and provide the capability of being incorporated within digital factories. Festo is making this task faster, easier and cheaper by focusing on Performance, Seamless Automation, Digitalisation and Sustainability. Ben Lloyd, Festo Electric Automation Product Manager looks at the latest developments. Highlighting the benefits with the CMMT-ST extra low voltage servo drive extra low voltage. The CMMT-ST servo drive maybe the smallest of the Festo electric drives range at just 27mm wide and only needing a 24 or 48V DC power supply, but it epitomises the approach of increased performance, seamless automation, sustainability and digitalisation. Higher performance Significant performance improvements have been achieved because the new servo drives are equipped with a microcontroller, which is three times more powerful than previous models. This delivers a number of performance enhancements, including: multi-protocol fieldbus compatibility, field weakening, energy management, auto-tuning, and U/f open loop control. Field weakening enables the connected motors to achieve higher maximum speeds or torques. For example, at low torques the maximum speed increases from 1,600 to 2,300 rpm – an increase of 44%. This presents the opportunity to select a smaller, lower cost motor to perform the same task. The CMMT-ST also features an integrated web server, an advanced feature for a low-cost device. This enables the easy transfer of data to and from the servo drive for fast, simple set-up, diagnostics, and file transfers. In addition, safety functions such as Safe Torque Off and Safe Stop 1 are also catered for. Seamless Automation Seamless Automation means that throughout the machine life cycle the CMMT-ST is easier, faster and cheaper to use. In the design phase simple software tools enable it to be quickly and easily selected, designed and documented. Festo online selection and configuration tools, such as the Electric Motion Sizing Tool, mean that specifiers can select the right drive package quickly and reliably. Faster and easier commissioning is also possible using Festo’s Automation Suite (FAS) software. In build, the drives connect seamlessly from set-up to commissioning – to the controls and software world ‘above’ and has a perfectly matched range of motors, mechanics and sensors ‘below’. The CMMT-ST range incorporates (just like its larger family members) multi-protocol connectivity. The new servo drives have the integral capability to communicate instantly to more than 75% of major fieldbus systems (including PROFINET, EtherCAT, EtherNet IP, and Modbus), either through simple DIP switch settings, software setup, or auto-recognition.
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