In the current technological environment where there are increasing demands for higher energy efficiency and lower costs, most manufacturers do not rely only on machinery and automation to decrease cycle times. Instead, they now pursue technology with solutions that are easy to set up, providing simple operator interfaces and reduced downtime. The choice of an electric, hydraulic or pneumatic motion system has the potential to affect costs, performance, flexibility, reliability, ease of use and maintenance. It is therefore important that customers get appropriate advice before selecting one of these, or opting for a hybrid automation solution.
The automation sector has already embraced the new reality of Industry 4.0 – the fourth industrial revolution. Industry 4.0 aims to increase the integration of all areas of industry through information technology. This has huge potential for increased collaboration, faster communication and real-time data exchange. For those with the foresight and expertise to integrate Industry 4.0’s offerings quickly, exciting opportunities are on the cards. There are six design principles that support companies in identifying and implementing Industry 4.0 scenarios: interoperability, virtualisation, decentralisation, real-time capability, service orientation and modularity.
Engineering companies that embrace combination electric, hydraulic and pneumatic motion technologies are in a better position to give the most suitable advice. They can help customers achieve the best solution for performance and price. They should have strong product portfolios in all three disciplines, and significant expertise in integrating electric, hydraulic and pneumatic technologies into an overall solution.
Hydraulics
Hydraulics is the choice for heavy loads when immediate motion is required. Hydraulics allows full velocity to be achieved quickly. Forces are by far the highest of the three technologies – upwards of 100 tons. Hydraulic systems have become smart – they are inherently powerful, and combine hydraulic actuators with integrated digital control electronics. This combination allows functions to shift to the software. The hydraulic standard functions are predefined in Bosch Rexroth controls, drives and power units – all the user needs to do is define the parameters.
Bosch Rexroth software and intelligent control algorithms, developed specifically for hydraulics requirements, automatically equalise the non-linearities inherent in fluid technology. For example, in the Sytronix series, the software combines the best from both electrical and hydraulic systems. Essentially, operations which used to be performed by valve controls made of steel and iron are now handled by decentralised intelligence in the electronically controlled device.
Bosch Rexroth integrated all of its electrohydraulics expertise in the IndraMotion MLC control solution software. This allows for the special characteristics inherent in fluid technology and can, in most instances, replace elaborate programming with parameterisation. This reduces engineering expenditure for machinery manufacturers and, depending on performance requirements, can execute both electrical and hydraulic movements without major changes in the machine control.
Pneumatics
Commonly powered by compressed air or compressed inert gases, pneumatics finds wide application in machining applications by offering fine performance and simple application. Most pneumatic systems operate at pressures of about 7 bar or less. Because pneumatic pressures are lower, components can be made of thinner and lighter weight materials. Factory automation is the largest sector for pneumatics technology, which is widely used for manipulating products in manufacturing, processing and packaging operations.
Pneumatics is the choice because speed and force are easily and continuously controllable over a wide range. This technology is also functionally reliable under adverse operating conditions and is insensitive to external influences such as high and low temperatures, dirt, mechanical vibration, moisture and electrical noise. In addition, pneumatics is fundamentally safe.
Aventics has integrated electronics into its current pneumatic range, for example the ED series electro-pneumatic pressure regulators or AES modular electronics for the AV Advanced Valve generation. This product range provides the functions required for machine networking and the Internet of Things, making its pneumatic components ‘Industry 4.0 ready’.
Aventics AV valves represent a valve technology innovation that is pushing the boundaries of electric/pneumatic hybrid products in terms of space and energy efficiency. With their diagonal arrangement of the valve spool, the valve size is reduced by half. This means these valves can be placed on machines close to the action, and reduces compressed air consumption by up to 20%.
Electric control
Electric control excels when absolute accuracy of movement is required or when continuous motion is needed. Electric servo control is useful in such diverse applications as CNC spindle controls in machining centres and lift-and-locate applications in assembly operations.
Electronic servo control offers the highest levels of precision, particularly in closed-loop applications where feedback allows the system to adjust to conditions. For example, Bosch Rexroth offers the System 300 advanced DC tightening system, which allows for multi-stage programming and multiple synchronisation of the spindle motors.
Since hydraulic and pneumatic applications use cylinders, they achieve linear motion simply and easily. Electric control is based on rotating motion and requires a transition, such as a ball screw or linear motor.
Electro-mechanical actuation can offer improved energy consumption. An experimental analysis conducted by the University of Kassel in Germany incorporating hydraulic, pneumatic and electric actuators, proved that the latter are the most energy efficient across the three disciplines.
In conducting the experiment, a specific duty cycle was chosen and parameters set for real application simulation. All actuators were mounted inline to have the same required duty cycle and the specifications for the choice of cylinders were similiar. The setup was conducted so that different loads could be chosen. A maximum load of 100 kg was chosen and standard hydraulic and pneumatic components used, with an integrated electromechanical actuator.
The measured energy consumption was multiplied by the number of operating hours and extrapolated to the real need during one year – with 6000 hours per year taken as a basis. The air cylinder’s energy requirement was 8980 kW hours per year, the hydraulic 3602 kW for the same period and the electro-mechanical alternative only 816 kW. CO2 consumption for the pneumatic system was 5,3 tons a year, 2,3 tons for hydraulic and only 525 kg for the electro-mechanical. This is equivalent to a saving of 90% compared to pneumatic and 77% to hydraulic cylinders.
Essentially, the comparison shows that a hydraulic actuator needs 4,4 times more energy for the same duty cycle and a pneumatic cylinder needs 10 times more energy compared to electromechanical actuators.
The electronics in Aventics AV valves in these applications support all standard fieldbuses and Ethernet protocols which realise control and communication tasks. The sensors also feature IO-Link interfaces, allowing them to exchange data with the control for diagnostic functions or parameterisation. For example, the Bosch Rexroth EMC electromechanical cylinder has an optional force sensor which allows decentralised process controls without a higher level control system.
The EMC-HD is a powerful alternative to pneumatic and hydraulic cylinders and provides benefits in terms of energy efficiency. It provides an advanced control technology advantage, even at high forces and its flexibility means it can be adapted to new tasks via the drive system. It is an electromechanical heavy-duty cylinder that transmits motor movement via ball or planetary screw drives, depending on the dynamics and force requirements.
Acquiring an appropriate hybrid solution
There are a number of factors to consider when selecting technology for a specific system, and key areas which should receive serious consideration are accuracy and repeatability, application complexity, speed, flexibility, reliability, maintainability and lifecycle costs.
The convergence of production IT and business IT, the synchronisation of processes as well as decisions taken autonomously by machines in real-time, have enabled the Hytec Group, through its relationship with Bosch Rexroth and Aventics, to provide accurate, efficient, customer-specific manufacturing products and solutions.
Industry 4.0 and the resultant hybrid automation solutions represent better resource allocation, higher efficiency, individuality and profitability. The Hytec Group is Industry 4.0 ready, with a number of safety-compliant hybrid solutions that integrate electric/pneumatics, electric/hydraulics and now even pneumatic/hydraulic/electric solutions.
For more information contact Willem Gijzelaar, Hytec Holdings, +27 (0)11 979 4630, [email protected], www.hytecgroup.co.za
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