Hydraulic Systems

Embedding axis controllers made by any manufacturer

Guest contributor: Theobald Herrmann, Bosch Rexroth

Automating hydraulic drives as easily and conveniently as electrical ones with combined monitoring and remote maintenance of all the technologies used – this increasingly important economic requirement can be fulfilled using valves with integrated axis controllers (IAC). What can they offer and how easy is it to implement manufacturer-independent integration at controller level?

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Bus systems play a key role in automation. They provide a flexible way of saving time and money when integrating hydraulic drives into higher-level control networks. However, in order to give the engineering plenty of freedom, this should ideally be independent of the controller manufacturer.

Ethernet – open communications standard

The basis for this manufacturer-independent communication is the network standard Ethernet. Thanks to the large address space and switch cascading facilities, networks can then be scaled to any size and can give an almost unlimited number of participants equal bus access. The most common Ethernet-based bus systems used in industrial automation to control hydraulic axes are SERCOSProfinet RTEthernet/IPEtherCAT, Powerlink and Varan.
All these bus systems can use multi-Ethernet interfaces to provide flexible availability – both for the engineering and for the end user.

What can IAC valves achieve with multi-Ethernet interfaces?

Multi-Ethernet interfaces are a key component of control valves with integrated digital axis controllers (IAC). The integrated switch (bus in and bus out)
makes it easy to comprehensively integrate your hydraulic drives into a uniform control concept. Using standardized M12 technology also enables you
to efficiently integrate a variety of sensors. The software-based control functions are particularly interesting to users. They enable the motion control
of a hydraulic drive to be handled in the same way as an electric one, ultimately depicting the operation and control of both types of drives in exactly the same way.

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Specific hydraulic axis control functions

Viewed precisely, an IAC (Integrated Axis Controller) is a digital controller equipped with control and regulation algorithms that is integrated into the valve together with all the necessary sensor interfaces for controlling position, pressure, force and flow. The extended function range includes alternating control (position, force) and status feedback for position control. This means that hydraulic motion sequences can be quickly implemented without the need for any programming. Another advantage is that control algorithms and parameters can be integrated into the valve and then selected by the higher-level controller as appropriate for the specific application. In this way, possibly supplemented by electric drives, they can be used as a cost-effective way of implementing tailored machine concepts and individual application requirements.

Commissioning, monitoring and engineering

Using standardized M12 technology reduces the cabling effort required and permits faster commissioning. Additional time and cost are saved by the wizard integrated into the software that guides the user through the few steps needed before final commissioning and also calculates all the necessary control parameters. Important for the plant’s availability are monitoring functions which, among other things, detect tracking errors and monitor the limits of travel.
In addition to these, some manufacturers also provide software tools to help motion control system users with commissioning and parameterization, and diagnostic functions such as multi-channel oscilloscopes and data loggers, so that the number of interfaces can be kept as low as possible – making the system faster and easier to configure.

Integrated machine safety (safe stop)

For the engineering IAC valves facilitate a modular construction system that can flexibly enhance system concepts. And not least, these include internally implemented DGUV-certificated safety functions. This gives you an economical and future-proof way to lay the foundations for safe stop, for instance by shutting down a channel as specified in EN 13849-1, and thus fulfill the requirements of the Machinery Directive even for large-scale plants.

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Case study 1: High precision control tasks

The role that IAC valves play in the accuracy of machine tools is made very clear by the example of a new rotary transfer machine with 54 electrical and hydraulic CNC axes. For this new development the manufacturer not only made use of a powerful CNC system solution with real-time communication via SERCOS, but also incorporated a module in controller format with software that was already capable of taking into account all the special features of fluid technology and was thus able to separate the drive level from the control level. This enables the machine to be constructed more compactly and with lower heat input. Thanks to the stable temperature, the vibration-damped sleeves of the circular array of processing axes can achieve a repeatable precision in the hydraulic servo axes of less than +/- 1 μm, corresponding to 5 μm on the workpiece. The travel speed is up to 30m/min.

Case study 2: A retrofitted core shooting machine

In addition to new designs, IAC valves with multi-Ethernet interfaces also offer considerable potential when it comes to modernizing legacy machines. For example, the well thought-out retrofit of a 50 year old core shooter coupled with new hydraulic components resulted in significantly improved efficiency. A total of eight IAC valves regulate the hydraulic cylinders on the basis of the set positions given by a CNC controller. Their possibilities and high level of precise repeatability made it possible to reduce the figures for setup time (system changeover) and waste (nibs). Altogether, despite operating three shifts, the machine’s availability increased by more than 10%, corresponding to 500 hours. Using a secure logic controller meant that safety was also brought up to date.

Conclusion

IAC valves with multi-Ethernet interfaces and integrated axis controllers enable mechanical engineering companies to easily utilize the productivity potential offered by hydraulic and hybrid drives.

Combining them with engineering tools, including industry-specific and application-specific control structures makes it possible to cost-effectively
implement tailored machine concepts and modernizations, with the result that the manufactured results can be optimized faster and more easily.

More informationwww.boschrexroth.com/iac

Moviehttps://www.youtube.com/watch?v=fVBOYCP31P0

cropped-cmafh-logo-with-tagline-caps.pngCMA/Flodyne/Hydradyne is an authorized Bosch Rexroth distributor in Illinois, Wisconsin, Iowa and Northern Indiana.

In addition to distribution, we design and fabricate complete engineered systems, including hydraulic power units, electrical control panels, pneumatic panels & aluminum framing. Our advanced components and system solutions are found in a wide variety of industrial applications such as wind energy, solar energy, process control and more.

New hydraulic design for presses

Guest contributor: Stefan Zimmerman

New drive concept makes hydraulics economical and intelligent

By means of variable-speed pump drives, new, patented hydraulic axes simplify the design and control of presses of any kind. They considerably reduce the power consumption as well as the required oil quantity by up to 90 percent. To this extent, the control technology of a valve control moved into the software of intelligent servo drives of a displacer control. This reduces the complexity and opens up new levels of flexibility and of condition monitoring.

Worldwide, the climate change has increasingly drastic effects on the everyday life. Thus, governments and international organizations have defined climate targets in order to limit the CO2emissions. What has already become standard in light bulbs and household devices also takes increasingly more effect in the industry. Energy-efficiency has become a decisive criterion for the machine users when it comes to the selection of machinery and systems. They expect a considerably increased output with clearly reduced current and resource consumption. Apart from that, numerous companies have already publicly obliged themselves to reduce their CO2 emissions by defined quantities. They can only achieve these targets if new machinery and systems are considerably more energy-efficient. So it is the challenge of machine manufacturers to develop new concepts.

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Using the hydraulic force density as required

In large systems with very high processing forces as they are required for forming methods, the hydraulics as main drive is one of the largest power consumers. The end users have accepted this for a long time as they wanted to have the maximum force available at any time, even if the process did not permanently require it. Modern hydraulic drives distinguish themselves by the physical unique selling points such as power density and robustness; however, they clearly reduce the power consumption by controlling the displacer as required. Thanks to its hybrid concept, the new hydraulicAxis patented by Bosch Rexroth for presses of different kinds, from low to high drive power, connects the advantages of hydraulics with those of the electric drive technology. First equipment according the new concept has shown that the power consumption can be reduced by more than 30 percent. The required oil quantity of the hydraulic installation can be reduced by up to 90 percent.

Conventional hydraulic systems

For decades, conventional systems have proven of value for presses in the medium and high performance range as drive technology of choice. In this connection, these systems mostly work with a central hydraulic power unit with several variable displacement pumps.  Moreover they are operated by electric motors directly connected to the mains. Apart from that, central or decentralized manifolds with on/off and proportional servo valve technology are required in order to control the cylinder(s) in rapid traverse, working or pressing mode and in the so-called return.

One disadvantage of this concept are idling losses during the standstill times. In the control of the cylinders, there are also throttle losses caused by the valve control. There is partly considerable heat introduction into the hydraulic oil, which must afterwards be compensated again by corresponding cooling.

Hydraulic axis replaces central power unit

A new, patented hydraulic concept replaces the previously common central power unit with valve control by a patented hydraulic axis with speed-controlled displacer control and a closed, decentralized fluid circuit. The hydraulic axis consists of a differential cylinder with a cylinder chamber and ring chamber. The cylinder chamber is for a powerful working movement and the ring chamber for the fast rapid traverse movement. An auxiliary cylinder takes up the oscillating volume during the different movements and in this way creates a closed circuit. A central oil tank is no longer necessary and thus completely omitted.

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The flow is generated by variable-speed pump drives. In order to satisfy the high precision and dynamics requirements, servomotors in combination with adjustable axial piston pumps lend themselves. Thus, all options of the 4-quadrant operation are available to the design engineers. With several cylinders, a corresponding number of Hydraulic axes is used. The synchronization control is performed by the software of the intelligent servo drives, synchronized by means of real-time communication.

Reversal of the movement by changing the direction of rotation

The area switchover for the relevant movement is effected by means of two valves. During the pressing process, the cylinder areas are large. Thus, the cylinders reach high forces at low velocity. During the return of the cylinders, however, the areas in the ring chamber are small in order to achieve the maximum rapid traverse velocity with low forces and to thus reduce the downtimes of the presses. For the reversal of the movement, the servomotors change their direction of rotation. If adjustable axial piston pumps are used, the swash plate of which can be swiveled through zero, the direction of the movement can also be changed by adjusting the swivel angle.

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Energy efficiency in practice: Presses consume more than 30 percent less

The hydraulic axis works in a strictly need-oriented manner. At partial load, the servo drive controllers reduce the speeds of the pump motors to the lowest value possible. During standstill times, e.g. for cooling down the tools, the motors are standing and do not consume any energy. During that time, safety valves support the return. Depending on the cycle times, variable-speed pump drives allow for energy savings of more than 80 percent as compared to constantly driven power units without variable displacement pumps. In practice, the first presses with hydraulic axes achieved reduced consumption of 30 percent as compared to already energetically optimized, conventional hydraulic solutions.

BR_Homburg_Booster-105Regarding the Sytronix family, Rexroth offers more than one hundred pump drives with variable speed relating to power and function. These can be integrated into all usual automation structures thanks to multi-Ethernet interfaces.

Exceeding the savings due to the need-based closed-loop speed control, additional functions increase the energy efficiency of the presses even further. In the lowering movement, the servomotors recuperate the braking energy and either feed it into an electric accumulator, make it available to other actuators, e.g. handling axes, via an intermediate circuit or feed it back into the mains.

Synchronization control of the hydraulic cylinders via intelligent software

The synchronization control can be effected via all common real-time protocols such as PROFINET, Ethernet IP, EtherCat or Sercos if the servo drive controllers provide corresponding multi-Ethernet interfaces. Changes in motion sequences are only transmitted via the machine control by means of software command to the intelligent drives. Mechanical adjustment works at the hydraulic axis are not necessary. So due to short changeover times, end users gain flexibility. At the same time, you can continuously document the manufacturing processes of every component by means of the servo-drive data. This satisfies the increasing demands on the traceability of products.

90 percent less hydraulic oil – central tank omitted

Due to the new concept of the hydraulic axis, the movements are primarily controlled via variable-speed pumps rather than the throttling of the flow by the valves. So considerably less heat is introduced into the hydraulic oil and only minor agitation results. Result: In the first presses with hydraulic axes, the manufacturer could reduce the oil volume from e.g. 10,000 liters to only 900 liters. This saves space for the tank and reduces the operating costs as in an oil exchange, less than ten percent of the previously used oil quantity have to be purchased and disposed of.

An additional advantage is the clearly reduced average noise emission. With variable-speed pump drives, it is up to 20 db(A) below that of constantly driven pumps. During standstill, the noise level of the hydraulics falls to zero. Due to the omitted tank and complex piping for a power distribution, resonance bodies for the structure-borne sound are omitted. With the new concept, the expenses for the noise insulation are considerably lower.

Easier hydraulic construction with quick commissioning

For manufacturers of hydraulic presses, the conversion to hydraulic axes brings about considerable savings in the design, assembly and commissioning. Tank, cooling and piping are completely or largely omitted as is the valve technology. The variance of different motion sequences is moved from the valve technology into the drive controller software. Here, Bosch Rexroth has, for example, integrated best-in-class controllers for different force/path and synchronization controls. Due to the corresponding commissioning software, the engineers don’t even need in-depth hydraulic knowledge for the initial commissioning. Software wizards propose suitable parameters. This considerably shortens the commissioning phases of a hydraulic press.

Condition monitoring increases the availability

The data that is gathered by the intelligent servo drives anyway and that can be amended by more sensors is particularly interesting for end users. It forms the basis for condition monitoring strategies increasing the availability. Based on the analysis of the data, the corresponding software identifies wear and errors before they will lead to standstills. So machine downtimes are replaced by scheduled maintenance measures.

Find out more about self-contained hydraulic actuators here.

cropped-cmafh-logo-with-tagline-caps.pngCMA/Flodyne/Hydradyne is an authorized Bosch Rexroth distributor in Illinois, Wisconsin, Iowa and Northern Indiana.

In addition to distribution, we design and fabricate complete engineered systems, including hydraulic power units, electrical control panels, pneumatic panels & aluminum framing. Our advanced components and system solutions are found in a wide variety of industrial applications such as wind energy, solar energy, process control and more.

Hydraulics with IO-Link: Reduced effort, high value

Guest contributor: Theobald Herrmann, Bosch Rexroth

In almost all industries, machine users require increased flexibility for production means for small batches and continuous diagnostics of all actuators and sensors to increase availability. In addition to this, there is quickly increasing horizontal and vertical connection of machinery and systems for Industry 4.0 applications. The open standard IEC 61131-9, IO-Link, fulfills these requirements at low connection costs and energy consumption. Flexibility of hydraulics is increased by transmission of parameter changes in running operation. Provision of diagnostics information offers numerous opportunities to extend the concepts of predictive maintenance to increase availability of the systems. The manufacturer-independent IO-Link can be integrated easily and quickly in any industrial automation application.

Standardized wiring and electronic name plate support commissioning and increase availability

• Open standard for bi-directional point-to-point connections in parallel to field bus
• Easy connection with standard cables and M12 connectors
• No additional engineering tool necessary, possible configuration via control system.
• Data for predictive maintenance and quick device replacement
 Industry 4.0-compatible hydraulic components for vertical flow of information

Introduction: Limits of serial field bus communication

The introduction of field bus technology in the 1980s was the starting point for horizontal connection of decentralized actuators within machinery. Serial wiring lead to a considerable reduction in cabling and opened new possibilities for modularization in mechanical engineering. Field buses as well as most current real-time Ethernet protocols are manufacturer-specific, proprietary systems. The protocols have been developed by control system manufacturers and focus on communication between own electric control systems and selected peripherals. For actuators, sensors and other third-party equipment, either their manufacturers or system integrators are required to provide suitable interfaces in hardware and software for the respective field bus. This is very complex as device profiles and software have to be created in the respective PLC for every individual field bus and control system of each manufacturer.

Possibilities for hydraulic connection

Integration of hydraulics in modern automation systems can be realized in different ways. Numerous existing machine concepts apply on-board electronics for control of hydraulic valves. Exchange of digital information is restricted and only possible if the respective device is connected to a superior control system via individual wiring. This state-of-the-art in technology increasingly no longer meets the requirements of end users.

The alternative are valves with integrated field bus connection. These, however, require extensive wiring as well as integration into the control system and the respective field bus protocol by means of dedicated software. Both requires considerable effort that is too high particularly for price-sensitive applications.

Thanks to IO-Link, machine manufacturer and system integrators are enabled to integrate for example proportional hydraulic series valves and sensors into digital communication structures with very little engineering effort. With its simple communication structure, IO-Link has low hardware requirements. Additionally, the standardized M12 connection technology enables simple and cost-efficient connection of hydraulic valves in the field. This way, previously “deaf-mute” components with analog control are transformed in communicating and flexible actuators and sensors.

IO-Link: Manufacturer-independent and compatible with all field bus protocols

The manufacturer-independent IO-Link according to IEC 61131-9 standardizes connection technology for actuators, sensors and other equipment and provides a digital communication protocol for data exchange between control systems and devices regardless of the field bus. Field bus technology is not replaced but extended. Parallel communication enables machine manufacturers use of IO-Link with all protocols and integration of IO-Link-compatible devices into various concepts without additional effort.

IO-Link is currently already supported by around 130 device manufacturers and companies in the field of technology. Around 40 manufacturers offer IO-Link Masters and the standard is supported by nine manufacturers of control systems with central Masters and respective engineering tools. IO-Link devices are in the product range of almost sixty manufacturers of sensors, actuators and other peripherals. Rexroth, for example, now also offers hydraulic proportional valves and pressure sensors with respective technology. Function and performance of these proportional valves are identical to series valves. However, they also offer all options for bi-directional communication via IO-Link. This way, the hydraulics can be integrated seamlessly into connected structures. Parameters can be changed and operating states changed by the control system during running operation.

IO-Link system set-up

A full IO-Link system consists of one centralized or decentralized IO-Link Master, one or more IO-Link devices as well as unshielded 3 or 5-conductor standard cables with M12 connectors. Project planning and parameterization of the IO-Link Master can be realized in the control system hardware or an optional engineering tool. The point-to-point connections between IO devices and the automation system are established by the Master. It serves as the interface to the superior control system.

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IO-Link Masters are offered by around 50 manufacturers for connection of one IO device per port. The selection includes options for the IP20 control cabinet as well as decentralized modules with protection class IP65/67 for installation at machinery. Particularly in large-scale systems, cabling is considerably reduced.

For decentralized IO-Link Masters, the user organization of IO-Link has defined M12 plug-in connectors with three or five conductors. The 5-pole version “Class B” port is used for devices with increased current consumption like hydraulic valves. The 3-pole version “Class A” port provides an energy supply of up to 200 mA which is sufficient for most sensors. In contrast to analog controls, unshielded cables are sufficient for fault-free communication over a cable length of up to 20 meters. IO-Link standardizes connection technology for all actuators and sensors and eliminates numerous sources of errors during the installation of systems. Otherwise complicated and expensive cable dimensioning with individual wiring and shielding is no longer required. In addition, the logistic effort is reduced thanks to application of uniform M12 cables for sensors and actuators.

Rapid commissioning per software

Every IO-Link device features an electronic device description, referred to as IO Device Description (IODD). It provides standardized important information:

• Device data
• Text description
• Identification, process and diagnosis data
• Communication properties
• Device parameters with value range and default value.
• Image of the device
• Logo of the manufacturer

The IODD set-up is identical for all devices of all manufacturers. The IODD enables automatic recognition of the device by the IO-Link Master for immediate parameterization. Also automatically, device descriptions are included in the system documentation.

For project integration of the IO-Link Master in overall automation, commissioning personnel use the engineering tools of the respective PLC manufacturer. The IO-Link Master is selected from the device portfolio and added to overall automation. Depending on the control system manufacturer, all blocks for communication are available in a library for free.

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Via IO-Link to Industry 4.0

IO-Link enables access to device data either directly from the control system or remotely via networks from any location. Particularly important for future-oriented concepts: Already today, IO-Link offers type and instance data of Industry 4.0 devices according to the definition of the German “Plattform Industrie 4.0” initiative.

This way, also hydraulic actuators meet all conditions for future requirements of Industry 4.0 applications. Additionally, this approach is well-suited for subsequent connection of existing machinery and systems with low effort. Users replace installed proportional valves and sensors by interchangeable options with IO-Link connection for direct communication with actuators and sensors.

Diagnosis functions for increased availability

The diagnosis functions of IO-Link devices enable new maintenance concepts and considerably reduce repair times. Now possible call-up of device information in parallel to the process forms the basis for condition-oriented and predictive maintenance concepts. In this respect, proportional valves report whether they are functional as well as errors like under or overvoltage. In addition, the valve and sensor status is displayed for transparent error analysis. An integrated operating hour indicator enables calculation of the residual life-cycle for maintenance and decision-making on further use of the valve.

In case of faults, IO-Link accelerates diagnosis thanks to remote access for maintenance specialists to identify the type and location of any errors. Precise localization without personal presence at the system alone considerably reduces reaction times. If necessary, the maintenance technician opens the IODD file of the respective device in the control system. Other than before, components do not need to be disassembled to decipher hardly readable labels and manufacturers and types no longer need to be looked for in system documentations. Thanks to the electronic name plate, all this information can now be accessed with just one mouse click to initiate the respective order without delay.

IO-Link follows the plug & play principle. Replaced devices are recognized by the IO-Link Master according to their IODD file and the respective parameters are automatically transferred without any actions in the software. This way, even less experienced technicians are enabled to replace components without problems to considerably reduce system downtimes.

Summary

The open IO-Link standard establishes continuous communication with sensors and actuators irrespective of the used field bus. Now, even hydraulic proportional valves can be intelligently, easily and cost-effectively integrated in bi-directional digital communication. This simplifies commissioning in hardware and software and enables flexible adjustment of hydraulic valves for varying production processes. Increased requirements for flexible machinery and systems are now complied with. Extended diagnosis information enables condition-oriented and predictive maintenance concepts and standstill and maintenance times are reduced. This increases the availability of machinery. In addition, IO-Link enables future-proof integration of hydraulic valves into connected structures as Industry 4.0 components with all their related features.

Why hydraulics and IO-Link? Click here

Learn more about Rexroth and IO-Link

cropped-cmafh-logo-with-tagline-caps.pngCMA/Flodyne/Hydradyne is an authorized Bosch Rexroth distributor in Illinois, Wisconsin, Iowa and Northern Indiana.

In addition to distribution, we design and fabricate complete engineered systems, including hydraulic power units, electrical control panels, pneumatic panels & aluminum framing. Our advanced components and system solutions are found in a wide variety of industrial applications such as wind energy, solar energy, process control and more.

 

Pump control – simple or intelligent?

Guest contributor: Martin Endres, Bosch Rexroth

Control pumps have a fixed place in hydraulics. Your advantage: They only provide as much flow and/or power as is required for the specified movement task. But which pump control  is suitable for which application? Mechanical-hydraulic or electro-hydraulic pump control? What are the differences?

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The advantages and disadvantages of the two pump control types can well be explained using the flow control of a deep drawing press as example. The hydraulic drive of the cylinder is based on a variable displacement pump working in an open circuit. The displacement is 250 cm3, the nominal pressure 350 bar. The mechanical input signal is hydraulically amplified. In this connection, the pump has three typical control tasks: Flow control (N and/or S function), power control (LR function) and pressure control (G function).

01) Mechanical-hydraulic pump control: simple, however limited

The mechanical input signal from the hand lever is hydraulically amplified. In this case, the flow is controlled by means of load-sensing. The pump swivel angle is adjusted independently of the load occurring at the actuator by means of a load sensing valve which is set to a Δp of 20 bar. So the velocity at the actuator remains constant.

The disadvantage: The throttling of the flow at the pump output goes along with a power loss which is completely converted into heat and increases the cooling demand. One advantage, however, is the easy set-up which does not even require a pilot oil pump as the adjustment energy is taken from the high pressure. Due to the continuous Δp of 20 bar, flow control is also possible at low pressures.

Power controllers increase the complexity

There is a need for an additional pilot oil pump if the deep drawing press – for example for safety-related reasons – requires a flow of zero in case of a low counter pressure (maximum of 4 bar). More components are necessary for realizing the power controller.

02) Electro-hydraulic pump control

Data recording and comparison by control electronics Compared to that, an electro-hydraulic system with only one fast high-response valve at the pump and amending control electronics is the more elegant solution. The regulated variables (path, force and velocity) correspond to the analog hydraulic variables flow and pressure.

The principle: A swivel angle sensor on the actuating piston and a separate and/or attached pressure transducer record the actual flow and pressure values. After comparison to the specified command values, the control performs all flow, pressure and torque limitation tasks and forwards a command value to the valve. Figure 2 shows different pump control systems which are autarkic subsystems and connected to the machine control via corresponding
interfaces.

Today, there is a whole range of motion controls and NC controls for hydraulic actuators available. It comprises single-axis controllers without control
cabinets where the electronic controls are integrated completely in the valve, up to multiple axis controllers with control cabinets for more complex tasks. In addition, intelligent pump controllers are improving the system performance. These control systems communicate via established field buses or Ethernet protocols with superior systems, and with these open standards it is possible to completely integrate them into Industry 4.0 architectures – this way, intelligent, networkable hydraulics are completely Industry 4.0 ready.

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03) Decision-making aid: Selection of the pump control type

It first of all depends on the physical variable to be controlled whether the mechanical-hydraulic or the electro-hydraulic variant is finally the better choice for the relevant application. Flow and pressure can be controlled with both types. For limiting the torque, however, the mechanical-hydraulic method needs an additional power controller changing the flow with constant pressure and simultaneously increasing the complexity of the hydraulics. Here you can find the selction guide

Master-slave pump combinations

A master-slave pump combination interesting for many applications is only feasible with an electrohydraulic control; however, it allows for combined pump systems with special properties. If, for example, by an early swiveling out of the pump, the master pump provides a certain flow from a certain point in time, it can be positioned at the maximum swivel angle already upon start-up of the motor and deliver into the system, which again increases the velocity and precision of the application.

How dynamic and accurate should the pump be?

The required dynamics and precision are more decision-making criteria. If, for example, particularly high dynamics with up to 80 ms are required, a primarily controlled pump would be suitable. With regard to precision, electro-hydraulic control systems with a repetition accuracy of <= 0.2 % for the pressure and a linearity deviation for the swivel angle of <= 1 % show convincing results. Compared to that, mechanical-hydraulic controls achieve about +/- 1.5% repetition accuracy for the pressure and a linearity tolerance of 2.5 to 7 % of Vgmax. All values are valid for a constant operating temperature of 50°.

Conclusion

The strength of the mechanical-hydraulic pump control is its simplicity. It is, however, only convincing in correspondingly clear applications. With increasing requirements with regard to function, precision and energy efficiency, there is no alternative to electro-hydraulic control systems which allow for pressure and flow control with high control quality according to the demand. As digital control electronics with integrated Multi-Ethernet interface can moreover be integrated into most different structures, it moreover also masters the prerequisites for the increasingly demanded networking in the sense of Industry 4.0.PC 4 Tabellen_EN-1-927x1200.png

Info graphics: Decision-making aid for the selection of the pump control type.

Learn  more about an electro-hydraulic pump control: www.boschrexroth.com/hpc

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CMA/Flodyne/Hydradyne is an authorized Bosch Rexroth distributor in Illinois, Wisconsin, Iowa and Northern Indiana.

In addition to distribution, we design and fabricate complete engineered systems, including hydraulic power units, electrical control panels, pneumatic panels & aluminum framing. Our advanced components and system solutions are found in a wide variety of industrial applications such as wind energy, solar energy, process control and more.

 

New Design for Hydraulic Power Units

Guest contributor:  Andreas Günder, Bosch Rexoth

Optimum power, less installation space: Thanks to new intellectual and design approaches, compact hydraulic power units increase the economic efficiency of machine tools.

Powerful force in a very confined space

In the production world, hydraulics are firmly established. Machine tool manufacturers appreciate hydraulics for their high power density, toughness and modular design. In the lower performance range up to 4 kW, however, there are also some challenges. Since the installation space is often limited, designers and technical purchasers are constantly looking for increasingly compact solutions.

Installation space is valuable

The demand for compact hydraulic drives is not only due to the structurally limited flexibility regarding extensions, modernization measures and refittings but also due to the requirements regarding acquisition costs and assembly times or structural extensions of the working space with given machine dimensions. In addition to the level of integration of the functions, energy efficiency often plays an important role as well. Last but not least, many manufacturers are following the miniaturization trend. If workpieces become increasingly smaller, the moved mass of the machine tool has to be decreased accordingly.

“Installation space eaters” hydraulic power units

To reduce the installation space, solution manufacturers can start mainly with the following components: hydraulic power unit and control cabinet. When considering this split, it becomes evident that compact power units which are also easy to integrate require completely new design approaches to eliminate all features which waste unnecessary space in the performance spectrum up to 4 kW and to ensure that the units are still compatible with many different machine designs.

Highly integrated design approaches

The features of such innovative design concepts according to the EU Eco-Design Directive 2009/125/EC for example include a tank which is optimized for efficient degassing and reduces the oil volume by up to 80 percent. A much more decisive factor for gaining space is, however, that all functions can actually be integrated in one small power unit – from an economic variable-speed drive for demand-based power output to sensor technology with filling level, temperature, pressure and filter contamination sensors to a completely wired frequency converter.

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Compact and ready for Industry 4.0

For the future viability of this approach with regard to Industry 4.0, a data interface is essential as well. Only with permanent condition monitoring can the operating conditions be optimized comfortably and relevant faults be detected early on. With this equipment, the user only has to connect the electric power, the data interface and the hydraulic supply during installation and the hydraulic power unit is ready for operation

New cooling with heatpipe

So-called heatpipes are considered to be a space-saving innovation regarding the cooling of hydraulic power units. Their high-performance passive thermal conduction allows for a further reduction of the frame size. The heatpipes absorb the thermal energy of frequency converter, motor and hydraulic oil and efficiently transfer it to a central heat sink such as e. g. cooling water…
This ensures an intelligently optimized thermal management within the hydraulic power unit and optimally utilizes the cooling power of the cooling water. There is no need for a separate hydraulic circuit for oil cooling. This reduces installation space, noise emissions, energy consumption and possibilities for leakage.

Heatpipe – Functional principle

Basically, a heatpipe consists of air-tightly sealed copper pipes with underpressure. Inside, there is a medium which transfers thermal energy. In the temperature range of hydraulic power units, the medium may be e.g. distilled water. The boiling temperature of the water is significantly reduced by the low pressure within the heatpipe, which means that a boiling or condensation process can already take place at low temperatures.

Functionality: If you dip the heatpipe for example in hot hydraulic oil, the thermal energy at the lower immersed part of the heatpipe is transferred to the water. The water exceeds the boiling point, evaporates and absorbs a large amount of thermal energy with low temperature difference (latent heat). The water steam rises to the upper part of the heat pipe which is cooled by e. g. a cooling element. Here, the water steam condensates and gives off the thermal energy to the cooling water. Thanks to the latent heatabsorption and dissipation, the thermal conductivity of heatpipes can be up to 1000 times higher than the thermal conductivity of copper pipes. Due to the high elasticity of the copper pipes, the heat pipe can be easily shaped. In this way, ideal heat paths can be formed inside the hydraulic power unit and the installation space can be considerably optimized. Similar application ranges with equal optimization potential can be found in computer technology. Here, the thermal energy in laptops caused by heat sources such as the CPU are transferred to the central cooling elements using heatpipes.

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Plug & Play: no control cabinet

The frequency converter has a high potential for gaining installation space as well. If it has already been equipped with Multi-Ethernet interface for Sercos, Profinet and other standards by the manufacturer, machine and plant manufacturers are able to reduce the control cabinet requirement for the hydraulic unit by up to 100 percent. As a precondition, however, the sensor technology and the motor in the power unit have to be wired to the frequency converter in such a way that the frequency converter can control the hydraulic pressure autonomously. This means that the control cabinet can not only be designed with smaller dimensions. Sometimes it can even be completely omitted together with the corresponding installation effort and related sources of error.

Conclusion

Fully integrated small power units based on a completely innovative design approach for the performance range up to 4 kW provide machine and plant manufacturers with the advantages of hydraulic drives with very little space requirements. As an alternative to purely electrical solutions, the required energy can be converted into a linear movement in a precise and costeffective manner directly at the working area using a simple hydraulic cylinder. If sensor technology, frequency converter and data interface are integrated as well, users not only benefit from comprehensive condition monitoring but also from a significantly reduced control cabinet footprint or even from a design without control cabinet.
More information fully integrated power units: www.boschrexroth.com/cytropac

Operating principle: https://www.youtube.com/watch?v=sSPemS94G2I

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CMA/Flodyne/Hydradyne is an authorized Bosch Rexroth distributor in Illinois, Wisconsin, Iowa and Northern Indiana.

In addition to distribution, we design and fabricate complete engineered systems, including hydraulic power units, electrical control panels, pneumatic panels & aluminum framing. Our advanced components and system solutions are found in a wide variety of industrial applications such as wind energy, solar energy, process control and more.

Twelve tips for better cylinder selection

Guest contributor: Marty Hegyi Product Manager, Cylinders, Bosch Rexroth Corp.

Here’s how to design hydraulic cylinders that improve performance, last longer and cost less.

Hydraulic cylinders harness fluid pressure and flow to generate linear motion and force, and they work well in both industrial machines, like presses and plastic-molding machines, and in mobile equipment, like excavators and mining trucks. And when compared with pneumatic, mechanical or electric linear-motion systems, hydraulics can be simpler, more durable and offer significantly greater power density.

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Bosch Rexroth builds large hydraulic cylinders with bores to 1.5m and strokes to 24 m

Hydraulic cylinders are available in an impressive array of types and sizes to meet a wide range of application needs. Choosing the right cylinder is critical for maximum performance and reliability. Here are 12 practical tips for selecting, sizing and operating the best one for a job.

Selection considerations

1. Choose the right cylinder type. Two basic hydraulic cylinder designs for industrial applications are tie-rod and welded cylinders.

Tie-rod cylinders use high-strength threaded steel tie rods on the outside of the cylinder housing for additional strength and stability. In the U.S., this is the most common cylinder type. They’re used on most general industrial applications, such as plastics machinery and machine tools, although they tend to be limited to 3,000 psi maximum operating pressure. The cylinders are built to NFPA standards, which makes their dimensions and pressure ratings interchangeable with any other cylinder built to that standard.

Welded or mill-type cylinders have a heavy-duty housing with a barrel welded or bolted directly to the end caps and require no tie rods. Designed for higher pressures, to 5,000 psi

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Mill-type cylinders have a heavy-duty housing with a barrel welded or bolted directly to the end caps

Mill -type cylinders have a heavy-duty housing with a barrel welded or bolted directly to the end caps and require no tie-rods

or greater, they are generally preferred in more-rugged applications such as presses, steel mills and offshore settings with harsh environments and wide temperature swings.

Unlike U.S. OEMs, European manufacturers typically use mill-type cylinders in almost all general industrial applications. (They also use tie-rod cylinders, but generally for lower-pressure tasks up to 160 bar (2,350 psi).) However, due to the design, tie-rod cylinders are less expensive than mill-type cylinders—another reason for widespread use in the U.S.

Also keep in mind that cylinders are often customized. NFPA cylinder standards dictate dimensions, pressure ratings, type of mountings, and so on—they’re standard catalog products. However, engineers designing custom machinery often need to deviate from the standards with special mountings, port sizes or configurations to suit a particular application. About 60% of the cylinders sold in the U.S. are catalog items, while 40% are modified products with unique requirements.

2. Select the proper mountings. Mounting methods also play an important role in cylinder performance. The cylinder mounting method first depends on whether the cylinder body is stationary or pivots.

For stationary cylinders, fixed mounts on the centerline of the cylinder are usually best for straight-line force transfer and minimal wear. Among the different variations, flange mounts are generally preferred. Loads are centered on the cylinder and opposing forces are equally balanced on rectangular or round flanges. They’re strong and rigid, but have little tolerance for misalignment. Experts recommend cap-end mounts for thrust loads and rod-end mounts for pull loads.

Centerline lug mounts also absorb force on the centerline, but require dowel pins to secure the lugs to prevent movement at higher pressures or under shock conditions.

Side-mounted or foot-mounted cylinders are relatively easy to install and service, but

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Tie-rod cylinders have high-strength threaded steel tie rods on the outside of the cylinder  housing for added strength and stability

they generate offset loads. The mounts experience a bending moment as the cylinder applies force to a load, potentially increasing wear and tear. Heavy loading tends to make long-stroke, small-bore cylinders unstable.

Side and foot mounts need to be well aligned and on the same plane, and the load supported and guided. Otherwise, induced side loads due to misalignment lead to cylinder wear and seal leaks. Engineers also must be concerned with shear forces on the bolts. Add a dowel or shear pin and keyway behind the feet to prevent the forces from potentially shearing the mounting bolts. If necessary for extra support, add another set of foot mounts in the cylinder midsection in addition to those on the head and cap ends.

3. Select the right pivot mountings when the cylinder body moves. Pivot mounts absorb force on the cylinder centerline and let a cylinder change alignment in one plane. Common types include clevis, trunnion and spherical-bearing mounts.

Clevis mounts can be used in any orientation and are generally recommended for short strokes and small to medium-bore cylinders. Cylinder engineers prefer clevis mounts with spherical bearings over those with plain bearings because they allow for a bit more misalignment and are, thus, a bit more forgiving. However, if using a spherical bearing on a rear clevis, they also recommend a rod-end attachment that pivots—such as a spherical rod eye. The combination helps compensate for any side loading or potential misalignment.

Trunnion mounts come in head, mid and rear-mount versions. The mid-trunnion design is likely most common, as it offers designers a bit more flexibility. They can be specified exactly in the cylinder mid-section or most anywhere toward the front or rear as the application demands. Once specified, however, the mount is not adjustable.

Sizing considerations

For all types of cylinders, important parameters include stroke, bore diameter, rod diameter and pressure rating.

4. Piston-rod diameter is critical. Perhaps the most common error in hydraulic design is underspecifying the piston rod, making a cylinder more prone to stress, wear and failure. Piston-rod diameters can range from 0.5 to more than 20 in., but they must be sized for the available loads. In a push application, it is extremely important to size the rod diameter properly, based on Euler calculations, to avoid rod buckling or bending.

When designing a cylinder to generate a required force, sizing the rod is always the first consideration. From there, work backward and determine bore size for the available pressure, and so on.

5. Prevent rod bending. In cylinders with long strokes, a fully extended rod can bend under its own weight. Excessive bending leads to wear and damage to seals and bearings. It could even cock the piston inside the bore, which can score and damage the inner surface of the cylinder. Rod deflection should never exceed 1 to 2 mm.

Cylinder rods that are at risk for bending or misalignment require additional support. Depending on the stroke length, a stop tube—which increases the bearing area of the cylinder—may be required to prevent excessive wear and jack-knifing. Engineers might also consider a larger diameter rod, which increases strength. But that also increases weight and may be self-defeating, so do the math carefully. In extreme cases, users may also need to add external mechanical support for the rod, such as a saddle-type bearing.

6. Watch out for impact loads. Stroke length, the distance needed to push or pull a load, can vary from less than an inch to several feet or more. But when the cylinder extends or retracts, ensure that the piston doesn’t bottom out and generate impact loads at the end of stroke. Engineers have several options: Add internal cushions to decelerate the load near the end of stroke; add an external mechanical stop that prevents the cylinder from bottoming out; or use proportional-valve technology to precisely meter flow and safely decelerate the load.

7. Weigh bore diameter versus operating pressure. To produce a given amount of force, engineers can specify large-bore cylinders that operate at low pressures, or vice versa. Generally, systems that operate at higher pressures but with smaller cylinders are more cost effective. Also the benefits cascade. Smaller cylinders require less flow and, in turn, smaller pumps, lines, valves and so on. Many installations see an overall cost reduction by moving to higher pressures.

That said, cylinders are rated for both nominal (standard) pressure and test pressure to account for variations. Systems should never exceed the nominal rated design pressure of a cylinder.

8. Add a factor of safety. While design calculations are essential, real-world operations differ from theoretical results. Always assume peak loads will require additional force. The rule of thumb is to choose a cylinder with a tonnage rating of 20% more than required for the load. That compensates for losses like friction from the load, efficiency losses in the hydraulics, actual pressure below the rated system pressure, slip-stick on cylinder seals and bearings, and so on.

Operating considerations

Cylinder parameters like stroke and force must match machine requirements, but that is only half the challenge. Environmental and operating demands also play a major part in determining a cylinder’s ultimate success.

9. Match the seals to the job.Seals are probably the most vulnerable aspect of a hydraulic system. Proper seals can reduce friction and wear and increase service life, while the wrong seal leads to downtime and maintenance headaches. It probably goes without saying, but ensure the seal material is compatible with the fluid. Most hydraulics use a form of mineral oil, and standard Buna-N seals tend to work well. But applications involving synthetic fluids, such as phosphate esters, require Viton seals. Polyurethane is also incompatible with high water-based fluid such as water glycol.

Regardless of the fluid, keep it clean. Contamination and dirt in the fluid will damage Rexroth-BR_CylinderApplicationseals. It can also score the inside of the barrel and eventually ruin the cylinder.

If operating temperatures exceed 300° F, standard Buna-N nitrile rubber seals may fail. Viton synthetic rubber seals generally handle temperatures to 400° F and fluorocarbon seals even higher. When in doubt, assume conditions will be worse than they first appear.

10. Add a gland drain. Probably 90% of cylinder failures are due to the seals. That holds even if engineers specify the proper seals for the fluid, pressure, environment and application as they wear out over time and need replacement. Most experts recommend that seals should be maintained periodically, rather than waiting for failure at a usually inopportune time.

If cylinders are in hard-to-access locations that makes maintenance difficult, or if leaks will damage products or lead to costly downtime, order cylinders with a “gland drain.” This is a special port machined into the cylinder head between primary and secondary seals; or between primary and rod wiper. Then, if the primary rod seal begins to fail and leak, oil bypasses the seal and flows out the gland-drain port—generally through tubing to a collection bottle. If oil collects in the normally empty bottle, it gives a visual indication that seals are wearing out and will soon need replacement.

Cylinders usually have a secondary rod seal or a double-lip rod wiper that temporarily prevents oil from leaking out the rod end, giving maintenance personnel time to schedule repairs.

11. Watch the materials. The type of metal used for the cylinder head, base and bearing can make a significant difference. Most cylinders use SAE 660 bronze for rod bearings and medium-grade carbon steel for heads and bases, which is adequate for many applications. But stronger material, such as 65-45-12 ductile iron for rod bearings, can provide a sizable performance advantage for tough industrial tasks.

Also consider extreme temperatures. Typical carbon steels used in cylinder components are generally suited for around –5 to 200° F. In arctic conditions well below 0° F, for example, standard steel can become brittle and may require alternative materials.

12. Protect the rod. Because the piston rod meets the outside environment, it must resist attack from water, salt air, corrosives, and other harmful substances. In general industrial applications, carbon steel with chrome plating is the norm. But in wet or high humidity environments, such as marine hydraulics, 17-4PH stainless steel with chrome plating is used for most piston rods. Some cylinder manufacturers offer special protective coatings. Bosch Rexroth, for example, offers Enduroq, which is a proprietary thermal-spray coating or plasma-welded overlay that’s applied to rods for extreme corrosion protection and high wear resistance. It’s used in harsh environments, typically for specialty large-bore, long-stroke cylinders.

For dirty, abrasive conditions, engineers have a love/hate relationship with protective rod boots. Installing a boot over the rod keeps out dirt, metal shavings and other external contamination that would otherwise damage the rod and eventually the seals. However, if the boot punctures or rips, dirt gets drawn in and may not get out, which is worse than no boot at all. Maintenance personnel must routinely check for worn or torn boots that could accelerate damage to the cylinder.

Don’t overlook sizing software

Sizing software for cylinders is a great tool, but more engineers need to take advantage of the benefits it offers. These programs address most, if not all, of the pertinent questions designers need to answer to spec the right cylinder.

One such program developed by Bosch Rexroth is the Interactive Catalog System Rexroth-BR_Catalog2 (1)(www.boschrexroth.com/ics). It lets users enter parameters like force, pressure, load, angle of installation and mounting type, and the software sizes the cylinder, lists variations that meet the criteria and offers possible alternatives. It also lets engineers select and test cylinders on-screen before specifying the actual components. In addition, ICS generates dimensional drawings and 2D or 3D models for direct import into AutoCAD or other CAD software.

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Drive for Technology 2016: New products with real benefits

by Harry Aghjian, CEO CMA/Flodyne/Hydradyne

Since 2004, CMA/Flodyne/Hydradyne has hosted a tradeshow and learning symposium every two years for our customers called the Drive for Technology.  The Drive for Technology has become known in our region for being a compact, powerful trade show where attendees can learn about new products and technology in an intimate setting.

This past April 19-20,  the Drive for Technology closed with our highest attendance to date – over 571 customers primarily from Illinois and Wisconsin – and some of the best attendee reviews we have had!

It is encouraging that our customers came from hundreds of miles away to be at the show.  We worked hard to combine an information rich event with some fun.  Our pig roast and barista bars were examples of the “fun” part.  The key for us, however,  was the information portion of the two day event.

The Drive for Technology used three channels to impart new products, new theories & new technologies to our customers:  technical seminars,  hands-on workshops and a vendor trade show.   Using the Internet of Things or, if you prefer, Industry 4.0 as our theme, we highlighted some of the newest technologies known to our industry.

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One such example is the Rexroth MLC-H controller.  MLC-H is the only open architecture controller that allows the mixing of hydraulic axis and electric servo/stepper axis under one programming environment using a digital SERCOS III interface.  The truly revolutionary part of this new technology is its Open Core interface.   Open what?  One easy example to illustrate Open Core: the MLC-H is open to external devices such as smart phones and tablets.  Having an open interface makes the MLC-H  a truly future proof technology supporting all the Ethernet-based protocols!

Another example is the OXiStop, OXS from Hydac.  Simply put, OXS allows us to shrink hydraulic reservoirs by up to 8x (less oil) and reduce operating costs up to 3x.  These are real benefits from products that are brand new to our industry.

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Our final mission was to allow our customers to “take with” the key information that they were presented with at the show.  We supplied an on-line link from our web site to download 100 +MB of information and data complete with application examples from each technical seminar.

Bosch Rexroth, for example, conducted four technical seminars, two workshops and set-up a 40 ft. booth to display their technology.  That’s a lot of information, and our customers were able to digitally walk away with everything that they needed at the end of the two day show.  That’s what the Drive for Technology is all about!

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