Pneumatics

Linear actuators are used in many applications around industry. Pneumatic, hydraulic and electromechanical technologies are the primary options for providing linear actuation but the selection and use of these technologies depends greatly on technical knowledge, budgets, available energy sources and careful consideration of the performance trade-offs of different approaches.

For example, pneumatic actuators don’t deliver high force output but are practical when a cost-effective, easy start-up is required. Conversely, hydraulic linear actuators are suited to high force applications but generate a lot of noise. And, while electromechanical actuators are quieter, they are much more difficult to install and maintain. 

So, what are the considerations and trade-offs when selecting linear actuators for a linear motion application?

There have been several recent improvements in pneumatic design, including positional feedback capabilities from proximity and linear position sensors. Better sealing has also allowed pneumatic linear actuators to be used more often in challenging environments or applications requiring wash down. 

However, pressure losses and the compressibility of air can make pneumatics less efficient than other linear technologies. While the speed ranges from a couple of centimetres per second to 150cm/s, force output is dependent on the maximum pressure rating and related bore size. Typically, however, pneumatic actuators have a maximum pressure rating of 10bar with bore sizes ranging from 12 to 320mm for approximately 80N to 80kN. 

Hydraulic systems therefore have a much higher possible force output, with typical pressure ratings up to 210bar with bore sizes ranging from approximately 12 to 355mm translating to about 220 to 171,000N of force. Hydraulic actuation also generates a significant amount of noise and, without proper maintenance, can leak.

When driven by a rotary motor, electromechanical linear motion systems employ one of four rotary-to-linear conversion systems: ballscrew, roller screw, Acme (lead) screw or belt drive. In addition, a linear motor can be used to provide motion.

A linear motor is similar to a rotary motor, but the motor coils make up the forcer. Depending on the design, one or two rows of magnets comprise the magnet track. In a rotary motor, the rotor spins while the stator is fixed, but in a linear motor, either the forcer or the magnet track can be the moving component, which is then integrated with an appropriate linear bearing. By sending electrical current to the forcer, the resulting magnetic field interacts with the magnet track and drives the linear motor carriage back and forth. 

Linear motors have high dynamic performance, with acceleration of greater than 20G at velocities of 10m/s or higher. Due to the direct drive nature of linear motors, there are no mechanical components to add backlash, torsional wind-up, or other positioning errors. Sub-micron resolution and repeatability are achievable and as the motor is directly coupled to the load, there are fewer components to fail, which adds long-term reliability.

Pneumatic, hydraulic and electric actuators are an integral part of automated systems, and there is no better actuator than another as the choice depends on the peculiarities and application needs. Today, the three technologies appear to be well developed and with a good level of maturity that guarantees long life and good reliability although with different operating characteristics. Placing a priority on one type of application parameter could mean that performance in another area might be sacrificed, but nevertheless all the decision making categories should be carefully weighed up before making the final choice of actuator equipment. 

This article was contributed by Franck Roussilon, product manager, Pneumatic Division Europe, Parker Hannifin Corporation.
 

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Linear actuators are used in many applications around industry. Pneumatic, hydraulic and electromechanical technologies are the primary options for providing linear actuation but the selection and use of these technologies depends greatly on technical knowledge, budgets, available energy sources and careful consideration of the performance trade-offs of different approaches.

For example, pneumatic actuators don’t deliver high force output but are practical when a cost-effective, easy start-up is required. Conversely, hydraulic linear actuators are suited to high force applications but generate a lot of noise. And, while electromechanical actuators are quieter, they are much more difficult to install and maintain. 

So, what are the considerations and trade-offs when selecting linear actuators for a linear motion application?

There have been several recent improvements in pneumatic design, including positional feedback capabilities from proximity and linear position sensors. Better sealing has also allowed pneumatic linear actuators to be used more often in challenging environments or applications requiring wash down. 

However, pressure losses and the compressibility of air can make pneumatics less efficient than other linear technologies. While the speed ranges from a couple of centimetres per second to 150cm/s, force output is dependent on the maximum pressure rating and related bore size. Typically, however, pneumatic actuators have a maximum pressure rating of 10bar with bore sizes ranging from 12 to 320mm for approximately 80N to 80kN. 

Hydraulic systems therefore have a much higher possible force output, with typical pressure ratings up to 210bar with bore sizes ranging from approximately 12 to 355mm translating to about 220 to 171,000N of force. Hydraulic actuation also generates a significant amount of noise and, without proper maintenance, can leak.

When driven by a rotary motor, electromechanical linear motion systems employ one of four rotary-to-linear conversion systems: ballscrew, roller screw, Acme (lead) screw or belt drive. In addition, a linear motor can be used to provide motion.

A linear motor is similar to a rotary motor, but the motor coils make up the forcer. Depending on the design, one or two rows of magnets comprise the magnet track. In a rotary motor, the rotor spins while the stator is fixed, but in a linear motor, either the forcer or the magnet track can be the moving component, which is then integrated with an appropriate linear bearing. By sending electrical current to the forcer, the resulting magnetic field interacts with the magnet track and drives the linear motor carriage back and forth. 

Linear motors have high dynamic performance, with acceleration of greater than 20G at velocities of 10m/s or higher. Due to the direct drive nature of linear motors, there are no mechanical components to add backlash, torsional wind-up, or other positioning errors. Sub-micron resolution and repeatability are achievable and as the motor is directly coupled to the load, there are fewer components to fail, which adds long-term reliability.

Pneumatic, hydraulic and electric actuators are an integral part of automated systems, and there is no better actuator than another as the choice depends on the peculiarities and application needs. Today, the three technologies appear to be well developed and with a good level of maturity that guarantees long life and good reliability although with different operating characteristics. Placing a priority on one type of application parameter could mean that performance in another area might be sacrificed, but nevertheless all the decision making categories should be carefully weighed up before making the final choice of actuator equipment. 

This article was contributed by Franck Roussilon, product manager, Pneumatic Division Europe, Parker Hannifin Corporation.
 

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IO-Link is a point-to-point communication technology that can be implemented into most PLC configurations or integrated into most existing industrial Ethernet networks via a device called IO-Link master. It is the first standardized IO technology worldwide (IEC 61131-9) for point-to-point communication between sensors, actuators and control devices – comparable to an “industrial USB” and is the perfect local extension of a superior industrial Ethernet network. Thanks to its simple installation, better control and enhanced diagnostics capabilities, IO-Link has already secured a large user base.

There are multiple advantages for engineers when designing an IO-link architecture for their latest equipment. For example: when applying a Parker IO-Link connected Moduflex valve island, in addition to simplified and standardized wiring, they can also realize the benefits of remote configuration, monitoring, and increased data availability, leading to enhanced diagnostics. Utilizing IO-Link can also be especially beneficial for machine applications where there are frequent changeovers or reconfiguration as this time can be reduced, as can unplanned downtime.

IO-Link doesn’t require any special or complicated wiring, which is a major benefit for adopting it as a communication method. Instead, IO-Link devices can be connected using standard 3 or 5-wire M12 cables, the same you would use to connect a standard proximity switch.

If previously you were using 25-pin wiring for a pneumatic valve manifold, then an upgrade to IO-Link would offer similar diagnostics and performance as with an industrial network (e.g. Profinet) but at a significantly lower cost and with a less complex system:

•    Highly cost-effective solution - It replaces an analog I/O and its 4-20mA/0-10V signal with the IO-Link digital information from an analog sensor, or to an analog device such as pressure regulator, saving on inventory costs
•    Enables possibilities for customer to de-centralize devices - On small- to medium-sized machines, many of the available IO-Link masters are IP67 and can be placed on the machine near the I/O points instead of in a centralized cabinet
•    Suitable for SAFE power source - Some IO-Link devices, such as the Parker’s IO-Link valve islands solution, are even suitable for use with a SAFE power source which is becoming an important requirement on many markets due to machine directives

IO-Link offers an increase in availability of data to the PLC, which helps to reduce time and money spent on troubleshooting analysis. There are three data types available:
•    Process data – Cyclic information that is transferred between device and the master automatically on a regular basis, used as I/O for the machine controls
•    Service data – information about the device itself, such as model and serial number, or error messages and maintenance warnings (e.g. device overheating, maximal current is exceeded, coil short circuit)
•    Parameter data – information that can be written in, or read from the device on request such as voltage level or counting cycles to support preventive maintenance needs

With IO-Link, you can read and change device parameters through the control system software which enables faster configuration and commissioning, plus changes can be made dynamically from the control system as needed. IO-Link also offers the ability to monitor device outputs, receive real-time status alerts, and adjust settings from virtually anywhere. Users can identify and resolve problems that arise in a timely manner and make decisions based on real-time data from the machine components themselves.
With visibility into errors and health status from each device, users can see not only what the device is doing but also how well it is performing. These extended diagnostics allow users to easily identify when a device is malfunctioning and diagnose the problem without shutting down the line or machine. The combination of real-time and historical data available via IO-Link helps to ensure smooth operation of system components, simplifies device replacement and enables the operator to optimize machine maintenance schedules – saving cost and reducing the risk of machine downtime.

Many general pneumatic control applications can benefit from such modules, including packaging machines, automotive systems and factory automation. In fact, if you happen to visit any automotive or packaging facility, the ‘elephant in the room’ will be clear to see: the big controller cabinet housing the PLCs and contactors. These cabinets consume valuable floor space, but now they are set to shrink in size. Safety relays are increasingly moving out of the cabinet, and trends indicate that PLCs are soon to follow. This ‘do more with less’ business model should encourage any of you who typically still hard-wire valve manifolds, to make that leap towards industrial networks such as IO-Link.
 
 

Use our configurator on Parker.com to discover how you can utilize IO-Link for your application.

Article contributed by Patrick Berdal, EMEA product manager for control devices, Pneumatic Division Europe, Parker Hannifin Corporation.

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Parker's Central Tire Inflation System (CTIS) offers improved mobility when operating vehicles in severe off-road or soft soil conditions. Ideally suited for the agriculture and military markets, this automatic tire pressure adjustment system allows the driver to optimize tire inflation pressure from the cab while operating on varying terrains with the simple push of a button. Reducing tire pressure results in a bigger tire footprint, providing increased flotation and traction when operating in soft soil terrain. Although often used in conjunction with all-wheel drive, non-all-wheel drive vehicles with CTIS can actually outperform all-wheel drive in many soft soil conditions.

Operating vehicles with reduced tire inflation pressure is approved by tire manufacturers when operating at reduced vehicle speeds. Contrary to common perception, operating at reduced tire inflation pressure can extend tire life due to reduced susceptibility to tire punctures and tread chunking. CTIS also results in increased fuel economy due to the improved rolling resistance as the tire floats on the surface rather than creating ruts in soft soil or sand.

Each wheel end is equipped with a CTIS wheel valve. The wheel valve connects the tire to the CTIS control system whenever it is actively measuring or changing tire pressure. Otherwise, the wheel valve is closed, isolating the tire from the system, thus ensuring that the tire will not leak down. This eliminates the need for manually operated shut off valves when the vehicle is inactive for extended periods of time. This feature also provides extended air seal life when the vehicle is in motion and tire pressure adjustment is not occurring. Parker offers wheel valves in a variety of sizes and configurations including valves with hose connections as well as flush-mount hose-less versions for use with wheels that have integral air passages. Located on the vehicle chassis or undercarriage, Parker’s CTIS pneumatic control unit consists of electro-pneumatic valves and pressure sensors required to monitor and control the pneumatic system.    

CTIS provides independent wheel-end control ensuring fail-safe operation in the event of damage to the vehicle or wheel end. The CTIS wheel valve is completely sealed to the atmosphere at the wheel end ensuring reliable deepwater forwarding capability. Tire venting while deflating is routed back through the pneumatic control unit rather than at the wheel end. The CTIS electronic control unit provides decision making and logic execution. The electronic circuitry is completely sealed in an aluminum enclosure resulting in a rugged environmentally robust package.

Vehicle mobility is improved by reducing tire inflation pressure resulting in a larger tire footprint. This bigger footprint improves traction, reduces wheel slip and allows the vehicle to float across the soft terrain instead of compacting the soil and causing rutting. When returning to improved terrain conditions, a simple push of a button on the driver interface automatically inflates the tires to the appropriate pressure utilizing the onboard air compressor.

Its unique wheel valve design provides the best in class deflate performance while incorporating the non piloted remote venting control strategy preferred by most vehicle manufacturers. CTIS can deflate tire pressures significantly lower than the competition while operating reliably over a wide range of temperatures and altitudes. The CTIS is insensitive to vehicle installation variables such as wheel-end, the back pressure and air seal flow. This results in enhanced fault tolerance as wheel valve shutoff is assured even with kinked, contaminated or restricted airlines. This is a patented wheel valve design that gets the job done faster, resulting in industry precedent-setting deflation rates. The operator interface provides the ability to select four terrain modes:

• Highway
• Cross country
• Mud, sand and snow
• Emergency mode

Pressing any of the terrain buttons results in the system checking all tire pressures and then automatically adjusting them to pressure targets. A green light on the driver interface will flash while pressure changes are being made and then turn solid indicating that target tire pressures have been reached. The operator can also select from three load levels: no load, partial load and full load optimizing tire pressure for load improves fuel economy, vehicle stability and ride comfort. 

The CTIS monitors tire pressure at regular intervals and offers a run-flat mode which reduces this interval to almost continuously monitor pressure. This is useful when an increased threat for puncture exists. CTIS will return to normal pressure check intervals after a predetermined time has expired. 

The system also monitors vehicle speed and provides both an over-speed warning and an automatic terrain mode bumper to ensure safe operation operators can run in an overspeed condition for a short period of time, for example, to preselect for an impending terrain change continue to over-speed will result in the amber warning led on the selected terrain button beginning to flash. If the vehicle speed is not reduced within an additional time, CTIS will automatically bump up the terrain mode to a more appropriate setting and inflate the tires to the new target pressure. This staged approach allows the operator to pre-select terrains as needed while protecting tires from damage.

Watch the video to learn more and see a vehicle in action:

Parker off-highway and mobile solutions will be showcased at IFPE/CONEXPO-Con/AGG in Las Vegas March 10 – 14. The Parker CTIS system will be on display. The CTIS offers best in class performance, including tire pressure control range and deflate rates with robust full tolerance. Parker is the global leader in motion and control technologies. For more information regarding Parker's central tire inflation systems, contact us.

Article contributed by Ryan Mills, project engineer, Parker Hannifin's Pneumatics Division.

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Starting from agriculture and food processing arriving to the packaging operation, automation is everywhere in the modern food plants and plays a fundamental role to address the required control movement quality, production speed, labour savings and overall profitability. Especially for food zones and wash areas, where there are multiple national and international standards to take into account and frequent cleaning and sanitising cycles to support, pneumatics offers a cost-effective choice. Applications in food production typically require specific certification for air motors, pneumatic cylinders and other associated equipment and special clean design features that minimize entrapment points for bacteria.

Food production environments necessitate frequent wash-downs of the work area, which can lead to damage to static and dynamic gaskets and seals. Constant exposure to damp and the caustic sprays of hydrogen peroxide and other cleaning materials used in wash-down cycles can eat away at unprotected materials. These environmental challenges have made stainless steel the most commonly used material for all food processing applications. Although stainless steel is more expensive than aluminum, it can resist the steam, high pressure water and caustic cleaners often used in food and beverage production. Parker P1VAS air motor and planetary reduction gear for example is built into a polished stainless housing that is sealed by a fluorocarbon rubber O-ring. The output shaft, which is made of polished stainless steel, is also sealed by a fluorocarbon rubber seal and thanks to the cylindrical shape, there are no pockets that can accumulate dirt or bacteria. 

No matter which component is being specified, it’s critical to understand the details of the food processing application and what is required - such as pressure, temperature, flow, port sizes, configurations and locations. Too often, filters or valves are chosen based on cost or size alone, forcing maintenance personnel to spend extra time on maintenance as a result of the system designer’s less than optimal choice. Longevity and repeatability are basic requirements for any good pneumatic solution. The choice should be made on products that have been thoroughly tested and designed to withstand the toughest conditions for operation, vibration and impact.

The accessories and options for pneumatic components are frequently neglected, so it’s important to ensure the entire product can withstand the environment where it will operate to avoid forcing maintenance personnel to waste time replacing parts. For example, the adjustment knob or T-handle of a typical regulator is made of a composite material. The caustic chemicals used in wash-down can corrode many types of plastic, so in addition to a stainless steel regulator, the knob should be made of stainless steel or other compatible material.

Filter-regulator options such as tapped manual drains or automatic stainless-steel drains are widely used to get rid of excess liquid and prevent water from draining onto the floor. Look for non-relieving regulators that do not release gases or liquid into the atmosphere. Whenever possible, select pre-lubricated or lubrication-free mechanisms that use food-grade grease and don’t require periodic lubrication.

Although some pneumatic valves meet NEMA protection standards or IEC/IP ratings, most are designed to be mounted in an enclosure to protect them during wash-downs. Check the design of this enclosure for any crevices between the valves and subplate or manifold bases and other non-smooth surfaces that can harbor bacteria. For those who use serial communications with their valves, these electronics also require protection.

Components that require lubricated compressed air or periodic manual lubrication should be avoided when working in food processing to minimize the risk of product contamination. Lubricant in the compressed air can collect near exhaust ports, and manually applied lubricant can spill onto or collect on multiple components.

Using dry air in non-lubricated applications is critical; condensation can corrode system components, increasing maintenance costs and reducing system efficiency. Also, unless distribution air lines are made of stainless steel, aluminum, or high-strength plastic, water can create pipe scale that can work its way into components and cause malfunctions. Water is a poor lubricant; when emulsified with residual compressor oils, it becomes a milky substance that must be drained away. In addition, there should never be any contact with synthetic emulsions in food processing. Dry, filtered, non-lubricated air usually eliminates these issues.

Find out more information about P1VAS air motors in this video.

This article was contributed by Franck Roussilon, product manager, Pneumatic Division Europe, Parker Hannifin Corporation.

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In the world of industrial automation, pneumatic rodless cylinders can now be found just about anywhere; from food and beverage packaging to pharmaceutical and chemical production lines. They have a significant advantage over more conventional rod-type cylinders because they are fast, efficient, capable of supporting high direct and cantilever loads and are smooth-running. In addition, they require only about half the space compared to their traditional counterparts.

They are also easily adjustable and offer air cushioning at the end positions. This serves to dampen the piston as it reaches the end of its travel, thereby slowing down the speed of the load at the end of the stroke to prevent unnecessary impact or shocks. Without the right setting, the service life of the overall system will be considerably shorter and generate potentially problematic vibrations throughout the entire assembly line.

Adjustable cushioning can be tailored to specific applications and is therefore more efficient than cushioning preset by the manufacturer, which can only assume a standard load and the speed at which it needs to travel. By adjusting the cushioning settings, which is known as “ideal cushioning”, the piston is decelerated to zero velocity at the end of the stroke, thereby dissipating all kinetic energy in the load. Therefore, shorter cycle times are achieved because with no piston bounce, no time is lost due to shock or vibration. System wear is reduced as the ideal cushioning eliminates shocks to the cushioning sleeve, thereby increasing the lifetime of the cylinder. Productivity is also ultimately improved when the system is at optimal operation, working well on a continuous basis without force, shocks or vibrations.

Let us take a look at the correct way to adjust the end position cushioning on a Parker ORIGA OSP-P pneumatic rodless cylinder to ensure shorter cycle time, less wear, higher productivity and longer product lifetime. This is recommended for any Parker rodless pneumatic cylinder before first use.

It is recommended that six bar of operating pressure is used for the adjustment process; any variations in pressure will require a slightly modified adjustment process. 

The adjustment screw is located at the cylinder's end caps.
All you will need to perform the adjustment is a small slotted screwdriver. 

With the fine thread of the cushioning screw, there is a high degree of sensitivity and set-up can be completed very accurately. The cushioning screw itself is secured against completely unscrewing. The factory setting of a Parker rodless cylinder cushioning adjustment screw is approximately one half turn open.

Firstly, loosen the cushioning adjustment screw by one full turn.
The piston re-bounces from the air cushion causing it to vibrate.
Cushioning must be slowly adjusted by loosening the screw turn-by-turn.
Cylinder noise will increase slightly but the piston vibrations will immediately start to decrease.
The vibrations will continue to decrease as you loosen the cushioning screw.
The noise will continue getting louder - this is completely normal for the adjustment process. 
Continue to slowly loosen the cushioning screw until the vibrations stop.
The cylinder will now become quieter until the noise is barely perceptible.
The piston will gently move into the end position.
The adjustment process is complete.

The ideal cushioning will increase productivity and output and will reduce costs at the same time.

To find more information on how to adjust the end position cushioning of the Parker ORIGA Series of pneumatic rodless cylinders, please see this video:

Article contributed by Dieter Winger, Product Manager, Pneumatic Rodless Actuators, Pneumatic Division Europe, Parker Hannifin Corporation

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