Pneumatics

Pneumatics have always played an important role in achieving maximised productivity for manufacturing automation applications and the technology is constantly evolving to solve engineering challenges. 

One such evolution is the development of rodless cylinders.

The disadvantages of rod-type cylinders

The limitations of conventional rod-type cylinders are widely recognised, particularly where long strokes are required. Being unsupported, the cylinder rod has a tendency to flex in the extended position which can cause excessive wear on rod seals and bearing leading to the need for additional engineering to avoid premature wear.

Space constraints may also limit the use of rod-type cylinders with the overall length being more than double the stroke length. This can cause problems when designing or mounting cylinders to machinery. In long travel situations, rod-type cylinders can also sag under its own weight and this misalignment can cause the cylinder rod to bind or buckle. 

The disadvantages of rod-type cylinders are:

• Overall length is more than double the stroke length.
• Risk of the piston rod bending, resulting in excessive wear.
• Bad positioning features due to two different piston areas.
• Unequal velocities in forward and return strokes.
• Designed for short stroke length.

The development of slot-type rodless cylinders was designed to eliminate all of these disadvantages.

The construction of rodless cylinders

The rodless pneumatic cylinder has been engineered to be a self-contained linear actuator with a unique design that offers greater design flexibility. With a unique design that uses only four main components, rodless cylinders, such as Parker's OSP range, offer a robust and reliable solution in operation that is simple to maintain; providing long trouble free service. Operated by compressed air, rodless cylinders combine controlled and precise movement with integral support and guidance in any plane.

The rodless cylinder consists of four main parts:

1. The cylinder barrel of extruded anodized aluminium has a slot along its entire length.
    
2. A flexible hardened stainless steel inner band running the entire length of the bore and passing through the piston provides a metal to metal seal. An outer band of the same material acts as a cover over the slot preventing foreign particles from entering into the cylinders interior.
    
3. The aluminium piston is fitted with synthetic bearing rings. The power transmission outwards takes place through a positive, physical connection through the slot to the external piston mounting. This solid guide permits the acceptance of external forces and moments and minimizes frictional losses.
    
4.  End caps providing connections to the air supply, and housing cushioning adjustment screws.

When to use rodless cylinders

The double acting operation of pneumatic rodless cylinders is advantageous in applications where space is limited.

This is because the installation length of a rodless cylinder is only slightly longer than the cylinder’s stroke. For example, 25mm diameter rodless cylinder with 1000mm stroke would only occupy 1200mm of space, opened or closed.

When specifying, a pneumatic rodless cylinder would be the ideal choice over a pneumatic rod-type cylinder to meet the following requirements:

• A source of repetitive linear movement is needed.
• Cleanliness and minimal risk of contamination from lubricants must be assured.
• Space savings are a major design consideration, e.g. long stroke applications.
• Reliability and minimal component maintenance is needed to safeguard against downtime.
• Overall length can present problems when designing or mounting cylinders to machinery.

When optimally selected and applied, the latest generation of smart sensors can have a positive impact on predictive maintenance strategies for fluid power applications.

Real-time data collection via smart sensors can influence decisions about when to schedule downtime to carry out maintenance operations, helping to maximise productivity. 

Maintenance operations are traditionally based on being either reactive or preventative. A reactive strategy means a loss in production and incurring unforeseen costs, while a preventative strategy often sees systems or parts repaired simply because they are listed on the general maintenance procedures, rather than when they actually need it. 

Attention has been gradually shifting to predictive maintenance, spurred on by the emergence of Industry 4.0 and sophisticated ‘smarter’ technologies. For fluid power systems, this means a whole new level of condition monitoring, to the extent that maintenance personnel can determine whether something out of the ordinary has occurred. 

Ultimately, every process has a ‘heartbeat’, so the question to ask is has that heartbeat changed over a certain period of time? Maybe it has become slower or faster, for instance. This is where smart sensor technologies begin to pay dividends. 

The latest sensor technology available for fluid power systems, such as the P8S CPS series from Parker, have evolved to offer high quantities of data which offer the opportunity for plant managers to transform how they operate and maintain industrial equipment. 

Embedded smart sensors can today be integrated with numerous different low-level fluid power products, from connectors, hoses and tubing, to pumps, motors, actuators and filters – all as part of an Industry 4.0 installation. One of the principal opportunities arising from this concept relates to predictive maintenance. For example, some of the diagnostic data generated from control valves could be invaluable in troubleshooting power issues. 

Among the common concerns in fluid power systems is voltage sags that can occur downstream on long runs, which sometimes lead to misfiring valves. Normally, without an oscilloscope, there are no means of diagnosing the root cause of the problem. In contrast, if each valve manifold node included voltage sensing, a ‘sweeper’ program could be written to record voltage levels across the machine during certain periods of the cycle.

Of course, selecting an Industry 4.0-enabled sensor is one thing, but ensuring that it can communicate with other such devices is quite another. For this reason, it is imperative to select a sensor vendor that operates a centralised strategy to ensure that its smart devices and sub-systems share open communications standards and best practices. IO‑Link is the first I/O technology for communicating with sensors and actuators to be adopted as an international standard (IEC 61131-9). This open protocol is bringing the world of Industry 4.0 to component level and already proving essential in ensuring interoperability across multiple technologies and manufacturers.

Consider a pneumatic device, for example, which is being used to grip workpiece blanks and load them into position on a machine tool. Here, the voltage of the coils across the solenoid valves can be monitored for signs of impending failure. In such a scenario, IO-Link can offer budget-friendly communication with low-level devices, connecting them to motion controllers that subsequently connect to a factory network and, if required, to the cloud. 

Smart sensors and other Industry 4.0-enabled devices must work in co-operation with products from other manufacturers. In fact, the value of any connected digital solution is directly proportional to its interoperability. There is no place for proprietary solutions; an open, exchange-based architecture that enables interoperability with third-party products, applications and platforms is essential.

Talk about Industry 4.0 and one recurring area of concern arises - security. Indeed, this issue has been central in discouraging many plants from taking the decision to connect machines and devices to the cloud and gaining the insight required to predict failures and optimise performance at the component level. 

For any company concerned about this issue and seeking guidance on how to move forward, this is the point where choosing the right vendor is of the essence.

It is critical to choose suppliers who can share technical knowledge and hands-on experience gained from working across a wide range of advanced applications.

With a specific focus on fluid power installations, the selected vendor should be able to offer advice on where sensors need to be integrated to obtain optimal insight, the type of data to collect, and how to present the results to MRO (maintenance, repair and operations) personnel in the way that is most useful. Progressive, forward-thinking vendors are striving to bake in best-practice data encryption in motion and storage to create secure end-to-end Industry 4.0-enabled systems. 

Using the latest sensor intelligence is now about far more than simply monitoring factors such as position and speed. It’s about using data, collected in real time, to provide vital information concerning service life that can help facilitate the implementation of predictive maintenance. This data can be used to identify when a machine or system is not functioning correctly, or at its optimum efficiency. Early sensor notification of issues allows system operators to investigate, consider, plan and schedule the required corrective maintenance for a time when production throughput is either low or can be stopped. This could be overnight, during a larger planned plant maintenance shutdown, or whenever there is the least impact on those all-important customer delivery schedules.

Continuous position sensing devices can make a significant contribution to creating a smarter, more efficient factory environment. To find out more, download our CPS Smart Sensing Brochure that covers continuous position sensing using analogue signal or IO-Link communication for linear actuators, and discover how you can better schedule corrective maintenance and reduce your downtime.

Article contributed by Franck Roussillon, product manager, actuators, Pneumatic Division Europe, Parker Hannifin Corporation.

Related content

Learn how to make your predictive maintenance "smarter"

What is the Foundation for a Smart Factory?

Know Your Pneumatics: Understanding IO-Link

The use of industrial networks to make sensors and actuators more intelligent has become common across modern factory environments, and the use of continuous position sensing is a pathway to achieving smart motion control in pneumatic systems.

Continuous position sensors are more sophisticated sensor devices with two-way data flow that help to bring intelligence to pneumatic motion control and provide necessary continuous data to help facilitate a true Industry 4.0 environment. 

Using contactless technology to continuously detect the linear position of a piston in its cylinder, the quick, precise and high-resolution sensing of the piston magnet is achieved without the need for separate position encoders or additional mechanics, therefore minimising the cost of implementation.

The data communicated by the sensor allows for monitoring, and when information flows in both directions and actuators are employed, control. The result is that positional data is made available for fast detection of any issues that might cause downtime or potential loss of productivity.

Easy mounting
For cylinders, linear slides and grippers with common T-slot or C-slot dimensions, the latest continuous position sensors, including the P8S CPS series from Parker, can be mounted without the need for extra accessories. Mounting on other cylinder types, such as round body, tie-rod and profile cylinders (and cylinders with a dovetail groove), is possible using a simple adaptor.

By externally mounting on the cylinder body, you avoid complicated integration requirements or any drilling of the piston rod itself. This design also facilitates quick and simple sensor maintenance or replacement. 

Application benefits
Among the principal benefits of continuous position sensors is the ability to monitor quality and provide process control and support optimisation, especially in tensioning applications such as paper or film processing where quality, repeatability and speed are paramount to profitable operations.  

Here, the remote reading of data from position sensors allows process deviations to be seen quickly and acted upon, thus keeping processes optimised and supporting predictive maintenance strategies.

Many other types of applications will also benefit, including materials handling, consumer packaging, small component assembly, machine building, and even tasks in the renewable energy industry, such as the positional control of solar panels as they track the sun.

With the appropriate shock, vibration, moisture, chemical and water ingress resistance, continuous position sensing can be used in challenging environments reliably over very long periods of time.

Two-way data flow
The monitoring of sensor data via traditional discrete or analogue signals is one-way communication; this is sufficient to allow the remote monitoring of automated processes, for example. However, in order to implement Industry 4.0 strategies, two-way communications are required meaning a connection to a network such as Profinet or IO-Link. In terms of Continuous Position Sensor implementation with pneumatics, it would include not only monitoring but also automatic configuration at start up and/or during maintenance replacement.   

In many cases, the early sensor notification of issues allows system operators to investigate, consider, plan and schedule the required corrective maintenance for a time when production throughput is either low or can be stopped. This could be overnight or during a larger planned plant maintenance shutdown.

Leveraging IO-Link
Another critical part in the success of Industry 4.0 manufacturing strategies is choosing the right protocol to connect sensors with controllers and actuators. Here, IO-Link provides the ideal solution, allowing two-way communications to receive data and then download a parameter to the device/actuator. As a result, processes can be adjusted remotely.

The advantages of IO-Link include the automatic detection and parameterisation of the IO-Link device, device monitoring and diagnostics, changes on the fly and reduced spare part costs.

Ultimately, the key to unlocking the power of smart sensors is in making diagnostic information easy to access. IO-Link allows for cyclic data exchange capabilities so that programmers can easily send the information directly to where it is required, either to an HMI screen, a signal light or a maintenance request. If sensor or actuator parameters need to be changed or calibrated, this can be done remotely, even while the production line is still running, ensuring that shutdowns, stoppages and unnecessary costs are avoided.

Learn more

Continuous position sensing devices can make a significant contribution in creating a smarter, more efficient factory environment. To find out more, download our brochure and discover how you can better schedule corrective maintenance and reduce your downtime.

Article contributed by Franck Roussillon, product manager for actuators, Pneumatic Division Europe, Parker Hannifin Corporation

Related content

Learn how to make your predictive maintenance "smarter"
What is the Foundation for a Smart Factory?
Know Your Pneumatics: Understanding IO-Link

Machinery and moving equipment is a vital element in all areas of modern automated industry, but what happens when the atmosphere in the working environment is potentially explosive? 

• Present continuously or for long periods (Gas Zone 0)
• Likely to occur in normal operation occasionally, typically between 10-1000 hours per annum (Gas Zone 1)
• Not likely to occur in normal operation, but if it does occur it will persist for a period typically less than 10 hours a year (Gas Zone 2)

• Group 1 equipment is intended for use in underground mines and surface installations of such mines likely to be endangered by flammable vapours and/or dusts
• Group 2 equipment is intended for use in other places exposed to explosive atmospheres. 

Article contributed by Franck Roussillon, european product manager for actuators, Pneumatic Division Europe, Parker Hannifin Corporation