Despite an evolution of alternatives, pneumatics have stood the test of time. Hydraulic and electromechanical systems might offer a better solution in certain circumstances, but there are still plenty of pneumatic applications. We gathered input from a panel of industry veterans to determine how prevalent the technology still is and what to consider when making a decision.
Participants include TJ McDermott, project manager at Systems Interface, a systems integrator in Bothell, Washington; Chico Marks, manager of total plant maintenance, Subaru of Indiana Automotive in Lafayette, Indiana; Randy Nobles, regional vice president at Womack Machine Supply; Scott M. Maurer, product manager—air line at SMC; Frank Langro, director, marketing, product management, at Festo; Jerry Scherzinger, marketing pneumatics product manager at Bimba; Nathan Irvine, application and technical support, and Marchelle Forish, senior product specialist at Aventics, and Bill Savela, marketing director at Delta Computer Systems.
What do pneumatics have to offer that still make them a viable solution?
Nobles: Pneumatic systems are still easy to implement and maintain. Also, the operational speed for the amount of money invested is very attractive.
Savela: Pneumatics can provide an optimal combination of force and compliance when controlled by a closed-loop motion controller with special capabilities for controlling both pressure/force and actuator position.
Scherzinger: Pneumatic devices are relatively low-cost and typically highly configurable, making them a great choice for both OEMs and MROs looking to provide a solution. Standard pneumatic actuators can, for example, be ordered in a wide variety of bore sizes, stroke lengths and mounting styles, making them highly flexible and capable of providing forces ranging from a few ounces—small bore sizes with low pressure—to over 10 tons—large bore sizes at 250 psi air pressure—in stroke lengths from fractions of an inch to 10 ft. Additionally, because pneumatics use air as the media, it is a clean source of work when compared to hydraulics, which uses hydraulic oil. A leak in a pneumatic system simply vents air to the atmosphere, but a leak in a hydraulic circuit discharges oil, requiring extensive cleanup and proper disposal.
Langro: Pneumatics can offer a variety of features that still makes it attractive to use. Pneumatics has few electrical connections and can be
suitable in washdown areas. Also, the power density of pneumatics offers an advantage over electrics in applications such as stamping and pressing. When compared to a hydraulic solution, pneumatics can be a cleaner installation, which is clearly important to industries including pharmaceutical, food and beverage and semiconductor.
Also Read: Is Pneumatics Still a Good Solution?
What is your primary reason for choosing pneumatics?
McDermott: In the short term, a pneumatic solution usually costs less than an electric linear motor approach. The capital cost of linear motors typically far exceeds simple pneumatics. However, the longer a pneumatic system is in service, the higher the cost. Maintenance costs climb, and air leaks add to the cost. On the other hand, pneumatic systems are generally easier to troubleshoot. This is especially important when the knowledge pool in a maintenance department is decreasing due to attrition. A linear motor, likely involving a VFD and motion logic, needs maintenance staff skilled in motion control programming. We pick the solutions that fit the application. A pneumatic ram is a good choice for an on-deck hawser winch brake. It's relatively compact for the force exerted, and is easy to maintain and quite robust. For the remote actuator bank, running it via a common Fieldbus protocol such as Ethernet/IP or Profinet is the only way to go. Pulling many conductors for traditional central control is more costly than pulling a single Ethernet cable. The Fieldbus hardware is very reliable and using a device level ring gives redundancy for even more robustness.
Nobles: The primary reasons for using pneumatics are simplicity, compressed air availability and experience. We are seeing interest in conversion to electric actuators, but this trend hasn't been vast.
Savela: Pneumatics excels in applications that require the application of precise amounts of pressure or force, yet those that also benefit from the compliance of the air medium. Using electric motors in such applications would cost more and be more difficult to implement. In addition, holding a load in a pneumatic system can consume less energy, possibly zero, in a closed system, which isn't possible with an electric motor, unless an expensive braking scheme is implemented.
Langro: The choice to use pneumatics, hydraulics, or electrics really should come down to the application requirements. What are you trying to move? How fast do you need to do it? What type of accuracy and repeatability is required? Are you planning to run multiple products that will require constant changeover? What are the environmental considerations? Based on these factors, you start to see which options offer the most viable solution. Pneumatics is a great choice for a case erector where the motion is highly repetitive and the motion requirements are not high precision. In contrast, a wafer inspection process in the semiconductor industry involves variable positions and requires high accuracies and repeatability, making an electrical-type motion solution more suitable for this application.
Can you talk about the types of machines or applications you're using pneumatics for?
Marks: We use pneumatics for the majority of our applications in the plant. They includes automated material handling, parts positioning for welding, paint application and bolt and fastener tightening. We do this with end-of-arm tooling on robots, dedicated clamping and positioning equipment, paint application bells and guns, and handheld fastener tightening torque guns.
Langro: Pneumatics are used in just about every industry that's involved in high- and even low-volume manufacturing. For example, diverse industries such as the automotive, semiconductor, pharmaceutical and food and beverage all have use for pneumatics in their various applications. Pneumatics can be found in the clamping and stamping of sheet metal parts in an automotive press shop, the lifting and transferring of wafers, and the coating of tablets in the pharmaceutical industry. Pneumatics is also found in gas box panels in the semiconductor industry. A common use of pneumatics is in the packaging of products. Pneumatics can be found in just about every machine that forms, fills or seals.
Scherzinger: As a manufacturer, our components—actuators, valves, fittings, manifolds, FRLs—are used on a tremendously wide variety of machines designed for many applications. The applications range from agricultural equipment and transportation vehicles, which need to withstand harsh outdoor environments, to food processing and packaging equipment exposed to corrosive washdown chemicals and medical devices that require a high degree of precision. Common in-plant manufacturing applications include material handling equipment such as conveyor diverters and pick-and-place equipment.
Savela: Fluid power applications in general benefit from the medium's ability to be used when pressure or force must be controlled in an application, and, within these application types, pneumatics excels when the application can benefit from a degree of compliance. Because air is much more compressible than hydraulic fluid, pneumatics can have an advantage in applications where force control is required, but which also need to have some give when an actuator and a work piece come together. Pneumatics are also especially useful in applications where the load can be subject to unknown shocks, bending applications where a force must be applied to the load to do the work, and force-backing applications where the load must have an accurate known force applied to it, such as a metal riveting application. Consider a press roll that is used to hold down lengths of logs as they are fed into a piece of sawmill equipment such as a planer, edger or bandmill. Controlling the press rolls means holding logs tightly without damaging them so as to not destroy valuable timber. Logs can be moving as fast as 2000 board ft/min, and the press rolls may need to sustain a force of up to 1,800 lb in order to maximize productivity. Adaptation of press roll positioning to maintain desired force without damaging the logs, even as log surface profiles are rapidly changing, can be accomplished better using pneumatics than other technologies.
How does a pneumatic solution compare to an integrated linear motor package, when considering cost, footprint and plug-and-play?
Marks: Pneumatics are cheaper and simpler than linear motor packages from both an engineering and maintenance perspective. From an engineering view, PLC-controlled pneumatics are typically easier to design than a motor, requiring less PLC code, simpler position sensing, less complicated motion control, and less costly components. Maintenance enjoys many of the same benefits. Spare parts are both less expensive and simpler to install; they are typically plug-and-play, requiring minimal training and no parameter setup. However, these advantages come with a tradeoff. These simpler pneumatic systems are not as precise in their positioning or motion control as an electromechanical system. While it is true that a pneumatic system can be designed to be very precise, this would eliminate many of the benefits of using pneumatics.
Savela: Pneumatics can handle high-cycle force applications that would degrade electromechanical solutions in a short period of time. An electromechanical solution may be more appropriate for applications which require speeds greater than about 40in./sec or accuracies better than 0.005 in., but most electromechanical solutions will not be able to match the life of a pneumatic solution in a force control application. In general, although they're typically fine for applications that do position control, linear electric motors aren't good for controlling force. Coupled with a proportional valve and precise transducers, a closed-loop motion controller can attain the same level of positioning accuracy as a linear motor, while also controlling pressure/force to a high degree of accuracy. Assuming that the pump, valve and control system can be mounted away from the actuator, but not too far away, a pneumatic solution can have a very small footprint at the actuator site and can place less weight on the moving actuator than a motor would. In applications that must apply and hold a given amount of force on an object, pneumatic systems have the advantage of being able to do so with lower energy consumption than electric motors, even linear ones. From the perspective of ease of use, a pneumatic system incorporating a motion controller with special support for fluid power control can be very easy to set up. For example, Delta Computer Systems' motion controllers are supported by RMCTools, a programming package that employs graphical tools to simplify system development and tuning. An example of one of Delta’s tools is the Plot Manager, which allows the designer to view the actual motion profile versus the target profile, so that errors can be removed via fine tuning. The screen capture below shows a plot made with the Plot Manager.
Nobles: Pneumatic solutions tend to be more cost-effective and have a smaller footprint than a competitive linear motor package. The plug-and-play aspect of these systems is comparable.
Langro: Pneumatics is typically a lower-cost option than a linear motor package and can be operated with a simple electrical signal from a PLC output. An integrated linear motor could be five times the product cost and requires more advanced programming to get the same positioning function. What a linear motor package can offer over pneumatics is flexibility, enabling the machine to be easily reconfigured to handle different products.
Irvine: Pneumatic solutions remain favorable versus electric drives for applications requiring low to moderate force and speed on low to moderate duty cycles. Low initial capital costs and generally long cycle life frequently lead to lower total cost of ownership in such applications.