New developments in pneumatic valve technology for packaging applications
Pneumatics is widely used in many packaging machines to drive motion and actuate machine sequences. It is a clean, reliable, compact, and lightweight technology that provides cost-effective control and actuation to help packaging machine designers create innovative systems while staying competitive.
Manifold valve technology plays a central role in the performance and effectiveness of pneumatic systems. Recent developments in this technology have increased pneumatic flexibility, modularity, and ability to integrate with and be controlled by the advanced communication bus architectures preferred by leading packaging machine original equipment manufacturers (OEMs) and end users, enhancing the application that value pneumatics technology supplies.
Pneumatics-driven packaging applications
Pneumatics can be particularly effective for machine motion that combines or includes high-speed, point-to-point movement of the types of products that have the weight and size dimensions typically found in packaging machines. This includes indexing, sorting, and pick-and-place functions. It is also used for suction cups or noncontact transfer devices.
For example, on cartoning machines pneumatics can drive multiple functions: indexing the infeed of blank cartons onto the process line, driving machine components that help form the folds then close the carton folds, and moving glue guns or other sealing devices. In form fill and seal machines, its common to have pneumatics-driven clamping devices and heat sealers, as well as tension controllers on rollers discharging the plastic film that forms the bags being sealed.
Four factors continue to make pneumatics broadly appealing to machine builders in the packaging industry.
1. Cost of ownership: Most pneumatics components are relatively low-cost, and systems are relatively easy to maintain and repair without special training or outside specialists, which can add to operating costs.
2. High speeds: Pneumatic-driven systems move products through machine sequences at high speeds-typical systems support motion sequences of up to 5 m/sec (16 ft/sec), and higher-end cylinders support 11 m/sec (36 ft/sec); these rates satisfy a significant percentage of throughput rates found in many packaging machine applications, such as pick-and-place systems.
3. Easy integration: Pneumatic technology is easy to integrate into larger machine designs, highly modular, lightweight, and compact enough to be installed on moving machine elements such as linear modules.
4. Reliability: Pneumatic-driven systems offer the kind of long-lasting reliability expected from today’s automation technologies. For example, one pneumatics suppliers’ valve series has been tested to operate, without device failure, through 140 million duty cycles.
Manifold valves: Control the flow
All pneumatics systems work on the same basic principle: One air source provides all air pressure needed for the different components, and it is the valve system that controls the distribution and sequencing of the air to drive individual actuators.
Standard valve systems typically provide directional flow control; air is supplied through one valve to actuate a pneumatic cylinder and drive the motion cycle on a machine device, and the air is released through the manifold following a different path. Most packaging machines use 12-15 station valve manifolds, but more advanced designs that support up to 64 valves stations are available.
Another common valve configuration is called a 3/2 valve, in which a three-way valve supplies air to an actuator and then allows it to exhaust so the actuator retracts. This type of valve configuration can be a more compact design, since some manufacturers allow two 3/2 valves to be paired in one valve slice for greater flexibility in controlling motion sequences.
Valve design considerations
When selecting a valve system, the main criteria to use are the valve’s flow rate, the weight and space constraints associated with fitting it into a machine design, and the valve’s functionality.
Significant design advances are making valves more compact and modular. This includes the expanded use of high-grade polymers to reduce valve weight. Lightweight construction keeps the valve as close as possible to the actuators it is controlling.
Minimizing the distance from the valve to the components helps reduce installation and connection costs. More importantly, it improves overall pneumatic energy efficiency. Air is considered an expensive commodity in many operations; by mounting a compact, lightweight manifold close to the cylinders (even on the end effector) the lighter weight enables the machine designer to use smaller actuators that are moving that end effector. Lighter weight plus smaller cylinders add up to less energy to supply the air.
Other innovations also have made pneumatic valves more compact and easy to locate within crowded machine spaces or control cabinets. One design uses a diagonal "wedge" shape that positions the pilot section above and on one side of the valve with the air output on the other side. This approach is up to 45% more compact than other designs and provides more airflow than valves of comparable design.
Another valve feature to assess is spool design; the spool is the moving device within the valve that regulates airflow. Some valves use a metal spool designed to fit into a honed housing; others use more lightweight polymer housing with a metal spool and O-ring seals on body of the spool, or the spool housing, to provide a seal and prevent leakage. Each design has its advantages: Seals can wear out and need replacement, however they do reduce leakage and provide better airflow.
Increasing valve intelligence
In packaging automation, demand has increased for pneumatics technologies to provide more sophisticated control and integration of digital intelligence and communications capabilities into their architecture.
When considering a pneumatics platform for a packaging system, it is critical to determine the level of control sophistication the system needs, which will help machine designers and end users select the optimum configuration. Leading pneumatics suppliers are engineering high-throughput multi-protocol bus interface modules that make it much easier to integrate valve manifolds into programmable logic controller (PLC) systems.
Machine builders can select from modules that support most major communications protocols used in the packaging industry, including Profibus DP (by PI North America), and DeviceNet and EtherNet/IP (from ODVA). One network connection replaces older, more costly and time-consuming methods requiring each valve on a manifold to have a standalone communications link with the machine controller.
There is also a trend to integrate input/output (I/O) connections into bus modules saving additional cost: Many pneumatics-driven actuators also have sensors capturing motion data from the pneumatic cylinder via I/O links. By integrating multiple I/O ports into the valve communications bus module, machine builders can eliminate the need for separate I/O bus modules.
Diagnostics, pressure control, safety
Valve designers are investing in new functionality, leveraging capabilities available from the advanced digital bus modules that are being added to manifold valve systems. For example, many machine designers want capabilities for condition monitoring and conduct diagnostics on valve components using feedback loops similar to those used in electric drive systems.
It soon will be possible to monitor the actual position of the spool within each valve on a manifold. By monitoring spool position, the machine can track exactly how each valve performed during a motion cycle, where that valve started, whether it fully shifted or only partially shifted, and final position. This data helps machine builders and end-user operators isolate and correct issues that may affect overall packaging quality and integrity.
Pressure control is a newer capability offered with pneumatic valves. Typically, the manifold supplies the same pressure to all actuators. Certain packaging applications, such as a clamp that is grasping and holding a product, may demand less pressure to handle a sensitive item properly and not damage it. Using the digital bus interface, the machine controller can adjust pressure on an individual valve or series of valves that drive that actuator; this allows one manifold to be used, rather than multiple valves with different pressure ratings.
Built-in safety functionality is another emerging capability, as valve manufacturers consider adding Category 3 and Category 4 exhaust valves to the manifold. Instead of exhausting the air from all actuators controlled by the valve in the event of emergency machine shutdown, it can be done selectively: If certain actuators are holding a load when the machine comes to a standstill, those actuators remain pressurized, while other machine axes are safely exhausted.
Pneumatic valve technology, value
Pneumatic valve systems continue to be improved, with investments in technology to make them more versatile and intelligent in response to the evolving demands of the packaging machine marketplace. Many manifold valve options are available. By considering those engineered to provide compact, lightweight design and use of digital electronics for easy integration into automation controls platforms, packaging machine builders and end users can be assured that solutions provide maximum commercial value.
– Erl Campbell is industry sector manager-food and beverage, Aventics. Edited by Mark T. Hoske, content manager, CFE Media, Control Engineering, firstname.lastname@example.org.
- Cost of ownership, high speeds, easy integration, and reliability make pneumatics attractive for machine builders.
- New pneumatic valve designs help packaging machine builders.
- Diagnostics, pressure control, and safety capabilities will help extend pneumatic applications.
When considering new machine designs, do you examine new packaging automation technologies, including pneumatics?
About the company
Aventics, which was the pneumatics division of Bosch Rexroth, became a stand-alone company in April 2014. The company has production offices in five countries and is represented in more than 40 countries. Learn more here.
– See articles below on pneumatic energy savings, pneumatics for pick and place, and when to apply pneumatic actuation.