Thanks all for your suggestions. Sorry for the lack of details.
The valve which is controlling the cylinder is a 5/2 valve with 3/8 NPT ports. In fact we replaced an old system (a TI PLC with a AB PLC)and we decided to change also some pneumatics (bad idea...).
Before, the cylinder was controlled by a 5/2 solenoid valve (spring return) triggered by a PLC digital output, the only thing we changed was that we put an air actuated valve (spring return also) instead the solenoid valve. The air for the signal comes through a 1/8 hose from the Festo.
Both the valve supply and signal come from the same source - we have 80 PSI. The length of the hose for the signal is about 40 feet, the same is the length from the supply to the valve. The distance between the valve and the cylinder is about 3 feet.
The cylinder is mounted vertical.
My main problem is not the response time (I can anicipate the command in the PLC) but the fact that the response is not constant.
I made some tests:
- for 1 minute, I triggered a 200 msec command every second -- sometimes the cylinder went at full stroke, sometimes it went half stroke, sometimes it didn't respond. If I decreased the command time at 150msec, most of the time the cylinder didn't move at all. If I increased the command time at 250msec, the cylinder responded always but the time it stayed at full stroke was visibly inconstant (I cant tell how much exactly but it was visible). Here I have to mention that the PLC cycle time is about 30msec and stays steady at this value all the time. I have no idea about the response time of the DNET module of the Festo block but it shouldn't be a problem (for an AB VFD I measured a max. of 30 msec delay on DNET so it should be OK, but maybe the Festo module is not so fast - I'll check the specs).
Thanks again all for your help.
Contact us to discuss your requirements of rotating air cylinders. Our experienced sales team can help you identify the options that best suit your needs.
Written by: FABCO-AIR
Compact air cylinders are critical to a wide range of applications, including printing, palletizing, robotics, automotive assembly, semiconductor processing and more. This type of pneumatic actuator provides short strokes in a compact, low-profile design-enabling you to use it in very tight spaces. With bore sizes from 0.5-4 inches and a maximum standard stroke of 4 inches, these cylinders typically feature the longest possible stroke for the smallest package size.
In light of their value and widespread use, it’s important to remember that not all compact air cylinders are created equal. There are a number of products currently competing for your attention and a share of the actuator market. Many of these components have similar features. Some even look alike-featuring the exact same exterior dimensions. How, then, can you decide which cylinder to use?
This white paper provides a helpful overview of air cylinder design and also explores the key features you should look for when selecting a compact cylinder for your application.
To specify the right air actuator, it’s helpful to ask yourself two main questions. The first is: What type of work does the cylinder have to perform? The second is: What types of cylinders do you have to choose from?
Compact air cylinders typically come in a wide range of styles, sizes, and mounting options (see sidebar). They can be double-acting, which is ideal for pushing and pulling tasks like feeding, lifting, lowering, and sorting. They can also be single acting, an ideal configuration if your application requires force in only one direction or involves unloaded return strokes. For safety reasons, single-acting cylinders are also popular if a defined position must be taken in the event of a power failure. Typical tasks for this style include clamping, ejecting, and actuating flaps and levers.
Compact air cylinders also come in single or double rod designs. A more common option, single rod designs often include a spring that extends or retracts the rod. Double rod cylinders, on the other hand, are useful whenever you need equal displacement on both sides of the piston. You can also use the extra end to mount cams for operating limit switches.
In addition to specifying the right configuration, it’s important to make sure your compact air cylinder meets the proper size requirements. Due to their use in tight or limited spaces, look for standard bore sizes between 0.5 and 4 inches, as well as standard strokes up to 4 inches.
For more information, please visit drake in china.
To truly evaluate a compact air cylinder, it’s helpful to take a look at what’s inside. High-performing cylinders will integrate top-of-the-line internal components. Our Pancake® cylinders, for example, incorporate stainless steel tie bolts and aluminum spacers, which lock precision-machined heads tightly around a strong composite cylinder barrel. This type of nonmetallic barrel features a smooth, self-lubricating interior surface that ensures reliable, long-lasting performance. At the same time, its high impact resistance reduces the chances that the cylinder will fail due to damage. By contrast, many compact air cylinders currently on the market integrate stainless steel cylinder walls, which-unlike nonmetallic composites-are subject to dings, dents and other damage. Many also include mirror-finished bores, which make lubrication difficult.
Due to their zero slipstick design, Pancake® cylinders also avoid the stiction problems metal cylinders encounter when they sit in a static position for too long. Combined with hard, chrome-plated stainless steel piston rods, as well as a nonmetallic rod bearing, Pancake® cylinders achieve optimal operation and service life.
The better the bearing, the more cycles you can expect from your air cylinder. Look for compact cylinders with superior rod-bearing materials. Pancake® cylinders, for example, incorporate a fluoropolymer-based composite that is bonded to a supporting filament-wound fiberglass and epoxy resin shell. This material resists corrosion, moisture and temperatures up to 325° F, enhancing the bearing’s load capacity and reliability in harsh environments. Many cylinders on the market feature oil-impregnated bronze bushings, which tend to pull out under side loads. These models also have a lower load capacity than composite options: 4,500 VERUS 60,000 PSI.
In addition to composite cylinder walls and rod bushings, other important internal design features to look for in compact air cylinders include:
Compact air cylinders like the Pancake® series play a critical role in a variety of applications-from conveyor systems to custom-built machinery. These highperforming cylinders come in a variety of styles and configurations. They also meet the right size requirements for use in tight or limited spaces. But most importantly, these cylinders incorporate high-quality internal components-enhancing your cylinder’s durability, reliability and lifespan in short-stroke applications.
Brought to you by FABCO-Air, a partner of DIRECTPNEUMATICS.COM
If you want to learn more, please visit our website drake p3.