Below is the list of the last 5 critical cylinder selection practices that should be considered when selecting the perfect air cylinder for the task at hand.

F. Add speed requirements into the equations
Once all forces are calculated, now keep in mind that it is the excess force that causes movement. The acceleration will be equal to the excess force divided by the total mass being moved (A=F/m). The total mass includes the cylinder piston rod assembly. Keep in mind that the air must get to the piston in a timely manner to build air pressure to produce the force that will cause acceleration. If the air cannot be delivered quickly enough, then the pressure, force, and even the acceleration will not be adequate.
G. Be sure to consider the angles
If you are dealing with linkages or have a force transfer angle, be sure to allow for force losses in angles. This can happen when force is working against a pin or other pivoting angles. The force transferred to the application is equal to force times sin (transfer angle), and the force absorbed by the pivot is equal to force times cos (transfer angle). When the transfer angle is above 135 degrees or below 45 degrees, more of the cylinder force is acting against the pivot than is being transferred to the application. Transfer angles above 150 degrees and below 30 degree transfer less than half the cylinder force to the application and simply should be avoided.
H. Design for slight future productivity requirement additions
Designing your cylinder to “max out” does not allow for future flexibility. It is always a good idea to allow for future productivity increases or even unforeseen force losses. You can always add a regulator to reduce the output force but it is difficult to add additional force.
I. Consider the kinetic energy
The mass has started moving and now what do I do? Don’t forget the kinetic energy associated with a moving load. Air cylinders have some ability to absorb kinetic energy but remember that their primary function is to convert pressure to linear force. When an external shock absorber is used effectively, they can transform a potentially destructive moving load into an expectable application.
J. Test
Not testing while trying to size an air cylinder for a specific application can be a great mistake. Once application hardware is in place, it can extremely costly to make adaptations for a larger diameter air cylinder. Often times, the entire application must be completely redesigned. Unless you are against strict time restrictions or you like to redesign your application, it is always a good rule of thumb to oversize your cylinder.

These simple steps in the beginning will ensure that your air cylinders will keep your production levels at a pinnacle.

Air Cylinders Direct is proud to announce another new product. The ESH Series is a guided linear motion device capable of heavy loads and moderately long strokes. The slide body is hardcoat anodized aluminum and the air cylinder is a high quality stainless steel body and rod cylinder.

Features
• Bore Sizes: 5/16" - 3"
• Strokes: Up to 32"
• Body: Hardcoat anodized aluminum (6061-T6511)
• Cylinder: Stainless Steel body & rod (corrosion resistant), up to 3" diameter bore size
• Alignment Coupler: 360° of float, eliminates side-loading of the cylinder
• Tooling Plate: Universal mounting pattern with standard dowel locating holes.
• Guide Shafts: Hardened Steel, (stainless available), large diameters for increased load capability
• Bearings: Precision bearings sealed with rod wipers (self-aligning, self lubricating, low friction, maintenance free)
• Bumpers: Durable polyurethane material
• Adjustable Shaft Collars: End of stroke adjustment

Air cylinders are offered in a variety of shapes, sizes, and types as well as with a multitude of standard options. At first glance, the number of permutations can be a bit overwhelming. The good news is that each actuator type and configuration has a place in today’s motion-centric automation environment.

Pneumatic actuators are selected by their ability to do work. To ensure maximum production, proper actuator selection is vital. Actuator application lives are often predestined long before the product is ever applied. The most common contributing factor that limits productivity is using an undersized actuator.

Below is a list of critical cylinder selection practices that should be considered when selecting the perfect air cylinder for the task at hand.

A. Determine the force
The theoretical force of a cylinder is the usable piston area multiplied by the applied air pressure (Force = Pressure X Area). For example, a 1-1/2” bore air cylinder with an extend force at 80 psi would generate 141 lbs. of force (1.767 X 80 = 141). Keep in mind that this is the theoretical force output and there can be several additional factors that can cause the actual application force to decrease.

B. Subtract the piston rod area, if applicable
The hypothetical force output is the usable piston area multiplied by the air pressure. If the cylinder is performing work on the return stroke, or you are using a double-rod cylinder, you must subtract the area of the rod to determine the actual usable piston area.

C. Know the true operating pressure
Although an air compressor may be able to produce a given pressure, the actual air pressure that the cylinder receives in the application may be much lower because of a multitude of factors.

D. Allowance of internal actuator friction, i.e., seals, bushings, wears bands, etc.
An air cylinder will never reach its theoretical force output because of internal friction. Friction is produced by cylinder seals, bushings, and other load support items, i.e., wear bands. The actual force loss can be between 1 to 10 psi of theoretical cylinder force output. Often, the determining factor depends on the seal type used by the cylinder manufacturer.

E. Know the true cylinder load
Unless the load is being lifted vertically, it can be fairly difficult to determine the actual load in question. Calculating force loss due to sliding friction can be a daunting task as well. This is difficult because the friction factor (Friction Force = Normal Force X the Coefficient of Friction). Please note that if you are sizing for an existing application, it is imperative that you measure the required force. If you are sizing for a completely new application, perform as much physical experimentation as possible to validate the calculations.

The last 5 keys (F - J) will be on the next update.

Air cylinders are offered in a variety of industry standards. Within these standards, air cylinders come in an assortment of shapes, sizes, and types, as well as with a multitude of standard options. At first glance, the number of permutations can be a bit overwhelming. The good news is that each actuator type and configuration has a place in today’s motion-centric automation environment.

Even though the air cylinder market includes a multitude of standard options, pneumatic actuators are still selected by their ability to do work. Sometimes the job at hand simply falls outside the standard product offering and only a tailored or custom air cylinder will suffice. The development of custom or tailored air cylinders can often be both expensive and time consuming. We have outlined this step-by-step process to ensure that your time and investment is well spent.

In order to properly specify a cylinder for any application, it requires that two main questions be answered before moving into the heart of the design. The first question is: what do I need the cylinder to do (what type of work will it be performing)? The second is: what types of cylinders do I have to select from? As previously mentioned, there are many standard cylinders types available to fit most applications, but often times there are design issues that keep a standard unit from meeting your specific requirements.

Before you charge into the specifics of your application, you should try to determine the basics of what you need. First you need to establish the force required to do the work you desire (Force = Pressure X Area). By using what you have, you must determine how much pressure you will have available to the cylinder as well. If you do not have enough pressure to produce the desired force using the preferred bore size cylinder, then you must go to a larger unit. This will affect the package size and may create some space requirement issues, so there is generally a balance that must be achieved. Stroke is usually a given in most applications, so decide on the stroke early on so you can figure out how much area that you will have available when addressing the mounting style. Mounting can be the most challenging issue. Subsequently, determine the way you would like to mount the unit and then decide if you have the proper structure and space to do so. This is a very basic concept, but failure to plan here can demolish your plans quickly. For example, if you would like to flange mount a unit but there is a fitting in the way of your mounting surface, it may force a redesign to a bottom mount where an additional plate may need to be added. Finally, you must figure out how much room you have available. At this point, you should have addressed the question of "what do you have" and all or a large portion of the question "what do I need."

Specialty cylinder applications start when you have addressed the questions and you are left with more questions or there is not a standardized cylinder that meets your specific application requirements. At this point, you should start by determining the special features that you require. When designing in a special (custom) cylinder, try to start with the particular family of cylinders, i.e., N.F.P.A. Interchangeable, Compact, Non-repairable, etc. that will be conducive to your application. If the application has plenty of room available and is very heavy duty, you may wish to start with an N.F.P.A. style cylinder. If real-estate is at a premium, you may want to start with a Compact type cylinder. When price is the main concern, a Non-repairable unit may become the first choice. Remember that you have several choices. Once you have determined the style of cylinder, you can then move on to the details of the design.

The next issue to address is the mounting. You should know at this point how you plan to mount the unit, but often times you have realized that it will require a mounting pattern or style that is non-standard. Therefore, you must determine how the style of cylinder that you have selected can be modified to fit. This may cause special manufactured mounting hardware such as special plates, flanges, or brackets to be produced. On units where the mount is made onto the cylinders, such as nose mounts or lugs, keep in mind that complete end caps will need to be produced which will add cost and time to be manufactured.

Then, you need to address the motion elements of the cylinder. Are there special movements, sensing, or side loads being applied that need to have special modifications to cylinder to try to accommodate these items? Multi-power, back-to-back, or multi-position cylinders may be required for the movements. Stroke adjust styles may also be needed when the stroke can change either on the extension or the retraction of the unit.
Sensing can often change the cylinder based on the type of sensing needed. Standard electronic switching will require magnets to be added. Proximity switching may cause internal or external changes to the cylinder so that the probes will have targets in which to read. Transducers may cause a variety of internal or external changes to a unit. Side loads often suggest a need for items such as stop tubes or heavier bushings because of the wear produced when the cylinder is in motion.

The final issue to address is the environment. Address the external issues and then address the internal issues. The external issues are items that will cause harm to the outside of the cylinder. Certain “wash down” or wet environments often cause material changes to the normal construction of the cylinder. Stainless steels, certain types of plastics, and chemical processes may need to be used on the products in order for them to withstand the environment. Heat may be another external issue that may cause a change to steel materials. The internal issues address items that may be used or may enter into the cylinder. If types of fluids are required to run the cylinder, then seal changes may be needed. When aggressive items are trying to enter into the unit, rod wipers or scrapers may be need. External chemicals may affect the internal components as well. Seal materials may also need to change.

Special cylinder applications can be very complicated, but by providing your cylinder manufacturer with the answers to these items when contacting them, this will greatly help them to provide the correct product to fit your cylinder needs. Keep in mind that each deviation from the standard product may cause special parts to be manufactured, purchased, and designed. When you are looking at your next design project, we would suggest that you try to fit it into a standard product if at all possible. The fewer parts that have to change, the less likely the cost will dramatically increase. However, when a total custom cylinder is required, you will need to plan on a longer lead time because these items will be designed to your specific needs. Good luck with all your future custom air cylinder applications.

Air Cylinders Direct is please to offer the EC Series Swing Clamps. Our pneumatic swing clamp combines linear and rotary motions. A specially machined spline internal to the piston rod develops the combined motions. When the clamp is pressurized to extend, it moves linear, removing the clamp tooling from the clamped surface as not to damage the clamped surface. After completing the linear travel, rotation occurs swinging the clamp arm away from the work holding area. During clamping the opposite motions occur.