Choosing the right air cylinder for your industrial application can be daunting given the vast array of options. This guide provides a clear, step-by-step approach to ensure you select the optimal cylinder for your needs.
**1. Determine Required Force:**
Begin by calculating the force needed to move your object. Accurately assess the object’s weight and factor in friction from sliding surfaces. Increase the calculated force by 25% to account for internal cylinder friction (rod and piston seals) and provide a safety margin for load variations.
**2. Calculate Cylinder Bore Size:**
Knowing your available air pressure (e.g., 90 PSI), multiply it by the piston’s surface area to determine the cylinder’s theoretical output force. Calculate the piston area using the formula: 3.14 x (radius in inches)^2. If the calculation doesn’t match a standard cylinder bore size, always select the next larger standard size. Note: The external cylinder dimensions don’t always correlate with the internal piston diameter.
**3. Determine Stroke Length:**
The required stroke length should ideally match the distance you need to move the object. However, consider the object’s size to prevent it from impacting the cylinder rod cap upon retraction. Using a slightly longer stroke allows the object to stop the piston’s movement before it bottoms out, potentially extending cylinder life, especially at high cycle speeds.
**4. Account for Connections:**
Factor in the dimensions of any connecting elements, like clevises, when determining the necessary stroke length. Remember, the rod can only move the distance the piston travels within the cylinder.
**5. Choose a Rod Connection Method:**
Directly screwing the object onto the rod thread requires careful alignment. Rod clevises offer more flexibility, accommodating slight misalignments. For significant misalignment, consider commercially available alignment couplers or external rod setups to minimize side-load on the cylinder rod.
Standard rod thread sizes vary depending on the cylinder bore size. Rod modifications, such as reduced thread sizes, different thread types (female), or replaceable studs, can enhance durability and reduce downtime.
**6. Select Cylinder Mounting Style:**
Cylinders offer diverse mounting options, including rod-cap threads, rear-cap threads, rear tangs for clevis mounts, threaded holes, flanges, and trunnion mounts. The optimal mount depends on the cylinder type and application.
Ensure the load is aligned with the rod travel to prevent issues. The load’s characteristics and location will influence the best cylinder mount.
**7. Choose the Cylinder Type:**
Consider these factors:
* Repairable vs. non-repairable (“throw-away”) cylinders
* NFPA (North American) vs. ISO (European) standards
* Construction materials: aluminum, steel, stainless steel, composite
* Rod materials: steel, stainless steel, chromed
Larger bore cylinders are usually repairable due to the higher initial investment. Select materials and seals based on the operating environment, considering factors like corrosion, and extreme temperatures.
**Additional Considerations:**
* **Cushions:** Use cushion vents to decelerate the piston at the end of the stroke, minimizing impact and extending cylinder life.
* **Position Sensing:** If position feedback is required, choose cylinders with magnets on the piston and external mounting options for proximity sensors (reed switches, Hall effect sensors, linear potentiometers). Alternatively, use external sensors to detect the load’s position.
By following these seven steps, you’ll be well-equipped to select the right air cylinder for your specific application.