Overview

Designing equipment that requires presses, lifts, and mobile machinery presents an equal challenge for OEM manufacturers. First, they need to design a cylinder that moves loads in both directions with precise control. Herein, a two-port design has proven its worth, as it drives motion in both directions by using positive control rather than waiting for the force of gravity to act upon springs or an external load to bring the mass back to its start position.

How Fluid Flow Controls Both Strokes

Fluid flow control cylinders are designed with two ports, one located at each end of the cylinder. In the extend stroke, fluid is pressurized and flows into one port. The other side, in the drain position, flows back to the reservoir. This function is reversed for the retract stroke, which pushes fluid into the port via the control valve. Since both directions of motion are controlled, the load is under predictable control at all times, and is therefore ideal for equipment that moves heavy parts without losing precision.

Differentiating Elements by Performance

The smooth travel of a piston over its lifespan can be attributed to the quality of the cylinder tube. A tube that is honed and cold drawn ensures a consistent bore surface minimizes seal wear from the piston cycling thousands of times. A rod is made from high grade steel with chrome plating that resists both corrosion and scoring. A gland fitted with sealing rings and wear rings keeps pressurized fluid contained at the rod end and facilitates linear movement. The piston is generally machined from a high grade steel with grooves to hold sealing rings on both sides to minimize bypass leakage. The design of the mounting structure is equally important. Of the various designs (clevis ends, tie-rod, flange), each addresses different loads and constraints in the machine’s overall layout. For example, a ductile iron clevis adequately addresses the connection of equipment that is pivoted under a load. A flange mount provides a rigid connection for a fixed attachment.

Sizing for the Application
Sizing requirements for bore, rod diameter, and stroke length intersect with an application’s force and speed needs. A larger bore means a higher force potential at the expense of requiring more fluid and creating longer cycle times due to pump size. Increasing rod diameter means a stronger resistance to buckling due to the compressive forces needed to actuate the cylinder in a stroke. In makins especially stroke lengths should have a little extra to accommodate clearances and to include safety factors for wear during service. Wall thickness is also related to the operating pressure of the system as the material selection should be such that the failure of the cylinder due to pressure will not occur before the expected life of the equipment. The most cost effective solution for the equipment is to get the design right and avoid reworking the cylinder.

Common Applications Across Industry

Controlled force in both directions dictates the use of this cylinder type. Presses use them to apply and retract the stroke. These also help lift equipment and material handling equipment in stabilizing a load in a controlled way. Tilting, steering and boom control systems on mobile machinery also rely on these designs.

Working with an Experienced Manufacturer

Using a catalog with specifications to source tube, rod, gland, and mounting components does not guarantee success. Precision in manufacturing tubes requires experience that Teutonic Engineering of Coimbatore, India, possesses. They manufacture tie-rod cylinders made from hard chrome plated rods and precision threaded glands with wear rings using cold drawn and honed tubes for industrial and mobile machine applications. Cylinder component quality along with application comprehension by the supplier enables OEM manufacturers to circumvent the time consuming trails running the gauntlet of unfamiliar cylinders’ suppliers.

Final Thoughts

Getting cylinder component details, dimensions, and mounting specifications correct during design ultimately pays dividends by eliminating unnecessary expense caused by premature wear. For OEM manufacturers and designers of presses, lifts, and mobile machines, a double acting hydraulic cylinder is a practical choice as it provides a powered and controlled force in both directions of motion.