Hydraulic Clamping Fundamentals


document, the term system shall indicate all of the hydraulic components (sort of like a finished printed document) of an installation as physically implemented, or planned. Force can be described as the amount of push or pull between two objects. In power clamping applications in the U.S., this force is typically designated as pounds (lbs) and is achieved by applying pressure to an actuator. Pressure is the resistance to flow of a liquid, and is in part responsible for creating the force in a hydraulic system. In power clamping applications, it is designated as pounds per square inch (psi). As water runs out of an unrestricted hose, it flows at zero pressure (no resistance, ignoring line losses). When you place your hand in front of this hose, you will feel the force of the water. This force is derived from pressure created by the resistance of your hand to the flow. As you move your hand closer to the end of the hose, the resistance increases, as does the pressure, which results in an increased force on your hand. Actuator is a device that uses the hydraulic pres- sure to achieve mechanical movement, or perform work. In work holding, this is generally in the form of an applied force. Actuators are typically broken down into two different types, linear and rotary. For power clamping applications, the primary focus is on linear actuators. Fluid velocity is the average speed of the fluid flowing past a given point in a specified amount of time. In power clamping applications, velocity is typically designated as feet per second (fps).

Hydraulic actuators provide a consistent, repeatable force in a relatively small weight and size envelope. This means that in today’s manufacturing environment, the work piece can be secured, in less time, with more accuracy and repeatability without sacrificing valuable fixture space. This is especially true in systems that operate above 2500 psi, to take an advantage of the increased force generated from a smaller component operating at higher pressure. Hydraulic power clamping also provides the manufacturer with flexibility in holding forces and actuator functions to optimize the design for machine operations as well as process functionality (loading/unloading).


Hydraulics is a science that deals with the laws governing liquids in motion. Specifically addressed in this document is the use of liquid hydraulic oil in motion and at rest in a system to transmit or generate force for hydraulic clamping applications. Circuit is the routing and control of a confined liquid to apply power. This power is used to achieve a specific function resulting in work being performed. For the discussions in this document, the term circuit shall be intended to indicate the planned functional components (sort of like a document outline) as represented in a schematic drawing. System is often synonymous with a circuit, but for discussion, should be additionally defined as the components as they are physically implementedinto a working application or circuit. This will include the actuators, fittings, manifolds, hose and tubing routing and length of run, as well as mounting styles of various devices. For the purpose of discussion in this

Flow rate is the measurement of a volume of fluid flowing past a given point in a specific

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