Hydraulic Applications – Clamping Fixture

In this article, we’ll cover a hydraulic clamping fixture as an example hydraulic system application. We’ll identify the hydraulic circuit components of the example system and build its hydraulic circuit diagram.

Clamping Fixture Hydraulic Application

Workpieces are to be clamped using a hydraulic cylinder. To prevent damage to the workpieces in question, the speed during the gripping and clamping operation needs to be slowed down. On the other hand, the speed at which the part is released will remain unchanged.

The hydraulic control system for the clamping fixture can be completed with a single one-way flow control valve for speed control.

A one-way flow control valve is formed by combining a flow control valve with a one-way shut-off valve. The flow control valve controls hydraulic fluid in the flow direction from A to B. Since the control action takes the form of narrowing the flow cross-section, it acts as a resistance and causes pressure to rise at port A. This rising pressure, together with the pressure-relief valve, causes the flow to be split. Due to this split, the flow rate in the line feeding the actuator is reduced, and consequently so is the actuator’s speed.

In adjustable one-way flow control valves, the control cross-section can be narrowed or widened depending on the situation.

One-Way Flow Control Valve

Flow control valves can be positioned to act on either the inlet or outlet of the cylinder.

Flow Control on the Supply Line

If pressure drops at the flow control point, part of the pressure energy is converted into heat, and this heat is transferred to the fluid and the actuator.

Flow Control on the Return Line

For the pressure-relief valve to open and split the flow, pressure on the piston face side must reach at least 240 bar. Because the ratio between the surface areas is 2:1, the pressure between the flow control valve and the cylinder reaches 480 bar. This pressure decreases in proportion to the friction between the cylinder and the piston, and to the external force acting on the piston rod. The hydraulic fluid, heated at the flow control point, is returned to the tank.

In this article, in the Machine Elements – Hydraulic Pneumatics section, we covered an example application using hydraulic circuit components such as a pressure-relief valve, a flow control valve, and a 2-way 2-position directional control valve. See you in our next articles.