Development of a Hydraulic Actuator to Superimpose Oscillation in Metal-Forming Presses

Abstract

A novel principle of a rotary piston valve and a high-frequency cylinder for a hydraulic actuation system are presented. This system will be utilized in metal-forming presses to superimpose a high-frequency oscillation on the movement of the ram. This technique was proven to enhance the forming parts quality, to extend the process limits and to reduce the forming force significantly. The key components of the valve are a stator and a rotary piston with radial drilled holes that is designed to provide a pulsating pressure and mass flow rate at a high frequency. A hydraulic cylinder is connected to the valve and converts the pulsating flow into a dynamic process force. The valve and the cylinder will be mounted on the bolster plate of a metal-forming press. In order to superimpose oscillation in the main forming direction, the cylinder is centered under the punch of the metal-forming tool. Three-dimensional computational fluid dynamics (CFD) simulations have been conducted to evaluate and to optimize the designs of the main components of the system. Hereby the commercial simulation code of ANSYS CFX was employed to determine the properties of the cylinder and the valve. Through its mesh motion technique, this simulation code allows the flow analysis between the rotary and the stationary part of the valve. Furthermore the dynamic characteristics of the system have been investigated under the influence of inertia and the compressibility of oil.

Influence of Superimposing of Oscillation on Sheet-Bulk Metal Forming

“…The maximum frequency decreases with increasing flow rates of the valves. The rotary piston valve has another functional principle which allows realizing high flow rates at a high frequency [9]. By adopting the rotation principle the frequency of the pulsation is therefore depending on the angular velocity of the rotor.…”

“…Due to the rotation of the rotor the main pressure room is connected to the tank so that the cylinder piston will be pushed to move down. At this time the lower room is connected to the hydraulic pump in order to provide a damping for the piston and accordingly to avoid the impact of the piston against the cylinder casing [9].…”

New Multistage Sheet-Bulk Metal Forming Process Using Oscillating Tools

“…This tool system consists of two main components: a plane strain compression tool and a hydraulic oscillation unit. The hydraulic oscillation unit developed by Behrens et al is able to realise an excitation frequency spectrum between 0 and 600 Hz at excitation amplitudes of 10-50 µm [14]. The displacement stroke of the sheet specimen can be measured by a laser-displacement sensor.…”

“…The hydraulic oscillation unit developed by BEHRENS ET AL. is able to realise an excitation frequency spectrum between 0 and 600 Hz at excitation amplitudes of 10-50 µm [14]. The displacement stroke of the sheet specimen can be measured by a laser-displacement sensor.…”

Numerical and Experimental Investigations of Multistage Sheet-Bulk Metal Forming Process with Compound Press Tools

“…In the last stage of the process sequence, the component part is sized. To improve the part accuracy and to reduce the forming force, the dynamic forces are generated by using a hydraulic oscillation system [6]. The major challenges for the process and the tool design are: the combination of the several processes in one stage and the superimposed oscillation of the whole process sequence.…”