MAINTAINING THE ACCURACY OF CONTROL PARAMETER VALUES ELECTRO-HYDRAULIC LOAD DURING STAMPING WITH SPATIO-TEMPORAL CONTROL

Abstract

The article is devoted to ensuring the stability of the technological process of electrohydraulic stamping of thin-sheet large-sized parts. This process is realised on multi-contour EH presses equipped with the capabilities of space-time control of the workpiece load. This control ensures the production of high-quality parts and high technical and economic performance of the process.

The control parameters include the geometry of the press energy release zone, the loading sequence of the workpiece sections and the value of the inter-electrode distance. The first parameters change little under specified operating conditions. The third parameter is subject to change over a specified number of discharges due to cavitation and EDM erosion. Violation of the specified value of the interelectrode distance leads to a violation of the energy release mode and its loss.

As a result of the experiments, the mechanism of cavitation destruction of the high-voltage insulation of the working electrode was determined and a solution was proposed for the conditions of winding the high-voltage insulation with a glass fibre roving, as well as electrical insulation in the areas adjacent to the discharge zone.

Several variants of the design of the end part of the working electrode, which is still directly in the EG discharge zone, were experimentally investigated.

The ratio of the duration of the pre-discharge stage to the characteristic time of the discharge circuit was chosen as a criterion parameter of resistance to electrical erosion of the discharge edges. The duration of the pre-discharge stage was determined from the discharge voltage oscillograms.

According to the given dependences of the above ratio on the number of discharges, the best design from the considered options was determined.

The used value of this ratio for the selected design corresponds to  ~ 2500 discharges at a voltage of 20...25 kV. This number of discharges is on average comparable to the operation during five shifts, after which it is necessary to restore the discharge edges of the electrode. To simplify the operations of changing electrodes, we propose a design in which the electrodes are fixed by clamping them with elastic washers.

It is concluded that the goal has been achieved: maintaining stable operation of the EG press with high technical and economic indicators of the entire technological process at a given quality of parts manufacturing.

It is concluded that the goal has been achieved: maintaining stable operation of the EG press with high technical and economic indicators of the entire technological process at a given quality of parts manufacturing.

Objective of the work - is to evaluate the effectiveness of the proposed technical solutions to increase the stability of the working electrodes and simplify their repair and restoration.