RU2023552C1 - Electrochemical hole size working method - Google Patents

Abstract

FIELD: punching of holes in thin-sheet parts. SUBSTANCE: method involves applying stencils to both sides of workpiece surfaces adapted for working by means of electrode-type tools; upon the moment workpiece is subjected to through punching, working of workpiece is continued for time period defined by expression, given in discription of invention. EFFECT: increased efficiency and high quality of working. 3 dwg

Description

 The invention relates to dimensional electrochemical processing and can be used to obtain through holes in thin-walled parts.

 A known method of electrochemical perforation of holes in thin-walled blanks, performed by stationary electrode-tools with the placement of the workpiece between two stencils, while pumping the electrolyte in each interelectrode channel is carried out in opposite directions. But this cannot exclude protrusions on the lateral surfaces of the stitched holes, moreover, it is difficult to do, since additional devices are needed to supply electrolyte to each interelectrode channel.

 The closest technical solution is the method of electrochemical perforation of holes in thin-walled blanks, carried out by stationary electrodes-tools with the placement of the workpiece between two stencils.

 However, with this method, protrusions remain on the side surface of the hole, i.e. there is a significant error in the linear size of the hole.

 The objective of the proposed method is to increase the accuracy of processing, i.e. getting holes with a flat side surface.

ln

, где К = 0,23...0,95 мм²/мин - характеристика режима ЭХО и обрабатываемого материала; h_з - толщина обрабатываемой заготовки; а_з - начальный межэлектродный зазор;Δ_x- погрешность линейного размера отверстия.This is achieved by the fact that in the known method of electrochemical perforation of holes in thin-walled blanks, in which the processing is carried out by electrode-tools with overlapping on both sides of the workpiece surface of the stencil blanks, the processing is carried out until the holes are pierced through and then continue for a period of time determined by the expression :
t _d = 0.27

ln

where K = 0.23 ... 0.95 mm ² / min is a characteristic of the ECHO mode and the processed material; h _s - the thickness of the workpiece; and _s is the initial interelectrode gap; Δ _x is the error of the linear size of the hole.

 This allows you to reduce the height of the protrusion on the side surface of the hole due to the concentration of the electric field and increase the rate of removal of metal at the top of the protrusion compared to the more gentle parts of the side surface of the hole. Over time, there is a uniform distribution of the rate of anodic dissolution of the metal along the entire side surface of the hole being machined.

 Figure 1 shows a schematic diagram of a device for dimensional electrochemical perforation of holes; in FIG. 2 - boundaries of the hole being machined at various points in time; figure 3 - dependence of the error of the linear size - the diameter of the hole on the processing time.

 The device has an upper 1 and lower 2 chambers for collecting electrolyte, which are connected through the input channels 3 and 4 for electrolyte in the cathodes 5 with interelectrode gaps 6 and 7. On the workpiece 8, which serves as the anode, are placed on both sides of the stencil 9 with holes 10 round forms. The current lead 11 and the cathode 5 are separated from each other by dielectric spacers 12 and output channels 13 for the electrolyte.

Prior to starting the electrochemical installation, the through hole piercing time t _pr in a thin-walled workpiece and the further processing time of the holes t _{d are} determined. Since the parameters a _o , k, h _s , Δ _x are given, then the time t _pr and t _d and the total processing time t = t _pr + t _d can be calculated on any microcalculator.

 When the device is operating, the electrolyte is supplied to chambers 1 and 2 and through channels 3 and 4 enters the interelectrode spaces 6 and 7. With the inclusion of a current source between the anode 8 and the cathodes 5, a difference in electric potentials is created. In this regard, in areas of the treated surface that are not protected by stencils 9, continuous electrochemical dissolution occurs. The electrolyte with dissolution products is removed through the outlet channels 13 into the electrolyte collection system.

Starting from the moment the device is connected to the current source, the through-hole piercing time t _pr in a thin-walled workpiece and the further processing time of the holes t _{d are} monitored using a stopwatch.

Electrochemical perforation of holes in a sheet of steel 12Kh18N10T with a thickness of _hz = 1 mm was performed for the following mode: voltage 14 V, initial interelectrode gap a _о = 1 mm, pressure at the inlet to the electrolyte feed chambers - 0.2 MPa, electrolyte - 20% aqueous solution of NaNO ₃ at 20 ^° C stencils made from PCB PTC GOST 5-78 0.2 mm thick, had a hole diameter of 2 mm.

, где для заданного режима k = 0,34 мм²/мин составило 1,84 мин.Through hole flashing time calculated by the formula
_ave t = 0,5h

where for a given mode, k = 0.34 mm ² / min was 1.84 min.

In practice, hole punching is always performed with a certain diameter error Δ _d = Δ _x , which is defined as half the difference between the hole diameters on the sheet blank under the stencil and at the point of maximum protrusion on the side surface.

ln

составило 0,55 мин.After a through hole flashing, the time of additional processing in order to obtain a hole with a diameter error Δ _d = 0.25 mm, calculated by the expression
t _d = 0.27

ln

amounted to 0.55 minutes

The total time of the electrochemical hole piercing was
t = t _ol + t _d = 2.39 min.

Starting from the moment of through hole flashing, at certain intervals, the diameter of the hole was measured using an MMI-2 instrumental microscope (certified error of 0.005 mm). The boundaries of the hole to be processed at different points in time t _d (Fig. 2) (1-t _d = 0.2 - 0.55 min, 3 - 1.01 min, 4 - 1.83 min) show that the continuation of processing after the moment flashing holes leads to alignment of the side surface of the hole. In this case, the error in the diameter of the hole Δ _d (Fig. 3) at the time of piercing the hole t _pr is 0.5 mm and decreases during processing. Thus, the application of the proposed method increased the accuracy of the processing in Δ _d (t _ol ) / Δ _d (t _d ) = 0.5 mm / 0.25 mm = 2 times.

Claims (1)

METHOD FOR DIMENSIONAL ELECTROCHEMICAL HANDLING OF HOLES in thin-walled workpieces, in which the workpiece is placed between two stencils, and the processing process is carried out by electrodes-tools simultaneously from two sides with pumping of the electrolyte, characterized in that when the time of through hole piercing is reached, the processing continues for a time determined according to the formula
t _d = 0.27

ln

,
where K = 0.23 - 0.95 mm ² / min;
h _s - the thickness of the workpiece;
a ₀ is the initial interelectrode gap;
Δd is the error of the diameter of the hole.

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