RU118240U1 - TOOL ELECTRODE FOR MANUFACTURING DIFFICULT PROFILE SMALL-DIMENSIONAL INTERNAL SURFACES OF ROTATION BODIES - Google Patents

Abstract

An electrode-tool for making threads on the inner surface of bodies of revolution, made in the form of a rod, on the cylindrical surface of which channels are made in the form of a helical line, characterized in that graphite or copper alloy is used as the electrode material, while the length of the electrode is at least two distances of the thread depth, and the profile and geometric dimensions of the working part of the electrode-tool are an equidistant display of the profile of the cavity of the part with dimensions, reduced by the value, of the interelectrode gap within 0.04-0.06 mm.

Description

The field of technology. The utility model relates to the field of engineering, where there is a large range of parts belonging to the class of small-sized, with high precision manufacturing of internal complex surfaces. This utility model is used for the manufacture of parts of bodies of revolution for small-sized and precision control and measuring and metalworking equipment by the method of processing materials with concentrated energy flows.

The level of technology. Known prefabricated electrode tool for electrical discharge machining through holes of predominantly rectangular cross-section, not perpendicular to the surface of the part, includes a holder in which a set of plates are provided that are rigidly fixed with the number of elementary electrodes specified for each specific perforation in the lower part. The cross section of the elementary electrode is made in accordance with the profile of the hole being processed (see RF patent for the invention No. 2241581 C2, B23H 1/04, B23H 9/14).

The disadvantage of this device is the design complexity.

An electrode tool is also known, made in the form of a rod with a working end surface, channels for the electrolyte are made in the form of a helix on a cylindrical surface. The channels are spherical in shape (see United States Patent for Invention No. 4,698,543).

The known device does not satisfy the geometrical parameters of the workpieces described in the section "Technical Field", and the helical groove serves only to drain the sludge and improve the washing conditions, the electrode also has equal diameters of the shank and the working part. It is taken as a prototype.

Disclosure of a utility model.

The objective of the utility model is to simplify the basing of the tool with increased accuracy and reduce the accumulated error in the manufacture of complex small-sized parts.

This is achieved due to the fact that the electrode-tool for making threads on the inner surface of bodies of revolution is made in the form of a rod with a working cylindrical surface on which channels are made in the form of a helix. Graphite or a copper alloy is used as the electrode material, while the length of the electrode is not less than two distances of the thread depth, and the profile and geometric dimensions of the working part of the electrode-tool are an equidistant display of the cavity profile of the part with dimensions reduced by an interelectrode gap of 0, 04-0.06 mm, depending on the nature of the treatment (rough, finishing) and the value of the specified roughness of the resulting surface due to the coefficient k and the numerical value Ra = 0.1.

A brief description of the drawings.

Figure 1 schematically shows a sectional drawing of the forming surface of a representative part; figure 2 - diagram of the operation of the EDM firmware indicating the required length of the working part of the electrode-tool (1) and the nominal length of the workpiece (2);

figure 3 - photorealistic image of the finished electrode-tool, obtained using the computer-aided design.

Implementation of a utility model.

The device consists of a hard graphite (or consisting of a copper alloy) cylinder (3) with a screw profile (4) that repeats the profile of the inner surface of the workpiece with understating the nominal size B calculated by formula (1) for the interelectrode gap calculated by formula (2) .

where A is the size of the workpiece element according to the drawing; δ is the interelectrode gap; Z _min - the minimum allowance for subsequent processing. The plus sign is taken when processing the outer surfaces, the minus sign is for the inside.

where k is a coefficient taking into account the combination of the material of the electrode tool and the workpiece; I _cp - average current strength, A .; f is the frequency, Hz; q - duty cycle; U _xx is the amplitude open circuit voltage, V; j is the current density, A / cm ² ); h is the length of the vertical path of the removal of sludge, mm

The numerical values of the coefficients and the necessary parameters for calculating the interelectrode gap are determined based on the specified accuracy parameters and physico-chemical properties of the materials of the part and tool.

After carrying out these calculations, the optimal range of the interelectrode gap was determined to be 0.04-0.06 mm, depending on the nature of the processing (roughing, finishing) and the value of the given surface roughness due to the coefficient k and the numerical value Ra = 0.1. If this range of interelectrode gap values is exceeded or underestimated, the geometric dimensions of the electrode and roughness parameters are violated.

The criteria for the selection of materials for the electrode-tool are the ease of their machining and high electrical conductivity with low wear of the working surface. Data on the relative wear of the electrode depending on the material are shown in table 1.

Table 1 The relative wear of some materials depending on the operating current Tool Electrode Material Relative wear% I _cp , A twenty 40 60 80 one hundred Red copper 10 12 13 fourteen fifteen Aluminum alloy AL5 27 twenty 19 17 16 Aluminum alloy D1 40 23 twenty 16 fourteen Gray cast iron 12 fourteen fifteen 16 17 Graphitized EEG Material 1,0 1,5 1.7 1,5 1,0

Based on the results obtained and the data of Table 1, graphite and a copper alloy were chosen as the material for the manufacture of the electrode-tool. Graphite is well machined. The properties and structure of this material make it possible to manufacture products of complex shapes, with small tolerances and with high accuracy. The combination of such a number of positive properties in one material predetermined its widespread use for the manufacture of electrode electrodes.

This model is manufactured at a turning machining center using a control program created by computer-aided design.

The device operates as follows. Processing with this electrode (1) is performed on an EDM machine with numerical control in a working fluid medium by rotationally translational movement in a spiral (4) to a depth equal to two lengths of the workpiece (2).

The device can also perform roughing and finishing in one operation without changing the technological base, which significantly increases the accuracy of manufacture and surface roughness corresponding to Ra = 0.05-0.06 μm.

This device has a simple design, reliable in operation and provides the formation of a unique physico-chemical state of the material in the surface layer, as well as achieving high environmental cleanliness of production.

Claims (1)

An electrode-tool for making threads on the inner surface of bodies of revolution, made in the form of a rod, on the cylindrical surface of which channels are made in the form of a helix, characterized in that graphite or a copper alloy is used as the electrode material, while the electrode length is at least two the distance of the thread depth, and the profile and geometric dimensions of the working part of the electrode-tool are equidistant display of the cavity profile of the part with dimensions reduced by the value of the interelectron a gap between 0.04-0.06 mm.