CN109967805B

CN109967805B - Tool cathode for electrochemical discharge mechanical milling composite machining and use method

Info

Publication number: CN109967805B
Application number: CN201910274296.9A
Authority: CN
Inventors: 曲宁松; 岳小康; 李寒松
Original assignee: Nanjing University of Aeronautics and Astronautics
Current assignee: Nanjing University of Aeronautics and Astronautics
Priority date: 2019-04-08
Filing date: 2019-04-08
Publication date: 2020-07-28
Anticipated expiration: 2039-04-08
Also published as: CN109967805A

Abstract

The invention relates to a tool cathode for electrochemical discharge mechanical milling composite machining and a using method thereof, belonging to the field of electrolytic electric spark mechanical composite machining. The cathode material of the tool is copper-tungsten alloy, the workpiece is a conductive material, the electrolyte is a salt solution with higher conductivity, a common direct-current power supply is adopted for supplying power, and an insulating blade is welded at the bottom of the cutter. During machining, electrolyte enters a machining area from the side wall of the tool cathode, electrochemical anodic dissolution of workpiece materials is achieved, meanwhile, a discharge channel is formed between the tool cathode and a workpiece in a small machining gap, and the rotation of the tool cathode achieves transfer of a discharge point, so that the electrolysis effect and the electric spark effect are combined to remove materials, the material removal rate is remarkably improved, and due to the milling effect of the blade at the bottom of the cutter, the machined bottom surface can be leveled, and the flatness of the machined bottom surface is improved. The cutter provided by the invention can realize high-efficiency and high-precision processing of metal materials difficult to process.

Description

Tool cathode for electrochemical discharge mechanical milling composite machining and use method

Technical Field

The invention relates to a tool cathode for electrochemical discharge mechanical milling composite machining and a using method thereof, belonging to the field of electrolytic electric spark mechanical milling composite machining.

Background

With the development of science and technology, parts prepared from difficult-to-cut materials such as titanium alloy, high-temperature alloy and the like are increasingly applied to the fields of aerospace and the like. For example, wings, center wings, fuselage skins and the like of C919 airplanes are all made of titanium alloy materials, and GH4169 materials account for 34%, 56% and 57% of the total weight of CF6 engines, CY2000 engines and PW4000 engines respectively. However, when the traditional machining method is adopted to machine the materials which are difficult to machine, the problems of large cutting force, serious tool abrasion and the like exist, the machining cost is high, the efficiency is low, and the further application of the materials in the aerospace field is limited.

The electrochemical machining is based on electrochemical anode dissolution principle to remove materials, belongs to non-contact machining, and removes workpiece materials in an ion mode during machining, so that the electrochemical machining has the advantages of no limitation of physical properties such as material strength, hardness and the like, high machining efficiency and no cutter loss. However, due to the characteristics of non-contact machining, the machining precision is not high, and especially when the electric quantity distribution in the machining area is not uniform, the flatness of the machined workpiece is poor. Arc discharge machining, which is a machining method developed for meeting the requirements of high efficiency and low cost of difficult-to-machine materials, melts or vaporizes a workpiece material by using high temperature generated by electric discharge, and rapidly discharges a product out of a machining gap under the scouring of a high-speed flowing electrolyte, is not limited by material hardness and the like, and has high energy utilization rate. Electrochemical discharge machining is a composite machining process combining electrolysis and discharge machining, compared with single electrolysis machining or discharge machining, machining efficiency can be improved by more than 5 times, the electrolysis can solve the problem of poor machining surface quality caused by discharge machining, and the precision of electrochemical discharge machining is reduced due to the electrolysis.

Grinding is one of the common finishing means, and may be combined with electrochemical machining, arc discharge machining, electrochemical discharge machining, etc. to improve the quality of the machined surface and improve the machining accuracy. Patent CN102398193A discloses a grinding-assisted electrochemical discharge machining tool and method, but the electrolytic action is only used to generate hydrogen bubbles to assist the electric discharge machining, and the machining gap is small, so that the exposed height of the abrasive grains is larger than the machining gap, and the grinding action can be fully exerted. In patent CN87106421A, an electric discharge machine grinding combined machining method and apparatus is disclosed, which uses the relative rotation motion of the tool and the workpiece to realize the forced mechanical motion arc breaking of the electric discharge arc, so as to realize the high-efficiency and stable arc discharge machining, but the finish machining of the grinding wheel is completed in the power-off state, which is not synchronous with the electric discharge machining, and the tool wear of the finish machining is increased. Patent CN107649755A discloses a high-speed arc discharge grinding combined machining method, which utilizes the inter-pulse period of pulse current to exert the grinding effect of abrasive grains to improve the quality of the machined surface. In patent CN105921834A, an electrolytic milling tool cathode is disclosed, which uses a bottom conductive ring to improve the flatness of the bottom surface, and in patent CN108393547A, a tool cathode is disclosed, which uses an insulating abrasive layer on the bottom surface to improve the flatness, but when an electric discharge machining mechanism is introduced, the instantaneous high temperature is likely to make these insulating layers fall off and fail.

For pure arc discharge machining, in order to maintain the generation of an arc, the machining gap is small, and abrasive grains can well grind a workpiece, but when electrolysis is involved, if the machining gap between the workpiece and a tool cathode is increased to exceed the exposure height of the abrasive grains, the abrasive grains cannot grind the workpiece, and the grinding effect is failed. And when the tool and the workpiece rotate relatively, a common direct current power supply can be adopted to replace a pulse power supply, the continuous electrolysis and arc discharge are beneficial to further improving the efficiency, but the machining gap is enlarged, and the abrasive particles can not play a role. Therefore, how to realize the electrochemical discharge machining and simultaneously level the machined bottom surface, improve the flatness of the machined bottom surface and improve the surface quality has important significance for promoting the further application of the electrochemical discharge machining.

Disclosure of Invention

The invention aims to provide a tool cathode for electrochemical discharge mechanical milling composite machining and a using method thereof, wherein the tool cathode adopts copper-tungsten alloy with high melting point as a tool cathode, salt solution with higher conductivity is used as electrolyte, insulating blades with different heights are embedded on the bottom surface of a tool, the electrolysis, arc discharge and mechanical milling are combined, so that the high-efficiency machining of metal materials difficult to machine can be realized, the problems of poor flatness and poor surface quality of the machined bottom surface can be improved, and the tool wear is reduced.

The utility model provides an electrochemistry discharge machine milling composite machining tool negative pole which characterized in that: the cathode substrate is a circular electrode, and the center of the cathode substrate is provided with a blind hole from top to bottom; a plurality of rows of liquid outlet holes which are vertically distributed are arranged on the side wall of the lower end of the cathode substrate; a reinforcing boss is arranged on the upper surface of the bottom of the cathode substrate along the diameter direction; two ends of the reinforcing lug boss are respectively positioned between the two rows of liquid outlet holes; the bottom of the cathode base body corresponding to the reinforcing lug bosses is provided with a near chute and a deep chute, the lug bosses are additionally arranged in the cutter, so that the bottom can be grooved, the cutter can be used for subsequent blade embedding, and the lug bosses are positioned between the liquid spraying holes, so that the situation that the lug bosses block electrolyte flowing into a machining gap can be avoided, and the machining efficiency is ensured; a first blade is embedded in the near chute, and a second blade is embedded in the far chute; the two chutes are same in shape and are both parallelogram, the shortest distance from the center of the near chute to the outer wall of the cathode substrate is smaller than the shortest distance from the center of the far chute to the outer wall of the cathode substrate, and the shortest distances from the centers of the two chutes to the outer wall surface of the cathode substrate are different, so that the exposed heights of the blades after being embedded are different, and the outer tool points of the blades are positioned on the extension line of the bus of the outer wall of the cathode substrate; the shapes of the first blade and the second blade are the same and are both parallelogram, the outer tool points of the embedded blades are all positioned on the extension line of the bus on the outer wall of the cathode matrix, and in order to enable the blades to be milled to an electrolytic machining area, the outer tool points of the blades need to be positioned on the extension line of the bus on the outer wall surface of the cathode matrix; above-mentioned first blade and second blade material are insulating material, and the exposure height of first blade is less than the exposure height of second blade, and the blade is insulating avoids blade and work piece positive pole direct contact to cause the short circuit, sets for the not equidistance with the exposure height of two blades, can accomplish the material branch that needs strike off respectively by two blades, avoids the great cutter wearing and tearing in order to aggravate of single cutter depth of cut.

The tool cathode for electrochemical discharge mechanical milling composite machining is characterized in that: the cathode base material is copper-tungsten alloy. The copper-tungsten alloy has good electrical conductivity, can reduce the voltage drop on the cutter, improves the electrolytic effect, has good thermal conductivity and high melting point, can meet the requirements of electrochemical discharge machining, reduces the abrasion of the cutter, has high hardness and high strength, can bear the milling force generated by mechanical milling, and ensures the machining stability.

The use method of the tool cathode for electrochemical discharge mechanical milling composite machining is characterized by comprising the following steps: the method comprises the following steps: the tool cathode is arranged on a machine tool rotating shaft, the machine tool rotating shaft is connected with a power supply cathode, the workpiece is connected with a power supply anode, and the processing sequence of the first blade after tool setting is superior to that of the second blade according to the moving direction of the workpiece and the rotating direction of the tool cathode; step two: the electrolyte is sprayed into the machining gap from the liquid outlet hole, the power supply is switched on, the feeding speed is gradually increased, so that arc discharge is generated between the cathode matrix and the workpiece, and at the moment, the material is removed at a high speed under the action of the arc discharge and electrolysis; step three: under the electrolytic action, the machined bottom surface can form a concave structure, and under the successive milling action of the first blade and the second blade, the machined bottom surface can be leveled, so that the high-efficiency and high-precision machining of the conductive material workpiece is realized. The two blades are different in exposed height, so that materials needing fine milling can be removed twice, the loss of a cutter is reduced, and in order to achieve the purpose, the bottom surface of the blade with the small exposed height needs to be machined firstly; the electrolysis in the present invention is not only to generate hydrogen bubbles to promote arc discharge machining, but also to remove materials, and particularly, to improve a recast layer and a heat affected zone after arc discharge machining.

The use method of the tool cathode for electrochemical discharge mechanical milling composite machining is characterized in that: the outer diameter of the cathode matrix of the adopted tool cathode is 6mm-30 mm; the cutting depth of the cathode of the adopted tool is 2mm-50 mm; the electrolyte is sodium nitrate solution or sodium chloride solution. The bottom of the cathode of the tool is embedded with two blades with different heights, the outer diameter is set to be not less than 6mm so as to ensure the processing difficulty of the tool, and the unevenness of the bottom surface caused by the overlarge diameter is serious, so the outer diameter of the tool is preferably not more than 30 mm; setting the processing depth to be more than 2mm according to the bottom thickness of the tool, the size of the liquid spraying hole and the exposed height of the blade, and when the depth is more than 50mm, obviously increasing the required liquid supply pressure; the solution of sodium nitrate or sodium chloride has high conductivity, and can fully exert the electrolysis action to improve the material removal rate, which is different from the low-conductivity electrolyte commonly adopted in the prior electrochemical discharge machining.

The invention has the following advantages:

1. by adopting a common direct-current power supply, adopting electrolyte with higher conductivity and adopting copper-tungsten alloy with good heat conduction and heat conductivity and high melting point as a tool cathode material, the continuous electrolysis effect and arc discharge effect can be realized, and the material removal rate can be further improved.

2. The arc discharge effect in the invention is continuous, because the energy density is high, the generated recast layer and the heat affected zone are also larger, when the salt solution with lower conductivity is adopted, the recast layer and the heat affected zone remained after the electrolysis effect can still be larger, the cutter abrasion during milling is increased, and when the salt solution with higher conductivity is adopted, the electrolysis effect can be fully exerted to reduce the residues.

3. The electrolytic action is generated to gradually increase the machining clearance between the cathode of the tool and the workpiece, the conventional abrasive grain grinding has no effect, the blade design is adopted, the exposure height is greatly improved, the mechanical milling action can be fully exerted to remove the machined bottom surface material, and the machined bottom surface flatness and the surface quality are improved.

4. Because the flatness of the machined bottom surface after electrolysis is poor and the flatness is reduced along with the increase of the diameter of the cathode of the tool, when the blade is adopted for milling, the machining allowance is gradually increased to cause larger tool abrasion, and the machining allowances can be removed twice by adopting different exposure height designs, so that the tool abrasion is reduced.

5. The insulating blade is a common blade, does not need to be specially customized, can regulate and control the exposure height of the blade only by calculating the shortest distance from the centers of the two oblique rectangular grooves to the outer wall surface of the cathode substrate, and has the advantages of simple structure, low manufacturing cost and easy operation.

Drawings

FIG. 1 is a view showing the internal structure of a cathode for a tool according to the present invention;

FIG. 2 is a cross-sectional view of the tool cathode of FIG. 1;

fig. 3 is a schematic view of the electrochemical discharge mechanical milling composite machining of the tool cathode provided by the invention.

Wherein the label names are: 1. a cathode substrate; 2. a liquid outlet hole; 3. reinforcing the boss; 4. a near chute; 5. a far chute; 6. a first blade; 7. a second blade; 8. a workpiece; 9. a workpiece feed direction; 10. the direction of tool cathode rotation; 11. a power source; 12. the shortest distance from the center of the near chute to the outer wall of the cathode matrix; 13. the shortest distance from the center of the far chute to the outer wall of the cathode substrate.

Detailed description of the invention

The invention is further described below with reference to the accompanying drawings:

as shown in fig. 1-2, an electrochemical discharge mechanical milling composite machining tool cathode is characterized in that: the cathode comprises a cathode substrate 1, wherein the cathode substrate 1 is a circular electrode, and a blind hole is formed in the center of the cathode substrate from top to bottom; a plurality of rows of liquid outlet holes 2 which are vertically distributed are arranged on the side wall of the lower end of the cathode substrate 1; a reinforcing boss 3 is arranged on the upper surface of the bottom of the cathode substrate 1 along the diameter direction; the two ends of the reinforcing lug boss 3 are respectively positioned between the two rows of liquid outlet holes 2; a near chute 4 and a far chute 5 are arranged below the bottom of the cathode substrate 1 corresponding to the reinforcing lug boss 3; a first blade 6 is embedded in the near chute 4, and a second blade 7 is embedded in the far chute 5; the two chutes are same in shape and are both parallelogram, and the shortest distance from the center of the near chute 4 to the outer wall of the cathode substrate 1 is smaller than the shortest distance from the center of the far chute 5 to the outer wall of the cathode substrate 1; the blades are in the same shape and are in a parallelogram shape, and the outer tool tips of the embedded blades are all positioned on the extension line of the bus of the outer wall of the cathode substrate 1; the blade material is insulating material, and the exposed height of the first blade 6 is less than that of the second blade 7.

In order to improve the material removal rate of single feed, the cathode of the tool adopts an internal liquid spraying and supplying mode, the thickness of the bottom of the tool is generally less than 1mm, at the moment, the blade is difficult to be embedded at the bottom of the tool, and the blade can be embedded into a boss after the boss is additionally arranged inside the tool (as shown in figure 2); the liquid outlet holes 2 which are vertically distributed are adopted, so that a boss can be added between the adjacent liquid outlet holes without interfering the liquid outlet of the liquid outlet holes; in order to inlay the parallelogram-shaped blade, two inclined grooves are required to be arranged at the bottom of the cutter, and the shortest distances from the centers of the two inclined grooves to the outer wall surface of the cathode substrate are different, so that the inlaid blade can be exposed at different heights, and the outer tool point of the blade can be positioned on the extension line of a bus of the outer wall of the cathode substrate (as shown in fig. 2); in order to enable the blade to be milled to an electrolytic machining area, the outer blade point needs to be on a bus extension line of the outer wall surface of the cathode matrix, at the moment, if the blade is in a vertical shape, the side wall of the blade is embedded on the outer wall surface of the cathode matrix, the integrity of the outer wall of the cathode matrix is damaged, and the electrolytic machining efficiency is influenced, so that the outer blade point can be located on the bus extension line of the outer wall of the cathode matrix without influencing the machining efficiency by adopting a parallelogram structure; the blade is insulating to avoid blade and work piece positive pole direct contact to cause the short circuit, sets for the not equidistance with the exposure height of two blades, can accomplish the material branch that needs to strike off by two blades respectively, avoids single cutter depth of cut great in order to aggravate cutter wearing and tearing.

As shown in fig. 3, the method for milling the cathode of the composite machining tool by the electrochemical discharge machine is characterized by comprising the following processes:

the method comprises the following steps: the tool cathode is arranged on a rotating shaft of the machine tool and is connected with a power supply cathode, the workpiece 8 is connected with a power supply 11 anode, and the processing sequence of the first blade 6 after tool setting is better than that of the second blade 7 according to the moving direction of the workpiece 8 and the rotating direction 10 of the tool cathode;

step two: the electrolyte is sprayed into the machining gap from the liquid outlet hole (2), the power supply is switched on, the feeding speed is gradually increased, so that arc discharge is generated between the cathode matrix 1 and the workpiece 8, and at the moment, the material is removed at a high speed under the action of the arc discharge and electrolysis;

step three: under the action of electrolysis, a concave structure is formed on the machined bottom surface, and under the successive milling action of the first blade 6 and the second blade 7, the machined bottom surface can be leveled, so that the efficient and high-precision machining of the conductive material workpiece 8 is realized.

Claims

1. A tool cathode for electrochemical discharge mechanical milling composite machining, characterized in that:

the cathode comprises a cathode substrate (1), wherein the cathode substrate (1) is a circular electrode, and a blind hole is formed in the center of the cathode substrate from top to bottom;

a plurality of rows of liquid outlet holes (2) which are vertically distributed are arranged on the side wall of the lower end of the cathode substrate (1);

a reinforcing boss (3) is arranged on the upper surface of the bottom of the cathode substrate (1) along the diameter direction;

two ends of the reinforcing lug boss (3) are respectively positioned between the two rows of liquid outlet holes (2);

a near chute (4) and a far chute (5) are arranged below the bottom of the cathode base body (1) corresponding to the reinforcing lug boss (3);

a first blade (6) is embedded in the near chute (4), and a second blade (7) is embedded in the far chute (5);

the two chutes are same in shape and are both parallelogram, and the shortest distance from the center of the near chute (4) to the outer wall of the cathode substrate (1) is less than the shortest distance from the center of the far chute (5) to the outer wall of the cathode substrate (1);

the first blade (6) and the second blade (7) are the same in shape and are both parallelogram, and the outer tool tips of the embedded blades are all positioned on the extension line of the bus of the outer wall of the cathode substrate (1);

the first blade (6) and the second blade (7) are made of insulating materials, and the exposed height of the first blade (6) is smaller than that of the second blade (7).

2. The tool cathode for electrochemical discharge mechanical milling composite machining according to claim 1, characterized in that: the cathode substrate (1) is made of copper-tungsten alloy.

3. The method of using a tool cathode for electrochemical discharge mechanical milling composite machining according to claim 1, characterized by comprising the following processes:

the method comprises the following steps: the tool cathode is arranged on a machine tool rotating shaft, the machine tool rotating shaft is connected with the negative electrode of a power supply (11), the workpiece (8) is connected with the positive electrode of the power supply (11), and the processing sequence of the first blade (6) after tool setting is superior to that of the second blade (7) according to the moving direction of the workpiece (8) and the rotating direction (10) of the tool cathode;

step two: the electrolyte is sprayed into the machining gap from the liquid outlet hole (2), the power supply is switched on, the feeding speed is gradually increased, so that arc discharge is generated between the cathode matrix (1) and the workpiece (8), and at the moment, the material is removed at a high speed under the action of the arc discharge and electrolysis;

step three: under the action of electrolysis, a concave structure is formed on the machined bottom surface, and under the successive milling action of the first blade (6) and the second blade (7), the machined bottom surface can be leveled, so that the efficient and high-precision machining of the conductive material workpiece (8) is realized.

4. The use method of the tool cathode for electrochemical discharge mechanical milling composite machining according to claim 3, characterized in that:

the outer diameter of a cathode substrate (1) of the adopted tool cathode is 6mm-30 mm;

the cutting depth of the cathode of the adopted tool is 2mm-50 mm;

the electrolyte is sodium nitrate solution or sodium chloride solution.