JP3627089B2 - Surface treatment equipment for ball end mill cutting edge - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention uses a green compact electrode formed by compression molding a metal powder, a metal compound powder or a ceramic powder as an electrode to generate a pulsed discharge between the electrode and the workpiece with the machining fluid interposed therebetween, and the discharge energy. This relates to a discharge surface treatment apparatus for forming a hard coating made of a material generated by reaction of electrode material or electrode material with discharge energy on the work surface. It is aimed.
[0002]
[Prior art]
A technology for applying corrosion resistance and wear resistance by coating the surface of a metal material by submerged discharge has already been filed for patent. The outline of the technology is as follows. Electrode material is deposited on the work surface by discharging in liquid with an electrode formed by mixing WC and CO powders and compression-molding. Thereafter, remelting electric discharge machining is performed with another electrode (for example, a copper electrode or a graphite electrode) to obtain higher hardness and higher adhesion.
[0003]
Hereinafter, the prior art will be described with reference to FIG.
Using a mixed green powder electrode 201 of WO-CO (tungsten carbide-cobalt), electrical discharge machining is performed in a liquid with a workpiece 202 as a material to be processed (base material S50) to deposit WO-CO. (Primary processing). Next, remelting processing (secondary processing) is performed with an electrode such as a copper electrode that is not so consumed. When the primary processing was deposited, the structure had a hardness of about Hv = 1410 and many cavities, but the secondary processing remelting process eliminated the cavities of the coating layer, and the hardness improved to Hv = 1750.
[0004]
This method provides a coating layer that is hard and has good adhesion to steel. However, it has been difficult to form a coating layer having strong adhesion on the surface of a sintered material such as cemented carbide.
[0005]
However, according to our research, when a discharge is generated between a material that forms a hard carbide such as Ti as an electrode and a metal material as a material to be processed, a strong hard film is formed without a remelting process. It was found that it can be formed on the metal surface that is the material to be treated. This is because TiC is produced by the reaction between the electrode material consumed by the discharge and carbon C, which is a component in the working fluid. Further, when a discharge is generated by interposing a working fluid with a metal material that is a material to be processed by a compacted electrode of a metal hydride such as TiH2 (titanium hydride), a material such as Ti is obtained. It has been found that a hard film can be formed faster and better in adhesion than in the case of use. Furthermore, when a discharge is generated between the metal material that is the material to be treated by a green compact electrode in which other metal or ceramic is mixed with a hydride such as TiH2 (titanium hydride), hardness, wear resistance, etc. It has been found that hard coatings with various properties can be formed quickly. As for the hardness, Hv = 2500 or more is obtained, and the performance equivalent to that of the conventional PVD and CVD is obtained. In the performance test applied to the tool, the wear life is confirmed to be the same as that of the conventional method. Yes. Furthermore, it has been found that the adhesion strength is extremely excellent, and even in a scratch (peel strength) test, there is a characteristic that an acoustic signal indicating the breakage or delamination of the hard coating is hardly detected.
[0006]
[Problems to be solved by the invention]
FIG. 7 shows the outline of a ball end mill which is a general tool for machine tools. Ball end mills are rapidly spreading as indispensable tools for recent high-speed cutting. The tip has a shape with a constant radius of curvature R, and there are two blades, three blades, and the like. The tip of the ball end mill is composed of a cutting edge having a rake angle, and has a twist angle in the axial direction and is connected to the root shank. Recently, in general machined parts including molds, materials to be machined are extremely hard, and materials having high toughness tend to be frequently used, and the life of tools is severely reduced, which is an obstacle to productivity. For this reason, when the tool reaches the end of its life, the cutting edge is polished by a tool grinder or the like to correct and reuse the cutting edge. However, a hardening process for improving the hardness of the cutting edge may be used in combination. In general, a surface hardening treatment known by chemical vapor deposition (CVD), physical vapor deposition (PVD) or the like is often employed.
However, since the surface-cured material is peeled or removed at the stage of re-polishing, it is divided into whether it is used for processing without re-hardening or used after surface-hardening. However, the surface hardening treatment is expensive and requires a certain treatment period, and it is necessary to have a certain amount of work in progress, and many of them are based on the benefits of extending the tool life by surface hardening treatment only for the first time. The current situation is. In addition, the surface hardening treatment is generally expensive, and is often outsourced to specialized contractors, making it impossible to install the equipment close to you and causing problems in terms of delivery time and handling of small lots. Currently.
[0007]
The discharge surface treatment apparatus provided by the present invention drastically solves these problems and easily forms a hard ceramic film on the edge of a ball end mill, greatly improving wear resistance and toughness, thereby extending the tool life. It can be done.
[0008]
[Means for Solving the Problems]
According to a ball end mill cutting edge surface treatment method according to a first aspect of the present invention , a discharge is performed by applying a cross-sectional shape of an electrode to a convex arc shape and causing the ball end mill edge to oppose with a minute gap so as to contact the outer surface. Is hardened by electric discharge machining while moving along the surface crossing the electrode cross-sectional direction.
[0009]
The surface treatment method for the ball end mill blade edge of the second invention is to move the ball end mill itself in the rotational direction in accordance with the movement during the process of moving the ball end mill along the outer surface of the electrode during the surface treatment. is there.
[0010]
The ball end mill used for the high speed cutting of the third invention is arranged such that the cross-sectionally projecting arc-shaped electrode and the ball end mill blade edge face each other with a minute gap, and a discharge is generated between them. A hard film is formed on the ball end mill cutting edge surface by moving the ball end mill cutting edge along the outer surface of the electrode in a direction transverse to the electrode cross-sectional direction.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 2 is a block diagram showing the concept of the ball end mill surface treatment apparatus according to the first embodiment of the present invention. In the figure, 1 is a green compact electrode, 2 is a workpiece, 3 is a machining tank, 4 is a machining fluid, 5 is a switching element for switching voltage and current applied to the green compact electrode 1 and the workpiece 2, and 6 is a switching element. A control circuit for controlling on / off of the element 5, 7 is a power source, 8 is a resistor, and 9 is a molded primary hard film.
[0012]
Next, surface treatment by the ball end mill surface treatment apparatus of the present embodiment will be described. In FIG. 3, reference numeral 120 denotes an electrode made of a compact of TiH2 (titanium hydride), which is formed for performing a discharge surface treatment on the ball end mill 110, and its cross section has an arc shape as shown in the figure. . Reference numeral 121 denotes a table that supports the electrode 120.
Reference numeral 111 denotes a rotating device that supports the electrodes and is called a C-axis. Reference numeral 112 denotes a main shaft that gives servo feed to the electrodes, 113 denotes a driving ball screw, 114 denotes a guide for guiding and supporting the main shaft 112, 115 denotes a gear, and 116 denotes a feed control motor. Reference numeral 117 denotes a pump for supplying a machining liquid, and 118 denotes a machining liquid tank.
In this configuration, the TiH 2 (titanium hydride) green compact electrode 120 and the ball end mill 110 are controlled to an appropriate gap (ten microns) using the main shaft 112, and between the green compact electrode 120 and the ball end mill 110. To generate a pulsed discharge.
While generating discharge, the table or electrode side is relatively moved in the direction (left-right direction in the drawing) across the electrode cross section along the arc-shaped outer surface of the green compact electrode 120 on the blade end face 110a. Then, the TiH2 (titanium hydride) green compact electrode 120 is consumed by the energy of the discharge, and the hard coating centered on Ti, which is the main component of the electrode 120, reacts with the carbon component in the machining liquid, and the ball end mill It adheres to the blade surface and forms a hard coating on the ball end mill surface. This hard coating has a very high hardness, and Hv = 2500-3000 is obtained. Furthermore, it is known that the adhesion strength is extremely high, and the strength is such that an acoustic signal (acoustic signal indicating destruction) cannot be detected in a scratch test or the like.
[0013]
Further details of the invention will be described.
FIG. 6 shows a cross section of the ball end mill and the electrode. In the figure, 125 is the first outer clearance angle (θ1) of the blade end 110a of the ball end mill, and 126 is the second outer clearance angle (θ2). Reference numeral 127 denotes a rake angle (θ3), and 128 denotes a discharge gap in which the electrode and the ball end mill face each other with a gap necessary for electric discharge machining. In such an arrangement, the C-axis device 111 is used to set the blade surface of the first outer clearance angle 125 of the ball end mill to be parallel to the outer surface of the electrode with respect to the green compact electrode 120. The position of the ball end mill with respect to the electrode at this time is defined as an angle 1 (122a) in FIG. FIG. 6 shows that the arc shape is moved while the discharge surface treatment is performed while controlling the axial movements of the angle 2 and the angle 3 and the X axis and the Z axis so as to cross the electrode along the arc surface of the electrode from the position of angle 1. A hard ceramic film can be uniformly formed on the blade surface having the first outer clearance angle.
In this state, half of the edge surface of the ball end mill has been processed. To process the other half, the method of moving from the position of angle 3 to angle 4 and angle 5 There is also a method of resetting the ball end mill angle 5 to the angle 4 and the angle 3 again when the processing is completed at the angle 3. The moving procedure may be properly used according to the purpose of the tool and does not need to be fixed. Thus, if it hardens | cures by electrical discharge machining, it can process uniformly over the whole blade surface (a range of about 180 degree | times) of a ball end mill.
The discharge trajectory 120a in FIG. 4 shows this state. When the ball end mill is moved so as to cross almost right side, the discharge trajectory remains as shown in FIG.
As can be seen from the shape of the cutting edge in FIG. 7, the blade surface is generally twisted with a constant curvature in the axial direction, and simply by crossing the surface of the arc-shaped protruding electrode, the above-mentioned first outer clearance angle is obtained. Uniform processing is difficult for the entire blade surface, and it is necessary to rotate the ball end mill itself at a constant ratio while moving the electrode surface. Thus, it is extremely effective to change the angle θ while synchronizing with the movement of the tool ball end mill. In the angle 1 of the ball end mill, the twist angle θ is changed from θ1 to θ3 when moving to the angle 2 and the angle 3.
As described above, according to the present embodiment, the outer surface of the electrode is formed into a projecting circular arc shape, the ball end mill blade edge is moved along the electrode, or the ball is moved using the C-axis device as necessary. The life of the ball end mill can be greatly improved by performing discharge surface treatment on the surface of the blade edge while moving the angle of the end mill itself to form a TiC carbide hard coating. Furthermore, there are many features such as easy processing as a ripple effect, the ability to use a commonly used electric discharge machining apparatus, and the need to commission an external specialist.
[0014]
Embodiment 2. FIG.
FIG. 7 shows an embodiment in which the electrode 120 is formed in a columnar shape, and the table 121 is changed to a V block shape. With this change, even if the electrode is consumed due to processing, it can be rotated and the opposite side can be used. Although the outer dimension of the electrode is small, the support is ensured by the V-block-shaped base 121, so that the workability can be improved and the electrode can be used to the end, and the material can be used effectively. The electrode external shape can be changed if the ball end mill trajectory program is changed, the processing program management is easy, and the electrode can be used many times.
FIG. 8 shows an embodiment in which the arrangement of the ball end mill as the electrode and the tool is reversed. A cylindrical electrode 120 is attached to the tip of the main shaft, the ball end mill is disposed horizontally on the table, and an angle indexing device is provided. This indexing device 130 indexes the angle of the ball end mill according to the progress of machining, and always controls the angle so that the first outer clearance angle of the blade surface is parallel to the electrode in conjunction with the position control of the electrode. . By arranging the tool in the horizontal direction, the electrode performs a circular motion while simultaneously controlling the XY axes in two directions along the cutting edge R surface of the tip as shown in FIG. The angle indexing device 130 gradually changes the angle of the ball end mill itself in accordance with the arc motion trajectory of the electrode, and the position is controlled so that the blade surface with the first outer clearance angle is always in contact with the outer surface of the electrode. If comprised in this way, since the shaping | molding of an electrode is a cylinder, it is easy, and it becomes the process sequence on the basis of a tool, and there exists an effect which workability | operativity can be improved significantly. Furthermore, arranging the tool sideways is excellent in visibility and can greatly improve workability.
[0015]
【The invention's effect】
The surface treatment method for the ball end mill blade edge according to the first aspect of the invention can greatly improve the life of the ball end mill by subjecting the ball end mill edge surface to a discharge surface treatment to form a carbide hard film.
[0016]
The surface treatment method of the ball end mill blade edge according to the second aspect of the invention can easily and reliably process the blade edge having a complicated curved surface by controlling the angle of the ball end mill itself, resulting in a long life of the ball end mill. It will be possible to greatly improve.
[0017]
In the ball end mill of the third invention, the surface of the ball end mill blade edge is subjected to discharge surface treatment to form a hard carbide film, and the life of the ball end mill can be greatly improved.
[Brief description of the drawings]
FIG. 1 is a principle diagram of a conventional hard film forming technique.
FIG. 2 is a basic principle diagram of the present invention.
FIG. 3 is a diagram showing a processing principle of a ball end mill which is an object of the present invention.
FIG. 4 is a diagram showing a processing principle by a ball end mill.
FIG. 5 is a basic position configuration diagram of an electrode and a ball end mill according to the present invention.
FIG. 6 is a cross-sectional view of the present invention.
FIG. 7 is a diagram showing another embodiment of the present invention.
FIG. 8 is a diagram showing still another embodiment of the present invention.
[Explanation of symbols]
1 Green compact electrode (primary processing electrode), 2 workpieces, 3 processing tanks, 4 processing fluids,
5 switching elements, 6 control circuits, 7 power supplies, 8 resistors,
9 Hard skin (film base hard coating), 110 ball end mill,
111 C-axis device, 112 spindle, 120 electrodes, 121 units, 122 angle 125 first outer clearance angle, 126 second outer clearance angle, 127 rake angle,
128 poles, 130 angle indexer.

Claims (3)

A compact powder electrode made by compression molding metal powder, metal workpiece powder, or ceramic material powder, or metal electrode is used as an electrode to generate a pulsed discharge between the electrode and workpiece. And a discharge surface treatment method for a ball end mill blade edge that forms a coating made of an electrode material or a substance formed by a reaction of the electrode material with the discharge energy by the discharge energy ,
A step in which the cross-sectional shape of the projecting arc-shaped electrode and the ball end mill blade tip are arranged facing each other with a minute gap;
Generating a discharge between the electrode and the ball end mill cutting edge, and moving the ball end mill cutting edge along the electrode outer surface in a direction transverse to the electrode cross-sectional direction;
A surface treatment method for a ball end mill cutting edge, wherein a hard coating is formed on the ball end mill cutting edge surface. 2. The surface treatment of a ball end mill cutting edge according to claim 1, wherein the ball end mill itself is moved in the rotational direction in accordance with the movement during the process of moving the ball end mill along the outer surface of the electrode during the surface treatment. Method. A ball end mill used for high speed cutting,
A cross-sectional shape of the projecting arc-shaped electrode and the ball end mill blade edge are arranged to face each other with a minute gap, and a discharge is generated between them, so that the ball end mill blade edge is transverse to the electrode sectional direction. A ball end mill in which a hard coating is formed on the edge surface of the ball end mill by moving along the outer surface of the electrode.

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