JPH11320273A - Surface processing device for knife edge of ball end mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the lifetime of a tool by forming a hard ceramic film simply on the knife edge of a ball end mill, enhancing the anti-abrasiveness, and heightening the toughness. SOLUTION: A knife edge of a ball end mill 110 is subjected to an electric discharge surface processing so that a hard film is formed on the knife edge, when the section shape of an electrode 120 is made an arc of circle protruding, and electric discharge is conducted with the knife edge of the end mill 110 confronting with a micro-gap in between so as to make contacting with the outside surface, and electric discharge machining is made while the knife edge of the end mill 110 is moved along the surface in the direction across the electrode section, and surface hardening is accomplished by the electric discharge processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulsed electric discharge between an electrode and a workpiece by interposing a working fluid with a compacted electrode formed by compression molding a metal powder, a metal compound powder or a ceramic powder. And a discharge surface treatment apparatus that forms a hard coating made of an electrode material or a substance generated by the reaction of the electrode material with the discharge energy by the discharge energy, the cutting edge of a ball end mill as a tool. Is intended to be subjected to a discharge surface treatment.

[0002]

2. Description of the Related Art A technique for imparting corrosion resistance and abrasion resistance by coating the surface of a metal material by in-liquid discharge has already been applied for a patent and is known. The outline of the technology is as follows. The electrode material is deposited on the work surface by performing submerged discharge with an electrode obtained by mixing and compressing WC and CO powders. Thereafter, another electrode (for example, a copper electrode or a graphite electrode) is used to perform remelting discharge machining to obtain higher hardness and higher adhesion.

The prior art will be described below with reference to FIG. Using a mixed green compact electrode 201 of WO-CO (tungsten carbide-cobalt), electrical discharge machining is performed in a liquid between the workpiece 202 as a material to be processed (base material S50) and WO-CO is deposited. (Primary processing). Then, re-melting (secondary processing) is performed using an electrode that does not wear much, such as a copper electrode. With the primary processing deposited as it was, the structure had a hardness of about Hv = 1410 and many cavities. However, the reworking of the secondary processing eliminated the cavities in the coating layer and improved the hardness to Hv = 1750.

According to this method, a coating layer which is hard and has good adhesion to steel is obtained. However, it has been difficult to form a coating layer having strong adhesion on the surface of a sintered material such as a cemented carbide.

However, according to our research, when a material that forms a hard carbide such as Ti is used as an electrode and a discharge is generated between the material and a metal material to be processed, a strong melting can be achieved without a remelting process. It was found that a hard film could be formed on the surface of the metal to be treated. This is because the electrode material consumed by the discharge reacts with carbon C, which is a component in the working fluid, to cause T
It depends on what iC generates. In addition, TiH2
(Titanium hydride) and a metal hydride compact electrode make it possible to generate a discharge by interposing a machining fluid between the electrode and the metal material to be treated, which is more effective than when a material such as Ti is used. It was found that the film was fast, had good adhesion, and could form a hard film. Further, when a discharge is generated between the metal material as a material to be processed by a green compact electrode in which another metal or ceramic is mixed with a hydride such as TiH2 (titanium hydride), hardness, abrasion resistance, etc. It has been found that a hard coating having various properties can be quickly formed. As for the hardness, Hv = 2500 or more is obtained, and the same performance as that of the conventional PVD and CVD is obtained. In the performance test applied to the tool, the wear life is confirmed to be substantially the same as that of the conventional method. I have. Further, it is known that the adhesive strength is extremely excellent, and that even in a scratch (peeling strength) test, an acoustic signal indicating destruction and peeling of the hard coating is hardly detected.

[0006]

FIG. 7 shows an outer shape of a ball end mill which is a tool for a general machine tool. Ball end mills are rapidly spreading as indispensable tools for recent high-speed cutting. The tip has a shape having a constant radius of curvature R, and includes a two-blade, a three-blade, and the like. The tip of the ball end mill is composed of a cutting edge having a rake angle, and is connected to the root shank with a twist angle in the axial direction. Recently, in general machined parts including dies, materials to be machined are extremely hard and materials with high toughness tend to be frequently used, and tool life is greatly reduced, which is a factor inhibiting productivity. Therefore, when the tool reaches the end of its service 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 some cases. Generally, a surface hardening treatment known by a chemical vapor deposition method (CVD) or a physical vapor deposition method (PVD) is often employed. However, since the surface-hardened material is peeled or removed at the stage of re-polishing, it can be used for processing without re-hardening or used after surface hardening. However, surface hardening treatment is expensive and requires a certain processing time, so it is necessary to have a certain amount of work in progress. That is the current situation. In addition, surface hardening treatment generally requires high equipment costs, and is often outsourced to specialized contractors, making it impossible to install the equipment close to the user, and causing problems in terms of delivery time and handling of small lots. It is the current situation.

[0007] The electric discharge surface treatment apparatus provided by the present invention drastically solves these problems and can easily form a hard ceramic film on the cutting edge of a ball end mill to greatly improve wear resistance and toughness. Can be extended.

[0008]

According to a first aspect of the present invention, there is provided a ball end mill blade surface treatment apparatus in which a cross section of an electrode is formed in a convex arc shape, and a blade end of the ball end mill is opposed to the outer surface of the ball end mill with a small gap. Let it discharge,
The surface is hardened by electrical discharge machining while moving the blade end of the ball end mill along the surface in a direction transverse to the electrode cross-sectional direction.

A ball end mill blade surface treatment apparatus according to a second aspect of the present invention is characterized in that the number of simultaneous control axes for numerical control of the feed of the ball end mill or the electrode is two or more in the course of the discharge surface treatment. .

The ball end mill blade surface treatment apparatus of the third invention moves the ball end mill itself in the rotational direction in accordance with the movement during the machining of moving the ball end mill along the outer surface of the electrode during the discharge surface treatment. It is characterized by the following.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 2 is a configuration 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 work, 3 is a processing tank, 4 is a processing liquid, 5 is a green compact electrode 1
And a switching element for switching the voltage and current applied to the work 2, 6 is an on state of the switching element 5,
A control circuit for controlling turning off, 7 is a power supply, 8 is a resistor, and 9 is a molded primary hard coating.

Next, the 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 TiH2 (titanium hydride) -based green compact 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 support for supporting the electrode 120. Reference numeral 111 denotes a rotating device that supports the electrodes and is called a C-axis. 112 is a spindle for providing servo feed to the electrode,
113 is a ball screw for driving, 114 is a guide for guiding and supporting the main shaft 112, 115 is a gear, and 116 is a motor for feed control. 117 is a pump for supplying a working fluid,
Reference numeral 118 denotes a processing liquid tank. In this configuration, Ti
An H2 (titanium hydride) -based green compact electrode 120 and a ball end mill 110 are attached to an appropriate gap (10
A pulse-like discharge is generated between the green compact electrode 120 and the ball end mill 110 while controlling to several microns. The table or the electrode side is relatively moved along the arc-shaped outer surface of the green compact electrode 120 along the arc-shaped outer surface of the compacted electrode 120 (left-right direction in the drawing) while generating electric discharge. Then, the TiH2 (titanium hydride) -based green compact electrode 120 is consumed by the energy of the discharge, and the hard coating mainly composed of Ti, which is a main component of the electrode 120, reacts with the carbon component in the working fluid to form a ball end mill. It adheres to the blade surface and forms a hard coating on the surface of the ball end mill. This hard coating has a very high hardness and Hv = 25.
00-3000 are obtained. Further, it has been found that the adhesive strength is extremely high, and the sound signal (sound signal indicating destruction) has such a strength that it cannot be detected in a scratch test or the like.

Further, details of the present 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 cutting edge 110a of the ball end mill, and 126 is the second outer clearance angle (θ2).
It is. 127 indicates a rake angle (θ3), and 128 indicates a discharge gap in which an electrode and a ball end mill are opposed to each other with a gap required for electric discharge machining. In such an arrangement, the C-axis device 111 is arranged so that the blade surface of the first outer peripheral relief angle 125 of the ball end mill is parallel to the outer surface of the electrode with respect to the green compact electrode 120.
Set using. The position of the ball end mill with respect to the electrode at this time is defined as an angle 1 (122a) in FIG. Angle 1
From the position shown in FIG. 6 when the arc is discharged and surface-treated while controlling the axis movement of the angles 2 and 3 and the X-axis and the Z-axis so as to cross the electrode along the arc surface of the electrode. A hard ceramic film can be formed uniformly on the blade surface at one clearance angle. In this state, half of the blade surface of the ball end mill has been processed. To process the other half in the same manner, the method of moving from the position of the angle 3 to the angles 4 and 5 as it is, There is also a method of resetting the ball end mill angle 5 again when the processing at the angle 3 is completed, and moving the ball end mill to the angle 4 and the angle 3. The moving procedure may be properly used depending on the purpose of the tool, and does not need to be particularly fixed. When the hardening treatment is performed by the electric discharge machining in this way, it is possible to uniformly process the entire blade surface of the ball end mill (in the range of about 180 degrees). The discharge trajectory 120a shown in FIG. 4 indicates this state. When the ball end mill is moved so as to cross almost right beside, the discharge trajectory remains as shown in FIG. As can be seen from the blade tip shape in FIG. 7, the blade surface is generally twisted at a constant curvature in the axial direction, and simply by traversing the arc-shaped projecting electrode surface, the first outer peripheral angle of the first outer clearance angle is reduced. It is difficult to perform uniform processing on the entire blade surface, and it is necessary to rotate the ball end mill itself at a fixed ratio while moving the electrode surface. It is extremely effective to change the angle θ while synchronizing with the movement of the tool ball end mill. At the angle 1 of the ball end mill, the torsion angle θ changes from θ1 to θ3 when moving to angles 2 and 3. As described above, according to the present embodiment, the outer surface of the electrode is formed in a protruding arc shape, and the blade end mill is moved along the electrode, or the ball is formed by using a C-axis device as necessary. By performing the discharge surface treatment on the cutting edge surface while moving the angle of the end mill itself to form a TiC-based carbide hard coating, it is possible to greatly improve the life of the ball end mill. In addition, it can be easily processed as a ripple effect,
There are many features such as the fact that a commonly used electric discharge machine can be used, and the need to outsource to an external specialist is unnecessary.

Embodiment 2 FIG. In FIG. 7, the electrode 12
This shows an embodiment in which 0 is a column shape, and the base 121 is changed to a V block shape. By changing in this way, even if the electrode is worn out by machining, it can be rotated and the opposite side can be used, and even if the shape needs to be corrected due to wear, if the outer shape is circular, it is easier to work than the first time Although the outer dimensions of the electrodes are reduced, the V-block-shaped table 121 ensures the support, but the workability is improved, the electrodes can be used to the end, and the material can be effectively used. The electrode shape can be changed as it is by changing the trajectory program of the ball end mill, the machining program management is easy, and the electrode can be used many times. FIG. 8 shows an embodiment in which the arrangement of the electrodes and the ball end mill as a tool is reversed. A cylindrical electrode 120 is attached to the tip of the main shaft, the ball end mill is arranged horizontally on a table, and an angle indexing device is provided. The indexing device 130 determines the angle of the ball end mill in accordance with the progress of machining, and constantly 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 an arc motion along the cutting edge R surface of the tip while performing simultaneous two-axis control of XY axes as shown in FIG. The angle of the ball end mill itself is gradually changed by the angle indexing device 130 in accordance with the arc movement trajectory of the electrode, and the position is controlled so that the blade surface of the first outer clearance angle is always in contact with the outer surface of the electrode.
With this configuration, there is an effect that the electrode can be easily formed because the electrode is formed in a cylindrical shape, and a machining procedure based on a tool is provided, thereby greatly improving workability. Further, arranging the tools in a horizontal direction has excellent visibility and can greatly improve workability.

[0015]

According to the ball end mill surface treating apparatus of the first aspect of the present invention, the surface of the blade of the ball end mill is subjected to a discharge surface treatment to form a TiC-based carbide hard coating, thereby greatly improving the life of the ball end mill.

The ball end mill surface treatment apparatus of the second invention can cope with a complicated torsion shape of the blade end of the ball end mill by using a plurality of moving axes, and as a result, the hard coating to the first outer clearance angle is formed. It is possible to facilitate molding and greatly improve the life of the ball end mill.

The ball end mill surface treatment apparatus of the third invention can easily and reliably treat a cutting edge having a complicated curved surface by controlling the angle of the ball end mill itself in addition to the multi-axis movement control. As a result, 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 view showing a processing principle of a ball end mill which is an object of the present invention.

FIG. 4 is a diagram showing the principle of processing by a ball end mill.

FIG. 5 is a basic position configuration diagram of an electrode and a ball end mill of the present invention.

FIG. 6 is a diagram showing a 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 treatment electrode), 2 work, 3
Processing tank, 4 processing liquid, 5 switching element, 6 control circuit, 7 power supply, 8 resistor, 9 hard skin (hard coating under film), 110 ball end mill, 111 C axis device, 112 main shaft, 120 electrodes, 121 units, 122
Angle 125 First outer clearance angle, 126 Second outer clearance angle, 1
27 Rake angle, 128 poles, 130 angle indexing device.

Claims (3)

[Claims] 1. A compact powder electrode obtained by compression-molding a metal powder, a powder of a metal workpiece, or a powder of a ceramic material, or a metal electrode as an electrode, and a working fluid interposed therebetween. In a discharge surface treatment device of a ball end mill blade, which forms a discharge consisting of an electrode material or a substance formed by reacting the electrode material with the discharge energy, the discharge energy is generated on the work surface by the discharge energy. In addition, the discharge surface treatment is performed to form a hard coating on the tip surface of the ball end mill, and in the discharge surface treatment step, the electrode is formed in a projecting arc shape in cross section, and the ball end mill is brought into contact with the outer surface thereof. The blade end of the ball end mill with a small gap to discharge. Surface treatment apparatus of the ball end mill cutting edge to surface hardening discharge machining to while moving along the direction of the surface transverse to the cross-sectional direction. 2. The surface treatment device for a ball end mill blade edge according to claim 1, wherein the number of simultaneously controlled axes of numerical control for feeding the ball end mill or the electrode is two or more. 3. The method according to claim 1, wherein, during the discharge surface treatment, the ball end mill itself is moved in the rotation direction in accordance with the movement during the processing of moving the ball end mill along the outer surface of the electrode. The surface treatment device for a ball end mill blade according to claim 2.