JPH09150305A - High speed cutting work method for die and superhigh speed milling device using this method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve various problematic points in the past and shorten a die machining time, by remarkably increasing a rotational speed and a feed speed of a cutting tool, also reciprocating a feed program of the tool. SOLUTION: A heat resistant tool, for instance, a single small diametric ball end mill 12 formed of cBN is rotated at a 5 to 200,000rpm high speed and reciprocated horizontally at a 10 to 100m/min high speed, the ball end mill is laterally moved in both end parts of reciprocating motion by a prescribed cutting amount in a horizontal surface to a direction orthogonal to a reciprocating direction, and cut by the same depth of cut, in the same surface and is vertically fed in a perpendicular direction by a prescribed depth of cut, so as to work a die shape by a high speed rotating/reciprocating motion of the single small diametric ball end mill.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed cutting method for a mold and an ultra-high-speed milling apparatus using the method.

[0002]

2. Description of the Related Art Many machine parts are formed using molds, and molds are indispensable for producing high-quality machine parts in large quantities at low cost. On the other hand, the manufacture of the mold itself has conventionally been long and costly. However, with the generalization of small-quantity production and the shortening of the product cycle, there is a strong demand for shortening the mold manufacturing period and reducing costs.

Conventionally, mold production is performed in the order of design, mold processing, assembly / finish, trial / correction, and the like. Of these, the design itself can be done in a relatively short period of time due to the development of CAD and molding simulation, etc. Currently, the most time is spent on NC programming for die processing and die processing. Have been.

[0004]

Most of the die machining is milling with an end mill. However, in the case of many complicated shapes, the tool diameter cannot be increased except for rough machining.
Mainly light cutting with small diameter tools. Therefore, there is a problem that the feed is small and the cutting time is long. Therefore, the cutting time can be reduced by increasing the rotation speed of the cutting tool and increasing the feed rate. In this case, the conventional machining method requires a tool life, high-speed rotation drive, and durability of the bearing. , Tool holders, high-speed feed mechanisms, preparation of NC tapes, thermal deformation of machine tools, generation of steps on the surface to be cut due to tool change, and breakage of tools due to unexpected increase in cutting depth.

That is, when high-speed rotation and high-speed feed are performed, the life of the tool is shortened, the frequency of tool change is increased, and as a result, high-speed machining cannot be performed. The conventional tool rotation speed is several thousand rpm or less. Of conventional ball bearings, which need to be increased to tens of thousands
It can be used up to about 10,000 rpm, but at higher speeds, the service life is so short that it cannot be used practically. At a high speed rotation of more than tens of thousands of rpm, the conventional tool holder loosens the tool holding part due to centrifugal force ( High-speed feed is indispensable for high-efficiency machining, which causes problems of enlargement) and dynamic balance, but conventional ball screws require 20 to 60 m / min.
Is the limit. In addition, acceleration and deceleration characteristics become important when high-speed feeding is performed, and drive and braking devices are enlarged to accelerate and decelerate in a short time. Even today, it takes a considerable amount of time to make NC tapes. In particular, in conventional 3-axis control, the time required to create an NC tape is increasing more and more because cutting is performed by reducing the feed pitch of the tool. When high-speed rotation and high-speed feed are performed, heat generation from the high-speed drive shaft and machining Due to heat, etc., especially in the case of die machining where dimensional accuracy is important, thermal deformation of the machine tool can not be ignored, and if the tool is replaced, mounting errors, elastic deformation of the tool, and variations in tool dimensions will cause Conventionally, there is a step in the surface and an error in the surface accuracy occurs.In the past, the machining efficiency was generally improved by roughly dividing into roughing and finishing, but the cutting depth of the tool often increased during the finishing after roughing, and There is a possibility that the cause and the like, there has been a problem point etc. is.

The present invention has been made to solve such a problem. That is, an object of the present invention is to solve the above-described various problems by greatly increasing the rotation speed and the feed speed of the cutting tool, thereby greatly reducing the processing time of the die. An object of the present invention is to provide a cutting method and an ultra-high-speed milling apparatus using the method.

[0007]

Means for Solving the Problems The inventors of the present invention have proposed cBN.
(Cubic boron nitride)
It has been found through experiments that it is suitable for ultra-high-speed milling of iron-based metal materials for molds, and that the tool life is prolonged at higher speeds. The present invention positively utilizes such new characteristics, uses one small-diameter tool made of a tool material having high heat resistance, and rotates the tool at a high speed and at a high speed. It solves the point.

That is, according to the present invention, a single small-diameter ball end mill made of a tool material having high heat resistance can be used for 5 to 5 minutes.
The ball end mill is rotated at a high speed of 200,000 rpm and reciprocated horizontally at a high speed of 10 to 100 m / min. At both ends of the reciprocation, the ball end mill is traversed by a predetermined cutting amount in a horizontal plane in a direction orthogonal to the reciprocating direction. It moves and cuts the same plane at the same depth of cut, then vertically feeds the ball end mill vertically at the predetermined depth of cut, whereby the single small-diameter ball end mill rotates at high speed and reciprocates at high speed. The present invention provides a high-speed cutting method for a mold, wherein a three-dimensional shape is machined by the method.

According to the method of the present invention, a single small-diameter ball end mill made of a tool material having high heat resistance can be used for 5 to 5 minutes.
Since it is rotated at a high speed of 200,000 rpm, a mold having a complicated shape and a small R portion can be processed. Moreover, this small-diameter ball end mill is horizontally set at 10 to 100 m / min.
By reciprocating at high speed, the work surface can be cut at high speed and high efficiency. Furthermore, the same plane is cut at the same cutting depth by high-speed reciprocating motion, and then the ball end mill is fed vertically at a predetermined cutting depth in the vertical direction, so that the cutting depth by the ball end mill is almost always constant. Since the cutting is performed while being held, it is easy to maintain the cutting conditions in the optimum region, and the life of the tool can be extended. Further, since the high-speed axis is only reciprocating, the creation of the NC program is simplified, and real-time NC control can be performed while creating data by the computer. At present, it takes a considerable amount of time to create an NC program. Therefore, a drastic reduction in the NC program creation time contributes to a reduction in the die manufacturing time as a whole. Further, since machining is performed by a single small-diameter ball end mill, there is no problem of an installation error or a variation in tool dimensions due to tool exchange. In addition, since there is no distinction between roughing and finishing, high-speed machining is performed on the same plane with a single tool. Easy and less risk of tool breakage. Also,
It is also possible to prevent tool breakage due to variation in the amount of cutting of the tool due to a mistake in the NC program.

According to a preferred embodiment of the present invention, before the high-speed reciprocating cutting in the same plane, relatively low-speed feeding is performed along the contour line of the outer peripheral contour at the same cutting depth in the same plane. With cutting. According to this method, since cutting is performed at relatively low speed feed, it can follow NC data, and a program can be easily and automatically generated in real time.
In addition, only reciprocating machining results in grooving during the first pass, which increases the tool load and makes high-speed feeding difficult.However, before high-speed feeding, first, the outer peripheral machining with contour contours is performed at relatively low speed. Thus, the load during high-speed feeding thereafter can be greatly reduced. Further, since the sheet is fed along the contour line of the outer peripheral contour, the surface roughness of the outer peripheral wall surface at least in the peripheral direction is greatly improved. In addition, it is possible to avoid excessive travel due to rapid stoppage at the time of high-speed feed, and eliminate the influence of a tool stop position error.

According to the present invention, a single small-diameter ball end mill made of a tool material having high heat resistance, a high-frequency motor for rotating the ball end mill at a high speed of 50,000 to 200,000 rpm, and a ball rotating at a high speed A high-speed bearing for supporting the end mill; a three-axis drive unit for moving the ball end mill in three directions of X-axis and Y-axis perpendicular to the horizontal plane and a Z-axis perpendicular to the horizontal plane; and NC control for numerically controlling the three-axis drive unit A three-axis driving device, wherein only the X-axis is
The small-diameter ball end mill is reciprocated at a high speed in the X-axis direction by the NC controller, and Y is moved at both ends of the reciprocating motion.
It is laterally moved by a predetermined cutting amount in the axial direction, cuts in the same plane at the same cutting depth, and then vertically feeds the ball end mill in the Z-axis direction at the predetermined cutting depth. An ultra-high-speed milling apparatus is provided, in which a three-dimensional shape is machined by high-speed rotation and high-speed reciprocation of a small-diameter ball end mill. The high-speed reciprocating motion of the X axis of the present invention is usually performed by a ball screw, but according to a more preferred embodiment, driven by a linear motor.

According to the configuration of the present invention, since the small-diameter ball end mill is rotated at a high speed to perform the processing while keeping the depth of cut constant, high-speed processing is possible even if the depth of cut is reduced, and the load is reduced. Since it can be made smaller, support by a high-speed bearing and high-speed rotation by a high-frequency motor become possible. Further, since a single small-diameter ball end mill is used without replacement, a lightweight and small tool holder can be used, and problems such as loosening of the tool holding portion and dynamic balance due to centrifugal force can be avoided. Furthermore, since only the reciprocating movement in the X-axis direction is performed at a high speed,
By reducing the weight of only the head for rotating and driving the ball end mill, high-speed feeding and acceleration / deceleration characteristics are improved, and acceleration / deceleration can be performed in a short time by a relatively small driving device. Further, since the high-speed axis is only reciprocating, even if the feed pitch of the tool is fine, the creation of the NC program is simplified, and real-time NC control can be performed while creating data by a computer. In addition, since high-speed rotation and high-speed feed are continued for a long time without replacing a single small-diameter ball end mill, the calorific value during operation becomes almost constant, and the heat balance is saturated, so that stable cutting can be performed. In addition, since machining is performed with a single small-diameter ball end mill, there is no problem of mounting errors or variations in tool dimensions due to tool change. There is no sudden change in the depth of cut, the depth of cut is easily maintained constant, and there is little risk of tool breakage.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic principle of the present invention and preferred embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show the results of experiments by the present inventors, and cBN
This is the result of ultra-high-speed milling of an iron-based metal material (work) for a mold using a high-density sintered cutting tool made of (cubic boron nitride).

FIG. 1 shows the relationship between the cutting length and the amount of wear when the cutting speed is changed. The conventional cutting speed in milling is 200 to 500 m / min. In this test, the test is performed at a speed 5 to 10 times or more the conventional speed. From this figure, 1000 to 3000 m / mi
In the speed range of n, a unique characteristic is shown that the higher the cutting speed, the smaller the amount of wear, that is, the higher the speed, the longer the tool life.

FIG. 2 is a view similar to FIG. 1 when the rotational speed of the tool (small-diameter ball end mill) is changed. Conventionally, the tool rotation speed in milling is 3 to 40.
In this test, the test is performed at a speed 5 to 20 times faster than the conventional speed. From this figure, 35,000 rp
At a rotation speed of m or more, as shown in FIG. 1, the higher the cutting speed, the smaller the amount of wear.

From the results of FIG. 1 and FIG. 2, it is possible to positively utilize the above-mentioned new characteristics, use one small-diameter tool made of cBN, and rotate and feed this tool at high speed.
By solving the various problems described above, ultra-high-speed milling can be performed. In addition to cBN, a tool material provided with a heat-resistant coating can have similar characteristics.

FIG. 3 is a schematic view showing a future view of the milling process. Milling processing in mold processing is progressing day by day due to its importance.
From the cutting speed of 0m / min, it is now about 200m / mi
The speed has been increased to about n. On the other hand, the feed (cutting depth) slightly increases with the increase in speed. Due to future technological innovation, cutting speed will be 4 ~ 500m /
min, and in the future, ultra high speed milling of about 1000 m / min is expected to be achieved. In addition, it is thought that a cut (cutting depth) becomes rather small from the necessity of precision processing. The present invention provides one means for achieving ultra-high speed milling based on this perspective.

FIG. 4 is an overall configuration diagram of an ultra-high-speed milling apparatus using the method according to the present invention. In this figure,
The ultra-high-speed milling device 10 of the present invention includes a single small-diameter ball end mill 12 made of a tool material having high heat resistance,
A high-frequency motor 14 that rotates the ball end mill 12 at a high speed of 50,000 rpm, a high-speed bearing 16 that supports the ball end mill 12 that rotates at a high speed, and an X-axis and a Y-axis that are perpendicular to a horizontal plane. A three-axis driving device 18 that moves in the three Z-axis directions and an NC control device 20 that numerically controls the three-axis driving device 18 are provided. As for the vertical Z axis, there are a method of moving the table surface as shown in this figure, and a method of moving the X axis slide portion 21 in the vertical direction. In this drawing, reference numeral 1 denotes a work (a workpiece).

The ball end mill 12 has a high density sintered c
Use BN. C has emerged as a new cutting tool material
BN (cubic boron nitride) has heat resistance, high toughness, and reduced occurrence of chipping. This high density c
According to the above test using a BN tool, 100
0-1500m / min, 2000-3000m with cast iron
/ Min super high speed milling is possible. Note that the ball end mill 12 may be a tool material having high heat resistance other than cBN. For example, a tool having a multilayer ceramic coating applied to a usual cemented carbide matrix, or an improved ceramic tool may be used.

In this figure, the ball end mill 12 rotates about the Z axis, is mounted on a support via a high-speed bearing 16, and this support reciprocates at a high speed in the X-axis direction. In the surface finish of the mold, the tip is 2-10m
A ball end mill having a small diameter of about m is most suitable. Further, in order to realize the above-described high-speed cutting speed with the small-diameter ball end mill 12, the number of rotations of the main shaft is 50,000 to 200,000 rpm.
requires m. In order to realize this high-speed rotation, the apparatus of the present invention uses a high-frequency motor 14 and an air bearing 16 as a high-speed bearing. According to this configuration, since the small-diameter ball end mill 12 is rotated at a high speed, the depth of cut per blade is very small and the cutting resistance is small, so that the support by the air bearing 16 and the high-speed rotation by the high-frequency motor 14 are possible. . The high-speed bearing 16 may be an air bearing, a magnetic bearing, or a high-speed ball bearing using ceramic.

The three-axis drive unit 18 has only the X-axis
It can reciprocate at a high speed of 00 m / min. In order to realize rapid acceleration and rapid deceleration by high-speed feed of the spindle and to achieve accurate positioning, it is important to reduce the weight of the movable part of the spindle. Therefore, in the present invention, the high-speed feed shaft is
Of the three axes, only one axis (X axis only) is set, and the other two axes (Y axis and Z axis) are set to low-speed feeding. In FIG. 4, the three-axis driving device 18 is of a gantry type, but the present invention is not limited to this, and other types of vertical or horizontal types may be used. The X-axis high-speed reciprocating motion generally uses a ball screw, but is preferably driven by a linear motor.

With the above-described structure, high-speed feeding and acceleration / deceleration characteristics can be improved, and acceleration / deceleration can be performed in a short time by a relatively small driving device. Further, since the cutting resistance is small, the high-speed feed shaft (X-axis) may be reduced in weight and may have a slight decrease in rigidity. As a result, the apparatus can be made relatively lightweight and cost can be reduced despite high-speed processing.

FIG. 5 is a view schematically showing a high-speed cutting method for a mold according to the present invention. In this figure, (A) is a side sectional view showing the movement of the small-diameter ball end mill 12 with respect to the work 1 on the X axis and the Z axis. Also,
FIG. 2B is a plan view showing the movement of the small-diameter ball end mill 12 with respect to the workpiece 1 on the X axis and the Y axis. (C) shows a small-diameter ball end mill 12 in the same plane.
Is schematically shown.

As shown in FIG. 5, according to the method of the present invention, a single small-diameter ball end mill 12 made of a tool material having high heat resistance is rotated at a high speed of 50,000 to 200,000 rpm.
The ball end mill 12 is set horizontally for 10 to 100 m / min.
Reciprocating at a high speed, and at both ends of the reciprocating motion, traverse in the direction perpendicular to the reciprocating direction in a horizontal plane by a predetermined cutting amount, cut in the same plane at the same cutting depth, and then in the vertical direction The ball end mill 12 is vertically fed at a predetermined cutting depth, whereby a single small-diameter ball end mill rotates at high speed and reciprocates at high speed to form a three-dimensional shape.

That is, the single small-diameter ball end mill 12 is reciprocated at a high speed in the X-axis direction by the NC control device 20 and is laterally moved by a predetermined cutting amount in the Y-axis direction at both ends of the reciprocation. The same plane is cut at the same cutting depth, and then the ball end mill is fed longitudinally at a predetermined cutting depth in the Z-axis direction. In addition, since the cutting chips generated by the cutting process are in the form of powder, they can be easily processed by vacuum suction or an air blower.

According to this configuration, the NC data of the cutting is a system in which the surface to be cut is painted by reciprocating feed of one axis. This exactly matches the scanning program of the light beam in laser stereolithography, and the software can be used as it is. Further, NC data of cutting can be directly obtained in real time immediately from the three-dimensional CAD data of the mold surface. Therefore, according to the present invention, the time for obtaining NC data can be significantly reduced, and the problem of increasing NC data can be overcome.

Furthermore, since all surfaces of the mold are cut with only one tool, no error occurs due to tool change, and the problem of poor accuracy due to thermal deformation of the machine tool can be almost solved. Even if only one tool is used, any number of drilling operations associated with die machining can be performed by helical feed of a ball end mill.

FIG. 6 is a schematic view showing another embodiment of the high-speed cutting method for a mold according to the present invention. In this embodiment, before the high-speed reciprocating cutting in the same plane of the work 1, the same plane is cut at the same cutting depth along the contour line of the outer peripheral contour 2 at a relatively low feed rate, and then the high-speed cutting is performed. To perform reciprocating cutting 3. In other respects, it is the same as FIG. According to this method, since the cutting of the outer peripheral contour 2 is cut at a relatively low speed feed, it can follow NC data, and a program can be easily and automatically generated in real time. In addition, in the reciprocating machining 3 alone, the groove machining is performed as shown in FIG. 7A during the first pass, so that the tool load increases and high-speed feeding becomes difficult. By performing the machining 2 at a relatively low speed feed, the machining at the subsequent high speed feed is not groove machining as shown in FIG. 7B, so that the cutting load can be significantly reduced. Further, since the material is fed along the contour line of the outer peripheral contour 2, at least the circumferential surface roughness of the outer peripheral wall surface is greatly improved.
Also, to avoid overshoot due to rapid stop at high speed feed,
The effect of the tool stop position error can be eliminated.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention.

[0030]

As described above, the high-speed cutting method of the mold of the present invention and the ultra-high-speed milling apparatus using this method are as follows.
It solves various problems in conventional mold processing, and can greatly increase the rotation speed and feed rate of the cutting tool, thereby greatly reducing the mold processing time and enabling mold production and new product development. Not only can the lead time be shortened, but it can also greatly contribute to reducing die costs and improving die accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a cutting length and a wear amount when a cutting speed is changed.

FIG. 2 is a relationship diagram between a cutting length and a wear amount when a rotation speed of a tool is changed.

FIG. 3 is a schematic view showing a future prospect of milling.

FIG. 4 is an overall configuration diagram of an ultra-high-speed milling apparatus using the method according to the present invention.

FIG. 5 is a view schematically showing a high-speed cutting method of a mold according to the present invention.

FIG. 6 is a schematic view showing another embodiment of the high-speed cutting method of the mold according to the present invention.

FIG. 7 is a view showing a cutting area by a ball end mill.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Work 2 Outer contour cutting 3 Reciprocating cutting 10 Ultra-high-speed milling device 12 Small-diameter ball end mill 14 High-frequency motor 16 High-speed bearing (air bearing) 18 3-axis drive device 20 NC controller

Continuation of the front page (72) Inventor Hirotaka Matsuoka 2-1 Hirosawa, Wako-shi, Saitama Pref. RIKEN

Claims (4)

[Claims] 1. A single small-diameter ball end mill made of a tool material having high heat resistance is rotated at a high speed of 50 to 200,000 rpm, and the ball end mill is horizontally rotated at a speed of 10 to 100 m / m.
reciprocating at a high speed, and at both ends of the reciprocating motion, transversely moving by a predetermined cutting amount in a horizontal plane in a direction orthogonal to the reciprocating direction, cutting in the same plane at the same cutting depth, and then vertically The ball end mill is fed longitudinally at a predetermined cutting depth in the direction, whereby a three-dimensional shape is machined by high-speed rotation and high-speed reciprocation of a single small-diameter ball end mill. Method. 2. The method according to claim 1, wherein before the high-speed reciprocating cutting in the same plane, the same plane is cut at a relatively low speed feed along the contour line of the outer peripheral contour at the same depth of cut. The high-speed cutting method for a mold according to claim 1. 3. A single small-diameter ball end mill made of a tool material having high heat resistance, and the ball end mill having a diameter of 5 to 2 mm.
A high-frequency motor that rotates at a high speed of 100,000 rpm, a high-speed bearing that supports a ball end mill that rotates at a high speed, and a ball end mill that moves in three axial directions perpendicular to an X axis and a Y axis and a Z axis perpendicular to a horizontal plane. An axis control device, and an NC control device for numerically controlling the three-axis drive device, wherein the three-axis drive device has an X-axis only of 10 to 100 m / mi.
The ball end mill is reciprocated at a high speed in the X-axis direction by the NC controller, and is laterally moved by a predetermined cutting amount in the Y-axis direction at both ends of the reciprocation. Then, the same plane is cut at the same cutting depth, and then the ball end mill is longitudinally fed at a predetermined cutting depth in the Z-axis direction, whereby the single small-diameter ball end mill rotates at high speed and reciprocates at high speed. An ultra-high-speed milling device, characterized in that a three-dimensional shape is machined by the method. 4. The ultra-high-speed milling apparatus according to claim 3, wherein the high-speed reciprocating movement of the X axis is driven by a linear motor.