JP2000280121A - Screw cutting method and cutting device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve the efficiency of thread machining by interrupted cutting. SOLUTION: In a method of cutting a screw by moving a cutting tool 1 along an outer peripheral surface or an inner peripheral surface of a work material, a cutting tool 1 provided with a plurality of cutting blades 3 on an outer peripheral portion is provided at a center thereof. While rotating around the axis, the screw is revolved along the central axis of the peripheral surface on which the screw is machined, and further moved in the axial direction along the central axis of the revolution, and the rotational speed and the rotational speed of the tool 1 A screw is cut on the peripheral surface by setting the ratio of the number to 37 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a screw by cutting and a cutting apparatus used for executing the method.

[0002]

2. Description of the Related Art As a method for forming a screw, there are a method of turning using a lathe, a method of forming a screw between a die and plastic deformation by sandwiching a work material, or a method of rotating a grindstone having a sectional shape similar to a screw thread. A method of grinding a work material by pressing the work material against the work material is known. Among them, the method by rolling is not always high in accuracy, and there is a difficulty in manufacturing a small diameter screw. In addition, the grinding method using a grindstone can increase the precision of the screw. In that respect, it is excellent as a screw finishing process, but is not suitable for manufacturing a screw from a coarse material. In contrast, the turning method
There are advantages such as a high degree of freedom in processing and the possibility of processing screws with high precision.

One example is described in Japanese Patent Application Laid-Open No. 5-305501. The method described in this publication is a method for processing a female screw at an eccentric position of a work material, and a cutting tool such as a cutting tool such as a cutting tool that can rotate while holding the work material by a chuck and rotating the work material. By moving the cutting tool in the axial direction toward the work material, and moving the cutting tool in the radial direction to adjust the cutting amount,
This is a method of cutting a screw on a work material.

[0004]

The method described in the above-mentioned publication is a turning method for performing cutting by rotating a work material with respect to a cutting tool, which is a cutting tool.
Therefore, the cutting edge of the cutting tool is formed to have substantially the same shape as the cross section of the thread of the screw to be formed, and this is constantly applied to the work material to perform continuous cutting. Therefore, screws with relatively high precision can be machined, and various types of screws can be machined. However, since continuous cutting must be performed, the cutting speed is restricted in terms of the temperature of the cutting edge, the strength of the cutting edge, and the like, and as a result, it is difficult to improve the machining efficiency.

Further, according to the above-mentioned publication, the apparatus for carrying out the above method rotates a work material for machining a screw at an eccentric position, and rotates the work material with respect to the work material. The main shaft is configured to move in coordination with the X direction which is the radial direction and the Z direction which is the axial direction. Therefore, in order to perform screw processing by displacing the cutting edge position helically relative to the work material, the rotation of the work material, the rotation of the main shaft, and the movement of the main shaft in the radial direction are coordinated. Therefore, it is difficult to increase the processing speed due to restrictions such as control delay.

The present invention has been made in view of the above circumstances, and has as its object to perform threading by cutting with high efficiency.

[0007]

Means for Solving the Problems and Actions To achieve the above object, the invention of claim 1 is to cut a screw by moving a cutting tool along an outer peripheral surface or an inner peripheral surface of a work material. In the processing method, a cutting tool provided with a plurality of cutting blades on an outer peripheral portion is rotated around its central axis, and revolves along a central axis of a peripheral surface on which the screw is processed, and further, the center of the revolving center. The method is characterized in that the tool is moved in the axial direction along the axis, and a screw is cut on the peripheral surface by setting the ratio of the rotation speed and the revolution speed of the tool to 37 or less.

Therefore, according to the first aspect of the present invention, by rotating the tool, the cutting edge provided on the outer peripheral portion of the tool becomes intermittent cutting which sequentially acts on the work material, and the rotation speed and the revolution speed of the tool are reduced. Is 37 or less, and the revolution speed of the tool is high, so that the cutting amount or machining efficiency does not decrease even if the cutting width per tooth is reduced. In other words, the cutting width per blade can be reduced without lowering the machining efficiency, and accordingly, heat generation, cutting resistance, impact force, and the like can be reduced, so that the tool life can be improved. Further, the machining efficiency can be improved by increasing the amount of cutting per tooth within the range of the tool life.

According to a second aspect of the present invention, a cutting tool having a cutting edge on an outer peripheral portion is attached to a distal end portion, and a main shaft that rotates and revolves is moved in the axial direction thereof, so that the outer peripheral surface or the inner surface of the work material is moved. In a cutting device that cuts a screw on a peripheral surface, an eccentric shaft that rotatably holds the main shaft in a position deviated from the rotation center axis in parallel with the rotation center axis, and the eccentric shaft is deviated from the rotation center axis A revolving shaft that is rotatably held in a position parallel to the rotation center axis and is moved back and forth in the axial direction, a first drive mechanism that rotates the main shaft, and a rotation of the main shaft by rotating the eccentric shaft. A revolving radius changing mechanism for changing a distance from a center axis of the shaft, and displacing a cutting portion of the work material by the tool in a spiral shape by rotating the revolving shaft in relation to movement in the axial direction. And a second drive mechanism. Is a device which is characterized in that there.

Therefore, in the second aspect of the present invention, the main shaft on which the tool is mounted is rotatably held at the eccentric position of the revolving shaft. Therefore, the tool is rotated by rotating the main shaft and the revolving shaft respectively. The tool can be moved in the axial direction by freely setting the revolution speed of the tool at that time. As a result, it is possible to increase the amount of cutting per blade when the cutting position of the work material by the tool is helically moved in order to machine the screw, thereby performing high-efficiency cutting.

[0011]

Next, the present invention will be described in detail with reference to the drawings. First, an example of a cutting apparatus according to the present invention will be described. In FIG. 1, a tool 1 is a cutter for screw processing provided with a plurality of cutting blades 3 on an outer periphery of a tip portion of a shank 2. The blade 3 is formed in a contour having substantially the same shape as the cross section of the thread to be formed. A main shaft 4 on which the tool 1 is mounted at a distal end is disposed inside a holding shaft 5. The holding shaft 5 is a cylindrical shaft, and is integrated with a housing (that is, a base portion) 7 of the entire cutting device 6 shown in FIG. Therefore, although the holding shaft 5 is moved with respect to the work material (not shown), it does not rotate. The housing 7 is mounted on a column (not shown) and moves back and forth in the axial direction of the main shaft 4, so that the main shaft 4 moves in the axial direction.

A revolving shaft 8 is rotatably held by a bearing 9 inside the holding shaft 5. The revolving shaft 8 is formed with a hole which is eccentric with respect to its axis and extends in the axial direction, and an eccentric shaft 10 is rotatably held by a bearing 11 therein. Therefore, this eccentric shaft 10
Revolves around the axis of the revolving shaft 8 when the revolving shaft 8 rotates. The eccentric shaft 10 is for changing the orbital radius of the main shaft 4, and has a through hole formed eccentrically with respect to its axis and penetrating in the axial direction,
The main shaft 4 is rotatably held by the bearing 12 inside the through hole.

FIG. 2 schematically shows the relative positions of the above-described shafts in the radial direction.
Are arranged coaxially. An eccentric shaft 10 having an axis O10 at a position eccentric to the axis O8 of the revolution shaft 8 is disposed inside the revolution shaft 8. The main shaft 4 rotatably arranged inside the eccentric shaft 10 has an axis O of the eccentric shaft 10.
Eccentric to 10.

Therefore, when the eccentric shaft 10 is rotated, the main shaft 4 located at a position deviated from the axis O10 is moved to the axis O.
It moves on a circumference C10 centered at 10. If the amount of eccentricity of the eccentric shaft 10 with respect to the revolving shaft 8 is equal to the amount of eccentricity of the main shaft 4 with respect to the eccentric shaft 10, the axis O4 of the main shaft 4 coincides with the axis O8 of the revolving shaft 8, and the revolving shaft 8 May be zero. That is, the eccentric shaft 10
, The amount of eccentricity of the main shaft 4 disposed inside the main shaft 4 with respect to the revolution shaft 8 changes. And the revolving shaft 8
When the amount of eccentricity of the eccentric shaft 10 with respect to the eccentric shaft 10 is equal to the amount of eccentricity of the main shaft 4 with respect to the eccentric shaft 10, the amount of eccentricity of the main shaft 4 with respect to the revolving shaft 8 is limited to zero or more, up to twice the eccentric amount. Changes to

The tool 1 attached to the main shaft 4 rotates together with the main shaft 4, while the main shaft 4 is held inside the revolving shaft 8. Revolves around the axis O8 of the revolving shaft 8. The revolution radius in that case is the amount of eccentricity of the main shaft 4 with respect to the revolution shaft 8 set by rotating the eccentric shaft 10.

The right end of the revolving shaft 8 in FIG. 1 extends to the rear end of the housing 7 and is rotatably supported by the housing 7 via a bearing 13 fitted on the outer periphery thereof. I have. A through hole centering on the axis is formed in a portion on the rear end side of the revolving shaft 8, and the input shaft 14 is rotatably held in the through hole via a bearing 15. The input shaft 14 is for rotating the main shaft 4 and is provided with a main shaft motor M1.
It is connected to. The spindle motor M1 is fixed to a housing 7 as a base. The left end of the input shaft 14 in FIG. 1 extends inside the revolving shaft 8 to a position close to the rear end of the main shaft 4.

A plurality of rollers 16 having different outer diameters are arranged in contact with the end of the input shaft 14. These rollers 16 are rotatably mounted on support pins 17 mounted on the revolving shaft 8 so as to be parallel to the axis of the input shaft 14. Further, a cylindrical body 18 is fitted so as to cover the whole of the plurality of rollers 16. Each roller 16 is provided between the cylindrical body 18 and the input shaft 1.
4, and the contact pressure is high, so that the torque is transmitted by the frictional force.

The cylindrical body 18 covers the outer periphery of the rear end of the main shaft 4, and has a different outer diameter between the outer peripheral surface of the main shaft 4 and the inner peripheral surface of the cylindrical body 18 like the roller 16. A plurality of rollers 19 are press-fitted. A support pin 20 to which the roller 19 is rotatably mounted is connected to a ring-shaped gear 21 rotatably disposed on the outer peripheral side of the main shaft 4 via a bearing. Further, the ring gear 21 is connected to the rear end of the eccentric shaft 10 by a pin.

Therefore, the torque of the input shaft 14 is rotated by the rotation of the roller 16 which is in contact with the outer peripheral surface of the
The torque of the cylindrical body 18 is transmitted to the main shaft 4 by the rotation of a plurality of other rollers 19 in close contact with the inner peripheral surface thereof. That is, when the input shaft 14 is rotated by the motor M1, the torque is transmitted to the main shaft 4 and the main shaft 4 rotates. And each roller 16, 1
As the orbit 9 relatively revolves, the amount of eccentricity of the main shaft 4 with respect to the input shaft 14, that is, the orbital radius of the main shaft 4 is changed.

A plurality of cutouts penetrating the inner and outer peripheral surfaces of the revolving shaft 8 on the outer peripheral side of the ring gear 21 are formed, and the intermediate gear 22 meshed with the ring gear 21 is formed.
Are arranged in each notch. These intermediate gears 22
Are different from each other due to the fact that the thickness of the revolving shaft 8 in each portion where the is disposed is eccentric with respect to the axis of the revolving shaft 8 along the axial direction inside thereof. The outer diameter of each intermediate gear 22 differs in size according to the thickness of the revolution shaft 8 in each part. That is, the circle connecting the outermost peripheral portions of the intermediate gears 22 is configured to be a circle centered on the axis of the revolution shaft 8. Each intermediate gear 22 is rotatably supported by a support pin 23 attached to the revolution shaft 8.

Each intermediate gear 22 meshes with a revolution radius changing gear 24 which is an internal gear. The revolving radius changing gear 24 is formed on the inner peripheral surface at the tip of the cylindrical shaft 25. The cylindrical shaft 25 is arranged coaxially with the input shaft 14 on the outer peripheral side of the revolution shaft 8 and is rotatably held by a bearing 26.

A revolving shaft gear 27 is fixed to the outer peripheral portion of the revolving shaft 8 located on the outer peripheral side of the input shaft 14, and an intermediate shaft gear 28 disposed adjacent to the revolving shaft gear 27 is connected to the cylindrical shaft 25. It is fixed to. The revolving shaft gear 27 is
The input gear 30 of the differential mechanism 29 meshes with the output gear 31 of the differential mechanism 29.

Here, the differential mechanism 29 will be described.
The differential mechanism 29 is configured using a mechanism having the configuration shown in FIG. That is, in FIG. 3, teeth 101 such as splines are formed on the inner peripheral surface of the ring-shaped member 100, and a flexible ring 103 in which outer teeth 102 having a smaller number of teeth than the teeth 101 are formed is a ring-shaped member. Member 10
0 is rotatably arranged on the inner peripheral side. On the inner peripheral side of the flexible ring 103, an elliptical rotating member 104 is disposed via a bearing 105, and the flexible ring 103 is connected to the teeth 1 of the ring-shaped member 100 at both ends of its long diameter.
01 and are meshed. Therefore, in the mechanism shown in FIG. 3, since the number of teeth of the flexible ring 103 is smaller than the number of teeth of the ring-shaped member 100, the flexible ring 1
Even if the ring 03 is rotated once, the ring-shaped member 100 does not rotate once but the rotation angle is reduced by the difference in the number of teeth.

FIG. 4 is an exploded view schematically showing the differential mechanism 29. A pair of circular splines 32 and 33 corresponding to the above-mentioned ring-shaped member 100, and the flexible A flex spline 34 corresponding to the ring 103 and a wave generator 35 corresponding to an elliptical rotating member 104 fitted on the inner peripheral side thereof are provided. That is, a pair of cylindrical circular splines 32 and 33 having spline teeth formed on the inner peripheral surface,
Spline teeth meshing with the spline teeth of the circular splines 32 and 33 are formed on the outer peripheral surface, and a flex spline 34 which is a flexible cylindrical body and a ball bearing are fitted on the outer peripheral surface of the elliptical cam. The outer periphery of the ball bearing is provided with a wave generator 35 into which the flexspline 34 is fitted.

The number of teeth of one circular spline 32 and the number of teeth of flex spline 34 are equal (for example, 200
The circular spline 32 is fitted and fixed to the inner peripheral side of the input gear 30. On the other hand, the number of teeth of the other circular spline 33 is slightly larger than the number of teeth of the flex spline 34 (for example, to 202).
The circular spline 33 is fitted and fixed to the inner peripheral side of the output gear 31. Then, the wave generator 35 is fitted and fixed to the adjustment shaft 36,
The adjusting shaft 36 is connected to the radius changing motor M2. The radius changing motor M2 is fixed to a housing 7 corresponding to a base of the present invention.

Therefore, in this differential mechanism 29, when the input gear 30 is rotated with the wave generator 35, that is, the adjustment shaft 36 fixed, the number of teeth of the circular spline 32 and the number of teeth of the flexspline 34 fixed to the input gear 30 , The flex spline 34 rotates at the same speed as the input gear 30. On the other hand, since the number of teeth of the circular spline 33 fixed to the output gear 31 is larger than the number of teeth of the flexspline 34, the output gear 31 rotates at a reduced speed according to the difference in the number of teeth. In the above example, the number of teeth of the flexspline 34 is “200”.
In contrast, the number of teeth of the circular spline 33 is “20”.
2 ", the output gear 31 is 200/202 = 1.
It rotates at a speed reduced to 00/101.

As described above, a difference in the number of revolutions is generated. Even in such a case, the ratio of the number of teeth between the input gear 30 and the revolving shaft gear 27 and the output gear 3 are adjusted so that the revolution radius of the main shaft 4 does not change.
The gear ratio between 1 and the intermediate shaft gear 28 is set. As an example, when the number of teeth of the input gear 30 is “100” and the number of teeth of the revolution shaft gear 27 is “200”, the number of teeth of the output gear 31 is “101”, and the number of teeth of the intermediate shaft gear 27 is “20
0 ”. In such a configuration, the adjusting shaft 36 is set.
That is, for example, if the input gear 30 is rotated at 101 rpm while the wave generator 35 is fixed, the output gear 31 rotates at 100 rpm and the revolution shaft gear 27 rotates.
Rotates at 101/2 rpm. When the output gear 31 rotates at 100 rpm, the intermediate shaft gear 28 meshing with the output gear 31 becomes 100 × 101/200 = 101.
/ 2 rpm. That is, the revolution shaft gear 27 and the intermediate shaft gear 28 rotate at the same speed.

Therefore, the rotation speed of the revolving shaft 8 and the cylindrical shaft 25
Are equal to each other, the revolving radius changing gear 24 formed on the cylindrical shaft 25 and the intermediate gear 2 meshing therewith
2 and the ring gear 21 meshing therewith rotate integrally. That is, the phase of the rollers 16 and 19 in the revolving direction is kept constant.

On the other hand, since there is a difference in the number of teeth between the flexspline 34 and the circular spline 33 on the side of the output gear 31, the rotation of the flexspline 34 causes the circular spline 33 to decelerate. It depends on the number. In the above example, since the difference in the number of teeth is “2”, the circular spline 33 becomes 2/200 = 1/10 with respect to the rotation of the flexspline 34.
It is decelerated at a rate of zero. That is, when the flex spline 34 is rotated at 100 rpm together with the adjustment shaft 36, the circular spline 33 is relatively rotated at minus (-) 1 rpm. Since the circular spline 32 and the flexspline 34 on the input gear 30 side have the same number of teeth, there is no difference in the number of rotations. As a result, when the flexspline 34 is rotated together with the adjustment shaft 36, a difference occurs in the rotation phase between the input gear 30 and the output gear 31. That is, the input gear 30 is rotated at a rotation speed of 1/100 of the rotation speed of the adjustment shaft 36.
And the output gear 31 can generate a relative rotational movement.

Such a relative rotation appears as a relative rotation between the revolving shaft 8 and the ring gear 21, that is, a relative revolving speed of the rollers 16 and 19. And each roller 16,
Since the amount of eccentricity of the main shaft 4 with respect to the input shaft 14, that is, the orbital radius changes due to the relative revolution of 19, fine adjustment of the orbital radius can be easily performed in the above device. In FIG. 1, reference numeral 37 denotes a revolving gear, and the revolving gear 37 meshes with the input gear 30. A revolving motor M3 is connected to the revolving gear 37. The revolving motor M3 is fixed to a housing 7 corresponding to a base of the present invention. In addition, the above-described orbital radius changing motor M2, the differential mechanism 29, and a system for transmitting torque from the differential mechanism 29 to the revolving shaft 8 and a system for transmitting torque from the differential mechanism 29 to the eccentric shaft 10 are revolved. This constitutes a radius changing mechanism.

In the cutting apparatus shown in FIG. 1, the revolving motion of the main shaft 4 is not achieved by a combination of linear motions in two-dimensional directions, but by the rotation of a revolving shaft 8 having the main shaft 4 built therein. Therefore, the spindle 4 can rotate and revolve at high speed. Also, in the above example,
Since the amount of eccentricity of the main shaft 4 with respect to the revolution shaft 8 can be changed by the rotation of the eccentric shaft 10, the radius thereof can be changed during the revolution.

The transmission system for the torque from the spindle motor M1 to the spindle 4 corresponds to the first drive mechanism of the present invention, and the transmission system for the torque from the revolution motor M3 to the revolution shaft 8 is the same. A mechanism that corresponds to the second drive mechanism of the present invention and that combines these two transmission mechanisms constitutes a rotary drive mechanism.

Next, a method of cutting a screw by the above-mentioned cutting device 6, that is, an example of the method of the present invention will be described. Since the tool 1 attached to the main shaft 4 has the cutting edge 3 having substantially the same contour as the cross-sectional shape of the thread to be formed, as shown in FIG. By pressing against the work material 41, the cutting edge 3
Thus, the same groove shape as that shape is formed on the work material. In this case, since the tool 1 is provided with a plurality of cutting edges 3 on the outer peripheral portion, by rotating the tool 1 together with the main shaft 4, the cutting edges 3 sequentially act on the work material. Become.

Further, since the main shaft 4 is rotatably held at the eccentric position of the revolution shaft 8, when the revolution shaft 8 is rotated,
The tool 1 revolves around the axis of the revolving shaft 8 together with the main shaft 4. As a result, as shown in FIG. 6, the cutting blade 3 moves while drawing a loop-like trajectory. In FIG. 6, reference numeral 40 indicates a processing hole in which a screw is to be processed. Therefore, the cutting speed by the cutting edge 3 is a speed obtained by adding the peripheral speed of the tool 1 by the rotation and the moving speed by the revolution.

The locus of movement of the cutting edge 3 due to the revolution of the tool 1 is a locus along the machining hole 40 of the work material 41. Therefore, as the revolving speed is relatively large, the cutting edge 3 moves every time. Therefore, the time or distance acting on the work material 41 becomes longer. In this way, the cutting length of the cutting blade 3 is increased once for each operation of the workpiece, so that the maximum cutting area can be reduced without reducing the cutting amount. In addition, the impact force or the cutting load applied to the cutting blade 3 by the intermittent cutting is suppressed, so that the tool life can be extended.

In the above-described cutting apparatus 6 according to the present invention, the revolving of the main shaft 4 and the tool 1 attached thereto is performed by revolving the revolving shaft 8 which holds the main shaft 4 so as to be rotatable. 1 to increase the number of revolutions, the ratio to the number of revolutions (number of revolutions / number of revolutions =
K) can be set arbitrarily. FIG. 7 is a diagram showing the results of measuring the relationship between the rotation / revolution ratio K and the processing efficiency. Here, the processing efficiency is a cutting volume (cc) per unit time (min), and is a measurement result when a hole having an inner diameter of 55 mm is cut at a cutting speed of 200 m / min and a cutting width of 0.6 mm. The used tools are an end mill having an outer diameter of 20 mm and an end mill having an outer diameter of 50 mm.

As shown in FIG. 7, when the revolution / revolution ratio K is smaller, the machining efficiency increases as the revolution / revolution ratio K becomes smaller. When the revolution / revolution ratio K becomes less than "37", the increasing tendency becomes remarkable. In particular, if it is not more than "20", it is possible to obtain a processing efficiency twice or more as high as the processing efficiency when the conventional rotation / revolution ratio K is set to about "100". In addition,
In FIG. 7, the machining efficiency when the rotation / revolution ratio K is "1" indicates the machining efficiency of boring, which is continuous cutting.

As described above, the cutting speed in the contouring process is the sum of the rotation speed of the cutting blade due to the rotation of the tool and the feed speed of the cutting blade due to the revolution. In the above-described cutting device according to the present invention, Since there is no restriction on the number of revolutions,
Increase the feed speed of the cutting blade due to revolution. In particular,
In the present invention, the cutting speed is set so that the ratio of the speed due to the revolution of the tool is 7% or more. This may be set by changing the revolution radius or the revolution speed.

In the contouring process in which the tool rotates and revolves, the tool is fed by a predetermined dimension while the cutting edge makes one revolution, so that the trajectory of the cutting edge follows the inner peripheral surface of the machining hole 40 as shown in FIG. Loops. As a result, there is a portion where the tool is fed while the cutting blade is not acting on the work material, and this portion becomes a so-called uncut portion and projects toward the center of the machining hole 40. The height H can be used as an index of the processing accuracy. FIG. 8 shows the result of measuring the relationship between the rotation / revolution ratio K and the processing accuracy H (μm).
The cutting conditions under which this measurement was performed were as follows:
m, cutting speed 200 m / min, cutting width 0.6 mm. The tools used were eight blades with an outer diameter of 20 mm, 16 blades with an outer diameter of 20 mm, eight blades with an outer diameter of 50 mm, and an outer diameter of 50.
mm end mills with 16 blades.

As described above, while rotating and revolving the tool 1, the spindle 4 is moved relative to the workpiece 41 in the axial direction of the spindle 4 in relation to the revolution speed (the revolution speed of the revolution shaft 8). That is, the entire cutting device 6 is advanced with respect to the workpiece 41. As a result, since the tool 1 advances in the axial direction while revolving, the cutting point of the cutting edge 3 is displaced in both the circumferential direction and the axial direction, and helical cutting is performed. That is, cutting of a screw having a lead angle determined by the revolution speed of the main shaft 4 and the feed speed in the axial direction is performed.

When a screw is formed on the inner peripheral surface of the processing hole 40, first, rough cutting is performed, and then finish cutting is performed. That is, at the time of the first cutting in which the main shaft 4 and the tool 1 are advanced in the axial direction, the orbital radius is set so that the revolving radius of the cutting edge is slightly smaller than the diameter of the screw to be machined, that is, the finishing margin remains. Set. This is performed by driving the radius changing motor M2 to rotate the eccentric shaft 10 relatively to the revolution shaft 8. After the tool 1 is moved forward together with the main shaft 4 to perform rough machining, the radius changing motor M2 is further driven to slightly increase the revolution radius of the tool 1, and in this state, the tool 1 is rotated and revolved in the axial direction. The screw is finished by moving it backward. In the case of the finish machining, the revolution speed of the tool 1 is set smaller than that in the case of the rough machining, and the rotation / revolution ratio K is increased. By doing so, the processing accuracy H described above becomes a small value, and the processing surface accuracy increases.

[0042]

As described above, according to the first aspect of the present invention, by rotating the tool, the cutting edge provided on the outer peripheral portion of the tool becomes intermittent cutting in which the cutting material sequentially acts on the work material. Since the ratio between the number of revolutions and the number of revolutions is 37 or less, and the number of revolutions of the tool is high, the cutting amount or machining efficiency does not decrease even if the cutting width per tooth is reduced. In other words, without reducing the processing efficiency,
Since the cutting width per tooth can be reduced and the heat generation, cutting resistance, impact force, etc. can be reduced accordingly, the service life of the tool can be improved. By increasing the amount of cutting, the machining efficiency can be improved.

According to the second aspect of the present invention, since the main shaft on which the tool is mounted is rotatably held at the eccentric position of the revolving shaft, the tool is rotated by rotating the main shaft and the revolving shaft respectively. Revolves while rotating, and at that time, the revolving speed of the tool can be freely set and the tool can be moved in the axial direction. As a result, the cutting position of the work material by the tool can be set to process the screw. By increasing the amount of cutting per blade when moving spirally, high-efficiency cutting can be performed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of the device of the present invention.

FIG. 2 is a view for explaining relative positions of a main shaft, an eccentric shaft, a revolving shaft, and a holding shaft in a radial direction.

FIG. 3 is a mechanism diagram for explaining a basic mechanism used for a differential mechanism.

FIG. 4 is an exploded schematic view showing components of a differential mechanism.

FIG. 5 is a schematic cross-sectional view for explaining a cutting state of a screw.

FIG. 6 is a diagram showing a locus of a cutting edge according to the method of the present invention.

FIG. 7 is a diagram showing a result of measuring a relationship between a rotation / revolution ratio and a processing efficiency.

FIG. 8 is a diagram showing the result of measuring the relationship between the rotation / revolution ratio and the processing accuracy.

[Description of Signs] 1 ... Tool, 3 ... Cutting Edge, 4 ... Spindle, 6 ... Cutting Device, 8 ... Revolving Shaft, 10 ... Eccentric Shaft, M1 ... Spindle Motor, M3 ... Revolving Motor, 40 ... Working Hole , 41 ...
Work material.

Claims (2)

[Claims] 1. A method for cutting a screw by moving a cutting tool along an outer peripheral surface or an inner peripheral surface of a work material, wherein the cutting tool is provided with a plurality of cutting blades on an outer peripheral portion. While rotating around the center, the screw is revolved along the central axis of the peripheral surface to be machined, and further moved in the axial direction along the central axis of the revolution, and the rotation speed and the revolution speed of the tool are compared with each other. A method of cutting a screw, comprising setting the ratio to 37 or less and cutting the screw on the peripheral surface. 2. A cutting tool having a cutting edge on an outer peripheral portion is attached to a tip portion, and a main shaft that rotates and revolves is moved in the axial direction to cut a screw on an outer peripheral surface or an inner peripheral surface of a work material. An eccentric shaft that rotatably holds the main shaft at a position deviated from the rotation center axis in parallel with the rotation center axis, and a rotation center axis at a position deviated from the rotation center axis. A revolving shaft that is held rotatably in parallel and is moved back and forth in the axial direction; a first drive mechanism that rotates the main shaft; and a distance from the central axis of the revolving shaft of the main shaft that rotates the eccentric shaft. And a second drive mechanism for helically displacing a cutting position of the work material by the tool by rotating the revolving shaft in relation to movement in the axial direction of the revolving shaft. Is characterized by Cutting device of the screw.