JP7013195B2 - Finishing method - Google Patents

Description

The present invention relates to a work finishing method for machining a workpiece (hereinafter referred to as a work) that rotates around an axis using a machining center with a rotary tool that rotates around the axis.

In recent years, while machining with multi-axis machines (including 5-axis machines) has become widespread, the roughing and finishing processes of workpieces are still performed by turning, using lathes and the like as general workpiece machining processes. After that, the setup is changed to a machining center or the like, and a cutting process is performed by the machining center or the like. In this way, it was inevitable to change the setup when processing one work.

In such a machining process, the rotary table mounted on a machining center or the like is used to continuously rotate the attached work at a rotation speed that can withstand the cutting force, and the attached work is indexed to an arbitrary angle. It has been used for fixed holding purposes.

On the other hand, if the rotary table invented by the applicant described in Patent Document 1 is used for the machining center, the work can be rotated at a high speed comparable to that of a lathe. It can be integrated and can be processed only with an existing machining center without purchasing expensive multi-tasking machines and lathes, without changing the setup.

Japanese Unexamined Patent Publication No. 2015-174187

However, with the rotary table of Patent Document 1, although it is possible to realize the machining accuracy equivalent to rough machining by a lathe, it is not possible to obtain a good machined surface equivalent to finish machining.

This is because, in general, the tool of the machining center uses an end mill, and when the work is machined with this end mill, it will be cut intermittently when viewed from the work due to the structure of the cutting edge, and the machined surface will be scaled. It will be finished in the shape. Therefore, it is not possible to obtain a mirror-like finish as in the finishing process.

Therefore, if a rotary tool of a well-known technique is used, it is possible to continuously cut when viewed from the work due to the structure, so that a better machined surface can be obtained than roughing.
However, although a rotary tool can obtain a better machined surface than rough machining, it is not possible to obtain a machined surface with high accuracy such as finish machining depending on the machining conditions.

Therefore, an object of the present invention is to control a peripheral speed of a rotary tool and a work and to control a cutting position without adding equipment even in machining by a machining center to obtain a good machined surface. The purpose is to provide a finishing method.

In order to solve the above problems, the work finishing method of the present invention is orthogonal to three orthogonal axes, one rotating axis for rotating a rotary table on which the work is placed, and a rotary tool for cutting the work while rotating. Using a machining center equipped with a numerical control device that drives and controls three axes, the relationship between the peripheral speed α of the rotary tool and the peripheral speed β of the work is set to α> β, including the work central axis and the cutting point of the round piece insert. It is characterized in that an angle γ formed by a horizontal axis orthogonal to the center axis of the work is provided, and cutting is performed while pressing one of the work and the round piece insert against the other.

According to the above procedure, the turning process can be performed only by the machining center and the rotary table mounted on the machining center, and good machining accuracy can be obtained. In addition, it is not necessary to change the setup for transferring to another machine, and it is possible to reduce the cost due to the addition of equipment.

Further, in the work finishing method of the present invention, it is preferable to control the rotation direction of the rotary tool so as to be an upcut according to the movement direction of the three orthogonal axes. According to the above procedure, the processing accuracy can be further improved. Further, as will be described in detail later, resistance is applied from the portion where the chips are thin to the portion where the chips are thick, so that the cutting can be performed more smoothly.

Further, in the work finishing method of the present invention, it is preferable that the rotation axis 1 is arranged so that the axis line and the axis line of the rotary tool are perpendicular to each other. According to the above procedure, the rotary tool does not need to be tilted with respect to the axis, and the work does not need to be tilted with respect to the axis. Therefore, the machine configuration itself becomes a simple configuration and also in machining. It is possible to obtain a machined surface with high accuracy without performing a complicated machining program.

Further, in the work finishing method of the present invention, it is preferable to use a dry method that does not use cutting oil. According to the above procedure, since cooling by cutting oil is not performed, it is possible to reduce the strength of the work by increasing the amount of heat generated by friction. As a result, the cutting resistance is reduced, so that the rotary table can be machined with a small load. Therefore, stable machining is possible, and a machined surface with high accuracy can be obtained.

Further, in the work finishing method of the present invention, it is preferable that the angle γ is determined according to the amount of deflection of the rotary tool during machining. According to the above procedure, a machined surface with high accuracy can be obtained.

Further, in the work finishing method of the present invention, the amount of deflection causes the rotary tool to bend the rotary tool corresponding to the cutting resistance (hereinafter referred to as the component force a) and the reaction force due to the cutting. It is preferable that the component force (hereinafter referred to as component force b) is determined to be balanced. According to the above procedure, a machined surface with high accuracy can be obtained.

According to the work finishing method of the present invention, a good machined surface can be obtained by controlling the peripheral speed of the rotary tool and the work and controlling the cutting position without adding equipment even in machining by a machining center. Can be done.

It is a schematic perspective view for demonstrating the finishing processing method of the work by one Embodiment of this invention. It is an enlarged view of a rotary tool, (a) is a front view, and (b) is a bottom view, respectively. It is a front view at the cutting position of a round piece insert and a work. It is a graph which showed the relationship between a round piece insert and cutting resistance. It is a graph which showed the relationship between a round piece insert and a cut amount error. It is a graph which showed the relationship between a round piece insert and surface roughness.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. Further, it can be appropriately changed as long as it does not deviate from the range in which the effect of the present invention is exhibited. It should be noted that FIGS. 1 to 4 described later show the x-axis, the y-axis, and the z-axis. The orientations of the x-axis, y-axis, and z-axis are aligned with each other even in different figures. In the description of the present specification, for convenience, the positive side in the x-axis direction is the "right" side, the negative side in the x-axis direction is the "left" side, the positive side in the y-axis direction is the "front" side, and the negative side in the y-axis direction is the "rear" side. The side, the positive side in the z-axis direction is the "upper" side, and the negative side in the z-axis direction is the "lower" side.

FIG. 1 is a schematic perspective view for explaining a method of finishing a work according to an embodiment of the present invention.
As shown in FIG. 1, the basic configuration of the machining center 100 has three orthogonal axes in combination with the table base 10 and the tool spindle 20, and the numerical control device 40 for controlling the movement of these axes and the rotation of the tool spindle 20 and the like. It is composed of such things.
The configuration will be described below while showing an example of the three orthogonal axes.

The tool spindle 20 can be moved one-dimensionally in the vertical direction (z-axis direction) with respect to the table base 10, and is around the axis A at a constant rotation speed β, in the direction of arrow a1 or in the direction of a2. It is rotatable to.
A rotary tool 23 including a shank portion 21 and a round piece insert 22 is attached to the tip of the tool spindle 20, and the shank portion 21 has a columnar shape and is rotationally integrated with the tool spindle 20. In addition, the axis A of the tool spindle 20 and the axis of the shank portion 21 are attached so as to coincide with each other.

Similarly, the round piece insert 22 is rotationally integrated with the tip of the shank portion 21 and is attached so that the axis A and the axis of the round piece insert 22 coincide with each other.

(Round piece insert)
As shown in FIG. 2, the round piece insert 22 has a circular shape when viewed in a cross section orthogonal to the axis A, and the intersection of the tip surface 22a and the side surface 22b is a cutting edge 22c.

The table base 10 can be moved two-dimensionally in the front-rear direction (y-axis direction) and the left-right direction (x-axis direction) with respect to the tool spindle 20.
A rotary table 30, which is one axis of rotation, is mounted on the table stand 10 so as to be movable and integrated with the table stand 10.
The rotary table 30 is preferably mounted so that the axis B of the rotary table 30 and the axis A of the rotary tool 23 are perpendicular to each other.

The numerical control device 40 mainly controls the moving directions of the three orthogonal axes composed of the tool spindle 20 and the table base 10, and also controls the rotation direction and the rotation speed of the tool spindle 20.
The numerical control device 40 cuts the end face of the work by controlling the rotation direction of the round piece insert 22 so as to be an upcut described later according to the movement direction of the three orthogonal axes. This makes it possible to obtain a good machined surface.

(Rotary table)
A chuck (not shown) is fixed to the rotary table 30, and the work w is gripped by driving the chuck (not shown).
A servomotor (not shown) is mounted inside, which enables the workpiece to be rotationally driven.

Further, a control device 50 for controlling the rotation speed, the rotation direction, and the like is connected.
In other words, by driving the rotary table 30 by the control device 50, the work w can be rotated around the axis B of the rotary table 30 in the arrow b1 direction or the b2 direction at a constant rotation speed α.

(Example 1)
The present inventor has evaluated the relationship between the cutting resistance, the depth of cut error, and the surface roughness with respect to the round piece insert by using the processing device, the processing procedure, the processing position, and the processing conditions below.

<Processing equipment>
As the processing apparatus, a commercially available 3-axis machining center (VERTICAL CENTER NEXUS 430B-2 HS manufactured by Yamazaki Mazak Corporation) was used, and a circular table developed by the present applicant was mounted on the table stand.
The spindle of the machining center can rotate up to 18000 min ^-1 , the table size is 1100 mm in length in the x-axis direction and 430 mm in length in the y-axis direction, and a round piece insert is attached to the spindle.
The circular table used was one that could rotate up to 1000 min ^-1 .

<Processing procedure>
The machining operation in the first embodiment will be described with reference to FIG.
First, the round piece insert 22 is moved to a predetermined machining position along the z-axis, and is held immovably at that position. Next, the table base 10 is relatively moved to the machining position with respect to the round piece insert 22 along the x and y axes. In this state, the circular table 30 is rotated at a predetermined rotation speed so as to have a constant speed, and the work w is rotated around the axis B in the direction of the arrow b1.

Then, the tool spindle 20 of the machining center 100 is rotated at a predetermined rotation speed so as to have a constant speed, and the round piece insert 22 is rotated around the axis A in the direction of arrow a2.
At this time, the work w and the round piece insert 22 may be rotated at the same time, or may be moved while rotating to a predetermined machining position.

In this state, by moving the table base 10 to the left along the x-axis, cutting is performed while pressing one of the work w and the round piece insert 22 against the other.

For convenience, when the table base 10 moves to the left as described above, the round piece insert 22 rotates around the axis A in the direction of arrow a2, so that the blade of the round piece insert 22 hits the cut portion and is scraped up. Processing while processing is defined as upcut.

On the other hand, cutting is defined as cutting by moving the table base 10 to the left side and rotating the round piece insert 22 around the axis A in the direction of the arrow a1.
The relationship between the peripheral speed α of the round piece insert 22 and the peripheral speed β of the work w was set to α> β.

<Processing position>
The machining position in the first embodiment will be described with reference to FIG. FIG. 3 shows a front view of the round piece insert 22 and the work w at the cutting position.

As shown in FIG. 3, a cutting resistance M due to machining acts on the rotary tool 23 (round piece insert 22 and shank portion 21), and a component force m for rotating the rotary tool 23 is generated. Further, when the round piece insert 22 is cut into the work w, a reaction force N is generated due to the cut, and a component force n is generated to rotate the rotary tool 23.

The offset angle γ is appropriately determined so that the forces of the component force m and the component force n are balanced.
The position where the offset angle γ is provided from the horizontal axis including the work center axis and orthogonal to the work center axis is defined as the cutting position.

With this offset angle γ, the deflection of the rotary tool 23 can be minimized, and a machined surface with high accuracy can be obtained.
Since an appropriate value of the offset angle γ changes depending on the rigidity of the rotary tool 23, the depth of cut of the round piece insert 22, the work material, and the like, the offset angle γ is appropriately determined according to the machining conditions.

<Processing conditions>
The processing conditions in Example 1 are shown in Table 1 below.

As shown in Table 1, the main processing conditions are the processing method, round piece insert diameter, work material, work peripheral speed β, feed amount per work rotation, cutting amount, round piece insert rotation speed, round piece insert peripheral speed. Of the 9 items of α and the offset angle γ, 6 items were fixed, and the round piece insert rotation speed (round piece insert peripheral speed α) and the offset angle γ were changed for verification. Then, the cutting resistance, the depth of cut error, and the surface roughness were measured when the round piece insert rotation speed (min ^-1 ) was set to 750, 1500, 3000, and 4500, respectively.

Further, under the present machining conditions, the work diameter φ130 is initially used, and the rotation speed of the circular table is calculated so that the work peripheral speed is 150 (m / min) with respect to the work diameter. The rotation speed of the circular table at that time was about 367 (min ^-1 ). Then, in the next verification, one work was used. That is, the diameter is reduced depending on the depth of cut, but each time the reduced work diameter is measured at the next verification, the rotation speed is calculated and verified so that the work peripheral speed is 150 (m / min). is doing.
In addition, the processing environment for processing was a dry method that does not use cutting oil.

FIGS. 4 to 6 show the relationship between the cutting resistance, the depth of cut error, and the surface roughness with respect to the round piece insert, respectively.

<Relationship with cutting resistance>
FIG. 4 is a graph showing the relationship between the round piece insert and the cutting resistance.
From FIG. 4, regardless of the offset angle γ, No. In Nos. 1 to 4, the cutting resistance becomes low when the round piece insert rotation speed becomes larger than 3000 (min ^-1 ).
It is considered that the reason is that heat is generated due to friction at the cutting point between the round piece insert and the work, the strength of the work is lowered, and the cutting resistance is reduced.
Here, the relationship between the round piece insert rotation speed, the round piece insert peripheral speed, and the work peripheral speed is shown in Table 2 below.

From Table 2, the round piece insert peripheral speed becomes larger than the work peripheral speed of 150 (m / min) when the round piece insert rotation speed is 3000 (min ^-1 ) or more.
That is, it can be said that the cutting resistance is low when the relationship between the round piece insert peripheral speed α and the work peripheral speed β is α> β.

<Relationship with depth of cut error>
FIG. 5 is a graph showing the relationship between the round piece insert and the depth of cut error.
The depth of cut error g referred to here is the processing by arranging the round piece inserts so as to have the set depth of cut e (0.2 mm in the first embodiment) with the outer circumference of the work as a reference. Later, the work diameter is measured to calculate the actual depth of cut f, and the value of the difference is referred to.

That is, the depth of cut error g was defined as follows.
Cut amount error g = Actual cut amount f-Set cut amount e

Considering, No. In No. 1, the component force n of the reaction force N generated by the notch shown in FIG. 3 exceeds the component force m of the cutting resistance M, and the notch is insufficient.
No. In 3 and 4, No. Contrary to 1, the component force m exceeds the component force n, and the depth of cut increases.
No. In 2, the component force m and the component force n are balanced. Therefore, the depth of cut error is extremely small.

As a result, in the first embodiment, No. It can be seen that the offset angle γ = 5 ° of 2 is a condition for obtaining good accuracy.

<Relationship with surface roughness>
FIG. 6 is a graph showing the relationship between the round piece insert and the surface roughness.
As shown in FIG. 6, when the round piece insert rotation speed becomes larger than 3000 min ^-1 , No. The surface roughness of 2 is improved.

The reasons are that the cutting resistance is reduced by making the round piece insert peripheral speed larger than the work peripheral speed, and that the offset angle γ is set appropriately (here, 5 °), and the amount of deflection of the tool is small. It is considered that the surface roughness was improved by this.

From the above verification results, according to the relationship between the round piece insert and the cutting resistance, when the peripheral speed of the work exceeds the peripheral speed of the round piece insert, the cutting resistance decreases and the load on the circular table can be reduced. Do you get it.

Then, according to the relationship between the round piece insert and the depth of cut error, if the offset angle γ is set so as to have an appropriate amount of deflection (balance between the component force m and the component force n), the accuracy of the depth of cut is improved. I found that I could.

Further, according to the relationship between the round piece insert and the surface roughness, the peripheral speed of the round piece insert exceeds the peripheral speed of the work, and the amount of deflection (balance between the component force m and the component force n) is obtained. It was found that if the offset angle γ is set to, it is possible to obtain a machined surface with high accuracy at the finishing machined level.

That is, even in machining by a machining center, a good machined surface can be obtained by controlling the peripheral speeds of the rotary tool and the work and controlling the cutting position without adding equipment. In other words, the turning process can be performed only with the machining center and the rotary table mounted on the machining center, and good machining accuracy at the finishing machining level can be obtained. In addition, it is not necessary to change the setup for transferring to another machine, and it is possible to reduce the cost due to the addition of equipment.

In addition, by making an upcut, resistance is gradually applied to the round piece insert from the part where the chips are thin to the part where the chips are thick, and it can be cut smoothly, and the part where the chips after processing are thin is still cut. Because of the beginning, the heat generation temperature of the round piece insert due to cutting is small, and the heat generation temperature of the round piece insert increases as the chips become thicker. Can be processed.

In addition, since the rotary tool does not need to be tilted with respect to the axis and the workpiece does not need to be tilted with respect to the axis, the machine configuration itself becomes a simple configuration and complicated machining is performed. A machined surface with high accuracy can be obtained without programming.

Further, since cooling by cutting oil is not performed, it is possible to reduce the strength of the work by increasing the amount of heat generated by friction. As a result, the cutting resistance is reduced, so that the rotary table can be machined with a small load. Therefore, stable machining is possible, and a machined surface with high accuracy can be obtained. Further, since the coolant water, the coolant tank, the coolant pump, the coolant hose, the nozzle, the solenoid valve and the like are not required, the cost can be reduced accordingly.

Although the present invention has been described above in terms of preferred embodiments, such a description is not a limitation, and of course, various modifications can be made. In the above embodiment, the relative movement of the work with respect to the rotary tool has been described, but the present invention is not limited to this, and the work may move in the x-axis direction, the rotary tool may move in the y and z axes, and the work may move in the y-axis. It may move in the direction and the rotary tool may move on the x and z axes, and is not limited to this.

In addition, the machining center was described in the vertical shape (the tool spindle is in the vertical direction), but the machining center is not limited to the horizontal shape or the portal shape. In the case of the horizontal machining center, the circular table is placed horizontally (the rotation axis is parallel to the z axis). ) Is even better.

In addition, the numerical control device of the machining center controls the three orthogonal axes, and the control device of the circular table controls the one axis of rotation. Not limited to this, the numerical control device of the machining center controls the one axis of rotation of the circular table. It doesn't matter.

Further, the measurement was performed under the processing conditions shown in Table 1, but the measurement is not limited to this, and may be appropriately changed depending on the work material and the work diameter.

Further, the processing environment is not limited to the dry type, and may be a wet type using cutting water or a semi-wet type between the dry type and the wet type.

Further, the work is not limited to a cylinder, but may be a cylinder or a prism, and the shape of the work is not limited.

Further, the servo motor mounted on the circular table is not limited to this, and may be a DD motor or the like.

10 Table stand 20 Tool spindle 21 Shank part 22 Round piece insert 23 Rotating tool 30 Round table 40 Numerical control device 50 Control device 100 Machining center α, β Circumferential speed γ Angle A, B Axis line a1, a2, b1, b2 Rotation direction m, n component w work

Claims (4)

Three orthogonal axes, one rotating axis that rotates the table on which the work is placed, and
A rotary tool that cuts the work while rotating, and
Using a machining center equipped with a numerical control device that drives and controls the three orthogonal axes,
The rotation axis 1 is arranged so that the axis line and the axis line of the rotary tool are perpendicular to each other.
The relationship between the peripheral speed α of the rotary tool and the peripheral speed β of the work is α> β, and the angle formed by the plane including the central axis of the work and the cutting point of the rotary tool with respect to the horizontal plane is γ. age,
The angle γ is such that the component force (m) for rotating the rotary tool corresponding to the cutting resistance (M) and the component force (n) for rotating the rotary tool corresponding to the reaction force (N) due to cutting are balanced. West,
A work finishing method characterized by cutting while pressing one of the work and the rotary tool against the other. In the work finishing method according to claim 1,
A work finishing method, characterized in that the rotation direction of the rotary tool is controlled so as to be an upcut according to the movement direction of the three orthogonal axes. In the work finishing method according to claim 1 or 2 .
A work finishing method characterized by a dry method that does not use cutting oil. In the work finishing processing method according to claims 1 to 3 ,
A method for finishing a work, wherein the angle γ is determined according to the amount of deflection of the rotary tool at the time of machining.

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