JP3275599B2 - Cutting method using rotary cutting tool - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting method in which a rotary cutting tool which is intermittently cut by being rotationally driven about an axis is sequentially moved to a plurality of tool points to perform cutting. In particular, the present invention relates to a rotary cutting method capable of obtaining high dimensional accuracy with as few tool points as possible.

[0002]

2. Description of the Related Art When a rotary cutting tool which is intermittently cut by a cutting edge by being rotationally driven around an axis is sequentially moved to a plurality of tool points to perform predetermined cutting on a workpiece, NC (Numerical control) Machine tools are widely used,
The plurality of tool points are set in advance as NC data. For example, when cutting a smooth free-form surface using a ball end mill whose cutting edge follows a hemispherical trajectory by being rotationally driven around the axis, "TO
As described in “YOTA Technical Review Vol. 41, No. 1 Reprint” (Toyota Motor Co., Ltd. issued in May 1991), the tool point is determined by the polyhedral approximation method or the inverse offset method. Normally, basically, (1) offset the free-form surface by the tool radius,
(2) The curve is approximated by a broken line, assuming the linear interpolation function of the NC. When approximating a polygonal line, the maximum value of the difference between the curve and the straight line is called tolerance, which is an accuracy index when creating NC data. The NC data increases as the tolerance decreases.

[0003]

The surface to be cut by the rotary cutting tool for interrupted cutting is not a smooth continuous surface, but a scale-like surface with irregularities due to the tooth mark of the tool.
The cutting of a free-form surface by a ball end mill is no exception, and is a discontinuous surface in which a large number of trochoidal surfaces (spheroidal approximation is also possible). The unevenness due to the tooth mark is called a cusp. When a free-form surface is cut based on NC data based on linear interpolation, a shape error due to tolerance and a shape error due to the cusp are superimposed on the obtained workpiece. Included.

However, in the conventional cutting method,
Since the cusp is not considered in association with the tolerance when setting the cutting conditions, there have been problems such as an increase in overall shape error and generation of more NC data than necessary. This increase in the shape error requires a large number of man-hours for operations for approaching the desired shape, such as polishing in a post-process. In addition, an increase in the amount of NC data lowers the feed speed, and causes an increase in processing time.

The present invention has been made in view of the above circumstances, and has as its object to minimize N
An object of the present invention is to provide high dimensional accuracy with the C data amount, that is, the number of tool points.

[0006]

In order to achieve the above object, the correlation between the shape error due to tolerance and the shape error due to a cusp is taken into consideration to minimize the overall shape error and to reduce the tool point. In the first invention, a rotary cutting tool that is intermittently cut by a cutting edge by being rotationally driven about an axis is sequentially moved to a plurality of tool points relatively, so that in cutting method of forming a target machining surface line a predetermined cut into,
The rotary cutting tool is rotated by a rotation angle of approximately one blade between the plurality of tool points, and the tip of the cutting edge of the rotary cutting tool is positioned around the tool axis near the tool point.
In this case, the cutting point is located at the cutting point on the target processing surface .

[0007]

In the cutting method using such a rotary cutting tool, the rotary cutting tool is rotated by a rotation angle of approximately one blade between a plurality of tool points, so that the tolerance is substantially minimized and the tool point is reduced. Is minimized. FIG. 1 is a schematic diagram in the case of cutting a target processing surface S having a gentle curvature. In FIG. 1, “feed f of one blade” is a dimension between cutting points intermittently cut by a cutting edge. When the rotation speed and the feed speed are constant and the target processing surface S is relatively flat, the feed amount during the rotation of the rotary cutting tool by the rotation angle of one blade (360 ° / number of blades) is substantially the same. Also,
The “line segment length L” is a plurality of tool points (NC) indicated by ▲ or △ at positions offset from the target machining surface S by the tool radius.
Data) The distance between the tool points CL _i , CL _{i + 1} ,... Allows the rotary cutting tool to move linearly between those tool points. (A) corresponds to the present invention when f ≒ L, and
(B) and (c) are shown for comparison with f <L and f> L, respectively. In the case of (b) where f <L, a relatively large tolerance T is generated and the tolerance is increased. While a large shape error occurs in which the cusp C is superimposed on T, in the case of (c) where f> L, as in (a) of the present invention, the tolerance T is substantially the minimum, but a wasteful tool not involved in cutting. Point △ exists. That is, if the feed f of one blade is the same, the tolerance T becomes substantially minimum at L ≒ f, and L
Even if <f, there is almost no difference in the tolerance T and the cusp C does not change, so that only useless tool points increase. What is necessary is that the tool point is set for each feed f of approximately one blade, in other words, the tool point is set for each cutting point of the cutting edge, so that the line segment length L and the feed f of one blade are set. Does not need to completely match, and when the target processing surface S is concave, the line segment length L is shorter, and when the target processing surface S is convex, the feed f of one blade is shorter. Varies depending on the shape of the target processing surface S.

On the other hand, according to the present invention, in the vicinity of the tool point, the tip of the cutting edge of the rotary cutting tool is set at the target position around the tool axis.
Since it is located at the cutting point on the processing surface , there is little variation in the shape error, and the cutting can always be performed with high dimensional accuracy. For example, FIG. 2A shows the case of the present invention in which cutting is performed near the tool points CL _i , CL _{i + 1} ,..., And FIG. However, in (b), since the cutting position itself by the rotary cutting tool has an error by the tolerance T, the maximum error dimension E is larger than in (a) where the error at the cutting position is substantially zero. That is, even if the tool point is set for each feed f of approximately one blade, the error size differs depending on the cutting position where cutting is actually performed by the cutting edge, and the error size is minimized when cutting is performed at the tool point. . Each tool point C
In the present invention in which cutting is performed in the vicinity of L _i , CL _{i + 1} ,..., The distance from the target processing surface S to the tool center during cutting is always constant, that is, the tool radius, and the error at that position is substantially zero. For this reason, the concept of tolerance has no meaning.

The cutting shape shown in FIGS. 1 and 2, that is, the surface having a waveform in which the arc of the tool radius repeats, is obtained when the rotary cutting tool is driven to rotate around the axis and cut. Although the cutting shape is slightly different from the cutting shape when the tool is driven to rotate around the axis while moving between the tool points, the rotation angle at which one cutting edge of the rotary cutting tool is involved in cutting is generally about 5 to 10 °. Therefore, it can be assumed that cutting is performed in a stopped state. Also, in the figure, the feed f of one blade is larger than that of the rotary cutting tool in order to clearly show the cusp C, but generally, the feed f of one blade is 1/30 to 1/100 of the tool diameter of the rotary cutting tool. The cusp C is about several μm.

[0010]

As described above, according to the cutting method of the present invention, there is little variation in shape error, cutting is always performed with high dimensional accuracy, and the number of tool points is minimized. Becomes

[0011]

According to a second aspect of the present invention, there is provided a rotary cutting tool which is intermittently cut by a cutting edge by being rotationally driven around an axis at a constant rotation speed. in by sequentially moved to a plurality of tool point in cutting process for forming a target machining surface I line a predetermined cutting to the work object, the rotation by the rotation angle of approximately 1 blade component among the plurality of tool point As the cutting tool is rotated, the plurality of tool points are set in accordance with the rotation speed and the feed speed, and the tip of the cutting edge of the rotary cutting tool is arranged around the tool axis in the vicinity of the plurality of tool points . On the target processing surface
Characterized in that it is located at a cutting point .

[0012]

The present invention corresponds to an embodiment of the first invention, wherein a rotary cutting tool is rotated by a rotation angle of approximately one blade between a plurality of tool points, and the plurality of tool points are rotated. In the vicinity, the tip of the cutting edge of the rotary cutting tool turns around the tool axis.
This is the same as the first invention in that it is located at the cutting point on the target machined surface, and the same operation and effect as the first invention can be obtained. On the other hand, in the present invention, the rotary cutting tool is driven to rotate around the axis at a constant rotation speed, and is moved at a constant feed speed. Is set according to the rotation speed and the feed speed so that the rotary cutting tool is rotated by the rotation angle of one blade. That is, since the direction of the cutting edge at each tool point is constant, the direction of the cutting edge with respect to the target processing surface to be cut differs depending on the shape, and it is necessary to accurately control so that cutting is performed at the tool point. However, for example, (a) the plurality of tools are determined based on a predetermined reference rotation speed and reference feed speed so that the rotary cutting tool is rotated by a rotation angle of approximately one blade between the plurality of tool points. A tool point setting step of setting a point; and (b) a tip of a cutting edge of the rotary cutting tool near the plurality of tool points.
The cutting point on the target machining surface whose end is around the tool axis
A phase setting step of setting the rotation phase of the rotary cutting tool for each of the tool points so that the rotary cutting tool is located at a plurality of tool points. As compared with a cutting method having a cutting control step of controlling the rotation speed and feed rate of the rotary cutting tool in association with each other so that the rotary cutting tool has the rotation phase set in the phase setting step, each tool point It is not necessary to set the rotation phase in, and since the rotation speed and the feed speed may be constant, there is less follow-up delay compared with the case where the feed speed is sequentially changed.
High-efficiency machining by high-speed feed is possible.

[0013]

As described above, according to the cutting method of the second invention, the same effects as those of the first invention can be obtained, and it is not necessary to set the rotational phase at each tool point. In addition, since the rotation speed and the feed speed may be constant, high-efficiency machining can be performed.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 3 is a block diagram of a cutting apparatus for performing cutting in accordance with the method of the present invention, and is a CAM (Co) for creating NC data including a plurality of tool points that define a tool movement trajectory.
mputer Aided Manufacturing) System 10, its NC
An NC data memory 12 which is a storage medium such as a magnetic tape or a magnetic disk for storing data, and an NC control device 14 which controls the operation of the NC machine tool 16 according to the NC data are provided. For example, as shown in FIG. 4, the NC machine tool 16 rotates a ball end mill 18 as a rotary cutting tool around an axis while rotating the ball end mill 18 in the X-axis, Y-axis, and Z-axis directions perpendicular to the workpiece 20. Relative to the workpiece 20, the workpiece 20 is subjected to predetermined cutting such as a free-form surface. The main shaft rotation driving means 22 for rotationally driving the ball end mill 18, and the ball end mill 18 are connected to the X-axis and the X-axis.
There is provided a feed drive unit 24 that translates three-dimensionally in the Y-axis and Z-axis directions. The main shaft rotation driving means 22 is an electric motor such as a servomotor, for example.
Is configured to include, for example, three sets of feed screws that move in three axial directions and a servomotor that rotationally drives the feed screws. FIG. 4A shows an example of a horizontal NC machine tool 16 in which the Z axis parallel to the main axis is horizontal, and FIG. 4B shows a vertical NC machine tool in which the Z axis parallel to the main axis is vertical. 16 is an example.

The CAM system 10 includes a CPU, RA
The NC data is created by using a microcomputer having M, ROM, and the like. A step S1 is a cutting path setting step, and a planned cutting path 28 is formed on the free-form surface 26 as shown in FIG. Set. The free-form surface 26 is three-dimensionally changed at the target processing surface to be cut.
It is displayed on a display device according to CAD data or the like. The planned cutting path 28 may be configured such that an optimal path is automatically set according to cutting conditions or the like, or may be arbitrarily set by an operator using an input device such as a mouse. . Step S2 is a cutting point setting step. As shown in FIG. 5B, the feed amount F during the rotation of the ball end mill 18 by one blade on the planned cutting path 28, for example, 1
In the case of a single blade, the cutting points CP are provided at intervals of the feed amount F during one rotation (360 °) around the axis. The feed amount F is calculated from the number of blades of the rotary cutting tool to be used, that is, the ball end mill 18 based on a reference rotation speed and a reference feed speed that are predetermined according to the specifications of the ball end mill 18 and the material of the workpiece 20. The cutting point CP is set in three-axis orthogonal coordinates (x, y, z) by being obtained and automatically calculating the feed amount F by an operator or by automatically calculating the feed amount F.

Step S3 is a tool point setting step, in which the ball end mill 18 is driven to rotate around the axis as shown in FIG. Set CL. Specifically, a position separated from each cutting point CP by a radius of the ball end mill 18 in the normal direction of the free-form surface 26 is obtained by using the function of the CAM system 10, and the position is determined by the tool point C.
L is set in three-axis rectangular coordinates (x, y, z). Such a tool point CL is obtained based on a predetermined reference rotation speed and reference feed speed such that the rotary cutting tool is rotated by a rotation angle of approximately one blade between the tool points CL. is there. The next step S4 is a phase setting step. As shown in FIG. 6, the rotation of the ball end mill 18 at each tool point CL is performed so that the cutting edge 30 of the ball end mill 18 cuts the workpiece 20 near the tool point CL. Set the phase θ. Specifically, the tool center of the ball end mill 18 (the center of curvature of the hemispherical shape which is the rotation locus of the cutting edge 30)
Is located at the tool point CL, the rotation phase θ at which the tip of the cutting edge 30 is located at the cutting point CP around the tool axis (parallel to the Z axis) is determined by using the function of the CAM system 10, for example, X. = 0 or Y = 0, which is a deviation angle from the reference phase. The rotation phase θ is set at ± according to the advance / delay in the tool rotation direction,
When a plurality of cutting edges are provided at equal angular intervals such as three blades, π, 2π / 3, etc. may be added and set.

Step S5 is a storage step in which the tool point CL and the rotational phase θ set as described above are stored in the NC data memory 12 as NC data. The NC control device 14 includes a microcomputer having a CPU, a RAM, a ROM, and the like.
NC according to NC data stored in data memory 12
The operation of the machine tool 16 is controlled, but the NC data may be directly stored in a storage medium of the NC control device 14 online. A means for automatically executing each of the steps S1 to S5 is provided so that the CAM system 10 automatically obtains the tool point CL and the rotation phase θ by inputting necessary information by an operator. It is desirable.

The NC control device 14 includes the ball end mill 1
8 is sequentially moved linearly to the plurality of tool points CL, and a cutting control step of controlling the feed speed of the ball end mill 18 so that the ball end mill 18 has the rotation phase θ at the tool point CL. Of
Functionally provided are a position comparison means 32, a phase comparison means 34, and a feed speed control means 36. The tool point CL of the NC data is read into the position comparison means 32, and the rotational phase θ is transmitted to the phase comparison means 34. Is read. A signal representing the relative position of the spindle position of the NC machine tool 16, that is, the relative position of the ball end mill 18 with respect to the workpiece 20 is detected from the tool position detecting means 38 which detects the relative position of the NC machine tool 16 in three-axis orthogonal coordinates. The position deviation is obtained by comparing the tool point CL with the relative position of the ball end mill 18, and a signal representing the position deviation is output to the feed speed control means 36. The tool position detecting means 38 is, for example, a rotary encoder provided in three servo motors constituting the feed driving means 24. A signal representing the rotational phase of the spindle is supplied to the phase comparing means 34 from the spindle rotational phase detecting means 40 which detects the rotational phase of the spindle of the NC machine tool 16. Is compared with the rotational phase of the main shaft to obtain a phase deviation, and outputs a signal representing the phase deviation to the feed speed control means 36. The main spindle rotation phase detecting means 38 is, for example, a rotary encoder provided in a servo motor constituting the main spindle rotation driving means 22, and similarly to the case of the rotation phase θ, for example, X = 0, Y = 0, etc. The mounting phase around the axis of the ball end mill 18 is determined based on the deviation angle of the specific position of the main shaft with respect to the phase, and based on the specific position of the main shaft.

The feed speed control means 36 controls the position deviation and the phase deviation so that these deviations are eliminated.
The feed driving means 24 of the NC machine tool 16 is controlled so that when the ball end mill 18 reaches the tool point CL, the rotation phase θ is reached and the cutting edge 30 cuts the cutting point CP. In that case, between the tool points CL, the ball end mill 1
8 is not involved in cutting, and it is sufficient that the tool position at the tool point CL is guaranteed. Therefore, as long as the ball end mill 18 does not interfere with the work 20 between the tool points CL, a straight line must be formed between the tool points CL. It is not necessary to perform position control by interpolation, and the tool position may be controlled based only on the tool point CL. Note that the spindle rotation drive means 22 of the NC machine tool 16 is configured to rotationally drive the spindle at a preset reference rotation speed.

In the cutting apparatus of this embodiment as described above, the ball end mill 18 is rotated by a rotation angle of approximately one blade between the tool points CL as shown in FIG. As is apparent, the tolerance is substantially minimized and the number of tool points CL is minimized. Since the number of tool points CL is minimized, the NC controller 1
The processing time of No. 4 has a margin, and the feed speed and the tool rotation speed can be increased to perform high-efficiency machining. Tool point CL
In the case where the tool position is controlled based on only the tool point CL without performing linear interpolation between them, the speed can be further increased. In addition, the feed amount F during rotation by one blade based on the reference rotation speed and the reference feed speed, that is, the distance between the cutting points CP corresponds to the feed f of one blade in FIG. The line segment length L, which is the distance between the tool points CL while the feed f is constant, varies according to the shape of the free-form surface 26.

Also, when the ball end mill 18 has the tool point CL
When the cutting edge 30 is reached, the cutting edge 30 cuts the workpiece 20, so that the shape error does not vary as is apparent from FIG. 2, and the cutting process is always performed with high dimensional accuracy. Can be. In particular, in this embodiment, the rotation phase θ is set as NC data, and the feed speed is controlled so that the actual rotation phase around the axis of the ball end mill 18 at each tool point CL matches the rotation phase θ. The cutting edge 30 is positioned at the cutting point CP at the tool point CL, and is controlled with high precision so as to cut the workpiece 20, so that the variation in shape error is further reduced and the dimensional accuracy is increased.

Next, another embodiment of the present invention will be described. In the following embodiments, portions substantially common to the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

In the embodiment shown in FIG. 7, when the NC data does not include the rotation phase θ, the CAM system 10 for creating the NC data is used. As shown in (1), an offset surface 44 is created at a position separated by a radius of the ball end mill 18 (a radius of curvature of a hemispherical shape which is a rotation locus of the cutting edge 30) in a direction normal to the free curved surface 26. When the offset surface 44 is created, for example, if the free-form surface 26 is a relatively flat surface close to an XY plane perpendicular to the axis of the tool (parallel to the Z-axis), the free-form surface 26 is simply set to the Z-axis. It is only necessary to offset in the direction by the radius dimension of the tool. In the tool path setting process of the next step SS2, FIG.
As shown in the figure, the tool center path 46, which is the moving path of the ball end mill 18, is set on the offset surface 44 in the same manner as in the case of the planned cutting path 28, and step SS
In the tool point setting step 3, as shown in FIG. 8 (c), the tool point CL is set to the three-axis orthogonal coordinates at the interval of the feed amount F while the ball end mill 18 rotates by one blade on the tool center path 46. (X, y, z). Such a tool point CL
Is determined based on a predetermined reference rotation speed and reference feed speed such that the rotary cutting tool is rotated by a rotation angle of approximately one blade between the tool points CL. Step SS4 is a storage step in which the tool point CL set as described above is stored in the NC data memory 12 as NC data. Note that each of the above steps SS1 to SS
It is desirable to provide a means for automatically executing each of the steps 4 and 4 so that the CAM system 10 can automatically determine the tool point CL by inputting necessary information by an operator.

The NC control device 14 includes the ball end mill 1
8 is sequentially moved linearly to the plurality of tool points CL, and a cutting control for controlling the feed speed of the ball end mill 18 so that the rotation phase of the ball end mill 18 becomes a predetermined reference phase at the tool point CL. A reference phase memory 48 is provided in addition to the position comparing means 32, the phase comparing means 34, and the feed speed controlling means 36. The reference phase memory 48 stores each tool point C
A phase around the axis when the ball end mill 18 reaches L is stored as a reference phase. For example, the cutting edge of the cutting edge 30 is positioned near the free-form surface 26 at each tool point CL as shown in FIG. Is set to a predetermined phase in advance. The free-form surface 26 is perpendicular to the axis of the tool (parallel to the Z axis).
In the case of a relatively flat surface close to the Y plane, as shown in FIG. 9, the rotation phase at each tool point CL is a constant reference phase,
In the figure, even if it is downward, the rotational phase difference from the actual cutting point CP is relatively small. The phase comparing means 34 compares the reference phase with the actual rotational phase of the main spindle supplied from the main spindle rotational phase detecting means 40 to determine a phase deviation, and sends a signal representing the phase deviation to the feed speed control means 36. Output to If the ball end mill 18 has one blade, the phase deviation can be obtained at all the tool points CL.
When there are a plurality of cutting edges 30 such as a single blade, the phase difference may be obtained at the tool point CL for each rotation of the tool.
Note that when a plurality of cutting edges 30 are provided, a plurality of reference phases may be set, and the phase difference may be obtained at all the tool points CL while periodically changing the reference phase.

The feed speed control means 36 is provided by the position comparing means 3
2 and the phase deviation supplied from the phase comparing means 34 based on the position deviation supplied from the ball end mill 18.
Are sequentially moved to each tool point CL, and the feed driving means 24 is controlled such that the rotation phase of the ball end mill 18 becomes the reference phase at the tool point CL. Thereby, when the ball end mill 18 reaches the tool point CL, the phase around the axis becomes the reference phase, and the cutting edge 30 cuts the workpiece 20 before and after that. In this embodiment, basically, the ball end mill 18 is sequentially moved to each of the tool points CL at a preset constant reference feed speed, and the main spindle rotation driving means 22 of the NC machine tool 16 is set in advance. The ball end mill 18 is driven to rotate at the given reference rotation speed. That is, the ball end mill 1
If 8 is moved at a constant reference feed speed and driven to rotate at a constant reference rotation speed, the phase deviation is theoretically zero, and the rotation phase of the ball end mill 18 at the tool point CL becomes the reference phase. It is.

Also in this embodiment, since the ball end mill 18 is rotated by a rotation angle of one blade between the tool points CL as shown in FIG. 9, the tolerance is substantially minimized as apparent from FIG. At the same time, the number of tool points CL is minimized, and high-efficiency machining can be performed by increasing the feed speed and the tool rotation speed as in the first embodiment. In particular, in the present embodiment, basically, the ball end mill 18 is driven to rotate around the axis at a constant reference rotation speed and is moved at a constant reference feed speed. Therefore, it is not necessary to set the rotation phase at each tool point CL, and the rotation speed and the feed speed may be constant. Therefore, there is less follow-up delay compared with the case where the feed speed is sequentially changed. Efficient machining is possible. In the present embodiment, the line segment length L in FIG. 1 is constant at the feed amount F during the rotation of one blade based on the reference rotation speed and the reference feed speed, and the length of one blade which is the distance between the cutting points CP. The feed f varies depending on the shape of the free-form surface 26.

The ball end mill 18 has a tool point CL.
Since the cutting edge 30 cuts the workpiece 20 before and after it is located at a position, there is little variation in shape error as is apparent from FIG. 2, and cutting is always performed with high dimensional accuracy. be able to. In this embodiment, since the rotation phase of the ball end mill 18 at the tool point CL is constant and the cutting of the workpiece 20 may be slightly shifted from the tool point CL, the cutting of the workpiece 20 at the tool point CL is performed. As compared with the first embodiment, there is a possibility that the shape error may slightly vary or the dimensional accuracy may slightly deteriorate, but the rotation angle at which one cutting edge 30 is involved in the cutting is generally 5 to 1
Since it is about 0 °, there is almost no problem if the free-form surface 26 to be cut is a relatively flat surface close to the XY plane perpendicular to the axis of the tool (parallel to the Z axis). In FIG. 9, the cutting point CP is shown on an arc centered on each tool point CL, but at the tool point CL on the left side, the cutting edge 30 is already at the cutting point C.
P, the cutting point CP is slightly strictly to the left of the drawing, and the cutting edge 30 does not reach the cutting point CP at the right tool point CL. Becomes

FIG. 10 shows the pick feed amount p in a direction perpendicular to the feed direction (right direction in the figure) of the ball end mill 18.
And the distance between the plurality of tool points CL in the feed direction, that is, the feed f of one blade, which is the distance between the cutting points CP, is set to be approximately 1.5: √3, and adjacent to each other. This is a case where the tool point CL on the tool moving path 50 to be moved is shifted by a substantially half pitch in the tool feed direction. G in the figure
Is the shift amount in the tool feed direction, where g ≒ f / 2. The figure is a plan view of the cut surface. In this case, since the ridge line of the cusp C becomes a regular hexagon in plan view as shown in the figure, if the maximum error size of the cusp C is the same, (the pick feed amount p The processing efficiency represented by x1 blade feed f) is maximized, and cutting can be performed most efficiently. That is, the error dimension of the cusp C becomes maximum at each vertex of the regular hexagon farthest from the tool center in plan view, and when the dimension from the tool center to the vertex is a, the pick feed amount p = 1.5a, 1 Blade feed f = (√
3) × a, p × f = 1.5 × (√3) × a ²
On the other hand, for example, as shown in FIG.
= 1 blade feed f and displacement g = 0, the cusp C
Is a square, and if the dimension from the tool center in plan view to the vertex of the square where the error dimension of the cusp C is the maximum is also a, the maximum error dimension of the cusp C is the same as in FIG. Is p = f = (√2) × a and p
× f = 2 × a ² , and the processing efficiency is 77 in the case of FIG.
%. In the case of FIG. 10, if the pick feed amount p and the feed f of one blade are set so that the machining efficiency becomes substantially the same as that of FIG. improves. Further, such a tool point setting method can be applied to any of the above-described two embodiments.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the present invention can be embodied in other forms.

For example, in the above-described embodiment, the ball end mill 18 is used as a rotary cutting tool. However, not only other end mills but also, for example, a two-dimensional curved surface in which a target processing surface to be cut changes in a waveform in one direction. For example, the present invention can be similarly applied to cutting of a milling cutter having an outer peripheral blade having a cylindrical rotation trajectory. In addition, the present invention is applicable even when the target processing surface to be cut is a flat surface,
There is no tolerance problem, but the number of tool points is minimized.

In the above-described embodiment, the case where the ball end mill 18 is moved in parallel with the three-axis orthogonal coordinates has been described. For example, the attitude is changed so that the axis of the ball end mill 18 is always perpendicular to the target machining surface. For example, it is also possible to employ another moving type machine tool.

In the above-described embodiment, the rotation phase at the tool point CL is compared with the rotation phase θ of the NC data or with a predetermined reference phase. The position to be compared can be set arbitrarily, such as slightly before the tool point CL, and the rotational phase θ and the reference phase may be set according to the position to be compared.

In the above embodiment, the ball end mill 1
8, the feed speed is controlled so that the rotation phase coincides with the rotation phase θ or a fixed reference phase. However, the rotation speed of the ball end mill 18 may be changed. The rotation speed and the feed speed may be controlled in association with each other so that the cutting edge 30 cuts the workpiece 20 in the vicinity.

In the embodiment of FIG. 3, the rotational phase θ is set as NC data. However, as in the embodiment of FIG. 7, the rotational phase of the ball end mill 18 is constant at each tool point CL. While the reference phase may be set, the cutting edge 3 for each tool point CL in the embodiment of FIG.
The rotation phase θ at which the 0 cutting edge is located on the workpiece 20 side, that is, the cutting point CP in FIG. 9 is set as NC data,
Control may be performed such that the rotation phase θ is obtained at each tool point CL.

Further, when the rotary cutting tool is driven to rotate relative to the workpiece at a constant feed speed while being driven to rotate at a constant rotational speed, the tip of the cutting edge of the rotary cutting tool is moved to the tool axis.
If the tool center when located at the cutting point on the target machining surface around the center is set as the tool point, the rotary cutting tool is driven to rotate at a constant rotation speed as in the embodiment of FIG. With relative movement,
As in the embodiment of FIG. 3, the cutting edge cuts the workpiece at each tool point. In this case, the movement time between the tool points varies according to the shape of the target processing surface.

Although the embodiment shown in FIG. 10 is for one-way machining in which the feed direction of the tool is constant, the same effect can be obtained by reciprocating machining in which cutting is performed while alternately feeding in the opposite direction.

Although not specifically exemplified, the present invention can be embodied with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining the operation and effect of the present invention;
In the case of the present invention, (b) and (c) are comparative examples.

FIG. 2 is another schematic diagram illustrating the operation and effect of the present invention;
(A) is the case of the present invention, and (b) is a comparative example.

FIG. 3 is a block diagram illustrating an example of a cutting apparatus that can suitably implement the method of the present invention.

FIG. 4 is a diagram illustrating a specific example of the NC machine tool in FIG. 3;

FIG. 5 is a diagram illustrating a procedure for setting a tool point using the CAM system of FIG. 3;

FIG. 6 is a diagram illustrating a method of setting a rotation phase θ using the CAM system of FIG. 3;

FIG. 7 is a block diagram illustrating another example of a cutting apparatus that can suitably implement the method of the present invention.

FIG. 8 is a diagram illustrating a procedure for setting a tool point using the CAM system of FIG. 7;

FIG. 9 is a diagram illustrating a relationship between a tool point and a cutting edge position during actual cutting of the cutting apparatus of FIG. 7;

FIG. 10 is a view for explaining another example of a method of setting a tool point using the method of the present invention, and is a view corresponding to a plan view of a cutting surface.

FIG. 11 is a diagram showing a comparative example for explaining the effect in the case of FIG. 10;

[Explanation of symbols]

18: ball end mill (rotating cutting tool) 20: Workpiece material 26: free-form surface (the target etching surface) 30: cutting edge _{CL, CL i, CL i +} 1, ···: Tool point CP: cutting point

Claims (2)

(57) [Claims] 1. A predetermined cutting process is performed on a workpiece by relatively rotating a rotary cutting tool, which is intermittently cut by a cutting edge by being rotationally driven around an axis, to a plurality of tool points. in cutting method of forming a target machining surface I line, together with said rotary cutting tool by the rotation angle of approximately 1 blade component is rotated among the plurality of tool point of the rotary cutting tool in the vicinity of the tool point The tip of the cutting edge is around the tool axis
A cutting method using a rotary cutting tool, the cutting method being positioned at a cutting point on the target processing surface . 2. A rotary cutting tool, which is intermittently cut by a cutting edge by being rotationally driven around an axis at a constant rotation speed, is sequentially moved to a plurality of tool points at a relatively constant feed speed. target machining surface I line a predetermined cutting the object
In the cutting method, the plurality of tool points are set according to the rotation speed and the feed speed so that the rotary cutting tool is rotated by a rotation angle of approximately one blade between the plurality of tool points. In the vicinity of the plurality of tool points, the tip of the cutting edge of the rotary cutting tool is
A cutting method using a rotary cutting tool , wherein the cutting point is located at a cutting point on the target processing surface around a center .