JP3224184B2 - Machining method with 5-axis NC machine tool - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is applied to, for example, a 5-axis NC machining center which is a 5-axis numerically controlled machine tool (hereinafter also referred to as an NC machine tool) for machining a press die or the like. The present invention relates to a machining method using a suitable 5-axis NC machine tool.

[0002]

2. Description of the Related Art Conventionally, a work surface of a work such as a press die has conventionally been a three-axis XYZ orthogonal numerically controlled machine tool, for example, a three-axis machine.
It is machined by a tool such as a ball end mill mounted on the spindle head of the spindle NC machining center.

In the case of the three-axis NC machine tool, as shown in FIG. 18, the axial direction of the ball end mill 1 is always a fixed direction, for example, a vertical direction. A direction indicated by an arrow P (hereinafter also referred to as an arc direction) indicates a step feed direction of the ball end mill 1 with respect to the work 2.

Ball end mill 1 for 3-axis NC machine tool
Moves in the direction of arrow Q (hereinafter, also referred to as a generatrix direction) to cut the workpiece 2 and then is step-feeded in the direction of arrow P. Then, from the position where the step was sent,
The procedure of cutting and moving the work 2 again in the direction of the arrow Q is repeated to cut substantially the entire surface of the work 2.

On the other hand, a technique for processing a workpiece with a 5-axis NC machine tool has been proposed in Japanese Patent Application Laid-Open No. 1-205595. In this technique, as shown in FIG. 19, a technique for processing a work 2 by controlling a ball end mill 1 mounted on a 5-axis NC machine tool (not shown) so as to be always perpendicular to a processing surface of the work 2. It is. The publication describes that by performing arithmetic processing so that the axial direction of the ball end mill 1 is always perpendicular to the processing surface of the work 2, complicated five-axis NC data can be easily created.

[0006] In the case where the workpiece 2 is machined by step-feeding the ball end mill 1, FIG. 20 (for a 3-axis NC machine tool) and FIG. 21 (for a 5-axis NC machine tool)
As shown in (2), a machining residue (hereinafter, also referred to as a machining residue, a machining balance, or a so-called cusp) Δh as viewed from the cross-sectional direction of the work 2 is generated. In FIG. 20 and FIG. 21, reference numeral 2c is a cutting allowance.

In order to reduce the machining balance Δh, a step feed pitch Pn (P ₁ , P ₁ ,
P ₂ , P ₁ and P ₃ in FIG. 21 may be reduced.

[0008]

However, when the pitch Pn is reduced, there is a problem that the processing time becomes longer, and as a result, the processing cost increases.

In particular, for example, a surface (hereinafter also referred to as a curved surface) 2a of the work 2 that is curved outward with a radius R is a three-axis N.
C When machining with the ball end mill 1 mounted on the machine tool, the step feed pitch Pn of the ball end mill 1 is used in order to make the machining balance Δh approximately the same as the horizontal portion 2b.
Must be set to a pitch P ₂ (see FIG. 20) which is shorter than the feed pitch P ₁ for processing the horizontal portion 2b, so that there is a problem that the processing time is further increased.

On the other hand, it is mounted on the 5-axis NC machine tool described above.
In the case of the bent ball end mill 1, the curved surface 2a is machined.
The pitch Pn, rather, the pitch for processing the horizontal portion 2b.
Chi-P ₁Long pitch P compared to_Three(See Fig. 21)
Such problems do not occur (in fact,
The pitch Pn is defined by the tip position of the ball end mill 1.
So P₁≒ P_Threebecome. ).

However, in the machining by the ball end mill 1 mounted on the 5-axis NC machine tool, the work 2
The ball end mill 1 is always held perpendicularly to the processing surface of. Therefore, the processing of the work 2 is performed only at one point at the tip of the ball end mill 1 which rotates at high speed around the axis. At one point at the tip, there is a problem that the peripheral speed of the blade is basically a zero value and the processing speed and the processing surface accuracy cannot be increased. In addition, since the cutting is performed at one point at the tip of the ball end mill 1, wear of the ball end mill 1 is accelerated, and a problem that the ball end mill 1 needs to be frequently replaced occurs.

For example, when a press die as a work is used for forming an outer panel of a private automobile, it is important that the press surface of the press die is smooth. After machining by NC machine tool,
The so-called cusp Δh was manually ground. This manual operation requires skill and takes a considerable amount of time, resulting in a problem that processing costs increase.

The present invention has been made in view of such problems, and enables a surface curved outwardly of a work such as a press die to be precisely machined in a short time. It is another object of the present invention to provide a machining method using a 5-axis NC machine tool, which can easily determine a moving path of a tool.

The outwardly curved surfaces of the workpiece are, as shown in FIG. 1, substantially opposite arc-shaped lines (simply called arcs) 111 and 11 having radii of Ra ₁ and Ra ₂ , respectively.
2 and the substantially opposite ends 111a, 112a and 111b, 112b of these two arc-shaped lines 111, 112.
, Two bus-like lines (straight lines or curves) 11
3, a curved surface (also referred to as a curved surface) 115 defined by 114. In FIG. 1, the curved surface 115 is
It can be considered as a set of lines exhibiting a so-called R (R) shape, that is, arcs having a constant or changing radius and arranged continuously in the generatrix direction Q. Also, in FIG. 1, each of the generatrix lines 113 and 114 of the curved surface 115
Are assumed to be flat surfaces. Even if there are irregularities on the planes 116 and 117, each arc 11
It is assumed that there are only convex portions lower than the surfaces formed by the tangents of the arcs 111 and 112 drawn from the terminal ends 111a and 112a of the bases 1 and 112 and the terminal ends 111b and 112b.

[0015]

SUMMARY OF THE INVENTION The present invention provides a method for cutting or grinding an outwardly curved surface of a work by a rotary working tool having an inwardly curved arc-shaped cutting edge. The tool is moved in the genera direction to process the partially curved surface, and then the tool is step-fed in an arc direction substantially orthogonal to the genera direction, and the tool is moved in the genera direction again at the step-feed position. And machining a partial curved surface adjacent to the partial curved surface and repeating these steps to machine the entire outer curved surface of the work. A step of selecting a tool in which the radius of the inwardly curved arc is equal to or larger than the radius of the outwardly curved arc of the work, and the length of the outwardly curved arc of the work and the length of the inwardly curved arc of the tool; Said Based on the circular arc direction of the permissible working balance ri over click, and determining the step feed count, characterized in that comprising a machining step of machining the workpiece at step feed count of the determined.

In the present invention, when the determined number of step feeds is one, first, one end of the outwardly curved arc of the workpiece and the inwardly curved arc of the tool are first formed. The tool is moved in the generatrix direction in a positional relationship where the outer end of the tool is in contact with the outer end of the tool to process a partially curved surface, and then the other end of the inwardly curved arc of the workpiece and the inner side of the tool. Step-feeding to a positional relationship where the curved arc contacts the tool tip side end portion, and moving the tool in the generatrix direction with the positional relationship to machine the remaining partially curved surface, thereby machining the entire outer curved surface. Then, when the determined number of step feeds is two, first, the tool is placed in a positional relationship where one end of the outwardly curved arc of the workpiece is in contact with the tool outer end of the inwardly curved arc of the tool. Is the bus direction Move to process the partially curved surface, and then step-feed to the positional relationship where the central portion of the outwardly curved arc of the workpiece and the central portion of the inwardly curved arc of the tool are in contact with each other. The tool is moved in the direction of the generatrix to machine a partial curved surface at the center, and further, the other end of the outwardly curved arc of the workpiece and the tool tip end of the inwardly curved arc of the tool. Step feed to the positional relationship where it touches, move the tool in the direction of the generatrix in that positional relationship and process the remaining partial curved surface to process the entire outer curved surface, and the determined number of step feeds
When three or more times, first, the tool is moved in the generatrix direction in a positional relationship where one end of the outwardly curved arc of the workpiece and the tool outer end of the inwardly curved arc of the tool are in contact with each other. Before processing the partially curved surface, and then dividing the outwardly curved arc of the work by the number of step feeds.
The equidistant point on the outwardly curved arc and the inwardly curved arc of the tool are
Step-feeding sequentially to a positional relationship where the equidistant points on the inwardly curved arc divided by the number of step-feeds sequentially contact each other,
The tool is moved in the generatrix direction in each positional relationship of the step feed to sequentially machine the partially curved surface, and further, the other end of the outwardly curved arc of the workpiece and the tool of the inwardly curved arc of the tool Stepping is performed to a positional relationship where the distal end portion is in contact with the outer peripheral curved surface by machining the last partial curved surface by moving the tool in the generatrix direction with the positional relationship. And

Further, according to the present invention, in the machining step, when the determined number of times of step feed is one, first, one end of the outwardly curved arc of the workpiece and the inwardly curved arc of the tool are formed. The tool is moved in the generatrix direction in a positional relationship where the tool tip side end is in contact with the tool, and a partially curved surface is machined, and then the other end of the inwardly curved arc of the work and the inside of the tool Step-feeding to a positional relationship where the tool outer end portion of the curved arc contacts the tool outer end portion, and moving the tool in the generatrix direction with the positional relationship to machine the remaining partially curved surface, thereby machining the entire outer curved surface. Then, when the determined number of times of step feed is two, first, the one end portion of the outwardly curved arc of the workpiece and the tool tip side end portion of the inwardly curved arc of the tool are in contact with each other in a positional relationship where they are in contact with each other. The tool Go to direction by processing the partially curved surface,
Next, step-feeding is performed until the center of the outwardly curved arc of the workpiece and the center of the inwardly curved arc of the tool are in contact with each other, and the tool is moved in the generatrix direction in the positional relationship. To process the central partial curved surface,
Step-feeding to the positional relationship where the other end of the outwardly curved arc of the workpiece and the outer end of the tool of the inwardly curved arc of the tool are in contact with each other, and moving the tool in the generatrix direction with the positional relationship. By processing the remaining partial curved surface, the entire outer curved surface is processed, and the determined number of step feeds
When three or more times, first, the tool is moved in the direction of the generatrix in a positional relationship where one end of the outwardly curved arc of the workpiece is in contact with the tool distal end of the inwardly curved arc of the tool. Then, the partially curved surface was processed, and then the outwardly curved arc of the workpiece was divided by the number of step feeds.
Equal points on the outwardly curved arc and the inwardly curved arc of the tool
Is divided by the number of times of the step feed to sequentially step forward until the equidistant points on the inwardly curved arc are sequentially in contact with each other, and the tool is moved in the generatrix direction in each of the step-forwarded positional relationships. To sequentially machine the partially curved surface, and further, step-feeds to a positional relationship where the other end of the outwardly curved arc of the workpiece and the outer end of the tool of the inwardly curved arc of the tool are in contact with each other. Then, the tool is moved in the generatrix direction to machine the last partial curved surface, thereby machining the entire outer curved surface.

Further, according to the present invention, the moving path of the tool in each of the generatrix directions divides the length of each of the workpieces in the generatrix direction by a predetermined length. A tip position of the tool is determined from the positional relationship with the workpiece, and the determined tip position of the tool at each of the division points is a path that is continuously connected.

[0019]

According to the present invention, the outer curved surface of the workpiece is cut or ground (from roughing to polishing) by a rotary working tool having an arc-shaped inner curved surface having a radius larger than the radius of the arc of the outer curved surface. ), The number of times the workpiece is moved in the generatrix direction (outside of the workpiece) based on the allowable work balance in the arc direction of the workpiece, the length of the outwardly curved arc of the workpiece, and the length of the inwardly curved arc of the tool. (The number of step feeds in the direction of the curved arc + 1) is determined, and the workpiece is machined according to the number of times of movement in the generatrix direction.

Further, according to the present invention, when the determined number of step feeds is three or more , the state in which the one arc end of the tool (the front-side arc end or the outer arc end) is matched with the one arc end of the work. Move the tool in the generatrix direction to process the partially curved surface, and then step through the workpiece arc .
Step the equidistant point on the arc divided by the number of feeds and the tool arc .
Step feed in the arc direction so as to sequentially match the equidistant points on the arc divided by the number of feeds , move the tool in the direction of the generatrix for each step feed, and sequentially process the adjacent partial curved surface, Lastly, the other arc end of the workpiece (for example, when the one arc end is selected as the arc end on the tip side, the outer arc end) and the other arc end of the tool are aligned in the generatrix direction. The tool is moved to process the entire curved surface of the work. Step feed count is 1
The above number is assumed.

Further, according to the present invention, when there are irregularities in the generatrix direction of the outwardly curved surface of the workpiece (irregularities such that the inclination of the tangent changes continuously), that is, the generatrix lines are not straight but smooth. When it is a curved line, or when the adjacent genera direction is not parallel even if it is a straight line, in other words, when it is necessary to turn the axis of the tool while moving in the genera direction, etc. When obtaining the moving path in the generatrix direction, the length of each of the workpieces in the generatrix direction is divided for each predetermined length, and the position of the tool in contact with the tool and the workpiece at each division point is determined by the position of the tool. A tip position is determined, and the determined tip position of the tool at each of the division points is a path that is continuously connected.

[0022]

An embodiment of the present invention will be described below with reference to the drawings. In the drawings referred to below, components corresponding to those shown in FIG. 1 and FIGS. 18 to 21 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 2 shows a configuration of a portion including the head 11 of the 5-axis NC machine tool according to this embodiment. The head 11 is mounted on a transfer shaft 12 movably mounted on a 5-axis NC machine tool main body. This transfer shaft 12
Are driven by respective motors (not shown) for XYZ axes, which are three orthogonal axes, through a feed mechanism, respectively.
It is designed to be transported in the axis and Z-axis directions.

An approximately triangular prism-shaped first rotating member 13 having a predetermined flat inclined surface 13a moves around a C-axis parallel to the Z-axis.
The shaft motor 15 can be turned in the direction of the arrow α. Also, the inclined surface 14 which is in sliding contact with the inclined surface 13a.
a with respect to the C axis, for example, 50 °
Second rotating member 14 having an arm portion 14c extending in a direction inclined by φ, for example, 10 ° with respect to the B axis inclined by 10 °.
However, it can be turned around the B axis by the B axis motor 16 in the direction of the arrow β. The second rotating member 14
Is a flange portion 14b having the inclined surface 14a, and an arm portion 1 integrally manufactured with the flange portion 14b.
4c and a chuck fixing portion 14d fixed to one end of the arm portion 14c.

Chuck fixing portion 1 in second rotating member 14
A chuck 17 is integrally fixed to 4d. A rotary processing tool (hereinafter, also referred to as a composite R cutter) 1 having an inwardly curved arc-shaped cutting edge, which will be described in detail later, is attached to one end of the chuck 17. The tool 1 is configured to be able to rotate at a high speed, for example, about 10000 rpm or more in a direction indicated by an arrow γ or a direction opposite thereto by a tool motor (not shown).

Under such a configuration, the tool 1 is moved in the X, Y, and Z directions through the transfer shaft 12, and
First rotating member 13 rotated by C-axis motor 15
Is rotated around the C axis, and is rotated around the B axis by the second rotating member 14 rotated by the B axis motor 16.

As described above, the 5-axis NC machine tool has three orthogonal axes.
It can be said that the machine has two axes B and C that rotate around the axes X, Y and Z. The present invention can be applied to a 5-axis NC machine tool that is not an orthogonal three-axis, in other words, a three-axis that does not rotate and that does not have an orthogonal relationship and a two-axis that rotates. That is, it can be said that the present invention can be applied to a five-axis NC machine tool including at least two turning axes and three fixed axes.

FIG. 3 shows the detailed structure of the composite R cutter 1 on the cutting edge side. As can be seen from FIG. 3, the compound R cutter (sometimes called a so-called concave R cutter) 1 has an arc-shaped cutting blade 1a that curves inward. The central angle δ of the arc 51 relating to the cutting blade 1a is δ = 45 ° in this embodiment. Radius of the cutting blade 1a,
That is, the radius of the arc 51 is Rc. The end 51b of the arc 51 on the tool tip 1b side is in contact with the circumference of the tip R member (virtually drawn spherical member) 52 including the tool tip 1b. To be precise, the end 51b of the arc 51 is set to the tip 1
The line extended to the b side is the tangent to the circle relating to the tip R member 52. Similarly, the other end 51a of the arc 51 is in contact with the circumference of the outer R member 53.

As described in parentheses, the tip R member 52 is a virtual spherical member having a circular cross section in the axial direction of the tool 1, and the outer R member 53 is formed in the axial direction of the tool 1. Is a virtual ring-shaped member whose cross section is a circle,
Actually, it is formed integrally with the shaft main body of the tool 1.

In the tool 1, the cutter function is as follows.
The exposed surface of the outer R member 53, the arc 51 and the tip R member 5
2 on the exposed surface. In this case, the trajectory of the tool 1, a so-called tool path (also referred to as a processing path), has a tool tip 1b.
The tool tip trajectory data is introduced into the 5-axis NC machine tool as tool trajectory data (so-called CL data).

A work to be machined by the tool 1 mounted on the head 11 of the 5-axis NC machine tool (the work here means a work after cutting or grinding by the tool 1).
Generally has a radius of R
a ₁ , Ra ₂ , substantially opposing arc-shaped lines 111, 112
And substantially opposite ends 111a, 112a and ends 111b, 112 of these two arc-shaped lines 111, 112.
b, two bus-like lines (straight lines or curves) 11
3, a workpiece 2 having a curved surface (also referred to as a curved surface) 115 defined by 114.

As described above, it is assumed that the curved surface 115 is a set of so-called R-shaped lines, that is, arcs having a constant or changing radius are continuously arranged in the generatrix direction Q. In FIG. 1, the radius Ra of the arc 111 on the near side of the curved surface 115 is Ra = Ra ₁ , and the radius Ra of the arc 112 on the back side is Ra = Ra ₂ . Also,
In FIG. 1, the generatrix lines 113 and 11 of the curved surface 115 are shown.
Surfaces 116 and 117 that are in contact with 4 are flat surfaces.
Even if there are irregularities, each end 1 of each arc 111, 112
11a, 111b, 112a, 112b to surface 116,
It is assumed that the projection has only a convex portion lower than the surface formed by the tangents of the arcs 111 and 112 drawn toward the 117 side.

FIG. 4 shows the configuration of an NC data creation system 21 to which an embodiment of the present invention is applied. This NC data creation system 21 includes an NC data creation unit 22
have. The NC data creation unit 22 stores a database 23 storing tool data Td for work machining.
, And workpiece shape data Wd from a database 23 in which workpiece shape data Wd created in advance for the workpiece 2 are stored.

The NC data generator 22 is a 5-axis NC which is trajectory data of the tip 1b of the composite R cutter 1 based on the supplied data and the like, that is, so-called CL data.
To create a data N _5. 5-axis NC data N ₅ created
It is stored in a database 26 for storing the 5-axis NC data N _5. The databases 23, 24, 26 are
Each of them is a storage unit such as a hard disk, and it goes without saying that the configuration may be changed to a configuration in which one storage unit is shared.

The NC data creation unit 22 is a computer, and as is well known, a central processing unit (CPU), an I / O port connected to the central processing unit, a read-only memory in which a system program and the like are written. (RO
M), random access memory (RAM, write / read memory) for temporarily storing processed data,
5-axis NC data N external memory by the application program was written ₅ such 5-axis NC data creation program graphic processing program to create a tablet 32 for a digitizer, a mouse 34, a keyboard 33 and an input such as a volume switch 35 Device, display 3
1. It has an output device such as a plotter or printer (not shown).

Next, the operation of the above embodiment will be described with reference to the flowcharts of the 5-axis NC data creation program shown in FIGS. The control entity is the NC data creation unit 22 unless otherwise specified.

First, the NC data generator 22 fetches the tool data Td from the database 23 (step S).
1). In this embodiment, the contents of the tool data Td are:
The tool 1 is the composite R cutter 1 described with reference to FIG. 3, and the radius Rc of the arc 51 having the central angle δ = 45 ° is Rc = 3.0R,
4.0R, 5.0R, 6.0R, 8.0R, 10.0
R, 12.0R, and 15.0R indicate that the data is for eight lines.

Next, the NC data creation section 22 reads the work 2
Is taken in (step S2).
In this embodiment, since the work 2 is a press die, the work 2 also takes in the thickness t of the pressed product. The thickness t of the pressed product may be input from the keyboard 33. In this embodiment, the thickness t is 0.7 mm. Since the press die is basically composed of a lower die (die) and an upper die (punch), for example, when forming an inwardly curved arc surface of the upper die, the corresponding lower die is formed. The radius of the outwardly curved arc surface of the mold may be increased by the thickness t of the pressed product.

The shape of the work 2 is as shown in FIG. 1, but here, in order to facilitate understanding of the working method of the present invention, FIG. The description will be made on the basis of the curved surface 215 having a simple configuration as shown in the drawings. In the description of the processing method for the curved surface 215, when the processing method for the curved surface 115 of FIG. This will be described with reference to FIG.

The curved surface 215 includes an arc 211 having a radius Ra,
212 and the ends 211a, 21 of the arcs 211, 212
A bus 213 connecting each of 2a, 211b, and 212b;
214. Also, the planes 216 and 217 connected to the buses 213 and 214 respectively
1, 212 end 211a, 212a, 211b, 21
2b is a plane formed by a tangent line extending outward and the buses 213 and 214.

When the radius (radius of the outwardly curved arc) Ra of the curved surface 215 is read, the radius (radius of the inwardly curved arc) Rc of the composite R cutter 1 is calculated as follows: Rc> Ra (basic selection criterion of the tool radius) (The process of selecting the tool radius based on the basic selection criteria of the tool radius: Step S)
3). If the radius Rc of the tool 1 is equal to the curved surface 21 of the work 2
When the radius Ra is smaller than 5, the work 2 is excessively cut, that is, a so-called overcut portion OC (see a dotted portion in FIG. 8) occurs. If the radius Rc of the tool 1 is too large compared to the radius Ra of the work 2, the machining balance after cutting or grinding (so-called cusp height) Δh may be too large.

Therefore, it is necessary to set the tool 1 having an appropriate radius Rc corresponding to the radius Ra of the work 2. Of course, when the radius Ra of the work 2 is different in the generatrix direction Q like the curved surface 115 shown in FIG. 1, the maximum radius of the arc related to the curved surface 115 (referred to as Ramax).
It is necessary to select a tool 1 having the above radius Rc.

The center angle ε of the arcs 211 and 212 of the work 2 (see FIG. 7) is preferably
Is larger than the central angle δ of the circular arc 51 (see FIG. 3). In this embodiment, since the central angle δ is 45 °, the central angle ε is 4 °.
An angle between 5 ° and less than 360 ° is selected.

In FIG. 7, the direction indicated by the arrow P is the step feed direction of the tool 1, but this may be the direction opposite to the direction of the arrow P, or the step feed may be performed in any one of the directions. Therefore, it is also referred to as the step feed direction P instead of the arrow P direction. The direction indicated by the arrow Q is the processing scanning direction (the direction of the generating line) of the tool 1, and
This is because, for each processing scan, for example, the first processing scan is performed in the direction of arrow Q, the processing scan at the next position after the step feed is performed in the direction opposite to arrow Q, and further step feed is performed. In addition, the processing scan at the next position may be performed in the direction of arrow Q, for example, so-called zigzag feed, or the processing scan direction may be limited to only one direction of arrow Q shown in FIG. . It is also referred to as the processing scanning direction Q instead of the arrow Q direction. Hereinafter, the directions (directions) of the arrows P and Q
May be changed depending on the drawings for convenience of understanding of the invention.

After the machining scan in the direction of arrow P is completed, the tool 1
May be retracted in the tool axis direction to avoid interference with the work 2, step-feed to the next machining scan start position, and return the tool 1 to the work direction at the machining scan start position.

Next, the method of selecting the tool 1 based on the allowable setting value of the machining balance Δh (see FIGS. 20 and 21) and the step feed (intermittent feed) of the tool 1 in the direction of arrow P (see FIG. 7). - discontinuous feed) times the number of the setting method will be described. Incidentally, when the step feed count is set to n times (hereinafter, number
In the equation, the number of step feeds is represented by n. ) , The number of machining movements (scans ) of the tool 1 in the generatrix direction Q is automatically set to n + 1. Conversely, when the number of machining scans of the tool 1 is m (hereinafter, the number of machining scans in the formula is m)
Represent. ), Step feed times the number is automatically set to n = m-1 times.

Then, the value of the allowable processing balance (allowable processing balance) Δhp (not shown) is input (step S4). In this embodiment, for example, Δhp = 0.
001 shall be input.

In practice, as shown below, the work radius Ra, the work center angle ε, the tool radius Rc, and
Number {or step feed times the number (n = m-1)} working balance of Δh from is uniquely determined. Therefore, the table of the number of processing scans CPT calculated in advance based on these parameters is stored in the storage means of the NC data creation unit 22. A method of creating the processing scan number setting table CPT will be described later.

[0049] Figure 9, step feed times the number once, in other words, the machining scanning times count control processing balances of Δh and orientation relative to the workpiece 2 in the composite R cutter 1 occurs when the two described like FIG.

As shown in FIG. 9, first, the work 2 and the composite R cutter 1 shown by a solid line are
The end 1 51b of the circular arc 51 is in contact with the end 211b of the circular arc 211 of the workpiece 2, and the tool 1 is maintained in that state and the tool 1 is moved in the generatrix direction Q (in the drawing, the direction perpendicular to the paper surface).
The first scanning or grinding of the work 2 is performed. In this case, at the position E, the tangent vector tb at the end 51 b of the arc 51 and the arc 21
The tool 1 is arranged so that the tangent vector tb at the end 211b of the tool 1 matches.

After the first machining scan, the tool 1 is step-fed in the direction of arrow P (the direction of the arc of the work 2), and is arranged at the position of the tool 1 indicated by a dashed line. That is, at the position (contact point) F, the end 51a of the arc 51 of the tool 1 and the workpiece 2
The tool 1 is placed at a position where the tangent vector ta at the end 51a of the arc 51 and the tangent vector ta at the end 211a of the arc 211 coincide with each other. In this positional relationship, the workpiece 2 is moved for scanning in a direction perpendicular to the paper surface (general direction Q), and the second or in this case, the last cutting or grinding is performed on the work 2. When scanning is performed in this manner, as shown in FIG. 9, a maximum machining balance Δh occurs on a bisector L of the central angle ε of the arc 211 of the workpiece 2.

[0052] Figure 10, when the processing of FIG. 9 example, in other words, step feed times the number once, in other words, subject to the description of the processing balance of Δh number processing scan times occurs when the two FIG. In FIG. 10, components corresponding to those shown in FIG. 9 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 10, the symbol CC is the center of the circle relating to the arc 51 when the tool 1 is at the position of the solid line, and the symbol CT is the center of the circle relating to the arc 211 of the workpiece 2.

When mathematically considered with XY coordinates, the following (1)
As shown in the equations (2) and (3), the equations of the arc 51 of the tool 1, the equation of the bisector L of the central angle ε, and the equation of the arc 211 of the workpiece 2 shown by solid lines are obtained, respectively. Can be

Equation of arc 51 of tool 1 shown by solid line {x + (Rc-Ra)} ² + y ² = Rc ² (1) Equation of bisector L of central angle ε y = {tan (ε / 2) )｝ · X (2) Equation x ² + y ² = Ra ² (3) of the arc 211 of the work 2 Here, the machining balance Δh is determined by the coordinates J at the intersection of the arc 211 and the bisector L. , The distance between the coordinates K of the intersection of the arc 51 and the bisector L.

The intersection coordinates J are obtained by the equations (3) and (2). The intersection coordinates K are obtained by the equations (1) and (2). Therefore, the distance between the coordinates J and the coordinates K, that is, the machining balance Δh can be obtained.

[0057] In FIG. 10 example, step feed times number one,
That is, when the number of processed scan times is 2 times working balance of Δh
Is explained, but the step feed
Number n times in the case of (the number of processed scan gyrus n + 1 times), Similarly, to determine the working balance of Δh by placing a central angle ε the angle between the contact point E and F of the working scanning lines adjacent Can be.

[0058] Based in these considerations, in advance, the other parameters the relationship machining balance is calculated in a computer Δh and processed scan times count {or step feed times the number (n = m-1)} , i.e., FIG. 11 shows the work radius Ra, the work center angle ε, and the tool radius Rc.

FIG. 11 shows a processing scan number setting table CPT.
It is a figure which shows a part of.

For example, the radius Ra of the arc 211 of the work 2
Is set to an accuracy of Ra = 4, the central angle ε of the workpiece 2 is ε = 45 °, and the allowable machining balance Δhp is set to an accuracy of Δhp = 0.01, the numerical value in the machining scan frequency setting table CPT of FIG. as shown at points where the lines, combined R radius Rc of the cutter 1 of the arc 51 is intended Rc = 5 is automatically selected, and processed scan times count (step feed count
However, it is understood that n = m-1) is automatically set to m = n + 1 = 4 (step S5).

[0061] Here, the allowable working on the basis of the balance of Δhp etc., when the processing number of scans setting table processing scan times count referenced to set the CPT three times (step feed times the number of 2 times), and 4 times The determination of the step feed position (each processing scan start position) in the case of (3 times) will be described.

[0062] Figure 12 is a diagram number processing scan times is subjected to the description of the case of three times (step feed times the number of 2 times). In this case, first, one end 211b of the outwardly curved arc 211 of the workpiece 2 and the end 51b of the inwardly curved arc 51 of the tool 1 shown by a solid line on the tool tip 1b side are at the contact point E and the respective tangent vectors coincide. To distribute. With this positional relationship, the tool 1 is moved in the generatrix direction (direction orthogonal to the paper surface) Q to
Of the partial curved surface 215a (see FIG. 13). Thus, in the composite R cutter 1, surface processing can be performed on the processing surface.

Next, the central portion 21 of the circular arc 211 of the workpiece 2
1c (the intersection of the bisector L of the central angle ε with the arc 211) and the central portion 51c of the arc 51 of the tool 1 ｛the arc 51 and the central angle δ
The tool 1 is step-moved in the direction of the arrow P to a positional relationship where each normal vector coincides with a point of intersection Gc with the bisector L of FIG. 3 (see FIG. 3). The tool 1 is moved in the generatrix direction Q in accordance with the positional relationship, that is, the positional relationship between the tool 1 and the work 2 indicated by a dashed line, and the central partial curved surface 215b (see FIG. 13) adjacent to the partial curved surface 215a is moved. Process.

Finally, like the tool 1 shown by the two-dot chain line,
The other end 211a of the circular arc 211 of the work 2 and the terminal 51a of the circular arc 51 of the tool 1 outside the tool 51 (on the side of the outer R member 53) are step-feeded until the contact point F and the tangent vectors coincide with each other. With the positional relationship, the tool 1 is moved in the generatrix direction Q to machine the remaining partial curved surface 215c (see FIG. 13) adjacent to the central partial curved surface 215b. Thereby, the entire curved surface 215 of the work 2 is processed. In this case, the part where the partially curved surface 215a and the partially curved surface 215b after processing are in contact with each other and the partially curved surface 215b
A machining residue Δh (not shown) occurs in a portion where the and the partially curved surface 215c are in contact with each other. Similarly, FIG. 14 is a diagram number processing scan times is subjected to the description of the case of four times (step feed times the number of 3 times). In this case, the arc 211 of the work 2
The tool 1 is moved in the generatrix direction Q in such a positional relationship that the tangent vector coincides with the ending point 211b of the tool 1 and the ending point 51b of the arc 51 of the tool 1 to form a partially curved surface. Next, the trisection point 211d of the arc 211 of the workpiece 2, the trisection point 51d of the arc 51 of the tool 1, the other three
Equivalent point 211e and other trisector 51 of arc 51 of tool 1
e is sequentially stepped so that the respective normal vectors coincide at the contact points G1 and G2, and moves in the generatrix direction Q in each of the stepped positional relationships to sequentially process the partially curved surface. The terminal 211a of the circular arc 211 and the terminal 51a of the circular arc 51 of the tool 1 are stepped forward until the respective tangent vectors coincide with each other at the contact point F, and the tool 1 is moved in the generatrix direction Q based on the positional relation and the final By processing the partially curved surface, the entire curved surface 215 is processed.

As understood from FIGS. 12 and 14,
The positions of the contacts G _C , G ₁ , G _2, etc.
When the central angle of 1 is ε and the number of step feeds is n (the number of processing scans is m), it is only necessary to set ε / n = ε / (m−1).

[0066] Step feeding times the number of the arc direction P determined in step S5 is 3 times, processing the scan times of the generatrix orientation Q
Assuming that the number is four, tool trajectory data, which is 5-axis NC machining data for the workpiece 2 having the curved surface 115 shown in FIG. 1 in which the radius Ra changes in the generatrix direction Q, in other words, For example, a process of obtaining trajectory data of the tip 1b of the composite R cutter 1 will be described. The trajectory data of the tip 1b of the composite R cutter 1 includes a tip position (also referred to as tip position data) SP and a tilt angle (referred to as tilt angle position data) SA of the composite R cutter 1. The tip position SP and the inclination angle SA together are called a tip position vector SV. The tip position vector SV (not shown) is represented by SV = SV (SP, SA).

In this case, first, as shown in FIG. 15, the three-dimensional position data of a generatrix line (hereinafter also referred to as a scanning line) 114 is read (step S6). Then, the scanning line 114 is divided into a plurality of parts in the generatrix direction Q which is the scanning line direction (step S7). This division may be an equal division, and is performed based on a tolerance such as each time the derivative in the direction of the scanning line 114 changes by a predetermined amount or more, or another appropriate parameter. This is because the tip position SP and the inclination angle SA of the composite R cutter 1 are changed for each division point so that processing corresponding to the curved surface 115 can be performed. here,
For convenience, the dividing point Pa on the scanning line 114 is represented by a point Pa = Pa ₀
And 100 points to ~Pa _99.

Therefore, first, Pa → Pa ₀ is set in order to obtain the tip position vector SV0 at the point Pa ₀ (step S8).

Next, a tangent vector 301 (see FIG. 16) of the arc 111 is calculated at the point Pa ₀ (step S9).

Next, as described with reference to FIG.
End 51b of the tool 1 in tangent vector 301 at point Pa ₀
And the tangent vector of the arc 51 to the tangent vector 301 (step S10).

In this state, the tip position vector SV of the composite R cutter 1 is calculated (step S11). This calculation method will be described later.

[0072] Then, a point to point Pa of the next Pa → P _{a + 1} (in this case, Pa ₁₎ as (step S11), and the point P _{a + 1}
Is calculated until Pa ₉₉ (Step S12), the tip position vector SV at each point Pa is calculated (Steps S9 to S9).
Step S13).

The combination of these tip position vectors SV calculated for the scanning line 114 becomes the tool path data of the composite R cutter 1 related to the scanning line 114.

Next, tool path data of the composite R cutter 1 relating to the scanning line 151 is obtained (step S13). In this case, the processing in step S9 described above is performed as shown in FIG.
As described with reference to the above, the processing in step S10 described above is changed to the processing for obtaining the normal vector 302 (see also FIG. 16) at the trisection point of the arc 111, and Normal vector at point and compound R
Instead of the process of matching the normal vector at the trisection point of the arc 51 of the cutter 1, the tip position vector SV may be calculated (step S14). In this manner, the tool trajectory data of the composite R cutter 1 relating to the scanning line 151 can be obtained.

The tool trajectory data for the scanning line 152 may be created based on the normal vector 303 (see FIG. 16) in the same manner as the tool trajectory data creation process for the scanning line 151 (step S14).

The tool trajectory data for the scanning line 113 can be created by performing a process based on the tangent vector 304 (see FIG. 16) as in the process of creating the tool trajectory data for the scanning line 114 (step S15).

Generally, when obtaining tool trajectory data relating to scanning lines on both ends of an outwardly curved arc of a work, processing based on a tangent vector between the work and the tool is performed, and a dividing point in the arc direction of the work is obtained. In order to obtain tool trajectory data for a scanning line passing through, processing based on a normal vector of a workpiece and a tool may be performed.

FIG. 17 is a diagram for explaining a method of calculating the tip position vector SV (not shown).

When the tool G and the workpiece 2 are in contact with each other at the contact point G ₂ with their normal vectors being coincident, the position SP of the tip 1 b of the tool 1 will be considered.

The coordinates of the contact point G ₂ are, for example,
(See FIG. 16) Since these are the coordinates above, they have already been obtained by matching the normal vectors at the division points between the work 2 and the tool 1. Then, the coordinates of the position SP of the tip 1b, offset from the position of the length dx amount corresponding contact G ₂ of the length dy and the perpendicular on the dividing line L when minus perpendicular line dividing line L from the tip 1b It can be seen that the position should be set. Further, the inclination angle SA of the tool 1 is:
The angle between the axis 1 _CL of the tool 1 and the dividing line L. In FIG. 17, it is easily understood that the following equations (4) to (7) hold.

Cy = (Rt + Rc) sin ω ₁ −Rt (4) cx = (Rt + Rc) cos ω ₁ (5) ω = arctan (cx / cy) (6) cd = (cx ² + cy ² ) (7) ) When the step feed count is n times, parakeratosis da tilt angle SA with respect to the contact G ₂ is obtained by equation (8).

Da = (90−ω ₁ ) / n (8) Therefore, the lengths dx and dy to be offset are:
They can be obtained by equations (9) and (10), respectively.

Dx = cd · sin (ω−da) (9) dy = Rc−cd · cos (ω−da) (10) It goes without saying that SA = da.

Similarly, the lengths dx and dy to be offset and the inclination angle S for the other contact points G ₁ , E and F are also set.
A can be obtained.

[0085] In this way, each division point Pa _0, Pa ₁ on the bus orientation Q, ..., the tip 1 of the tool 1 in Pa ₉₉
b obtains a coordinate Dp of, storing the data in which the these, tool path data for each scanning line are created, it is stored in the database 26 as a 5-axis NC data N _5. The created 5-axis NC data N ₅ is supplied to an arithmetic control unit (not shown) constituting a 5-axis NC machine tool having the 5-axis head 11 shown in FIG. A servo mechanism (not shown) constituting the machine operates, and the servo mechanism (not shown) is turned on by a feed mechanism (not shown).
The shaft head 11 can perform a desired operation, for example, cutting or grinding a curved surface formed of an outwardly curved arc of a press die for each partial curved surface.

Before supplying the 5-axis NC data N ₅ to the arithmetic control unit constituting the 5-axis NC machine tool, the NC data creation system 21 uses the tip position vector of the tool 1 based on the 5-axis NC data N _5. By processing the trajectory graphically and displaying it on the display 31 together with the work 2, it is also possible to perform a simulation before actually grinding or cutting the work 2. The trajectory of the tip position 1b may be corrected by the simulation.

As described above, according to the above-described embodiment, it is possible to easily create the tool trajectory data when processing the work 2 having the curved surface 115 by the composite R cutter 1.
In other words, 5-axis NC data N for 5-axis NC machine tool
₅ can be easily created. Further, since machining can be performed for each partially curved surface, the machining time can be reduced, the surface accuracy of the machined surface can be improved, and the burden of finishing work by the operator can be greatly reduced.

The present invention is not limited to the above-described embodiment.
It goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0089]

As described above, according to the present invention, an outwardly curved surface of a workpiece is formed by a rotary working tool having an arc-shaped inwardly curved surface having a radius larger than the radius of the arc of the outwardly curved surface. When performing cutting or grinding (including from roughing to polishing), set the allowable processing balance in the arc direction of the work, the length of the outwardly curved arc of the work, and the length of the inwardly curved arc of the tool in the generatrix direction of the work. Is determined (the number of step feeds in the direction of the outwardly curved arc of the work + 1).
The workpiece is machined according to the determined number of times of movement in the generatrix direction. Since the number of processing scans (the number of step feeds) is determined in relation to the processing balance, which is an appropriate and important index when processing a workpiece, the processing time and
The effect is obtained that a processing method with good visibility of the processing result such as processing accuracy can be achieved.

Further, according to the present invention, the tool is moved in the generatrix direction with the one arc end of the tool aligned with the one arc end of the work to machine the partially curved surface. Equivalent point on the arc divided by the number of step feeds and the arc of the tool divided by the number of step feeds
Stepwise in the direction of the arc so as to sequentially match the equidistant points of the workpiece, move the tool in the direction of the generatrix for each step feed, and sequentially process the partially curved surfaces that are adjacent to each other. The tool is moved in the generatrix direction with the end and the other arc end of the tool aligned to machine the entire curved surface of the work.

In this case, it is possible to cut or grind the outward curved surface of the workpiece on the inwardly curved surface of the rotating tool, that is, a surface having a high peripheral speed. The effect is achieved. Since the processing is performed for each surface, the effect that the processing time can be shortened is also achieved.

Further, according to the present invention, when there are irregularities in the generatrix direction of the outwardly curved surface of the workpiece (irregularities such that the inclination of the tangent changes continuously), that is, the generatrix lines are not straight but smooth. When the curve is a simple curve, or even if it is a straight line, the adjacent genera direction is not a parallel line (when it is necessary to turn the axis while moving in the genera direction), the respective genera direction of the tool When determining the movement path to the work, the length of each of the workpieces in the generatrix direction is divided for each predetermined length, and the tip position of the tool is determined from the positional relationship between the tool and the work at each division point. The determined and determined end positions of the tool at each of the division points are continuously connected.

In this way, even if the movement in the generatrix direction involves the rotation of the 5-axis NC machine tool, the machining path, that is, the 5-axis NC data is automatically and therefore easily converted. The effect of being able to create is achieved.

The present invention is suitable for application to the production of a press die (work) for producing an outer plate having a smooth curved surface such as an automobile.

[Brief description of the drawings]

FIG. 1 is a diagram provided for describing a work having a curved surface processed by a 5-axis NC machine tool.

FIG. 2 is a perspective view showing a configuration of a part including a head of a five-axis NC machine tool to which the present invention is applied.

3 is a composite R mounted on the 5-axis NC machine tool shown in FIG. 2;
It is a figure showing composition of a cutter.

FIG. 4 is a block diagram showing a configuration of a 5-axis NC data system according to one embodiment of the present invention.

FIG. 5 is a flowchart (1/2) illustrating a process mainly performed by an NC data creation unit in FIG. 4;

FIG. 6 is a flowchart (2/2) showing a process mainly performed by the NC data creating unit in FIG. 4;

FIG. 7 is a diagram showing a curved surface used for explaining the operation of the embodiment.

FIG. 8 is a diagram provided for describing overcut of a work by a composite R cutter.

FIG. 9 is a diagram provided to explain an operation of processing the work in a direction orthogonal to the paper surface by step-feeding the composite R cutter once.

FIG. 10 is a diagram provided for explaining a processing balance in the case of FIG. 9;

FIG. 11 is a diagram illustrating an example of a machining scan number setting table set in a memory of an NC data creating unit.

FIG. 12 is a diagram provided to explain an operation of processing a workpiece in a direction orthogonal to the paper surface by step-feeding the composite R cutter twice.

13 is a diagram which is used for describing the processing order of the partially curved surface in the case of the example of FIG. 12;

FIG. 14 is a diagram provided to explain an operation of processing a workpiece in a direction orthogonal to the paper surface by step-feeding the composite R cutter twice.

FIG. 15 is a diagram provided for describing division of a generatrices line;

FIG. 16 is a diagram provided for explanation of a tangent vector and a normal vector on a curved surface;

FIG. 17 is a diagram which is used for describing the calculation of the tip coordinates of the tool from the coordinates of the contact position between the workpiece and the tool.

FIG. 18 is a diagram which is provided for explanation when processing a workpiece with a ball end mill of a three-axis NC machine tool.

FIG. 19 is a diagram provided for explanation when processing a workpiece with a ball end mill of a 5-axis NC machine tool to which a conventional technique is applied.

FIG. 20 is a diagram which is provided for explaining remaining machining and the like when a workpiece is machined by the three-axis NC machine tool of the example of FIG. 18;

FIG. 21 is a diagram which is used for explaining remaining machining and the like when a workpiece is machined by the 5-axis NC machine tool of the example of FIG. 19;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Tool (composite R cutter) 2 ... Work 11 ... Head 21 ... NC data creation system 22 ... NC data creation part 115, 215
…… Curved surface ε… Central angle of convex arc part of work δ… Central angle of concave arc part of tool Δh… Working balance CPT… Working scan frequency setting table N ₅ … 5 axis NC data P… Circular direction (step feed direction) ) Q: Generic line direction Ra: Radius of convex arc part of work Rc: Radius of concave arc part of tool

Continuation of the front page (72) Inventor Yukio Yajima 1-10-1 Shinsayama, Sayama-shi, Saitama Honda Engineering Co., Ltd. (72) Inventor Toshio Koishi 1-10-1 Shin-Sayama, Sayama-shi, Saitama Honda Engineering Co., Ltd. (56) References JP-A-5-96447 (JP, A) JP-A-6-266429 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23Q 15/00-15 / 28 G05B 19/18-19/46

Claims (4)

(57) [Claims] When cutting or grinding an outwardly curved surface of a work with a rotary processing tool having an inwardly curved arc-shaped cutting edge, the tool is moved in a generatrix direction of the work to partially cut the surface. Machining a curved surface, and then step-feeding the tool in an arc direction substantially orthogonal to the generatrix direction, moving the tool again in the generatrix direction at the position of the step feed, and adjoining the partial curved surface. In a machining method using a 5-axis NC machine tool, which processes a partially curved surface to be processed and repeats these steps to machine the entire outer curved surface of the workpiece, a radius of the inwardly curved arc of the tool is: Selecting a tool having a radius equal to or greater than the radius of the outwardly curved arc of the work; and allowing the length of the outwardly curved arc of the work, the length of the inwardly curved arc of the tool, and the direction of the arc of the work. Based on Engineering balance ri, and determining the step feed count, five-axis NC machine tool according to a processing method characterized by comprising a processing step of processing the workpiece at step feed count of the determined. 2. The method according to claim 1, wherein when the determined number of step feeds is one, first, one end of the outwardly curved arc of the workpiece and a tool outer end of the inwardly curved arc of the tool. The tool is moved in the generatrix direction in a positional relationship where the tool is in contact with the workpiece to machine a partially curved surface, and then the other end of the inwardly curved arc of the work and the tool of the inwardly curved arc of the tool are processed. By step-feeding to the positional relationship where the distal end portion contacts, the tool is moved in the generatrix direction in accordance with the positional relationship and the remaining partial curved surface is machined to process the entire outer curved surface, and is determined. When the number of step feeds is two, first, the tool is connected to the bus-line in a positional relationship where one end of the outwardly curved arc of the workpiece and the tool outer end of the inwardly curved arc of the tool are in contact with each other. Move in the direction and partially curve Machining a surface, and then step-feeding to a positional relationship where the central portion of the outwardly curved arc of the workpiece and the central portion of the inwardly curved arc of the tool are in contact with each other. In the target direction to process the central partial curved surface,
Further, the workpiece is step-feeded to a positional relationship where the other end portion of the outwardly curved arc of the work and the tool distal end portion of the inwardly curved arc of the tool are in contact with each other, and the tool is moved in the bus direction in the positional relationship. When the determined number of step feeds is three or more , first, one end of the outwardly curved arc of the workpiece is processed by processing the remaining curved surface to process the remaining partially curved surface. said the tool in a positional relationship where the inner curved arc of the tool outer end portion of the tool is in contact moves in the generatrix orientation and processing the partially curved surface, then, before the outer curved arc of the work
The equidistant points on the outwardly curved arc divided by the number of step feeds and the inwardly curved arc of the tool are calculated by the number of step feeds.
Stepwise until the divided points on the inwardly curved arc are successively in contact with each other, and sequentially move the tool in the generatrix direction at each of the stepwise positional relationships to sequentially machine the partially curved surface, and Step-feeding to a positional relationship where the other end of the outwardly curved arc of the workpiece and the tool distal end of the inwardly curved arc of the tool are in contact, and the tool is moved in the generatrix direction in that positional relationship. 2. The machining method according to claim 1, wherein the entire outer curved surface is machined by moving and machining the last partially curved surface. 3. In the machining step, when the determined number of step feeds is one, first, one end portion of the outwardly curved arc of the workpiece and a tool tip end of the inwardly curved arc of the tool. The tool is moved in the generatrix direction in a positional relationship where the part is in contact with the workpiece to machine a partially curved surface, and then the other end of the inwardly curved arc of the work and the inwardly curved arc of the tool are processed. By step-feeding to the positional relationship where the outer end portion of the tool is in contact with the tool, the tool is moved in the generatrix direction in the positional relationship and the remaining curved surface is machined to process the entire outer curved surface. When the number of step feeds is two, first, the tool is connected to the bus bar in a positional relationship in which one end of the outwardly curved arc of the workpiece is in contact with a tool tip end of the inwardly curved arc of the tool. Move to the target bay A curved surface is machined, and then step-feeding is performed to a positional relationship where the central portion of the outwardly curved arc of the workpiece and the central portion of the inwardly curved arc of the tool are in contact with each other, and the tool is connected to the bus with the positional relationship. Moving the workpiece in the target direction to process the central partial curved surface, and further step until the other end of the outwardly curved arc of the work contacts the outer end of the tool of the inwardly curved arc of the tool. Feed, the tool is moved in the generatrix direction in the positional relationship, and the entire outer curved surface is machined by machining the remaining partial curved surface. When the determined number of step feeds is three or more , first, Processing the partially curved surface by moving the tool in the generascopic direction in a positional relationship where one end of the outwardly curved arc of the workpiece and the tool distal end of the inwardly curved arc of the tool are in contact with each other. And then the work Said outer curved arc
The dividing point on the outwardly curved arc divided by the number of step feeds and the inwardly curved arc of the tool are divided by the number of step feeds.
The stepwise feeding is sequentially performed until the equidistant points on the inwardly curved arc divided by the above are sequentially in contact with each other, and the tool is moved in the generatrix direction at each of the stepped positional relationships to sequentially machine the partially curved surface, Further, the workpiece is step-fed to a positional relationship where the other end of the outwardly curved arc of the workpiece and the outer end of the tool of the inwardly curved arc of the tool are in contact with each other, and the tool is moved in the generatrix direction in the positional relationship. 2. The machining method according to claim 1, wherein the entire outer curved surface is machined by moving and machining the last partially curved surface. 4. The moving path of the tool in each of the generatrix directions divides the length of the workpiece in the generatrix direction by a predetermined length, and separates the tool from the workpiece at each division point. The tip position of the tool is determined from the contacting positional relationship, and the determined tip position of the tool at each of the division points is a path that is continuously connected, according to any one of claims 1 to 3, wherein A machining method using the 5-axis NC machine tool described in the above.