JPH10113846A - Cutting method, cutting data preparing method and program record medium for preparing cutting data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform well cutting by keeping cutting resistance nearly constant while maintaining tool rotation speed and feed rate constant even for three dimensional curved surface. SOLUTION: The cut volume Vn of each reference travel when finishing is calculated (S4), and the amount of feed in the normal line direction of the desired product shape is corrected so that the cut volume Vn becomes nearly constant (S5). This constitution produces a shape before finishing so that the cut volume Vn when finishing becomes nearly constant (S6). Prior to finishing, a workpiece member is perliminarily cut so as to become a shape before finishing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting method, a cutting data creating method, and a program recording medium for creating cutting data, and in particular, always performs proper cutting regardless of a change in the shape of a machining portion. It is related to the technology to be used.

[0002]

2. Description of the Related Art A rotary cutting tool is rotated around an axis while being relatively moved with respect to a workpiece including a direction intersecting the axis, thereby cutting the workpiece into a predetermined product shape. Is widely performed in various fields such as mold processing. As the rotary cutting tool, various types of milling machines such as a ball end mill are preferably used. Such a rotary cutting tool is generally mounted on an automatic cutting device such as an NC (numerical control) machine tool or a machining center, and is used for forming a product. , The workpiece is relatively moved with respect to the workpiece according to the movement path data set in advance, so that the workpiece is cut by the cutting edge provided on the outer periphery.

[0003] One type of cutting method using such an automatic cutting apparatus is as follows: (a) The rotary cutting tool is driven relative to the workpiece at a constant feed speed while being driven to rotate at a constant rotational speed. And (b) preliminary cutting the workpiece prior to the final cutting step so that the cutting resistance in the final cutting step is constant. And a preliminary cutting step. JP-A-8-2517
The method described in Japanese Patent Publication No. 8 is an example of the method, in which a tool moving path in a preliminary cutting process is set based on a radius of curvature of a product shape, a tool diameter, and the like so that a cutting amount at a corner portion is constant. It has become so.

[0004]

However, in the cutting method for setting the tool moving path so that the cutting amount in a two-dimensional plane perpendicular to the tool axis is constant as described above,
It could not be applied when cutting a three-dimensional curved surface.

[0005] It has been proposed to control the feed rate to keep the cutting resistance constant, but the feed amount per tooth is changed, so that the machined surface roughness deteriorates. It is conceivable to control the tool rotation speed (spindle speed) in accordance with the feed speed so that the feed amount per blade is constant. However, since the time constants of the main shaft and the feed shaft are different, the actual one blade It is difficult to make the per-feed amount constant.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to keep the cutting force substantially constant while maintaining the tool rotation speed and the feed speed constant even for a three-dimensional curved surface. It is to maintain a good cutting process.

[0007]

In order to achieve the above object, a first aspect of the present invention is to rotate a rotary cutting tool about an axis while including a direction intersecting the axis with respect to a workpiece. A cutting method for cutting the member to be processed into a predetermined product shape by relative movement,
(a) a finish cutting step in which the rotary cutting tool is relatively driven with respect to the workpiece at a constant feed speed while being rotationally driven at a constant rotation speed, and the workpiece is finish-cut into the product shape. (B) a preliminary cutting of the workpiece prior to the finishing cutting step, so that the cutting volume of the rotary cutting tool at the predetermined number of cuttings at the time of the finishing cutting becomes substantially constant or gradually decreases. And a cutting step.

According to a second aspect of the present invention, an automatic cutting apparatus rotates a rotary cutting tool about an axis while relatively moving the rotary cutting tool relative to a workpiece including a direction intersecting the axis. A method of creating cutting data for performing a predetermined cutting process on a member, according to predetermined finish cutting data, while rotating the rotary cutting tool at a constant rotation speed and at a constant feed speed. By relatively moving the workpiece relative to the workpiece, prior to finish-cutting the workpiece into a predetermined product shape, the cutting volume of the rotary cutting tool at the time of the predetermined number of cuts during the finish cutting is substantially reduced. The method further comprises a preliminary cutting data generating step of generating preliminary cutting data for preliminarily cutting the workpiece to be constant or gradually decreasing.

[0009] A third aspect of the present invention is to rotate the rotary cutting tool about an axis by an automatic cutting apparatus and relatively move the rotary cutting tool with respect to a workpiece including a direction intersecting the axis, thereby forming the workpiece. A recording medium for a cutting data creation program for creating cutting data for performing predetermined cutting on a member by a computer, wherein the rotary cutting tool is rotated at a constant speed in accordance with predetermined finishing cutting data. By rotating relative to the workpiece at a constant feed speed while rotating and driving at a speed, prior to finish-cutting the workpiece to a predetermined product shape, the rotation during the finish cutting is performed. Preliminary cutting data for preliminarily cutting the workpiece is created so that the cutting volume of the cutting tool every predetermined number of cuts becomes substantially constant or gradually decreases. Wherein the order of the program is recorded.

[0010]

According to the present invention, the work is performed prior to the finish cutting so that the cutting volume of the cutting edge of the rotary cutting tool at the time of the finish cutting is substantially constant or gradually reduced at the time of the finish cutting. Since the members are pre-cut, the cutting resistance in the finishing cutting process, in which cutting is performed at a constant rotation speed and a constant feed speed, becomes substantially constant or gradually decreases, and the elastic deformation of the rotary cutting tool and a holding mechanism for holding the same. An excellent finished surface accuracy can be obtained without a step due to a change in the amount or a cusp change due to a change in the feed amount per blade. If the cutting force is substantially constant, the amount of elastic deformation is substantially constant, so that no step is produced.However, even when the cutting force gradually decreases, the change in elastic deformation is more gradual than when it increases. And a step is unlikely to occur. In addition, since the cutting volume is to be substantially constant or to be gradually reduced,
It is possible to cope with cutting of any machining shape such as a three-dimensional curved surface as well as a two-dimensional curved surface.

[0011]

Here, the preliminary cutting data creation step includes, for example, (a) a predetermined number of cuttings when a finishing cut is performed at a constant cutting amount in accordance with finishing cutting data including cutting conditions and movement path data. A cutting volume calculation step of sequentially calculating a cutting volume for each, and (b) partially reducing the depth of cut so that the cutting volume becomes substantially constant, for example, substantially equal to a predetermined reference value or gradually decreases. A cutting amount correction step of correcting, and (c) based on the corrected cutting amount and the correction amount, the cutting volume at each predetermined number of cuts when the finish cutting is performed according to the finish cutting data becomes substantially constant. (D) a pre-cutting shape generation step for generating a three-dimensional pre-cutting shape that gradually decreases, and (d) preliminary cutting data including cutting conditions and movement path data for cutting a workpiece into a pre-cutting shape. Create And a data creation step. The program for creating the preliminary cutting data also includes, for example, a program for executing the above-mentioned cutting volume calculation step, cutting depth correction step, shape generation step before finish cutting, and data creation step.

The depth of cut can be determined, for example, by setting the allowance in the surface normal direction of the target product shape, or a three-axis automatic cutting machine that translates the rotary cutting tool three-dimensionally while holding it parallel to the Z axis. In the case of (1), the size of the margin in the Z-axis direction and the like are appropriately determined according to the target product shape, the automatic cutting device to be used, and the like.

The cutting volume is obtained from the shape of the rotation trajectory of the cutting edge of the rotary cutting tool, the tool position before and after cutting every predetermined number of cuts, the shape of the workpiece just before cutting, and the like.
The volume of the part that newly interfered when the rotary cutting tool and the workpiece to be machined are three-dimensionally reproduced by an M device or the like and moved relatively to the next tool position may be obtained. The workpiece to be processed before the finish cutting may be formed of a micro cube, and the number of micro cubes in a portion that interferes with the tool as the tool moves may be obtained as the cutting volume. The cutting volume for each predetermined number of cuts is, for example, the cutting volume for each blade or for each rotation of the tool,
Alternatively, although the cutting volume is a predetermined number of revolutions, the feed speed is constant and the rotation speed is constant in the finish cutting, so that the cutting volume can be set based on the moving distance of the tool or the cutting time. It is also possible to obtain the entire cutting volume for each predetermined number of cuts in all the steps of the finish cutting. For example, the cutting volume is obtained for each machining position separated by a fixed distance, or the cutting volume such as a part where the tool moving direction changes The calculation time can be shortened by calculating only the portion where the change is expected.

It is desirable that the shape before finish cutting be such that the cut volume in the finish cutting step is as constant as possible. However, if the shape is unavoidably changed due to overhang or the like, the cut volume of the overhang portion is required to prevent a step. Should be reduced. Also, when the cutting volume is gradually reduced in this way, without increasing it thereafter,
What is necessary is just to set the shape before finish cutting based on the cutting volume after the taper. In addition, as long as the required accuracy is satisfied, there is no problem even if there is a slight increase or decrease in the cut volume.

The finish cutting data and the preliminary cutting data include, for example, cutting conditions such as a tool rotation speed, a feed speed (relative moving speed with respect to a workpiece), a pick feed amount, and moving path data, and should be processed. It is set based on the product shape, the shape of the workpiece, the shape before finish cutting, the type and size of the rotary cutting tool to be used, the required processing accuracy, and the like. The same rotary cutting tool can be used for finish cutting and preliminary cutting.However, because the required processing accuracy is different, use different rotary cutting tools of different types and sizes or define different cutting conditions. Is also possible.

The preliminary cutting data creating step is configured to be executed by, for example, a cutting data creating apparatus having a computer, but may be configured to be executed by an automatic cutting apparatus such as an NC machine tool. it can. The cutting data creating device is configured to create, for example, finish cutting data and create preliminary cutting data using the finish cutting data. When the preliminary cutting data creation process is performed by the automatic cutting device, the finish cutting data can also be created by the same automatic cutting device, but it can be created in advance by another cutting data creation device. Is also good. Also,
The preliminary cutting data creation step and the preliminary cutting data creation program may all be performed automatically by a computer or the like, but include a step of requesting an input operation, a selection operation, etc. by an operator as necessary. Is also good.

The program recording medium for preparing the preliminary cutting data may be a ROM or other storage means provided in a cutting data creating device having a computer or an automatic cutting device, or may be detachably attached to such a device. A magnetic disk or magnetic tape that is mounted on
A portable storage means such as a CD-ROM may be used.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram illustrating an NC processing system that can suitably execute the method of the present invention.
Numeral 0 denotes an NC data generating device for generating NC data (cutting data) including moving path data and cutting conditions, 1
Reference numeral 1 denotes an NC data memory which is a recording medium such as a magnetic tape or a magnetic disk for storing the NC data, and 12 denotes an NC machine tool which performs a cutting process according to the NC data. The NC machine tool 12 is equivalent to an automatic cutting device, and includes an NC control unit 14 and an NC operation unit 16. The NC operation unit 16 includes, for example, a rotary cutting tool 18 such as a ball end mill as shown in FIG. , Its rotary cutting tool 1
8 is rotated around an axis parallel to the Z-axis, and the rotary cutting tool 18 is rotated by X-axis, Y-axis, Z-axis.
It has a feed drive means 22 for performing three-dimensional parallel translation in the axial direction, and rotates the rotary cutting tool 18 while rotating the rotary cutting tool 18 with respect to the workpiece 24 in accordance with predetermined movement path data including a direction intersecting with the axis. The workpiece 24 is cut into a predetermined product shape such as a free-form surface by relative movement. The main shaft rotation driving means 20 is an electric motor such as a servomotor, for example, and the feed driving means 22 is configured to include, for example, three sets of feed screws for moving in three axial directions and a servo motor for rotating the feed screws. You. Although the illustrated example shows a three-axis NC machine tool, the present invention can be applied to other NC machine tools such as a five-axis machine.

The NC data creation device 10 corresponds to a cutting data creation device, and includes a CPU 10a, a RAM, and the like.
10b and a microcomputer having a ROM 10c. The microcomputer 10 performs signal processing according to a program pre-stored in the ROM 10c while utilizing the temporary storage function of the RAM 10b, and reads necessary information from the database 26 while the flowchart of FIG. According to NC
Create data. The database 26 includes cutting condition information such as a tool rotation speed and a reference feed speed, and the workpiece 24.
Material shape information on the initial shape of the workpiece, machining shape information on the intended machining shape (product shape), the rotary cutting tool 18
The basic tool shape information including the rotation locus shape of the cutting edge of the tool is stored in advance. Steps S2 to S7 in FIG. 3 correspond to a preliminary cutting data creation step, and each of these steps S
RO storing a program for executing steps 2 to 7
M10c corresponds to the program recording medium for cutting data creation of claim 3. When creating the NC data, an input operation and a selection operation by the operator are performed via an input device (not shown) such as a keyboard as necessary.

Referring to FIG. 3, in step S1, the finishing cutting data including the rotation speed (spindle speed) of the rotary cutting tool 18, the feed speed, the amount of pick feed, and the movement path data are to be machined. The setting is made based on the product shape, the material of the workpiece 24, the type and size of the rotary cutting tool 18 to be used, the required processing accuracy, and the like. Here, a constant value is set for the tool rotation speed, the feed speed, and the pick feed amount at least while the workpiece 24 is being cut, and a constant tool rotation speed,
Finish cutting is performed at the feed speed and the pick feed amount. This step S1 corresponds to a finish cutting data creation step.

In step S2, the reference surface before finish cutting is obtained by offsetting the shape surface of the target product shape by the reference cutting amount A in the surface normal direction. The reference depth of cut A is the surface normal direction during the finish cutting (in the case of plane cutting, the Z-axis direction).
The cutting depth is determined based on the tool rotation speed and the feed speed at the time of finish cutting so that optimum cutting performance can be obtained when plane cutting is performed. The initial shape of the workpiece 24 is configured to have a surplus thickness at least larger than the reference cut amount A from the shape surface of the target product shape.

In step S3, the workpiece 24 up to the reference plane before finish cutting is formed of a small cube. The smaller the small cube, the higher the accuracy is obtained, but the amount of data increases with it. Therefore, it is desirable to set the size according to the size of the rotary cutting tool 18 and the amount of pick feed. % Value is set. As shown in FIG.
In the axial direction, the shape is divided into a grid by the length of one side of the micro-cube, and the intersection with the reference plane before finish cutting is determined by considering a straight line parallel to the Z-axis from the center point of the grid as shown in FIG. Then, a small cube including the intersection with the reference plane before finish cutting,
It is a small cube representing the upper limit of the workpiece 24 immediately before the finish cutting.

Subsequently, in step S4, as shown in FIG. 7, the workpiece 2 composed of a large number of minute cubes is formed.
Rotary cutting tool 1 on the upper surface (reference surface before finish cutting) 30
8 is cut by the reference cutting amount A, the rotary cutting tool 18 is moved by a predetermined reference moving amount f corresponding to a predetermined number of times of cutting in accordance with the moving path data, and a new rotation is performed. The number of micro cubes (micro cubes indicated by black dots in FIG. 7) that have interfered with the cutting tool 18 is determined by the cutting volume V _n.
Is calculated as May be a cutting volume V _n for each reference movement amount f in the finish cutting so as to obtain all, but in order to shorten the calculation time, successively cutting the volume V _n of positions spaced by a certain predetermined distance You may ask for it. Steps S2 to S4 correspond to a cutting volume calculation step. In addition, the rotary cutting tool 18 in FIG. 7 represents the shape of the rotation locus of the cutting edge, and the reference numeral 32 represents a processed surface (corresponding to a product shape) after finishing. In this case, the processing surface 32 is parallel to the XY plane, and the surface normal direction is parallel to the Z axis.

In the next step S5, the cutting volume V _n
Is corrected so that is substantially constant. This is performed, for example, as shown in FIG. 4. In step R1, a large number of cutting volumes V _n obtained in step S4 are obtained.
It is determined whether or not the processing for correcting the cutting amount based on the above has been completed, and if YES, the process from step S6 in FIG. 3 is executed. If the determination in step R1 is NO, step R2
In determining whether substantially equal or not with each cutting volume V _n is a predetermined reference value V ^*, in the case of V _n ≒ V ^* in the following areas after the determination in step R1 without correcting the depth of cut Volume determination is performed sequentially. If the determination in step R2 is NO, it is determined whether V _n> V ^* or in step R3, V _n> V ^* For the surface normal direction finish cutting before the reference surface of the position in step R4 downward, i.e., to reduce the depth of cut is offset so as to approach the product shape of interest, thereby reducing the cutting volume V _n. In the case of V _n <V ^*, increase the depth of cut is offset so as to separate the finish cutting before the reference surface of the position in step R5 upper direction of the surface normal direction, i.e. from the product shape for the purpose and increases the cutting volume V _n. The reference value V ^* is a cutting volume per reference movement amount f when a flat surface parallel to the XY plane is cut by the reference cutting amount A according to the finish cutting data, and the cutting edge of the rotary cutting tool 18 is used. rotation locus shape, pick feed amount, the reference movement amount f, based on the reference depth of cut a, obtained as with the cutting volume V _n as the number of small cube.

[0025] At Step R4, R5, and change the offset amount by a predetermined dimension to a predetermined, or it also be recalculated cutting volume V _n in the same manner as newly step S4, the cutting volume V _It is also possible to calculate the offset amount, that is, the correction amount of the cutting amount, using a predetermined arithmetic expression or the like such that _n matches the reference value V ^* .
Step S5 corresponds to a cutting amount correcting step.

[0026] In step S6, a finishing cutting before shape cutting volume V _n is substantially constant in the case of performing finish cutting in accordance with finishing milling data created in the step S1, depth of cut and cutting of the corrected It is generated in three dimensions based on the amount of correction of the amount. In the present embodiment, step R4
The corrected pre-cutting reference plane locally offset in the surface normal direction at R5 and R5 is used as the pre-cutting shape as it is. FIG. 8 is a diagram showing an example of the shape before finish cutting generated in this way, and the cutting amount a in the surface normal direction at the time of finish cutting changes according to the product shape. This step S6 corresponds to a pre-cutting shape generation step.
The portions indicated by dots (shaded) in FIG. 8 are the allowances for the preliminary cutting, and the blank portions are the allowances for the finish cutting.

In step S7, prior to the finish cutting, preliminary cutting data for cutting the workpiece 24 into the shape before the finish cutting is prepared. The preliminary cutting data includes cutting conditions such as the rotation speed (spindle rotation speed) of the rotary cutting tool 18, feed speed, pick feed amount, and movement path data, and the like. It is set based on the initial shape, the type and size of the rotary cutting tool 18 to be used, and the like. Since high machining accuracy is not always required in the preliminary cutting, it can be set as appropriate separately from the case of the finish cutting data. Step S7 corresponds to a data creation step.

In the next step S8, the finish cutting data and the preliminary cutting data created in steps S1 and S7 can be input to the NC machine tool 12 respectively.
The data is converted into the C data format and stored in the NC data memory 11.

Returning to FIG. 1, N of the NC machine tool 12
The C control unit 14 includes a microcomputer including a CPU, a RAM, a ROM, and the like.
According to the NC data stored in the C data memory 11, N
It controls the operation of the C operation unit 16 and is functionally provided with a feed speed control means 34 and a rotation speed control means 36. The feed speed control means 34 reads the actual tool position detected by the tool position detection means 38 so as to move the rotary cutting tool 18 in accordance with the movement path data at the feed rate set in the NC data while reading the feed drive means. 22 is controlled. Also, the rotation speed control means 36
Controls the operation of the main spindle rotation driving means 20 so that the rotary cutting tool 18 is driven to rotate around the axis at the tool rotation speed set in the NC data.

Then, first, according to the preliminary cutting data, the NC
When the machine tool 12 is operated, the workpiece 14 is preliminarily cut into a shape before finish cutting (preliminary cutting step), and thereafter, the NC machine tool 12 is operated according to the finish cutting data to be preliminarily cut. The workpiece 14 to be processed is finish-cut into a target product shape (finish cutting step).

[0031] Here, in the NC machining system of this embodiment, each predetermined cutting frequency of the rotary cutting tool 18 during the finishing cutting, the cutting volume V _n for each reference movement amount f is substantially constant in particular As described above, since the workpiece 24 is preliminarily cut prior to the final cutting, the cutting resistance in the final cutting step of performing the cutting at a constant rotation speed, a constant feed speed, and a constant pick feed amount becomes substantially constant, and the rotational cutting is performed. An excellent finished surface accuracy can be obtained without a step due to a change in the amount of elastic deformation of the tool 18 or the holding mechanism that holds the tool 18 or a cusp change due to a change in the feed amount per blade. Moreover, since the cutting volume V _n is controlled in such a substantially constant, a two-dimensional curved surface, such as of course three-dimensional curved surface may correspond to the cutting of any machining shape.

Further, in the present embodiment is adapted to the workpiece 24 expressed in small cube, obtaining the cutting volume V _n from the number of small cube of the interfering portions and the rotating cutting tool 18, for example 3-dimensional curved surface The calculation time can be greatly reduced as compared with the case where the cutting volume of the three-dimensional shape is calculated using an equation or the like.

[0033] Although in the above example was adapted to adjust the cutting volume V _n in depth of cut of the surface normal direction of the product shape, product shape as shown in FIG. 8 is changed in the Z-axis direction If
Z-axis direction of the depth of cut of the cutting volume V _n with, furthermore it is also possible to adjust the finishing cutting front shape.

Although the embodiments of the present invention have been described in detail with reference to the drawings, this is merely an embodiment of the present invention, and the present invention is not limited to various modifications and alterations based on the knowledge of those skilled in the art.
It can be implemented in an improved manner.

[Brief description of the drawings]

FIG. 1 is a functional block diagram illustrating an example of an NC processing system that can suitably implement the method of the present invention.

FIG. 2 is a diagram illustrating an example of an NC operation unit of the NC machine tool in FIG.

FIG. 3 is a flowchart illustrating the operation of the NC data creation device in FIG. 1;

FIG. 4 is a flowchart illustrating specific contents of step S5 in FIG. 3;

FIG. 5 is a view for explaining a plan view state of a micro cube created in step S3 of FIG. 3;

FIG. 6 is a diagram illustrating a process of generating a three-dimensional shape of a workpiece before finish cutting with the micro cube of FIG. 5;

7 is a diagram illustrating a specific example for calculating the cutting volume V _n in step S4 of FIG. 3.

8 is a diagram showing an example of a shape before finish cutting generated in step S6 of FIG. 3 together with a product shape.

[Explanation of symbols]

10: NC data creation device (cutting data creation device) 10c: ROM (program recording medium for cutting data creation) 12: NC machine tool (automatic cutting device) 18: rotary cutting tool 24: workpiece to be processed Step S2 S7: Preliminary cutting data creation process

Claims (3)

[Claims] 1. A workpiece is cut into a predetermined product shape by rotating a rotary cutting tool relative to a workpiece including a direction intersecting the axis while rotating the rotary cutting tool about the axis. A cutting method for processing, wherein the rotary cutting tool is relatively driven with respect to the workpiece at a constant feed speed while being rotationally driven at a constant rotation speed, and the workpiece is finished in the product shape. A finishing cutting step for cutting, and the work volume prior to the finishing cutting step, so that a cutting volume of the cutting edge of the rotary cutting tool at the time of the finishing cutting at each predetermined number of cuts becomes substantially constant or gradually decreases. A pre-cutting step of pre-cutting a member. 2. A rotary cutting tool is rotated around an axis by an automatic cutting apparatus and relatively moved with respect to a workpiece including a direction intersecting the axis.
A method of creating cutting data for performing a predetermined cutting process on the workpiece, comprising: a predetermined feed while rotating the rotary cutting tool at a constant rotation speed in accordance with predetermined finish cutting data. A predetermined number of cutting times of the cutting edge of the rotary cutting tool at the time of the finish cutting prior to finish-cutting the workpiece into a predetermined product shape by relatively moving the workpiece at a speed. A cutting data creating method, comprising a preliminary cutting data creating step of creating preliminary cutting data for performing preliminary cutting of the workpiece so that the cutting volume of each of the workpieces becomes substantially constant or gradually decreases. 3. A rotary cutting tool is rotated around an axis by an automatic cutting device, and is relatively moved with respect to a workpiece including a direction intersecting with the axis.
A recording medium for a cutting data creation program for creating cutting data for performing predetermined cutting on the workpiece by a computer, wherein the rotary cutting tool is used in accordance with predetermined finish cutting data. By performing relative movement with respect to the workpiece at a constant feed speed while rotating and driving at a constant rotation speed, prior to finish-cutting the workpiece into a predetermined product shape, A program for creating preliminary cutting data for pre-cutting the workpiece to be processed is recorded such that the cutting volume of the cutting edge of the rotary cutting tool for each predetermined number of cuts becomes substantially constant or gradually decreases. A program recording medium for creating cutting data, characterized in that: