JP2013132733A - Device and method for calculating machined surface property, and device and method for determining machining condition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for calculating machined surface properties in which the machined surface properties can be simulated.SOLUTION: A device includes: a tool center displacement amount calculation section 42 for calculating a displacement amount of a rotational center C of a rotating tool 5 based on the cutting resistance of the rotating tool 5 when the cutting resistance of the rotating tool 5 is changed by intermittent cutting; a relative cutting edge position calculation section 14 for calculating the relative cutting edge positions of blades 5a and 5b relative to the rotational center C of the rotating tool 5; an absolute cutting edge position calculating section 15 for calculating the absolute cutting edge positions of the blades 5a and 5b relative to a workpiece W based on the displacement amount of the rotational center C of the rotating tool 5 and the relative cutting edge positions; post-machining shape calculation section 24 for calculating the post-machining shape of the workpiece W by transferring the absolute cutting edge positions to the workpiece W; and a machined surface property calculation section 62 for calculating the machined surface properties ΔY2 in the post-machining shape based on the post-machining shape of the workpiece W calculated.

Description

  The present invention relates to a machined surface property calculating apparatus and a machined surface property calculating method for calculating a machined surface property in intermittent cutting with a rotary tool on a workpiece. Furthermore, the present invention relates to a machining condition determination device and a machining condition determination method to which the calculation device or calculation method is applied.

  In Japanese Patent Laid-Open No. 9-47941, when cutting is performed using a ball end mill, the feed rate is controlled in consideration of the amount of displacement of the tool according to the rigidity of the tool system due to an increase in the processing load. Is described.

Japanese Patent Laid-Open No. 9-47941

By the way, if the machined surface properties (surface state of the machined shape) can be simulated, machining conditions that can improve the machined surface properties can be found.
The present invention has been made in view of such circumstances, and a machining surface property calculation device and a machining surface property calculation method capable of simulating the machining surface property, and a machining condition using the machining surface property calculation device. An object of the present invention is to provide a determination device and a processing condition determination method.

(Processed surface property calculation device)
(Claim 1) A machined surface property calculation apparatus according to the present invention uses a rotary tool having one or more blade portions in the circumferential direction on the outer peripheral side, and rotates the rotary tool around an axis with respect to a workpiece. In the intermittent cutting performed by moving relative to each other, in the machined surface property calculation device for calculating the processed surface property, when the cutting resistance generated in the rotary tool fluctuates with intermittent cutting, Tool center displacement amount calculating means for calculating the displacement amount of the rotation center of the rotary tool based on the cutting resistance of the rotary tool, and relative blade edge position calculation for calculating the relative blade edge position of the blade portion with respect to the rotation center of the rotary tool. Means, an absolute blade edge position calculating means for calculating an absolute blade edge position of the blade portion with respect to the workpiece based on a displacement amount of the rotation center of the rotary tool and the relative blade edge position; and Addition Based on the calculated post-processing shape of the workpiece, a processing surface property in the post-processing shape is calculated based on the post-processing shape calculation means for calculating the post-processing shape of the workpiece by transferring it to the workpiece. Machined surface property calculating means.

(Claim 2) Further, the processed surface property calculated by the processed surface property calculating means may be a surface roughness in the post-processed shape.
(Claim 3) Further, the machining surface property calculated by the machining surface property calculation means calculates a deepest position in a cutting direction in the post-machining shape in a predetermined rotation of the rotary tool, and a plurality of the deepest positions It may be the difference between the maximum value and the minimum value.

(Processing condition determination device)
(Claim 4) The machining condition determination device according to the present invention includes the above-described machining surface property calculation device that calculates the machining surface property, and a machining condition determination unit that determines the machining condition based on the calculated machining surface property. With.
(Claim 5) Further, the machining control device calculates a minimum uncut amount of the workpiece based on a difference between a processed shape of the workpiece and a target shape of the workpiece. An amount calculation unit may be provided, and the processing condition determination unit may determine the processing condition based on the processed surface property and the minimum uncut amount.

(Claim 6) Further, the machining condition determining means may determine the rotational speed of the rotary tool based on the machined surface properties and the minimum uncut remaining amount.
(Claim 7) Further, the machining condition determining means determines the rotational speed of the rotary tool based on the machined surface properties, and sets the command position of the rotary tool based on the minimum remaining amount of cutting. You may make it offset to.

(Processed surface properties calculation method)
(Claim 8) The machining surface property calculation method according to the present invention uses a rotary tool having one or more blade portions in the circumferential direction on the outer peripheral side, and rotates the rotary tool about the axis while rotating the rotary tool about the workpiece. In the intermittent cutting performed by moving relative to each other, in the machining surface property calculation method for calculating the machining surface properties, when the cutting resistance generated in the rotary tool fluctuates with intermittent cutting, A tool center displacement amount calculating step for calculating a displacement amount of the rotation center of the rotary tool based on a cutting resistance of the rotary tool, and a relative blade edge position calculation for calculating a relative blade edge position of the blade portion with respect to the rotation center of the rotary tool. An absolute blade edge position calculating step of calculating an absolute blade edge position of the blade portion with respect to the workpiece based on a displacement amount of the rotation center of the rotary tool and the relative blade edge position; and Addition Based on the post-processing shape calculation step of calculating the post-processing shape of the workpiece by transferring it to the workpiece, and calculating the processed surface properties in the post-processing shape based on the calculated post-processing shape of the workpiece. A machined surface property calculating step.

(Processing condition determination method)
(Claim 9) The machining condition determination method according to the present invention includes the above-described machining surface property calculation method for calculating the machining surface property and the machining condition based on the machining surface property calculated by the machining surface property calculation method. And a processing condition determining step for determining.

  (Claim 1) In intermittent cutting with a rotary tool, while the rotary tool is rotating once, depending on the phase of the blade part of the rotary tool, the moment of cutting and the idling that is not cut. There are moments. For this reason, the displacement amount of the rotation center of the rotary tool does not always become the processed surface property. The rotation center of the rotary tool means the rotation center of each cross section in the axial direction of the rotary tool when the rotary tool is not deformed. Further, the cutting resistance may fluctuate even while the rotary tool is rotating once and cutting.

  Here, according to the present invention, the absolute cutting edge position relative to the workpiece is calculated by considering the relative cutting edge position in addition to the amount of displacement of the rotation center of the rotary tool. That is, the movement of the absolute cutting edge position can be grasped with high accuracy while the rotary tool is rotated once. And since the post-processing shape of the workpiece is calculated by transferring the absolute cutting edge position to the workpiece, the post-processing shape can be calculated with high accuracy. The processed surface properties of the post-processing shape are calculated from the post-processing shape thus calculated. Therefore, the machined surface properties can be obtained with high accuracy by simulation.

(Claim 2) The processed surface properties are the surface roughness, that is, the difference between the deepest position in the cutting direction and the position of the outermost surface. That is, the surface roughness can be calculated by simulation.
(Claim 3) The processed surface property is a difference between the maximum value and the minimum value among the plurality of deepest positions. The difference can be easily calculated. The difference sufficiently represents the surface state of the shape after processing.

  (Claim 4) According to the machining condition determining apparatus of the present invention, since the machining condition is determined using the machined surface properties calculated by simulation, high machining accuracy can be obtained. Here, the machining condition determination device can be applied as an NC data creation device, and can also be applied as a device that performs correction processing in actual machining. Here, the machining conditions are, for example, at least one of the rotational speed of the rotary tool, the cutting allowance in the cutting direction, the relative feed speed of the rotary tool, and the trajectory (machining path) of the command position.

  (Claim 5) The minimum uncut amount can be calculated by calculating the difference between the post-process shape calculated by the post-process shape calculation means and the target shape. Then, by determining the machining conditions based on the calculated minimum remaining amount of machining and the machined surface properties, the machined surface properties can be made highly accurate while reducing the minimum remaining amount of machining. That is, processing accuracy can be improved.

  (Claim 6) Here, it has been found that the machined surface properties and the minimum uncut remaining amount change according to the rotational speed of the rotary tool. Therefore, by determining the rotation speed based on the calculated machined surface properties and the minimum remaining amount of machining, the machined surface properties can be made highly accurate while reducing the minimum remaining amount of machining.

  (Claim 7) Even if the current machining condition is a machining condition in which the minimum remaining amount of machining is large, the minimum remaining amount of machining can be reduced by offsetting the command position itself. On the other hand, the machined surface properties cannot be highly accurate even if the command position is offset. Therefore, the machined surface property is applied to determining the rotation speed of the rotary tool. In this way, the calculated machined surface properties are applied to the determination of the rotation speed, and the calculated minimum remaining amount is applied to the command position offset, thereby reducing the minimum remaining amount of machining and improving the machined surface properties with high accuracy. Can be.

(Claim 8) According to the machined surface property calculation method according to the present invention, the machined surface property can be calculated with high accuracy in the same manner as the machined surface property calculation device described above.
(Claim 9) In the machining condition determination method according to the present invention, the machined surface properties can be made highly accurate as in the above-described machining condition determination apparatus.

It is a figure which shows the structure of the machine tool of the application object of the processing system in this embodiment. It is a figure for demonstrating the generation | occurrence | production mechanism of a process error, Comprising: The state in which the rotary tool is deform | transforming is shown. It is a figure for demonstrating the generation | occurrence | production mechanism of a process error, Comprising: The cutting resistance which arises in a rotary tool is shown. It is a figure for demonstrating the generation | occurrence | production mechanism of a process error, Comprising: The behavior with respect to the elapsed time of the cutting resistance which arises in a rotary tool, and the displacement amount of the rotation center of a rotary tool is shown. It is a figure for demonstrating the generation | occurrence | production mechanism of a process error, Comprising: The positional relationship of the rotary tool and a workpiece in each time of FIG. It is a figure for demonstrating the generation | occurrence | production mechanism of a process error, Comprising: The relationship between the displacement amount of the rotation center of a rotary tool, and a process error is shown. (A) shows the relative cutting edge position of the blade part with respect to the rotation phase of the rotary tool. (B) shows the amount of displacement of the rotation center with respect to the rotation phase of the rotary tool. (C) shows the absolute cutting edge position of the blade portion with respect to the rotational phase of the rotary tool. It is a detailed functional block diagram of the processing system of this embodiment. It is a figure which shows the actual cutting amount h and the cutting length b. (A) is a figure regarding the 1st after-process shape calculated in the after-process shape calculation part of FIG. (B) is a figure regarding the 2nd post-process shape calculated in the post-process shape calculation part of FIG. It is explanatory drawing regarding the vibration phase of a rotary tool. It is a figure which shows the locus | trajectory of a rotation center when the rotation center of a rotary tool changes to a cutting direction. It is a figure which shows the shape after a process in the case of FIG. 11, and shows the positional relationship with a target position. This post-processing shape corresponds to the second post-processing shape calculated in FIG. In the case of FIG. 11, it is a figure which shows the 1st post-processing shape, and shows the positional relationship with a target position. The relationship between the rotational speed of the rotating spindle and the minimum uncut amount is shown. The relationship between the rotational speed of a rotating spindle and the maximum amplitude of a rotating tool is shown. The relationship between the rotational speed of a rotation main axis and a surface property value is shown.

(1. Outline of processing system)
An outline of the processing system will be described. The machining system aims to reduce the minimum remaining amount of machining and to make the machined surface properties highly accurate when cutting the workpiece W with a rotary tool. That is, it aims at reducing a processing error.

(2. Configuration of the target machine tool)
A configuration of a machine tool to which the machining system is applied will be described. The target machine tool is a machine tool that cuts the workpiece W with a rotary tool. A horizontal machining center as an example of the machine tool will be described with reference to FIG. As shown in FIG. 1, the machine tool is movable in the Y-axis direction on the bed 1, the column 2 that can move on the bed 1 in the X-axis direction, and the front surface of the column 2 (left surface in FIG. 1). A saddle 3, a rotary spindle 4 that is rotatably supported by the saddle 3 and holds a rotary tool 5, and a table 6 that is movable on the bed 1 in the Z-axis direction and on which a workpiece W is placed. .

  Here, the rotary tool 5 includes one or more blade portions 5a and 5b in the circumferential direction on the outer peripheral side. The rotary tool 5 includes, for example, a ball end mill, a square end mill, and a milling cutter. That is, the machine tool performs intermittent cutting by moving relative to the workpiece W while rotating the rotary tool 5 about the axis. Although not shown, the machine tool includes a motor for moving the column 2, the saddle 3 and the table 6, a coolant nozzle for supplying coolant, a coolant pump, and the like.

(3. Mechanism of machining error)
Next, a mechanism for generating a machining error will be described with reference to FIGS. The processing error is an error between the actual processed shape of the workpiece W and the target shape (design value) of the workpiece W.

  As shown in FIG. 2, the deformation of the rotary tool 5 causes the rotation center coordinates of the respective cross sections in the Z-axis direction of the rotary tool 5 to deviate from the command coordinates. The Z-axis direction is the rotation axis direction of the rotation main shaft 4. In particular, when a rotary tool 5 (elongated rotary tool) having a large L / D (= length / diameter) is used, the rigidity of the rotary tool 5 is low, so that the distal end side of the rotary tool 5 is bent by the cutting resistance Fy. Easy to deform. Here, one or more blade portions 5a and 5b are provided on the outer peripheral surface of the tip of the rotary tool 5 in the circumferential direction. That is, the post-machining shape of the workpiece W changes due to the displacement of the rotation center C on the tip side of the rotary tool 5 (parts of the blade portions 5a and 5b) by the cutting force Fy. As a result, a processing error occurs. Here, the rotation center C is the rotation center of each cross section in the axial direction of the rotary tool 5 (the rotation axis direction of the rotary spindle 4) when the rotary tool 5 is not deformed, that is, each Z in the rotary tool 5. It means the center of rotation of the axial section. However, in order to make the explanation easy to understand, the rotation center C will be described below as one rotation center in a certain Z-axis coordinate.

  Here, if the cutting resistance Fy generated in the rotary tool 5 is constant, the amount of deflection on the tip side of the rotary tool 5 is constant. However, in the intermittent cutting with the rotary tool 5, the cutting resistance Fy generated in the rotary tool 5 changes sequentially. Therefore, the amount of displacement of the rotation center C on the tip side of the rotary tool 5 changes sequentially mainly in the Y direction. At this time, the displacement amount of the rotation center C on the tip side of the rotary tool 5 and the cutting resistance Fy depend on the dynamic characteristics of the rotary tool 5. The dynamic characteristics of the tool indicate the deformation behavior with respect to the input force, and the transfer function (compliance and phase lag) or the mass (M) calculated therefrom, the viscous damping coefficient (C), the spring constant (K). ), Resonance frequency (ω), damping ratio (ζ), and the like. In FIG. 2, the reciprocating arrow is a display that means that the rotation center C on the tip side of the rotary tool 5 reciprocates mainly in the Y direction.

  In FIG. 2, the processing error due to the cutting resistance Fy in the Y direction has been described. However, in practice, as shown in FIG. 3, the rotary tool 5 may have a cutting resistance Fx in the counter feed direction and a cutting resistance Fz in the axial direction in addition to the cutting resistance Fy in the counter cutting direction. That is, the rotation center C on the tip side of the rotary tool 5 is displaced in the direction of the combined resistance Fxyz (not shown) of the cutting resistances Fx, Fy, and Fz in each direction. Although FIG. 3 shows a square end mill, the same applies to a ball end mill as shown in FIG.

  Next, when intermittently cutting the workpiece W while rotating and feeding the rotary tool 5, the cutting resistance Fy generated in the rotary tool 5 and the displacement amount Ya of the rotation center C on the tip side of the rotary tool 5. Will be described with reference to FIGS. 4 and 5. FIG. Here, the cutting resistance Fy in the counter-cutting direction (Y direction) and the displacement amount Ya of the rotation center C on the tip side will be described. This is because the anti-cutting direction (Y direction) has the greatest influence on the machining error.

  With reference to FIG. 4 and FIGS. 5A to 5E, the behavior of the cutting resistance Fy with respect to the elapsed time t will be described. As shown in FIG. 4, the cutting resistance Fy changes from zero to a large value at time t1, and then changes to zero again at time t2. FIGS. 5A and 5B correspond to times t1 and t2 in FIG. 4, respectively. As shown in FIG. 5A, time t1 is the moment when one of the blades 5a starts to contact the workpiece W. That is, time t1 is the moment when cutting is started by one of the blade portions 5a. On the other hand, as shown in FIG. 5B, the time t2 is the moment when the cutting of the workpiece W by the one blade portion 5a is finished. Thus, one blade part 5a is cutting between t1 and t2.

  Thereafter, as shown in FIG. 4, the cutting resistance Fy is zero between t2 and t4. During this time, as shown in FIG. 5C corresponding to time t3, both the blade portions 5a and 5b are not in contact with the workpiece W. That is, the rotary tool 5 is idling.

  Thereafter, as shown in FIG. 4, the cutting resistance Fy changes to a large value again at time t4 and changes to zero again at time t5. At time t4 in FIG. 4, the other blade portion 5b starts to contact the workpiece W as shown in the corresponding FIG. 5 (d). That is, cutting is started by the other blade portion 5b. Further, at time t5 in FIG. 4, as shown in the corresponding FIG. 5 (e), the cutting with the other blade portion 5b is finished. Thus, the other blade part 5b is cutting between t4 and t5.

  Here, it can be seen from the current cutting region in FIG. 5 that the actual cutting amount (instant cutting amount) differs at the instants t1 to t2 and t4 to t5. That is, the actual cutting amount increases at a stroke from the start of cutting and gradually decreases after reaching the peak. In more detail, it changes before and after the boundary between the part not cut last time and the part cut last time. Then, as shown in the sharply increasing portion of the cutting resistance Fy in FIG. 4, the cutting resistance Fy during the cutting process has a substantially triangular shape and changes according to the actual cutting depth. I understand that.

  In addition, when the rotary tool 5 starts cutting at times t1 and t4, in other words, it collides with the workpiece W at times t1 and t4. That is, at the moment when the rotary tool 5 starts cutting from the idle state, an intermittent cutting resistance is generated in the rotary tool 5 due to a collision with the workpiece W.

  That is, the rotation center C on the distal end side of the rotary tool 5 generates an acceleration in at least the anti-cutting direction (Y direction) due to fluctuations in the cutting resistance Fy during cutting. Furthermore, due to the intermittent cutting, the rotational center C on the tip side of the rotary tool 5 is at least in the anti-cutting direction (Y) due to the cutting resistance Fy (force such as impact force) during cutting. Direction).

  Therefore, the displacement amount Ya of the rotation center C on the distal end side of the rotary tool 5 vibrates according to the eigenvalue of the rotary tool 5 as shown in FIG. In particular, immediately after the occurrence of the cutting resistance Fy that fluctuates during the cutting process, the displacement amount Ya of the rotation center C becomes the largest and then decays. Then, again, the displacement amount Ya increases due to the cutting resistance Fy, and repeats.

  Next, how the displacement amount Ya of the rotation center C on the tip side of the rotary tool 5 affects the machining error will be described with reference to FIGS. 6 (a) to 6 (c). In each of the rotational phases φ of the rotary tool 5, the relative position (relative blade edge position) of the blade edge of the blade portion 5a with respect to the rotation center C on the distal end side of the rotary tool 5 is as shown in FIG. That is, the rotational phase φ at which the blade portion 5a cuts the workpiece W is in a phase range of about 30 ° to 90 °.

  Three types of displacement Ya of the rotation center C on the front end side are shown. However, these are all shown schematically, and the vertical axis of FIG. 6B is not the same scale as the vertical axis of FIG. The first (No. 1) displacement amount Ya has a behavior corresponding to the depth of cut as shown in FIG. The second (No. 2) displacement amount Ya is a vibration behavior as shown in FIG. The third (No. 3) displacement amount Ya is assumed to be constant.

  In this way, in the case of the first (No. 1) to third (No. 3) displacement amount Ya, the cutting edge position (absolute cutting edge position) of the blade portion 5a with respect to the workpiece W is shown in FIG. As shown in c). That is, the behavior shown in FIG. 6A is added to the behavior shown in FIG. 6B. Here, in FIG. 6C, the range of the hatched rotational phase φ is cut by the blade portion 5a. Further, in actual machining, the rotational speed of the rotary tool 5 is very large relative to the feed speed of the rotary tool 5. Therefore, most of the cutting surface in this cutting process is scraped off by the next cutting process. Then, the portion that appears in the shape after the final machining in the cutting surface in the current machining is near 90 ° in the hatched rotational phase φ of FIG. That is, at least the deepest position of the hatched rotational phase φ appears in the final post-processing shape.

  In view of this, in the case of the first (No. 1) displacement amount Ya in FIG. 6C, the tool rotation phase φ is at the deepest position in the vicinity of 90 °, and coincides with the target value. Therefore, in the case of the first (No. 1) displacement amount Ya, the machining error is substantially zero. In the case of the second (No. 2) displacement amount Ya, the tool rotation phase φ is at the deepest position slightly before 90 ° and is below the target value. Therefore, in the case of the second (No. 2) displacement amount Ya, a machining error that causes excessive machining occurs. However, depending on the second (No. 2) displacement amount Ya, there may be a machining error that remains uncut or the machining error may be zero. In the case of the third (No. 3) displacement amount Ya, the tool rotation phase φ is at the deepest position in the vicinity of 90 ° and exceeds the target value. Therefore, in the case of the third (No. 3) displacement amount Ya, a machining error that is always left uncut occurs.

  Thus, the deepest position of the absolute blade edge position of the blade portion 5a and its vicinity form a post-processing shape. That is, not only the displacement amount Ya of the rotation center C on the distal end side of the rotary tool 5 but also the position of the cutting edge position of the blade portion 5a with respect to the rotation center C affects the machining error. I understand.

(4. Functional configuration of machining system)
Next, details of the functional configuration of the machining system will be described with reference to FIGS. The machining system is configured as shown in the functional block diagram of FIG. The functional configuration of the processing system shown in FIG. 7 will be described below.

  The machine information storage unit 10 stores various types of information related to the application target machine tool. The various information includes, for example, control parameters such as the machine configuration of the machine tool, the corner portion deceleration parameter, the rotation speed upper limit value of the rotation spindle 4, and the upper limit value of the movement speed of each feed axis. The command value calculation unit 11 is based on the NC data already created and the machine information stored in the machine information storage unit 10, and the center position command value C 0 of the rotary tool 5 and the phase command value of the rotary spindle 4. Is calculated. The center position command value C0 of the rotary tool 5 is expressed in the machine coordinate system.

  The tool center coordinate calculation unit 12 includes the center position command value C0 of the rotary tool 5 calculated by the command value calculation unit 11 and the rotation center C on the tip side of the rotary tool 5 calculated by the tool center displacement amount calculation unit 42. Based on the amount of displacement, the coordinates of the rotation center C on the tip side of the rotary tool 5 are calculated. That is, if the displacement amount of the rotation center C on the tip side changes by continuing the simulation, the change is sequentially reflected to calculate the coordinates of the rotation center C on the tip side. The cutting edge shape storage unit 13 stores the cutting edge shape of one or a plurality of rotary tools 5. In the case of the ball end mill shown in FIG. 2, for example, the shape of the blade portions 5a and 5b shown in the drawing is stored in the blade shape storage unit 13.

  The relative blade edge position calculation unit 14 calculates the relative blade edge positions of the blade parts 5 a and 5 b with respect to the rotation center C on the distal end side of the rotary tool 5. Here, the relative cutting edge position calculation unit 14 calculates the relative cutting edge position based on the phase command value of the rotation spindle 4 calculated by the command value calculation unit 11 and the cutting edge shape stored in the cutting edge shape storage unit 13. calculate. That is, the relative cutting edge position calculation unit 14 calculates the relative cutting edge positions of the blade parts 5 a and 5 b for each of the rotation phases φ of the rotary tool 5. The relative cutting edge position is, for example, information as shown in FIG.

  The absolute cutting edge position calculation unit 15 calculates the absolute cutting edge positions of the blade parts 5 a and 5 b with respect to the workpiece W based on the coordinates of the rotation center C on the tip side of the rotary tool 5 and the relative cutting edge position. The absolute cutting edge position calculation unit 15 can calculate an absolute cutting edge position that changes according to the elapsed time t during one rotation of the rotary tool 5. The absolute cutting edge position is information as shown in FIG. 6C, for example. Further, when the relative blade edge positions of the blade portions 5a and 5b change by continuing the simulation, the absolute blade edge position calculation unit 15 calculates the absolute blade edge position by sequentially reflecting the change.

  The material shape calculation unit 21 calculates the material shape of the workpiece W based on the input shape data. The machining shape storage unit 22 stores the material shape of the workpiece W calculated by the material shape calculation unit 21 and the history of the machining shape of the workpiece W calculated by the post-machining shape calculation unit 24. . That is, the stored information includes not only the shape after the final machining but also the shape of the workpiece W that sequentially changes during the machining.

  The actual cutting amount calculation unit 23 calculates the actual cutting amount h by the blade portions 5a and 5b by simulation at each moment of machining. The actual cutting amount h will be described with reference to FIG. FIG. 8A shows a state in which the rotational phase φ of the rotary tool 5 is about 45 °. At this moment, the radial length of the rotary tool 5 in the portion where the blade portion 5a is in contact with the workpiece W becomes the actual cutting amount h. When the rotary tool 5 rotates clockwise from the state shown in FIG. 8A, the actual cutting amount h gradually decreases. When the absolute cutting edge positions of the blade portions 5a and 5b change by continuing the simulation, the actual cutting amount calculation unit 23 sequentially reflects the change and calculates the actual cutting amount h. In other words, the actual cutting amount calculation unit 23 performs the actual cutting based on the absolute cutting edge position calculated by the absolute cutting edge position calculation unit 15 and the shape of the workpiece W at that time stored in the machining shape storage unit 22. The cutting depth h is calculated. In FIG. 8A, Rd is a cutting allowance in the cutting direction (−Y direction).

  The post-machining shape calculation unit 24 calculates the post-machining shape of the workpiece W by transferring the absolute cutting edge position that sequentially moves to the workpiece W. Then, the processed shape of the workpiece W calculated by the processed shape calculation unit 24 is stored in the processed shape storage unit 22. When the absolute cutting edge position changes by continuing the calculation, the post-machining shape calculation unit 24 sequentially reflects the change and calculates a new post-machining shape. Here, as the post-processing shape calculated by the post-processing shape calculation unit 24, any of the following two types can be adopted. These will be described with reference to FIGS. 9 (a) and 9 (b).

  As the first post-machining shape, as shown in FIG. 9A, the post-machining shape calculation unit 24 includes the cutting direction of the absolute cutting edge position during each rotation of the blade parts 5a and 5b of the rotary tool 5. The deepest position P (n) in the (−Y direction) is extracted, and the deepest position P (n) is calculated as the post-machining shape of the workpiece W. Then repeat this. In this case, the processed shape of the workpiece W is point data as the past deepest positions P (1) to P (n-1) and the current deepest position P (n). Here, since the distance between the adjacent deepest positions P (n-1) and P (n) is very small, even if the deepest position P (n) has a post-machining shape, it must be processed with sufficiently high accuracy. The shape can be recognized.

  As the second post-processing shape, the post-processing shape calculation unit 24 calculates the post-processing shape of the workpiece W by transferring the locus of the absolute cutting edge position of the blade portions 5a and 5b to the workpiece W. Then repeat this. In this case, not only the deepest position P (n) shown in FIG. 9A but also the positions before and after the deepest position P (n) are stored as post-processing shapes. When the portion Qb (n-1) stored as the past shape history is cut off by cutting this time, the shape information Q (( Update to n). In this way, the latest post-processing shape is sequentially formed. The latest post-processed shape is composed of a part Qa (n-1) that has not been cut out of the past shape information Q (n-1) and a part Q (n) formed this time. The second processed shape formed in this way is stored as finer point data or continuous lines than the first processed shape described above. Therefore, the second post-processing shape can grasp the surface roughness and the like.

  The cutting resistance calculation unit 32 calculates the cutting resistance by using the actual cutting amount h calculated by the actual cutting amount calculation unit 23 and the cutting length b acquired from the processing conditions. The cutting resistance can also be detected using a sensor.

  The tool dynamic characteristic storage unit 41 stores a dynamic characteristic coefficient of the rotary tool 5. The dynamic characteristic coefficient includes a mass coefficient M, a viscous resistance coefficient C, and a spring constant K. These dynamic characteristic coefficients M, C, and K can be acquired by performing a hammering test on the rotary tool 5 in advance, performing a simulation, or actually measuring with a sensor installed in the machine. .

  The tool center displacement amount calculation unit 42 calculates the rotation center C based on the cutting force calculated by the cutting force calculation unit 32 and the dynamic characteristic coefficients M, C, and K stored in the tool dynamic characteristic storage unit 41. The displacement amount is calculated. The basic formula used to calculate the displacement amount of the rotation center C is formula (1). Then, the tool center displacement amount calculation unit 42 feeds back the calculated displacement amount of the rotation center C to the tool center coordinate calculation unit 12. Therefore, when the cutting force changes by continuing the simulation, the tool center displacement amount calculation unit 42 calculates the displacement amount of the rotation center C by sequentially reflecting the change. Here, the tool center displacement amount calculation unit 42 calculates the amplitude of vibration of the rotary tool 5 based on the displacement amount of the rotation center C.

  Here, the amount of displacement of the rotation center C changes as the cutting resistance generated in the rotary tool 5 fluctuates. Further, the amount of displacement of the rotation center C varies depending on the vibration phase θ of the rotary tool 5 when receiving the cutting resistance Fy during cutting by the rotary tool 5. More specifically, as shown in FIG. 10, when the rotary tool 5 receives the first cutting resistance and the vibration phase is defined as 0 °, the rotary tool 5 receives the second cutting resistance. Depending on the vibration phase θ of the rotary tool 5, the amount of displacement of the rotation center C changes. Therefore, the relationship between the vibration phase θ of the rotary tool 5 when receiving the cutting resistance Fy and the displacement amount (Ya) of the rotation center C in the anti-cutting direction (Y direction) will be described with reference to FIG. In the following description, the vibration phase θ of the rotary tool 5 when the rotary tool 5 receives the second cutting resistance is simply referred to as “vibration phase θ”.

  As shown in FIG. 10, the rotary tool 5 is in a state of vibrating in the anti-cutting direction (in the Y direction) while being fed and moved in the X direction. Then, the vibration phase θ = 0 ° to 360 ° of the vibration is defined as shown in FIG. That is, the vibration phases θ = 0 ° and 360 ° are vibration phases in which the rotary tool 5 moves in the anti-cutting direction and the moving speed in the anti-cutting direction is maximized. The vibration phase θ = 90 ° is the vibration phase at the moment when the rotary tool 5 is switched from the anti-cutting direction to the cutting direction. The vibration phase θ = 180 ° is a vibration phase in which the rotary tool 5 moves in the cutting direction and the moving speed in the cutting direction is maximized. The vibration phase θ = 270 ° is the vibration phase at the moment when the rotary tool 5 is switched from the cutting direction to the anti-cutting direction.

  Returning to FIG. 7, the functional configuration of the machining system will be described. The machining error calculation unit 60 calculates a machining error ΔY based on the post-machining shape of the workpiece W calculated by the post-machining shape calculation unit 24 and the target shape of the workpiece W. Here, the machining error ΔY can be represented by the minimum uncut amount ΔY1 and the surface property value ΔY2.

  This will be described with reference to FIGS. 11 and 12. When the rotation center C of the rotary tool 5 is sent in the direction of the arrow in FIG. 11, it is assumed that the rotation center C moves along a locus like a one-dot chain line in FIG. 11. Then, the cutting edge draws a trochoid for the number of cutting edges, but if the single blade feed amount is sufficiently small with respect to the tool diameter, the rotary tool 5 draws a locus as shown by each circle in FIG. 11 at each moment. It can be said. And the shape after a process of the to-be-processed object W becomes a shape of the part except the area | region of the circle | round | yen of each rotary tool 5 of FIG. Here, the target shape is a position indicated by Ptarget.

  That is, the processed shape of the workpiece W is as shown in FIG. Here, in the processed shape Q of the workpiece W, the difference between the target shape (target value) Ptarget and the deepest position of the processed shape Q is the minimum remaining amount ΔY1, and the deepest position and the outermost surface of the processed shape Q The surface roughness that is the difference from the side position is the surface property value ΔY2. As described above, the machining error ΔY is represented by the total value of the minimum uncut amount ΔY1 and the surface property value ΔY2.

  Therefore, the machining error calculation unit 60 includes a remaining machining amount calculation unit 61 that calculates a minimum remaining amount of machining ΔY1, and a machining surface property calculation unit 62 that calculates a surface property value ΔY2. Here, the post-processing shape Q shown in FIG. 12 corresponds to the second post-processing shape shown in FIG. At this time, in the case shown in FIG. 12, the surface property value ΔY <b> 2 is obtained by transferring the trajectory of the absolute cutting edge position of the blade portions 5 a and 5 b of the rotary tool 5 to the workpiece W to transfer the second value of the workpiece W. When the shape after processing (shown in FIG. 9B) is used, the surface roughness is Rz (JIS B0633: 2001). Thus, according to the above method, the surface roughness Rz can be calculated.

  In addition, when the first post-machining shape as shown in FIG. 9A is used, as shown in FIG. 13, the uncut remaining amount calculation unit 61 determines the maximum value Pmax of the deepest position P and the target shape Ptarget. The machined surface property calculation unit 62 calculates the difference between the maximum value Pmax at the deepest position P and the minimum value Pmin at the deepest position P as the surface property value ΔY2. This surface property value ΔY2 is an approximate value of the surface roughness Rz and sufficiently represents the surface state of the post-processing shape. And calculation of an approximate value can perform an arithmetic process easily.

  The machining condition determination processing unit 70 calculates a machining error ΔY of the rotary tool 5 based on the vibration state of the rotary tool 5 and the vibration phase θ of the rotary tool 5 when the rotary tool 5 receives the second cutting resistance Fy. The processing conditions are determined so as to make it smaller. The machining conditions can be determined by the machining condition determination processing unit 70 to change the NC data itself, or the machining conditions can be corrected during machining.

  With reference to FIGS. 14-16, the process condition determination process by the process condition determination process part 70 is demonstrated. FIG. 14 shows the relationship between the rotational speed S of the rotary spindle 4 and the uncut amount ΔY1, FIG. 15 shows the relation between the rotational speed S of the rotary spindle 4 and the maximum amplitude Amax of the rotary tool 5, and FIG. The relationship between the rotational speed S of the rotary spindle 4 and the surface property value ΔY2 will be described. 14 to 16, the vibration phase θ is also shown.

  As shown in FIG. 16, the surface property value ΔY2 is smallest in the vicinity of the vibration phase θ = 0 to 90 ° and 180 °. Then, the minimum uncut amount ΔY1 in the vibration phase θ within the range is small in the vicinity of the vibration phase θ = 180 ° as shown in FIG. In the case of this vibration phase θ, as shown in FIG. 15, the maximum amplitude Amax of the rotary tool 5 is also small. Therefore, the machining condition determination processing unit 70 determines the rotation speed S among the machining conditions so that the vibration phase θ is in the vicinity of 180 °. By doing so, the processing error ΔY can be reduced.

  A determination method different from the determination method will be described. As shown in FIG. 16, in the vicinity of the vibration phase θ = 180 °, the range in which the surface property value ΔY2 is small is very small. In particular, in the case of the elongated rotary tool 5, this is likely to occur. Therefore, even if the vibration phase θ is slightly shifted, the surface property value ΔY2 is increased. Therefore, consider a vibration phase θ = 0 to 90 ° in which the surface property value ΔY2 is small. However, at the vibration phase θ = 0 to 90 °, as shown in FIG. 14, the minimum remaining amount ΔY1 is large. Therefore, the machining condition determination processing unit 70 determines the rotation speed S in the range of the vibration phase θ = 0 to 90 °. Thereby, surface property value (DELTA) Y2 can be made small (a process surface property can be made highly accurate). Then, the machining condition determination processing unit 70 offsets the command position of the rotary tool 5 in the cutting direction as the minimum uncut amount ΔY1. As a result, the minimum uncut amount ΔY1 can be reduced.

  The machine control unit 82 controls each drive unit 83 based on the NC data. In particular, the machine control unit 82 controls the rotation speed of the rotary spindle 4 based on the rotation speed S of the NC data determined by the machining condition determination processing unit 70, and when the command position is offset, the command position To control the relative position of the rotary tool 5 and the workpiece W.

  When the machining condition is determined by the machining condition determination processing unit 70 during machining, the correction unit 81 corrects the correction according to the machining condition. Further, in addition to the above, the correction unit 81 can also correct the command value so as to change the cutting allowance Rd or the feed speed in the cutting direction. For example, the amount of displacement of the rotation center C of the rotary tool 5 is reduced by reducing the cutting allowance Rd in the cutting direction or reducing the feed rate. As a result, processing errors can be reduced.

  According to the processing system described above, the following effects can be obtained. In intermittent cutting with the rotary tool 5, while the rotary tool 5 is rotating once, depending on the phase of the blade parts 5 a and 5 b of the rotary tool 5, the moment of cutting and the idling that is not cut. And there are moments. Therefore, the displacement amount of the rotation center C of the rotary tool 5 is not always the minimum uncut amount ΔY1 or the surface property value ΔY2. Further, the cutting resistance may fluctuate while the rotary tool 5 is rotating once and during cutting.

  Therefore, in addition to the displacement amount of the rotation center C of the rotary tool 5, the absolute cutting edge positions of the cutting edges 5 a and 5 b with respect to the workpiece W are calculated by considering the relative cutting edge positions of the cutting edges 5 a and 5 b. That is, the movement of the absolute cutting edge position can be grasped with high accuracy while the rotary tool 5 is rotated once. And since the post-processing shape of the workpiece W is calculated by transferring the absolute cutting edge position to the workpiece W, the post-processing shape can be calculated with high accuracy. Based on the post-processing shape thus calculated, the uncut amount ΔY1 and the surface property value ΔY2 of the post-processing shape are calculated. Therefore, the uncut amount ΔY1 and the surface property value ΔY2 can be obtained with high accuracy by simulation.

  Furthermore, since the machining conditions are determined by the two determination processes described above using the uncut amount ΔY1 and the surface property value ΔY2 calculated by the simulation, high machining accuracy can be obtained. That is, the minimum uncut amount ΔY1 and the surface property value ΔY2 can be reduced.

5: Rotating tool, 5a, 5b: Cutting edge, 14: Relative cutting edge position calculation section, 15: Absolute cutting edge position calculation section, 24: Post-machining shape calculation section, 42: Tool center displacement calculation section, 61: Uncut amount Calculation unit 62: Machining surface property calculation unit 70: Machining condition determination processing unit C: Center of rotation Ptarget: Target shape Pmax: Maximum value of deepest position Pmin: Minimum value of deepest position S: Rotational speed W: Workpiece, ΔY1: Minimum uncut amount, ΔY2: Surface property value (machined surface property)

Claims (9)

In intermittent cutting performed by using a rotary tool having one or more blades in the circumferential direction on the outer peripheral side and moving the rotary tool relative to the workpiece while rotating about the axis, the machining surface A machined surface property calculating device for calculating properties,
A tool center displacement amount calculating means for calculating a displacement amount of the rotation center of the rotary tool based on a cutting resistance of the rotary tool when a cutting resistance generated in the rotary tool fluctuates with intermittent cutting;
A relative blade edge position calculating means for calculating a relative blade edge position of the blade portion with respect to the rotation center of the rotary tool;
Absolute edge position calculation means for calculating an absolute edge position of the blade portion with respect to the workpiece based on the displacement amount of the rotation center of the rotary tool and the relative edge position;
A post-processing shape calculation means for calculating a post-processing shape of the workpiece by transferring the absolute cutting edge position to the workpiece;
Based on the calculated post-processing shape of the workpiece, a processing surface property calculation means for calculating a processing surface property in the post-processing shape;
A machined surface texture calculation device comprising: In claim 1,
The machined surface property calculating device, wherein the machined surface property calculated by the machined surface property calculating unit is surface roughness in the post-machined shape. In claim 1,
The machined surface property calculated by the machined surface property calculating means calculates the deepest position in the cutting direction in the post-machined shape in a predetermined rotation of the rotary tool, and the maximum value and the minimum value among the plurality of deepest positions. Machined surface property calculation device that is a difference in values. The machined surface property calculating device according to any one of claims 1 to 3, which calculates the machined surface property,
Machining condition determining means for determining a machining condition based on the calculated machined surface properties;
A processing condition determination apparatus comprising: In claim 4,
The processing control device includes a remaining amount calculation unit that calculates a minimum remaining amount of the workpiece based on a difference between a processed shape of the workpiece and a target shape of the workpiece,
The processing condition determining device is a processing condition determining device that determines the processing condition based on the processed surface property and the minimum uncut remaining amount. In claim 5,
The machining condition determining unit is a machining condition determining device that determines a rotation speed of the rotary tool based on the machined surface properties and the minimum uncut amount. In claim 5,
The machining condition determining means determines the rotational speed of the rotary tool based on the machined surface properties, and offsets the command position of the rotary tool in the cutting direction based on the minimum uncut amount. . In intermittent cutting performed by using a rotary tool having one or more blades in the circumferential direction on the outer peripheral side and moving the rotary tool relative to the workpiece while rotating about the axis, the machining surface A machined surface property calculation method for calculating properties,
A tool center displacement amount calculating step of calculating a displacement amount of the rotation center of the rotary tool based on the cutting resistance of the rotary tool when the cutting resistance generated in the rotary tool fluctuates with intermittent cutting;
A relative blade edge position calculating step of calculating a relative blade edge position of the blade portion with respect to the rotation center of the rotary tool;
An absolute cutting edge position calculating step of calculating an absolute cutting edge position of the cutting edge with respect to the workpiece based on a displacement amount of the rotation center of the rotating tool and the relative cutting edge position;
A post-processing shape calculation step of calculating a post-processing shape of the workpiece by transferring the absolute cutting edge position to the workpiece;
Based on the calculated post-processing shape of the workpiece, a processing surface property calculation step for calculating a processing surface property in the post-processing shape;
A machined surface texture calculation method comprising: The machined surface property calculation method according to claim 8, wherein the machined surface property is calculated.
A machining condition determining step for determining a machining condition based on the machined surface texture calculated by the machined surface texture calculation method;
A processing condition determination method comprising:

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