JP2903524B2 - Free curved surface processing method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a free-form surface processing method, for example, a CAM (compu
This method is suitable for use when cutting a product having an outer shape having the free-form surface using data representing the free-form surface in ter aided manufacturing or the like.

B. Summary of the Invention The present invention provides a free-form surface machining method, in which after drilling using a drill in advance, and cutting the side wall of the machining hole using a ball end mill, the tool path can be shared and the surface can be shared. A free-form surface having irregularities can be easily obtained.

C Prior Art Conventionally, when machining into a complicated shape having a concave portion in a CAM or the like, first, a discharge electrode for electric discharge machining is created, and a mold is subjected to electric discharge machining.

That is, as shown in FIG. 10, the roughing and finishing electrodes 1 and 2 are formed in a convex shape with respect to the concave portion of the mold 3 based on the curved surface data of the concave portion.

D Problems to be Solved by the Invention By the way, in the case of using the electric discharge machining method, it is necessary to form the discharge electrodes 1 and 2 for rough machining and finish machining in addition to increasing the machining time. However, there is a problem that the work process becomes complicated and complicated as a whole.

One solution to this problem is NC (numerica
l control) If machining can be performed directly by using a complicated free-form surface data having a concave portion by a machine tool or the like, the machining time can be remarkably reduced.

However, in this case, it is necessary to generate tool path data for each tool to be used, and the machining method is complicated as a whole, so that it is still insufficient as a solution.

The present invention has been made in view of the above points, and it is an object of the present invention to propose a free curve machining method capable of directly cutting a desired curved surface shape in a short time by a simple method.

Means for Solving Problem E In order to solve such a problem, in the present invention, an offset surface SOF is generated based on data representing a free-form surface, and a tool path is generated based on the offset surface SOF. In the free-form surface processing method of processing the processing material 10 into a desired free-form surface, the tool shapes of the drill DR and the ball end mill BM are designated and processed so that the diameter of the ball end mill MB is larger than the diameter of the drill DR. Drilling is performed on the material 10 at predetermined intervals GP at each processing depth specified based on the offset curved surface SOF using the drill DR, and the tool path LE when drilling is performed by the drill DR. , And a predetermined interval GP is set so that adjacent holes D1, D2,... Formed by the drill DR are independent of each other with side walls. At the same time, by moving the ball end mill MD in the tip direction along the same tool path LE as the drill DR, the side wall is cut based on the difference in diameter between the ball end mill MD and the drill DR, and the adjacent holes D1, D2 ,... Should be continuous.

F action Drill DR and ball end mill MB for processing material 10
When the tip of the ball is milled to the same machining depth, the shape of the drill DR and ball end mill MB is specified so that the tool shape of the ball end mill MB contains the tool shape of the drill DR, and the cutting capability in the tip direction After drilling in advance to each predetermined machining depth corresponding to the free-form surface using a drill DR having a drill DR, using the tool path LE, the drill DR is formed by a ball end mill MB having a cutting ability in the side direction.
By cutting the side wall of the drilled hole (D1, D2, ...) by using the tool path LE, the rough machining shape DE can be cut in a shorter time.
F may be formed.

G Example Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a curved surface processing procedure SP1 executed by the free curved surface processing apparatus according to this embodiment as a whole, in which a die of a product having a predetermined outer shape of a free curved surface is cut.

That is, the free-form surface processing device enters the curved surface processing procedure SP1 in accordance with, for example, the operation of the operator, and
In P2, first, the first ball end mill MB for roughing
Wait for a radius RB of 1.

Here, the radius RB represents the distance from the center position of the ball end mill KB1 to the cutting edge.
Enter [mm], and then the free-form surface processing device
Move to SP3 and wait for the finishing D input.

Here, as shown in FIG. 2, the finishing margin D is a processing target of a die (finished die finished curved surface SC, and the curved surface SC is used when roughing is performed using a drill and a ball end mill. After obtaining a curved surface S (hereinafter referred to as a surface for rough machining) inside by a thickness D with respect to the curved surface representing the outer shape of the free-form surface, the final machining target SC is obtained by finishing.
This thickness is the finishing margin D.

Here, in step SP3, for example, when the value of the finishing margin D of 1 [mm] is input from the keyboard, the free-form surface processing apparatus proceeds to step SP4 to generate an offset surface.

That is, as shown in FIG. 3, the free-form surface machining apparatus translates the position data representing the surface of the free-form surface SC as the machining target by the parallel movement represented by (RB + D) · n in the normal direction. The position data representing the offset curved surface SOF composed of the set surfaces is generated.

That is, in this case, the radius of the ball end mill 10 (m
m], since 1 [mm] is input as the value of the finishing margin D, the offset amount represented by the value (RB + D)
Offset curved surface SO translated in the normal direction by 11 [mm]
Generate F.

Subsequently, the free-form surface machining apparatus proceeds to step SP5 and has an input of the uncut thickness T. In this die machining, as shown in FIG. 4, since the ball end mill MB does not have a cutting ability in the tip direction, machining holes (D1, D2...) Having a predetermined depth are formed in advance by a drill. After that, rough processing is performed by cutting using a ball end mill MB using the processing holes (D1, D2...).

That is, in the ball end mill MB, the tip has no cutting ability and has a cutting ability in the side direction, whereas the drill has a cutting ability in the tip direction of the tool and has no cutting ability in the side direction. Therefore, if a hole is drilled to a predetermined depth and then the remaining side wall portion is cut by a ball end mill MB having a large radius with respect to the drill, rough processing to a predetermined shape DEF can be performed.

In this embodiment, the drill is sequentially moved in the X and Y directions at a predetermined pitch, the hole is cut in the depth direction (ie, the Z direction) with the offset curved surface SOF as a cutting target, and then the ball end mill MB is moved to the drill end. The die is moved in the X and Y directions with the same pitch as that described above, is moved in the depth direction, and is driven to cut the die in advance before roughing.

At this time, as shown in FIGS. 5 and 6, the shape of the cutting edge of the ball end mill MB1 has the following formula x ² + (y−RB) ² = RB ^2. 1) can be represented by

On the other hand, the angle α _D of the cutting edge of the drill DR is generally 11
Since it is 8 mm, the straight line L representing the shape of the cutting edge of the drill DR
D is It is represented by

Therefore, from equations (1) and (2), the ball end mill
When the tip of the cutting edge of MB1 coincides with the tip of the cutting edge of the drill DR, the x coordinate of the point where the straight line LD and the curve LO representing the cutting edge shape of the ball mill end mill MB1 intersect is expressed by the following equation. It is represented by

Therefore, drill D against radius RB of ball end mill MB1
If the radius DR of R is selected to the value of the following formula RD = 0.8RB (4), and the position of the drill DR is set so that the tip DR of the drill DR and the tip of the ball end mill MB1 match. The drill DR can be driven using the same tool path data as that of the ball end mill MB1.

Thus, in this embodiment, as shown in FIG. 7, by inputting the uncut thickness T1 [mm] inputted in step SP5, the radius satisfying the expression (4) is satisfied so that the uncut thickness T remains. And then cut with a ball end mill MB1.

However, if the drill DR is drilled while leaving the uncut thickness T as described above, it is possible to prevent harmful stress from being applied in the direction perpendicular to the rotation axis of the drill DR and to break the drill DR. Can be avoided.

Subsequently, the free-form surface machining apparatus proceeds to step SP6 and calculates the machining pitch GP of the drill DR from the uncut thickness T as described above.

Thus, the machining pitch GP for the radius RD of the drill DR and the uncut thickness T is expressed by the following equation: GP = T + 2 × 0.8 RB (5), where the machining pitch GP is 17 [mm]. It can be seen that processing is required.

Here, as shown in FIG. 8, the radius RB of the ball end mill MB1 is determined by cutting the side surface of the hole (D1, D2...) Formed by the drill DR with the ball end mill MB1. The following formula is used so that the formed machining holes B1 and B2 are opened to each other with a predetermined opening portion OP. Is selected to satisfy the following.

Subsequently, the free-form surface machining apparatus moves to step SP7 and sequentially controls the movement of the drill in the x-direction and the y-direction by the machining pitch GP, and the tool path data at which the tip of the drill DR reaches a point on the curved surface S in the z-axis direction. To form

At this time, the free-form surface machining apparatus generates tool path data based on the principle of tool interference avoidance as shown in FIG.

In other words, the processing pitch GP using the ball end mill MB1
In the case where the offset curved surface SOF is generated for the finished curved surface SC when a plurality of intersections with the offset curved surface SOF occur on one straight line LC, the distance between the finished curved SC generates data toolpath LE to move the tool center BO to the minimum point H _3, thus One Kezurito the W portion upon cutting based on the tool path data.

The plurality of intersections of the sub connexion linear _{LC (H 1, H 2,} H 3), by the distance from the finished curved SC generates tool path data as the maximum depth of the point of maximum H _1, the tool interference Can be obtained, whereby cutting can be performed by using the ball end mill MB1 while avoiding tool interference.

That is, the free-form surface processing apparatus moves to step SP8,
Performs drilling of the drill DR based on the tool path data.

At this time, the tip of the drill DR is set to be shifted to the lower end by the radius RD of the ball end mill MB1.

Subsequently, when the process proceeds to step SP9 and the cutting is performed by the ball end mill MB1 along this tool path, the cutting holes B1 and B2 as shown in FIG. 8 can be formed.

When cutting holes (B1, B2 ...) are formed here,
As shown in FIG. 10, since the uncut portion HC remains, the rough machining can be completed by cutting and removing the uncut portion HC using a second ball end mill MB2 having a larger radius.

Accordingly, the free-form surface machining apparatus proceeds to step SP10, and determines the offset amount (RBS + D) based on the value 1 [mm] of the finishing margin D input in step SP3 and the radius RBS of the second ball end mill. .

In this case, the radius RBS of the second ball end mill MB2 is
It is necessary to select a value at which the unremoved portion HC can be removed by cutting.

Therefore, the radius RBS of the ball end mill MB2 is the center axis HCO of the uncut portion HC from the rotation center KO of the ball end mill MB2.
By setting the distance to RH and selecting a value represented by the following formula, RBS> RH (7), the uncut portion HC can be cut and deleted.

The distance RH from the center of rotation KO to the center axis HCO of the uncut portion HC is expressed by the following equation, where d is 1/2 of the machining pitch GP. It is represented by

Accordingly, since the processing pitch GP is determined as 17 [mm], RH = 12.02 [mm] is determined.

Therefore, in the case of this embodiment, the second ball end mill MB
The radius RBS of 2 is selected to be 12.5 [mm], so that the offset amount is 13.5 [mm].

Furthermore, the free-form surface processing equipment moves to the next step SP11,
A second offset surface SOF2 is generated.

That is, an offset curved surface that is a surface that is translated in the normal direction by a translation amount represented by (RBS + D) · n with respect to the position data representing the surface of the free-form surface SC to be processed.
Generate position data representing SOF2.

In this case, since 13.5 [mm] is input as the offset amount, the offset curved surface SOF2 translated in the normal direction by the offset amount is generated.

Next, the free-form surface processing device moves to step SP12,
Using the machining pitch GP (17 [mm]) obtained by the equation (5) and the rotation center axis KO of the first ball end mill MB1, the ninth is performed.
Based on the method for avoiding tool interference described above with respect to the drawing, the second
After the generation of the tool path data, the cutting by the second ball end mill MB2 is performed in step SP13.

Thus, the free-form surface machining device can be used for the uncut part HC (No. 10
After the figure is deleted, the process proceeds to step SP14 to complete the roughing.

According to the above method, the shape relationship between the drill DR and the first ball end mill MB1 for the first rough machining is specified in advance as described above with reference to FIG.
The first ball end mill MB after drilling in advance using
By cutting the side wall of the processing hole by using 1, the tool path for driving the drill DR and the first ball end mill MB1 can be shared, thereby shortening the processing time as a whole roughing Can be

In the above embodiment, the tip angle α _{D of the} drill is
Although the case of 118 ° has been described, the present invention is not limited to this, and even when a drill having another angle is used, the radius RB of the ball end mill is correspondingly described above with reference to FIGS. The same effect can be obtained by designating the method in advance.

Further, in the above-described embodiment, the case where a ball end mill having a hemispherical tip is used has been described.However, the present invention is not limited to this, and even when a cutting tool having another tip shape is used, Accordingly, a similar effect can be obtained by previously specifying the radius and the tip angle of the drill by the method described above with reference to FIGS. 5 and 6.

Further, in the above-described embodiment, the case where the relationship between the radius RD of the drill and the radius RB of the ball end mill is specified as in the expression (4) is described. However, the shape of the drill is not limited to this, and the outer diameter of the ball end mill is not limited to this. What is necessary is just to select so that it may not protrude from a shape.

Further, in the above-described embodiment, when machining using the first ball end mill MB1, the uncut portion HC (tenth
(FIG. 1), a case has been described in which the uncut portion HC is removed by using the second ball end mill. However, the present invention is not limited to this, and the first ball end mill MB
By selecting the radius RB of 1 to a value that allows the remaining portion HC to be removed and the portion HC to be removed, the cutting process using the second ball end mill MB2 may be omitted.

Further, in the above-described embodiment, the case where the present invention is applied when a mold is prepared has been described. However, the present invention is not limited to this, and can be widely applied to a case where a product is directly processed.

H Effect of the Invention As described above, according to the present invention, a tool path can be shared by performing pre-drilling using a drill and then cutting the side wall of the processed hole using a ball end mill. Accordingly, it is possible to realize a free-form surface processing method capable of shortening the processing time and easily obtaining a free-form surface having irregularities in the surface shape.

[Brief description of the drawings]

FIG. 1 is a flow chart showing one embodiment of the present invention, and FIG.
Fig. 3 is a cross-sectional view for explaining a processing shape, Fig. 3 is a schematic diagram for explaining an offset curved surface, Fig. 4 is a perspective view showing a processing step according to the present invention, and Figs. 5 and 6 are drills and balls. FIG. 7 and FIG. 8 are schematic diagrams showing the relationship between the processing interval and the radius of the drill and ball end mill, and FIG. 9 is a schematic cross-section showing the principle of avoiding tool interference. FIG. 10 is a schematic diagram showing the relationship between the uncut portion and the radius of the ball end mill, and FIG. 11 is a schematic side view showing a conventional example. 3, 10: Die, DR: Drill, MB1, MB2: Ball end mill, SC: Finished surface, LE: Tool path, GP
... processed pitch.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G05B 19/4093 B23Q 15/00

Claims (1)

(57) [Claims] 1. A free-form surface machining method for generating an offset surface based on data representing a free-form surface, generating a tool path based on the offset surface, and machining a work material into a desired free-form surface. The tool shape of the drill and the ball end mill is specified so that the diameter of the drill is larger than the diameter of the drill, and the processing depth specified based on the offset curved surface at predetermined intervals for the processing material. The hole is sequentially drilled using the drill, and the ball end mill is used for cutting using the tool path when the hole is drilled. The predetermined interval is determined by the drill. Each adjacent hole formed is independent with side walls from each other, and the ball end mill is moved along the same tool path as the drill. The side wall is cut based on the difference in diameter between the ball end mill and the drill by moving the ball end mill in the direction of the tip thereof, and the gap is such that the adjacent holes are continuous. Free-form surface processing method.