JPS639926B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a face milling cutter that has a main cutting edge formed on the outer periphery of the distal end of the body of the milling cutter and is used for face milling and the like. [Prior Art] Originally, cutting with a milling cutter is different from general turning and the like, and is all interrupted cutting. That is, in milling, a cutting process is repeated in which each cutting blade cuts into the workpiece material with an impact, and then finishes cutting with an even more impact. Therefore, the durability of a milling cutter, that is, the life of the tool, is more influenced by chipping or fatigue damage of the cutting edge due to repeated impacts than damage caused by normal cutting edge wear. Therefore, in order to extend the life of the milling cutter, it is important to improve the initial cutting style between the cutting edge and the workpiece surface during cutting to alleviate the contact impact. Therefore, first, the cutting situation using a conventional face milling cutter will be discussed. Fig. 1 shows a blade type face milling cutter, which is an example of a conventional face milling cutter, in which reference numeral 1 indicates the body of the milling cutter, 2 the mounting hole thereof, 3 a keyway for mounting, 4 is the shank part of the blade, ) is the rake face of the head cutting edge of the blade,
Reference numeral 6 indicates an end face, ie, a front flank, of the cutting edge, and 7 indicates a side face, ie, a side flank, of the cutting edge. Here, symbols and terms will be defined for various angles of the cutting edge, which are necessary elements for studying the above-mentioned contact mode. The symbol R in Figure 1 is the radial rake angle. This radial rake angle R is the angle that the rake face 5 makes with respect to the radius r connecting the rotational axis O of the milling cutter and the cutting edge T, and as shown in the figure, the rake face 5 is tilted forward in the rotational direction 9 of the milling cutter. A positive angle is when the angle is, and a negative angle is the opposite. Also, 1st-
The symbol A in the figure indicates the axial rake angle. This axial rake angle A is the angle formed by the rake face 5 with respect to the axis O. As shown in the figure, when the rake face 5 is tilted backward with respect to the rotation direction 9 of the milling cutter, it is a positive angle. The opposite is a negative angle. Further, the symbol CH indicates a corner angle (JIS-B0170 cutting tool terminology, approach angle of No. 305). This corner angle CH is the degree that the main cutting edge is oblique, and is the angle that the main cutting edge makes with the axis O of the milling cutter, and the cutting edge is located closer to the outer circumference of the body 1 of the milling cutter than the cutting edge. The case is positive. FIG. 2 is a diagram showing the relative position of the milling cutter and the upper surface of the workpiece perpendicular to the rotational axis O of the milling cutter during milling, as seen from the direction of the axis O of the milling cutter. In the figure, reference numeral 8 indicates the outer peripheral outline circle of the milling cutter, 9 indicates the direction of rotation, 10 indicates the workpiece, 11 indicates the upper surface thereof, 12 indicates the upper edge of the side surface, and 13 indicates the feed direction of the workpiece. This is an arrow indicating.
Further, the symbol P is the intersection point of the milling cutter's outer circumferential contour circle and the side surface of the workpiece, and is the initial contact point at the time of milling cutting. Furthermore, as one element for determining the contact style, the angle ε between the (O-P) line and the side surface of the workpiece is the engagement angle (JIS-B0172 milling term,
It forms a complementary angle to the engagement angle E of #1006. That is, E
+ε=90°). Next, FIG. 3 is a perspective view showing the cutting state of the face milling cutter, and shows a cross section of one cutting by one main cutting edge of the blade type face milling cutter. In the figure, reference numeral 4 indicates the shank portion of one blade attached to the milling cutter, and 9 indicates the rotating direction of the milling cutter, that is, the direction of movement of the blade during cutting. Further, reference numeral 10 is the work material, 11 is the upper surface thereof, 14 is the side surface thereof, 12 is the upper edge of the side surface and is the intersection line of the upper surface 11 and the side surface 14, and 13 is the feed of the work material during cutting. It is an arrow indicating the direction. The above-mentioned cut cross section has a substantially parallelogram shape, which is represented by a quadrilateral STUV in the figure. The length of the side ST or UV in the vertical direction is determined by the depth of cut per cut, and the length of the side TU or VS in the horizontal direction is determined by the amount of feed per tooth. When one cutting edge of a face milling cutter starts cutting the STUV cross section, the issue to be considered regarding the contact pattern here is at what point the milling cutting edge and the side surface of the workpiece first come into contact and begin cutting. be. FIG. 4 schematically shows four possible contact modes during actual cutting. In the figure, the points indicated by black circles are the parts where the main cutting edge and the workpiece first come into contact, and both are shown as point contacts. These are S contact, T contact, and U contact, respectively.
We will call this contact, V-contact. In reality, in addition to these four point contact states, ST where two points are in contact at the same time,
There are also line contacts such as TU, UV, and VS, and surface contacts where four points such as STUV come into contact at the same time, but both occur under extremely limited specific conditions and can be considered as special cases of the four point contacts mentioned above. We will omit that consideration and consider the basic case of point contact. The reference numeral 16 shown in the lower left of FIG. 4 is the S contact,
First, the tip of the cutting blade cuts into the side surface of the workpiece, making point-to-surface contact. This is disadvantageous because the impact applied to the tip of the cutting blade is extremely large. On the other hand, the reference numeral 17 shown in the upper right of Fig. 4 is a U contact, which is also a point-to-plane contact, but in this case, contrary to the previous example, the point of the workpiece first hits the rake face of the cutting edge. Therefore, the impact on the tip of the cutting edge is gentle, which is the desired contact style. Also, the code 1 in the upper left of Figure 4
5 and the reference numeral 18 on the lower right are T contact and V contact, respectively, but in both cases, the main cutting edge and the edge of the workpiece cross each other, so it can be said that it is a type of point contact. In either case, the impact on the cutting edge is relatively gentle, and these are also desirable contact modes. In the end, among the four possible contact modes mentioned above, only S contact, which cuts into the workpiece from the cutting edge tip, is superior to the other three contact modes in terms of sharpness, but the impact on the tip of the cutting edge is superior to the other three contact modes. is large and undesirable as a contact mode. By the way, regarding the conditions under which each of the above contact modes occurs, there is a relational expression shown in the table below, which was elucidated by Mr. Kronenberg of West Germany.

[Table] According to Mr. Cronenberg's conditional expression above, the S contact in question occurs when (R>ε), that is, the engagement angle ε is smaller than the radial rake angle R, and (CH<i), that is, the characteristic This is the case only if the corner named i is greater than the corner angle CH. here,
Regardless of the magnitude of R and ε, if the relationship CH>i holds, S contact will not occur. Therefore, first looking at the above equation regarding the characteristic angle i, when the axial rake angle A is a negative value, i
also takes a negative value, so in the general case where the corner angle CH is a positive value, the relationship (CH<i) does not hold, and therefore no S contact occurs. Furthermore, even if the axial rake angle A is positive, if its value is small, the denominator in the above equation becomes approximately 0, and as a result, the value of i also becomes small, so (CH<
This means that the relationship i) does not hold. [Problems to be solved by the invention] However, as the value of the axial rake angle A increases, the value of i also increases, so (CH<
When the relationship i) comes to hold, it becomes impossible to avoid S contact. Therefore, as mentioned above, S contact can be avoided by making the axial rake angle A negative or small, but if the axial rake angle A is negative or small, the cutting resistance increases and the cutting quality deteriorates. becomes worse. Due to the above relationship, particularly with this type of milling cutter, there has been a problem in that it is difficult to avoid S contact and maintain sharpness at the same time. [Object of the Invention] The present invention was made to solve the above-mentioned problems, and it is possible to avoid or alleviate the S contact and at the same time maintain machinability, that is, sharpness, and furthermore, it is possible to maintain cutting performance, that is, sharpness, which is unique to face milling. It is an object of the present invention to provide a face milling cutter that has cutting performance suitable for various applications and can further improve sharpness. [Means for Solving the Problems] The face milling cutter of the present invention is a face milling cutter in which a main cutting edge having a positive corner angle is formed on the outer periphery of the tip of the body of the milling cutter. The center axis is perpendicular to the main cutting edge and approximately parallel to the reference plane of the main cutting edge, the cutting edge inclination angle of the main cutting edge is approximately 0° at the cutting edge, and it is oriented from the cutting edge to the cutting edge. It is formed by a cylindrical surface that gradually becomes larger. [Example] Figures 5 to 5 show a blade-type face milling cutter that is an embodiment of the present invention, and the same components as those shown in Figures 1 to 1 are shown. are given the same reference numerals and their explanations will be omitted. In Figure 5 to Figure 5, reference numeral 1 in the figure
9 is the shaft of the blade attached to the outer periphery of the tip of the body 1 of the milling cutter; 20 is the brazed cemented carbide where the cutting edge is formed; 21
is a reference plane that is a plane perpendicular to the main movement direction of the main cutting edge 22 (JIS-B0170 cutting tool terminology, No. 204 reference plane)
It is. Further, reference numeral F denotes a rake face along the main cutting edge 22, and this rake face F is formed to be the outer circumferential surface of the cylinder 23. Here, the cylinder 23 has its central axis O1 substantially parallel to the reference plane 21 and the main cutting edge 2
The cylinder is oriented in the Q direction perpendicular to 2 or in a direction similar to the Q direction. Thereby, the main cutting edge 22 is formed so as to draw a circular arc shape when viewed in the Q direction. Furthermore, the rake face F is the cutting edge inclination angle (JIS-B0170 cutting tool terminology, cutting edge inclination of No. 307) formed by the tangent 24 and the reference surface 21 near the cutting edge S when viewed in the Q direction The angle) t is approximately 0°, and the cutting edge inclination angle t1 between the tangent 24' and the reference surface 21 becomes large near the edge T. This main cutting edge 22 has a positive corner angle CH
Since it is attached with a
As shown in the figure, the curvature is large near the cutting edge S, and gradually decreases toward the cutting edge T, forming a quadratic curve similar to the oblique cross section of a cylinder. According to the face milling cutter having the above configuration, as the main cutting edge 22 goes from the cutting edge S to the cutting edge T, the main cutting edge 22 progressively tilts backward with respect to the rotating direction 9 of the milling cutter, in other words, the axis O of the milling cutter. Since the axial rake angle A is progressively retracted from the point S and forms a small angle of approximately 0° near the cutting edge S, it is possible to avoid S contact and prevent the cutting edge S from breaking. Since the positive angle increases progressively, sharpness can be maintained, and the above two performances, which have been difficult to achieve in the past, can be achieved at the same time. Furthermore, to explain in general terms the radial rake angle R, which is another requirement that determines machinability, that is, the quality of sharpness, based on FIG. 6 and FIG. 6, the conditions for forming a positive radial rake angle are depends on how far the rake face 5 retreats from the radius r1 parallel to the rake face 5 in the rotational direction 9 of the milling cutter. In this way, when the rake face 5 retreats, the rake face 5 is aligned with the axis O of the milling cutter and the main cutting edge S.
radial rake angle R with respect to the radius r connecting T
is a right angle. The value is determined by the radius r of the milling cutter and the amount of retraction b of the rake face 5 b/r=
It is sinR. As the amount of retreat of the rake face 5 increases to b1 as shown in FIG. 6, the radial rake angle R1 becomes a positive angle. However, in the face milling cutter according to the present invention, as shown in FIG. Moreover, as shown in Figure 5, this rake face F is progressively retreating from the axis O of the milling cutter from the cutting edge S to the cutting edge T, so the radial rake angle R is small near the cutting edge S and It increases progressively towards T. As described above, in the face milling cutter according to the present invention, both the axial rake angle A and the radial rake angle R are small at the cutting edge S, and the angle is small at the cutting edge T.
The angle increases progressively toward . However, in the face milling cutter mentioned above, since the main cutting edge 22 has a positive corner angle CH, the rake angle is the rake angle in the Q direction perpendicular to the main cutting edge 22, that is, the true rake angle (JIS-B0170
Cutting tool terminology, vertical rake angle of No. 310) shall be discussed. As is well known, the relational expression for calculating the true rake angle Tr is tanTr=tanR・cosCH+tanA・sinCH
It is. If we apply the axial rake angle A and radial rake angle R of the face milling cutter according to the present invention to this formula, we can see that there is a major feature here. That is, as mentioned above, both the axial rake angle A and the radial rake angle R are small at the cutting edge S and increase progressively and continuously toward the cutting edge T, so according to the above equation, both of them are weighted. The true rake angle is small at the S part of the cutting edge and increases progressively towards the T part of the cutting edge, but the rate of this increase becomes even more weighty. On the other hand, in the conventional example of a face milling cutter with a straight main cutting edge, when a positive axial rake angle A is attached, the rake face 5 is The radial rake angle R also increases as it moves backward from the cutting edge S section to the cutting edge T section from the axis O in the rotational direction 9 of the milling cutter, but the manner in which it increases is proportional, and the axial rake There is no change in angle A. As a result, the true rake angle increases proportionally from the cutting edge S to the cutting edge T. In other words, the effect is small because the increase rate of the true rake angle is only related to the radial rake angle R on one side in the second term on the right side of the above equation, and as in the configuration according to the present invention, the radial rake angle R is also the same as the axial rake. Since both angles A do not change at the same time, the manner in which they increase is neither progressive nor weighted. In general, in a face milling cutter whose cutting edge has a positive corner angle CH, the diameter d of the cutting edge S portion is smaller than the diameter D of the cutting edge T, as shown in FIG. Therefore, the rotational circumference of the main cutting edge gradually increases from the cutting edge S to the cutting edge T, and the difference is proportional to 3.14 times the difference in diameter. Therefore, the amount of cutting also increases from the cutting edge S to the cutting edge T in accordance with the above ratio. Therefore, in this type of face milling cutter, it is desirable that the cutting performance is better as the cutting edge approaches the cutting edge T compared to the cutting edge S. In this regard, in the face milling cutter according to the present invention, the true rake angle is small at the S portion of the cutting edge and increases continuously in a progressive and weighted manner as it moves toward the T edge of the cutting edge. Even if the above-mentioned S contact is avoided or alleviated in the S section and its sharpness slightly decreases, the cutting performance improves in a progressive manner toward the cutting edge T and adapts well to the gradual increase in the amount of cutting. As a result, cutting is performed extremely smoothly. This performance is particularly noticeable in heavy cutting with deep cuts and high feeds, and when heavy cutting is performed with the face milling cutter described above, clean chips 25 that are concave and spirally wound as shown in Figure 7 are produced.
It was found that, while the chips 25 are generated and discharged regularly, in the case of the conventional straight main cutting edge, cracks 26 are formed in the chips 25 and discharged as shown in FIG. The cutting effect is also clearly symbolized by the shape of the chips 25. In addition, in the description of the above embodiment, a blade type face milling cutter was described, but the present invention is not limited to this, and can be applied to various types of face milling cutters such as a brazing type, a clamp type, and a throw-away type. can. In addition, it can be similarly applied to an angular cutter with a corner angle CH, similar to a face milling cutter. [Effects of the Invention] As explained above, according to the face milling cutter of the present invention, on the one hand, the S contact between the main cutting edge and the workpiece material that impairs the tool life can be avoided or alleviated, and on the other hand, the cutting performance, that is, the sharpness can be improved. This makes it possible to resolve the two-way contradiction that was previously thought to be unavoidable, and in addition to this, it also actively demonstrates excellent cutting performance that matches the cutting mode of a face mill. can do.

[Brief explanation of the drawing]

Figure 1 is a partially cutaway vertical sectional view showing a conventional blade type face milling cutter;
Figure 1 is a side view of the blade in Figure 1, Figure 1 is a bottom view of Figure 1, Figure 2 is a top view for explaining the cutting mode of a conventional face milling cutter, and Figure 3 is a cutting style of a conventional face milling cutter. FIG. 4 is an explanatory view showing the contact mode between the workpiece and the main cutting edge in a face milling cutter, and FIG. 5 is a front view of the cutting edge portion showing an embodiment of the face milling cutter of the present invention. Fig. 5 is a view from the Q direction of Fig. 5, Fig. 5 is a side view of Fig. 5, Fig. 6 is an explanatory diagram of the radial rake angle, Fig. 7 and 7th-
The figure is a perspective view showing the shape of chips. 1...Body, 21...Reference surface of cutting blade, S...
...Blade tip, T...Blade end, F...Rake face, CH...
Corner angle, O... Axis of milling cutter, O1... Center line of cylinder, 9... Rotation direction, 22... Main cutting edge,
23... Cylindrical surface, t, t1... Cutting edge inclination angle, A...
...Axial rake angle, R, R1...Radial rake angle, r, r1...Radius of milling cutter, 25...
Chips.

Claims (1)

[Claims] 1. In a face milling cutter in which a main cutting edge 22 having a positive corner angle CH is formed on the outer periphery of the tip of the body 1 of the milling cutter, the rake face F along the main cutting edge 22 is formed by a cylindrical surface. , the central axis 01 of the cylindrical surface is perpendicular to the main cutting edge 22 and approximately parallel to the reference plane 21 of the main cutting edge 22, and the cutting edge inclination angle t of the main cutting edge 22 is parallel to the main cutting edge 22. It is a cylindrical surface that forms approximately 0° at the cutting edge S of the main cutting edge 22 and gradually becomes larger from the cutting edge S to the cutting edge T of the main cutting edge 22.
is a quadratic curve whose curvature gradually decreases from the cutting edge S to the cutting edge T side when viewed from the side perpendicular to the axis O, and its axial rake angle A
and the radial rake angle R both increase progressively from the cutting edge S to the cutting edge T,
A face milling cutter characterized in that a true rake angle formed by the rake face F in a direction orthogonal to the main cutting edge 22 increases progressively and weighted from the cutting edge S to the cutting edge T.