JPS63221913A - End mill - Google Patents

Abstract

PURPOSE:To smoothly grind a side surface and prevent the deterioration of precision of the undulation on the finished surface by installing a cutter having a torsional outer periphery which always contacts with a a certain number of simultaneously working cutting edges and setting the depth of a cutter groove part to 0.15 or less of the outer diameter. CONSTITUTION:When the cutting-in quantity in the axial direction is (a), cutting-in quantity in the radial direction is (b), diameter of an end mill is D, number of cutting edges is N, number of simultaneously working cutting edges is Ns, center angle of ground surface 2 is phi, torsional angle of cutter is beta, pitch in the axial direction of cutter is l, and the lead is L, Ns=N.l/L, L=pi.D.cotbeta, l=a+D/2.cotbeta.cos<-1>(1-2b/D), phi=cos<-1>(1-2b/D). For example, when a=30mm, b=0.05mm, D=10mm, and Ns=1, beta becomes 27.6 deg. and phi becomes 8.11 deg.. When the first cutter I1 passes through a point P1, the second cutter I2 passes through a point P2, and the grinding without the group surface 2 smooth ly changes from the grinding by the first cutter I1 to the grinding by the second cutter I2. The depth of a cutter groove is set to 0.15 or less of the diameter D, and the center thickness is increased, and rigidity is improved.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an end mill for precision finishing of side cutting.

[Prior art and its problems]

Generally, when performing side cutting with an end mill, the first
The cutting process will proceed as shown in the figure.1. Ru. In this case, since the outer peripheral cutting edge l of the end mill is twisted in the axial direction, cutting starts from the tip of one cutting edge in the axial direction, and as it rotates, it moves upward (to the shank side). f) The part of the cutting edge involved in cutting moves with a force of The number of peripheral cutting edges involved is more than one, so that when a certain cutting edge h (cutting is still being performed at a certain position on the raised surface), the next peripheral cutting edge In this way, at the same time, the number of peripheral cutting edges involved in cutting becomes several, two, or two become three, so the cutting resistance acting on the end mill increases. fluctuating, 4th
As shown in Figure 1-1, there may be undulations or collapse on the finished surface.
<Occurrence. Therefore, if we consider side surface cutting using a straight-edged end mill as shown in Figure 5, one cutting edge cuts the side surface equivalent to the total depth of cut in the axial direction at one time with zero time lag. do. Therefore, theoretically, the above-mentioned "undulation"
etc. will not occur. However, in reality, because intermittent cutting is performed, the finished surface may be "peeled".
Otherwise, depping occurs due to impact cutting resistance acting on the cutting edge, which shortens the life of the end mill. - Judging from the two facts mentioned above, the conclusion is that the existence of a torsion angle (axial rake) allows for smooth cutting, but the existence of this torsion angle itself causes "waviness" on the finished surface. It is also the cause of such occurrences. Furthermore, since cutting is performed with an end mill in a cantilevered state, the shape of the end mill itself must be highly rigid, otherwise the end mill will suffer from elastic deformation due to cutting resistance in addition to two series of poor finishing. Although this results in a large error in cutting accuracy, conventional end mills have a large blade groove depth even though the radial depth of cut is small in finishing cutting. In addition, these problems are further exacerbated by their synergistic effects, and when the depth of cut in the axial direction is large (especially when the depth of cut is twice the diameter of the end mill), the length of the outer cutting edge becomes longer. Therefore, this tendency is noticeable.

[Purpose of the invention]

The present invention has been devised in view of the problems of the prior art as described above, and is intended to effectively solve these problems. Therefore, the object is to provide an end mill that can smoothly cut the side surface and suppress deterioration of accuracy such as "waviness" on the finished surface as much as possible.

[Means to solve the problem]

The end mill of the present invention has the following configuration in order to solve the problems of the prior art and achieve the objectives. That is, it is equipped with a twisted peripheral cutting edge that always contacts the cut surface, which is divided into a cylindrical shape corresponding to the specified axial depth of cut and radial depth of cut, with a constant number of simultaneous cutting edges, Further, the depth dimension of the blade groove portion corresponding to the outer circumferential cutting edge is set to be 0.15 times or less the outer diameter dimension of the enlarging mill. In particular, when the number of simultaneous cutting blades is 1, the tangent of the helix angle of the peripheral cutting blade is set equal to the ratio of the circumferential dimension of the peripheral circle of the end mill to the product of the axial depth of cut and the number of blades. There is.

[Effect]

According to the end mill according to the present invention, although the peripheral cutting blades are twisted blades, the number of cutting blades simultaneously involved in cutting is always constant, so that the contact of each peripheral cutting blade with the cut surface of the workpiece is The contact is continuous rather than intermittent, and the cutting resistance shared by each cutting edge is always constant and does not fluctuate. In addition, since the depth of the blade groove is 0.15 times the diameter of the end mill or less because it is an end mill for finish cutting and the radial depth of cut is sufficiently small, this allows the core thickness to be set large and increases rigidity. can be increased.

【Example】

A preferred embodiment of the present invention will be described below with reference to FIGS. 1 and 2.
This will be explained with reference to the figures. FIG. 1 is an explanatory diagram schematically showing the contact state of the end mill according to the present invention with a workpiece. Here, the specified axial depth of cut a is 30 mm, the radial depth of cut (cutting width) b is 005, and the end mill diameter is 10 mm.
, the number of blades N is 2, the number of simultaneous cutting blades Ns is l, the rotation direction of the end mill is the direction of arrow R, the central angle of the surface to be cut 2 is φ, the helix angle β of the outer cutting edge, the first cutting edge l, When the axial pitch between the second cutting edge I and the second cutting edge I is ρ, the number of simultaneous cutting edges Ns is calculated using the formula (+
) can be expressed as However, N is the number of blades of the end mill, L is expressed by Equation (2), and Q is expressed by Equation (3). L−π・D−cotβ −(2
) Ma Noni, expressed as . (2), (3) formula nia = 30 mz, b = 0,
05 myn. Substitute D=IOmm, express L and ρ as a function of β,
Furthermore, when β is determined by substituting N5=1 into the (+) equation along with L and ρ, it becomes β-27.6°. However, at this time cos φ-099, and φ-8. ■1°
(#O, I 42rad). In the figure, reference numeral 11 denotes a first cutting edge that has finished cutting the surface 2 to be cut and is about to move away from the surface 2 to be cut. Reference numeral 12 denotes a second cutting edge which starts to come into contact with the surface to be cut 2 at the same time as the first cutting edge 11 finishes cutting, and is about to start cutting. Each of the four corners of the surface to be cut 2 is defined as P, , P2
．． P3. P, and when the first cutting edge II passes the point P1, the second cutting edge 1° passes the point P1, and cutting within the cut surface 2 is performed by the first cutting edge 1. There is a continuous and smooth transition from cutting by the second cutting edge I to cutting by the second cutting edge I, and the number of simultaneous cutting edges Ns always remains a constant value. That is, before cutting by the first cutting edge I is completed, in other words, before the first cutting edge 11 reaches the point PI, the second cutting edge 1. When cutting begins, the number of simultaneous cutting edges Ns becomes 2 from this point until the first cutting edge 11 passes point P, and the cutting resistance fluctuates, resulting in "undulations etc." On the other hand, the first cutting edge II is at point P
If the second cutting blade 12 has not yet reached the point P3 even after passing through the point P3, there will be a time period in which no cutting is performed by any of the cutting blades, and as a result of intermittent cutting, the second cutting blade 12 will not reach the point P3. When cutting begins, an impactful cutting force is applied to the second cutting edge I.
, causing chipping and "peeling" of the cut surface. Note that since the radial cutting amount is also finish cutting, it is sufficiently smaller than the end mill diameter, and it is also possible to perform approximate calculations by assuming that b=o. In this case, Q=a in equation (2), and this is applied to N5 in equation (1).
By substituting with =1, we obtain, and the tangent of the torsion angle β is as follows. In addition, FIG. 2 is a cross-sectional view of the end mill of this embodiment in the direction perpendicular to the axis, and the depth d of the blade groove 3 for discharging chips is 1.4 mm, which is less than 0.15 times the diameter of the end mill. This design does not form an unnecessarily large blade groove, and the size is the minimum required size according to the radial depth of cut, and the core thickness dimension C increases accordingly, increasing rigidity. It is being In this example, when the number of simultaneous cutting blades Ns is 1, that is, when the first cutting blade leaves the surface to be cut, the next two cutting blades start to newly contact the surface to be cut. Although the case where the cutting edge is the second cutting edge has been described, the case is not limited to this case, and it is theoretically possible that the cutting edge that starts contacting at this timing is the third or fourth cutting edge.

【Effect of the invention】

As is clear from the above description, the present invention provides the following excellent effects. In other words, it eliminates fluctuations in cutting resistance when performing side cutting, enables continuous and smooth transition between each peripheral cutting edge, and improves the rigidity of the end mill, especially when cutting with a large axial depth of cut. It is possible to prevent "waviness" and "peeling" on the finished surface and improve the precision of the finished surface as much as possible.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically showing the contact state of the end mill according to the present invention with a workpiece, FIG. 2 is a cross-sectional view of the end mill of the present embodiment in the direction perpendicular to the axis, and FIG. FIG. 4 is a perspective view illustrating the state of the finished face cut with a conventional end mill, and FIG. 5 is a perspective view illustrating the state of side cutting with a straight edge end mill. be. 11+ 12・Outer peripheral cutting edge, 2...Cut surface, 3・Blade groove, a...Axial depth of cut, b.Radial depth of cut, C...Core thickness dimension, d...Depth of blade groove Size, D...
・Diameter dimension of end mill, β ・Torsion angle of peripheral cutting edge 1st
Figure 2x 1N leap day, UG3-221913 (4) Figure 3 Figure 4 Tsumugisa - □

Claims (2)

[Claims] (1) A constant simultaneous cutting edge is always applied to the cut surface (2), which is divided into cylindrical sections corresponding to the specified axial depth of cut (a) and radial depth of cut (b). number(
The end mill is equipped with twisted peripheral cutting edges (1_1, 1_2) that contact each other at the peripheral cutting edges (1_1, 1_2), and the depth dimension (d) of the blade groove (3) corresponding to the peripheral cutting blades (1_1, 1_2) is equal to the outer diameter of the end mill. An end mill characterized in that the dimension (D) is set to 0.15 times or less. (2), the helix angle (β
) is the axial depth of cut (a) and the number of teeth (N).
The end mill according to claim 1, wherein the ratio of the circumferential dimension of the outer circumference of the end mill to the product of is equal to the ratio of the circumferential dimension of the outer circumferential circle of the end mill.