Patent Application
20130101363
1. Field of the Invention
The present invention relates to a cutting insert and an indexable milling tool to which the cutting insert is attached.
2. Description of the Related Art
In prior-art pocket machining performed in manufacture of a molding die or the like, a milling tool capable of drilling might be used. In the pocket machining, steady discharge of produced chips from a machined recess (pocket) is one of the conditions for efficient machining, and air-blow is used for that purpose. In this discharging method, a high-pressure air is injected toward the machined recess so as to blow out the chips to the outside of the hole by its wind pressure.
Even if the air-blow is used, injection of air at such high pressure that can blow out the chips of any size is not possible, and generation of chips broken up as fine as possible is required for a milling tool for performing the pocket machining. As a method of breaking up the chips, Japanese Patent Laid-Open No. 2007-283482 discloses a cutting insert in which a plurality of nicks is formed in a flank so as to discontinue a cutting edge.
However, the cutting insert having a nick as disclosed in Japanese Patent Laid-Open No. 2007-283482 cannot cut a portion where the nick is formed if the cutting insert is used singularly. Thus, a cutting insert having another shape for additionally cutting a portion which is not cut by the one cutting insert with a nick is further needed. Therefore, if the cutting insert having a nick is used, a plurality of types of inserts needs to be prepared all the time, which incurs an increase in a storage cost. Moreover, even if the inserts have different shapes, the difference is slight, and there was a chance of an attachment error of attaching an insert other than the type which should have been attached.
The present invention was made in order to solve the above-described problems and has an object to provide a cutting insert capable of breaking up chips with one type of insert and a milling tool to which the cutting insert can be attached.
That is, the cutting insert of the present invention is a cutting insert removably attachable to a tool body of a milling tool, including :
Preferably, the cutting insert has a cutting edge angle of small cutting edge located on the rear side in a feeding direction in two adjacent small cutting edges interposing a single separating portion therebetween is smaller than a cutting edge angle of the other small cutting edge located on the front side in the feeding direction.
Preferably, in the cutting insert, when a cutting edge angle of one small cutting edge is set to 5° or more and 20° or less, cutting edge angles of all the other small cutting edges are 5° or more and 20° or less.
Preferably, the separating portion is formed in a substantially linear in the cutting insert.
To the indexable milling tool of the present invention, the cutting insert of any of the present inventions described above is able to be removably attached.
In the cutting edge of the cutting insert of the present invention, the main cutting edge is separated into a plurality of portions, but since those cutting regions partially overlap each other, broken-up chips can be produced and moreover, machining with one type of a cutting insert is possible. Thus, a cost and a labor required for management of the cutting insert of the present invention become extremely smaller than before.
Moreover, when the cutting insert of the present invention is to be attached, it is not necessary to consider at which spot in the tool body which insert is attached, extremely smooth replacement/attachment works become possible.
In the main cutting edge of the cutting insert of the present invention, at least one separating portion not involved in cutting and connecting two separated small cutting edges is provided in the middle of the main cutting edge in a direction along the main cutting edge. Chips produced from each of the small cutting edges separated from each other are small in length in a direction along the main cutting edge and in volume, and such compact and light-weighted chips are easily discharged from the pocket by air-blow in pocket machining, and a defect in the cutting edge caused by biting of the chips or damage on a worked surface are suppressed.
In the indexable milling tool according to the present invention, since the cutting insert of the present invention is used, no labor is required such as attachment of inserts of different types depending on an insert attachment seat. Thus, a mechanical work is facilitated, and time for replacement work is made shorter than before.
Moreover, since the chips produced by the indexable milling tool according to the present invention are broken up and the thickness is small, if the indexable milling tool of the present invention is used in pocket machining, various problems caused by non-discharge of the chips from a machined hole such as biting of the chips and the like become difficult to occur.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
An end mill according to an embodiment of the present invention will be described below by referring to the attached drawings.
A cutting insert 10 according to this embodiment has a substantially parallelogram plate shape as illustrated in
The cutting insert 10 is a so-called positive type insert in which each of the flanks 15 is inclined inward as it gets closer to the lower face from the cutting edge and at least the cutting edge is made of a hard material such as cemented carbide, cermet and ceramic, ultra high pressure sintered compact such as diamond and CBN or any of the above-described material coated with metal compounds containing Ti, alumina or the like.
The cutting edge formed on a pair of short sides of the rake face 14 is provided with an acute angle corner 16, a wiper cutting edge 18 continuing to the acute angle corner 16, a main cutting edge 11 continuing to the wiper cutting edge 18, and an obtuse angle corner 17 continuing to the main cutting edge 11, and the wiper cutting edge 18 extends linearly in a direction substantially in parallel with the center feed axis H. The center feed axis H is an axis in parallel with a feeding direction in this embodiment, and the right side is the feeding direction in
The main cutting edge 11 is formed on the intersecting portion between the rake face 14 and the flank 15. This main cutting edge 11 is separated into two short small cutting edges by a separating portion 12 formed on the intersecting portion between the rake face 14 and the flank 15 similarly to the main cutting edge 11. Then, in the explanation below, the small cutting edge on the rear side with respect to the separating portion 12 in the feeding direction will be referred to as a first cutting edge 11a, and the small cutting edge on the front side with respect to the separating portion 12 in the feeding direction will be referred to as a second cutting edge 11b.
A peripheral cutting edge 13 is formed on each of a pair of long sides of the rake face 14, and the cutting insert 10 is attached so that the peripheral cutting edge 13 is in parallel with the central axis of the rotating tool body or a back taper is created.
A seat face 19 formed on the lower face of the cutting insert 10, a side face extending from the peripheral cutting edge 13 (flank 15), and a side face extending from the wiper cutting edge 18 (flank 15a) function as contact faces in contact with the seat face and a peripheral wall of an insert seat provided in the rotating tool body.
As illustrated in
In
The linear first cutting edge 11a of this embodiment is formed so that a first distance (Lb) from a first connection portion (Pb) located between the separating portion 12 and the second cutting edge 11b to the center feed axis H is longer than a second distance (La) from a second connection portion (Pa) located between the separating portion 12 and the first cutting edge 11a to the center feed axis H. In other words, the second connection portion (Pa) located between the first cutting edge 11a and the separating portion 12 is formed closer to the center of the cutting insert 10 than a virtual straight line (EL) obtained by extending the second cutting edge 11b toward the first cutting edge 11a (See
Thus, the separating portion 12 is formed closer to the rear side in the V-axis direction than an axis line passing through the first connection portion Pb and in parallel with the center feed axis H. The separating portion 12 is not brought into contact with a workpiece even if the second cutting edge 11b is performing cutting and so is not involved in cutting. Moreover, if the separating portion 12 as above is formed, an overlapped effective cutting region at the same time is produced between the effective cutting region of the first cutting edge 11a and the effective cutting region of the second cutting edge 11b. As a result, by using the single cutting insert 10 of this embodiment or just a plurality of the cutting inserts 10 of this embodiment, a portion not cut is not formed in the workpiece. Since the cutting insert 10 of this embodiment is a positive insert, a side face extending from the separating portion 12 to the lower face is also formed of an inclined face inclined inward of the cutting insert 10 as it goes to the lower face.
The cutting insert 10 of this embodiment does not form a portion not cut on the machined face as described above. Therefore, cutting by using only the cutting insert 10 of this embodiment is possible, and a storage cost is reduced. Moreover, if the cutting insert 10 of this embodiment is used in a milling tool using a plurality of cutting inserts, since labor to consider the type of the cutting insert for each attachment spot is not necessary, efficient cutting edge replacement can be realized.
The separating portion 12, the first cutting edge 11a, and the second cutting edge 11b are not limited to the above-described embodiment. That is, a main technical idea of the cutting insert 10 of the present invention is that the main cutting edge is separated into two or more short small cutting edges by providing a portion not involved in the cutting on the main cutting edge and an effective cutting region of each separated small cutting edge is partially overlapped with each other and thus, the cutting insert having the main cutting edge in a shape realizing the above is within a technical scope of the present invention.
Thus, the separating portion is not limited to a linear shape as in the above-described embodiment but may have a curved shape, for example. In that case, too, if the connection portion between the small cutting edge and the separating portion located on the rear side with respect to the separating portion in the feeding direction is formed closer to the center of the cutting insert than a virtual extension line obtained by extending the other small cutting edge on the front side in the feeding direction toward the small cutting edge located on the rear side in the feeding direction, the cutting edge angle can be set such that the separating portion is no longer involved in the cutting and the effective cutting regions of the two small cutting edges are partially overlapped. If the separating portion is a curved line, the curved line may be concavely curved in a recess shape toward the center of the cutting insert or may be convexly curved in a projection shape toward the outside of the cutting insert.
If the connection portion between the small cutting edge on the rear side in the feeding direction and the separating portion is located closer to the outside of the cutting insert than the virtual extension line of the small cutting edge located on the front side in the feeding direction, whatever cutting edge angle is set, the separating portion is also involved in the cutting. The term “front side in the feeding direction” refers to a place on the same side as the feeding direction than a certain position when the certain position is based, and the term “rear side in the feeding direction” refers to a place on the side in the direction opposite to the feeding direction with respect to the certain position when the certain position is based.
As another form of the cutting insert of the present invention, though the first cutting edge 11a and the separating portion 12 cross each other at an obtuse angle in this embodiment, they may instead cross each other at an acute angle. Similarly, the separating portion 12 and the second cutting edge 11b may cross each other at an acute angle or may cross each other at an obtuse angle.
As another form of the cutting insert of the present invention, one of the small cutting edges with respect to the separating portion can be linear and the other small cutting edge can have an arc shape (not shown). As still another form, the main cutting edge can have two or more separating portions and three or more small cutting edges (not shown). In this case, a relationship between a given separating portion and the small cutting edges connected to the both ends thereof needs to be such that, as described above, the connection portion between the small cutting edge located on the rear side with respect to the given separating portion in the feeding direction and the given separating portion is formed closer to the center of the cutting insert than the virtual extension line obtained by extending the other small cutting edge on the front side in the feeding direction toward the small cutting edge located on the rear side in the feeding direction. As another form of the cutting insert of the present invention, a triangle, a polygonal plate shape such as a pentagon, or a negative insert can be used as replacement.
Subsequently, the milling tool of the present invention will be described by using an end mill which is one embodiment thereof. As illustrated in
The cutting insert 10 is attached to the tool body 1 such that, as known from
In this end mill, as illustrated in
Since the second connection portion Pb between the separating portion 12 and the second cutting edge 11b protrudes toward the leading end of the tool body 1 further than the first connection portion Pa between the separating portion 12 and the first cutting edge 11a, the entire separating portion 12 is recessed closer to the rear end of the tool body 1 than at least a leading portion of the second cutting edge 11b. Thus, the separating portion 12 becomes a portion not brought into contact with the workpiece at all and not involved in the cutting during machining. It is needless to say that the side face extending from the separating portion 12 to the lower face is also formed of an inclined face inclined inward of this cutting insert as it goes to the lower face so as not to touch the workpiece.
According to the cutting insert and the end mill of this embodiment, one separating portion 12 not involved in the cutting is formed in the middle of the main cutting edge 11, and as a result, the main cutting edge 11 is separated into two parts, that is, the first cutting edge 11a and the second cutting edge 11b, and thus, each cutting edge produces a chip which is short and small in the volume and has a width according to a cutting edge length thereof. In pocket machining of a molding die, such compact and light-weight chips are easily discharged from the pocket by air-blow and thus, a defect in the main cutting edge 11, the outer peripheral cutting edge 13 and the like caused by biting of the chips can be suppressed.
Since the first cutting edge angle κ1 of the first cutting edge 11a and the second cutting edge angle κ2 of the second cutting edge 11b are set within a range of relatively small values, that is, a range of 5° or more and 20° or less, substantial chip thicknesses of the first cutting edge 11a and the second cutting edge 11b become small, and a load during the cutting applied to the entire cutting edges is reduced. As a result, damage on the first cutting edge 11a or the second cutting edge 11b or particularly damage on the cutting boundary portion is suppressed, and a life of the entire cutting edge is improved.
In a cutting tool having a small cutting edge angle of the main cutting edge, a contact length between the main cutting edge and the workpiece is long in general and a width of the chip is large. However, in the cutting insert and the end mill of this embodiment, since the main cutting edge 11 is split into the first cutting edge 11a and the second cutting edge 11b, the width of the chip produced by the respective cutting edges becomes shorter than the length of the main cutting edge 11. On the other hand, since the first cutting edge angle κ1 of the first cutting edge 11a and the second cutting edge angle κ2 of the second cutting edge 11b are set to small values, respectively, the thicknesses of the chips produced by the first cutting edge 11a and the second cutting edge 11b become small. As known from the above, since the separating portion 12 is formed on the main cutting edge 11, the cutting insert 10 and the end mill of this embodiment can generate a chip which is small in width and thickness. The chip which is small in width and thickness is formed into a coil or spring shape which is compact, light-weight, and elastically deformed easily and so is easily discharged. Thus, an effect of suppressing defect on the cutting edge caused by biting of the chips becomes extremely high.
Since the respective parts of the first cutting edge 11a and the second cutting edge 11b are included in a region between a line in parallel with the center feed axis H passing through the first connection portion Pa of the first cutting edge 11a and a line in parallel with the center feed axis H passing through the second connection portion Pb of the second cutting edge 11b (See
The rake face 14 of the cutting insert 10 according to this embodiment has a leading end of the obtuse angle corner 17 at the highest level in the thickness direction of the cutting insert 10, and as it separates from the obtuse angle corner 17, the level gradually lowers in the thickness direction of the cutting insert 10 (see
The two raised obtuse angle corners 17 are arranged at opposite ends of the short diagonal 28 while the lowered acute angle corners 16 are arranged at opposite ends of the long diagonal 26, with an inclined face 14a, being associated with each raised obtuse angle corner 17. The peripheral cutting edges 13 extend along the long sides 22F, 22R, each peripheral cutting edge 13 extending from one of the raised obtuse angle corners 17 towards an adjacent lowered acute angle corner 16. Meanwhile, the main cutting edges 11 extend along the short sides 24, each main cutting edge 11 extending from one of the raised obtuse angle corners 17 towards an adjacent lowered acute corner 16. Each main cutting edge 11 comprises separated first and second small cutting edges 11a, 11b, respectively, the second small cutting edge 11b being closer to the raised obtuse angle corner 17 than the first small cutting edge 11a. The non-cutting separation portion 12 formed between the first and second small cutting edges 11a, 11b on an intersecting portion between the rake face 14 and the flank face 15. In the front view of the rake face 14, a first connection portion Pa between the first small cutting edge 11a and the separating portion 12 is formed closer to a center of the insert—either or both the center feed axis H and the insert center C—than a virtual straight line extending through the second small cutting edge in a direction of the first small cutting edge 11a.
In the end mill attached with the cutting insert 10 with increased rake angles, a radial direction rake angle β of the first cutting edge 11a and the second cutting edge 11b mainly performing cutting increases. With the increase of the radial direction rake angle β, the cutting resistance is reduced, and stable machining with less tool rattling is realized in the pocket machining. The radial direction rake angle β is preferably a positive value rather than a negative value. If the radial direction rake angle β is positive, cutting resistance decreases and a direction of the cutting resistance is directed toward the center of the tool body 1. As a result, defect of the cutting edge is prevented. If the radial direction rake angle β is positive, an outflow direction of the chips produced by the first cutting edge 11a and the second cutting edge 11b is also directed toward the center of the tool body 1. Then, in wall face machining in which cutting is performed by leaving the wall face on the outer periphery side of the tool body 1 or particularly the wall face machining in pocket machining, the chips are prevented from being bitten in a gap between the wall face and the outer peripheral face 2 of the tool body. As a result, adhesion of the chips to the wall face is suppressed, and a quality of appearance of the wall face is improved.
Since the peripheral cutting edge 13 is arranged in parallel with the central axis A of the tool body 1 as in the end mill of this embodiment, the wall face of the workpiece is finished with high accuracy. However, if a contact length between the peripheral cutting edge 13 and the wall face becomes large, the increase in the cutting resistance might incur rattling of the tool, and thus, in order to prevent this, it may be so configured that the long side of the rake face 14 of the cutting insert 10 is inclined inward from the peripheral cutting edge from the middle thereof to the acute angle corner 16 or is recessed so that a back taper is provided arbitrarily.
The present invention has been described in the above-described embodiment and its variation and the like with some degree of specificity, but the present invention is not limited to them. For example, an end mill is used as an embodiment of a milling tool in the above description, but the milling tool of the present invention can be also applied to a milling tool other than the end mill such as a front milling cutter, a side cutter and the like. It should be understood that the present invention is capable of various modifications and changes without departing from the spirit or scope of the invention described in claims. That is, the prevent invention includes any variations, applications, and equivalents contained in the idea of the present invention specified by the claims.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-140511 | Jun 2010 | JP | national |
This application is a Continuation-in-part of International Application No. PCT/JP2011/062657 filed Jun. 2, 2011 and published as WO 2011/162081A1, which claims the benefit of Japanese Patent Application No. 2010-140511, filed Jun. 21, 2010. The contents of the aforementioned applications are incorporated by reference herein in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2011/062657 | Jun 2011 | US |
| Child | 13715231 | US |
