ES2359628T3 - ROTATING TOOL AND CUTTING INSERT. - Google Patents

Abstract

A rotary tool with interchangeable insert in which the inserts are placed detachably; the insert comprising front and bottom surfaces (14, 16) substantially square in shape and one side curved outwardly (15) on each side surface, and having a positive type shape in which a line (11) formed by said face and lateral saying serves as a cutting edge; each side (15) having a substantially centered flat surface part (12) extending towards said lower surface without making contact with said cutting edge; a main cutting edge formed by said outwardly curved edge line that extends circularly from its lowest point (7) to a periphery of said tool when said insert is placed in said rotary tool with interchangeable insert, so that it has a negative radial angle of attack (Rr) and a real angle of reduction between + 3º and + 15º; and said lower point (7) being inward with respect to a center of said main cutting edge (11) curved outward.

Description

The present invention relates to a rotary tool, with interchangeable insert such as a front milling tool, etc. Suitable for fast-moving jobs, and using a disposable insert.

As a rotary tool with an interchangeable fast-forward insert, the Japanese patent pending assignment No. 2000-126920 discloses a front milling cutter head equipped with disposable inserts. This front milling cutter head comprises disposable round inserts, each with a hole for mounting in the center, cylindrical supports each having a support seat at a pointed end to fix the disposable round insert by means of a flat head screw in a direction such that its upper surface serves as a side and its lateral surface serves as a face, a body of the cutting head for fixing the cylindrical supports and cotter pins, each inserted into a plurality of circular holes arranged in the peripheral part of a front surface of the body of the cutter head in parallel with its axis and pressed into a space between a flat surface disposed on a periphery of each cylindrical support and the body of the cutter head. When attached to the support, the disposable insert is tilted in the backward direction of rotation and towards the periphery of the cutting head, with a cutting edge formed by a transverse edge of the upper face and the side surface curved outward in the direction front surface and in the direction of rotation of the cutter head. In this way, with each disposable round insert placed in the tool tilted in two directions, a large circular cutting edge is disposed that exerts a reduced impact in a fast forward cutting.

Because this front milling tool comprises disposable round inserts, the surfaces of each insert with which the insert is attached to the tool are a bottom surface and a side surface. However, because the lateral surface of the insert is a curved surface, precise placement is difficult, so you need a screw to control the position of the edge. In addition, because the round insert is positioned inclined in two directions it is possible for the insert to rotate during cutting, resulting in the edge position deviating. Therefore, this tool is suitable for working at a depth of cut as small as 0.1–1mm or less, and if the tool is designed larger for a deeper cut, an embedded cutting edge becomes too long, giving place to a cutting resistance too large.

As another example of rotary tools with high efficiency interchangeable inserts, the Japanese patent pending assignment No. 2000-5921 discloses, as shown in Figure 24, a rotary tool of disposable type of rapid advance comprising a plurality of disposable inserts 301 , each disposable insert 301 having a straight or circular peripheral cutting edge to have a backward taper δ towards a circular main cutting edge 311 and a central axis of the tool 302, and the main cutting edge 311 having an angle k of the cutting edge between 3º and 35º. With the main cutting edge 311 of the disposable insert 301, the chips generated in the initial cutting phase are thin and gradually become thicker as the tool rotates. Therefore, a great impact force is not applied to the tool, which allows a rapid advance of the steel that experiences few variations in its cutting conditions. For example, in the case of steel cutting, which is free of intermittent cutting, a stable cut is achieved even under the conditions of a fz feed per tooth of 2 mm / tooth.

However, it has been found that this rotary tool of disposable type of rapid advance is not necessarily satisfactory to achieve a greater advance per tooth. Furthermore, because this disposable insert 301 has the main circular cutting edges 311 on two opposite surfaces with two other opposite surfaces for contacting the tool, it is not economically advantageous.

Document FR 1,536,303 A discloses a cutting insert for placement in a rotary tool, the insert having a substantially square face and lower faces and a side curved outward on each side surface. An outwardly curved edge line between the aforementioned face and a side serves as a cutting edge. Each side has a flat surface part that extends to the bottom surface but does not make contact with the cutting edge.

Document GB 1,142,820 A discloses a rotary tool that has detachable cut-in inserts with a negative radial attack angle and a positive axial attack angle.

It is an object of the present invention to provide a rotary tool in which the cutting inserts are detachably placed and that is capable of making a stable cut without the inserts cracking, even for rapid advance work on work pieces that They have large variations of cutting conditions.

This object is achieved by a rotary tool with interchangeable cutting inserts, as set forth in Claim 1. The dependent claims are related to the preferred embodiments of the invention.

Consequently, desirable embodiments are a rotary tool, with long-life interchangeable inserts, such as a front milling tool capable of making a stable cut without the inserts cracking, even for fast-forwarding work at a depth of cut of approximately 1-6 mm. especially for parts that experience large variations in cutting conditions such as parts that have many holes and pre-hardened steel, etc. and for which disposable inserts are used.

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Therefore, the embodiments provide a rotary tool with interchangeable insert such as a front milling tool, which can be operated with rapid advance while having high precision, and which can stably cut parts that experience large variations. under cutting conditions such as parts with many holes, pre-hardened steel, etc.

The disposable insert used in a rotary tool with interchangeable insert has a long service life and excellent cracking resistance.

As a result of intensive research, the inventor has considered that placing disposable inserts of substantially square shape comprising laterals with a flat surface part in a substantially central part of a rotary tool with interchangeable insert, so that the radial attack angle is negative , and that a main cutting edge formed by an outwardly curved edge line extends circularly from the lowest point to a periphery of the tool, the impact applied to the disposable inserts in a cutting process is softened, thereby obtaining Fast forward cutting mode and long service life with intermittent cutting.

Therefore, the disposable insert removably placed in a rotary tool with interchangeable insert of the present invention substantially comprises a square-shaped face and a bottom surface and a side curved outwardly on each side surface, the disposable insert having a type shape positive in which an outwardly curved edge line formed by the face and side serves as a cutting edge, each side having a substantially central part a flat surface portion that extends towards the bottom surface without making contact with the cutting edge, and a main cutting edge formed by the outwardly curved edge line that extends circularly from its lowest point towards the periphery of the tool when the insert is placed in the rotary tool with interchangeable insert, so that have a negative radial angle of attack.

An angle between the flat surface part and the face is preferably 3 ° to 10 ° less than an angle between the face and the side.

Part of the circular cutting edge is preferably straight. Also, the main cutting edge is preferably constituted by a plurality of straight lines and / or curved lines.

The disposable insert preferably has a fracture-shaped front groove along the main cutting edge.

The radius of curvature of the curved edge line is preferably 0.6–1.6 times the diameter of a circle inscribed in the insert.

The rotary tool with interchangeable insert according to the present invention comprises disposable inserts placed detachably in the rotary tool with interchangeable insert, the insert substantially comprising a square face and bottom surface and a side curved outward on each side surface , and having a positive type shape in which a curved edge line formed by the face and side serves as the cutting edge; each side in a substantially central part having a flat surface part that extends towards the lower surface without making contact with the cutting edge; a leading cutting edge formed by the outwardly curved edge line extending circularly from its lowest point to a periphery of the tool when the insert is placed in the rotary tool with interchangeable insert, so that it has an angle of attack negative radial; and the lowest point being inward with respect to a center of the main cutting edge curved outward.

The main cutting edge preferably has a cutting angle of 35% or less. Also, the angle of radial attack is preferably between -5 ° and -45 °. In addition, the main cutting edge has a real recess angle between + 3º and + 15º.

In a preferred embodiment, the radial angle of attack of the main cutting edge changes continuously or intermittently towards the periphery of the tool.

Certain preferred embodiments will be described below by way of example only and with reference to the accompanying drawings, in which:

Figure 1 is a front view showing a disposable insert according to an embodiment of the present invention;

Figure 2 (a) is a side view of the disposable insert of Figure 1, which is viewed from the direction A with Figure 2 (b) showing an enlargement of the part within a circle in Figure 2 (a );

Figure 3 is a side view of the disposable insert of Figure 1, which is viewed from the direction B;

Figure 4 is a perspective view showing the disposable insert according to an embodiment of the present invention;

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Figure 5 is a bottom view showing the front milling tool according to an embodiment of the present invention;

Figure 6 is a view of the straight section taken along the line C-C in Figure 5;

Figure 7 is a partial, enlarged view of the straight section showing the details of a cutting process using the disposable inserts according to an embodiment of the present invention;

Figure 8 is a partial, enlarged view of the straight section showing the details of a cutting process using the disposable insert according to another embodiment of the present invention;

Figure 9 is a partial, enlarged view of the straight section showing the details of a cutting process using the disposable insert according to a further embodiment of the present invention;

Figure 10 is a perspective view showing the disposable insert according to yet another embodiment of the present invention;

Figure 11 is a partial, enlarged view of the straight section showing the details of a cutting process using the disposable insert of Figure 10;

Figure 12 is a partial, enlarged view of the straight section showing the details of a cutting process using the disposable insert according to another additional embodiment of the present invention;

Figure 13 is a partial, enlarged view of the straight section showing the details of a cutting process using the disposable insert of Comparative Example 1;

Figure 14 is a partial, enlarged view of the straight section, showing the details of a cutting process using the disposable insert of Comparative Example 2;

Figure 15 is a partial, enlarged bottom view showing the front milling tool of Example 2;

Figure 16 is a partial, enlarged bottom view showing the front milling tool of Example 3;

Figure 17 is a partial, enlarged bottom view showing the front milling tool of Example 4;

Figure 18 is a perspective view showing a section of the part in the Examples and in the Comparative Examples;

Figure 19 is a graph showing the results of the advance limit test in Examples 2-4 and in Comparative Examples 1-3;

Figure 20 is a graph showing the results of the life test in Examples 2-4 and in Comparative Example 1;

Figure 21 is a partial, enlarged view of the straight section showing the details of a cutting process using the disposable insert according to another additional embodiment of the present invention;

Figure 22 is a partial, enlarged view of the straight section, showing the details of a cutting process using the disposable insert according to another additional embodiment of the present invention;

Figure 23 is a partial, enlarged bottom view showing the front milling tool according to another additional embodiment of the present invention;

Figure 24 is a partial view of the straight section showing the rotary tool of the rapid advance disposable type described in Japanese Patent Pending Assignment No. 2000-5921.

Figure 1 shows a disposable insert 1 according to an embodiment of the present invention, Figure 2 (a) is a side view of this disposable insert 1 seen from the direction A, and Figure 2 (b) is a partial view, enlarged, of the straight section, which shows a part within a circle in Figure 2 (a). Figure 3 is a side view of the disposable insert 1 of Figure 1 viewed from the B direction.

This disposable insert 1 has a substantially square shape as a whole, with a cutting edge 11 curved outward on each side. With respect to the shape of the cutting edge 11, the term "curved outward" means that the insert 11 has a sharp edge outward. However, it is not necessary that the entire cutting edge 11 have a single radius of curvature, but may consist of a plurality of curved lines and may be partially straight. In addition, the insert 1 can have a slot with a fracture-shaped face along the main cutting edge 11 curved outward. Although a connecting part of the adjacent cutting edges is preferably beveled with a curve having an appropriate radius of curvature, the bevel may not be necessary in some cases with direct connection of both cutting edges 11.

The circular cutting edge 11 has a radius of curvature R preferably from 0.6 to 1.6 times the diameter D of a circle inscribed 13 in the insert 1. When R / D is less than 0.6 times, the insert 1 It has substantially the same shape as a round insert, resulting in a large cutting edge angle in applications with a large depth of cut, which makes it impossible to make the cut with rapid advance. To make the depth of cut greater with an angle of the cutting edge without changing, the inscribed circle 13 should be increased. When R / D is greater than 1.6 times, the cutting edge 11 has substantially the same shape as a straight cutting edge, losing the advantages of the curved cutting edge, which has a long service life due to the length long contact between the cutting edge 11 and a piece during cutting, high resistance in intermittent cutting, and high resistance to fracturing even when heat fracturing occurs due to a compression force during cutting.

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A part 12 of the flat surface disposed in a substantially central part of the side 15 on each side of the insert 1 extends from a position 12a separated from the curved cutting edge 11 a small distance TS to a lower surface 16.

The flat surface part 12 serves as a stop surface when the insert 1 is placed in a tool body, which allows precise placement of the insert 1. An angle α of the flat surface part 12 with the face 14 is preferably from 3º to 10º less than an angle β of face 14 with side 15. When this difference (angle θ) is less than 3º, a sufficient area of the stop surface is not obtained. On the other hand, when it is less than 10º the edge resistance decreases.

Figures 5 and 6 show a front milling tool as an example of the rotary tool with interchangeable insert of the present invention, Figure 5 being a bottom view and Figure 6 being a view of the straight section taken along the line CC in Figure 5. As shown in Figure 6, each disposable insert 1 is placed in a tool body. The mounting mechanism of the insert 1 is known by itself. As shown in Figures 5 and 6, the insert 1 can be held by a key 4 by means of an insert support element 3 having a seat for insert support 1, so that the insert 1 is placed in the body of the tool. Alternatively, the insert 1 may be provided with a clamping hole in the central part of a clamping mechanism.

Figures 7-9 are enlarged views of the straight section that show in detail how an insert 1 placed in the front milling tool shown in Figure 6 cuts a piece W. Figures 7-9 indicate that at an angle k of the cutting edge fixed so that the lowest point 7 of the cutting edge 11 is located inside the tool with respect to a center of the cutting edge 11, a cutting part where the cutting edge 11 is placed can be long to prevent a part of the center of the cutting edge 11 having the weakest resistance from being first contacted with a piece W, and thus subjected to impact. The angle k of the cutting edge is preferably 35 ° or less.

The inventors have investigated the mechanism of impact generation in the insert 1 in a cutting process, independently in (1) impact when the insert 1 begins to bite the piece W (at the beginning of the cut), (2) impact during a period from application to part W to separation from it. As a consequence, the inventors have considered that the impact (1) can be reduced by making the lowest point 7 of a main cutting edge 11 as a cutting starting point to bite a bit deeply in a piece W, and the impact ( 2) can be reduced by providing a negative angle of radial attack Rr. With the rotary tool with interchangeable insert having these characteristics, the chips 8 generated by the contact with the piece W in the initial cutting phase are thin and gradually become thicker as the tool rotates, as shown in Figure 7 In this way, a large impact force is not applied to the tool, which allows rapid tool advance and stable intermittent cutting with a long service life of the disposable inserts 1.

The disposable insert 1 is placed in the rotary tool with interchangeable insert preferably so that it is negative and between -5 ° and -45 °. The radial angle of attack Rr of the main cutting edge 11 can change continuously or intermittently as it approaches the periphery of the disposable insert 1. The actual reduction angle of the main cutting edge 11 is preferably between + 3rd and + 15th. Incidentally, the actual recess angle is an angle obtained by synthesizing the axial attack angle and the radial attack angle. The actual recess angle and axial angle of attack are defined in JIS B0170.

To improve the surface conditions of the worked surface, disposable inserts 1 according to the above embodiments can be modified as described below. For example, Figure 8 shows an example with a secondary cutting edge 10, and Figure 9 shows an example with an inner peripheral cutting edge 6. Figures 10, 11 show a bevelled example in a corner portion 21 with a angle γ substantially equal to, or greater than, the radial angle of attack, and Figure 12 shows an example of Figure 11 with a secondary cutting edge 10 added.

The present invention will be described in detail with reference to the Examples that follow with no intention of limiting the present invention to them.

Example 1, Comparative Examples 1, 2.

The specifications of the disposable insert 1 of the present invention shown in Figures 1-4 were set as follows:

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Diameter D of the inscribed circle 13: 15,875 mm,

Radius of curvature R of the circular cutting edge 11: 15 mm,

Angle α between face 14 and the flat surface part 12: 70 °,

Angle β between face 14 and side 15: 75 °, and

Thickness T: 4.76 mm.

As shown in Figure 2 (b), the flat surface portion 12 that extends along the side 15 from a position 12a is displaced 0.5 mm backwards from the cutting edge 11 to the bottom surface 16. This insert 1 was placed in the front milling tool body shown in Figure 5. A radial angle of attack Rr was set at -4 °, and an axial angle of attack was set at 9 °. An angle of the cutting edge was set at 15 °, so that the lowest point 7 of the cutting edge 11 was located radially inward with respect to a center of the cutting edge 11.

For comparison, a disposable insert 101 of a regular triangle shape having a straight cutting edge 111 shown in Figure 13 (Comparative Example 1), and a disposable insert 201 of square shape having a straight cutting edge 211 shown in the Figure 14 (Comparative Example 2) were placed respectively in a front milling tool for a cutting test. An angle of the cutting edge was 90 ° in Comparative Example 1 and between 30 ° and 45 ° in Comparative Example 2.

With these tools, a test was carried out at the maximum feed rate with the following cutting specifications to compare the maximum feed rate Fmax and the quantity Q of chips discharged per unit of time.

Diameter of the cutting edges: 200 mm (with the total set of 10 inserts),

Part: S50C,

Cutting depth Ad: 2 mm, and

Cutting width Rd: 180 mm.

The advance fz of the insert 1 per tooth could be made as large as 2.5 mm / tooth at a cutting speed V as low as 100m / minute of Example 1.

Under these conditions the stable cut was maintained until the forward speed F of the platform reached

4,000 mm / minute and the quantity Q of discharged chips reached 1,440 cm3 / minute.

On the other hand, F was 800 mm / minute, and Q was 288 cm3 / minute in Comparative Example 1, because the insert 101 cracked when the feed per tooth was greater than 0.25 mm / tooth at a speed of V cut of 180 m / minute. Also, the advance fz per tooth was limited to 0.4 mm / tooth or less with F = 1,280 mm / minute and Q = 460.8 cm3 / minute in Comparative Example 2 due to the strength limit of insert 201 at a speed of cut V of 180 m / minute.

It follows that the speed of advance F of the platform per unit of time and the quantity Q of discharged chips was 3 to 5 times improved in Example 1 with respect to Comparative Examples 1 and 2. Because the Insert 1 of Example 1 had the main cutting edges 11 curved outwards, each cutting edge 11 bites a shallow piece W from the lowest point 7 of the insert 1 at the beginning of cutting, resulting in a small impact. Therefore, the fz feed per tooth could be made as large as about 1.0 to 3.5 mm / tooth even when cutting a steel such as the S50C.

With a radial angle of attack with a large negative angle, specifically from approximately 0 ° to approximately -40 °, so that the actual recess angle is large and not negative, there is a large bite time of the insert 1 in the piece W from the lower point 7 to the contour 9. As a result, the insert 1 is strong enough in the intermittent cut, and the disposable insert 1 has a long service life due to a large contact length between the cutting edge 11 and the part W On the other hand, chips of uniform thickness are generated during cutting in the case of inserts 101, 201 of Comparative Examples 1 and 2. Therefore, a smaller angle of the cutting edge would produce thinner chips. Thus, the fz feed per tooth was as small as about 0.2 to 0.4 mm / tooth in the cutting of a steel such as the S50C.

Examples 2-4, Comparative Example 3

Using the insert of Example 1, the axial angle of attack of a tool body was set at 9 °, and the angle k of the cutting edge was set at 15 ° so that the lowest point 7 of the cutting edge was located inward with respect to a center of the cutting edge. The radial angle of attack Rr was -10 ° in Example 2 shown in Figure 15, -15 ° in Example 3 shown in Figure 16, and -20 ° in Example 4 shown in Figure 17. A comparison also tested a tool with a radial angle of attack Rr of -4º (Comparative Example 3), and the tools of Comparative Examples 1 and 2.

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Using the tools of Examples 2 and 4 and Comparative Examples 1-3 (each front milling tool with 6 teeth, in which only one insert was placed), a test was performed on a piece with a large number of holes , each with a diameter of 8 mm shown in Figure 18, which easily caused the cracking of the inserts, to measure the advance fz per tooth, which expresses the cutting efficiency, until each insert was subjected to an initial cracking . The cutting specifications were subject to initial cracking. The cutting specifications were as follows:

Cutting edge diameter: 125 mm,

Part: pre-hardened steel [SCM440 (HS40)],

Cutting speed: 150 m / minute,

Ad depth of cut: 1 mm, and

Cutting width: 90 mm.

The results of the cut are shown in Figure 19. There was no cracking in the inserts of Examples 2-4 and in Comparative Example 3, even though the fz feed per tooth was increased by 0.1 mm / tooth from 0.1 mm / tooth to 0.8 mm / tooth. On the other hand, cracking occurred in a fz feed per tooth of 0.25 mm / tooth in the insert of Comparative Example 1. There was also cracking in a feed per tooth of 0.4 mm / tooth in the insert of Comparative Example 2.

In conditions so hard that they exceed common sense, with a fz feed per tooth increased to 1.5 mm / tooth, a cutting test was carried out to compare the life of each tool. The results are shown in Figure 20. While the service life was 3 minutes in Comparative Example 3, it was 33 minutes in Example 2, 40 minutes in Example 3, and 17 minutes in Example 4. From these results it remained confirmed that the angle of radial attack Rr increased in a negative direction, the life of the inserts increased even under extremely harsh intermittent cutting conditions. The actual recess angle was 6.1 ° in Example 2, 4.8 ° in Example 3, 3.4 ° in Example 4, and 7.7 ° in Comparative Example 3. These results confirmed that when the actual recess angle it was 3º or greater the useful life of the inserts was long even in conditions of intermittent cut extremely hard.

Examples 5-8

The same effect was obtained with a main cutting edge 11 consisting of a curved line that extends from the lowest point 7 towards the periphery and a straight line as shown in Figure 21 (Example 5), with an edge of main cut 11 consisting of a plurality of straight lines from around the lowest point 7 towards the periphery with an angle k of the cutting edge of 35 ° or less, as shown in Figure 22 (Example 6), with a negative radial angle of attack Rr intermittently changed as shown in Figure 23 (Example 7), or with a radial angle of attack Rr uniformly and continuously changed with a convex top surface of an insert (Example 8). This effect is obtained widely from a small diameter to a large diameter regardless of the diameter of the edge of the cutting tool.

As described above in detail, the rotary tool with interchangeable insert such as a front milling tool, etc., equipped with the disposable insert of the present invention can cut a part efficiently with a rapid advance and a long service life due to a resistance to improved cracking. The rotary tool with interchangeable insert of the present invention having such characteristics shows excellent cutting behavior of parts with many holes, of pre-hardened steel parts, etc.

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Claims (9)

1. A rotary tool with interchangeable insert in which the inserts are placed detachably; the insert comprising front and bottom surfaces (14, 16) substantially square in shape and one side curved outwardly (15) on each side surface, and having a positive type shape in which a line (11) formed by said face and lateral saying serves as a cutting edge; each side (15) having a substantially centered flat surface part (12) extending towards said lower surface without making contact with said cutting edge; a main cutting edge formed by said outwardly curved edge line that extends circularly from its lowest point (7) to a periphery of said tool when said insert is placed in said rotary tool with interchangeable insert, so that it has a negative radial angle of attack (Rr) and a real angle of reduction between + 3º and + 15º; Y said lower point (7) being inward with respect to a center of said main cutting edge (11) curved outward.

2.

 A tool according to claim 1, wherein said main cutting edge has an angle of the cutting edge (11) of 35 ° or less.

3.

 A tool according to claim 1 or 2, wherein said radial angle of attack (Rr) is between -5 ° and -45 °.

Four.

 A tool according to any one of claims 1 to 3, wherein the radial angle of attack (Rr) of said main cutting edge (11) changes continuously or intermittently towards the periphery of said tool.

5.

 A tool according to any one of claims 1 to 4, wherein an angle (α) between said flat surface part (12) and said face (14) is between 3 ° and 10 ° less than an angle (β) between said face and said side (15).

6.

 A tool according to any one of claims 1 or 5, wherein part of said cutting edge (11) curved outward is straight.

7.

 A tool according to any one of claims 1 to 6, wherein said main cutting edge (11) is constituted by a plurality of straight lines and / or curved lines.

8.

 A tool according to any one of claims 1 to 7, which has a fracture-shaped front groove along said main cutting edge (11).

9.

 A tool according to any one of claims 1 to 8, wherein the radius of curvature of said outwardly curved edge line (11) is 0.6 to 1.6 times the diameter of an inscribed circle (13) in said insert (1).