Positive cutting insert

Abstract

The invention relates to a positive cutting insert (10) having a chip surface (14), a main free surface (24) and a secondary free surface (26), wherein a cutting edge (12) is formed between the chip surface (14) and the main free surface (24), characterized in that the secondary free surface (26) is offset relative to the main free surface (24) towards the interior of the cutting insert (10) and is delimited on each side in a direction parallel to the cutting edge.

Description

Technical Field

[0001] The present invention relates to a positive cutting insert having a chipping surface, a primary free surface and a secondary free surface, wherein the cutting edge is formed between the chipping surface and the primary free surface. Background Technology

[0002] Cutting inserts are essential components in machining technology. They are used in tools such as rotary drills, milling tools, and drill bits, and allow for the efficient removal of material from a workpiece. In most cases, they are indexable so that when the cutting edge wears, a new, unworn cutting edge can be used effortlessly. Due to the cutting angle of positive cutting inserts, there are low cutting forces and high surface quality of machined workpieces.

[0003] Cutting inserts are typically manufactured using powder metallurgy. A mixture of powdered carbides is filled into a mold and pressed under high pressure to create a so-called "preform." This preform is then heated during a sintering process, whereby the powder particles fuse together, and the cutting insert acquires its final strength and hardness.

[0004] A key challenge in powder metallurgy manufacturing is achieving the most uniform density possible in the final pressed preform. Density variations in the preform lead to uneven shrinkage during sintering, which can in turn cause warping, cracking, or dimensional deviations in the finished cutting inserts.

[0005] It has been found, particularly for positive cutting inserts, that a recurring problem is that during the pressing operation, the powder material in the cutting edge region is compressed less than in other regions. This is due to the geometry of the drill bit shape and the different cross-sections along the cutting insert. Lower compression results in a lower density of the preform in the cutting edge region.

[0006] During the subsequent sintering process, the lower-density regions shrink more than the denser, compressed regions. This results in uneven shrinkage of the cutting insert, which compromises the precise geometry of the cutting edge. The consequence is dimensional deviations in the cutting insert, higher cutting forces, and correspondingly higher thermal loads, leading to a shorter service life. Summary of the Invention

[0007] The object of this invention is to manufacture positive cutting inserts characterized by particularly high dimensional consistency.

[0008] This invention provides an effective solution to this problem through a specific design of the free surface of the cutting insert. Generally, the section of the free surface removed from the cutting edge is more inward than the section closer to the cutting edge. Specifically, in the positive cutting insert of the type described above, the secondary free surface is configured to be offset inward relative to the primary free surface toward the cutting insert, and is restricted on each side in a direction parallel to the cutting edge.

[0009] This geometric adjustment allows for more uniform compression of the powder material throughout the pressing process. Specifically, it is compressed more in the cutting regions to achieve a more uniform density. By further retracting these regions away from the cutting edge, the cross-section of the cutting insert decreases at these locations. This results in more efficient transfer of the pressing force to the total powder volume, particularly to the critical areas at the cutting edge. The result is more uniform powder compression throughout the entire cutting insert. The constraint of the secondary free surface leads to specifically defined areas where higher pressing forces can be concentrated.

[0010] During sintering, the uniform packing density results in uniform shrinkage behavior. This maintains the geometric integrity of the cutting edge and significantly reduces dimensional deviations. This improves the precision and quality of the produced cutting inserts, and enhances their performance and service life in actual use.

[0011] Furthermore, this solution allows for optimized manufacturing processes without significant modifications to existing pressing tools or sintering furnaces. The improved free surface geometry can be achieved with minimal effort and reduces scrap rates.

[0012] In embodiments of the invention, the secondary free surface extends continuously from the first corner free surface to the second corner free surface. The technical advantage of this continuous second free surface is improved structural integrity of the cutting insert. The continuous surface allows mechanical stress to be evenly distributed along the secondary free surface, thereby avoiding localized stress peaks. This results in increased stability and service life of the cutting insert due to fewer fracture points and increased resilience to mechanical shocks.

[0013] In this configuration, the sub-free surface can be designed to be flat, allowing for manufacturing with minimal effort and high precision. Furthermore, during preform production, the pressing force is uniformly distributed along the sub-free surface, thereby improving the dimensional consistency of the sintered cutting blades.

[0014] In an alternative embodiment, the subfree surface is wavy, uneven, or concave when viewed along the associated cutting edge. A wavy subfree surface leads to increased mechanical stability of the cutting insert. The wavy structure better absorbs and distributes cutting forces, thereby increasing overall strength. Furthermore, it generates a larger surface area, allowing the wavy structure to better dissipate heat generated during machining, similar to cooling ribs.

[0015] In another embodiment, multiple secondary opening surfaces are disposed along one side of the cutting insert between the first and second corner free surfaces. The technical advantage of this design with multiple secondary opening surfaces is that they increase the structural strength of the cutting insert. By dividing the secondary free surfaces, stress can be dissipated more effectively and material weakening can be avoided. This results in improved service life and higher reliability of the cutting insert during continuous use.

[0016] The secondary free surface can be implemented as grooves, with extensions of the primary free surface extending between these grooves. Ribs, which are extensions of the primary free surface and are located between the grooves, serve as reinforcing structures that increase the rigidity of the cutting insert, stabilize the cutting edge, and effectively dissipate the cutting forces acting on the cutting edge.

[0017] In one embodiment, the groove tapers gradually towards the base side of the cutting insert, resulting in a straight outer edge on the base side (i.e., the support surface). The advantage of this embodiment is that the linear outer edge allows for precise positioning and securing of the cutting insert within the tool holder. The tapering of the groove towards the base side prevents stress concentration at the edges and reduces the risk of material weakening. This improves the durability of the cutting insert and ensures stable mounting. Furthermore, the large base side reduces surface compression.

[0018] The grooves can have a constant width, allowing mechanical stress to be evenly distributed along the sub-free surface. A uniform groove geometry also simplifies manufacturing and ensures consistent quality of the cutting inserts.

[0019] In one embodiment, the cutting insert has a fastening opening extending through the base side and through the chip surface. This cutting insert can be easily and securely installed using a fastening screw extending through the fastening opening, particularly in an existing receiving recess.

[0020] Cutting inserts can have polygonal shapes, making multiple mounting positions possible, where new, unworn cutting edges can be quickly obtained upon wear. In the case of rectangular cutting inserts, four possible mounting positions are created. Other examples include T-shaped and W-shaped inserts.

[0021] According to one embodiment of the invention, the cutting blade has a circular shape including a fastening opening extending through the base surface and through the chip surface. The compression of the powder during pressing also has a beneficial effect on cutting blades with circular cutting edges.

[0022] As an alternative to securing the opening, the cutting insert can be arranged such that it can be clamped on the tool holder from above using clamping jaws or the like.

[0023] According to one embodiment, the chip surface adjacent to the cutting edge is designed to be concave, which allows for particularly good and uniform powder compression when pressing preforms in conjunction with the retracted sub-free surface. Furthermore, the known advantages of concave chip surfaces can be utilized.

[0024] Alternatively, the chip surface can also be negative or flat. Attached Figure Description

[0025] The invention will now be described based on various embodiments shown in the accompanying drawings.

[0026] - Figure 1 Cutting blades based on existing technology;

[0027] - Figure 2 In the perspective view, the cutting blade according to the first embodiment of the present invention,

[0028] - Figure 3 A schematic cross-sectional view of the cutting blade during rotation according to the first embodiment;

[0029] - Figure 4 The cutting blade according to the second embodiment in a side view;

[0030] - Figure 5 In the plan Figure 4 Cutting blades,

[0031] - Figure 6 Perspective view Figure 4 Cutting blades,

[0032] - Figure 7 In the bottom view Figure 4 Cutting inserts;

[0033] - Figure 8 Along Figure 9 In the cross-sectional view of plane VIII-VIII Figure 4 Cutting inserts;

[0034] - Figure 9 Supplementing size information and Figure 4 Corresponding views;

[0035] - Figure 10 The cutting blade according to the third embodiment in the side view;

[0036] - Figure 11 In the plan Figure 10 Cutting inserts;

[0037] - Figure 12 Perspective view Figure 10 Cutting inserts;

[0038] - Figure 13 In the bottom view Figure 10 Cutting inserts;

[0039] - Figure 14 Along Figure 15 In the cross section of plane XIV-XIV Figure 10 The cutting blade; and

[0040] - Figure 15 Supplementing size information and Figure 10 Corresponding views;

[0041] - Figure 16 A cutting blade according to the fourth embodiment is shown in a side view;

[0042] - Figure 17 It shows Figure 16 A plan view of the cutting insert;

[0043] - Figure 18 It shows Figure 16 A perspective view of the cutting blade;

[0044] - Figure 19 It shows Figure 16 Bottom view of the cutting blade;

[0045] - Figure 20 It shows the addition of a cutting plane. Figure 16 Another view of the cutting blade;

[0046] - Figure 21 It shows along Figure 20 The plane XXI-XXI Figure 16 The cross-section of the cutting blade;

[0047] - Figure 22 The cutting blade according to the fifth embodiment is shown in a side view;

[0048] - Figure 23 It shows Figure 22 A plan view of the cutting insert;

[0049] - Figure 24 It shows Figure 22 A perspective view of the cutting blade;

[0050] - Figure 25 It shows Figure 22 Bottom view of the cutting blade;

[0051] - Figure 26 It shows the addition of a cutting plane. Figure 22 A side view of the cutting blade; and

[0052] - Figure 27 It shows along Figure 26 The plane of XXVII-XXVII Figure 22 A cross-sectional view of the cutting insert. Detailed Implementation

[0053] exist Figure 1 In the image, a positive cutting insert 10 according to the prior art can be seen. It has four cutting edges 12 formed at the transition between the chip surface 14 and the four free surfaces 16.

[0054] The cutting insert 10 is designed as a cube and has a fastening opening 18 extending from the chip face 14 through the body of the cutting insert 10 toward the base surface 20. Using the base surface 20, the cutting insert 10 extends in the recess of the tool holder.

[0055] The free surface 16 is designed to be flat, wherein the base surface 20 has a smaller profile than the chip surface 14. In other words, in the plan view, the cutting edge 12 protrudes from above beyond the base surface 20.

[0056] exist Figure 2 The first embodiment of the cutting blade 10 according to the present invention is shown in the figure.

[0057] With Figure 1 The cutting insert 10 is in the same manner. Figure 2 The cutting insert 10 is designed as a cube. Therefore, it has a square base surface 20, four side surfaces, and a chip surface 14 on the top side of the cutting insert 10.

[0058] Alternatively, the cutting insert can also be generally rectangular, for example, having a rhomboid shape. Such a cutting insert can be used for penetration.

[0059] Other alternatives are triangular boards, T-shaped boards, or W-shaped boards.

[0060] The base surface 20 forms the base of the cutting insert 10 and serves as a support surface in the tool holder. Four side surfaces 22 extend from the base surface 20, representing the free surface 16 of the cutting insert 10.

[0061] Each free surface 16 is divided into a primary free surface 24 and a secondary free surface 26.

[0062] The main free surface 24 directly adjoins the chip surface 14. The transition from the main free surface 24 to the chip surface 14 forms the cutting edge 12, on which the workpiece is machined during the machining process. The main free surface 24 forms a defined free angle with the plane defined by the base surface 20 to ensure optimal cutting conditions. Adjacent to the cutting edge 12, the chip surface 14 is concave in configuration to obtain optimal chip flow.

[0063] Additional geometric features may be provided on the chip surface 14 to guide the chips formed during machining in a desired manner.

[0064] Below the primary free surface 24, a secondary free surface 26 is arranged, which retracts inward toward the cutting blade 10. Therefore, the secondary free surface 26 is offset from the primary free surface 24, and the area "behind" the primary free surface 24 represents a cantilever or "balcony" extending "behind" the secondary free surface 26. In other words, the primary free surface 24 protrudes outward across the secondary free surface 26.

[0065] The width B of the secondary free surface 26, measured in the extension direction of the cutting edge 12, is a majority of the width of the cutting insert 10. In the exemplary embodiment shown, the auxiliary cutting edge 28 extends to the corner free surface 30 located below the cutting corner 32. In other words, the secondary free surface 26 is defined on each side in a direction parallel to the cutting edge 12, and is here defined by the corner free surface 30.

[0066] The special design of the cutting blade 10, with its retracted secondary free surface 26 and the resulting overhang, achieves uniform compression of the powder material during preform production. During the pressing operation, the pressing tool can act on both the chipping surface 14 and the base surface 20. In particular, the tool effectively impacts the powder material in the area of ​​the primary free surface 24.

[0067] The pressure applied from the top and bottom allows for uniform compression of the powder material, particularly in the critical areas of the primary free surface 24 and the cutting edge 12. Due to the reduced material thickness in the areas of the retracted secondary free surface 26, the compressive force is efficiently transferred across the entire cross-sectional profile. This results in a uniform density distribution within the preform.

[0068] During the subsequent sintering process, the preform shrinks uniformly because density differences have been minimized. This results in a cutting insert 10 with high dimensional consistency and a precisely defined cutting edge 12.

[0069] Due to its cubic shape, in this exemplary embodiment, the cutting blade 10 has four usable cutting edges 12. This increases the economic efficiency and flexibility of the manufacturing process.

[0070] exist Figure 3 In the middle, you can see Figure 2 The cutting insert 10 is used in applications where it is used to machine a workpiece by rotation. A tool holder for the cutting insert 10 is not shown here.

[0071] exist Figure 3 In the image, the balcony-shaped protrusion of the primary free surface 24 can be clearly seen, which is generated by the depression R of the secondary free surface 26 compared to the primary free surface 24. Figure 3 It is also clearly shown that when pressing the preform, the powder material can be well compressed from above and below because the pressing tool can act on the transition surface 27 from the primary free surface 24 to the secondary free surface 26, while pressing from above (i.e., the side of the chip surface 14).

[0072] It should be noted that the cutting inserts according to the invention, even though shown here for application in turning, can in principle be used in other cutting applications, particularly for milling.

[0073] Figures 4 to 9 A cutting insert 10 according to a second embodiment is shown. The same reference numerals are used for features known from the first embodiment, and reference is made in this regard to the above description.

[0074] The difference between the first and second implementation schemes is that, in the second implementation scheme, the sub-free surface 26 is designed differently.

[0075] Unlike the first embodiment, the secondary free surface 26 here does not extend continuously from one corner free surface 30 to another corner free surface, but is embodied as a plurality of grooves 34 arranged adjacent to each other. These grooves 34 extend downward toward the base surface 20 from the level where the main free surface 24 terminates in the first embodiment.

[0076] The ribs 36 that now exist between the multiple secondary free surfaces 26 represent extensions of the primary free surface 24 and continue downward from the primary free surface 24.

[0077] The groove 34 is arranged to taper gradually toward the base surface 20 of the cutting insert 10, such that the base surface 20 has straight outer edges 38 on all four sides. This facilitates the precise positioning and securing of the cutting insert 10 in the tool holder.

[0078] The advantage of the second embodiment is that it achieves a good trade-off between uniformly pressing the powder material during preform production and the high stability of the final cutting blade 10. The grooves 34 allow the pressing tool to apply pressure in segments from below the "balcony," allowing for high pressing forces in areas within the main free surface 24. The spacing of the grooves 34 is chosen to distribute the pressing force evenly across the overhanging portion of the material. Ribs 36 (i.e., extensions of the main free surface 24) serve as supports for the "balcony" (i.e., the overhanging main free surface 24).

[0079] The groove 34 here begins at a distance d from the cutting edge 12, which can be on the order of 0.1 mm to 1 mm. In the exemplary embodiment shown, the distance d is about 0.6 mm.

[0080] The depth t of the groove 34 can be on the order of 0.1 mm to 0.3 mm.

[0081] The distance from groove 34 to corner radius 40 is on the order of 0.1 mm to 1 mm.

[0082] In the exemplary embodiment shown, the height h of the trench 34 is approximately 3 mm.

[0083] The groove 34 is implemented here with a constant width, which simplifies production and ensures uniform mechanical load along the sub-free surface 26.

[0084] Figures 10 to 15 A cutting insert 10 according to a third embodiment is shown. The same reference numerals are used for features known from the second embodiment, and reference is made in this regard to the above description.

[0085] The difference between the second and third implementation schemes is that, in the third implementation scheme, the groove 34 forming the retracted subfree surface 26 does not have a constant width, but widens towards the base surface 20.

[0086] Another difference between the second and third embodiments is that, in the third embodiment, the groove 34 does not taper towards the base surface 20, but remains visible at the level of the base surface 20, i.e., as a recessed portion of the outer edge 38 of the base surface 20.

[0087] The ribs 36 formed between the grooves 34 also represent the continuous extension of the main free surface 24 after the cutting edge 12.

[0088] The groove 34 here begins at a distance d from the cutting edge 12, which can be on the order of 0.1 mm to 1 mm. In the exemplary embodiment shown, the distance d is about 0.5 mm.

[0089] The depth t of the groove 34 can be on the order of 0.1 mm to 0.3 mm. In the exemplary embodiment shown, the depth t is 0.3 mm.

[0090] The distance from groove 34 to corner radius 40 is on the order of 0.1 mm to 1 mm.

[0091] In the exemplary embodiment shown, the height h of the trench 34 is approximately 3.5 mm.

[0092] On the side surface of the chip surface 14, the distance m between the center lines of adjacent grooves 34 is approximately 1.4 mm. On the side surface of the base surface 20, the grooves 34 have a width b of approximately 1 mm, while the ribs 36 disposed between the grooves have a width r of approximately 0.4 mm.

[0093] Here, the half-open angle α of the extended groove 34 of the truncated section is 6°.

[0094] Figures 16 to 21 A cutting insert according to a fourth embodiment is described. Features known from previous embodiments are referred to using the same reference numerals, and reference is made in this regard to the above description.

[0095] The essential difference between the aforementioned embodiment and the fourth embodiment is that, in the fourth embodiment, the base body has a circular rather than angular configuration. Therefore, the cutting edge 12 has a circular shape, and the base surface 20 is also flat. The resulting support surface is annular and serves to provide support at the bottom of the receiving recess in the tool holder.

[0096] The chip surface 14 is located on the top side of the cutting insert 10 and is designed according to the aforementioned embodiment. A cutting edge 12 for machining the workpiece is formed between the chip surface 14 and the main free surface 24. The main free surface 24 extends downward from the cutting edge 12 and has the same clearance angle as in the aforementioned embodiment.

[0097] The secondary free surface 26 is offset toward the interior of the cutting blade 10 relative to the primary free surface 24, thereby forming an overhang, similar to the angular embodiment. This configuration allows for uniform compression of the powder material during preform production and results in high dimensional consistency of the final cutting blade 10. In this embodiment, the groove 34 extends to the base surface 20, such that the outer edge of the base surface 20 is a closed circle.

[0098] The fastening opening 18 extends axially from the cutting surface 14 to the base surface 20 through the cutting insert 10, so that the cutting insert 10 can be securely fastened in the tool holder.

[0099] Figures 22 to 27A cutting blade 10 according to a fifth embodiment is shown. Features known from previous embodiments are referred to using the same reference numerals, and reference is made in this regard to the above description.

[0100] Therefore, the cutting insert 10 has a generally circular base surface 20 and a correspondingly designed chip surface 14. The cutting edge 12 is formed between the chip surface 14 and the main free surface 24, similar to the aforementioned embodiment.

[0101] Similarly, the secondary free surface 26 has a plurality of grooves 34 evenly spaced along its periphery. These grooves extend downward from the primary free surface 24 to the base surface 20. Between the grooves 34 are ribs 36, which represent the extension of the primary free surface 24 and contribute to the structural stability of the cutting insert 10.

[0102] The groove 34 may have a constant width, or it may widen toward the base surface 20.

[0103] The difference between the fourth and fifth embodiments is that, in the fifth embodiment, the groove 34 does not taper towards the base surface 20, but rather also exists at the outer edge of the base surface 20. Therefore, it is defined by raised lines.

Claims

1. A positive cutting insert (10) having a chip surface (14), a primary free surface (24), and a secondary free surface (26), wherein a cutting edge (12) is formed between the chip surface (14) and the primary free surface (24), characterized in that, The secondary free surface (26) is offset toward the interior of the cutting blade (10) relative to the primary free surface (24) and is defined on each side in a direction parallel to the cutting edge.

2. The cutting blade (10) according to claim 1, characterized in that, The secondary free surface (26) extends continuously from the first corner free surface (30) to the second corner free surface (30).

3. The cutting blade (10) according to claim 2, characterized in that, The subfree surface (26) is designed to be flat.

4. The cutting blade (10) according to claim 2, characterized in that, The secondary free surface (26) is designed to be wavy, uneven, or concave when viewed along the associated cutting edge (12).

5. The cutting blade (10) according to claim 1, characterized in that, Multiple secondary free surfaces (26) are disposed along one side of the cutting blade (10) between the first corner free surface and the second corner free surface (30).

6. The cutting blade (10) according to claim 5, characterized in that, The secondary free surface (26) is implemented as a groove (34), and the extension of the main free surface (24) extends between the grooves.

7. The cutting blade (10) according to claim 6, characterized in that, The groove (34) gradually tapers toward the base side of the cutting blade (10), so that the base surface (20) has a straight outer edge (38).

8. The cutting part (10) according to claim 7, characterized in that, The groove (34) has a constant width.

9. The cutting insert (10) according to any one of the preceding claims, characterized in that, The cutting blade has a polygonal shape.

10. The cutting insert according to any one of the preceding claims, characterized in that, The cutting blade includes a fastening opening (18) extending through the base surface (20) and through the cutting surface (14).

11. The cutting insert (10) according to any one of claims 1 to 9, characterized in that, The cutting blade has a circular shape including a fastening opening (18) extending through the base surface (20) and through the chip surface (14).

12. The cutting insert (10) according to any one of the preceding claims, characterized in that, The chip surface (14) is arranged concavely adjacent to the cutting edge (12).

13. The cutting insert according to any one of claims 1 to 10, characterized in that, The cutting surface (14) is negative or flat.

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