MACHINING TOOL AND CUTTING INSERTS FOR THE MACHINING TOOL

Description

[0001] The invention relates to a machining tool according to the preamble of claim 1, in particular for wood or wood-like materials, plastics and / or composite materials, and a cutting insert for the machining tool according to the preamble of claim 15. Such a machining tool and such a cutting insert are known from document US3742565 A. State of the art

[0002] When machining materials, especially wood, the general goal is to achieve a smooth surface that requires no rework. To achieve this, the cutting edge geometry of the machining tool must be optimized. However, especially when machining wood or wood-like materials, various adverse effects can be observed that impair the quality of the machined surface. When machining wood, for example, what is known as pre-splitting can occur when a crack precedes the cutting edge in the direction of the grain when a chip is removed. Although this pre-splitting makes machining easier and extends the service life of the cutting edge, it also leads to an undesirably rough surface. In addition, the workpiece fibers can become raised again after cutting if the wood surface is treated with, for example, water-soluble varnishes.

[0003] To achieve the smoothest possible surface, requiring minimal rework, despite these effects, the tool cutting edge must have the smallest possible cutting edge rounding and a small wedge angle. However, the wedge angle, in particular, is subject to the restriction that it must not fall below a certain value for various cutting edge materials. If the wedge angle is too small, the cutting edge will become blunt right from the start of machining, resulting in increased cutting edge rounding and / or chipping at the cutting edge, resulting in the required cutting quality not being achieved.

[0004] In order to ensure a wedge angle that is not too small for wear reasons, while also not too large for high surface quality, cemented carbides are used almost exclusively for the manufacture of cutting edges today. Depending on the application, such cutting edges have wedge angles between 45° and 60°.

[0005] Another factor influencing the machining result is the shear angle. The shear angle is the angle the cutting edge assumes relative to the axis of rotation or its direction of rotation. Using a shear angle creates a so-called "swept" cut because only one point on the cutting edge is used in the surface creation area. This cuts through the wood fibers more smoothly than if no shear angle is set, resulting in an even better surface quality.

[0006] A similar effect to that achieved by using a shear angle can also be achieved with a cambered cutting edge (= cutting edge radius). A comparatively small, unrolled camber of between 0.02 and 0.09 mm is sufficient to achieve the desired effect. Furthermore, the cambered cutting edge produces a significantly better surface quality in the area of the cutting edge overlap.

[0007] The use of replaceable, square cutting inserts with cambered cutting edges and a cutting edge radius ranging between 50 and 150 mm along their length is already known. Such cutting inserts available on the market also feature a wedge angle of 60°. A high wedge angle is particularly desirable because it reduces wear and thus extends the service life of the cutting insert. However, the large wedge angle reduces the usability of the cutting edges on smaller tool diameters. Due to the greater curvature of the cutting circle, cutting edges with a higher clearance angle must be used. Otherwise, undesirable burn marks will appear on the wood surface, and the risk of a workshop fire will increase. The maximum tool diameter for cutting edges with a wedge angle of 60° is therefore approximately 80 mm.With smaller insert diameters, the rake angle becomes too small due to the higher clearance angles, so that optimal machining cannot be achieved.

[0008] FR-A-2702403A1 discloses cutting inserts measuring 14.5 mm x 14.5 mm, which have a chamfer of 1 to 3° to create a crown. The wedge angle of the cutting inserts is between 35 and 40°, and preferably 37°. Compared to the described cutting inserts, standard cutting inserts should have dimensions of 14 mm x 14 mm. It should be noted that according to FR-A-2702403A1, a chamfer is used instead of a cutting edge radius to create the crown. This has the disadvantage that visible streaks may remain when machining wood surfaces, which is aesthetically undesirable.

[0009] US patent application No. US2008050185A1 also describes square cutting inserts with a cutting edge length of 15 mm. The spacing of the cutting edges mounted on a tool is between 0.8 and 0.9 inches (20.32 and 22.86 mm), and the overlap of the cutting inserts is between 0.375 and 0.425 inches (9.52 and 10.8 mm). This means that the cutting edges have an edge length of at least 15 mm. US2008050185A1 does not contain any information about whether the cutting edges are cambered or not.

[0010] EP-A-1 442 852 discloses a cylindrical milling cutter with indexable inserts arranged in rows around the circumference of a roller body with chip grooves. The indexable inserts in consecutive rows are spaced apart. The indexable inserts have a square shape and a slightly curved upper surface. EP-A-1 442 852 does not provide any information on the dimensions of the inserts. Task

[0011] The object of the invention is therefore to propose a machining tool and a cutting insert with which a high surface quality can be produced even with smaller tool diameters in the range of less than 80 mm. A further objective is to provide a machining tool that enables higher performance compared to known machining tools while maintaining otherwise consistent surface quality. Description

[0012] These and other objects are achieved by the subject matter according to claim 1. Advantageous embodiments of the subject matter according to the invention are defined in the subclaims.

[0013] The invention relates to a machining tool for the rotating machining of materials, in particular for wood or wood-like materials, plastics and / or composite materials. The tool has at least one row of individual cutting plates arranged in the circumferential direction, which are essentially square in plan view and have cambered cutting edges, which have a wedge angle and are arranged at an axial angle to the axis of rotation.

[0014] According to the invention, the cutting edges of the square cutting inserts have a length greater than 13 mm and less than 15 mm, a cutting edge radius of less than 50 mm, and a wedge angle of less than 60° and greater than 45°. This cutting edge geometry has the advantage that, by reducing the cutting edge radius while maintaining the same developed crown in the wood, a significantly larger shear angle can be used. Finally, the improved cutting edge geometry is suitable for improved cutting edge positioning and improved cutting angles such as rake, wedge, clearance, and shear angles across the entire diameter range of the tools. Surprisingly, this allows for significantly improved surface quality while maintaining the same tool life. The wedge angle is preferably between 45° and 55°.

[0015] A further advantage is that the smaller wedge angle compared to conventional cutting geometries allows for significantly higher rake and clearance angles. This ensures more optimal machining, less friction, and less heat. To the inventor's surprise, the tool life did not decrease despite the smaller wedge angle.

[0016] Advantageously, the cutting edges of the square inserts have a length greater than 13.5 mm and less than 14 mm, a cutting edge radius of less than 48 mm, and preferably a wedge angle of less than 58°. Lower limits for the wedge angle for inserts with edge lengths between 13 mm and 15 mm are 45°, preferably 48°, and particularly preferably 50°. Due to the shorter cutting edge length and the smaller cutting edge radius, tool diameters significantly smaller than 80 mm can be achieved with the improved cutting edge geometry.

[0017] It has proven particularly advantageous if the cutting edges of the square inserts have a length between 13.7 mm and 13.9 mm, a cutting edge radius of less than 45 mm and preferably equal to or greater than 40 mm, and preferably a wedge angle of less than 54°, preferably approximately 53°. "Approximately" is understood to mean ±0.5 degrees. With inserts whose cutting edge geometry meets the aforementioned criteria, an excellent surface quality can be achieved.

[0018] According to a preferred embodiment, the cutting edge, when projected radially onto a projection plane containing the longitudinal axis of the tool, is inclined at an axial angle of between 18 and 32 degrees, preferably between 20 and 30 degrees, and particularly preferably between 22 and 28 degrees relative to the longitudinal axis of the tool. Setting an axial angle of between 22 and 28 degrees relative to the longitudinal axis of the tool has proven optimal in conjunction with the cutting inserts of the aforementioned cutting geometry.

[0019] According to the invention, at least two rows of cutting inserts are provided in the circumferential direction, with the cutting inserts of the two rows at least partially overlapping when viewed in the direction of rotation of the tool. This has the advantage that the interrupted cut requires less machining power than if the two rows were designed with a single uninterrupted cutting edge.

[0020] The tool preferably has at least one spiral recess with several adjacent seats for receiving cutting inserts. Such an arrangement has proven successful in practice. The distance between two adjacent seats, measured in the axial direction of the tool, is less than twice the cutting edge length of the cutting inserts. This allows a closed cut, similar to that achieved with a continuous cutting insert, to be created using the second row of cutting inserts and a corresponding axial offset of the square cutting inserts.

[0021] A particularly advantageous embodiment of the machining tool provides that one of the two outermost cutting plates is rotated by the axis angle -λ with respect to the longitudinal axis running in the lateral surface, so that the outermost and all subsequent cutting plates 17 pull either outwards or inwards during the cutting process, ie a force component acting outwards or inwards on the wood fibers occurs during cutting.

[0022] The present invention also relates to a substantially square cutting insert for a machining tool for the rotating, machining of materials, in particular for wood or wood-like materials, plastics, and / or composite materials, having a front surface and a cambered rake face, wherein the front surface forms an obtuse angle with the cambered rake face. The cutting insert according to the invention is characterized in that the cutting edges of the square cutting inserts have a length greater than 13 mm and less than 15 mm, a cutting edge radius of less than 50 mm, and a wedge angle of less than 60° and greater than 45°. The advantages of a cutting insert with such a cutting geometry have already been discussed above.

[0023] A further object of the present invention is a system comprising a tool for the rotary machining of materials such as wood or wood-like materials, plastics and / or composite materials and a cutting insert according to claims 11 to 14.

[0024] Embodiments of the invention will now be described in more detail with reference to the accompanying figures. Fig. 1A side view of a first embodiment of a machining tool according to the invention for the rotary machining of a workpiece with a plurality of cutting plates arranged in a spiral recess; Fig. 2A front view of the embodiment of Fig. 1 ; Fig. 3A cutting plate according to the invention in a bottom view and in section; Fig. 4Schematic of the cutting plate of Fig. 3when positioned tangentially on the circumference of a cylindrical machining tool; Fig. 5 Schematically the cutting insert of Fig. 3 , when it is tilted by the clearance angle α on the circumference of the machining tool; Fig. 6 Schematic of the geometric positioning of the cutting insert on a cylindrical machining tool; Fig. 7 Schematic of a second embodiment of a cylindrical machining tool for rebating with rows of cutting inserts arranged one behind the other, wherein half of the outer surface is shown as a developed surface for better illustration; Fig. 8 Schematic of a third embodiment of a machining tool for grooving; Fig. 9 Schematic of a fourth embodiment of a machining tool for joining.

[0025] The Figures 1 and 2show a perspective view of a first embodiment of a machining tool 11 according to the invention for the machining of materials, in particular for wood or wood-like materials such as coated or uncoated chipboard, hardboard or the like. However, the machining tool 11 can also be suitable for other materials such as fiber-reinforced plastics or the like. The machining tool 11 is designed as a spiral milling cutter and is intended for mounting on a tool shank (not shown). During operation, the machining tool 11 is driven to rotate about a rotational axis 12 ( Fig. 1 ).

[0026] The base body 13 of the machining tool 11 is essentially cylindrical, with a plurality of cutting plates 17 designed as circumferential cutting edges 19 arranged on its cylindrical circumferential surface 15. The cutting plates 17 are arranged in at least one, preferably in at least two or more rows arranged in the circumferential direction, with these individual rows or groups overlapping one another in the axial direction in order to achieve a uniform machining result.

[0027] In the Fig. 1In the illustrated machining tool 11 according to the invention, a spiral, semicircular, or U-shaped chip channel 21 is formed in the peripheral surface 15 adjacent to a likewise spiral-shaped recess 23. Several insert seats 25 are arranged at a distance from one another in the spiral-shaped recess 23. A screw channel 27 for receiving a fastening screw 29 is provided in the center of each insert seat 25.

[0028] In Fig. 3On the right, a bottom view of the cutting plate 17 is shown, and on the left, the cutting plate 17 is shown in section. The cutting plate 17 has a substantially square outline with edge length I, a flat front surface 31 and a smaller and also flat support surface 33. Between the front surface 31 and the support surface 33, a cutting wedge with the cutting edges 19 and the wedge angle β is formed on each of the side edges. The reference number 35 designates the cambered rake face, and the front surface 31 is the flank face. As can be seen from the inventive Fig. 3As can be seen, the cutting edges 19 are not straight, but cambered, ie, formed with a specific cutting edge radius, which is preferably less than 45 mm. In the center of the cutting insert 17 there is a conical receiving hole 37, which serves to receive the head of the fastening screw 29. If a cutting insert with cambered cutting edges is viewed from the side in a direction that lies in the plane of the front surface, the cambered cutting edge is perceived as a straight line ( Fig. 4 ). However, as soon as the cutting edge is tilted by a clearance angle α, the cambered cutting edge 19 appears as an elliptical development with a certain residual camber 39, which is smaller than the actual camber of the cutting edge ( Fig. 5 ). If the cutting plate were tilted by 90° (viewing angle perpendicular to the front surface as in Fig. 3), then the full crowning 38 would be visible. For the design of the machining tool, this means that a desired, optimal residual crowning can be set by a corresponding inclination of the insert seat relative to the circumferential surface.

[0029] In Fig. 6 The arrangement of the cutting plate 17 on a cylindrical tool 11 is shown as an example. As can be seen from the Fig. 6As can be seen, the cutting insert 17 is tilted by a clearance angle α relative to a tangent 41 applied to the tool circumference. According to the exemplary embodiment, the cutting insert is rotated in the clearance angle plane by the axial angle λ into the milled spiral groove 23, and the two corner points of the cutting edge (intersection points of the cambered cutting edges) are simultaneously tilted by a plane angle ε so that they again lie on the same "line" or cutting circle. For a cylindrical tool, this "line" is the same cutting circle diameter, and for a conical tool, the corner points of the cutting edge lie on the corresponding "chamfer angle line" of the tool.

[0030] Fig. 7shows an example of a machining tool 11a according to the invention, as it can be used for rebating a wooden workpiece. For better illustration, one half of the cylinder surface is shown as a developed surface, ie spread out in the plane. The machining tool has two rows 43, 45 of cutting plates 17 arranged one behind the other in the circumferential direction, which, as can be seen from Fig. 7As can be seen, they are arranged offset from one another. By turning the cutting edge by the axial angle and by freeing the cutting edge by tilting it by the clearance angle, a triangular "dead" area 47 is created on one side of the cutting edge, i.e., an area of the cutting edge that is not involved in the current machining process. The rebating machining tool 11a is wider by a "dead" area 47 than the maximum rebating depth; otherwise, the uppermost cutting insert 17 of the second row 45 would protrude beyond the tool body. The direction of rotation arrow 49 indicates the direction of rotation, and λ denotes the axial angle.

[0031] In Fig. 8 A machining tool specifically designed for grooving is shown.

[0032] The special feature of this machining tool 11b is that the cutting inserts 17 are divided and arranged in such a way that there is no "dead" area on either side of the body. This can be achieved by placing additional pre-cutters on both sides, so that the milling cutter can also be used as a "grooving cutter." According to the exemplary embodiment, the grooving tool 11b has a first row 43 with four cutting inserts 17 and a second row 45 with three cutting inserts 17. The cutting insert of the first row is rotated by the axial angle λ with respect to the longitudinal axis such that the first and all subsequent cutting inserts 17 extend outwards during the cutting process.

[0033] In Fig. 9 a machining tool 11 is shown which can be used specifically for joining and which is comparable to that of Fig. 1is identical. The special feature of this machining tool is that the cutting inserts are rotated by the axial angle λ with respect to the longitudinal axis in such a way that at least one cutting edge on both sides of the body is pulled "inward" by 17' or 17", thus pushing the wood fibers toward the workpiece being machined. This creates a tear-free cutting edge on both sides. This special cutting edge arrangement and the release of the cutting edge by tilting it by the clearance angle creates a triangular "dead" area above or below the cutting edge, i.e., an area of the cutting edge that is not involved in the current machining process. To prevent the cutting edge from protruding laterally from the tool, the tool must be widened by at least this amount to prevent the risk of injury to the user and to protect the cutting edge from damage.

[0034] In summary, the following can be stated: The cutting insert has, for example, a trapezoidal cross-section with a wedge angle β formed at the cutting edge, wherein the wedge angle β is enclosed by a cambered rake face and a clearance face of the cutting edge. The wedge angle β is supplemented by a clearance angle α and a rake angle γ, totaling 90°. According to the invention, the wedge angle β is < 60° and lies in a range between 45° and 58°, preferably between 52° and 54°, preferably approximately 53°. The improved cutting edge geometry enables machining tools with smaller diameters to be realized. legend

[0035] 11 Machining tool 12 Rotary axis 13 Base body 15 Circumferential surface 17 Insert 19 Cutting edge of the insert 21 Chip channel 23 Spiral groove 25 Insert seat 27 Screw channel 29 Fastening screw 31 Front surface or clearance angle surface 33 Support surface 35 Crowned rake surface 37 Locating hole 38 Full crown 39 Residual crown 41 Tangent 42 Wood workpiece 43, 45 Rows of inserts 47 "Dead" area 49 Direction of rotation arrow

Claims

1. A machining tool (11, 11a, 11b) for rotatively machining materials (42), particularly for wood or wood-like materials, plastics and / or composite materials, characterized in that the machining tool is also designed with a spiral-shaped, semicircular or U-shaped chip channel (21), an adjacent spiral-shaped depression (23) with several adjacently arranged seats (25) for receiving cutting plates and, arranged thereon in the circumferential direction, a row of individual cutting plates (17) that essentially are square in a top view and have cambered cutting edges (19), with said cutting edges having a wedge angle and being arranged at an axial angle λ to the rotational axis (12), wherein the cutting edges (19) of the square cutting plates (17) have a length that is greater than 13 mm and smaller than 15 mm, a cutting edge radius that is smaller than 50 mm and a wedge angle β that is greater than 45° and smaller than 60°.

2. The tool according to claim 1, characterized in that the cutting edges (19) of the square cutting plates have a length that is greater than 13.5 mm and smaller than 14 mm and a cutting edge radius that is smaller than 48 mm.

3. The tool according to claim 1, characterized in that the cutting edges (19) of the square cutting plates have a length between 13.7 mm and 13.9 mm, a cutting edge radius that is smaller than 45 mm and a wedge angle β that is smaller than 54°.

4. The tool according to one of claims 1 to 3, characterized in that the wedge angle β is ≥ 48°, particularly ≥ 52°.

5. The tool according to claim 1, characterized in that the cutting plate (17) particularly has a length of 13.8 mm, a cutting edge radius of 40 mm and a wedge angle β of 53°.

6. The tool according to one of claims 1 to 5, characterized in that the cutting edge (19) is inclined relative to the longitudinal tool axis by an axial angle λ between 18 and 32 degrees in a radial projection on a projection plane containing the longitudinal axis of the tool.

7. The tool according to one of claims 1 to 6, characterized in that the cutting edge (19) is inclined relative to the longitudinal tool axis by an axial angle λ between 20 and 30 degrees in a radial projection on a projection plane containing the longitudinal axis of the tool.

8. The tool according to one of claims 1 to 7, characterized in that the cutting edge (19) is inclined relative to the longitudinal tool axis by an axial angle λ between 22 and 28 degrees in a radial projection on a projection plane containing the longitudinal axis of the tool.

9. The tool according to one of claims 1 to 8, characterized in that the cutting plate (17) assumes such a plane angle ε that the opposing corner points of the cutting edge (19) lie on the same cutting circle radius.

10. The tool according to one of claims 1 to 9, characterized in that at least two rows (43, 45) of cutting plates (17) are provided in the circumferential direction, wherein the cutting plates of the two rows (43, 45) overlap at least partially.

11. The tool according to one of claims 1 to 10, characterized in that a screw channel (27) for receiving a fastening screw (29) is provided in the center of each seat (25) and a conical receiving hole (37) for the head of the fastening screw (29) is provided in the center of the cutting plate (17).

12. The tool according to one of claims 1 to 11, characterized in that the distance between two adjacent seats measured in the axial direction of the tool is smaller than twice the cutting edge length of the cutting plates.

13. The tool according to one of claims 1 to 12, characterized in that the tool diameter is smaller than 80 mm.

14. The tool according to one of claims 1 to 13, characterized in that a semicircular or U-shaped chip channel (21) is formed adjacent to the spiral-shaped depression (23).

15. A cutting plate (17) for a machining tool for rotatively machining materials (42), particularly for wood or wood-like materials, plastics and / or composite materials, wherein said cutting plate has a front face (31) and a cambered cutting face (35), wherein the front face (31) forms an obtuse angle with the cambered cutting face (35), and wherein a conical receiving hole (37) for the head of a fastening screw (29) is provided in the center of the cutting plate (17), characterized in that the cutting edges (19) of the square cutting plates (19) have a length that is greater than 13 mm and smaller than 15 mm, a cutting edge radius that is smaller than 50 mm and a wedge angle β that is greater than 45° and smaller than 60°.

16. The cutting plate according to claim 15, characterized in that the cutting edges (19) of the square cutting plates have a length that is greater than 13.5 mm and smaller than 14 mm and a cutting edge radius that is smaller than 48 mm.

17. The cutting plate according to claim 15, characterized in that the cutting edges (19) of the square cutting plates (17) have a length between 13.7 mm and 13.9 mm, a cutting edge radius that is smaller than 45 mm and a wedge angle β that is smaller than 54°.

18. The cutting plate according to one of claims 15 to 17, characterized in that the wedge angle β is ≥ 48°, particularly ≥ 52°.

19. The cutting plate according to claim 18, characterized in that the cutting plate (17) particularly has a length of 13.8 mm, a cutting edge radius of 40 mm and a wedge angle β of 53°.

20. A tool system comprising a tool according to one of claims 1 to 14 and a cutting plate according to one of claims 15 to 19.