Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23C—MILLING
  • B23C5/00—Milling-cutters
  • B23C5/02—Milling-cutters characterised by the shape of the cutter
  • B23C5/10—Shank-type cutters, i.e. with an integral shaft
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23C—MILLING
  • B23C5/00—Milling-cutters
  • B23C5/16—Milling-cutters characterised by physical features other than shape
  • B23C5/165—Milling-cutters characterised by physical features other than shape with chipbreaking or chipdividing equipment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23C—MILLING
  • B23C2210/00—Details of milling cutters
  • B23C2210/04—Angles
  • B23C2210/0407—Cutting angles
  • B23C2210/0442—Cutting angles positive
  • B23C2210/0457—Cutting angles positive radial rake angle
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23C—MILLING
  • B23C2210/00—Details of milling cutters
  • B23C2210/32—Details of teeth
  • B23C2210/326—File like cutting teeth, e.g. the teeth of cutting burrs
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23C—MILLING
  • B23C2210/00—Details of milling cutters
  • B23C2210/48—Chip breakers
  • B23C2210/486—Chip breaking grooves or depressions

Definitions

• the invention relates to a burr according to the preamble of claim 1.
• burrs are also known as rotary files (in English: bur or burr). According to the definition in DIN 8032/8033 and ANSI, they are used both in hand-held and automated tools, each with an electric motor or pneumatically driven tool, and are used for manual and automatic (including robot guidance) grinding of metal surfaces through fine material removal used.
• Known burrs for the aforementioned purpose have a shaft section and a milling section that adjoins the shaft section and ends in a free milling tip. At least the milling section consists of flart metal, for example tungsten carbide.
• the shaft section and the milling section are designed to be rotationally symmetrical to an axis of rotation.
• the milling section has a milling length and has a plurality of cutting edges which are separated ge by spaced Flauptnuten.
• a usual number of flake grooves in known burrs with a diameter of 12.7 mm (1/2 ") is, for example, 24.
• the flake grooves have a groove depth, hereinafter referred to as the flake groove depth, and extend helically in a first helix direction with a first helix angle of the milling section.
• Each of the cutting edges here has a rake face and a free face as well as a cutting edge at the transition between the rake face and the free face with the formation of a rake angle and a clearance angle.
• the first helix angle is measured between a tangent applied to the cutting edge and a line parallel to the axis of rotation.
• a plurality of chip breakers is provided in each flank.
• the chip breakers have a depth, which is referred to below as the chip breaker depth, and are in a helical shape second twist direction with a second twist angle along the Fräsab extend section.
• the second helix angle is measured between a tangent to the connecting line between adjacent but mutually offset chip breakers provided in successive open spaces and the parallels mentioned to the axis of rotation.
• the first twist direction runs in the direction of rotation of the burr, while the second twist direction can be opposite to the first twist direction and thus also against the direction of rotation of the burr; the second helix angle is then negative.
• the second twist direction can also run in the direction of rotation of the burr, the second twist angle then being positive.
• the function of the chip breaker is on the one hand to control chip formation and on the other hand to reduce the cutting resistance. If the chips can be broken into a convenient length, they will not wrap around the workpiece, vibration is suppressed and the chances of damage to the burr are reduced. A low cutting resistance prevents the cutting edge from breaking prematurely due to vibrations. A low cutting resistance also helps to reduce the load and the generation of heat and can delay wear.
• burrs of the aforementioned type have the disadvantage that their cutting performance can hardly be increased without shortening their service life too much.
• no burrs have become known that offer an optimal balance between good milling performance and a long service life.
• a burr according to the invention is generally designed in accordance with DIN 8032/8033 and ANSI standard.
• the milling bit according to the invention with its milling section made of flart metal is particularly adapted to the machining of steel surfaces.
• the term “in the area of the milling section with the largest diameter” is used, so that a uniform reference point is given even with different geometries of the milling bits according to the invention.
• the features according to the invention can be identified in both a cylindrical and a spherical milling section.
• the term “base body of the milling section” could be chosen, in particular to distinguish it from the area of the milling tip.
• the chip breaker depth of a milling bit according to the invention is in the region of the milling section with the largest diameter between 5 and 25% of the flaunt groove depth.
• Such a chip breaker depth is much less than is known from the prior art.
• a relatively small chip breaker width (measured along the cutting edge) is associated with a small chip breaker depth due to the manufacturing process.
• the technical effect achieved by these features is that a greater linear length of the main grooves is achieved compared to the known deeper and broader chipbreaker depths.
• chip breaker depths of up to 80% of the main groove depths are known.
• the clearance angle in the region of the milling section with the largest diameter is between 10 ° and 20 °. This will - in conjunction with the other features of the invention - it is enough that the cutting edges are more resistant and are therefore subject to ge lower wear.
• the rake angle is in the area of the Fräsab section with the largest diameter between -3 ° and + 14 °. It has been found that this rake angle, which is selected to be relatively small compared to known burrs, contributes to achieving good cutting performance and low wear.
• the first twist angle is greater than 25 °.
• a relatively large helix angle also allows more cutting edges to come into contact with the workpiece. In this way, the load on the cutting edges can be reduced; the surface quality of the workpiece is also improved.
• Another measure according to the invention is that the number of main grooves is less than 15 and preferably not more than twelve. This also results in a high cutting performance, with the interplay of all the features of claim 1, the wear of the Fräsab section is surprisingly very low, which is at least partially achieved by the increased strength of the main grooves.
• an important feature of the inventive burr is that its chip breakers have a very small depth (and thus also width) compared to known burrs, the purpose of the chip breaker, ie the crushing of the chips during the grinding process, being retained .
• the linear length of the available cutting edge is maximized due to the shallow depth and the associated manufacturing-related narrow width of the chip breaker.
• the chip breaker depth in the region of the milling section with the largest diameter is between 10% and 20% of the main groove depth.
• the chip breaker depth in the region of the milling section with the largest diameter is preferably between 0.1 and 0.25 mm and is particularly preferably not greater than 0.2 mm.
• the chip breaker depth is in the range between 10% and 20% of the main groove depth, as a reference, then the main groove depth is between 0.5 mm and 2.5 mm, and preferably no greater than 20 mm.
• the chip breaker depth can be 0.1 mm in the case of a main groove depth of 1 mm.
• the chip breaker depth is 0.2 mm in the case of a main groove depth of 2 mm.
• the chip breaker depth in the area of the milling section with the largest diameter is advantageously not greater than the maximum width of the chip breaker (chip breaker width), measured along the cutting edge. Before given to the chip breaker width is, for example, twice as large as the chip breaker depth. Such a ratio of chip breaker width to chip breaker depth is achieved, for example, when a chip breaker wheel with a 90 ° angle is used.
• the chip breakers are particularly preferably placed completely in the flank, so they do not protrude into the main groove facing away from the direction of rotation or the subsequent chip space.
• All chip breakers are preferably at a distance from the transition between the shank section and the milling section and / or the milling tip. This distance is for example and preferably at least 1 mm. This ensures that there is no weak point on the cutting edges which could break off if the distance between the chip breaker and the shank section or the milling tip is too small.
• the clearance angle in the region of the milling section with the largest diameter is between 12 ° and 18 °, particularly preferably between 13 ° and 15 °.
• the free areas in the region of the milling section with the largest diameter have a width, measured in the direction of rotation of the milling pin, of 0.2 mm to 1 mm, preferably 0.4 to 0.8 mm.
• the said open area which begins directly at the respective cutting edge and runs counter to the direction of rotation of the burr, the only open area produced when the flake grooves are cleared.
• This open space is also called “primary relief” in English.
• a further open area (“secondary relief”) therefore does not adjoin the said open area (primary relief) - contrary to the direction of rotation of the burr. Rather, immediately after the (first) flank, the flake groove begins with the corresponding chip space.
• this design facilitates the clearing position of the cutting edges or fluted grooves; on the other hand, it has not proven beneficial to provide an additional open area.
• the first twist angle is selected to be larger and, in this case, preferably larger than 27.5 °.
• the first twist angle is particularly preferably in the range between 29 ° and 32 °, and very particularly preferably 30 °.
• the second helix angle ie the slope angle formed by the chip breakers, preferably has a smaller slope than the first helix angle. It has proven to be advantageous if this is in the range between -75 ° and -88 °, preferably between -78 ° and -85 °, and particularly preferably between -80 ° and -82 °.
• the second helix angle can be chosen to be positive and is then preferably between + 75 ° and + 88 °, preferably between + 78 ° and + 85 °, and particularly preferably between + 80 ° and + 82 °.
• the first helix angle of all cutting edges and main grooves is preferably the same.
• first helix angle is also preferably constant along the milling length. It is also preferred if the second twist angle for the chip breaker is constant.
• variable first and / or second helix angles are possible.
• Variable first helix angles can be implemented e.g. for one or more individual main grooves and / or between different main grooves.
• a variable second helix angle a possible embodiment can, for example, have a slope that increases from the shank to the milling tip.
• Other embodiments with regard to a variable second twist angle are possible without restriction.
• burrs according to the invention with a radius at the milling tip (where, for example, burrs with a cylindrical milling section are not included)
• the two cutting edges of at least one pair of cutting edges which run on opposite sides of the milling section, merge into one another at the milling tip.
• at least two cutting edges form a common cutting edge on the milling tip.
• These two cutting edges of said at least one pair preferably form an S-shape when viewed from above on the milling tip. This can increase the stability of the milling tip. It is also possible - to a limited extent - to carry out cutting or drilling operations with the milling tip.
• the number of main grooves is less than or equal to the largest diameter, measured in mm, of the milling section. Accordingly, it has turned out to be positive with regard to the machining result - with little wear - that
• the number of main grooves is 5 to 7, preferably 6,
• the number of main grooves is 7 to 9, preferably 8,
• the number of main grooves is 9 to 11, preferably 8,
• the number of main grooves is 9 to 11, preferably 10, and / or
• the number of main grooves 11 to 13, preferably 12, is.
• a preferred lower limit of a specified pair of values with the upper limit of another specified pair of values can represent a further advantageous range. It is possible, for example, that a preferred chip breaker depth is between 5% (claim 1) and 20% (claim 2) of the main groove depth.
• the milling sections of the burrs according to the invention can be provided with various coatings that contribute to a reduction in wear and an increase in service life.
• Such special coatings can consist of TiN, TiAIN, AITiN, DLC, CH-NFE and CH-FEP, for example.
• FIG. 1 shows a side view of a burr according to the invention
• Fig. 2 is a cross-sectional view taken along A-A in Fig. 1;
• FIG. 3 shows an enlarged detail of FIG. 2;
• FIG. 4 shows a cross-sectional view of a detail similar to FIG. 3, but here running through a chip breaker
• FIGS. 1-6 A first embodiment of a burr 1 according to the invention is shown in FIGS. 1-6.
• a burr 1 has a cylindrical shank section 2 and a substantially conical, circumferentially outwardly curved, Fräsab section 4, the latter having a milling length f and ending in a milling tip 6.
• the shaft section 2 is used for fastening in a manually or automatically operated tool that the shaft section 2 and thus the entire burr 1 set in a direction of rotation 9 in rotation in order to grind a metal workpiece.
• the shaft section 2 and the milling section 4 are designed to be rotationally symmetrical to an axis of rotation 8.
• At least the milling section 4 consists of hard metal.
• the shaft section 2 can also - which is also preferred - consist of hard metal and is then preferably formed in one piece with the milling section 4; alternatively, the shank section 2 is made of steel, the shank section 2 then being connected to the milling section 4, for example by soldering.
• the milling section 4 can have different geometries. Instead of a substantially conical or conical cross section, the Fräsab section 4 can be designed with a constant or spherical cross section. Many other forms are possible, as well as mixed forms, all of which are known to the person skilled in the art.
• cutting 10 and main grooves 14 alternate in the direction of rotation 9 of the burr 1, these cutting edges 10 and main grooves 14 along the milling section 4, seen in the direction of the milling tip 6, in a first helical direction 16 in a helical shape with a first constant here Twist angle a of 30 ° (see Fig. 1).
• the first helix angle a is - in the Be rich of the milling section 4 with the largest diameter, here in the Be rich of the transition from the milling section 4 to the shaft section 2 - between a tangent applied to the cutting edge 12 (see below) of a cutting edge 10 and a parallel to the axis of rotation 8 measured.
• the first twist direction 16 runs in the direction of rotation 9.
• the number of main grooves 14 is chosen to be low and is less than 15. In the illustrated embodiment, ten main grooves 14 and thus also ten cutting edges 10 are present (see FIG. 2).
• the first twist angle ⁇ is greater than 25 °, preferably greater than 27.5 ° and is preferably in the range between 29 ° and 32 °.
• a particularly preferred embodiment is shown in the figures, in which the first twist angle ⁇ is a constant 30 °.
• the at least two successive cutting edges 10 have a first helix angle a that is different from one another, for example with a first helix angle a that differs from one another by 0.5 °, 1 ° or 2 °.
• each of the cutting edges 10 has a cutting edge 12.
• a rake face 20 which forms a rake angle g with a straight line perpendicular to and through the axis of rotation 8 of the burr 1 (see FIG. 3).
• a free surface 24 in English: primary relief
• a further open area in English: secondary re Ran, which would adjoin said first open area 24 against the direction of rotation 9, is not provided and is generally not preferred.
• the rake angle g is approx. + 7 ° and is preferably generally in the range between -3 ° and + 14 °, preferably between 0 ° and + 12 ° and particularly preferably in the range between +5 ° and + 10 °.
• variable rake angles are also possible. Such variable rake angles can be implemented for one or more individual cutting edges and / or between different cutting edges.
• the clearance angle d is approx. 15 ° and, according to the invention, generally in the range between 10 ' and 20 °, preferably between 12 ° and 18 ° and particularly preferably between 13 ° and 15 °.
• the free surface 24 preferably has a width I, measured in the direction of rotation 9 of the burr 1, from 0.2 mm to 1 mm, preferably from 0.4 to 0.8 mm.
• the rake angle g of the cutting edges 10 at the milling tip 6 is preferably between -3 ° and 0 °.
• Milling bits without a defined face radius have, for example, a cylindrical or conical milling section.
• chip breakers 30 in English: Chip breaker are seen along their course in the first twist direction 16.
• the chip breakers 30 each have a chip breaker depth s which, according to the invention, is small compared to the main groove depth h (see Fig.
• the chip breakers 30 of adjacent cutting edges 10 follow one another in the form of a helix which is opposite in a second twist direction 32, which is opposite to the first twist direction 16 and thus also the direction of rotation 9.
• the second helix angle ⁇ is measured between a tangent to a connecting line between adjacent chip breakers 30 provided in successive free areas 24 but offset at an angle to one another and a parallel line to the axis of rotation 8.
• the second twist angle formed in this way ß is, as in the illustrated embodiment, preferably con stant.
• the chip breaker depth s mentioned is in the range between 5 and 25% of the flute depth h, preferably in the range between 10% and 20% of the flute depth h. It has been found that such a chip breaker depth, which is small in relation to the main groove depth h, has great advantages with regard to the effective cutting length of the cutting edges 10, the longevity he increases or the wear of the cutting edges 10 is reduced and yet the Main task of the chip breaker 30 effectively done, namely to improve the chip control and at the same time reduce the cutting resistance.
• the chip breaker depth s is approximately 17% of the main groove depth h.
• the chip breaker depth s is preferably in the range between 0.1 and 0.25 mm.
• the chip breaker depth s is 0.1 mm with a main groove depth h of 1 mm.
• the chip breaker depth s is 0.2 mm with a main groove depth h of 2 mm.
• the chip breaker depth s is 10% of the main groove depth h. According to the percent ranges given above, however, it is also easily possible if the chip breaker depth s is 0.2 mm with a main groove depth h of 1 mm, ie the ratio of the two depths is 20%.
• the chip breaker width b (see FIG. 5), which is related to the chip breaker depth s due to the production of the chip breaker 30 by means of cutting wheels known per se, is preferably greater than the chip breaker depth s and, for example, twice as large.
• the chip breaker depth s can be, for example, 0.2 mm and the chip breaker width b, for example, 0.4 mm.
• the number of chip breakers 30 along a cutting edge 12 is dependent on the milling length f, the diameter of the milling section 4 and / or the number of cutting edges 10.
• the number of chip breakers 30 along a cutting edge 10 is, for example, between four and eight, for example five or six. In the illustrated embodiment, five chip breakers 30 are provided per cutting edge 10. It is particularly advantageous if the chip breakers 30 run completely in the respective free surface 24 or are embedded in it, as can be seen in the perspective sectional view of FIG.
• chip breakers 30 have a distance a from the boundary area between the milling section 4 and the shank section 2 (see FIG. 1), this distance a preferably being at least 1 mm. It is also preferred if there is a corresponding distance from the chip breaker 30 to the milling tip 6 (not shown, but recognizable in FIG. 6). Both measures serve to ensure that the effective length of a cutting edge 12 between a chip breaker 30 and the freely tapering end of the cutting edge 12 does not become too small, so that the risk of breaking this cutting edge section when grinding or milling a workpiece does not increase significantly.
• Said second helix angle ⁇ which is formed by the chip breakers 30, which are seen in the opposite direction of rotation 9 successive cutting edges 10 and which run helically on the milling section 4, is approximately -81 ° in the embodiment shown in the figures, and generally advantageously in the range between -75 ° and -88 °, preferably between -78 ° and -85 ° and particularly preferably between -80 ° and -82 °.
• the second twist angle ß is negative; but it can also be positive and advantageously between + 75 ° and + 88 °, preferably between + 78 ° and + 85 °, and particularly preferably between + 80 ° and + 82 °.
• the first twist direction 16 and the second twist direction 32 then both run in the direction of rotation 9.
• the number of fluff grooves 14 is selected to be relatively small. In the exemplary embodiment shown in the figures, as stated above, ten Flauptnuten 14 and ten cutting edges 10 are present. It has proven to be advantageous if the number of Flauptnuten 14 is less than or equal to the maximum diameter of the milling section 4, measured in mm.
• the values given for the embodiment shown in the figures relate to the area of the milling section 4 with the largest diameter, ie the present Area of the transition between the milling section 4 to the shaft section 2.
• a uniform reference point is specified, which also applies to milling sections 4 with a different geometry (for example, spherical head-shaped).
• the designation “base body of the milling section 4” could be chosen, in particular to distinguish it from the area of the milling tip 6.

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• 2020
  • 2020-03-06 DE DE102020106105.6A patent/DE102020106105A1/de active Pending
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  • 2021-03-05 EP EP21710454.6A patent/EP4110542B1/de active Active
  • 2021-03-05 ES ES21710454T patent/ES3011271T3/es active Active
  • 2021-03-05 US US17/909,453 patent/US12496644B2/en active Active
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