END MILLS

Description

[0001] The invention relates to an end mill for milling composite materials, e.g. fiber-reinforced plastics (FRP) such as carbon- or glass-fiber-reinforced plastics (CFRP / GFRP).

[0002] Fiber-reinforced plastics are relatively difficult to machine due to their multi-phase structure. For example, when milling a fiber-reinforced plastic sheet, delamination of fiber-reinforced plastic layers or fiber protrusions on the two sheet surfaces are often observed. Therefore, cost-effective machining of modern fiber-reinforced plastics, especially in series production, requires a customized tool design that reliably prevents delamination or fiber protrusions on a machined fiber-reinforced plastic component. Examples of the aforementioned tools with customized tool designs include end mills, which are designed as compression cutters, in which a special cutting part design generates opposing axial cutting forces.At the point where the fibers of a milled FRP material, which are traditionally created by these cutting forces, meet, these fibers are compressed and ultimately separated. This prevents delamination or fiber protrusions on the two sheet surfaces.

[0003] For example, DE 102006022572 A1 describes an end mill with a shank and a cutting part axially adjoining the shank, which has an even number of, for example, four cutting edges, which are circumferentially spaced from one another by grooves and each have a plurality of circumferential cutting edges with a left-hand or right-hand helix. To address the problems mentioned above, it is proposed that the helix direction of the circumferential cutting edges of cutting edges immediately following one another in the circumferential direction be reversed from left to right or right to left. The cutting forces occurring during milling of a fiber-reinforced plastic material at two cutting edges immediately following one another in the circumferential direction therefore generate opposing axial forces, which lead to compression of the fiber composite layers of the fiber-reinforced plastic material.If a FRP plate is milled, it can be achieved that fiber composite layers adjacent to the two plate surfaces or fibers protruding from the FRP material are reliably separated.

[0004] From WO 2017 / 134011 A1 or US Pat. No. 9,174,287 B2, for example, the skilled person knows an end mill that has a cutting part adjoining a shank with circumferential cutting edges that are left- and right-handed with respect to the rotational axis of the end mill, which are divided into segments by intersecting left- and right-handed flutes. The left- and right-handed flutes extend with a constant flute cross-section across a cutting zone in the cutting part or from a front end to a shank end of the cutting part.

[0005] In contrast, US 3,913,196 or US 2013 / 0294852 A1 shows and describes a right-cutting end mill with a shank and a cutting part adjoining the shank, which cutting part extends from a shank-side end to a front end and, in a front longitudinal region which extends from the front end to a transition point in the central region of the cutting part, a plurality of right-handed helix (i.e. running with a positive helix angle) first circumferential cutting edges, each adjoining a right-handed first groove (chip groove), and, in a rear longitudinal region which extends from the above-mentioned transition point in the central region of the cutting part to the shank-side end of the cutting part, a plurality of left-handed helix (i.e. running with a negative helix angle) second circumferential cutting edges, each adjoining a left-handed second groove (chip groove).Due to the opposing helix direction of the first and second circumferential cutting edges in the front and rear length regions of the cutting part, the cutting forces occurring during milling of a fiber-reinforced plastic (FRP) material result in opposing axial forces that cause compression of the FRP material. Due to the distribution of the first and second circumferential cutting edges between the front and rear length regions of the cutting part, the total result is a pulling cut in the front length region, through which fiber composite layers or fibers are pulled toward the shaft end of the cutting part, and a pushing or pushing cut in the rear length region, through which fiber composite layers or fibers are pushed or pressed toward the front end of the cutting part.The opposing axial forces prevent delamination of fiber composite layers or fiber protrusions on the two surfaces of a milled FRP sheet. However, since the first and second peripheral cutting edges are individually ground into the front and rear longitudinal sections of the cutting part, respectively, the formation of the cutting part and thus the end mill as a whole is relatively difficult and time-consuming.

[0006] The document CN 104 191 020 A discloses an end mill according to the preamble of claim 1.

[0007] Starting from an end mill as known from CN 104 191 020 A, the invention is therefore based on the object of creating an end mill designed as a compression mill, with which a high surface quality can be achieved when milling a composite material and which is easier to manufacture.

[0008] This object is achieved by an end mill having the features of claim 1. Advantageous or preferred developments are the subject of dependent claims.

[0009] An end mill according to the invention for milling composite materials, e.g., fiber-reinforced plastics (FRP), has a defined cutting or rotation direction, i.e., it is designed for either right-hand cutting / right-hand rotation or left-hand cutting / left-hand rotation. The end mill, which extends along a longitudinal center or rotational axis, can be functionally divided into a shank that can be clamped in a chuck and a cutting part. The cutting part can be connected to the shank directly axially or indirectly via a non-cutting connecting part.The cutting part extends from a shaft end to a front end and has, in a front / front length region adjacent to the front end, exclusively or at least almost exclusively a plurality of first circumferential cutting edges running with a positive helix angle, each adjacent to a first groove running with a positive helix angle, and, in a shaft / rear length region adjacent to the shaft end, exclusively or at least almost exclusively a plurality of second circumferential cutting edges running with a negative helix angle, each adjacent to a second groove running with a negative helix angle.

[0010] The sign of the helix angle (positive or negative) or the helix direction (positive or negative) of the peripheral cutting edges and grooves is uniquely determined by the cutting direction / rotation of the end mill. For a right-cutting / right-rotating end mill, right-handed / right-threaded peripheral cutting edges / grooves have a positive helix angle, and left-handed / left-threaded peripheral cutting edges / grooves have a negative helix angle. Conversely, for a left-cutting / left-rotating end mill, left-handed / left-threaded peripheral cutting edges / grooves have a positive helix angle, and right-handed / right-threaded peripheral cutting edges / grooves have a negative helix angle.A peripheral cutting edge with a positive helix angle generates an axial cutting force toward the shank end of the cutting part and performs a pulling cut, while a peripheral cutting edge with a negative helix angle generates a cutting force toward the front end of the cutting part and performs a pushing cut. An end mill according to the invention can therefore be used as a compression mill.

[0011] The inventive design achieves an almost exclusively pulling cut in the front longitudinal section of the cutting part and an almost exclusively pushing or pushing cut in the rear longitudinal section of the cutting part. When milling a fiber-reinforced plastic (FRP) plate, opposing axial forces are therefore achieved, which cause compression of the FRP material and prevent delamination and fiber protrusion on both surfaces of the FRP plate.

[0012] Each peripheral cutting edge forms a cutting wedge in cross-section, as is known to those skilled in the art, which is clearly defined by a wedge angle, clearance angle, and rake angle. Viewed in the direction of extension, each peripheral cutting edge extends from a cutting edge corner on the front side to a cutting edge corner on the shank side and corresponds to the intersection line between a flank and a rake face. Each peripheral cutting edge therefore has a peripheral cutting edge length that extends beyond a mere cutting edge corner. Each groove adjacent to a peripheral cutting edge serves for chip removal.

[0013] In contrast to the end mills discussed above, as known from US 3,913,196 or US 2013 / 0294852 A1, in the end mill according to the invention the cutting ridges are now developed such that each first cutting ridge has at least one third circumferential cutting edge downstream of the first circumferential cutting edge in the circumferential direction or direction of rotation of the end mill, which third circumferential cutting edge borders a third groove which has a smaller groove cross-section than the first groove, and each second cutting ridge has at least one fourth circumferential cutting edge downstream of the second circumferential cutting edge in the circumferential direction or direction of rotation of the end mill, which fourth circumferential cutting edge borders a fourth groove which has a smaller groove cross-section than the second groove.

[0014] Every third groove that separates two third circumferential cutting edges from one another or a third circumferential cutting edge from a possibly upstream first circumferential cutting edge has a narrower or smaller, i.e. narrower and / or less deep, groove cross-section than a first groove located in front of the upstream first circumferential cutting edge. Likewise, every fourth groove that separates two second circumferential cutting edges from one another or a fourth circumferential cutting edge from a possibly upstream second circumferential cutting edge has a narrower or smaller, i.e. narrower and / or less deep, groove cross-section than a second groove located in front of the upstream first circumferential cutting edge. The third and fourth circumferential cutting edges are used to finish the surfaces created by the first and second circumferential cutting edges, respectively. The third and fourth circumferential cutting edges sever fibers that may have been created by the engagement of the first and fourth circumferential cutting edges, respectively.second peripheral cutting edges were torn out of a milled composite material but not separated. In contrast to the first and second peripheral cutting edges, milling with the third and fourth peripheral cutting edges results in thinner chips, i.e., smaller chips, which achieves a higher surface quality. The first and second peripheral cutting edges can therefore also be referred to as the first and second pre-machining, rough-machining, or roughing cutting edges, respectively, and the third and fourth peripheral cutting edges can be referred to as the third and fourth post-machining, fine-machining, or finishing cutting edges, respectively.

[0015] As a result, the end mill according to the invention achieves not only the desired compression of the milled composite materials, e.g. fiber-reinforced plastics (FRP) such as carbon- or glass-fiber-reinforced plastics (CFRP / GFRP), but also a high surface quality of a surface resulting from the milling process.

[0016] At least partial profiling of the circumferential cutting edges by so-called chip splitter grooves, i.e. a subdivision of the circumferential cutting edges into cutting edge segments, further contributes to good surface quality and chip removal. According to the invention, the first cutting edges have chip splitter grooves which divide at least some of the first circumferential cutting edges and third circumferential cutting edges into cutting edge segments, and the second cutting edges have chip splitter grooves which divide at least some of the second circumferential cutting edges and fourth circumferential cutting edges into cutting edge segments. Each cutting edge segment of a circumferential cutting edge extends from a cutting edge (segment) corner on the front side to a cutting edge (segment) corner on the shaft side and therefore has a circumferential cutting edge length that goes beyond a mere cutting edge (segment) corner.

[0017] The chip breaker grooves are achieved according to the invention in that, viewed in the circumferential direction of the end mill, every second first groove extends into the rear longitudinal region up to the shank-side end of the cutting part and divides the second and fourth circumferential cutting edges into cutting segments, and viewed in the circumferential direction of the end mill, every second second groove extends into the front longitudinal region up to the front end of the cutting part and divides the first and third circumferential cutting edges into cutting segments.

[0018] Due to the extension of the first grooves into the rear longitudinal region at least as far as the shank-side end of the cutting part and the second grooves into the front longitudinal region at least as far as the front end of the cutting part, and the associated inventive division of the cutting lands and the circumferential cutting edges into cutting edge segments, the cutting part can be manufactured simply and economically. Such a design offers the advantage that the first and second grooves delimiting the first and second circumferential cutting edges can be ground into the cutting part one after the other using a grinding wheel that has a grinding wheel profile corresponding to a cross-sectional profile of the first and second grooves and is guided over the cutting part in one pass with a twist corresponding to the respective groove and over the length of the corresponding groove.This measure therefore eliminates the need for separate operations for grinding the chip breaker grooves apart from the formation of the first and second grooves.

[0019] In the interest of the simplest and most economical design of the end mill, the third and fourth peripheral cutting edges are each designed such that every third peripheral cutting edge runs parallel to a respective upstream first peripheral cutting edge, and every fourth peripheral cutting edge runs parallel to a respective upstream second peripheral cutting edge. In this case, a grinding wheel with a constant angle of approach to the rotational axis and, if necessary, a modified radial infeed depth can be guided over the cutting part to form the first and third peripheral cutting edges or the second and fourth peripheral cutting edges.

[0020] Furthermore, the number of third circumferential cutting edges is preferably equal to the number of fourth circumferential cutting edges. In this regard, in particular, each first circumferential cutting edge can be followed by two third circumferential cutting edges, and each second circumferential cutting edge can be followed by two fourth circumferential cutting edges.

[0021] The design of the end mill can be further simplified in that the circumferential cutting edges are distributed equidistantly per cutting land, and / or the first and second grooves have the same groove widths and / or groove depths, and / or the third and fourth grooves have the same groove widths and / or groove depths, and / or all circumferential cutting edges are located on the same diameter or (flight circle) radius, and / or the first cutting lands and second cutting lands are each distributed equidistantly around the axis of rotation of the end mill, and / or the first cutting lands and second cutting lands have the same helix angles, and / or the number of first cutting lands is equal to the number of second cutting lands, in particular by an even number, in particular four, of first cutting lands and an even number, in particular four, of second cutting lands.

[0022] In an end mill according to the invention, the cutting part can be designed such that the front length region is shorter than the rear length region. In particular, the length of the front length region can be 0.1 to 3 times, preferably 0.1 to 0.2 times, the length of the cutting part.

[0023] The cutting part of an end mill according to the invention can additionally be designed with a face cutting edge. In this regard, the first grooves, which run with a positive helix angle, can be drawn into the end face of the cutting part and form face cutting edges. The cutting part can therefore have a number of face cutting edges corresponding to the number of first circumferential cutting edges, and each face cutting edge can merge via a cutting edge corner into an associated first circumferential cutting edge. The face cutting edges can each be arranged in front of an associated longitudinal center plane in which the rotational axis of the end mill lies, and when viewed axially, run in particular parallel to the associated longitudinal center plane, preferably in a straight line from the associated cutting edge corner towards the rotational axis of the end mill.

[0024] Each of the features and measures discussed above contributes to the simple and economical production of an end mill according to the invention. In this regard, for example, an end mill blank with a nominal diameter corresponding to the end mill to be produced can be machined in several grinding steps. To form the first and second peripheral cutting edges, the first grooves and second grooves can each be ground sequentially into the cutting part with the aid of a first grinding wheel, which has a grinding wheel profile corresponding to the groove cross-section of the first grooves and second grooves and is guided over the cutting part in one pass over the length of the corresponding groove, with a helix around a rotational axis of the end mill.Subsequently, to form the third and fourth peripheral cutting edges, the third grooves and fourth grooves can each be ground sequentially into the cutting part with the aid of a second grinding wheel, which has a grinding wheel profile corresponding to the groove cross-section of the third groove and fourth groove and is guided over the length of the corresponding groove in one pass over the cutting part, with a twist around the rotation axis of the end mill.

[0025] The features discussed above and further features are explained in more detail below with reference to the accompanying drawings using the example of a preferred embodiment of an end mill according to the invention. Fig. 1 shows a side view of the preferred embodiment of an end mill according to the invention. Fig. 2 and Fig. 3 show two scaled side views of the face of the end mill from Fig. 1 . Fig. 4shows a perspective scaled side view of the face area of ​​the end mill from Fig. 1 . Fig. 5 shows a scaled front view of the end mill Fig. 1 represents. Fig. 6 shows a side view of an end mill in a state (e.g. after a first manufacturing step or for clarity with second and further grooves omitted) in which the cutting part only has first grooves running with a positive helix angle. Fig. 7 shows analogous to Fig. 6 a side view of an end mill in a state in which the cutting part only has second flutes running with a negative helix angle. Fig. 8 shows a side view of an end mill in a state where the cutting part has intersecting first grooves and second grooves. Fig. 9 shows a front view of the end mill from Fig. 6 . Fig. 10 a scaled-up section "A" from Fig. 9 . Fig. 11 shows analogous to Figs. 6 and 7 a side view of an end mill in a state in which the cutting part only has third flutes running with a positive helix angle. Fig. 12 shows analogous to Fig. 11 a side view of an end mill in a state in which the cutting part only has fourth flutes running with a negative helix angle. Fig. 13 shows a front view of the end mill from Fig. 11 . Fig. 14 a scaled-up section "B" from Fig. 13 . Fig. 15 shows similar to Fig. 1 the side view of the end mill according to the invention as the result of a superposition of the Fig. 8, Fig. 11 and Fig. 12 shown groove structures.

[0026] The Figures 1 to 5 show a preferred embodiment of an end mill according to the invention for milling composite materials, e.g. fiber reinforced plastics (FRP), in different views. Figures 6 to 14illustrate individual steps of a process for producing the Fig. 1 to 5 shown end mill 10, which are intended to facilitate the understanding of the various cutting structures on the cutting part 100. Fig. 15 contains various length specifications regarding the cutting part 100.

[0027] In the embodiment shown in the figures, the end mill 10 is designed to be right-cutting or right-rotating. The end mill 10, which extends along a longitudinal center or rotational axis 20, can be functionally divided into a shank 200, which can be clamped in a chuck, and a cutting part 100 (see FIG. Fig. 1 and Fig. 15 ). In the embodiment shown, the cutting part 100 is axially directly adjacent to the shaft 200.

[0028] The cutting part 100 extends in particular from a shaft-side end 130 to a front end 120 and has, in a front / front length region 121 adjacent to the front end 120, four right-hand twisted strands, ie strands with a positive twist angle α1 (cf. Fig. 6 ) extending, first cutting ridges 122 and in a shank-side / rear length region 131 adjacent to the shank-side end four left-hand twisted, ie with a negative twist angle α2 (cf. Fig. 7 ) extending second cutting ribs 132. As in Fig. 1 shown and in Fig. 15 As indicated, the first and second cutting webs 122, 132 overlap in an overlap region K. In an end mill 10 according to the invention, the cutting part 100 can be designed such that the front length region 121 is shorter than the rear length region 131. The Fig. 15further shows that the front length region 121 is shorter than the rear length region 131 of the cutting part 100.

[0029] The first and second cutting ridges 122, 132 are each arranged equidistantly around the rotational axis 20 and are spaced apart from each other by first and second chip-removing grooves 1222, 1322, respectively. The front view in Fig. 5 shows the 90° pitch of the first cutting edges 122.

[0030] Each first cutting ridge 122 forms a first circumferential cutting edge 1221 leading or upstream in the direction of rotation, which borders a first groove 1222, and two trailing or downstream third circumferential cutting edges 1223, each bordering a third groove 1224. The third circumferential cutting edges 1223 and third grooves 1224 run parallel to the first circumferential cutting edges 1221 and first grooves 1222, i.e., with the same helix angle α1 as the first circumferential cutting edges 1221 and first grooves 1222. Analogously, each second cutting ridge 132 forms a second circumferential cutting edge 1321 leading or upstream in the direction of rotation, which borders a second groove 1322, and two trailing or downstream fourth circumferential cutting edges 1323, each bordering a fourth groove 1324. The fourth circumferential cutting edges 1423 and fourth grooves 1424 run parallel to the second circumferential cutting edges 1321 and second grooves 1322, iewith the same helix angle α2 as the second peripheral cutting edges 1321 and second grooves 1322. In . Fig. 1 For reasons of clarity, the circumferential cutting edges 1221 formed on one of the first cutting ridges 122 and the circumferential cutting edges 1321 formed on one of the second cutting ridges 132 are identified by reference numerals. In particular, one can see a first circumferential cutting edge 1221 and two third circumferential cutting edges 1223 formed on a first cutting ridge 122, as well as a second circumferential cutting edge 1321 and two fourth circumferential cutting edges 1323 formed on a second cutting ridge 132.

[0031] Each of the first, second, third and fourth circumferential cutting edges 1221, 1321, 1323, 1423 forms, in the manner known to the person skilled in the art, a cutting wedge in cross section, which is clearly defined by a wedge angle, clearance angle and rake angle, as is clear to the person skilled in the art, for example, from the Figures 10 and 14In the direction of extension, each peripheral cutting edge extends, as can be seen from the enlargements in the Figures 2 to 4 As can be seen, it extends from a cutting edge 420 on the front side to a cutting edge 421 on the shank side and corresponds to the intersection line between a flank and a rake face. Each peripheral cutting edge therefore has a peripheral cutting edge length that extends beyond a mere cutting edge. Each groove adjacent to a peripheral cutting edge therefore serves to evacuate chips.

[0032] Each third groove 1332, which separates two third circumferential cutting edges 1223 from each other or a third circumferential cutting edge 1223 from a possibly upstream first circumferential cutting edge 1221, has a narrower or smaller, ie in the embodiment shown narrower and less deep, groove cross-section than a first groove 1222 lying in front of the upstream first circumferential cutting edge 1221, as can be seen from a comparison of the representations of the Figs. 9 and 13Analogously, every fourth groove 1424, which separates two second circumferential cutting edges 1321 from one another or a fourth circumferential cutting edge 1323 from a possibly upstream second circumferential cutting edge 1321, has a narrower or smaller, i.e. narrower and less deep, groove cross-section than a second groove located in front of the upstream first circumferential cutting edge 1221. The third and fourth circumferential cutting edges 1223, 1323 serve to post-machine the surfaces produced by the first and second circumferential cutting edges 1221, 1321, respectively. As mentioned at the outset, the third and fourth circumferential cutting edges 1223, 1323 sever fibers which may have been torn out of a milled composite material by the engagement of the first and second circumferential cutting edges 1221, 1321, but which were not severed. In contrast to the first and second peripheral cutting edges 1221, 1321, milling with the third and fourth peripheral cutting edges 1223, 1323 results in smaller chip thicknesses, iesmaller chips, thereby achieving a higher surface quality. The first and second peripheral cutting edges 1221, 1321 can therefore also be referred to as the first and second pre-machining, rough-machining, or roughing cutting edges, respectively, and the third and fourth peripheral cutting edges 1223, 1323 as the third and fourth post-machining, fine-machining, or finishing cutting edges, respectively.

[0033] In the embodiment shown, the circumferential cutting edges are also distributed equidistantly on each cutting ridge. Furthermore, the first and second grooves 1222, 1322 have equal groove widths and groove depths, and the third and fourth grooves also have equal groove widths and groove depths. Furthermore, all circumferential cutting edges are located on the same diameter or (trajectory) radius.

[0034] The inventive design achieves an almost exclusively pulling cut in the front longitudinal region 121 of the cutting part 100, through which fiber composite layers or fibers of a milled composite material are pulled toward the shaft-side end 130 of the cutting part 100, and an almost exclusively pushing or pushing cut in the rear longitudinal region 131 of the cutting part 100, through which fiber composite layers or fibers of a milled composite material are pushed or pressed toward the front end of the cutting part 100. When milling an FRP plate, opposing axial forces are therefore achieved, which cause compression of the FRP material and prevent delamination and fiber protrusions on the two plate surfaces of the FRP plate.

[0035] The Fig. 1further shows that the first and second cutting edges 122, 132 and thus the first and third circumferential cutting edges 1221, 1223 and the second and fourth circumferential cutting edges 1321, 1323 formed on the cutting edges are at least partially divided or profiled into cutting edge segments by so-called chip breaker grooves 1225, 1235. Each cutting edge segment of a circumferential cutting edge extends from a cutting edge (segment) corner 420 located on the front side to a cutting edge (segment) corner located on the shaft side and therefore has a circumferential cutting edge length that extends beyond a mere cutting edge (segment) corner.

[0036] In the embodiment shown, the chip breaker grooves 1225, 1235 are achieved in that, viewed in the circumferential direction of the end mill 10, every second first groove extends into the rear longitudinal region 131 as far as the shaft-side end 130 of the cutting part 100 and divides the second and fourth circumferential cutting edges 1321, 1423 into cutting edge segments, and viewed in the circumferential direction of the end mill 10, every second second groove extends into the front longitudinal region 121 as far as the front end 120 of the cutting part 100 and divides the first and third circumferential cutting edges 1221, 1223 into cutting edge segments.

[0037] In the embodiment shown, the cutting part 100 is additionally designed to be end-cutting. The first grooves 1222, which run with a positive helix angle α1, are drawn into the end face of the cutting part 100 and form four end cutting edges, each of which merges via a cutting edge into an associated first peripheral cutting edge. The straight end cutting edges are each parallel to and in front of an associated longitudinal center plane and comprise two long end cutting edges 400 that cut across the center and two short end cutting edges 410 that end in front of the center, as shown in Fig. 5 is shown.

[0038] Based on the Figures 6 to 15 A method for manufacturing the end mill 10 described above is explained below.

[0039] To form the first and second peripheral cutting edges 1221, 1321, as can be seen from Fig. 6 and Fig. 7recognizable, firstly the first grooves 1222 and second grooves 1322 are each ground sequentially into the cutting part 100 with the aid of a first grinding wheel (not shown), which has a grinding wheel profile corresponding to the groove cross-section of the first grooves 1222 and second grooves 1322 and is guided over the length of the corresponding groove in one pass over the cutting part, with a twist around a rotation axis of the end mill 10.

[0040] As in Fig. 6As can be seen, in addition to the first groove 1222, which runs several times around the end mill 10, a short first groove 1222a is ground in the front longitudinal region of the cutting part 121, extending from the front end of the cutting part. In this embodiment, this groove is offset by 90° from the first groove 1222 in the direction of rotation of the end mill. A length l nk of this short first groove 1222a along the rotation axis 20 from the front end 121 of the cutting part 100 to the groove outlet corresponds, for example, approximately to the diameter of the end mill 10.

[0041] Fig. 7 illustrates the grinding of the second grooves 1322. Analogous to the first grooves, two second grooves 1322 offset by 90° to each other are ground starting from the shaft end 130 of the cutting part 100, one of these second grooves running almost to the front end of the cutting part (as can be seen from Fig. 7visible, at a distance of approximately one-quarter to one-fifth of the diameter of the end mill 10 from the front end 120 of the cutting part 100), while the other ends in approximately the same area in which the aforementioned short first groove 1222a ends, but just overlaps it. The grooves form the compression area near the overlap area of ​​the short first groove 1222a with the second groove ending near the end of the groove 1222a. Due to the grooves, which only overlap each other in the compression area, the number of cutting surfaces in this area increases, which leads to more reliable separation of the chips or fibers and thus to a cleaner surface of the workpiece.

[0042] Overall, this results in a Fig. 8 shown blank. As Fig. 8As can be seen, the respective first and second grooves cross each other, which results in the first grooves acting as chip separating grooves 1235 for the second grooves and conversely the second grooves acting as chip separating grooves 1225 for the first grooves.

[0043] In the Figures 9 and 10 For clarification, a front view of the blank is shown again Fig. 8 and an enlarged section of it is shown. Fig. 9 illustrates the above-mentioned 90° arrangement of the first grooves (from Fig. 6 ) to each other, while in Fig. 10 the shapes of one of the four protruding webs between two grooves, which were further processed by the work steps explained below, are shown enlarged.

[0044] To form the third and fourth circumferential cutting edges 1223, 1423, the third grooves 1224 and fourth grooves 1324 are then each ground sequentially into the cutting part 100 with the aid of a second grinding wheel, which has a grinding wheel profile corresponding to the groove cross-section of the third groove 1223 and fourth groove 1423 and is guided over the length of the corresponding groove in one pass over the cutting part 100, with a twist around the rotation axis of the end mill 10.

[0045] Analogous to the Figures 6 and 7 , which schematically demonstrate the grinding of the first and second grooves, is shown using the Figures 11 to 15 schematically explains the manufacturing of the third and fourth grooves 1224, 1324 in more detail. To simplify the drawing, the first and second grooves have been omitted in these figures. As can be seen from Fig. 11As can be seen, in this exemplary embodiment, three third grooves 1224 are ground into the cutting part (more precisely, onto the webs of the cutting part) with a predetermined helix angle (in the present example, the helix angle α1 of the first grooves 1222) and a slight offset from one another, which is approximately in the range of a groove width. This offset results, for example, from the simultaneous grinding of the grooves with a correspondingly adapted grinding tool with three projections, with which an end mill blank is ground. Alternatively, a grinding wheel could also be guided three times over the corresponding surface of the end mill. As can be seen from Fig. 11 The third grooves 1224 are ground parallel to the first grooves 1221 and only to a similar width as the first short groove 1222a. Analogously, as in Fig. 12As illustrated, three fourth grooves 1324 are ground parallel to the second groove on the webs of the cutting part 100 and end at approximately the same height as the second grooves 1322. Here, too, an offset as explained above is evident, which results, for example, from the angle of the grinding wheel. Similar to the first and second ground grooves, the third and fourth ground grooves also form an overlap area, which, during use, creates a compression of the machined material.

[0046] Fig. 13 shows the front view of the end mill 10 manufactured with such grooves according to Fig. 11 A view of the front end of the cutting part. As mentioned above, the first and second grooves milled into the finished part have been omitted here for clarity. Fig. 14 illustrated as an enlarged section from Fig. 13the shapes of the third grooves 1224 and the resulting cutting and clearance surfaces.

[0047] The end cutting edges 400, 410 are then ground into the face area of ​​the end mill 10.

[0048] Due to the extension of every second of the first grooves into the rear longitudinal region 131 and every second of the second grooves into the front longitudinal region 121 at least as far as the front end of the cutting part 120 and the associated inventive division of the cutting webs 122, 132 and the circumferential cutting edges into cutting edge segments, the cutting part 120 can be manufactured simply and economically. Such a design offers the advantage that the first and second grooves 1222, 1322 delimiting the first and second circumferential cutting edges 1221, 1321 can be ground into the cutting part 120 one after the other using a grinding wheel that has a grinding wheel profile corresponding to a cross-sectional profile of the first and second grooves 1222, 1322 and is guided over the cutting part 120 in one pass with a twist corresponding to the respective groove and over the length of the corresponding groove.This measure therefore eliminates the need for separate operations for grinding the chip breaker grooves apart from the formation of the first and second grooves 1222, 1322.

[0049] The features discussed above and each of the measures discussed above contribute to a simple and economical production of an end mill 10 according to the invention. In this regard, for example, an end mill blank with a nominal diameter corresponding to the end mill to be produced can be machined in several grinding steps. To form the first and second peripheral cutting edges 1221, 1321, the first grooves 1222 and second grooves 1322 can each be ground sequentially into the cutting part 100 with the aid of a first grinding wheel, which has a grinding wheel profile corresponding to the groove cross-section of the first grooves 1222 and second grooves 1322 and is guided over the length of the corresponding groove in one pass over the cutting part 100, with a twist around a rotation axis 20 of the end mill 10.Subsequently, to form the third and fourth circumferential cutting edges 1223, 1323, the third grooves 1224 and fourth grooves 1324 can each be ground sequentially into the cutting part with the aid of a second grinding wheel, which has a grinding wheel profile corresponding to the groove cross-section of the third groove 1224 and fourth groove 1324 and is guided over the length of the corresponding groove in one pass over the cutting part 100, with a twist around the rotation axis 20 of the end mill. List of reference symbols

[0050] 10 end mill 20 rotary axis 200 shank 100 cutting part 130 shank end of the cutting part 120 front end of the cutting part 121 front length range of the cutting part 131 rear length range of the cutting part 122 first cutting edges 132 second cutting edges 1221 first peripheral cutting edges 1222 first grooves 1222 short first groove 1321 second peripheral cutting edges 1322 second grooves 1223 third peripheral cutting edges 1224 third grooves 1323 fourth peripheral cutting edges 1324 fourth grooves 1225, 1235 chip breaker grooves 400 long end cutting edges 410 short end cutting edge 420 front cutting edge corner 421 shank cutting edge corner α1, α2Twist angle (of the first and second cutting edges and grooves) KCompression range l nk Length of the short first groove 1222a

Claims

1. An end mill (10) for milling composite materials, having a defined rotational direction, a shaft (200) and a cutting part (100), wherein the cutting part (100) extends from a shaft-side end (130) to a front-side end (120) and comprises, in a front length region (121) adjacent to the front-side end (120) of the cutting part (100), a plurality of first cutting bars (122) with first circumference cutters (1221) extending at a positive angle of twist, which are each adjacent to a first groove (1222) extending at a positive angle of twist (α1), and comprises, in a rear length region (131) adjacent to the shaft-side end (130) of the cutting part (100), a plurality of second cutting bars (132) extending at a negative angle of twist (α2) with second circumference cutters (1321), which are each adjacent to a second groove (1322) extending at a negative angle of twist (α2), wherein each first cutting bar (122) has at least one third circumference cutter (1223) downstream of the first circumference cutter (1221) and adjacent to a third groove (1224) which has a smaller groove cross-section than the first groove (1222), and each second cutting bar (132) has at least one fourth circumference cutter (1323) downstream of the second circumference cutter (1321) and adjacent to a fourth groove (1324) which has a smaller groove cross-section than the second groove (1322), characterized in that the first cutting bars (122) comprise chip divider grooves which divide at least a part of the first circumference cutters (1221) and third circumference cutters (1223) into cutter segments, and the second cutting bars (132) comprise chip divider grooves which divide at least a part of the second circumference cutters (1321) and fourth circumference cutters (1323) into cutter segments, wherein every second first groove (1222) extends into the rear length region (131) as far as the shaft-side end (130) of the cutting part (100) when viewed in the circumferential direction of the end mill (10) and divides the second and fourth circumference cutters (1321, 1323) into cutter segments, and every second second groove extends into the front length region (121) as far as the front-side end (120) of the cutting part (100) when viewed in the circumferential direction of the end mill (10) and divides the first and third circumference cutters (1221, 1223) into cutter segments.

2. The end mill (10) according to claim 1, characterized in that every third circumference cutter (1223) runs parallel to the upstream first circumference cutter (1221) and every fourth circumference cutter (1323) runs parallel to the upstream second circumference cutter (1321).

3. The end mill (10) according to claim 1 or 2, characterized in that the number of third circumference cutters (1223) is equal to the number of fourth circumference cutters (1323).

4. The end mill (10) according to claim 3, characterized in that two third circumference cutters (1223) are arranged downstream of each first circumference cutter (1221) and two fourth circumference cutters (1323) are arranged downstream of each second circumference cutter (1321).

5. The end mill (10) according to one of the preceding claims, characterized in that all circumference cutters lie on the same radius.

6. The end mill (10) according to one of the preceding claims, characterized in that the first cutting bars (122) and second cutting bars (132) are each distributed equidistantly.

7. The end mill (10) according to one of the preceding claims, characterized in that the first cutting bars (122) and second cutting bars (132) have the same angle of twist size.

8. The end mill (10) according to one of the preceding claims, characterized in that the number of first cutting bars (122) is equal to the number of second cutting bars (132).

9. The end mill (10) according to one of the preceding claims, characterized by an even numbered plurality, in particular four, of first cutting bars (122) and an even number, in particular four, of second cutting bars (132).

10. The end mill (10) according to one of the preceding claims, characterized in that the front length region (121) is shorter than the rear length region (131).

11. The end mill (10) according to one of the preceding claims, characterized in that the length of the front length region (121) is 0.1 to 3 times, preferably 0.1 to 0.2 times, the length of the cutting part (100).

12. The end mill (10) according to one of the preceding claims, characterized in that the cutting part (100) is configured to be end-cutting.

13. A method for grinding a cutting part (100) of an end mill (10) according to one of claims 1 to 12, characterized in that for forming first and second circumference cutters (1221, 1321), first grooves (1222) and second grooves (1322) are initially ground sequentially into the cutting part (100) with a twist about an axis of rotation of the end mill (10) with the aid of a first grinding wheel, which has a grinding wheel profile corresponding to the groove cross-section of the first grooves (1222) and second grooves (1322) and is guided over the cutting part (100) in one pass over the length of the corresponding groove, and for forming third and fourth circumference cutters (1223, 1323), third grooves (1224) and fourth grooves (1324) are subsequently ground sequentially into the cutting part (100) with a twist about the axis of rotation of the end mill (10) with the aid of a second grinding wheel, which has a grinding wheel profile corresponding to the groove cross-section of the third grooves (1224) and fourth grooves (1324) and is guided over the cutting part (100) in one pass over the length of the corresponding groove.