Milling Tools

Abstract

The present invention relates to a cemented carbide milling tool having a cylindrical shank (16) and cutting head (18) for face milling workpieces made of hard, brittle materials. The cutting head (18) is configured as an end mill with a corner radius or a ball nose end mill with a cutting length (L2.2). The shank (16) has at least one clearance segment (28) extending to its chuck end (26) and having a diameter (d3) smaller than that of the cutting head (18). The tip of the cutting head (18) is coated or chipped with a hard mineral along a length (L2) with a diameter (d1) used for finishing, to which a segment (24) used for roughing is connected. The segment (24) has a cutting length (L2.2-L2=L2.1) and a reduced diameter (d4) that is smaller than the diameter (d1) of the cutting length (L2) in the cutting head (18) used for finishing and larger than the diameter (d3) of the clearance segment (28).

Description

[Technical field]

[0001] The invention relates to a carbide milling tool having a cylindrical shank and a cutting head for face milling of workpieces made of hard-brittle materials according to the preamble of claim 1. [Background technology]

[0002] The milling of workpieces made of very hard materials causes considerable wear on the milling tools used for this purpose. This problem also occurs when profiling graphite workpieces, in particular for the manufacture of spark-discharge machining electrodes for CNC machines. The graphite blocks used as starting material are usually machined using carbide end mills, the cutting heads of which can be diamond coated or tipped.

[0003] A milling tool having the features of the preamble of claim 1 is known from the Applicant's DE 101 03 04 199 A1. There, the cutting head has a short coating length and only allows short infeeds, making it suitable only for finishing and not for roughing. The adjacent length of the shaft does not perform cutting, since it is configured as a clearance segment, and therefore cannot be used for either roughing or finishing.

[0004] Another milling tool having the features of the preamble of claim 1 is described and illustrated in patent application WO 2005 / 023933. However, again in this case the non-cutting clearance segment is directly adjacent to the head segment used for finishing, so that two different milling tool configurations must be provided for roughing and finishing.

[0005] The same is true for the milling tool according to US Pat. No. 5,399,633, the cutting area of ​​which is suitable only for rough machining or only for finishing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] European Patent No. 2540427 [Patent Document 2] DE 102006026851 [Patent Document 3] International Publication No. 2018 / 163148 Summary of the Invention

[0007] It is an object of the invention to configure a milling tool such that it can be used both for rough machining and for the subsequent finishing of a workpiece. The solution to this problem is provided by the characteristic feature of claim 1, in which the segment enabling rough machining is connected to a short cutting length of the cutting head suitable for finishing machining. The clearance segment, due to its setback diameter, prevents unwanted radial pressing during finishing after rough machining.

[0008] In an advantageous development of the invention, both the finishing and the roughing segments of the cutting head are coated or chipped with hard minerals, in particular diamond.

[0009] The invention is explained below by means of exemplary embodiments shown in the drawings. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram showing how an end mill or a ball end mill is used to machine a workpiece, for example, an electrode for spark discharge machining. [Diagram 2] FIG. 1 illustrates an end mill with a corner radius and a coated cutting head according to the prior art. [Diagram 3] FIG. 3 shows a variation of FIG. 2, but with a known end mill having a corner radius with non-cutting clearance. [Figure 4]1 shows a milling tool according to the invention; [Diagram 5] 5 is a cutaway enlarged view of the cutting head in region V of FIG. 4 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 1 shows a schematic representation of a workpiece 10 made of a hard-brittle material, for example graphite, the conical upper part 12 of which is to be machined, for example for producing an electrode for spark discharge machining. To produce the desired profile of the upper part 12, a milling tool, designated in its entirety by 14, is used, which here has a cylindrical shank 16 and a cutting head 18 in the form of a ball end mill. During machining, the milling tool 14 rotates about its longitudinal axis 22 and at the same time moves along the profile of the workpiece 10 around the longitudinal axis 20 of the workpiece 10. To machine the conical upper part 12, the milling tool 14 is moved in both the x-direction and the z-direction, and optionally also in the direction of all three axes x, y, z.

[0012] FIG. 2 shows a schematic view of a conventional milling tool 14, which here is configured as an end mill with a corner radius. As is known from the applicant's patent application DE 10 10 15 200 15 30 35 40 45 50 55, the cutting head 18 provided at the tip of a shank 16 with a diameter d1 has a length s consisting of a radius r of the cutting edge rounding and a small additional length a. At the height s, i.e. at the transition to the shank 16, the cutting head 18 has the same diameter d1 as the shank 16. This has the consequence that, as the milling tool 14 is progressively fed in in the axial direction z (see FIG. 1) during roughing and finishing, the non-cutting shaft 16 is subjected to a radial compressive load and thus deformed. This not only affects the machining accuracy, but can also lead to breakage of the shank 16.

[0013] The improved configuration of the milling tool 14 according to the patent application WO 2005 / 023363, shown in FIG. 3, brings about a certain improvement here, since the shank 16 has a smaller diameter d3 at the height s than the cutting head 18 which projects radially beyond the shank 16. In this way, a non-cutting clearance 28 is formed up to the chuck end 26 of the milling tool 14, so that no radial compressive forces occur during roughing or finishing. Radial compressive forces only occur if the cutting edge diameter d1 gradually decreases when the milling tool 14 is fed axially until it reaches the dimension d3, whereby the non-cutting longitudinal area of ​​the clearance 28 causes a radial press.

[0014] The design of the cutting head 18 of the milling tool 14 according to the invention results from Figures 4 and 5. In particular, Figure 5 shows that the cutting head 18 has at its tip a cutting area with length L2 and diameter d1, which is used for finishing the previously roughened upper part 12 (see Figure 1) of the workpiece 10. The length L2 corresponds to the maximum feed of the milling tool 14 during finishing.

[0015] At point W1, the cutting head 18 transitions into a segment 24 having a length L2.2-L2=L2.1, the diameter d4 of which is somewhat smaller (for example, about 0.05 mm) than the diameter d1 of the cutting area L2. According to the invention, the segment L2.2-L2=L2.1 is configured in a cutting manner and is used for rough cutting of the workpiece.

[0016] Only at the circumference W2, an empty non-cutting clearance segment 28, once again having a reduced diameter d3, extends over the length L3-L2.2 of the shaft 16 to the beginning of the chuck end 26, which then has the same or a slightly larger diameter d2.

[0017] Both the cutting head 18 and the roughing segment 24 may be coated with a hard mineral, such as diamond, over their length L2 or L2.2-L2=L2.1.

Claims

1. A milling tool made of cemented carbide, a cutting head configured as an end mill or ball end mill with a corner radius and having an overall cutting length (L2.2); a cylindrical shank having a chuck end and at least one clearance segment axially disposed between said cutting head and said chuck end; The cutting head is integrally formed with the shank; The cutting head includes: a tip portion having a first diameter (d1) and a first cutting length (L2) and coated or tipped with a hard mineral, the tip portion being configured for finish milling of a workpiece made of a hard and brittle material; a rough cutting segment extending axially from the tip portion and integrally formed therewith, the rough cutting segment having a second cutting length (L2.2-L2=L2.1) and a second diameter (d4) smaller than the first diameter (d1); the blade of the tip portion and the blade of the rough cutting segment extend axially contiguously with each other; 4. A milling tool, comprising: a clearance segment extending axially from the roughing segment and having a third diameter (d3) smaller than the second diameter (d4).

2. 2. A milling tool according to claim 1, characterized in that the roughing segment is also coated or tipped with a hard mineral.

3. 3. A milling tool according to claim 1 or 2, characterized in that the second diameter (d4) is approximately 0.05 mm smaller than the first diameter (d1).

4. A milling tool according to any one of the preceding claims, characterized in that the chuck end has a fourth diameter (d2) which is equal to or greater than the third diameter (d3).

5. A milling tool according to any one of the preceding claims, characterized in that the tip portion is coated with diamond.

6. 6. A milling tool according to claim 5, characterized in that the roughing segment is also coated with diamond.

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