Method and device for machining longitudinal edges of metal workpieces

Abstract

A method for machining long edges of metal workpieces (2), wherein during the machining of the workpiece (2), all the cutting edges (z) are put into engagement with the machining surface (B) over an effective length (l) and having a cutting depth (t), and the removal of the chips is effected in each case over a length which is equivalent to the tooth spacing (a.sub.s) between the adjacent teeth simultaneously with their motion along the effective length (l).

Claims

1. A method for machining a longitudinal edge of an elongated metal workpiece (2) with a circumferential milling cutter (1) rotatable about a rotation axis and having at least one spiral cutting edge, the method comprising: contacting a longitudinal machining surface (B) of the workpiece (2) by the at least one cutting edge (z) of the milling cutter (1) with a plurality of teeth simultaneously; providing relative movement between the workpiece (2) and the milling cutter in the direction of the rotation axis of the milling cutter (1); wherein the plurality of teeth contact the machining surface (B) simultaneously with identical tooth spacings (as) in a direction of the relative movement; engaging the plurality of teeth (z), with the machining surface (B) over a cylindrical effective length (l) of the milling cutter (1) during machining of the workpiece (2) during the relative movement, wherein each of the plurality of teeth (z) has an identical cutting depth (t); and removing chips (s) is effected between adjacent teeth having the tooth spacing (as) simultaneously with the relative movement.

2. The method of claim 1, wherein the circumferential milling cutter (1) has, at an end thereof, a conical portion (k) that facilitates the engagement of the cylindrical effective length (l) of the milling cutter (1) with the workpiece (2).

3. The method of claim 1, wherein the at least one spiral cutting edge is embodied as cutting threads of the circumferential milling cutter (1).

4. The method of claim 1, wherein the workpiece (2) is a rail.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be described in further detail below in terms of exemplary embodiments in conjunction with the drawings. In the drawings:

(2) FIG. 1 is a schematic illustration of one exemplary embodiment of a circumferential milling cutter of the invention, having the workpiece, in a front elevation view;

(3) FIG. 2 shows the embodiment of FIG. 1 in a schematic top view;

(4) FIG. 3 is an enlarged view of the machining surface with the cutting edges of the embodiment shown in FIGS. 1 and 2;

(5) FIG. 4 is an enlarged view of the machining surface with the cutting edges of an embodiment which works with a cutting edge speed that is higher than the feed rate;

(6) FIG. 5 is a schematic view of a multi-stage tool according to an embodiment of the invention;

(7) FIG. 6 is a schematic view of a circumferential milling cutter according to an embodiment of the invention for machining tangential portions of the running surface of railroad tracks.

DETAILED DESCRIPTION OF THE DRAWINGS

(8) In FIG. 1, a circumferential milling cutter 1 according to an embodiment of the invention and a workpiece 2 are shown schematically in a front elevation view.

(9) FIG. 2 shows the circumferential milling cutter 1 of the invention, shown in FIG. 1, and a workpiece 2 in a schematic top view. The axis of rotation O of the cylindrical circumferential milling cutter 1 is disposed parallel to the machining surface B in such a way that simultaneously, all the spirally embodied cutting edges z are in engagement with the machining surface B over a length 1. The cutting edges are embodied with multiple threads, each with a slope angle or angle of inclination such that a uniform tooth spacing as is created between the cutting edges z. In the vicinity of the side toward the feed direction Lg, the circumferential milling cutter 1 is embodied conically over the length k corresponding to the angle , thereby ensuring smooth engagement of the cutting threads in transition from the noncutting state.

(10) Each circumferential milling cutter comprises a cylindrical region 1 and a conical region k, which result in a total tool length l. The circumferential milling cutter 1 is set into rotation in a predetermined manner in the direction n, so that the cutting edges move in the same direction as the feed direction L.sub.g, but slightly slower than the feed rate.

(11) In FIG. 3, the engagement region of the circumferential milling cutter shown in FIG. 1 can be seen. The cutting speed v.sub.s results from the difference between the feed rate L.sub.g and the speed of motion of the cutting threads v.sub.z in the vicinity of the machining surface B which is acted upon with a cutting depth t. Advantageously, the two speeds can be defined relative to one another in such a way that the cutting distance a.sub.s, located between two cutting threads, is attained between the cutting positions indicated once the full engagement length l of the tool with simultaneous removal of the chip s from the machining surface B is accomplished. The limit state of this mode of operation is based on the equality of time expended on the one hand in the cutting edge movement v.sub.z along the engagement path 1, and on the other of the cutting movement v.sub.s in the vicinity of a tooth spacing a.sub.s. The movements can be adapted to one another with the aid of an electronic controller. Based on the electronically detected feed rate L.sub.g, the tool rpm in the direction n can be regulated with the aid of an arithmetic unit in order to ensure that the procedure is properly performed.

(12) In comparison to the known milling methods, the method of the invention has the advantageous property that the chip lengths do not exceed the tooth spacing a.sub.s, which thus favors the use of circumferential milling cutters with a small tooth spacing and a high number of teeth.

(13) By the use of small tooth spacing on a cutter head, the number of teeth of the spirally embodied cutting edges z located in the cut in the engagement path 1 can be increased. Thus in comparison to an embodiment with a lower number of teeth, and at the same feed rate L.sub.g, a reduction in the cutting speed v.sub.s can be attained. The higher number of cutting threads additionally brings about an effective distribution of the cutting energy. Because of the curved shape of the tool jacket, the machining surface is created in the form of a shallow longitudinal groove. Depending on the tool diameter D selected and on the width of the machining surface, the deviation from a plane surface can be minimized and thus ignored.

(14) In FIG. 4, the engagement region can be seen of a circumferential milling cutter 1 whose cutting thread speed v.sub.z is greater than the feed rate L.sub.g. The cutting speed v.sub.s results from the difference between the aforementioned components. The removal of the chips s is advantageously done with a chip thickness s, corresponding to the machining depth t, simultaneously with the movement of the cutting edges along the machining edge B. The cutting length corresponds to the amount of the cylindrical length l of the tool 1, increased by one tooth spacing a.sub.s. The advantages in conjunction with the short chips s and the low metal-cutting machining speeds s, in conjunction with high feed rates L.sub.g also occur in this variant embodiment.

(15) In FIG. 5, an exemplary embodiment of a multi-stage tool according to the invention is shown schematically. By simple refinement of the features described in conjunction with FIGS. 1 through 4, a tool with two or more stages can be designed, with which it is possible to master machining situations in which the requisite machining depth t is greater than the allowable chip thickness. Two or more tools 1 are mounted on the same axis of rotation O. The function is ensured because of the equality of the tooth spacing and the effective lengths l of the tools. The diameters of the circumferential milling cutters are selected differently, to suit the chip thicknesses.

(16) FIG. 6 is a schematic view of a circumferential milling cutter 1, embodied according to the invention, which is used for machining tangential portions of curved travel surface profiles of railroad tracks. The tool 1, whose spiral cutting edges, in a position parallel to its axis of rotation O, contact the machining surface, is similarly to what is shown in FIGS. 1 through 5 disposed tangentially to one of the machining lanes of the travel surface of the rail. Between the circumferential milling cutter 1 and the workpiece 2, parallel to the machining surface B, a relative motion at the feed rate L.sub.g takes place along the machining surface B. The machining of the curved travel edge is done with a cutting track that extends at a tangent to the rail profile.

(17) When rails are used their travel surfaces have geometric and metallurgical flaws, which have a harmful influence on both service life and smoothness of travel. The rails are resurfaces by machining off the defective zones and deformations. For performing this activity, among other things, circumferential milling cutter technologies are employed that have low productivity and low working speeds, as a rule below 3 km/h. However, these values can be achieved with high cutting speeds, which in combination with short service lives result in high machining costs. The use of the milling method of the invention is advantageous in terms of both process and economy and enables much higher productivity, which attains the objective, at the speed of a slowly moving train. Thus resurfacing the rails can be done during scheduled operation, without interrupting train operation by blocking the tracks.

(18) The scope of protection of the invention is not limited to the examples given hereinabove. The invention is embodied in each novel characteristic and each combination of characteristics, which includes every combination of any features which are stated in the claims, even if this feature or combination of features is not explicitly stated in the examples.