Tool for chipless manufacturing or finishing of screw threads, manufacturing method of said tool, and manufacturing method of screw threads

Abstract

To provide a tool for chipless manufacturing or finishing threads with high accuracy, and a method for manufacture of the threads.SOLUTION: A tool 1 comprises at least one molding part 5 which is rotatable around a tool shaft A, a plurality of pressing lobes in the molding part is continuously arranged along a molding curve 6 which substantially extends spirally around the tool shaft A, a pitch of the molding curve 6 substantially corresponds to a pitch of a manufactured or finished thread, and the molding curve has a spiral angle. A profile of at least one pressing lobe is so designed that the manufactured thread has an arch shape or an ogive shape, which is round at least partially, in an axial direction cross section including the tool shaft.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tool for chipless making or finishing of threads, a method for making the tool, and a method for making threads. [Background technology]

[0002] A ball screw drive is a screw drive with balls inserted between the screw and the nut. When rotating between the screw and the nut, the balls roll in a corresponding ball screw (or ball screw groove). Such ball screws are traditionally manufactured using mounting points, a well-known procedure that is time-consuming. Such ball screws must be highly accurate. High accuracy can only be achieved if the manufactured screw thread can be measured.

[0003] For measuring such threads, stylus measuring instruments are known, for example, from DE 19947001 A1, DE 102013015237 A1 or DE 102017103954 A1. Such scanning measurements still have a higher accuracy than optical measurements. In order to use stylus measuring instruments, the line to be measured must have certain properties, in particular protruding areas of the surface can prevent the alignment of the stylus measuring instrument to the surface. In stylus measuring instruments there is a stylus finger with a probe head. This stylus finger is guided along the measuring line. The measuring line of the internal thread runs in particular parallel to the thread axis.

[0004] According to the prior art, cold forming tabs are known which produce or finish threads without cutting. With these tools, the threads are produced without cutting by forming the workpiece, so-called pressing lobes, also known as forming wedges or teeth, which cause cold deformation of the workpiece by pressure. Such pressing lobes have flanks. The advantage of these tools is that the deformation of the surface and the resulting hardening increases the hardness of the material in the area of ​​the thread profile, which results in a more wear-resistant thread than with chip thread production.

[0005] Known cold-form tabs, in particular for producing internal threads, comprise a shank, which is usually cylindrical and whose end facing away from the workpiece is received and held in a chuck of a thread-forming device, and the working area, in particular the forming part, is located on the side of the cold-form tab opposite the shank.

[0006] The forming portion is provided with a spiral forming curve along the circumferential direction, and the pressing lobe is formed as a protuberance along this forming curve.

[0007] In the case of the cold-formed tabs known from DE102012100734A1, the pitch angle between two successive pressing lobes along the forming curve is the same for all pressing lobes. The imaginary straight connecting lines between the tips of the pressing lobes along the forming curve, apart from radial deviations, in their projection onto a surface perpendicular to the tool axis, essentially form a regular n-gon (polygon), in which n pressing lobes are arranged per revolution of the forming curve around the tool axis. Each n-th pressing lobe is arranged along a straight line parallel to the tool axis. These pressing lobes arranged along straight lines form so-called pressing ridges. Furthermore, cold-formed parts are also known from DE102012100734A1.

[0008] In known thread formers, the pressing lobes have a profile that is determined perpendicular to the forming curve. The pressing lobes have a triangular, elliptical or cylindrical profile, especially in the upper region of the pressing lobe. Such a profile is perpendicular to the course of the forming curve. A section perpendicular to the forming curve is further called a normal section. In the case of a forming curve with a thread pitch, this means that the profile of the normal section is inclined by a pitch angle α towards a plane containing the rotation axis of the thread cutter, i.e. the axial section. The plane containing the rotation axis (axial section plane) is the rz plane of the cylindrical coordinate system. The helix angle α lies in the θ-z plane, θ being the angular coordinate of the coordinate system. With α=0° the curve has no pitch and is rotated perpendicular to the rotation axis. α=90° corresponds to the direction of the rotation axis.

[0009] Such profiles cannot be measured with sufficient accuracy using known stylus measuring instruments, in particular the profiles along the pressing lobes cannot be measured with sufficient precision in known, particularly polygonally shaped, thread grooves. Summary of the Invention

[0010] It is an object of the present invention to provide a tool for chipless manufacturing or finishing of threads with greater accuracy.It is a further object of the present invention to define a method for manufacturing threads that can be more accurately measured using a stylus measuring device, and a method for manufacturing a thread tool for manufacturing such threads.

[0011] Concerning the tool, the object is solved by a tool for non-cutting production or finishing of a thread, in particular a ball screw, in or on a workpiece, in particular a cold forming tab or thread former, comprising at least one forming part rotatable about a tool axis for non-cutting production or finishing of a thread, in particular an internal thread. The forming part has several pressing lobes projecting radially outward from the tool axis, the thread being produced or finished by pressing said several pressing lobes against the workpiece surface. The pressing lobes are arranged successively along a forming curve that extends substantially helically around the tool axis. The gradient of the forming curve substantially corresponds to the gradient of the thread to be produced or finished, where the forming curve has a helix angle α. According to the invention, the profile of the at least one pressing lobe is designed such that in an axial section including the tool axis, the produced thread is at least partially rounded arch or ogival. The section including the rotation axis of the thread cutter is an axial section. In the case of a forming curve with a thread pitch, this means that the profile in the normal section is inclined by the pitch angle α towards the plane containing the axis of rotation of the thread cutter, i.e. the axial section. Preferably, the profiles of some or all pressing lobes are designed in this way. The round or ogive shape makes it easier for the probe head to reach the surface in the axial section, improving the measurement accuracy.

[0012] A rounded arch is understood in particular to be a cylindrical, elliptical or convex arch with a varying radius. An ogive is understood in particular to be a Gothic arch with a uniform or varying radius. The tip of an ogive arch may be rounded. In one embodiment, the varying radius may be a profile having different parts with different radii, for example 2 to 5 different radii, and in particular having a transition area between them such that the curvature changes from a first radius to a second radius.

[0013] In one embodiment, the profile of at least the first pressing lobe is at least partially, in particular entirely, rounded arch or ogive in a cross section including the tool axis. In particular, the radially outer region of the first pressing lobe, preferably the region including the pressing lobe tip, has a rounded or ogive profile. In particular, the profile is one of the following: rounded arch, ogive, ogive with rounded tip, ogive with a first radius in the region of the tip and a second radius in the region of the flank, ogive with extended legs. Two adjacent pressing lobes in an axial cross section may be separated by a groove. Such a groove may in particular be flat or concave in an axial cross section.

[0014] In further embodiments, the tool comprises in particular two, or three, or four, or five, or six or more pressing lobes and / or the pressing lobes are arranged on at least two pressing ridges. Such a pressing ridge is formed in the sense of the present invention by a plurality of pressing lobes. This is in particular a pressing ridge in which each n-th pressing lobe is arranged along a straight line parallel to the tool axis, i.e. at an angle of 360°. In particular, the first pressing lobe is arranged on the pressing ridge. A pressing ridge with several first pressing lobes, in particular a pressing ridge with the first pressing lobe exclusively on the shaped part, is a first pressing ridge. Thus, the first pressing lobe has a rounded or ogive-shaped profile in the axial cross section, in particular in the region including the tip of the pressing lobe. In this configuration, the profile of the tool along the tool axis, in particular along the tip of the pressing lobe, can be measured particularly well with a stylus measuring instrument.

[0015] Then, by geometric transformation, the shape of the thread to be produced can be calculated exactly, or the corresponding profile in the axial section can be calculated from the shape of the thread to be produced and the required profile in the normal section.

[0016] Optionally, one of the pressed ridges along the forming curve is longer than the other pressed ridges, in particular the second pressed ridge being the longest pressed ridge, is shorter, in particular the first pressed ridge, in particular 1.5 to 2.5 times longer at the sweep angle θ. In one embodiment, the longest pressed ridge thus substantially corresponds to two adjacent pressed ridges without a lubrication groove between them.

[0017] In particular, the longer second pressing ridge may be a pressing ridge with several second pressing lobes, in particular a pressing ridge with the second pressing lobes exclusively in the moulding. In particular, the tool comprises just one second pressing ridge and several first pressing ridges. The first and second pressing ridges ideally have a similar or identical profile.

[0018] In one embodiment, the tool has at least one, in particular several, cooling channels, each having an outlet opening in the shank-side part of the forming.

[0019] In a further embodiment, at least some of the pressing lobes, in particular the first and / or second pressing lobes, have an initial forming region and / or a free surface region. In the initial forming region, the height of the pressing lobe increases in the radial direction, and in the free surface region, the height of the pressing lobe decreases in the radial direction, so that a clearance angle exists here. The initial forming region is located in front of the pressing lobe tip in the direction of rotation along the forming curve. The clearance region is located behind the pressing lobe tip in the direction of rotation.

[0020] The initial forming zone and / or the free surface zone may follow a polygonal course. The forming zone merges into the zone of the pressing lobe tips by a transition zone and / or the zone of the pressing lobe tips merges into the free surface zone by another transition zone. In particular, the initial forming zone may have a forming edge angle in the range of 5° to 17°, in particular 12°.

[0021] In one embodiment, the shaping portion comprises a shaping region and a calibration region, the shaping curve in the shaping region being in particular 1 to 3 revolutions and the shaping curve in the calibration region being in particular 2 to 20 revolutions, preferably 5 to 10. In a further configuration, the calibration region may be conical such that the diameter of the calibration region increases towards the shank.

[0022] The method according to the invention for the non-cutting production or finishing of a screw thread, in particular a ball screw, preferably an internal thread, with a tool according to the invention allows the production of a screw thread, which has a thread pitch with a helix angle α and which is suitable for scanning with a stylus measuring device known per se. The advantage of the method according to the invention is that the screw thread can be produced with high precision and with less time expenditure.

[0023] In one embodiment, the thread produced in the part comprising the tool shank is at least partially round or ogive, in particular cylindrical.

[0024] After the threads are cut, they are finished.

[0025] The method according to the invention for the manufacture of a tool according to the invention, in particular a cold-formed tab or a thread former, is suitable for the non-cutting manufacture or finishing of a thread, in particular a ball screw, in or on a workpiece, which method in particular comprises the steps of providing a blank and milling or cutting a pressing lobe or of providing a shank and building up the pressing lobe by an additive manufacturing process, in particular 3D printing.

[0026] The present invention will also be explained in more detail below with reference to further features and advantages with reference to the description of embodiments and the accompanying drawings. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 shows an embodiment of a thread tap according to the present invention. [Diagram 2] 2A-2C further illustrate the embodiment of the thread tap of FIG. 1. [Diagram 3] FIG. 2 shows a tip of the embodiment of the thread tap of FIG. 1. [Figure 4] FIG. 13 illustrates the profile of the pressing lobe along the forming curve. [Diagram 5] FIG. 2 shows a thread profile. [Figure 6] FIG. 1 is a superposition of the profiles of the pressing lobes in the axial and normal sections. [Figure 7a] FIG. 13 illustrates different ogive-shaped profiles of the pressing lobes. [Figure 7b] FIG. 13 illustrates different ogive-shaped profiles of the pressing lobes. [Figure 7c] FIG. 13 illustrates different ogive-shaped profiles of the pressing lobes. [Figure 8a] FIG. 13 illustrates different ogive-shaped profiles of the pressing lobes. [Figure 8b] FIG. 13 illustrates different ogive-shaped profiles of the pressing lobes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The cold-formed tab 1 in Figure 1 has a shank 2 and a forming portion 5. The shank is at least partially cylindrical and has a squared profile at the end opposite the forming portion 5, which is suitable for mounting in the chuck of a thread forming device. The cold-formed tab has a tool axis A which is the axis of rotation.

[0029] The forming section 5 is divided into a forming area 3 facing the tool tip and a calibration area 4. In the forming section 5, pressing lobes 7 are arranged on pressing ridges 9,10. The pressing ridges 9,10 are straight pressing ridges. The pressing lobes 7 lie on a helical forming curve 6 with a helix angle α. In the calibration area 4, the pressing lobes 7 have a greater radial height than in the forming area 3. A lubrication groove 11 is arranged between two adjacent pressing ridges 9,10. The pressing ridges 9,10 and the lubrication grooves 11 extend parallel to the tool axis A.

[0030] Adjacent pressing lobes 7 in the pressing ridges 9, 10 are not directly adjacent, but are separated from each other by grooves 14, which in the illustrated embodiment are flat in axial cross section. Here, the grooves 14 extend parallel to the forming curve 6. The pressing lobes 7 have a profile 20 parallel to the tool axis, i.e. in the axial cross section. This profile 20 is bounded in the tool axial direction by a profile boundary curve 21a. The two profile boundary curves of adjacent pressing lobes 7 do not meet here, but meet at their respective ends at the groove 14. In a cross section perpendicular to the forming curve 6, i.e. in the normal cross section, the same pressing ridge has different profile boundary curves 21b with a helix angle not equal to zero. In an alternative embodiment not shown, adjacent pressing lobes 7 can also be adjacent without a groove or separated by a concave groove tapering towards the shaft axis. In the first case, the respective profile boundary curve ends at a junction or a transition to a concave groove.

[0031] As shown in FIG. 2 and especially FIG. 3, the pressing ridges 9, 10 have different lengths. In the view of the tool tip in FIG. 3, the cold-formed tab 1 is polygonal, here with five corners. Each of the pressing ridges 9 has a polygonal corner. The pressing ridges 9 with the pressing lobes 7a and 7c have a first length and each constitute one polygonal corner. These are the first pressing ridges 9 with the first pressing ridges 7a and 7c. The pressing ridge 10 with the pressing lobe 7b has a longer length and comprises two polygonal corners. This is the second pressing ridge 10 with the second pressing lobe 7b. The polygonal corner area of ​​each pressing lobe forms a pressing lobe tip 8 that has a greater radial distance to the tool axis A than the other areas of the pressing lobe. The second pressure lobe 7b has pressure lobe tips 8a, 8b, where pressure lobe tip 8a is on the forming curve rearward of pressure lobe tip 8b. The pressure lobe tips 8a, 8b can have different radial distances relative to the tool axis.

[0032] The shorter first pressing lobe 7a and / or the longer second pressing lobe 7b with the initial forming area 15 and the free surface area 16 have, as shown in FIG. 4, in particular a forming edge angle δ. Towards the corners of the polygon a transition area is formed. The apex of the pressing lobe 8 has, along the forming curve 6 and in a plane inclined by α to the vertical, i.e. in the axial section, a cylindrical profile, thus a rounded arch profile here, and further has a curved or smooth area beyond the transition area to a free surface area with a clearance angle ξ. In this example, the clearance angle ξ corresponds substantially to the forming edge angle δ, in particular to the forming edge angle ±5°.

[0033] 5 shows a thread profile 30 having a thread 31 wound along a forming curve 6. In a normal cross section N, i.e. in a view inclined by a pitch angle α with respect to the axial cross section, the illustrated thread profile has a rounded arc-shaped profile, in particular a cylindrical profile.

[0034] 6-8 show further profiles of the pressing lobe, in particular the pressing lobe tip, in normal or axial cross section. FIG. 6 shows a second embodiment of the profile of the pressing lobe, where the normal and axial cross sections overlap. The arc K serves only as a visual support and facilitates the recognition of the changing radius along the profile boundary curves 21a, 21b. The profile boundary curve 21a represents the profile boundary curve in the axial cross section, and the profile boundary curve 21b represents the profile boundary curve in the normal cross section. Both profile boundary curves 21a, 21b are ogive-shaped. The two profile boundary curves 21a, 21b are different in the lower region facing the respective groove 14. FIG. 7a shows an ogive-shaped profile in an axial cross section, and FIG. 7b shows an ogive-shaped profile in an axial cross section with a rounded tip. FIG. 7c shows a further ogive-shaped profile in axial section, which deviates from the previously shown profiles in that the radius of the area facing each groove 14 is radius R1, which merges in the area of ​​the tip of the ogive arch with radius R2, where R1 <R2である。

[0035] Figures 8a and 8b show further embodiments of the profile of the pressure lobes, especially in the region of the pressure lobe tips. In figure 8a, the two legs of the two-pointed arch have a uniform radius. In figure 8b, the radius of the two legs increases in the region facing the groove 14 and the legs extend tangentially. [Explanation of symbols]

[0036] 1 tool 2 Shank 3 Molding area 4 Calibration area 5 Molding section 6 Molding curve 7 Pressing Lobe 8 Pressing lobe tip 9 First pressing ridge 10 Second pressing ridge 11 Lubrication groove 12 Cooling channel outlet 14 groove 15 Initial forming area 16 Free surface area 20 Profiles 21a First profile boundary curve 21b Second profile boundary curve 30 Thread Profiles 31 Thread A Tool axis N normal cutting plane α Helix angle δ Forming edge angle ξ Clearance angle θ Angular coordinate in the coordinate system K Arc

Claims

1. 1. A tool for chipless making or finishing a thread in or on a workpiece, comprising: At least one forming part rotatable about a tool axis for chipless manufacturing or finishing of a female thread, the forming portion includes a plurality of pressure lobes projecting radially outward from a tool shaft, the plurality of pressure lobes being pressed against a surface of the workpiece to produce or finish a thread; the plurality of pressing lobes being successively arranged along a forming curve that extends substantially helically about a tool axis; the pitch of the forming curve substantially corresponds to the pitch of the thread to be manufactured or finished; The forming curve has a helix angle; the profile of at least one pressing lobe is at least partially rounded arch or ogive in an axial cross section including the tool axis; the pressing lobe is disposed on at least two pressing ridges, one of the at least two pressing ridges being a first pressing ridge and the other of the at least two pressing ridges being a second pressing ridge; the second pressing ridge is longer along a forming curve than the first pressing ridge and has a sweep angle 1.5 to 2.5 times greater than the first pressing ridge.

2. 2. The tool of claim 1, wherein the profile of one or more or all of the pressure lobes is selected from one of the following profiles: round, ogive, ogive with a rounded lobe tip, ogive with a first radius in the area of ​​the pressure lobe tip and a second radius in the area of ​​the side lobe, and ogive with extended legs.

3. 3. A tool as claimed in claim 1 or 2, comprising two, or three, or four, or five, or more than five pressure lobes.

4. A tool according to claim 1 , further comprising cooling channels, the cooling channels having outlet openings in the shank-side portion of the forming portion.

5. 5. A tool as claimed in claim 1, wherein at least some of the pressing lobes have an initial forming region located in front of the pressing lobe tip in the direction of rotation along the forming curve and / or a free surface region located behind the pressing lobe tip in the direction of rotation along the forming curve, and a shape along the forming curve formed by the initial forming region and / or the free surface region and the pressing lobe tip is a polygon.

6. A tool as described in claim 5, wherein the initial forming region merges into the region of the pressing lobe tip by a transition region and / or the region of the pressing lobe tip merges into the free surface region by a further transition region.

7. The molding section includes a molding area and a calibration area, 7. A tool according to claim 1, wherein the forming curve in the forming region is from 1 to 3 revolutions and the forming curve in the calibration region is from 2 to 20 revolutions.

8. A method for non-cutting production or finishing of a thread with a tool according to any one of claims 1 to 7, comprising the steps of: The thread has a thread pitch with a helix angle and is at least partially round or ogive in a cross section containing the tool axis.

9. A method for finishing a thread with a tool according to any one of claims 1 to 7, comprising the steps of: the thread has a thread pitch with a helix angle and is at least partially round or ogive in a cross section containing the tool axis; The method wherein the threads are finished after they are cut.

10. A method for manufacturing a tool for non-cuttingly manufacturing or finishing a thread in or on a workpiece according to any one of claims 1 to 7, comprising the steps of: a) providing a blank and milling or machining a pressing lobe; b) providing a shaft and building, in an additive manufacturing process, a pressing lobe; The manufacturing method is selected from the following:

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