Method for making a blind hole

Abstract

A method for making a blind hole may include arranging a workpiece in a negative form with a first portion and a second portion. The first portion may include a recess. The second portion may include a guide for a punch. The recess may be arranged substantially coaxially to the guide. The method may also include displacing a material of the workpiece into the recess via pressing the punch into the workpiece. Additionally, the method may include pressing the punch into the workpiece in a first movement section with a first velocity. The method may further include further pressing the punch into the workpiece in a second movement section with a second velocity such that the material is sheared and is partly extruded into the recess. The method may include moving the first portion relative to the second portion and shearing off the material displaced within the recess.

Claims

1. A method for making a blind hole comprising: arranging a metallic workpiece in a negative form structured at least partly complementary to the workpiece with a first portion and a second portion, the first portion of the negative form including a recess configured to receive a material of the workpiece to be displaced, the second portion of the negative form including a guide for a punch wherein a diameter of the recess is equal to or smaller than a diameter of the punch and the recess includes an annular step where the diameter of the recess changes abruptly, and wherein the recess is arranged substantially coaxially to the guide; moving the punch in an axial direction in the guide toward the workpiece and establishing a first contact between the punch and the workpiece; displacing the material of the workpiece into the recess via pressing the punch into the workpiece; pressing the punch into the workpiece, after establishing the first contact, in a first movement section with a first velocity such that the material of the workpiece encountered by the punch in the first movement section is sheared in an adiabatic state; further pressing the punch into the workpiece in a second movement section with a second velocity such that the material of the workpiece encountered by the punch in the second movement section is sheared and compacted on one of i) an annular step defined by a difference in the diameters of the recess and the diameter of the punch and ii) the annular step of the recess and is partly extruded into the recess, wherein the second velocity is smaller than the first velocity; and moving the first portion relative to the second portion substantially orthogonally to the axial direction and shearing off the material displaced within the recess.

2. The method according to claim 1, wherein the pressing the punch into the workpiece in the first movement section includes pressing the punch into the workpiece to a first depth of approximately 0.01 times a height of the workpiece to 0.5 times the height of the workpiece.

3. The method according to claim 2, wherein the pressing the punch into the workpiece in the second movement section includes pressing the punch into the workpiece to a second depth, the first depth and the second depth defining a total depth of approximately 0.8 times the height of the workpiece to 0.9 times the height of the workpiece.

4. The method according to claim 3, wherein: the first velocity is at least 1 m/s; and the second velocity is 0.15 m/s or less.

5. The method according to claim 4, wherein: the first velocity is approximately 6 m/s to 8 m/s; and the second velocity is 0.005 m/s or less.

6. The method according to claim 1, wherein the pressing the punch into the workpiece in the first movement section includes pressing the punch into the workpiece to a first depth, and wherein the pressing the punch into the workpiece in the second movement section includes pressing the punch into the workpiece to a second depth, the first depth and the second depth defining in the first and second movement section a total depth of approximately 0.8 times a height of the workpiece to 0.9 times the height of the workpiece.

7. The method according to claim 1, wherein the pressing the punch into the workpiece in the first movement section includes pressing the punch into the workpiece to a first depth of less than approximately 10% of a height of the workpiece.

8. The method according to claim 1, wherein the first velocity is at least 1 m/s.

9. The method according to claim 8, wherein the first velocity is approximately 6 m/s to 8 m/s.

10. The method according to claim 9, wherein the first velocity is approximately 7 m/s.

11. The method according to claim 8, wherein the second velocity is 0.15 m/s or less.

12. The method according to claim 1, wherein the second velocity is 0.15 m/s or less.

13. The method according to claim 12, wherein the second velocity is 0.005 m/s or less.

14. The method according to claim 1, wherein the establishing a first contact between the punch and the workpiece includes contacting a curved surface of the workpiece with the punch at a point of the curved surface where a tangent of the curved surface is perpendicular to the axial direction.

15. The method according to claim 14, wherein: the pressing the punch into the workpiece in the first movement section includes pressing the punch into the workpiece to a first depth of approximately 0.01 times a height of the workpiece to 0.5 times the height of the workpiece; and the pressing the punch into the workpiece in the second movement section includes pressing the punch into the workpiece to a second depth, the first depth and the second depth defining a total depth of approximately 0.8 times the height of the workpiece to 0.9 times the height of the workpiece.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the Figures

(2) FIGS. 1a-1d schematically show various steps of the method for implementing a method according to the invention for making a blind hole,

(3) FIG. 2 schematically shows a velocity vs. time diagram to explain the method,

(4) FIG. 3 schematically shows a groove block made according to the method of the invention,

(5) FIG. 4 schematically shows a cross-sectional representation through a profile piece with a groove block made according to the invention,

(6) FIGS. 5a and 5b each schematically show a representation as in FIGS. 1a and 1b, but with a different recess in the first portion.

DETAILED DESCRIPTION

(7) According to FIGS. 1a-d and 5a,b, a device 1 according to the invention for carrying out the method explained in the following paragraphs for making a blind hole 2 in a metallic workpiece 4, especially one having at least one curved surface 3, is shown. The device 1 according to the invention herein comprises a negative form 5 fashioned so as to be at least partly complementary to the workpiece 4 being machined with a first portion 6 (female die) and a second portion 7. There is provided in the first portion 6 of the negative form 5 a recess 8 arranged substantially coaxially to the blind hole 2 being produced for material 9 being displaced during the making of the blind hole 2 (see FIGS. 1b to 1d), the recess 8 preferably tapering conically in the direction of the workpiece 4 being machined, so that the material 9 extruded into the recess 8 after a shearing off can drop downward automatically. In the second portion 7 of the negative form 5 a guide 10 for a punch 11 (male die) is provided, arranged substantially coaxially to the blind hole 2 being produced. By means of a displacement device 12, which is shown only highly schematized in FIG. 1b, the punch 11 can be moved in the axial direction 13, that is, coaxially to the blind hole 2 being produced and to the guide 10, as well as to the recess 8, the displacement device 12 being furthermore designed such that it can move the punch 11 in different movement sections B.sub.1 and B.sub.2 with different velocities v.sub.1 and v.sub.2.

(8) A diameter D.sub.A of the recess 8 in the first portion 6 of the negative form 5 herein according to FIGS. 1a-d is smaller than an outer diameter D.sub.S of the punch 11 at the location bordering on the workpiece 4 being machined (cf. FIG. 1a).

(9) In FIGS. 5a, b, there is likewise provided in the first portion 6 of the negative form 5 a recess 8 arranged substantially coaxially to the blind hole 2 being produced for material 9 being displaced during the making of the blind hole 2 (see FIG. 5b), but it has an annular step 15a, so that a diameter D.sub.A changes abruptly in the region of the annular step 15a, being reduced abruptly in the downward direction. Beneath the annular step 15a shown in FIGS. 5a, 5b, the recess 8 preferably widens conically, so that in this case the material 9 extruded into the recess 8 does not drop down automatically after a shearing off, but instead is held at the annular step 15a. The (inner) diameter D.sub.A of the recess 8 in the first portion 6 above the annular step 15a may correspond herein to the outer diameter D.sub.S of the punch 11. On the lower side of the first portion 6 of the negative form 5 the diameter D.sub.A may also once more correspond to the diameter D.sub.S thanks to the conical widening. The depth t.sub.1 of the recess 8 above the annular step 15a should correspond substantially to at least the depth t.sub.1 of the first movement section B.sub.1 (HGSS depth). It is likewise conceivable for the depth t.sub.1 to be defined as t.sub.1+x, where x corresponds to a control parameter at which the compression is supposed to begin. Thanks to this configuration, an elastic mounting of the first portion 6 of the negative form 5 can be omitted, since the material 9 which is expelled during the first movement section B.sub.1 during the high-speed shearing with the first velocity v.sub.1 would not impact on and destroy the female die, that is, the first portion 6. Thus, the depth t.sub.1 up to the annular step 15a is preferably around 0.01 H≤t.sub.1≤0.5 H, preferably t.sub.1≤0.1 H, where H stands for the overall height of the workpiece 4.

(10) Furthermore, in the device 1 according to the invention the first portion 6 of the negative form 5 is movable substantially orthogonally to the axial direction 13, that is, with respect to the punch axis 14 here, relative to the second portion 7 of the negative form 5, so that a shearing off of the material 9 extruded into the recess 8 during the making of the blind hole 2 may occur, as is shown in FIG. 1d. Purely theoretically, it is also of course conceivable herein for the second portion 7 of the negative form 5 to be movable relative to the first portion 6 or for both portions 6, 7 to be movable relative to each other.

(11) The method according to the invention for making the blind hole 2 functions as follows:

(12) First of all, the negative form 5 with the first and second portion 6, 7 is provided and the workpiece 4 being machined is arranged therein, as shown by FIGS. 1a, 5a. After this, the punch 11 is moved by means of the displacement device 12 in the axial direction 13 toward the workpiece 4, wherein the punch 11 after a first contact with the workpiece 4 is pressed in a first movement section B.sub.1 (also see FIG. 2) with a first velocity v.sub.1 into the workpiece 4, where v.sub.1 is so high that the material encountered by the punch 11 in the first movement section B.sub.1 is sheared off in an adiabatic state. This condition is represented for example by FIGS. 1b, 5b. The first portion 6 of the negative form 5 is elastically mounted, especially in order to withstand the high impulse occurring during the first movement section B.sub.1 without damage.

(13) After this comes a further pressing of the punch 11 into the workpiece 4 in a second movement section B.sub.2 with a second velocity v.sub.2, which is smaller than the first velocity v.sub.1, so that the material encountered by the punch 11 in the second movement section B.sub.2 is sheared and at the same time compacted on an annular step 15 formed by the different diameters D.sub.A and D.sub.S of the recess 8 and the punch 11 (see FIG. 1c) or on the annular step 15a and furthermore is partly extruded into the recess 8. In FIG. 1c, the punch 11 is no longer shown, for better clarity.

(14) In the optional succeeding step of the method, represented in FIG. 1d, a relative displacement occurs between the first portion 6 and the second portion 7 of the negative form 5 or vice versa, substantially orthogonally to the axial direction 13 or to the punch axis 14, which at the same time also represents a blind hole axis or a recess axis, and thus the material 9 displaced into the recess 8 is sheared off. After this, the workpiece 4 provided with the blind hole 2 according to the invention can be removed from the negative form 5.

(15) Considering FIG. 2, for example, one may recognize therein the individual movement sections B.sub.1 and B.sub.2 as well as the corresponding velocities v.

(16) The punch 5 in the first movement section B.sub.1 is pressed into the workpiece 4 with a first velocity v.sub.1 of v.sub.1≥1 m/s, especially with 6 m/s≤v.sub.1≤8 m/s, especially preferably with v.sub.1≈7 m/s. In this process, a so-called high-speed shearing occurs, with which an especially smooth surface can be achieved. However, no extrusion can occur herein, due to the high first velocity v.sub.1 and the concomitant high impulse. In the following second movement section B.sub.2 the second velocity v.sub.2 decreases significantly and is preferably <0.5 m/s, especially ≤0.15 m/s, or even especially preferably v.sub.2≤0.005 m/s, by which an extrusion of the material 9 displaced by the punch 11 into the recess 8 may occur. The last movement section B.sub.3 merely denotes a return of the punch 11 to its starting position.

(17) The punch 11 in the first movement section B.sub.1 is pressed into the workpiece 4 by a depth t.sub.1 of around 0.01 H≤t.sub.1≤0.5 H, where H stands for the overall height of the workpiece 4. The punch 11 in this case in the first movement section B.sub.1 is pressed into the workpiece 4 preferably less than 10%, that is, t.sub.1≤0.1 H. The punch 11 in the first and second movement section B.sub.1, B.sub.2 is pressed into the workpiece 4 by a total depth t.sub.1,2=t.sub.1+t.sub.2 of around 0.8 H≤t.sub.1,2≤0.9 H, so that after removing the punch 11 from the blind hole 2 there remains a blind hole bottom 16 with a thickness d of around 0.1 to 0.2 H.

(18) If the workpiece 4 is fashioned for example as a groove block 17 (cf. FIGS. 3 and 4), it may have a height H of around 7.3 mm, an overall depth of the blind hole t.sub.1,2 of around 6.3 mm, and a blind hole bottom 16 with a thickness d of around 1.0 mm.

(19) The workpiece 4 produced according to the invention can be, for example, a groove block 17, which receives a spring-loaded fixation element 18 in the blind hole 2 produced according to the invention, by which the groove block 17 can be held in an undercut groove 19 (see FIG. 4). Of course, the groove block 17 may also have, in addition to the blind hole 2, a through opening 20 produced in similar fashion (see FIG. 3), in which an internal thread is cut to receive a fastening screw. Of course, it is also clear that the groove block 17 illustrated need not necessarily have a curved surface 3, but also of course can be fashioned as a rectangular block, or one which is triangular in cross section.

(20) With the method according to the invention and the device 1 according to the invention, an especially exact blind hole 2 can be produced by manufacturing technology and furthermore in an economical way.