EP2343138A1 - Method and device for forming workpieces - Google Patents

Abstract

The device has an inner molding tool is arranged coaxial to machine main axis (x) of a main spindle (1.1) that comprises a driver (11). The inner molding tool is axially positioned and/or axially moved relative to axial position of an outer molding tool (8), which is radially positioned or moved radially, during formation of a blank mold, which is formed as a rotationally symmetrical hollow body. The inner molding tool has a spherical, outer contour that has a set of conical, concave, and/or convex transitions. An independent claim is also included for a method for producing workpieces from a blank mold.

Description

The invention relates to a device for forming workpieces according to the preamble of claim 1 and a method for forming workpieces according to claim 8.

Methods are known in which a workpiece is set in rotation and then formed by rolling or rolling from outside to the workpiece. Often these workpieces are designed as rotationally symmetrical hollow body. The hollow bodies may have unilaterally closed bottoms.

In most cases, this transformation takes place in such a way that the outer forming rollers press the shell of the hollow body-shaped workpiece against an internal mandrel, so that the material is made to flow within a forming zone between the forming tools axially, radially and tangentially. The wall thickness of the shell is reduced.

The reshaped hollow body is guided over its entire length on the inner mandrel, so that at least 50% of the finished workpiece are on the inner mandrel after the forming. Depending on the process, 100% of the length of the workpiece may also be on the inner mandrel.

The pressing of the material against the inner mandrel during the forming has the disadvantage that a very high friction arises between the inner surface of the workpiece and the surface of the inner mandrel. The friction in turn leads to adverse heating of the workpiece and inner mandrel. In addition, the wear of the surface during the forming process due to the friction stress.

Furthermore, the ideal outer diameter of the inner mandrel must be found by experiments, which makes expensive subsequent corrections to the outer diameter of the inner mandrel required. The production of workpieces with different inner diameters at different wall thicknesses within a workpiece with an internal mandrel is excluded. For the production of such workpieces a split internal mandrel, which is attached to each of the main spindle and tailstock spindle, is required. However, such a device with split internal mandrel is expensive. In addition, the possible contour of the workpiece is also limited, since even a split mandrel allows only a limited design freedom of the inner contour of the workpiece to be formed.

The object of the invention is to provide a method that makes the shaping of rotationally symmetrical workpieces with constant and different wall thicknesses at different outside and inside diameters possible, and to provide an apparatus for performing this method, in which the mentioned disadvantages do not occur or to a lesser extent.

This object is achieved by a device having the features of claim 1 and by a method having the features of claim 8. The features of the dependent subclaims relate to advantageous embodiments.

In accordance with the invention, the device has an inner forming tool that is rotatable about a main machine axis and is mounted coaxially with the machine main axis of the device.

The inner forming tool is fastened to a holder which can be displaced in the axial longitudinal direction and which can itself be rotatably mounted with or independently of the inner forming tool.

A number of outer forming rollers, which can be moved and positioned according to a predetermined workpiece contour, engage in the region of the inner forming tool from the outside against the lateral surface of the preform. The preform is received by a pick-up device, which is preferably simultaneously a centering device that also centers the preform.

The special feature of this device is that the internal forming tool is provided with an outer contour, which allows to specify by the axial positioning of the outer forming tools relative to the inner forming tool, the axial position of the forming zone on the inner forming tool and thus due to the contouring of the inner forming tool specify the inner diameter of the workpiece by the relative axial position of the outer and the inner forming tool to each other. Due to the radial positionability of the outer forming tools, the outer workpiece diameter and thus the wall thickness at each position along the machine main axis x can be predetermined in addition to the inner workpiece diameter.

Figur 1

- zeigt schematisch drei beispielhafte Ausführungsformen des inneren Umformwerkzeugs,

Figur 2

- zeigt schematisch beispielhafte mögliche Formen von Vorform und Werkstück,

Figuren 3 und 4

- zeigen verschiedene Phasen des Umformverlaufs anhand einer beispielhaften Werkstückgeometrie und Werkzeugausführung,

Figur 5

- zeigt eine beispielhafte erfindungsgemäße Vorrichtung zu verschiedenen Zeitpunkten des Prozesses.

The invention is explained schematically below with reference to the figures:

FIG. 1

schematically shows three exemplary embodiments of the inner forming tool,

FIG. 2

schematically shows exemplary possible shapes of preform and workpiece,

FIGS. 3 and 4

show various phases of the forming process on the basis of an exemplary workpiece geometry and tool design,

FIG. 5

shows an exemplary device according to the invention at different times of the process.

The inner forming tool 9 preferably consists essentially of an inner forming roller or has at least one roller which represents the element of the forming tool 9 that acts on the workpiece 4 from the inside. The outer contour 9.2 of the inner forming tool 9 can be cylindrical, conical, convex or concave, depending on how the workpiece 4 to be formed requires it. The inner diameter of the workpiece Depending on the relative axial position of the inner forming tool 9 to the outer forming tools 8, the forming zone migrates in the axial direction on the surface contour of the inner forming tool 9. The relative position can be chosen so that at the forming zone always engages a region of the outer contour of the inner Umforwerkzeugs 9, in which the effective outer diameter of the inner forming tool 9 is equal to or minimally smaller than the desired inner diameter of the workpiece 4 at the respective position.

The inner forming roller 9 is guided axially to the position of the outer forming rollers 8 by a holder 5 centrally in the main spindle 1.1 and continuously movable in relation to the outer forming rollers 8.

If a cylindrical hollow body is to be formed with a constant inner diameter, the inner forming roller 9 and outer forming rollers 8 can be performed in a constant axial position to each other during the forming.

If, on the other hand, a hollow body having different inner diameters is to be formed, the inner forming roller 9 moves axially relative to the outer forming rollers 8 until the desired inner diameter at the respective point of the workpiece 4 is reached.

Preferably, the preform 3 can be kept centered by a driven carrier 11 of the axially movable main spindle box 1 and axially, for example, with the centering 7 of the tailstock 2, braced. For this purpose, a suitable tensioning device 14, which is preferably a pressure cylinder, may be provided.

The outer forming tools 8 may be radially guided in a housing, not shown, and may, preferably by means of CNC axes, which specify the radial position of the forming tools 8, follow predetermined travel movements. In this case, the outer contour of the desired workpiece 4 results from the radial positions at the respective axial position of the preform.

The number of possible outer forming tools 8 results from the geometric outer dimensions of the forming tools in relation to the outer diameter of the workpiece 4. The maximum diameter of the inner forming tool 9 is limited by the inner diameter of the preform.

The axial position of the outer forming rollers 8 to the inner forming tool 9, for example, by manual adjustment of the outer forming tools 8 to be matched and with each other. During the deformation, these outer forming rollers 8 in the axial direction in fixed position to each other, preferably at least as long as the desired contour of the workpiece 4 no adjustment of the axial Positions of individual forming tools to each other during the forming requires.

The clamped preform 3 can be centered by the driver 11 of the main spindle 1.1 and / or the internal forming tool 9. The tension can be effected by a pressure device 14, for example a pressure cylinder, of the tailstock 2. Preferably, the outer Umformwerkzuge 8 can be moved back to an initial position. The inner forming tool 9 is located axially in the forming position in the area of the outer forming tools 8.

The unit formed by the bias can now be moved axially by the feed device 15 of the main spindle box 1, which is preferably designed as a feed cylinder against the pressure of the pressure device 14 in the forming position. In this case, the unit may already be offset in rotation about the main machine axis or be. The inner forming tool 9 can stand axially in forming position to the outer forming rollers 8. The outer forming tools 8 can then be moved radially in the forming position.

Main spindle box 1 with rotating main spindle 1.1, preform 3 and tailstock 2 can thus form a unit which together by the axial force of the feed device 15, which is preferably a feed cylinder, with a controlled feed in the axial direction relative to the outer forming tools 8 can be moved.

As soon as the forming tools 8 are in the forming position, they can cause the material of the wall thickness W0 of the preform 3 to flow in the radial, tangential and axial directions due to the radial contact pressure of the outer forming tools 8 and the resistance of the inner forming tool 9.

The radial distance of the engaging to the inner contour of the workpiece 4 area 9.1 of the outer contour of the Innenumformwerkzeugs 9 and the outer contour of the workpiece 4 engaging portion of the outer forming tools 8 to each other results in the forming wall thickness W1 of the workpiece to be manufactured in the respective axial position of Preform 3 before. In this case, the desired outer diameter with the predetermined wall thickness W1 can form in this axial position. In this case, the inner diameter of the workpiece 4 to be produced in each axial position of the workpiece 4 is predetermined by the contact diameter 9.1 of the distance of the engaging to the contour of the workpiece 4 region of the outer contour of the Innenumformwerkzeugs 9 of the machine main axis x in the respective axial position results.

An thereby increasing length of the preform 3, the tailstock 2 in the flow direction of the formed material against the pressure of the pressing device 14, which is preferably a pressure cylinder, press back. The pressure device 14 may be designed so that the back pressure is regulated and / or controllable. It is also possible to provide a Andrückverlängerung 10, which is preferably guided centrally to the main axis.

The outer diameter of the workpiece to be manufactured with the wall thickness W1 is specified at the respective axial position of the workpiece 4 by the respective radial position and dimensioning of the outer forming tools 8. The wall thickness W1 of the workpiece 4 to be produced results at the respective axial position of the workpiece 4 through the contact diameter 9.1 of the internal forming tool 9.

This is determined by the fact that, due to the axial position of the inner forming tool 9 relative to the outer forming tools 8, a clearly defined area of the outer contour of the inner forming tool 9 acts on the inner contour of the workpiece 4 to be reshaped. Thus, the inner diameter of the workpiece 4 to be formed can be set in the respective axial position.

If the axial position of the inner forming roller 9 is changed relative to the outer forming rollers 8 during forming, the contact diameter 9.1 and thus the defined area of the outer contour of the inner forming tool 9 acting on the inner contour of the workpiece 4 to be formed changes, with the result that the wall thickness W1 of the formed workpiece 4 changes. In this case, in the example shown with an axial feed of the internal forming tool 9 with the outer contour 9.2 in the tailstock 2, a smaller inner diameter, at a feed of Innenumformwerkzeugs 9 in the direction of the main spindle 1, a larger inner diameter. Remains the axial position of the internal forming tool 9 in relation to the outer forming rollers 8 fixed, results as a constant inner diameter of the contact diameter 9.1 of the internal forming tool. 9

The inner diameter is smaller when the contact diameter 9.1 is smaller, that is, the axial position of the Innenumformwerkzeugs 9 relative to the axial position of the outer forming tools 8 changes such that the forming zone on the outer contour of the inner forming tool in a region with smaller, on the Shapes inner contour of the workpiece 4 attacking, effective tool diameter. As a result, a greater wall thickness can be formed without the outer forming rollers 8 changing their radial position.

In contrast, change the outer forming rollers 8 their radial position to a smaller outer diameter formed in accordance with the resulting from the new axial relative position of Innenumformwerkzeugs 9 due to the outer contour of the inner forming tool 9 inner diameter of the workpiece 4, then with a constant wall thickness, a smaller outer diameter than before Changing the radial position of the outer forming rollers 8 and the axial position of the inner forming roller 9 are formed.

The inner diameter becomes larger when the contact diameter 9.1 becomes larger, ie, the axial position of the inner forming tool 9 relative to the axial position of the outer forming tools 8 changes such that the deformation zone on the outer contour of the inner forming tool in a region with greater on the inner contour of the workpiece 4 acting effective tool diameter shifts. As a result, the molded wall thickness W1 can be reduced without the outer forming tools 8 changing their radial position.

If, on the other hand, the outer forming rollers 8 also change their radial position to a larger shaped outer diameter corresponding to the inner diameter of the workpiece 4 resulting from the new axial relative position of the inner forming roller 9 due to the outer contour of the inner forming tool 9, then with a constant wall thickness a larger outer diameter than before Changing the radial position of the outer forming rollers 8 and the axial position of the inner forming roller 9 are formed.

These described basic movements can be lined up in any desired manner, so that any sequences of the described cylindrical or conical contour profile sections 3.1 arise. In addition, the formation of any conical and / or convex contours is possible by superposition of the described basic motion sequences.

Once the end of the preform 3 is reached, the outer forming tools 8 can go back to the starting position. Subsequently, the unit of main spindle box 1, tailstock and finished part 4 can go back to the unloading position. The finished workpiece 4 can now be relaxed and removed.

It is also possible for the inner forming tool 9 to have a shape on the inner contour of the workpiece 4, which makes it possible to contour the inner contour not only axially but also in the circumferential direction. Such circumferential inner contouring 4.1 can be, for example, axially extending inner ribs. One possibility of realizing such an inner forming tool is a forming tool, preferably a roller, with a surface contoured on the inner contour of the workpiece 4 in the circumferential direction.

1. 1. Hohlkörper mit und ohne einseitigen Boden, mit gleichbleibenden Außen - und Innendurchmesser,
2. 2. Hohlkörper wie unter 1, jedoch mit ein oder mehreren zylindrischer Verdickungen bei gleichbleibendem oder sich änderndem Außendurchmesser,
3. 3. Hohlkörper wie unter 1, jedoch mit konischem, konkaven und/oder konvexen Verläufen der Wanddicken bei gleichbleibendem sich änderndem Außendurchmesser,
4. 4. Hohlkörper wie unter 1 bis 3, mit einer Konturierung in Umfangsrichtung, beispielsweise axial verlaufenden Innenrippen.

Due to the axial movability of the inner forming tool 9 relative to the outer forming tools 8, the following inner contours are possible:

1. 1. hollow body with and without one-sided bottom, with constant outer and inner diameter,
2. 2. Hollow body as in 1, but with one or more cylindrical thickening with a constant or changing outer diameter,
3. 3. Hollow body as in 1, but with conical, concave and / or convex profiles of the wall thicknesses with a constant changing outer diameter,
4. 4. Hollow body as under 1 to 3, with a contouring in the circumferential direction, for example, axially extending inner ribs.

Claims (10)

Device for processing a preform (3), with at least one outer forming tool (8), which can be radially positioned or moved radially,
characterized,
in that an internal forming tool (9) is arranged coaxially with the main machine axis (x) of the main spindle (1.1) and can be axially moved and / or axially positioned relative to the axial position of the outer forming tools (8). Device according to claim 1,
characterized,
that the Innenumformwerkzeug (9) during the forming of the preform (3) relative to the position of the outer forming tools (8) moved axially or can be axially positioned. Apparatus according to claim 1 or 2,
characterized,
that the inner mold tool (9) has an axially profiled, in particular a spherical, outer contour. Device according to one of the preceding claims,
characterized,
that the outer contour (9.2) of the inner mold (9) comprises one or a plurality of cylindrical paragraphs and / or one or a plurality of conical, concave and / or convex transitions. Device according to one of the preceding claims,
characterized,
that the inner forming tool (9) having a contoured engaging surface in the circumferential direction on the inner contour of the workpiece. 4 Device according to one of the preceding claims,
characterized,
in that the inner forming tool (9) is composed of a plurality of outer profiles and / or contours. Device according to one of the preceding claims,
characterized,
that the Innenumformwerkzeug (9) has at least one forming roller, which is preferably mounted coaxially to the machine main axis, and / or the Außenumformwerkzeuge (8) comprises forming rollers. Method for producing workpieces from a preform (3), in particular by means of a device according to one of the preceding claims, in which a preform (3) is formed by the interaction of an inner and at least one outer forming tool, the pressure being between the outer forming tools (8) and the inner forming tool (9) on the shell of the preform (3) causes the material to flow,
characterized,
that when the preform rotates (3) this assumes a predetermined by external forming tools (8) and an internal forming tool (9), the wall thickness through the Radial position of the outer forming tools (8) and the inner forming tool (9) is determined to each other. Method according to claim 8,
characterized,
that with rotating preform (3) of the wall thickness profile of the shape to the workpiece (4) (9.1) of the Innenumformwerkzeugs (9) to one another is determined by the distance between the outer forming rollers (8) and the contact diameter. Method according to claim 8 or 9,
characterized,
that with rotating preform (3) of the wall thickness profile of the workpiece to be formed from the relative radial position of the outer forming tools (8) to the contact diameter (9.1) of Innenumformwerkzeugs determined, the contact diameter is due to the outer contour of Innenumformwerkzeugs (9) of the gives relative axial position to the outer forming tools.

Images