Process for producing a metal component by flow forming

Abstract

Method for producing a component from metal, in which a metal preform having at least one tubular region is first produced, the component then being produced by flow-forming the tubular region of the preform, characterized in that the preform is produced entirely by 3D metal printing and is machined before flow-forming.

Description

[0001] The invention relates to a method for producing a component from metal, in which a metal preform having at least one tubular region is first produced, wherein the component is subsequently produced by flow-forming the tubular region of the preform.

[0002] In flow forming, hollow bodies are produced by forming a preform, usually tubular, or a preform having at least one tubular section. The preform is pushed onto a mandrel and clamped in a torsion-proof manner. One or more, usually three, rotating flow rollers then press radially onto the rotating preform, causing the material to expand in the axial direction. The wall thickness is reduced and the workpiece lengthened. The final state is brought about by compressive stress. The pressure exerted on the material increases the strength of the material and also lengthens the workpiece as the wall thickness becomes thinner. This leads to improved material properties, higher load-bearing capacity, and a longer service life than with components manufactured by machining. In addition, very precise components can be manufactured using flow forming. For example,Drive shafts for engines or hydraulic cylinders are manufactured using flow-forming. The work hardening of flow-forming technology allows for wall thicknesses very close to the theoretical minimum, resulting in extremely low component weights and high precision.

[0003] The starting product for flow forming is a preform that is tubular or at least has an area that can be formed by flow forming. Depending on the component to be manufactured and the material properties or material compositions (metal alloys) required for the component, tubes are used as the preform, which are machined before flow forming in order to create the initial dimensions required for the respective component. If no suitable tubes are available as a preform, the preform is produced by machining from solid material or by forging. The latter variants are generally used when special material compositions are required for which tubes are not available as preforms or semi-finished products, or when components with a more complex geometric shape are to be produced.It is evident that the production of the preform for the actual flow forming is both material-intensive and technically complex.

[0004] From DE 42 05 675 A1 a method with the features of the preamble of patent claim 1 is known, in which the preform is produced by drilling.

[0005] It is generally known to produce components using 3D printing, not only from plastics, but also from metals or metal alloys. Such components are usually prototypes or components for small series. In principle, a metal wire or metal powder can be used as the starting material for 3D metal printing. The component produced using 3D metal printing is then post-processed if necessary, usually by machining the surface. DE 10 2013 110 417 A1 discloses a metal powder for powder-based manufacturing processes and a method for producing a metallic component from metal powder using 3D metal printing. Another 3D metal printing method is known from EP 0 946 325 B1.

[0006] From the unpublished document DE 10 2016 111 047 B3, a method and a system for the combined additive and forming production of a metallic molded body are known, wherein the molded body is built up layer by layer, in particular by melting a wire- or powder-like metallic material and applying the molten material to an already completed layer or a build platform, wherein pressure-forming processing of the already completed layers takes place during production. From DE 10 2014 014 202 A1, a method is known in which a preform made of a sheet-like starting material is used as the starting product, wherein this preform is not produced by 3D printing. This sheet-like preform is then provided with local material accumulations by means of additive processes, preferably at specific locations, which are then formed by means of incremental sheet-metal forming.

[0007] The object of the invention is to be able to produce components by flow forming in a much more material-saving, economical and flexible manner.

[0008] This object is achieved according to the invention in a method of the type described at the outset in that the preform is produced entirely by 3D metal printing and is machined before flow forming.

[0009] It has surprisingly been discovered that it is possible to produce a preform suitable for subsequent flow-forming using 3D metal printing. Such a preform can be formed by flow-forming at least one tubular region without causing damage to the material structure. Rather, the flow-forming process homogenizes and strengthens the metal structure of the preform while simultaneously reducing the wall thickness, making it possible to produce components with material properties that were previously unimaginable using 3D metal printing.This allows components to be manufactured using flow-forming with significantly less material, and components with more complex shapes can also be created, for example components with one or more tubular areas that are flow-formed and adjacent areas that already receive their final shape through metal pressure, possibly with minor post-machining.

[0010] In a preferred embodiment, it is possible for the preform to be manufactured, at least in certain areas, in multiple layers from different materials using 3D metal printing. This allows specific material properties to be achieved at specific locations on the finished workpiece, depending on the functional areas, due to increased work hardening depending on the respective function.

[0011] According to a first preferred embodiment, wire is used as the starting material for 3D metal printing. Bead- or ring-shaped sections are formed layer by layer and welded together. The surface of such a preform is irregular and generally requires material removal by machining prior to flow forming, albeit with only minimal material loss.

[0012] According to a second preferred embodiment, metal powder is used as the starting material for 3D metal printing. This printing process is particularly suitable when metal compositions are required that are not available as wire material.

[0013] The preform is machined prior to flow-forming. Machining can also be performed on areas of the preform that are not flow-formed but are intended to receive a shape that cannot be achieved by flow-forming.

[0014] In order to influence the material properties of the component to be produced, it can additionally be provided that the preform is subjected to a heat treatment before and / or after flow forming.

[0015] The invention is explained in more detail below with reference to the drawing, which shows Fig. 1 a preform produced by 3D metal printing in longitudinal section, Fig. 2 the preform according to Fig. 1 in perspective view, Fig. 3 the preform after Fig. 1 in longitudinal section after machining, Fig. 4 the preform after Fig. 3 in perspective view, Fig. 5 the preform after Fig. 3 in longitudinal section during flow forming, Fig. 6 The finished component after flow forming in perspective view.

[0016] The method according to the invention for producing a metal component is generally suitable for any component that can be produced by flow-forming. The drawings illustrate the production of a hydraulic cylinder 1 as the component to be produced.

[0017] In a first process step, a preform 2 is produced using 3D metal printing. In the example, wire was used as the starting material for 3D metal printing, which is welded layer by layer during printing. Alternatively, metal powder can also be used as the starting material for 3D metal printing.

[0018] Since wire was used as the starting material for the production of preform 2 by 3D metal printing, preform 2 has a surface that is not smooth but caterpillar-shaped; this caterpillar-shaped surface structure is designated 3.

[0019] The preform 2 produced in this way has, in the exemplary embodiment, a central tubular region 4, which is subsequently to be formed by flow-forming. Adjacent to the tubular region 4, the preform 2 has, in the sense of Fig. 1 on the left a connection area 5 and two fastening areas 6, 7 and on the right adjacent to the tubular area 4 further areas, namely hydraulic connection areas 8, 9 and a thickened annular end area 10.

[0020] The preform 2 thus produced is processed in a second process step according to Fig. 3 and Fig. 4 machined. To enable the subsequent flow-forming process, the surface of the tubular area 4 is machined, for example by turning, to obtain a flat surface in the tubular area 4. For this purpose, in principle, only the caterpillar-shaped surface structure 3 in the tubular area 4 is removed. In the other areas, the respective caterpillar-shaped surface structure 3 is also removed by machining, for example milling or turning, and the required functional parts for the finished component, i.e., the hydraulic cylinder 1, are thereby directly formed, namely the connection area 5, which is additionally provided with a transverse bore 11, as well as the fastening areas 6, 7, the hydraulic connection areas 8, 9, and the thickened annular end area 10.

[0021] In addition, the preform 2 is also machined, preferably by turning, in its inner hollow region 12, which also has a caterpillar-shaped surface structure 3 on the inside due to the process, in order to obtain a smooth surface in the inner hollow region 12 as well.

[0022] The preform 2, which has already been processed in this way, is then pushed onto a mandrel 13 and by means of pressure rollers 14, of which Fig. 5 only one is shown. For this purpose, the preform 2 is clamped in the usual way with the mandrel 13 in a rotationally secure manner, then several, usually three, spinning rollers 14 rotating at the same speed press radially on the rotating preform 2, so that the material deflects in the axial direction. In the process, the wall thickness is reduced and the tubular area 4 of the preform 2 is lengthened. The thus extended area is in the Fig. 5 and Fig. 6 marked 15.

[0023] At the end of the flow forming process, the finished component, namely the hydraulic cylinder 1, is completed. Fig. 6 shown.

[0024] Of course, the invention is not limited to the illustrated embodiments. Further embodiments are possible without departing from the basic concept. Thus, other components suitable for flow-forming can also be produced using the method according to the invention. The prerequisite is that the preform to be produced by 3D metal printing has at least one tubular region that can subsequently be flow-formed. To influence the material properties of the component to be produced, the preform can also be subjected to heat treatment before and / or after flow-forming. List of reference symbols: 1 hydraulic cylinder 2 preform 3 caterpillar-shaped surface structure 4 tubular area 5 Connection area 6 Mounting area 7 Mounting area 8 Hydraulic connection area 9 Hydraulic connection area 10 End area 11 Cross hole 12 hollow area 13 Thorn 14 Pressure roller 15 Area

Claims

[1] A method for producing a component from metal, in which a metal preform having at least one tubular region is first produced, the component then being produced by pressure-forming the tubular region of the preform, characterized by that the preform is manufactured entirely by 3D metal printing and machined before flow forming. [2] Method according to claim 1, characterized by that the preform is manufactured at least partially in multiple layers from different materials by 3D metal printing. [3] Method according to claim 1 or 2, characterized by that wire is used as the starting material for 3D metal printing. [4] Method according to claim 1 or 2, characterized by that metal powder is used as the starting material for 3D metal printing. [5] Method according to one or more of claims 1 to 4, characterized bythat the preform is subjected to heat treatment before flow forming. [6] Method according to one or more of claims 1 to 5, characterized by that the preform is subjected to heat treatment after flow forming.

Images