WO2019243088A1

WO2019243088A1 - Method and device for the primary forming of metal parts

Info

Publication number: WO2019243088A1
Application number: PCT/EP2019/064987
Authority: WO
Inventors: Bernd Zapf; Benjamin Grübel; Heinz Brujmann; Sebastian Knaus; Wolfgang Wenzler
Original assignee: Gebr. Heller Maschinenfabrik Gmbh; August Wenzler Maschinenbau GmbH
Priority date: 2018-06-19
Filing date: 2019-06-07
Publication date: 2019-12-26
Also published as: DE102018114661A1

Abstract

The method according to the invention is particularly suitable in the case of variants of component parts (16, 17), which up to now have been produced by casting and which have a common base part (14) at their origin. The base part (14) is selectively enhanced by the additive forming of additional structures (18, 19), thereby producing by a hybrid processing method. Therefore, the number of required casting mould variants can be reduced and production can be carried out in a more economical and flexible way. Irrespective of the final form of the component part (16 or 17), core or basic features are manufactured by casting and the finished component part (16, 17) is completed using the hybrid method. It can be mass produced both in very small and very large production runs. The method is particularly suitable for producing frame components in the automotive industry where, for example, fastening points of all types in a vehicle very often constitute component part variants which lead to disproportionate expenditure and complicated logistics in terms of the foundry process. Other possible applications are in the construction of electric motors, the aircraft industry, energy generation, mould making and in other industrial fields.

Description

Method and device for the primary shaping of metal parts

The invention relates to a method for the formation of metal parts in a hybrid working method and a device therefor.

For the primary shaping of metal objects, various casting processes are known, such as the sand casting process. The casting mold must contain all structural details, including a dimension allowance if necessary, for later machining.

As an alternative to master molding processes for the provision of metal parts, methods are known with which these can be produced, for example, by machining processes from semi-finished products, such as rods, tubes, plates, sheets or the like. Parts manufactured in this way can also be joined using joining processes, e.g. Welding can be connected to a desired component.

Furthermore, additive processes are known in which the desired final shape is achieved by a combination of an original molding process with material-processing.

[0005] DE 10 2014 014 202 A1 discloses a method for the combined production of components by means of incremental sheet metal forming and additive and subtractive methods in one setting. To carry out the method, a sheet metal part is formed using a tool for incremental sheet metal deformation, for example in the form of a printing stylus, with an additive being used before and / or during or after this processing Material application process Material accumulations are achieved. Laser cladding is particularly recommended as an additive method for material application. To perform the same, a nozzle is provided through which metal powder is supplied to the application site, which is welded onto the sheet metal part by means of a laser beam. With this proposal, the production of sheet metal parts can be made more flexible and simplified, especially with demanding geometries. In addition, the accumulations of material applied by means of build-up welding can be reworked, i.e. subtractively, especially to increase the dimensional and shape accuracy.

The deformation of the sheet metal part during the described generative manufacture of the part in a single clamping leads to stresses which may only be released after the sheet metal part has been unclamped, which means that it can be used in the production of sheet metal parts by the named method accuracy problems can arise.

It is an object of the invention to provide an improved method for producing metal parts in at least one aspect compared to the prior art.

This object is achieved with the method according to claim 1 and the device according to claim 14:

In the inventive method for shaping metal parts, a base part is provided in a first step, for example by casting or forging.

The cast or forged part can, if necessary, be subjected to a first rough preprocessing, for example for removing a cast skin, deburring, removing sprues or the like. However, after the base part has been formed by casting or forging, any (further) plastic deformation of the base part does not occur. The base part represents a partial volume of a desired component and consequently has only a subset of the structural features of the desired finished component. However, there are no further structural features on the base part, preferably those which are to be formed on peripheral sections of the component. An additional structure to create additional structural features is then formed on the base part in a further manufacturing step in an additive manufacturing process. This is typically done by melting parts of a metal supply as well as portionwise or continuous attachment and letting these parts solidify on the base part. This process can take place intermittently or continuously. The additive manufacturing step thus carried out increases the volume of the workpiece being created.

The method also includes the material-removing, ie subtractive processing of the additional structure generated in the additive method. In addition, before, at the same time or afterwards, the base part itself can be subjected to machining in order to preferably finish the further structural features on the additively attached component sections and / or on the base part. The structural details available on the base part and on the additional structures are e.g. around features defined in the component drawing. In any case, additional structures are not single-layer or multi-layer weld seams for connecting the base part to other preformed components.

[0011] This concept provides a highly efficient method of manufacturing metal components that opens up new degrees of design freedom. In the case of casting processes, in particular gravity casting processes, such as sand casting processes or the like, the construction must ensure that the wall thickness is as uniform as possible and material Avoid accumulations. With the method according to the invention, a thick-walled base part can be produced, for example in the forging or casting process, onto which filigree additional structures are molded in the additive manufacturing step.

Preferably, the base part produced in the casting or forging process is inserted and clamped in a workpiece clamping device before the additive formation of the additional structure, after which in this a clamping, in particular without further mechanical (plastic) deformation of the base part, in this a clamping both the additive formation of the at least one additional structure and the material-removing processing on the additional structure and / or the base part is carried out. This enables the safe and inexpensive production of dimensionally stable metal components. The metal materials of the base part and the additional structure can be the same or different. It can be pure metals or metal alloys, the metal alloys preferably being the same or having at least the same base metal. For example, the first and the second metal material can each be aluminum alloys, which have the same or different mechanical properties, but are in any case weldable to one another.

The additive manufacturing process is preferably a welding process in which the second material is held ready as a wire, which is itself held ready as a melting electrode, for example. In the preferred welding method, the arc burns between the wire and the base part or welding beads already generated in previous work steps. It is thus formed on the surface of the base part or on the surface of already solidified welding beads, at the welding point a weld pool with which the free end of the melting wire is brought into contact periodically, at least in a preferred manufacturing process. In this way, the metal drops forming on the free end of the wire are checked and transferred to the base part in a targeted manner, so that the formation of welding smoke and welding spatter is minimized. This procedure allows the additive manufacturing step to be carried out in one setting in a machine tool, which simultaneously or subsequently effects the machining of the base part and / or the additional structure.

The machine tool receives the workpiece on a workpiece carrier, which is preferably pivotally mounted about two axes, which together form an angle, preferably a right angle. The two axes can be aligned horizontally, but preferably one axis is horizontal and one axis is perpendicular to it - vertical in the zero position. The machine part, which can be pivoted about the horizontal axis, preferably carries a rotary table with a workpiece carrier, the rotary table defining a rest position, a vertical axis of rotation. The method is preferably carried out in such a way that the base part is spatially positioned during the production of the additional structure in such a way that that surface area of the base part to which the metal material from the second supply is attached is kept horizontal. So relatively large material areas can be applied to the base component or additional structures that have already been generated on the base component. The liquid metal is held in the weld pool by gravity.

[0015] Preferably, the base part is attached during the additive attachment of the additional structure, for example by loading heating or cooling, kept at a temperature which allows the attachment of the additional structure to the base part with minimal distortion thereof. For this purpose, it may be useful to preheat the base part. However, it can also be expedient to cool the base part before and / or during the attachment of the additional structure in order to keep it at a temperature which is below a structural transformation temperature. The microstructure transformation temperature can be a temperature at which the mechanical properties of the material of the base part, for example its hardness, change. If the base part consists of an aluminum material, it may be expedient to keep the base part at a temperature below 180 °.

[0016] The concept according to the invention permits the primary shaping of the additional structure and the mechanical finishing of the same in a single clamping in a single processing machine in the same working area of the same. The welding head required to carry out the additive manufacturing step, or the at least one tool required to carry out the material-removing machining step, can be kept in a tool magazine. A tool changer transports the tool and the welding head between the tool magazine and the processing machine. Several tool magazines can be provided and several tools as well as several welding heads can be kept ready. The tools are preferably tools with at least one geometrically defined cutting edge, in particular milling cutters.

It is possible to complete the material order of the additive manufacturing step by superimposing a number of welding beads and then to connect a material-removing manufacturing step. It is however, it is also possible to switch one or more times between additive manufacturing steps and material-removing manufacturing steps. As a result, each additive manufacturing step always has a defined starting area, which reduces dimensions and increases material efficiency and thus the speed of work.

However, it is also possible to control the material application in accordance with the speed of movement of the welding head (and / or the workpiece) and in accordance with the quantities of material to be filled. This can be done by specifying the speed of the material application in the additive manufacturing step in accordance with the geometry.

The inventive method is particularly suitable for the production of component families whose geometry allows the division into a base part, which is common to all components of the component families, and individual additional structures. This means that each component of the component families can be created from one and the same base part by molding the individual additional structures in the additive manufacturing process. An additive manufacturing process is understood to mean all generative shaping processes in which the shape of the additional structure is generated from at least in a transition phase of informal material. The mere attachment of prefabricated elements to the base part, such as would be the attachment of preformed tabs, is not understood as an additive manufacturing process.

The manufacturing method according to the invention makes it possible to keep basic parts in stock and to produce individual components quickly on demand. To carry out this method, the processing machine has at least two processing programs in its machine control, each processing program having because a different component variant to be produced from the same base part is assigned.

The device according to the invention allows the method according to the invention to be carried out. It combines a processing machine, such as that used for machining workpieces, with a welding machine to operate the welding head picked up by the working spindle of the processing machine. Two axes of the workpiece holder, which are at an angle to one another, allow that by the appropriate program control

Always keep the weld head generated on the base part horizontal or almost horizontal during additive manufacturing. The welding head is held so that the

Wire feed direction from top to bottom and thus essentially vertical. The wire feed direction is understood to mean the direction in which the wire moves at its end adjoining the arc. Thus, the arc burning between the workpiece and the wire and the gas outlet direction of an assigned protective or active gas nozzle are essentially vertical, but in any case oriented towards the horizontal weld pool.

Further details of advantageous embodiments of the invention emerge from the drawing, the description or the subclaims. Show it:

1 shows a casting mold and a metal supply for producing a base part in the casting process, in a schematic representation,

[0023] FIG. 2 a part produced in the casting process,

[0024] FIG. 3 shows a component produced using the base part according to FIG. 2, in a first variant, in a perspective view, [0025] FIG. 4 shows another component produced using the base part according to FIG. 2, in a perspective view,

FIG. 5 shows a processing machine which is set up to generate an additive structure on the base part, in a schematic side view,

FIG. 6 the processing machine according to FIG. 5, set up for machining the base part and / or an additive structure,

Figure 7 shows the base part and a welding head in a schematic diagram illustrating the creation of an additive structure.

In Figure 1, a first supply 10 of a first metal material 11 is illustrated to illustrate the manufacture of a base part, which is to be filled into a mold 12. The casting mold 12 is preferably a casting mold for gravity casting, for example a sand mold, which encloses a cavity 13 which corresponds to the shape of the base part 14 to be produced (see FIG. 2). In addition, the cavity 13 can have sections 15, for example for the sprue or for the escape of air. In principle, not only sand casting processes, but also other casting processes can be used to produce the base part 14, for example permanent mold casting, centrifugal casting, pressure casting, investment casting or the like. The metal material 11 may be any castable metal, for example an iron-based metal alloy or an aluminum-based metal alloy.

Figures 3 and 4 illustrate two different components 16, 17, each in a perspective schematic representation, which are based on the same base part 14. At least one additional structure 18 (and possibly further additional structures 18a, 18b, 18c) is provided on the first component 16 according to FIG. 3 and is initially missing from the base part 14. Likewise, at least one additional structure 19 (and, if appropriate, further additional structures 19a, 19b, 19c), which is not part of the base part 14, is provided on the second construction part 17. The additional structures 18, 19 differ from one another in position and / or

Size and / or shape. The same can be done for any additional structures 18a, 19a; 18b, 19b; 18c, 19c apply, which differ in number, size, shape and position or can also match each other in whole or in part.

The components 16, 17 thus form a component family with a common base part 14 and different Additional structures 18, 19. The additional structures 18, 19 (as well as 18a to 18c and 19a to 19c) preferably consist of the same metal material as the base part 14. If necessary, however, the material properties can also be chosen differently. If the first metal material 11 is, for example, an aluminum alloy, the additional structures 18, 19 (such as 18a to 18c and 19a to 19c) can likewise consist of aluminum material of the same or different alloy composition. The additional structures 18, 19 (and also 18a to 18c and 19a to 19c) can consist of the same metal material or of different metal materials. The additional structures 18, 19 have defined shapes and are dimensionally defined and their shape in the component drawing. Pure weld seams for connecting two or more prefabricated components are not additional structures in the sense of this invention.

The component 16 or 17 is produced starting from the base part 14 in each case on a machine 20 schematically illustrated in FIGS. 5 and 6 in its working space 21. The machine tool 20 has one for receiving the base part 14 (FIG. 5) Workpiece carrier 22, which is preferably tiltable about a horizontal pivot axis 24 and can be rotated about a vertical axis of rotation 23. The two axes of rotation 23, 24 preferably form a right angle with one another. They can cross one another or be arranged at a vertical distance from one another. In addition, the workpiece carrier 22 may be movable in one or more directions, for example in a horizontal direction 25. When the workpiece carrier 22 is pivoted about the pivot axis 24, the axis of rotation 23 tilts to the vertical, that is to say it is always perpendicular to the workpiece carrier. The processing machine 20 also has a work spindle 26, which includes a spindle motor and a tool holder 27 driven by the latter. The drive motor is controlled by a control device 28, for example in order to assume a fixed rotational position or to run at a given speed.

For the spatial positioning of the work spindle 26, a slide 29 is used, which can be moved, for example, in a vertical direction 30 and / or in other directions. In addition, the work spindle 26 is preferably held pivotably about a horizontal axis 31. Alternatively, the work spindle 26 can be oriented essentially vertically on the slide 29.

The processing machine 20 also includes at least one tool magazine 32, which is used to hold tools, such as the tool 33. The tool 33 can be a drill, milling cutter or a similar tool with at least one geometrically determined

Be a cutting edge that can be used for machining a workpiece when it is inserted into the tool holder 27.

In addition, at least one welding head 34 can be kept in the tool magazine 32 or another separate tool magazine, which can also be inserted into the tool holder 27. To transfer the tool 33 and possibly other tools or the

Welding head 34 and possibly other welding heads in the tool holder 27 and for leading them out and transferring them back into the tool magazine 32 is a tool changer 35. If the work spindle 26 is oriented vertically or can be transferred into a vertical position, the shaft of the welding head 34 and that of it specified wire feed direction be the same. Is the work spindle 26 not convertible into a vertical position, it is advantageous if the shaft of the welding head is oriented transversely to the wire feed direction, so that the wire feed direction is still vertical when the work spindle is not vertical, for example horizontal. A straight welding head can also be combined with an angle adapter.

The processing machine 20 is assigned a welding device 36, which contains a supply of a second metal material, for example in the form of a wire reel. Egg ne not further illustrated feed device serves to weld wire 34 through the wire 38

Feed hose 39. In addition, the welding device 36 contains a welding current source 40 which is connected to the wire 38 with a first pole and to the base part 14 or its workpiece carrier 22 with a second pole in order to close the circuit. The welding device 36 also includes a gas delivery device, from which gas is supplied to the welding head 34 via the hose 39 or a separate hose, not shown. This gas can be an active gas, e.g. CO2, or a non-reactive gas (inert gas) or another protective gas.

The control device 28 contains at least one, but preferably two, symbolically illustrated in FIG. 5, machining programs 41, 42, with the aid of which they both the movements of the workpiece carrier 22 and the movements of the work spindle 26 and the tool changer 35 and the work of the Welder 36 controls. The two machining programs 41, 42 each encompass all work steps both for generating the additional structure 18 and 19 by means of the welding head 34 and for the subsequent material-removing processing of the base part 14 and / or the additional structure 18 and 19 by means of the tool 33 (or other cutting tools). The following description of the manufacture of component 16 applies accordingly to the manufacture of construction part 17:

To produce the component 16, the base part 14 is first produced in a casting step in a casting process. Alternatively, this base part 14 can also be produced in another shaping process, such as a forging process. The base part 14, if necessary freed of sprues and burrs and, if necessary, cast skins and possibly also any excess material is subsequently clamped to the workpiece carrier 22, which it no longer leaves until its completion and in which it remains clamped. The further production of the component 16 according to FIG. 5 thus begins with the replacement of the welding head 34 in the working spindle 26. The machining program 41 now carries out a material application operation at least at one point provided for the base part 14, as illustrated in FIG. 7. For this purpose, the welding head leads the wire 38 to the base part 14 in order to build up beads 43 in several layers there. This forms an arc 44 between the wire 38 and the component 14 or welding beads 43 present thereon, which on the one hand forms a molten bath 45 on the base part 14 or the welding bead (s) 43 located thereon and on the other hand to form liquid drops 46 leads to the free end of the base part 14 facing the welding wire 38. The drop 46 represents a molten portion of the second metal material present in wire form.

During the production of the weld beads 43, the workpiece carrier and with it the base part 14 are each held by targeted movement about the axes of rotation 23, 24 such that the weld pool 45 is horizontal. This can a relatively large-volume weld pool can be generated without the risk of it leaking.

The wire 38 is, as the arrow 47 indicates, continuously conveyed. An additional drive 48 is provided in the welding head 34, which gives the wire 38 an additional movement which can be understood as a "pilgrim step movement". The wire 38 oscillates at a high frequency, preferably more than 10, preferably more than 50 Hz, preferably more is moved back and forth as 100 Hz, so that drops 46 forming at its end are brought into contact with the weld pool 45 and thus transferred into it in a controlled manner. The welding head 34 is continuously moved in a welding manner along a contour on which the additional structure is located 18 (and 18a to 18c) After this structure has been built up, the welding head 34 is transferred by means of the tool changer 35 into a tool magazine, for example the tool magazine 32, and the tool 33 is inserted into the work spindle 26 for this purpose, as shown in FIG can the welding head 34 by means of the work spindle 26 directly, that is, in the so-called pick-up method, in a W tool magazine are transferred.

With the tool 33 and possibly other tools, the component 16 can now be finished under the further direction of the machining program 1 and then removed as a finished part from the machine tool 20.

If another component such as component 17 is to be produced, this is done under the control of the second machining program 42, which is also kept in the control device 28.

The processing machine 20 can be formed by a suitable processing center or a suitable other machine tool, the workpiece carrier 22nd This machine is equipped not only to mechanically clamp the workpiece, but also to make electrical contact, so that the welding current can be returned from the working space 21 to the welding machine 36 via the two round axes (23, 24). The welding device 40 may be part of the processing machine 20 or a separate device. The production of the finished contour by means of cutting tool 33 can take place after the material application work has been completed by welding head 34 or alternately with it. The latter is particularly useful if the processing machine 20 has several, for example two work spindles, one of which is equipped with the welding head 34 and the other with the cutting tool 33. By alternating material application and material removal, that is, intermediate machining between several material application cycles, thermal stresses can be partially reduced.

The inventive method is particularly suitable when variants of components 16, 17, which have long been produced by casting, can be traced back to a common base part 14. The base part 14 is ge supplemented by additive molding of additional structures 18, 19, whereby a hybrid machining process is created ge. This can reduce the number of casting mold variants required and production can be carried out more economically and flexibly. Irrespective of the final expression of component 16 or 17, core or basic features are produced by casting and the addition to the finished component 16, 17 is carried out by the hybrid method. Both very small and very large lots can be produced in series. The method is particularly suitable for frame parts in the automotive industry, where, for example, attachment points of any kind in the vehicle very often represent component variants that result in disproportionate expenditure and complicated logistics in terms of foundry technology. Further fields of application can be found in electric motor construction, in the aircraft industry, in energy generation, in mold construction and in other industrial fields.

Reference characters:

10 first stock of a metal material

11 first metal material

12 mold

13 cavity

14 base part

15 more channels of the mold

16 first component

17 second component

18 additional structure (as well as 18a, 18b, 18c)

19 additional structure (as well as 19a, 19b, 19c)

20 processing machine

21 work space

22 workpiece carriers

23 vertical axis of rotation of the workpiece carrier 22

24 horizontal axis of rotation of the workpiece carrier 22

25 horizontal axis

26 work spindle

27 tool holder

28 control device

29 sledges

30 vertical direction

31 swivel axis

32 tool magazine

33 tools

34 welding head

35 tool changer

36 welding machine

37 second stock of a metal material

38 wire

39 hose

40 welding power source Machining program for producing component 16 Machining program for producing component 17 welding beads

Electric arc

melting bath

drops

arrow

accessory drive

Claims

Claims:

1. A process for the primary shaping of metal components, with the following steps:

Providing a cast or forged part as a base part (14), which consists of a first metal material and is a partial volume of a desired finished component (16, 17),

Providing a supply (37) of a second metal material,

Melting portions (46) of the portion (37) of the second metal material in portions and attaching and solidifying these parts to the base part (14) with multiple superimposition to additively form an additional structure (18) on the base part (14),

Material-removing processing of the additional structure (18) and, if necessary, the base part (14), which complements the volume of the base part (16, 17).

2. The method according to claim 1, characterized in that for the production of the base part (14) a casting mold (12) is provided that the first supply (10) molten liquid first metal material as a whole and at least partially in the casting mold (12) fills is that the metal material in the casting mold (12) is cooled, at least until it solidifies and forms a casting, and then used further as the base part (14), the casting process preferably being a gravity casting process and, more preferably, the casting mold ( 12) is a sand mold.

3. The method according to any one of the preceding claims, characterized in that the base part (14) before the additive formation of the additional structure (18) in a workpiece clamping device (22) is inserted and clamped in this, after which in this on both the additive training the additional structure (18) and the material-removing machining can be carried out.

4. The method according to any one of the preceding claims,

characterized in that the first metal material and the second metal material are metals or metal alloys which can be welded to one another, wherein, preferably, the first and second metal materials are the same metals or metal alloys which have the same base metal.

5. The method according to any one of the preceding claims,

characterized in that the base part (14) and the additional structure (18) have different wall thicknesses.

6. The method according to any one of the preceding claims,

characterized in that the second metal material of the second supply is kept ready as wire (38) and that a welding process is used for the additive formation of the additional structure (18), in which the second supply is continuously produced by means of a

electric arc (44) is melted.

7. The method according to claim 6, characterized in that the wire (38) formed by the second metal material of the second supply as a melting electrode is provided, which is supplied with a welding current via a welding current source (40) in order to maintain an arc (44) between the wire (38) and the base part (14) or weld beads (43) formed thereon, and that, preferably that free end of the wire (38) is brought into contact periodically with a melted area (45) of the base part (14) or egg ner already formed on this welding bead (43).

8. The method according to any one of the preceding claims,

characterized in that the base part (14) is spatially positioned during the production of the additional structure (18) such that that surface area of the base part (14) to which metal material from the second supply is attached is kept horizontal.

9. The method according to any one of the preceding claims,

characterized in that the additive generation of the additional structure (18) and the material-removing machining thereof are carried out in the same working space (21) of a processing machine (20).

10. The method according to any one of the preceding claims,

characterized in that a welding head (34) is used to carry out the additive manufacturing step and a tool (34) with a geometrically defined cutting edge, in particular at least one milling cutter (33), both of which are in a tool magazine (32 ) held ready and by means of a tool changer (35) in the work spindle (26) of a machine tool (20) can be replaced and exchanged.

11. The method according to any one of the preceding claims,

characterized in that the material order of the additive manufacturing step and the material removal of the material-removing manufacturing step are carried out alternately.

12. The method according to any one of the preceding claims,

characterized in that the speed of the material order in the additive manufacturing step geometry is determined accordingly.

13. The method according to any one of the preceding claims,

characterized in that at least two machining programs (41, 42) are provided in a memory area of a machine control (28) of a machine tool (20), each machining program (41, 42) each having a different component part to be produced from the same base part (14) riante is assigned.

14. Device for carrying out the method according to one of the preceding claims, with a machining machine (20), the at least two axes (23, 24) pivotally mounted workpiece holder (22), at least one work spindle (26) with a tool holder (27) and with at least one tool magazine (32) which is equipped with at least one tool (33) and at least one welding head (34) or can be fitted.

15. Device according to claim 14, characterized in that the work spindle (26) has a vertical axis or can be moved into a position with a vertical axis and / or that the welding head has a shaft which can be positioned in the tool holder (27) and forms a wire feed direction, the wire feed direction being transverse to that Shaft is oriented.