DE102012008371A1 - Method for producing an overhanging component by layered construction - Google Patents

Abstract

A method of manufacturing an overhanging component (2e) comprises performing layer-by-layer processing steps of the component multiple times, applying a layer portion having predetermined dimensions of a particulate material in a predetermined area on a base layer and heating the layer portion by means of a heat source such that the particles of the material combine with each other within predetermined dimensions. A local build-up angle of an overhang which occurs between two successive layer sections (16) does not exceed a predetermined maximum build-up angle (α) with respect to a vertical of the base layer. Thus, hydraulic cross-sections can be produced generatively without the aid of support structures whose circular replacement diameter exceeds a value of 10 mm.

Description

TECHNICAL AREA

The invention relates to a method for producing a fluid-carrying component by layered structure.

BACKGROUND OF THE INVENTION

One attempt in the manufacture of components for vehicles is in particular the weight reduction to improve the dynamic characteristics of the vehicle. In particular, in commercial aircraft, considerable efforts are being made to reduce the weight of components to allow more economical operation by saving fuel. This is not limited to main components, but also applies to all installations and systems.

A method for producing a control block in lightweight metal construction is out DE 10 2006 062 373 A1 known, in which a system of circuit elements is designed with load-friendly walls that are connected directly or with other elements to a coherent structure and all produced by a generative manufacturing process.

Cavities or closed walls with an opening perpendicular to the mounting direction, which are arranged in the construction direction of a generative layer construction method and are successively closed by the layer construction process, require from a certain spatial extent support structures. Thus, for example, in the case of circular tube cross-sections with a diameter of more than 10 mm, it can be observed that in the structure of the tapering, occluding section of the tube cross-section, the melted material of an overhang always sinks into the underlying powder bed.

The manufacturing fluid-carrying components in a layered structure with a closed cross section and an opening perpendicular to the mounting direction may require significant additional effort by the necessary support structures. Thus, both the overall manufacturing time and the costs are increased by relatively intensive reworking to remove the support structures, so that the economy of the manufactured component is reduced overall.

An object of the invention is therefore to propose a method for producing a component having an overhang, which allows both a reduction of the manufacturing time, the costs incurred and the necessary reworking in relation to the removal of necessary support structures, while still the manufactured component as possible should have the same mechanical and physical properties, as that of a manufactured in other ways component.

SUMMARY OF THE INVENTION

The object is achieved by a method having the features of independent claim 1. Advantageous embodiments and developments can be found in the dependent claims.

A method for producing an overhanging component comprises performing one or more processing steps for the layered construction of the component, with at least the application of a layer portion having predetermined dimensions of a particulate material in a predetermined area on a base layer and the heating of the layer portion means a heat source in such a way that the particles of the material combine with one another within predetermined dimensions, wherein a local superstructure angle of an overhang that occurs between two successive layer sections does not fall below a predetermined minimum installation angle to a base layer.

The base layer is to be understood as a layer which is already present before each application of another layer. For example, at the beginning of the process, the base layer is a support structure made of multiple layers of fusible material. All other material layers applied thereon form the base layer for the respective subsequent layer.

An overhang is furthermore to be understood as such a part of a layer section below which the underlying layer section has a recess. A first layer section may have approximately a recess over which a second layer section extends with a recess. If the recess of the second layer section is tapered with respect to the recess of the first layer section, edges of the superposed recesses form the mounting angle, which must not exceed a certain value.

This additive manufacturing process may preferably be applied in the form of an additive layer manufacturing (ALM) process in the design of hydraulic systems, manifolds, and other particularly light weight hydraulic equipment, particularly for use in commercial aircraft. This creates a spatial component in layers relatively arbitrarily complex shape. The material properties are equal or superior to a casting. Lasers are particularly suitable as the heat source, so that a special form of an ALM method is an SLM ("Selective Laser Melting") method. It is advantageous to use powdered steel, stainless steel, aluminum alloys, titanium alloys or other fusible materials in the process according to the invention. For certain applications, cobalt and nickel alloys are known. For use in vehicles and in particular commercial aircraft is particularly powdery AlSi10Mg and TiAl6V4.

The achievable layer thicknesses are dependent on several factors, such as the performance of the heat source used, the required accuracy, the material properties and the reworkability. The smallest possible base area of a layer section is dependent on the geometric extent of the heat source. With particularly fine heat sources, such as a laser beam, therefore, a particularly fine structure can be produced. The process is repeated by adjusting the respective melted contour until the component is completed.

The shape of a pipe cross-section is also dependent on the supporting effect of the solidified material surrounding the molding. Advantageously, a completely covering layer can be generated for uniting successive overhangs if the so-called overhang radius or end radius of an opening to be closed does not exceed a certain value. Thus, overhang radii of up to 4 mm with sufficient dimensional accuracy and surface quality can be manufactured generatively without support structure. As the radius increases, the specified quality parameters gradually decrease until finally no successful production is possible without the aid of support structures. Thus, the support-free producible molding cross-section is limited and represents for technical applications in about hydraulic or pneumatic systems, a significant limitation of the system properties. To solve the problem, a teardrop-shaped cross section is proposed, the base radius of any size and its overhang radius assume a derived from the quality parameters size can. The combination of the radii can take place via planar as well as single or multiple curved geometric structures, wherein the choice of the local mounting angles material and process parameter specific critical angles is subject. For light metal alloys such as A1Si10Mg or TiAl6V4, these are approximately 45 °. The consistent avoidance of too small installation angles means that the molten material does not or only slightly sinks into the powder bed and thus the quality parameters mentioned are positively influenced.

Although the design of the tube cross-section deviates from a desired, circular shape, but can be reduced by the significantly simplified manufacturing time and costs through the eliminated post-processing. Depending on the geometric design parameters, the strength to be achieved of such a fluid-conducting element can only mean a slight increase in weight in comparison to conventional tube cross-sections. As the outer boundary of such a fluid-carrying element designed in turn a circular cross-section is advantageous, this form can significantly increase the hydraulic loads to be sustained.

In an advantageous embodiment, an overhang radius of 4 mm is not exceeded. An overhang radius is a part of one or more layer sections which terminate an overhang, for example in the production of a pipe cross-section. The overhang, after the open cross-section is covered layer by layer with the mounting angle, finally closed, wherein the radius formed to the overhang does not exceed a value of 4 mm, so that there is also a sinking of molten material is not expected.

In an advantageous embodiment of the invention, the particulate material is a metallic material. This makes it possible to produce components with a high strength and in particular pressure resistance, for example for use in hydraulic systems. To achieve a particularly low weight, light alloys such as AlSi10Mg or TiAl6V4 are suitable here. Subsequent heat treatment to homogenize the metal structure significantly improves the material properties.

In an equally advantageous embodiment of the invention, the particulate material is a ceramic material, for example zirconium oxide (ZrO ₂ ) or aluminum oxide (Al ₂ O ₃ ). The compressive strength is within the scope of those made of metallic particles components, the merits of the ceramic material are particularly in the significantly reduced weight.

In an advantageous embodiment, after completion of the layered construction, the manufactured component is heat-treated in a heat treatment device. Thus, the structure of the manufactured component can be influenced such that it evenly over the entire spatial Extension of the component is such that during the manufacture of the component resulting stresses are eliminated. This may include, for example, heating to a target temperature, maintaining a target temperature, and selectively lowering the temperature.

In an advantageous embodiment, the produced body is post-machined. The base element can serve as a reference or reference. Thus, the dimensional accuracy of the entire component can be secured. For example, post-processing may include grinding, drilling, polishing, or other types of common machining methods.

In an advantageous embodiment, the produced body is aftertreated by introducing a pickling solution into cavities of the body and exciting an ultrasonic vibration in the pickling solution. Due to the layered structure, the body has a staircase-like contour at edges which form an angle other than 0 ° to the direction of construction, the shape of the steps being dependent on the layer thicknesses. By means of the surface treatment according to the invention with the aid of the pickling solution, this contour can be smoothed. A pickling solution in the context of this invention is an acid or a mixture of acids, preferably mineral acids, with or without the addition of hydrofluoric acid. Mineral acids are acids which contain no carbon and generally comprise hydrochloric acid, sulfuric acid and nitric acid and possibly phosphoric acid. Particularly suitable is a mixture of nitric acid and hydrofluoric acid. The excitation of an ultrasonic vibration can be achieved by introducing at least one sonotrode in the pickling solution, which is coupled to one or more ultrasonic transmitters. Ultrasonic waves with a frequency of, for example, 20 kHz to 40 kHz can cause strong cavitation in the pickling solution, the effect of which leads to a high fluid exchange. This realizes a particularly homogeneous material removal on the component to be treated.

In an advantageous embodiment, the introduction of the pickling solution can be carried out by immersing the component in a container containing the pickling solution. This ensures that the pickling solution penetrates into all cavities. In addition to the treatment of the surfaces of the cavities while a treatment of external surfaces is achieved.

In a further advantageous embodiment, the ultrasonic oscillation is generated in the at least one cavity of the component, so that the material removal concentrates on the technically essential surfaces.

In addition, by using the produced body as the anode by applying a positive voltage and the sonotrode as a cathode by applying a negative voltage by immersion in an electrolytic solution, e.g. As an aqueous solution of NaClNaNO ₃ , an electrochemical removal of metal ions are carried out on the body, wherein the electrolyte is cleaved. The dissolved metal ions enter into reactions with parts of the split electrolyte at the anode, so that a metal hydroxide is obtained, which settles in a dip tank and is removed.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, advantages and applications of the present invention will become apparent from the following description of the embodiments and the figures. All described and / or illustrated features alone and in any combination form the subject matter of the invention, regardless of their composition in the individual claims or their back references. In the figures, the same reference numerals for identical or similar objects.

1 shows in successive representations the structure of a pipe section.

2a and 2 B show a sectional view of a pipe cross-section with different gradients of an inner contour.

3 shows in sequential schematic representations a variant of a post-treatment process.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

1 shows the progress in the production of a pipe section 2e with a cross-section normal to a construction direction A. The manufacturing process is generative, thus starting from a substrate surface 4 Layer by layer using a heat source of a powdery material along a predetermined contour generates a fine segment of the pipe section, which connects to an underlying segment. There are various stages of a pipe section with 2a . 2 B . 2c . 2d and 2e denotes, wherein pipe section 2a an initial stage concerns and 2e a final stage.

In the exemplary illustration receives a pipe section 2a initially a circular cross-section 6 who is in a pipe section 2 B along the construction direction A extends until it kinks 8th reached. An open cross section of a pipe section 2c transversely to the construction direction A is successively enlarged to a lower part of the transverse to the construction direction A pipe section 2e to generate. Once the point of maximum width has been reached, the pipe cross-section running transversely to the direction of construction A must be closed, which is achieved by successive narrowing.

The layer-by-layer reduction of the distance from flanks 10 and 12 of the pipe cross-section is limited by an assembly angle α, which is exemplary of a drop-shaped end cross-section 14 can lead if the lowest possible angle is always maintained. In 2a and 2 B the construction angle are shown using two exemplary sectional views.

The approach of the flanks 10 and 12 to form a closed area can be performed by gradually reducing the respective recesses in the layer portions of the generative manufacturing process. The reduction must be limited so that the resulting angle of the flanks 10 and 12 is limited to the mounting direction A to an angle of ≥ 45 °. Layer sections shown in detail 15 Accordingly, they are adapted such that, depending on the respective thicknesses, a desired build-up angle α results therefrom. The resulting shape of the pipe cross section 14 transverse to the construction direction A is at constant minimum angle as in 2 B represented accordingly drop-shaped, since a semicircular cross-sectional part is covered with a triangular cross-sectional part.

Locally, the mounting angle can exceed the minimum value, so that other contours can be produced, which deviate from a pure drop shape. 2a shows about a changed pipe cross-section 14 ' by a variably chosen in the upper part of the mounting angle α.

The completion of the pipe cross-section 14 can then through a layer section 15 be completely closed, if an overhang or end radius r, which dimensions the opening to be closed, does not exceed a value of 4 mm. Thus, the sinking of liquid material can be prevented in a powder bed. This procedure is made by means of a section of the tip of the pipe cross-section 14 shown for clarity as a section CC in a plan view.

The pipe cross-section 14 can be dimensioned such that the substantially same fluidic properties are achieved, as with a circular cross-section.

3 shows a generatively produced, fluid-carrying component 16 made of a metallic material with system components 18 and 20 , each one a cavity 22 and 24 have, wherein the system component 18 is shown in a sectional view. The system component 18 is an example of a mounting direction A inclined by an angle β, so that the cavity 22 has a stair-step-like surface. It is important to smooth these by removing material.

The component 16 can in a container 26 be immersed, with a pickling solution 28 is filled. This may comprise a mineral acid with or without an addition of hydrofluoric acid, wherein the pickling solution must be adapted to the material of the component 16 ablate. By the duration of the dive material removal can be controlled.

To improve the material removal is an excitation of ultrasonic waves within the cavities 22 and 24 provided, for example, by introducing sonotrodes into the cavities 22 and 24 can be done. Closely adjacent and communicating cavities 22 and 24 can through a common sonotrode 30 are applied with ultrasonic waves, while non-communicating cavities may require the use of multiple sonotrodes. By excitation of ultrasonic waves, for example in a range of 20 kHz to 40 kHz, a cavitation effect can be produced, which achieves a high fluid exchange, resulting in a very homogeneous removal of material on the inner surfaces of the cavities 22 and 24 leads. This will be the surfaces of the cavities 22 and 24 smoothed and the frictional resistance of a through this component 16 reduced to leading fluids.

The effect can be further achieved by exciting an ultrasonic vibration when the pickling solution is an electrolyte solution and between the component 16 and the sonotrode 30 a voltage is applied.

In addition, it should be noted that "having" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. It should also be appreciated that features described with reference to any of the above embodiments may also be used in combination with other features of other embodiments described above. Reference signs in the claims are not to be considered as limiting.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102006062373 A1 [0003]

Claims (15)

Method for producing an overhanging component ( 2e ), comprising the multiple execution of processing steps for the layered structure of the component ( 2e . 16 ), comprising at least: - depositing a layer section having predetermined dimensions of a particulate material in a predetermined area on a base layer and - heating the layer section by means of a heat source such that the particles of the material interconnect within predetermined dimensions, one between two consecutive ones Layer sections ( 16 ) setting of the local superstructure angle (α) of an overhang does not fall below a predetermined minimum superstructure angle to the base layer. A method according to claim 1, wherein a closed top surface having a radius (r) is used for combining successive overhangs of a layer section in a subsequent layer section, wherein the radius (r) does not exceed an extension of 4 mm. Method according to one of the preceding claims, wherein the particulate material is a metallic material. Method according to one of the preceding claims, wherein the particulate material is a ceramic material. Method according to one of the preceding claims, wherein after completion of the layered structure, the manufactured component ( 2e ) is heat treated in a heat treatment apparatus. Method according to one of the preceding claims, wherein the assembled component ( 2e . 16 ) is machined. Method according to one of the preceding claims, wherein the assembled component ( 2e . 16 ) is treated on the surface, comprising the steps of: - introducing a pickling solution ( 28 ) in cavities ( 22 . 24 ) of the component ( 2e . 16 ) and - excitation of an ultrasonic vibration in the pickling solution ( 28 ). Process according to claim 7, wherein the pickling solution ( 28 ) is an acid or a mixture of acids. A method according to claim 8, wherein a in the pickling solution ( 28 ) acid is a mineral acid. A method according to claim 8 or 9, wherein the pickling solution contains hydrofluoric acid. Method according to one of claims 7 to 10, wherein the excitation of an ultrasonic vibration by introducing at least one sonotrode ( 30 ) into the pickling solution ( 28 ) is achieved. The method of claim 11, wherein the at least one sonotrode ( 30 ) in at least one cavity ( 22 . 24 ) of the component ( 2e . 16 ) is introduced. Method according to one of claims 7 to 12, wherein the introduction of the pickling solution ( 28 ) by immersing the component in a container ( 26 ), the pickling solution ( 28 ). Method according to claim 7 and 11 or 12, applying a positive voltage to the produced body ( 28 ) and a negative voltage at the sonotrode ( 30 ), wherein the pickling solution is an electrolyte solution. Pipe section ( 2e ) produced by a generative manufacturing method having the features of claims 1 to 14, comprising a cross-section ( 14 ) perpendicular to a mounting direction (A).

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