EP3782739A1

EP3782739A1 - A component for use as rotary body

Info

Publication number: EP3782739A1
Application number: EP19193106.2A
Authority: EP
Inventors: Niklas Bisch; Aggeliki QUELL; Florian Wassermann
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2019-08-22
Filing date: 2019-08-22
Publication date: 2021-02-24

Abstract

The invention relates to a component having a base body (1) of a first material comprising a tubular inner shell (2) and a tubular outer shell (3) coaxially collocated around a common longitudinal axis (4) and forming an annular space (5) between the outer wall of the inner shell (2) and the inner wall of the outer shell (3), the annular space (5) having lattice structures (6) in it connecting the inner shell (2) and the outer shell (3) in radial direction, one end face (7) of the annular space being closed and the opposite end face (8) of the annular space being open, characterized in that the annular space (5) is filled with a second material which encloses the lattice structures (6). The invention further relates to a method for the manufacture of a component according to the invention by an additive manufacturing process.

Description

The invention relates to a component having a base body comprising a tubular inner shell and a tubular outer shell coaxially collocated around a common longitudinal axis. The component may comprise a further segment that is formed onto the base body.
Such components are used in process technology as rotating bodies, for example as classifier wheels for separating or classifying solid particles.
Document DE 198 40 344 A1 discloses a classifier wheel for a centrifugal wind sifter with blades through which the air flows from the outside to the inside in the opposite direction to the direction of centrifugal flow, which are arranged between a circular disc carrying the classifier wheel hub and an annular cover disc. The flow channels formed by the surfaces of the blades contain internals which specifically influence the flow path.
In the document DE 10 2004 053 530 A1 , a classifying wheel for a device for separating powdery, fibrous or granular materials is proposed, which consists of a monolithically formed cylindrical body having a concentric core for receiving a drive shaft. A plurality of flow apertures is distributed over the cylinder circumference and is formed as slots extending in the longitudinal direction of the cylinder or as radially oriented bores.
The inner wall of the tubular inner shell facing the coaxial longitudinal axis forms a sleeve in the base body of the component, which is usually used to receive a drive device, such as a drive shaft of a motor, through which the component can be set in rotation.
Such components are exposed to high stresses and loads during operation, both due to centrifugal forces at high rotational speeds and external forces such as the impact of particles on the component surface in the case of classifier wheels or aerodynamical forces, for example. Conventionally, such components are therefore usually made of a robust material such as steel or other metals, whereby the base body of the component is designed as a solid body. The advantage of the robustness compared to impacting forces is bought by a high dead weight of the component, whereby the roller bearings mounted on the driving shaft required for rotation are highly strained and, thus, wear quickly.
It was an object of the invention to provide a component for use as a rotating body, which has comparable rotational properties and stability to known components but has a lower dead weight than known components.
This task is solved according to the invention by a component according to claim 1. Furthermore, the task is solved by a process for manufacturing a component according to claims 9 and 15. Advantageous variants of the component and the process are presented in claims 2 to 8 and 10 to 14.
A first subject of the invention is a component having a base body of a first material comprising a tubular inner shell and a tubular outer shell coaxially collocated around a common longitudinal axis and forming an annular space between the outer wall of the inner shell and the inner wall of the outer shell. The annular space comprises lattice structures which connect the inner shell and the outer shell in radial direction. The terms "inner wall" and "outer wall" refer to the radial direction perpendicular to the longitudinal axis of the component. One end face of the annular space is closed, and the opposite end face of the annular space is open. The annular space is filled with a second material which encloses the lattice structures.
In contrast to components with a base body made of a solid material according to the prior art, the component according to the invention has a significantly lower dead weight due to the annular space of the base body. However, due to the lattice structures that connect the inner shell and the outer shell in radial direction, rigidity and structural stability are at least comparable to prior art components. Radial, axial or azimuthal forces acting on either of the shells are received and transferred to the opposite shell by means of the lattice structures. The filling of the annular space with a second material seals the base body of the component and prevents imbalances of the rotating component due to ingression of particles into the base body. In addition, the filling protects the lattice structures against detrimental effects like abrasion, erosion or corrosion.
In a preferred embodiment of the component according to the invention the outer wall of the outer shell is rotationally symmetrical with respect to the longitudinal axis. In another preferred embodiment the inner wall of the inner shell is rotationally symmetrical with respect to the longitudinal axis. In a further preferred embodiment of the component according to the invention the outer wall of the outer shell and the inner wall of the inner shell are rotationally symmetrical with respect to the longitudinal axis. Rotational symmetry of the inner and/or outer surfaces prevents an imbalance when the component is rotated. This is of increasing importance with increasing rotational speeds at which the components are rotated.
Rotational symmetry as used herein with respect to the shell walls means the relationship of the inner and/or outer surface of the component or its parts to the free environment. If, for example, the inner wall of the inner shell forms a recess in the base body of the component for receiving a drive device such as a drive shaft of a motor, the symmetry of this inner wall is of no importance in view of any imbalances. However, the outer wall of the outer shell in this example is of importance if the component is to be designed in view of the reduction or prevention of imbalances.
According to the invention, the annular space comprises lattice structures that connect the inner shell and the outer shell in radial direction. The lattice structures may be of any form as long as the function of connectivity between the shells in radial direction is given. Preferably, the lattice structures comprise 3-dimensional X-lattices, softbox lattices, honeycomb structures, organic lattice structures and/or simulation-based lattices. The lattice structure may be simulated and optimized with respect to its topology by means of mathematical models. In a preferred embodiment the lattice structure is elongated in the direction of the longitudinal axis, in particular if the lattice structure is produced via additive manufacturing methods.
Preferably, the lattice is an open-cell structure. More preferably, the cross-sectional gap width of the lattice is homogeneous in the sense that single gap widths do not differ from each other by more than 50%, more preferably not more than 25%, most preferably not more than 10%. The term "cross-sectional" refers to a plane that is perpendicular to the longitudinal axis of the base body. A homogenous distribution of gap widths enhances the process of filling the cavities in the annular space with the second material.
In a further preferred embodiment the lattice structure provides open channels extending from the open end face of the base body towards the opposite closed end face of the base body. This geometric feature further enhances the process of filling the cavities in the annular space with the second material.
The ratio of the total volume of the lattice structure to the volume of the empty annular space without lattice structure is preferably in the range from 10% to 70%, more preferably in the range from 20% to 50%, most preferably in the range from 30% to 40%. Depending on the requirements on stability and weight of the component, the lattice structure may be designed with a higher or lower percentage of volume in the annular space.
In a preferred embodiment the lattice structures have an n-fold rotational symmetry where n is a natural number greater than 2. From a practical point of view in terms of producibility of the lattice structures the number n should be smaller than 50, preferably smaller than 20. However, lattice structures with a higher n-fold rotational symmetry are also encompassed by the invention. According to the invention "rotational symmetry" is to be understood as a symmetry with respect to functional features of the lattice structure. A symmetry in a strictly mathematical or geometric sense is not a prerequisite.
The first material that constitutes the base body may be any material that is suited to withstand the stresses and forces the component is exposed in operation. In a preferred embodiment the first material is selected from the group of metallic materials, ceramic materials or combined metal-ceramic materials. More preferably, the metallic materials, ceramic materials or combined metal-ceramic materials are suited to be processed in an additive manufacturing process.
In a preferred embodiment of the invention the first material is a metallic material selected from the group of aluminum alloys, magnesium alloys, nickel-base alloys, steel, stainless steel or tool steel. If a light weight construction is a requirement aluminum alloys or magnesium alloys are preferred. If mechanical strength and stability are requirements tool steel is preferred. If chemical resistance of the first material is of importance stainless steel or nickel-base alloys are preferred.
The second material that fills the annular space of the base body may be any material that can be filled into the cavities of the lattice structure in the annular space of the base body.
It is preferred that the density of the second material is lower than the density of the first material. Preferably, the density of the second material is in the range of from 0.01 to 5 g/cm³, more preferably in the range of from 0.5 to 1.5 g/cm³.
It is further preferred that the second material is pourable or capable of flowing into the cavities in the annular space.
It is further preferred that the second material shows a good adhesion to the surface of the first material, e.g. to the inner walls of the inner and outer shell of the base body.
It is further preferred that the second material is selected from chemically resistant substances.
It is further preferred that the coefficients of thermal expansion of the first material and of the second material are similar in the sense that the ratio of the coefficient of the second material to the coefficient of the first material is less than 7, more preferably less than 3.
In a preferred embodiment the second material is a polymer, in particular selected from the group of thermosets or thermoplastics. In an even more preferred embodiment the second material is based on an epoxy resin.
In one preferred variant the second material is selected from the group of thermosets and is provided for filling as a reactive mixture with an initial viscosity below 800 mPas.
In another preferred variant the second material is selected from the group of thermoplastics and is provided for filling as a hot-melt with an initial viscosity below 800 mPas.
It is further preferred that the second material has a glass transition temperature of at least 140°C. A high glass transition temperature is particularly advantageous for components that heat up while in operation, e.g. due to external forces. A high glass transition temperature of the second material ensures that the annular space conserves its rigidity and does not start to flow or creep unpredictably.
In a further preferred embodiment the second material is essentially free of gas bubbles. This can be achieved by a pre-treatment of the second material to remove any gas bubbles before the second material is introduced into the annular space. Thereby, a more uniform second material is achieved and the risk of cavity formation in the second material that could lead to imbalances of the rotating component is reduced.
In a further preferred embodiment the first material is treated mechanically, thermally or chemically before the second material is introduced.
It is further preferred that the structural part of the base body is self-supporting in the sense that the structure of the base body which is formed by the first material is able to withstand external loads and forces when in operation. Advantageously, the minimal wall thickness of the respective elements of the base body as well as the minimal diameter of the elements of the lattice structure are 1 mm. The second material may contribute to the structural properties to a minor degree. The main tasks of the second material are to seal the base body against ingression of external particles and the protection of the lattice structures against detrimental effects like abrasion, erosion or corrosion.
The component according to the invention may be used in a variety of different applications in the process industry. Depending on the intended application, the component may comprise further elements or constituents in addition to the base body.
In a preferred embodiment of the component according to the invention a further component segment is integrally formed onto the closed end face of the base body in the direction of the longitudinal axis directed away from the base body. The further component segment may comprise any technically useful element like blades, edges, lamellas, stirrers, or mixing elements.
In a particularly preferred embodiment the component is a classifier wheel, an impeller wheel, e.g. a pump wheel, or a machining tool, e.g. a cutting tool.
It is further preferred that the inner and/or outer surfaces of the further components are rotationally symmetrical with respect to the longitudinal axis.
A second subject of the invention is a method for the manufacture of a component having a base body of a first material comprising a tubular inner shell and a tubular outer shell coaxially collocated around a common longitudinal axis and forming an annular space between the outer wall of the inner shell and the inner wall of the outer shell, the annular space having lattice structures in it connecting the inner shell and the outer shell in radial direction, one end face of the annular space being closed and the opposite end face of the annular space being open. According to this second subject of the invention the base body of the component is formed by an additive manufacturing process in a first step, and the annular space in the base body is filled with a second material which encloses the lattice structures in a second step.
Additive manufacturing processes, also referred to as generative manufacturing processes or 3D printing, are known from the prior art. In an additive manufacturing process, the material is added layer by layer to produce a component. In the case of metal powder or ceramic powder as a material, for example, metal powder particles or ceramic powder particles are applied iteratively and melted by energy input, so that the component is built up layer by layer. Common processes include selective laser melting (SLM), selective laser sintering (SLS), binder jetting, direct energy deposition processes such as laser metal deposition (LMD) and electron beam melting (EBM).
The component can be manufactured in different ways. In a first preferred variant, the component is completely manufactured in an additive manufacturing process. In this variant, the component is preferably manufactured coaxially to the longitudinal axis. The layered construction thus begins with the open end face of the base body with the inner and outer shell and the respective first elements of the lattice structure to which the remainder of the component is fused layer by layer. Depending on the layout of the component it may be appropriate from a practical point of view to begin the layer-wise construction at the opposite end of the component. In this case, the component is built up layer by layer up to the open end face as the last piece to be fused.
In a second preferred variant, the component comprises a base body and a further component segment integrally formed onto the closed end face of the base body.
The further component segment or parts thereof are prefabricated, e.g. by conventional fabrication methods or by additive manufacturing methods. The base body is integrally formed onto the further component segment by additive manufacturing methods. The layered construction thus begins with the closed end face of the base body with the inner and outer shell and the respective first elements of the lattice structure to which the remainder of the component is fused layer by layer up to the open end face as the last piece to be fused. The closed end face may be a part of the further component segment or may be fused onto the further component segment by an additive manufacturing method. In this variant, too, the component is preferably manufactured coaxially to the longitudinal axis.
In a third preferred variant, parts of the component are prefabricated whereas the base body and further parts of the component are manufactured in an additive manufacturing process. The prefabricated parts and the additively manufactured parts are assembled after their respective fabrication.
In the case of variants with prefabricated components, the respective component can be manufactured using known manufacturing processes, for example by conventional methods like casting or cutting, or by additive manufacturing.
In a preferred embodiment of the method for the manufacture of a component according to the invention particles of the first material which are not firmly bonded to the base body are removed from the annular space after completion of the base body and before filling in the second material. This reduces the probability of imbalances of the rotating component due to particle agglomerations inside the annular space that might distort the rotational symmetry.
In a further preferred embodiment of the method for manufacture the first material is treated mechanically, thermally or chemically before the second material is introduced. Mechanical treatment may include roughening of surfaces inside the annular space to improve the adhesion of the second material to the first material. Mechanical treatment may further include grinding or polishing of surfaces inside the annular space to improve the flux of the second material into the lattice structure. Mechanical treatment may also combine different methods. As an example, the walls of the shells inside the annular space may be designed with a pre-defined roughness that is higher than the roughness of the lattice structures. After the production of the component and before the filling of the annular space of the base body with the second material the annular space can be subjected to a grinding or polishing process. As a result, the flux of the second material through the lattice structure is enhanced while the adhesion of the second material to the walls of the shells is improved as well.
Thermal treatment may include homogenization or stress relief annealing. Stress relief annealing relieves residual stresses in the finished component and minimizes subsequent distortion of the component during operation. Chemical treatment may include nitriding to increase the hardness of the component.
In a second step of the method for the manufacture of a component according to the invention the annular space in the base body is filled with a second material which encloses the lattice structures. The process of filling the annular space is suitably selected depending on the properties of the second material. Examples are pouring-in or pressing-in the second material into the open end face or introducing a reactive mixture as the second material into the annular space that cures or develops a foam over time.
In a preferred embodiment the annular space in the base body is filled with the second material starting from the closed end face of the base body. This reduces the risk of cavity formation in the second material that could lead to imbalances of the rotating component. Preferably, a small tube, e.g. a cannula or a pipette, is introduced into the lattice structure down to the closed end face of the base body, filling of the second material through the tube is started, and the tube is withdrawn from the annular space in the course of filling the annular space with the second material.
In one preferred variant the second material is selected from the group of thermosets, the second material is filled into the annular space as a reactive mixture, and the initial viscosity of the reactive mixture is below 800 mPas.
In another preferred variant the second material is selected from the group of thermoplastics, the second material is filled into the annular space as a hot-melt, and the initial viscosity of the hot-melt is below 800 mPas.
In a further preferred embodiment of the method for manufacture the second material is pre-treated to remove any gas bubbles before the second material is introduced into the annular space. Thereby, a more uniform second material is achieved and the risk of cavity formation in the second material that could lead to imbalances of the rotating component is reduced.
A third subject of the invention is a method for the manufacture of a component having a base body of a first material comprising a tubular inner shell and a tubular outer shell coaxially collocated around a common longitudinal axis and forming an annular space between the outer wall of the inner shell and the inner wall of the outer shell, the annular space having lattice structures in it connecting the inner shell and the outer shell in radial direction, one end face of the annular space being closed and the opposite end face of the annular space being open. According to this third subject of the invention the base body of the component is formed by an additive manufacturing process, and the annular space in the base body is filled with a second material which encloses the lattice structures during the formation process of the base body.
In a preferred embodiment of this third subject of the invention, the formation of the base body by the first material and the filling of the annular space with the second material is an iterative process. In a first step, a first part of the base body can be formed by an additive manufacturing process. In a second step, the annular space in the base body formed in the first step can be filled with the second material. In a third step, a second part of the base body can be formed onto the first part of the base body by an additive manufacturing process. In a fourth step, the annular space in the base body formed in the third step can be filled with the second material. Subsequently, the third and fourth step can be repeated until the base body and/or the component are formed in their entirety.
In an alternative preferred embodiment of this third subject of the invention, the formation of the base body by the first material and the filling of the annular space with the second material are performed simultaneously, for example by a multi-material additive manufacturing process wherein the first material forms the structural part of the base body and the second material forms the filling of the annular space of the base body created by the first material. First material and second material may be applied layer by layer to form the base body and/or the component in their entirety.
The invention is explained in more detail below with reference to the drawings. The drawings are to be interpreted as in-principle presentation. They do not constitute any restriction of the invention, for example with regards to specific dimensions or design variants. In the figures:

Fig. 1: shows a perspective view of a classifier wheel as a first embodiment of a component according to the invention.
Fig. 2: shows a detailed cutout of the perspective view of Fig. 1.
Fig. 3: shows a longitudinal cut of the classifier wheel according to Fig. 1.
Fig. 4: shows a detailed cutout of the longitudinal cut of Fig. 3.
Fig. 5: shows a bottom view of the classifier wheel according to Fig. 1.
Fig. 6: shows a perspective view of a further classifier wheel as a second embodiment of a component according to the invention.
Fig. 7: shows a longitudinal cut of the classifier wheel according to Fig. 6.
Fig. 8: shows a detailed cutout of the longitudinal cut of Fig. 7.
Fig. 9: shows a bottom view of the classifier wheel according to Fig. 6.

List of reference numerals used:

1: base body
2: inner shell
3: outer shell
4: longitudinal axis
5: annular space
6: lattice structures
7: closed end face
8: open end face
9: recess
10: cover plate

Example 1 (first embodiment)

Fig. 1 shows a perspective view of a classifier wheel as a first embodiment of a component according to the invention. The classifier wheel has a base body 1 of a first material comprising a tubular inner shell 2 and a tubular outer shell 3 coaxially collocated around a common longitudinal axis 4. The outer wall of the inner shell 2 and the inner wall of the outer shell 3 form an annular space 5 between them, wherein the terms "inner wall" and "outer wall" refer to the radial direction perpendicular to the longitudinal axis 4. In the axial direction the annular space 5 has two opposite end faces. One end face 8 is open and forms the lower end of the classifier wheel. The opposite end face 7 (not visible in Fig. 1) is closed. A further component segment is integrally formed onto the closed end face in the direction of the longitudinal axis 4 directed away from the base body 1. This further component segment is a hollow cylinder with slots in the cylinder wall in longitudinal direction and constitutes the functional part of the classifier wheel.
The outer wall of the outer shell 3 as well as the outer wall of the cylinder of the further component segment are rotationally symmetrical with respect to the longitudinal axis 4.
The inner shell 2 and the outer shell 3 are connected in the radial direction by lattice structures 6 in the annular space 5. The layout of the lattice structures 6 is explained in more detail with reference to Figs. 2 to 5:
The lattice structures 6 are formed by a multitude of nodal points connected with each other by straight webs. The nodal points are aligned in horizontal and longitudinal planes, wherein the term "horizontal" refers to a plane that is perpendicular to the longitudinal axis 4. In each horizontal plane the nodes are arranged in an orthogonal manner forming a chessboard-like grid of nodes. Fig. 5 is a bottom view of the classifier wheel and shows the orthogonal arrangement of the grid of nodes in the first horizontal plane (counting from the bottom of the base body towards its upper end).
Each of the nodes in a horizontal plane is connected by webs to four other nodes in the horizontal plane below the actual plane and to four other nodes in the horizontal plane above the actual plane. In the longitudinal direction, the nodes are offset in a way that the node of the actual horizontal plane is placed in the intersection point of the four nodes of the horizontal plane that this node is connected to. This connecting layout is shown in longitudinal cut of the classifier wheel in Fig. 3 and 4 and in the detailed cutout of the perspective view in Fig. 2.
In the exemplary classifier wheel shown in Figs. 1 to 5, the rotational symmetry of the lattice structure is 4-fold. Turning the wheel around its longitudinal axis 4 by 90°, 180° and 270° leads to identical layouts in view of their structural properties. Structural properties are, for example, the orientation of the nodes and their connections of the grid as they determine the stability and rigidity of the lattice structure. In view of these functional features the lattice structure is 4-fold rotational symmetric, even though the structure is not exactly symmetric in a strictly mathematical or geometric sense.
The inner wall of the inner shell 2 has two longitudinal recesses 9 for receiving a drive device such as a drive shaft of a motor. The drive shaft of the motor and the inner wall of the inner shell 2 will be assembled in a form-fitted way. Thus, in operation there will be no imbalance due to the recesses 9 in the inner shell 2.
A classifier wheel according to Figs. 1 to 5 has been manufactured according to the invention. Apart from a cover plate 10 at the upper end of the classifier wheel, the whole component has been formed by an additive manufacturing process.
The classifier wheel has been manufactured on a Selective Laser Melting machine SLM 125 HL (by company SLM Solutions Group AG, Luebeck, Germany) using an infrared laser as energy source. The first material was a tool steel powder with particles in the range of from 15 to 50 micrometers and a density of 7.7 g/cm³. The thickness of each layer during the printing process was 30 micrometers.
The classifier wheel was manufactured starting from the open end face 8 of the base body 1 and was built up layer by layer up to the upper end of the classifier wheel. The length of the classifier wheel was 75 mm with a diameter of the wheel of 50 mm. The inner diameter of the inner shell 2 was 17 mm. The outer diameter of the outer shell 3 was 40 mm.
After completion of the component including the base body 1 and the further component segment particles of the first material which were not firmly bonded to the base body 1 were removed from the annular space by shaking the component and by using a suction apparatus for the remaining parts.
The cover plate 10 was manufactured in a conventional cutting process. The cover plate 10 and the additively manufactured part were assembled by shrink fitting. The assembled component was subjected to soft nitriding in order to increase the hardness of the outer surfaces of the component.

In a second step the cavities of the annular space were filled with a second material. The second material was an epoxy system (thermoset) with the following ingredients:

Ingredient	Chemical Structure	Function	Weight-%
Epilox® A19-03 (LEUNA-Harze GmbH)	Bisphenol A based epoxy resin	Resin	79.9
Epliox® P13-18 (LEUNA-Harze GmbH)	Monoglycidyl ether of C12-C14 alcohol	Reactive diluent	3.6
Baxxodur® EC 210 (BASF SE)	Methyl-diaminocyclohexane	Hardener	16.5

The three ingredients were mixed in a vacuum speed mixer until a homogeneous reactive mixture was obtained. The initial viscosity of the mixture was 782 mPas at a temperature of 23°C. The density of the mixture was 1.1 g/cm^3. The mixture was filled into a 60 ml syringe with a metal cannula with an inner diameter of 2 mm. The diameter of the cannula was small enough such that it could be introduced through the lattice structure 6 from the open end face 8 down to the inner surface of the closed end face 7. The filling of the annular space 5 was started at the closed end face 7. The cannula of the syringe was withdrawn from the annular space 5 in the course of filling the annular space 5 with the epoxy system.
The filled component was put into a chamber and was degassed by applying a vacuum suction to the chamber for one hour. Afterwards, it was placed into a drying chamber for two hours at a temperature of 120°C and for another hour at a temperature of 140°C. At the end of this procedure the epoxy system was completely cured. Its glass transition temperature was 146.9°C.
The mass of the classifier wheel according to the invention was 335 g with a contribution of 318 g by the first material and of 17 g by the second material. The ratio of the total volume of the lattice structure to the volume of the empty annular space without lattice structure was 35%. Compared to a corresponding classifier wheel made from a solid material, the mass of the classifier wheel according to the invention is reduced by 23%.
The classifier wheel has been subjected to a spinning test to determine its mechanical properties. The classifier wheel withstood 105 minutes of operation at a speed of 21,600 rpm with multiple start-ups and shut downs without any problems. No failures or damages of the lattice structure or any other load-bearing parts of the classifier wheel have been detected. A frequency analysis of the measured vibration data during the test showed a dominant amplitude for the rotation frequency. Thus, the manufacturing quality of the classifier wheel produced in the SLM process was high enough such that no balancing was necessary.

Example 2 (second embodiment)

Fig. 6 shows a perspective view of a further classifier wheel as a second embodiment of a component according to the invention. Whereas in the first embodiment the lengths (in longitudinal direction) of the base body 1 and the further component segment are similar, the length of the base body 1 in the second embodiment is much shorter than the length of the further component segment. Apart from the geometric differences, the elements of the second embodiment fulfill the same functions as the respective elements of the first embodiment.
The classifier wheel according to the second embodiment has a base body 1 of a first material comprising a tubular inner shell 2 and a tubular outer shell 3 coaxially collocated around a common longitudinal axis 4. The outer wall of the inner shell 2 and the inner wall of the outer shell 3 form an annular space 5 between them. In the axial direction the annular space 5 has two opposite end faces. One end face 8 is open and forms the lower end of the classifier wheel. The opposite end face 7 (not visible in Fig. 6) is closed. A further component segment is integrally formed onto the closed end face in the direction of the longitudinal axis 4 directed away from the base body 1. This further component segment is a hollow cylinder with slots in the cylinder wall in longitudinal direction and constitutes the functional part of the classifier wheel.
The outer wall of the outer shell 3 as well as the outer wall of the cylinder of the further component segment are rotationally symmetrical with respect to the longitudinal axis 4.
The inner shell 2 and the outer shell 3 are connected in the radial direction by lattice structures 6 in the annular space 5. The layout of the lattice structures 6 is identical to the layout according to the first embodiment and is shown in more detail in Figs. 7 to 9.
In the exemplary classifier wheel shown in Figs. 6 to 9, the rotational symmetry of the lattice structure is 4-fold. Turning the wheel around its longitudinal axis 4 by 90°, 180° and 270° leads to identical layouts in view of their structural properties.
The inner wall of the inner shell 2 has a longitudinal recess 9 for receiving a drive device such as a drive shaft of a motor. The drive shaft of the motor and the inner wall of the inner shell 2 will be assembled in a form-fitted way. Thus, in operation there will be no imbalance due to the recess 9 in the inner shell 2.

Claims

A component having a base body (1) of a first material comprising a tubular inner shell (2) and a tubular outer shell (3) coaxially collocated around a common longitudinal axis (4) and forming an annular space (5) between the outer wall of the inner shell (2) and the inner wall of the outer shell (3), the annular space (5) having lattice structures (6) in it connecting the inner shell (2) and the outer shell (3) in radial direction, one end face (7) of the annular space being closed and the opposite end face (8) of the annular space being open, characterized in that the annular space (5) is filled with a second material which encloses the lattice structures (6).
The component according to claim 1, wherein the outer wall of the outer shell (3) is rotationally symmetrical with respect to the longitudinal axis (4).
The component according to claim 1 or 2, wherein the lattice structures (6) have an n-fold rotational symmetry and n is a natural number greater than 2 and less than 50, preferably less than 20.
The component according to any of claims 1 to 3, wherein the first material is selected from the group of metallic materials, ceramic materials or combined metal-ceramic materials.
The component according to any of claims 1 to 4, wherein the second material is a polymer, in particular selected from the group of thermosets or thermoplastics.
The component according to any of claims 1 to 5, wherein the second material has a glass transition temperature of at least 140°C.
The component according to any of claims 1 to 6, wherein a further component segment is integrally formed onto the closed end face (7) in the direction of the longitudinal axis directed away from the base body (1).
The component according to claim 7, wherein the component is a classifier wheel, an impeller wheel or a machining tool.
A method for the manufacture of a component having a base body (1) of a first material comprising a tubular inner shell (2) and a tubular outer shell (3) coaxially collocated around a common longitudinal axis (4) and forming an annular space (5) between the outer wall of the inner shell (2) and the inner wall of the outer shell (3), the annular space (5) having lattice structures (6) in it connecting the inner shell (2) and the outer shell (3) in radial direction, one end face (7) of the annular space being closed and the opposite end face (8) of the annular space being open, characterized in that the base body (1) of the component is formed by an additive manufacturing process in a first step, and that the annular space (5) in the base body is filled with a second material which encloses the lattice structures (6) in a second step.
The method according to claim 9, wherein after completion of the base body (1) and before filling in the second material, particles of the first material which are not firmly bonded to the base body (1) are removed from the annular space (5).
The method according to claim 9 or 10, wherein the annular space (5) in the base body (1) is filled with the second material starting from the closed end face (7).
The method according to any of claims 9 to 11, wherein the second material is selected
(a) from the group of thermosets, the second material is filled into the annular space (5) as a reactive mixture, and the initial viscosity of the reactive mixture is below 800 mPas; or

(b) from the group of thermoplastics, the second material is filled into the annular space (5) as a hot-melt, and the initial viscosity of the hot-melt is below 800 mPas.
The method according to any of claims 9 to 12, wherein the second material is pre-treated to remove any gas bubbles before the second material is introduced into the annular space (5).
The method according to any of claims 9 to 13, wherein the first material is treated mechanically, thermally or chemically before the second material is introduced.
A method for the manufacture of a component having a base body (1) of a first material comprising a tubular inner shell (2) and a tubular outer shell (3) coaxially collocated around a common longitudinal axis (4) and forming an annular space (5) between the outer wall of the inner shell (2) and the inner wall of the outer shell (3), the annular space (5) having lattice structures (6) in it connecting the inner shell (2) and the outer shell (3) in radial direction, one end face (7) of the annular space being closed and the opposite end face (8) of the annular space being open, characterized in that the base body (1) of the component is formed by an additive manufacturing process, and that the annular space (5) in the base body is filled with a second material which encloses the lattice structures (6) during the formation process of the base body (1).