Monolithic weighing system and manufacturing method thereof
Through the combination of additive manufacturing and subtractive processing, the material selection and structural design of the single-body weighing system are optimized, the compromise problem of material selection in the prior art is solved, and efficient functional area optimization and cost are achieved reduce.
Patent Information
- Application Number
- CN202080078846.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Priority Date
- 2019-11-18
- Filing Date
- 2020-11-09
- Publication Date
- 2024-12-24
- Estimated Expiration
- 2040-11-09
AI Technical Summary
Existing monomer weighing systems have compromises between stiffness and processability in material selection, resulting in high material cost and incomplete functionality, especially in the area of the flake joints.
Administrative manufacturing method is adopted to form single piece blanks through layering and alternating application of different materials, and optimize the thin joint area in the final processing of subtractive materials, combining sandwich structure and material transition area to ensure the material of each area The best choice.
The material selection of functional area optimization is achieved, reducing material costs, improving the elasticity and tensile strength of the flake joints, while maintaining the stiffness of the lever and the machability of the overall equipment.
Smart Images
Figure CN114729833B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a monolithic weighing system comprising a plurality of levers which are connected to one another via lamellar joints, wherein the levers on the one hand and the lamellar joints on the other hand consist of different materials or material combinations, and the levers adjoining one of the lamellar joints on both sides have a first material and the lamellar joints have a second material which is different from the first material.
[0002] The present invention also relates to a method for producing a monolithic weighing system, which comprises a plurality of levers which are connected to one another by means of lamellar joints, wherein the levers on the one hand and the lamellar joints on the other hand consist of different materials or material combinations, and the levers adjacent to one of the lamellar joints on both sides have a first material and the lamellar joints have a second material different from the first material. Background Art
[0003] A generic weighing system and a method for producing the same are known from EP 3 502 633 A1 and WO 2019 / 121350 A1.
[0004] The term "weighing system" is understood here to mean a lever mechanism, which in a balance, in particular an electronic precision balance (regardless of whether it works, for example, according to the principle of electromagnetic compensation or based on strain gauges), connects the load receiving part, for example, the balance pan, on the one hand, with the actual sensor, for example, an electromagnetic active coil device, on the other hand. For this purpose, the weighing system comprises a complex assembly of levers (including steering gears) and joints connecting these levers, which are connected to each other in an integral manner (monolithic). The typical method for manufacturing such a monolithic weighing system (referred to as "monolithic") is to mill the entire system out of a metal block, for example, aluminum. This is expensive, especially in terms of the material costs associated with it. In addition, the aluminum commonly used is not the best material for all functional aspects, but it presents a good compromise in terms of the necessary functional properties of the different components of the monolithic part and its processability. In the case of choosing other materials, the compromise is usually more unfavorable. Although a monolithic weighing system made of inexpensive stainless steel is easy to process and also has the necessary rigidity in the lever area; however, joints made of stainless steel, especially thin-film joints, usually lack the necessary elasticity and tensile strength. On the contrary, choosing, for example (Inconel) is more favorable in terms of joint properties and will also give the required lever stiffness; however, brittle Inconel is difficult to process over large areas. It is therefore advantageous to provide a single piece consisting of different materials that are connected to each other uniformly in similar materials.
[0005] This approach is pursued in the aforementioned document of the same type. The document proposes that the weighing system blank be manufactured from a material optimized for the lever region and that a recess be provided in the joint region, wherein the recess is subsequently filled with the material optimized for the joint region. According to the document mentioned, the material should be joined by casting, shaping or kneading in a material-locking manner and, in particular in the case of kneading, should be joined in a substantially material-uniform manner. However, according to the inventors' experience, this method is not very practical. Summary of the invention
[0006] The object of the present invention is to provide a generic weighing system and a method for its production which provide a practical implementation of the method for functional area-optimized material selection.
[0007] This object is achieved in conjunction with the one-piece weighing system according to the invention in such a way that the one-piece component according to the invention is provided by:
[0008] - an additive manufacturing method, in which different materials, including the first and second materials mentioned, are applied in layers and connected to form a one-piece weighing system blank, wherein the weighing system blank has the desired lever area and the desired foil joint area, and
[0009] - Subsequent subtractive final machining of the weighing system blank, at least in the area of the intended lamella joints, in order to obtain the weighing system.
[0010] A corresponding manufacturing method is solved in conjunction with the method for manufacturing a monolithic weighing system according to the invention, characterized by the following steps:
[0011] - manufacturing a weighing system blank by means of an additive manufacturing method, wherein powders made of different materials, including the first and second materials mentioned, are sintered to form the weighing system blank, wherein the weighing system blank has the desired lever region and the desired lamella joint region, and
[0012] - Subsequent subtractive final machining of the weighing system blank, at least in the area of the intended lamella joints, in order to complete the weighing system.
[0013] In short, the basic idea of the solution according to the invention is to first "print" the blank of the monolithic weighing system with the help of a "3D printer". For 3D printing (a synonym for additive manufacturing methods), different methods are known to those skilled in the art, and these methods can all be used within the scope of the present invention. Here, the so-called cold spraying method, selective laser welding, cladding and powder sintering are mentioned only by way of example. Within the scope of powder sintering, powder bed laser sintering methods and powder nozzle laser sintering methods have been proven to be particularly suitable. The advantage of this additive manufacturing method is that it is only necessary to produce a defined area of the weighing system blank made of different materials by correctly and synchronously conveying different powders, especially different metal powders. Depending on the design of the transition when changing the powder, a clear material boundary or a transition area of mutual penetration can be provided here. In any case, the various functional areas of the monolithic part can be made of materials that are optimally selected for this function.
[0014] Another advantage of additive manufacturing methods is greater geometrical design freedom compared to subtractive methods. In particular, undercuts or cavities that cannot be produced using subtractive methods or can only be produced with difficulty can be formed relatively easily using additive methods.
[0015] The disadvantage of the additive manufacturing method is the spatial accuracy that is still insufficient so far compared to conventional milling. Therefore, the present invention provides that in the second method step, subtractive reprocessing, i.e., material removal, is performed. This particularly relates to the expected lamella joint area of the weighing system blank, i.e., those areas of the weighing system blank from which the lamella joint of the weighing system is transformed within the scope of the final processing. The expected lever area, i.e., those areas of the weighing system blank from which the lever of the weighing system is transformed by the final processing, is typically also subjected to subtractive reprocessing. However, subtractive reprocessing can usually be limited to deburring or polishing. In the expected lamella joint area, within the scope of the subtractive final processing, a substantial shape change is typically performed.
[0016] Thus, for example, it is possible to produce the desired lever region from stainless steel and the corresponding lever region from a corrosion-resistant nickel-based alloy (eg ) to produce the desired lamella joint area. Its disadvantages of high price and poor processability are therefore limited to a small area of the entire device and are also overcompensated by functional optimization. In contrast, the advantages of stainless steel, low price and easy reprocessability, can be used for the majority of individual parts, where its functional properties also meet the desired requirements.
[0017] Subtractive final machining can be carried out in a manner known in principle, in each case taking into account the requirements of the individual case. For example, it can be carried out mechanically, in particular by milling, by laser optical means or by electroerosion.
[0018] Some monolithic geometries have extremely fine lamellae joints. When choosing brittle materials for these areas (e.g. ), these areas are very fragile and are prone to breakage, especially in harsh manufacturing environments. Despite the subtractive final processing provided according to the invention, it is not always possible to form the expected lamella joint area so solidly that it is reliably protected from breakage during the processing steps that are still to be carried out before the subsequent final processing. Therefore, in a special embodiment of the present invention, one (preferably all) of the expected lamella joint areas and the expected lever areas adjacent to them on both sides have two outer layers of a first material and an inner layer of a second material between them, and within the scope of the final processing, the outer layer is completely removed in the expected lamella joint area while at least partially retaining the inner layer there and in the adjacent expected lever area while at least partially retaining the inner layer and the outer layer. In other words, the weighing system blank is printed (additively manufactured) in the form of a sandwich structure across regions. The second material specifically for the joint function is introduced as an inner layer here, and its two sides are flanked by two outer layers of the first material optimized for the lever function. The outer sheath stabilizes the expected lamella joint area during the entire manufacturing and handling process until the final processing process. Only within the scope of final processing, in the area of the intended foil joint, are these outer stabilizing layers removed, leaving behind the mechanically sensitive inner layers that are optimized for the joint function and then form their foil joint in the finished single component. At the same time, the foil joint reaches relatively deeply into the adjacent lever and is thus firmly anchored in the single component to the adjacent structure.
[0019] Alternatively, it can be provided that the levers adjacent to the lamella joint on both sides are mainly composed of the first material, while the lamella joint is completely composed of the second material, which gradually transitions into the first material in a transition area located within the lever. In this embodiment, the expected lamella joint area is preferably already printed only from the second material optimized for the joint function. The anchoring portion in the adjacent expected lever area is achieved by constructing a corresponding transition area, which can be achieved, for example, by superimposing a mixed delivery of two materials in an additive manufacturing process. In this embodiment, subtractive reprocessing is not too expensive. However, the expected lamella joint area is not protected at all, so this design is not suitable for all materials.
[0020] It is of course possible to shape different intended laminar joint regions of the weighing system blank in different ways, so that different laminar joint structures can be realized within the same single component.
[0021] As already explained above, different material combinations have proven to be particularly useful. It can therefore be advantageously provided that the first material and the second material are metallic materials, wherein the first material is in particular stainless steel and the second material is in particular Alternatively, the first material can be, in particular, a copper-nickel-tin alloy and the second material can be, in particular, a copper-beryllium alloy. This description of a material combination is to be understood as purely exemplary and is not to limit the invention in any way.
[0022] In another embodiment, it can therefore be provided that the first material is a ceramic, in particular zirconium oxide or aluminum oxide, and the second material is a metallic material. In particular, the above-mentioned ceramics have proven to be very suitable for additive manufacturing methods. It has also been shown that within the scope of such additive manufacturing methods with metallic materials, they can form very strong, nearly material-homogeneous connections via interlaced transitional mixing areas. Furthermore, they have the rigidity required for a one-piece lever and are very inexpensive. However, they are completely unsuitable for joints, so here metals, in particular Or a copper-beryllium alloy is preferably used as the second material here.
[0023] Another advantage of ceramic materials is their electrical insulation properties. Therefore, in a modification of the above-mentioned embodiment, in which the first material and the second material are respectively metallic materials, it can be provided that the lever adjacent to one of the lamella joints on both sides contains an electrical conductor track made of the second material, which passes through the lever and is connected to the second material of the lamella joint in a material-uniform manner and is surrounded by the first material. In this way, a conductor track can be realized that passes through the lever and the lamella located between the levers. This conductor track can be used to guide measurement or control signals or for electrical energy supply. At least in the lever area, the conductor track is insulated from its surroundings by the ceramic sheath that surrounds it. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Other details and advantages of the present invention are derived from the following detailed description and accompanying drawings, in which:
[0025] Figure 1 A sectional view showing a section of a blank of a weighing system according to a first embodiment of the invention,
[0026] FIG. 2 shows the structure of a laser beam after mechanical final processing (sub-figure a) or laser optical final processing (sub-figure b). Figure 1 A cross-sectional view of a weighing system produced from a weighing system blank,
[0027] Figure 3 A sectional view showing a section of a weighing system blank according to a second embodiment of the invention,
[0028] FIG. 4 shows the structure of a laser beam after mechanical final processing (sub-figure a) or laser optical final processing (sub-figure b). Figure 3 A cross-sectional view of a weighing system produced from a weighing system blank,
[0029] Figure 5 A sectional view showing a section of a weighing system blank according to a third embodiment of the invention,
[0030] Figure 6 A perspective view of a weighing system according to a preferred development of the invention is shown, and
[0031] Figure 7 Show Figure 6 Cross-section of a weighing system.
[0032] The same reference numbers in the drawings identify the same or similar elements. DETAILED DESCRIPTION
[0033] Within the scope of the manufacturing method according to the invention, a weighing system blank 10 is first produced by means of an additive manufacturing method. Different materials or different material combinations are used for different regions of the weighing system blank 10. Subsequently, a subtractive final processing of the weighing system blank 10 is carried out, which results in the production of a finished weighing system 100. Figure 1 and 3 In a very schematic illustration, illustrative sections of weighing system blanks 10 of different configurations are shown. FIGS. 2 and 4 show the various final processing techniques that can be used to produce a weighing system blank 10. Figure 1 and 3 A weighing system 100 is produced from a weighing system blank 10 of the type shown in FIG. A section of a weighing system blank 10 or a weighing system 100 is shown, respectively, which comprises the intended laminar joint region 11 or laminar joint 110 and the intended lever region 12 or lever 120 adjoining on both sides, respectively. In this case, only the end region of the intended lever region 12 or lever 120 directly adjoining the intended laminar joint region 11 or laminar joint 110 is shown.
[0034] exist Figure 1 A sandwich-like layer structure has been realized in the weighing system blank 10 of FIG. An inner layer made of a second material 22 is embedded between two outer layers made of a first material 21. The first material 21, for example stainless steel or a copper-nickel-zinc alloy, is selected in such a way that it is optimized for the design of the lever 120 of the weighing system 100. In particular, it should be stable, creep-resistant, inexpensive and preferably easy to process. In contrast, the second material 22, for example Or copper-beryllium alloy is selected as follows, that is, so that it is optimized for the design of the thin-film joint 110. In particular, the spring characteristics desired in the individual case have the highest priority in the selection of materials. Those skilled in the art will understand that Figure 1 The relative layer thicknesses of the materials 21 , 22 are not to be understood to be to scale. In particular, in practice, the outer layer made of the first material 21 is usually much thicker than the inner layer made of the second material 22 .
[0035] Figure 1 The enlarged circle shown in the upper right of the figure illustrates the special features of the additive manufacturing method. By gradually superimposing and mixing the initial powders composed of materials 21 and 22 for building the weighing system blank 10, a transition region can be provided between the layers, in which the materials 21 and 22 penetrate and form a nearly material homogeneous structure despite the presence of different initial materials. By selectively synchronizing the powder input and powder application during additive manufacturing, the thickness and material gradient in this transition region can be precisely adjusted.
[0036] According to the invention, the weighing system blank 10 is then finished, wherein in particular the intended lamella joint region 11 is transformed into a lamella joint 110. According to the invention, this is done by means of a subtractive machining method, i.e. by material removal. The intended lever region 12 is also transformed into a lever 120.
[0037] Final processing can be performed in different ways. Figure 2a A typical final machining result by milling is shown. Figure 2b The results of a typical laser optical final processing are shown. Other subtractive processing methods, such as electro-erosion, can also be used within the scope of the invention.
[0038] Figure 3 An alternative embodiment of a weighing system blank 10 is shown. Figure 3 In the additive manufacturing of the weighing system blank 10, the different materials 21, 22 are not applied in layers, but are applied alternately in sections. Figure 3 As shown in the enlarged circle at the top right, here too, a nearly material-homogeneous transition is obtained, which ensures a staggered and secure anchoring of the different material regions. Figure 3In the embodiment of the invention, the intended lever region 12 is made almost completely of the first material 21, while the intended foil joint region 11 is made completely of the second material 22. In the preferred embodiment shown, however, the transition region between the materials 21, 22 is significantly shifted into the intended lever region 12. This has the result that the intended foil joint region 11 is actually composed only of the second material 22 optimized for the joint function. "Inhomogeneities" in the material represented by the transition region (which, if positioned in the finished foil joint 110, could adversely affect the joint function) are unimportant in the region of the lever 120, which must be essentially stable and, in particular, resistant to bending.
[0039] FIG. 4 shows the final machining according to the invention, ie in particular the final machining by milling (see FIG. Figure 4a ) and laser optical final processing (sub Figure 4b ), with regard to FIG. 4 , reference may be made fully to the contents mentioned above in the text of FIG. 2 .
[0040] Figure 5 An alternative embodiment of the weighing system blank 10 according to the invention for the above-described anchoring of the material layers by a continuous material transition is shown. Here, the boundary area between the layers of the first material 21 and the second material 22 is formed as a clear boundary surface, wherein the inner layer of the second material 22 has a mushroom-shaped undercut anchoring portion 24, which extends into the adjacent layer and is surrounded there by the first material 21 in a form-fitting manner. Such anchoring portions 24 can be arranged distributed over the entire boundary surface in order to ensure a permanent and firm connection between the individual material layers.
[0041] Figure 6 and Figure 7 A different illustration of a development of the invention is shown, in which the lever 120 adjacent to the foil joint 110 marked by a thick circle is substantially made of a ceramic material. However, the lever has a track made of a metallic material running through it, and the foil joint 110 is also substantially made of this metallic material. In this way, it is possible to extend the conductor track 130 ( Figure 6 ), the conductor tracks can be used (at least in the region of the lever 120) to measure or control the insulated conduction of an electric current or to power specific components.
[0042] Of course, the embodiments discussed in the detailed description and shown in the drawings represent only illustrative examples of the invention. Based on the present disclosure, the person skilled in the art is provided with a wide range of variation possibilities. In particular, the invention is not limited to the use of exactly two different materials 21, 22. Of course, three or more different materials can also be used in different spatial configurations. The invention is also not limited to the use of metallic materials. In particular, the use of ceramics, in particular for the intended lever area 12 or lever 120, has proven to be advantageous. The person skilled in the art will also appreciate that different areas of one and the same weighing system blank 10 can be arranged in different ways, for example according to Figure 1 and 3 The exemplary embodiment is designed so that different laminar joints 110 or levers 120 adjoining thereto can be implemented in one and the same weighing system 100 .
[0043] Reference numerals list
[0044] 10 Weighing system blank
[0045] 11 Lamellar joint area
[0046] 12 Leverage Area
[0047] 21 First Material
[0048] 22 Second Material
[0049] 100 Weighing system
[0050] 110 Thin-blade joint
[0051] 120 Leverage
Claims
1. Monolithic weighing system (100), The monolithic weighing system comprises a plurality of levers (120) which are connected to each other by means of a laminar joint (110), wherein: The lever (120) on the one hand and the laminar joint (110) on the other hand consist of different materials or material combinations, and the lever (120) adjoining one of the laminar joints (110) on both sides comprises a first material (21), and the laminar joint (110) comprises a second material (22) different from the first material (21), The monolithic weighing system is obtained by: - an additive manufacturing method, in which different materials, including the first and second materials (21, 22) mentioned, are applied in layers and connected to form an integral weighing system blank (10), wherein the weighing system blank (10) has a desired lever area (12) and a desired foil joint area (11), and - Subsequent subtractive final processing of the weighing system blank (10) at least in the expected laminar joint region (11) in order to obtain the weighing system (100).
2. The single-body weighing system (100) according to claim 1, characterized in that: The subtractive final processing is performed mechanically.
3. The single-body weighing system (100) according to claim 1 or 2, characterized in that: The subtractive final processing is performed laser optically.
4. The single-body weighing system (100) according to claim 1 or 2, characterized in that: The subtractive final machining is performed by electro-erosion.
5. The single-body weighing system (100) according to claim 1 or 2, characterized in that: An intended foil joint region (11) and an intended lever region (12) adjacent thereto on both sides have two outer layers of a first material (21) and an inner layer of a second material (22) between the outer layers, and within the scope of final processing the outer layers are completely removed in the intended foil joint region (11) while at least partially retaining the inner layer there and in the adjacent intended lever region (12) while at least partially retaining the inner and outer layers.
6. The single-body weighing system (100) according to claim 1 or 2, characterized in that: The lever (120) adjoining the laminar joint (110) on both sides consists predominantly of a first material (21), whereas the laminar joint (110) consists entirely of a second material (22), which gradually transitions into the first material (21) in a transition region within the lever (120).
7. The single-body weighing system (100) according to claim 1 or 2, characterized in that: The first and second materials (21, 22) are metallic materials.
8. The single-body weighing system (100) according to claim 1 or 2, characterized in that: The first material (21) is ceramic, and the second material (22) is a metallic material.
9. The single-body weighing system according to claim 8, characterized in that: A lever adjoining one of the foil joints on both sides contains electrical conductor tracks made of the second material, which pass through the lever and are connected in a materially uniform manner to the second material of the foil joint and are surrounded by the first material.
10. The single-body weighing system (100) according to claim 2, characterized in that: The subtractive final machining is performed by milling.
11. The single-body weighing system (100) according to claim 7, characterized in that: The first material (21) is stainless steel, and the second material (22) is 12. The single-body weighing system (100) according to claim 7, characterized in that: The first material (21) is a copper-nickel-tin alloy, and the second material (22) is a copper-beryllium alloy.
13. The single-body weighing system (100) according to claim 8, characterized in that: The first material (21) is zirconium oxide or aluminum oxide, and the second material (22) is a metal material.
14. Method for producing a monolithic weighing system (100), comprising a plurality of levers (120) which are connected to one another by means of laminar joints (110), wherein: The lever (120) on the one hand and the laminar joint (110) on the other hand consist of different materials or material combinations, and the lever (120) adjoining one of the laminar joints (110) on both sides comprises a first material (21), and the laminar joint (110) comprises a second material (22) different from the first material (21), It is characterized by having the following steps: - manufacturing a weighing system blank (10) by means of an additive manufacturing method, wherein powders consisting of different materials, including the first and second materials (21, 22) mentioned, are sintered to form the weighing system blank (10), wherein the weighing system blank (10) has a desired lever region (12) and a desired lamella joint region (11), and - Subsequent subtractive final processing of the weighing system blank (10) at least in the expected laminar joint region (110) in order to complete the weighing system.