METHOD FOR PRODUCING AN ASSEMBLY OF CALIBRATED PARTS
Patent Information
- Authority / Receiving Office
- MX · MX
- Patent Type
- Patents
- Current Assignee / Owner
- GKN SINTER METALS ENG GMBH
- Filing Date
- 2022-04-05
- Publication Date
- 2026-05-19
Smart Images
Figure MX433732B0
Abstract
Description
METHOD FOR PRODUCING AN ASSEMBLY OF CALIBRATED PARTS t? l Lfrnn / zznz / E / Yi Field of Invention The invention relates to a method for producing an assembly of calibrated parts. The parts are produced, in particular, from a compressed powder material to form green bodies, which are then sintered to form solid working parts (sintered parts). Sintered parts of this type can be further processed by a subsequent compression operation (calibration) to achieve a higher level of dimensional accuracy. Background of the Invention An assembly of parts often comprises a plurality of parts that must be separated from one another at least intermittently, for example, for arrangement and attachment to other components. For instance, connecting rods may be produced as an assembly of parts, where the connecting rod head for attaching the connecting rod to a crankshaft would need to be made of two parts. To produce an assembly of parts, for example, it is common to first produce the assembly from a one-piece workpiece and provide a fracture notch. The one-piece workpiece is fractured (cracked) along the fracture notch, with the Ref. 333077 result of producing two parts, which by means of an individually made fracture surface must be joined again exclusively with the other respective part. During the production of an assembly of powder-formed parts metallurgically, it is known to produce each of the parts of the assembly individually by pressing, sintering them individually, and calibrating them individually. Brief Description of the Invention The object of the present invention is to solve at least partially the problems mentioned in the prior art. In particular, it proposes a method for producing an assembly of parts, wherein the parts are produced from a powdered material by compression and sintering, and optionally by calibration. In this case, the method is intended to achieve high dimensional accuracy of the assembly of parts, while minimizing the complexity of the method. A method having the features of claim 1 contributes to achieving these objectives. Advantageous embodiments are the subject of dependent claims. The features set forth individually in the claims may be combined in any technologically significant manner and may be supplemented by substantive explanatory material in the description and / or details of the figures, with other variants of the embodiment of the invention shown. A method is proposed for producing an assembly of calibrated parts, wherein the assembly comprises at least a first part having a first contact surface and a second part having a second contact surface, wherein, in the assembly, the parts come into contact with each other by means of the contact surfaces. The parts are manufactured in an undercut-free manner, at least in relation to an axial direction, and can, in the assembly of calibrated parts, be displaced relative to each other along the axial direction and along the contact surfaces. The method comprises at least the following steps: a) provide the first part and the second part in each case in the form of a green body, wherein a green body is produced from a powdered material by compression; b) sintering the parts and forming, at least partially, positive bonding material connections between the parts via the contact surfaces; c) arrange the assembly of parts in a calibration tool; d) displace the parts relative to each other along the axial direction in the calibration tool; e) arranging the parts, in order to form the assembly of parts, with contact surfaces that come into mutual contact in the calibration tool; and f) calibrate the assembly of parts by compression and provide the calibrated assembly of parts. The preceding (non-conclusive) subdivision of the method's stages into a) and af) is intended primarily for distinguishing purposes and not to dictate any sequence or dependency. The frequency of the method's stages may also vary. Similarly, the method's stages may overlap at least partially in time. Preferably, method stage f) takes place during stage d) and / or stage e). In particular, stages a) and af) are performed in the sequence indicated. The contact surfaces of the parts extend, in particular, exclusively in planes running parallel to the axial direction. In the assembly arrangement of the parts, the parts come into contact with each other via these contact surfaces. The parts are designed so that they can be displaced relative to each other along the axial direction, sliding against each other via their contact surfaces. For this purpose, the parts are made in an undercut-free manner; that is, the parts can be displaced relative to each other along the axial direction without impediment; therefore, there are no stops against which the parts can collide. The assembly of parts may comprise two or more parts. The parts are provided in the form of green bodies according to step a). A green body refers to a working part that is produced by compressing a powdered starting material. According to step b), the parts are sintered together. To this end, the parts are positioned relative to each other, particularly in the arrangement intended for assembly, and are sintered together. Specifically, sintering involves using a temperature slightly below the melting point of the material used, where the individual particles of the powdered material are bonded together by positive material bonding through so-called sintering necks. In the arrangement of parts in the assembly of parts, the parts come into contact with each other via the provided contact surfaces. According to step c), the sintered parts, which are connected to each other via contact surfaces, are inserted in the form of a part assembly into a calibration tool. A calibration tool (as known) is, in particular, a press or can be incorporated into a press. The assembly of parts can be formed using a calibration tool. The parts of the assembly are compacted, at least partially, by the calibration tool and undergo plastic deformation. In step d), the parts are displaced relative to each other along the axial direction, specifically parallel to the extent of the contact surfaces. The parts are displaced relative to each other by various components of the calibration tool (by one or more lower punches / one or more upper punches). As a result of this displacement, the connections created in step b) between the contact surfaces of the parts are broken. In particular, the parts are displaced to such an extent along the axial direction that the contact surfaces that are in mutual contact still have an overlap of at least 90%, in particular at least 75%, preferably at least 25%, along the axial direction (compared to a 100% overlap of the contact surfaces in the arrangement intended for the assembly of parts). It is also possible for the parts to move to such an extent along the axial direction that the contact surfaces no longer overlap. As a result of the breaking of the positive bonding connections of the material, the parts are once again separated from each other and can move independently of each other after being removed from the calibration tool. In step (e), the parts are moved back and, in particular, positioned relative to each other in the arrangement specified by the parts assembly. However, the arrangement of the parts according to step (b) and step (e) may also differ. In particular, the positions of the parts differ between step (b) and step (e) only in terms of their position along the axial direction. In step f), the calibration of the parts or the assembly of parts takes place. A compaction operation is performed here, specifically to increase dimensional accuracy. This involves plastic deformation of the parts or the assembly of parts. The proposed method allows for high dimensional accuracy of the assembly of parts, since, at the end of the method, the parts are calibrated together (i.e., in a state already joined or arranged to form the assembly of parts) and, optionally, undergo plastic deformation together. Specifically, the parts of one assembly cannot be interchanged with parts from another assembly. Therefore, the parts of one assembly remain assigned to each other at all times (i.e., from powder pressing to form the green body to calibration). In particular, prior to step a), in a step aO), in a common working phase and in a common pressing tool, the parts are compressed from the powdered material to form a first green body and a second green body and are joined together to form the parts assembly, so that the parts are in contact with each other through the contact surfaces. The parts thus produced are supplied in the form of a parts assembly in step a). In particular, to form the respective green body, the first part is compressed in a first working space of the pressing tool and the second part is compressed in a second working space t? l Lfrnn / zznz / E / Yi of the tool. In this case, at least one green body is displaced relative to the other respective working space (or the green body that was already generated by compression), along the axial direction, to form the assembly of parts. A pressing tool (known) comprises, in particular, one or more lower punches and one or more upper punches, and also a die and, optionally, one or more mandrels. In particular, both parts are already present in the form of green bodies before displacement to form the assembly of parts, i.e., both powdery materials in each workspace have already been compressed to form the respective green body. In particular, the compression of the respective green body can take place simultaneously or in parallel. It is also possible to allow the compression of the respective green body to occur with a time lag. In particular, the displacement of the green bodies or the workspaces can also be carried out simultaneously, in parallel, or with a time lag relative to the compression of the materials to form the respective green body. In particular, the workspaces are arranged offset from each other along the axial direction, so that the parts (or workspaces, or powdery materials) do not come into contact with each other during the compression of at least one of the parts to form a green body. It is preferable that at least one green body has already been generated before displacement or before contact between the two workspaces (or the powdered materials contained within them). This essentially prevents the mixing of the powdered materials. In particular, it is therefore possible to maintain or create boundary surfaces (the subsequent contact surfaces), which extend parallel to the axial direction between the green bodies, so that, during calibration, the subsequent separation of the parts along the contact surfaces is possible or guaranteed. In particular, the green bodies are joined together in stage aO) to form a transition fit or even a press fit. A press fit comprises, in particular, a slight overlap of the parts along a direction transverse to the axial direction. A transition fit optionally also allows clearance between the parts along a direction transverse to the axial direction. As a result of the press fit, the parts can be joined together, i.e., moved into the arrangement intended for the parts in the assembly, simply by applying a pressing force. The fit makes it possible for the parts to be handled and transported together in assembly form. Such a method for producing an assembly of parts from green bodies, comprising compressing powdered materials to form green bodies, moving the green bodies relative to each other to form a pressed fit and thereby generating the assembly of parts, is known, for example, from document WO 2011 / 035862 Al. This document describes how partial green bodies are first pressed separately in a pressing tool, then gathered, and subsequently joined. In this case, the separated partial quantities of the powdered substance in the tool are pressed to form two separate partial green bodies and are gathered in the tool in a subsequent working stage. Separate pressing can mean that the partial quantities of the powdered substance are separated from each other in the tool in such a way that two separate working spaces are formed within the tool, and that separate green bodies are produced in these working spaces, which are then referred to as partial green bodies.In this case, it is equally possible that, during the pressing of the partial green bodies, the press punches of the adjacent workspace form a workspace for the other pressed body or respective partial green body. A press punch located in the center of the tool can, in this case, form a cavity in a first workspace for a first partial green body, while the outer press punches for the first partial green body form an outer workspace for a second partial green body, which is formed by means of the central press punch. This method is not limited to simply pressing the two partial green bodies separately; rather, it is also possible to first press one partial green body in a separate, independent first workspace and then transfer this partial green body to the second workspace for the second partial green body.Subsequently, during the pressing of the second partial green body, the first partial green body remains in its working space, so that the joining of the first partial green body to the resulting second partial green body is carried out directly. The joining of the first and second partial green bodies is thus transferred to a working phase of the tool in which the second partial green body is pressed. t? l Lfrnn / zznz / E / Yi The current method, in particular, makes use of the high-precision fit of the green bodies thus produced from the assembly of parts that are subsequently calibrated. Both during compaction itself and during demolding and subsequent handling, the sintered components are at risk of cracking at transverse transitions, due, among other things, to density inhomogeneities and / or axial and radial stresses in the tooling. The risk of cracking at transverse transitions, for example, due to stresses in the green body that occur during the pressing process, is avoided by the method known from WO 2011 / 035862 A1, since the at least two partial green bodies are compacted independently of each other, without disruptive influences at the cross-sectional transitions, and are subsequently joined in one operation.In particular, a particularly preferred fit accuracy is achieved between the partial green bodies to be joined. If the green body (i.e., the green bodies forming the part assembly) is sintered after demolding from the pressing tool (and optionally after further processing stages), the high fit accuracy of the green bodies with each other results in sintering on the contact surfaces of the green bodies. The fit accuracy can influence the intensity of sintering. In the case of a transition fit, a lower degree of sintering is expected than in the case of a press fit. In particular, after the assembly of parts has been formed in step aO), the parts are provided in the form of an assembly of parts in step a) and are sintered in the form of an assembly of parts in step b). Specifically, the green bodies are no longer separated from each other before insertion into the calibration tool. The high fit accuracy of the part assembly (both with the green bodies joined and with the sintered workpiece) can therefore be used for calibration or for subsequent use of the parts as a part assembly. In particular, the first part and the second part are produced from an identical powdered material. Furthermore, a parts assembly, produced by the described method, is proposed. The calibrated parts assembly comprises at least a first part having a first contact surface and a second part having a second contact surface, wherein, in the parts assembly, the parts come into contact with each other via the contact surfaces. The parts are made in a recess-free manner, at least in relation to an axial direction, and, in the calibrated parts assembly, they can be displaced relative to each other at least along the axial direction and along the contact surfaces. Specifically, to separate or assemble parts, the parts can be moved relative to each other only along the axial direction. In particular, the parts are therefore provided with geometric structures that, in relation to a radial and / or circumferential direction, create a form-fitting connection between the parts. In particular, in order to separate or assemble parts, the parts can be moved relative to each other along the radial direction. Specifically, the parts are provided with geometric structures that, in relation to other radial directions and / or a circumferential direction, create a form-fitting connection between the parts. In particular, there may be minimal undercut in relation to a radial direction, which can be overcome by elastic deformation so that the radial connection is possible. In particular, the assembly of parts is of a ring-shaped modality, in which each part forms a ring segment that extends along a circumferential direction t? l Lfrnn / zznz / E / Yi. In particular, the parts are configured so that they are identical to each other (or alternatively to differ from one another) in terms of their geometric design. The resulting assembly of parts can be produced with high dimensional accuracy, whereby the parts, already assembled to form the assembly, can be made available for further use. The statements made regarding the method may apply in particular to the assembly of parts and vice versa in each case. It is noted as a precaution that the numerical terms used here (first, second, ...) serve primarily (only) to distinguish between several similar objects, dimensions, or processes; that is, they do not imperatively specify any dependency and / or sequence of these objects, dimensions, or processes in relation to one another. Should a dependency and / or sequence be necessary, this is explicitly stated here, or it is obvious to a person skilled in the art upon studying the specifically described modality. If a component can occur more than once (at least once), the description relating to one of these components may be similarly applied to all or some of the plurality of these components, but this is not mandatory. t? l Lfrnn / zznz / E / Yi Brief Description of the Figures The invention and its technical field will be explained in more detail below, based on the accompanying figures. It should be noted that the invention is not intended to be limited by the illustrative embodiments mentioned. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the substantive issue explained in the figures and combine them with other parts and conclusions of this description. In particular, it should be noted that the figures, and especially the size proportions illustrated, are only schematic. In the figures: Figure 1 shows a known method for producing green bodies; Figure 2 shows an assembly of parts in a view along an axial direction; Figure 3 shows a perspective view of the assembly of parts in accordance with Figure 2; Figure 4 shows the assembly of parts according to Figure 2: Figure 5 shows a perspective view of the assembly of parts according to Figures 2 to 4, with the parts having been displaced relative to each other along the axial direction; and Figure 6 shows a side elevation view t? l Lfrnn / zznz / E / Yi of the assembly of parts in accordance with Figures 4 and 5. Detailed Description of the Invention Figure 1 shows a method for producing green bodies 7, 8 known from WO 2011 / 035862 A1. Such a method for producing a part assembly 1 from green bodies 7, 8 consists of pressing powdered materials 9 to form green bodies 7, 8, displacing / moving the green bodies 7, 8 relative to each other to form a pressed fit and thereby generating the part assembly 1. The pressing tool 11 comprises a die 16, a first upper punch 17, a second upper punch 18, a first lower punch 19, and a second lower punch 20. According to step A of the illustrated method, the lower punches 19, 20 are displaced in the die 16 and the powdered material 9 is disposed of. In step B, the upper punches 17, 18 are disposed of in the die 16 and all the punches 17, 18, 19, 20 are displaced relative to each other such that a first working space 12 and a second working space 13 are formed, comprising materials 9 that are separated from each other. In stage C, the materials 9 in the workspaces 12, 13 are pressed to form the green bodies 7, 8. In stage D, the green bodies 7, 8 are joined together by the displacement of the punches 17, 18, 19, 20. In stage E, the assembly of parts 1 formed by the green bodies 7, 8 is ejected. Therefore, the green bodies 7 and 8 are first pressed separately in a pressing tool 11, then brought together, and subsequently joined. In this case, the separate portions of the powdered material 9 in the pressing tool 11 are compressed to form two separate green bodies 7 and 8 and are brought together in the pressing tool 11 in a subsequent working stage. During the compression of the green bodies 7 and 8, the punches 17 and 19 in the adjacent working space 12 form a working space 13 for the other respective green body 8. A punch 17 and 19 arranged in the center of the pressing tool 11 can, in this case, form a cavity in a second working space 13 surrounding these punches 17 and 19, so that the first green body 7 generated in the first working space 12 can be inserted into this cavity during joining.The outer punches 18, 20 form the second outer working space 13 for the second green body 8. Figure 2 shows an assembly of parts 1 in a view along an axial direction 6. Figure 3 shows a perspective view of the assembly of parts 1 according to Figure 2. Figure 4 shows the assembly of parts 1 according to Figure 2. Figure 5 shows a perspective view of the assembly of parts 1 according to Figures 2 to 4 with parts 2, 4 having been displaced relative to each other along the axial direction 6. Figure 6 shows a side elevation view of the assembly of parts 1 according to Figures 4 and 5. Figures 2 to 6 will be described together below. The calibrated part assembly 1 comprises a first part 2 having a first contact surface 3 and a second part 4 having a second contact surface 5, and also a third part 21, wherein, in the assembly of parts 1, parts 2, 4, and 21 are in contact with each other via contact surfaces 3 and 5. Parts 2, 4, and 21 are each of identical type. Parts 2, 4, and 21 are made free from undercuts with respect to an axial direction 6 and can, in the assembly of calibrated parts 1, be displaced relative to each other only along the axial direction 6 and along contact surfaces 3 and 5. Parts 2, 4, 21 are provided with geometric structures (in the manner of a so-called dovetail connection in this case) which, in relation to a radial direction 22 and a circumferential direction 14, produce a form-carrying connection of parts 2, 4, 21. The assembly of parts 1 is of a ring-shaped form, t? l Lfrnn / zznz / E / Yi in which each part 2, 4, 21 forms a ring segment extending along the circumferential direction 14. In the course of the method, in step aO), in a common operation and in a common pressing tool 11, a first green body 7 and a second green body 8 (and also a third green body) are generated from the powdered material 9 by means of pressure (see Figure 1, steps A, B, C). The three green bodies 7, 8 are joined together to form the assembly of parts 1 (see Figure 1, step D), so that the green bodies 7, 8 (or parts 2, 4, 21) come into contact with each other by way of the contact surfaces 3, 5. The parts 2, 4 and 21 produced in this way are provided in the form of assembly of parts 1 in step a) (see Figure 1, step E and Figures 2 and 3). According to step a), parts 2, 4, and 21 are each provided in the form of a green body 7, 8, whereby a green body 7, 8 is produced from a powdered material 9 by pressing. According to step b), parts 2, 4, and 21 are sintered, and bonded connections are formed between parts 2, 4, and 21 via contact surfaces 3 and 5 (e.g., Figures 2 and 3). According to step c), the assembly of parts 1 is arranged in a calibration tool. 10. According to step d), parts 2, 4, 21 are displaced relative to each other along the axial direction 6 in the calibration tool 10 (see Figures 4 to 6; calibration tool, for example, designed according to the pressing tool 11 in accordance with Figure 1; shown only in Figures 4 to 6). According to step e), parts 2, 4, 21 are arranged to form the parts assembly 1, with contact surfaces in mutual contact 3, 5 in the calibration tool 10 (for example, according to Figures 2 and 3), and according to step f), the parts assembly 1 is calibrated by applying pressure and the calibrated parts assembly 1 is provided (for example, according to Figures 2 and 3). The contact surfaces 3, 5 of parts 2, 4, 21 extend exclusively in planes running parallel to the axial direction 6. Parts 2, 4, 21 are designed so that they can be displaced relative to each other along the axial direction 6, in which parts 2, 4, 21 slide against each other by way of the contact surfaces 3, 5. For this purpose, parts 2, 4, 21 are made in an undercut-free manner, i.e., parts 2, 4, 21 can be displaced relative to each other along the axial direction 6 without impediment. t? l Lfrnn / zznz / E / Yi In step d), parts 2, 4, 21 are displaced relative to each other along the axial direction 6. Parts 2, 4, 21 are displaced relative to each other by various components of the calibration tool 10 (for example, by one or more lower punches 19, 20 / one or more upper punches 17, 18; see, for example, Figure 1). As a result of the displacement, the connections generated in step b) between the contact surfaces 3, 5 of parts 2, 4, 21 are broken. In this case, parts 2, 4, 21 are displaced to such an extent along the axial direction 6 that the mutual contact surfaces 3, 5 still have an overlap 23 of at least 25% along the axial direction 6 (see figures 4 to 6), compared to an overlap 23 of 100% of the contact surfaces 3, 5 in the arrangement provided for the assembly of parts 1 (see figures 2 and 3). In step e), parts 2, 4, 21 are moved (back) again and, in particular, placed relative to each other in the arrangement provided by the assembly of parts 1. However, the arrangement of parts 2, 4, 21 according to step b) and step e) may also differ from each other. In step f), parts 2, 4, 21 or the assembly of parts are calibrated. Here, a subsequent compaction operation is performed, in particular to increase the dimensional accuracy. In particular, this involves the plastic deformation of parts 2, 4, 21 or the assembly of parts 1. List of reference symbols Assembly of parts Part One First contact surface Part Two Second contact surface Axial direction First green body Second green body Material Calibration tool Pressing tool First workspace Second workspace Peripheral management Pressing direction Matrix First upper punch Second upper punch First lower punch Second lower punch Third part you? l Lfrnn / zznz / E / Yi Radial direction Overlap It is hereby stated that, as of this date, the best method known to the applicant for putting the aforementioned invention into practice is the one that is clear from the present description of the invention.
Claims
1. A method for producing an assembly of calibrated parts, characterized in that it comprises at least a first part having a first contact surface and a second part having a second contact surface, wherein, in the assembly of the parts, the parts come into contact with each other by way of the contact surfaces; wherein the parts are made free from undercuts, at least in relation to an axial direction, and can, in the assembly of calibrated parts, be displaced relative to each other along the axial direction and along the contact surfaces; wherein the method comprises at least the following steps: a) providing the first part and the second part in each case in the form of a green body, wherein a green body is produced from a powdered material by compression; b) sintering the parts and at least forming material bonding connections between the parts by way of the contact surfaces;c) arranging the assembly of parts in a calibration tool; d) displacing the parts relative to each other along the axial direction in the calibration tool; e) arranging the parts, in order to form the assembly of parts, with contact surfaces in mutual contact in the calibration tool; and f) calibrating the assembly of parts by compression and providing the calibrated assembly of parts.
2. A method according to claim 1, characterized in that prior to step a), in a step aO), in a common operation and in a common pressing tool, the parts are compressed from the powdered material to form a first green body and a second green body and are joined together to form the assembly of parts, such that the parts come into contact with each other by way of the contact surfaces; wherein the parts are provided in the form of an assembly of parts in step a).
3. Method according to claim 2, characterized in that, to form the respective green body, the first part is compressed in a first working space of the pressing tool and the second part is compressed in a second working space of the pressing tool; wherein at least one green body is displaced relative to the other respective working space, along the axial direction, to form the assembly of parts.
4. Method according to claim 3, characterized in that both parts are present in the form of green bodies prior to displacement to form the assembly of parts.
5. A method in accordance with any of the preceding claims 3 and 4, characterized in that the working spaces are arranged offset relative to each other along the axial direction, so that the parts do not come into contact with each other during the compression of at least one part to form a green body.
6. Method in accordance with any of the preceding claims 2 to 5, characterized in that the green bodies are joined together in step aO) to form a press fit or a transition fit.
7. Method in accordance with any of the preceding claims 2 to 6, characterized in that, once the assembly of parts has been formed in step aO), the parts are provided in the form of an assembly of parts in step a) and are sintered in the form of an assembly of parts in step b).
8. Method in accordance with any of the preceding claims 1 to 7, characterized in that the first part and the second part are produced from an identical powdered material.
9. Assembly of parts, produced by a method according to any of the preceding claims, characterized in that it comprises at least a first part having a first contact surface and a second part having a second contact surface, wherein, in the assembly of parts, the parts come into mutual contact by way of the contact surfaces; wherein the parts are made free from undercuts, at least in relation to an axial direction and can, in the assembly of calibrated parts, be displaced relative to one another at least along the axial direction and along the contact surfaces.
10. Assembly of parts according to claim 9, characterized in that, to produce the assembly of parts, the parts can be moved relative to each other exclusively along the axial direction.
11. Assembly of parts in accordance with any of the preceding claims 9 and 10, characterized in that, to separate the assembly of parts, the parts can be moved relative to each other exclusively along the axial direction.
12. Assembly of parts in accordance with any of the preceding claims 9 to 11, characterized in that the assembly of parts is ring-shaped, wherein each part forms a ring segment extending along a circumferential direction.
13. Assembly of parts in accordance with any of the preceding claims 9 to 12, characterized in that the parts are identical to each other in terms of their geometric design.