Bonding of lamella packs with 2K adhesives using inkjet technology

Abstract

In a method for manufacturing a sheet metal lamella pack (4) for an electric machine, sheet metal lamellae (22) are produced from a sheet (12) in stamping steps (SSa-d), an adhesive (36) with at least two mutually reactive components (37a,b) is applied to at least one flat side (40a,b) of the sheet metal lamellae (22) in printing steps (DSa,b) using printheads (30a-e) in an inkjet process, wherein each of the components (37a,b) is dispensed separately from one of the printheads (30a,b) without premixing, and in a stacking step (SA) the sheet metal lamellae (22) are stacked on top of each other to form the lamella pack (4) and bonded together by means of the adhesive (36). A manufacturing unit (2) for producing the sheet metal lamella package (4) includes a punching module (20a-d) for the punching steps (SSa-d), printing modules (28a,b) with printheads (30a,b) for the printing steps (DSa,b) and a stacking module (31) for the stacking step (AS).

Description

[0001] The invention relates to laminated lamination packs for electrical machines, e.g. packs for rotors or stators of electric motors.

[0002] WO 2019 / 086634 A1 discloses a method for producing an electrical steel sheet stack using an anaerobic-curing adhesive, an electrical steel sheet stack produced or producible by such a method, and a device for producing an electrical steel sheet stack. During the production process, the anaerobic-curing adhesive is activated by rubbing the electrical steel strip with a rubbing device comprising a surface structure containing beryllium and / or transition metals, preferably copper-containing surface structures. In a preferred embodiment, the rubbing device is a brush.

[0003] The object of the present invention is to improve the bonding of lamination packs.

[0004] The object of the invention is achieved by a method according to patent claim 1. Preferred or advantageous embodiments of the invention and other categories of invention emerge from the further claims, the following description and the attached figures.

[0005] The method is used or is designed to produce a laminated core stack for an electrical machine. Such a stack is also simply called a "laminated core stack." The laminated core stack contains a plurality or multiplicity of, in particular, comparatively thin, flat, identical laminated cores or "laminations," each having two parallel flat sides. The cores are stacked on top of one another in alignment, flat side to flat side, and two adjacent cores are glued together on each flat side.

[0006] In the process, at least two sheet metal laminations are manufactured. In particular, a plurality of sheet metal laminations is produced. Each of the sheet metal laminations has two opposing flat sides. The sheet metal laminations are manufactured in such a way that each of the sheet metal laminations is produced from a sheet metal in at least one punching step. Typically, several punching steps are required to produce each sheet metal lamination. The punching steps are, in particular, part of a continuous punching process as part of a manufacturing process, which also includes, in particular, the bonding of the sheet metal laminations to one another and their packaging to form the sheet metal lamination package, as explained further below.

[0007] In the process, an adhesive is also printed in at least one printing step onto at least one, in particular exactly one, flat side of each sheet metal lamination to be bonded. In particular, the first or last sheet metal lamination of a sheet metal lamination stack remains adhesive-free, since the adhesive is already applied to the bonding partner, namely the adjacent sheet metal lamination.

[0008] In the process, the adhesive is applied to the respective sheet metal lamella or its flat side in the respective printing step by printing it using at least one print head in an inkjet process, i.e., using inkjet technology. In the printing step, the sheet metal lamella may already be present in a separate form or may still be part of the sheet metal, for example, a sheet metal strip, from which the sheet metal lamella is ultimately manufactured or separated.

[0009] Several print heads can be combined in a print module, which specifically defines their relative spatial arrangement.

[0010] Inkjet technology is understood as follows: Adhesive is applied to the flat side of the sheet, similar to the application of ink to a printing substrate, using an inkjet printer (also called droplet-jet printer, inkjet printer, color jet printer, and inkjet printer). The adhesive is thus applied in a matrix printing process, in which a printed image, in this case an "adhesive image" / "adhesive application," is created by the targeted firing of small ink nozzles (here adhesive nozzles) or the deflection of small ink droplets (adhesive droplets).

[0011] Such printers, in this case print heads, belong to the group of non-impact printers / print heads, meaning they do not come into contact with the flat surface during adhesive application. In other words, the adhesive is applied to the flat surface "through the air." For such print heads, see the explanations for inkjet printers, e.g., at https: / / de.wikipedia.org / wiki / Tintstrahldrucker.

[0012] The adhesive has at least two adhesive components ("components"). These are reactively formed with one another, meaning that the actual adhesive effect of the adhesive only develops when the two components are mixed. In particular, the adhesive has exactly two components. This can be a "classic" 2-component adhesive. In this case, the components must be mixed in a specified stoichiometric mixing ratio (range with tolerances) to produce an adhesive with the desired adhesive effect. Overdosing or underdosing the second component will result in no effective adhesive effect.

[0013] However, it may also be a so-called NoMix adhesive as the first component, which requires an activator as the second component. While the activator is essential here to achieve the desired bonding effect, an overdose may not harm the bonding effect. In practice, it is common practice to simply add more activator than required to simplify dosing, as, unlike a "classic 2-component adhesive," excess activator as the second component is harmless to the bonding effect. However, overdose can also be harmful. In any case, an exact mixing ratio is not required.

[0014] In this case, each of the components is printed individually from one of the print heads. The second component can be printed from the same print head as the first or from a different print head. Different print heads can be located in the same or different print modules.

[0015] The output from the print heads occurs without pre-mixing the components in or (in the sense of a flow of components upstream) in front of the print head(s). In other words, the pure (at least two), unmixed components are dispensed from the print heads. They only mix / touch / contact after they have been output from the print head. In particular, this only takes place on the surface of the metal lamella. The mixing occurs, for example, through at least partial overlap / overprinting, i.e. printing the components at the same place or so close together that components at least partially overlap. Alternatively or additionally, the mixing can also occur or be intensified by joining the metal lamella printed with the components to a neighboring lamella later after the printing. The mixing is therefore achieved, for example, by pressure when two lamellas are pressed against each other orthe flow of the (liquid) components on the sheet metal lamella is achieved or enhanced.

[0016] In particular, the first component is applied to one flat side of the sheet metal lamination, and the second component is applied to the other flat side. This ensures that the components are mixed and thus react to form the adhesive only at the moment the two sheet metal laminations are joined together. However, from a process perspective, applying both components to the same side is more advantageous and is optionally available here.

[0017] Suitable printheads are commercially available, for example, from Xaar (Xaar plc Headquarters, 3950 Cambridge Research Park, Waterbeach, Cambridge, CB25 9PE, United Kingdom), https: / / www.xaar.com / de / produkte / xaar-druckköpfe. Any adhesive can be used as long as it can be applied using such printheads using the inkjet process. Alternatively or additionally, application using a LIFT (Laser Induced Forward Transfer) application system is also conceivable. A combination of inkjet and LIFT for the various components is also conceivable.

[0018] The LIFT technology is to be understood here as follows: From “Laser-Induced Forward Transfer: A Method for Printing Functional Inks”, by J. Marcos Fernandez-Pradas and Pere Serra, Crystals 2020, 10(8), 651; Published: July 29, 2020, downloaded on April 25, 2023 from https: / / www.mdpi.com / 2073-4352 / 10 / 8 / 651, the following is known: Laser-induced forward transfer (LIFT) is a direct-printing process based on the action of a laser, which prints a small portion of a material from a thin donor layer onto a receiving substrate. Since the process's inception, solid donor layers or foils have been used, but the same operating principle also works with liquid ink films. LIFT is a nozzle-free printing process that has virtually no restrictions on the particle size and viscosity of the ink to be printed.Therefore, LIFT is a versatile process that can be used to print any functional material for which an ink can be formulated.

[0019] The process also includes a stacking step, which follows the punching and printing steps, i.e., only takes place after these steps have been completed. The sheet metal laminations to be bonded, which are printed with adhesive on the flat side, are stacked on top of each other to form the lamination stack and bonded together using the adhesive. If necessary, the sheet metal laminations are also pressed against each other during the stacking step to achieve a defined bond.

[0020] The application of the adhesive for bonding sheet metal laminations to laminated cores for electric motors using inkjet technology allows extremely flexible dosing of the adhesive on the flat side and enables bonding over the largest possible area, as the adhesive can be applied, for example, right up to the edge of the lamination, see below. This is advantageous for the further development of the sheet metal composite, as the mechanical strength in particular can be achieved very well in an inline process. According to the invention, an application of multi-component, in particular 2K adhesives, for sheet metal lamination bonding is achieved. This results in the use of inkjet printing technology for the application of multi-component, in particular two-component adhesives over large areas for very thin adhesive layers. This is essential for the industrial use of this class of adhesive. The invention enables the development of 2K adhesives for laminated core production.Premixed multi-component adhesives must be dispensed and bonded within a defined open time. If the open time is exceeded, the properties of the adhesive change significantly due to the ongoing chemical curing reaction (e.g., viscosity increase). Micro-dosing of premixed adhesives (e.g., 2-component adhesives), as required for the described application, cannot be reliably implemented using conventional dispensing technologies. Process interruptions can lead to the adhesive curing in the dispensing unit, rendering it unusable or requiring extensive cleaning. Alternatively, regular flushing is required to continuously remove the premixed reactive mixture from the system (within the open time).The invention avoids these problems because the mixing takes place directly on the surface to be bonded, and the reactive components do not remain in the mixed state in the dispensing unit (print head). This is one of the main reasons why the invention opens up this class of adhesive for application.

[0021] In a preferred embodiment, a no-mix adhesive is dispensed as one of the components and an associated activator as another. Thanks to inkjet technology or targeted printing, precise dosing of the activator is possible, so that after reaction with the no-mix adhesive, as little or no excess activator remains. In other words, the activator can be precisely dosed and used in the optimal ratio to the adhesive. Alternatively, the adhesive can be used according to the classic 2K chemistry (fixed mixing ratio).

[0022] In a preferred embodiment, a mixing ratio of at least two of the components is adjusted by metering the output from the print heads. The two components can thus be easily and precisely applied to the metal lamination in the desired ratio. This allows the required ratio to be adjusted particularly precisely for both "traditional" 2-component adhesives and the NoMix adhesive and activator.

[0023] In a preferred embodiment, at least two of the components are printed as component dots on the flat side or sides in the manner of an alternating dot pattern. In this case, two adjacent component dots are those of different components. The arrangement of the component dots on the flat side corresponds in particular to a checkerboard pattern, i.e., is staggered in rows. In particular, the component dots are adjacent to one another, i.e., touch one another or at least partially overlap. This results in a homogeneous distribution and optimal conditions for thorough mixing of the two components on the flat side, at least during or after the flat side is pressed against the adhesive partner, i.e., the adjacent flat side in the stack. The "checkerboard" pattern is not necessarily the ideal situation; directly on top of one another would presumably be better; moreover, partial or spot bonding is also possible.

[0024] In a preferred embodiment, the sheet metal is provided as a strip or strip material with both flat sides. This allows the invention to be integrated into a conventional strip production process for sheet metal lamination packs.

[0025] In a preferred variant of this embodiment, the punching steps, the printing steps, and the stacking step are carried out as a continuous inline process using the strip / material as the starting material. The process continues on the strip material until the laminations are separated from the strip material. The process then continues on the separated laminations, but in the present sense, it still represents a continuous inline process "on the strip material." This allows for particularly efficient production of laminated cores.

[0026] In a preferred embodiment, at least two punching steps are performed consecutively, and at least one printing step is performed between two of the punching steps. This allows the adhesive application to be integrated particularly favorably into the punching process.

[0027] The adhesive can be applied in any desired pattern, e.g. from spot to large or full-surface.

[0028] In a preferred embodiment, the adhesive is printed onto the entire respective flat side of at least one, preferably all of the sheet metal laminations (except for those not to be printed). “Entire flat side” is to be understood here in the technical sense. In this case, for example, a very small edge area of ​​the sheet metal lamination can be left free compared to the surface so that the adhesive does not interfere with further processing steps of the sheet metal laminations during further production of the sheet metal stack or ooze out of the sides of the sheet metal stack. By leaving the edge area free of adhesive, tolerances in the amount of adhesive applied, in the viscosity as well as manufacturing inaccuracies, etc. can be taken into account in the technical sense and yet a full-surface bonding of the sheet metal laminations can be achieved in the technical sense. Appropriately bonded sheet metal laminations contribute to a particularly stable and media-tight lamination stack.

[0029] In a preferred embodiment, the adhesive is printed onto at least one, in particular all of the respective metal laminations in at least, in particular exactly two consecutive printing steps. The adhesive is printed sequentially, in particular by means of at least, in particular exactly two different print heads. Initially, only a portion of the adhesive is printed in a first partial printing step. Only later do further partial printing steps follow, in which the remaining adhesive is applied to the same lamination. Parts of the adhesive application therefore take place at different times and / or from different print heads, in particular with an intermediate time pause. This makes it possible, for example, to achieve an increased process speed that would not be achievable with one print head / single continuous print alone, e.g.because a print head alone is not capable of printing at the required speed.

[0030] In a preferred embodiment, the two components are dispensed from different print heads. Optionally, these can also be print heads from different print modules, meaning the components are then also dispensed from different print modules. For example, a specially adapted print head can be used for each component to optimally adapt the output to the respective component's properties (e.g., viscosity).

[0031] In a preferred embodiment, the method is carried out with the aid of or in a manufacturing facility (see below). This facility has a stationary base frame—e.g., in a production facility. At least one of the print heads is stationary during at least one of the printing steps, i.e., printing in or on / relative to the base frame. In particular, the metal lamination is moved relative to the print head during printing, i.e., during printing. Alternatively, the metal lamination can also remain stationary during printing. This allows for a particularly simple print head structure.

[0032] In a preferred embodiment, the method is also carried out with the aid of or in the aforementioned production system. At least one of the print heads moves relative to the base frame during at least one of the printing steps, i.e., the printing itself. The sheet metal lamination itself can also move during printing or remain stationary relative to the base frame. This allows for particularly flexible printing.

[0033] In a preferred variant of this embodiment, at least one of the print heads moves during at least one of the printing steps, i.e., printing, in at least one direction of movement relative to the base frame, in particular exactly one direction that is not parallel to a transport direction of the sheet metal lamination. In particular, it moves in a direction of movement that is transverse or perpendicular to the transport direction. In particular, it moves in a direction of movement that runs parallel to the flat side of the sheet metal lamination to be printed. This enables particularly effective printing. The direction / path of movement of the print head is in particular a straight line. In particular, this movement is the only one of the print head relative to the base frame. Alternatively, a combination with other movements can be carried out.

[0034] In a preferred variant of this embodiment, at least one of the print heads moves by rotating about at least, in particular exactly, one axis of rotation relative to the base frame during printing. The axis of rotation is in particular perpendicular to the transport direction of the slats, in particular perpendicular to a plane of extension of the flat side of the slats or sheet / strip to be printed. This also allows particularly effective printing of the slats. The print head can, for example, perform one rotation / turn per printing process or continue to rotate continuously - even during non-printing times. In the latter case, there is no need for any acceleration during the printing process.

[0035] The object of the invention is also achieved by a manufacturing device according to patent claim 15. This serves or is configured to produce the above-mentioned laminated lamination stack for the electrical machine according to the above-mentioned method. The manufacturing device contains at least one punching module. The punching modules as a whole are configured to carry out the punching steps explained above. The manufacturing device contains at least one printing module. Each of the printing modules contains at least one of the above-mentioned print heads. The printing modules as a whole are configured to carry out the above-mentioned printing steps. The manufacturing device contains a stacking module. This is configured to carry out the above-mentioned stacking step. In particular, the manufacturing device also contains a curing module for curing the adhesive.

[0036] The manufacturing facility and at least some of its possible embodiments as well as the respective advantages have already been explained in connection with the method according to the invention.

[0037] In preferred embodiments, the manufacturing facility contains, alternatively or additionally: - the basic framework mentioned above, - at least one transport module for the slats to transport them relative to the base frame.

[0038] In particular, the print head is in a fixed position relative to the base frame. In particular, the print head is movable relative to the base frame at least translationally in the at least one direction of movement. In particular, the print head is rotatable relative to the base frame about the at least one axis of rotation.

[0039] The invention is based on the following findings, observations, and considerations and also includes the following preferred embodiments. These embodiments are sometimes referred to as "the invention" for simplicity. The embodiments may also contain parts or combinations of the above-mentioned embodiments or correspond to them and / or may also include previously unmentioned embodiments.

[0040] The invention is based on the recognition of the following problems: Spot bonding processes for sheet metal stacks are often implemented with two-component adhesives based on anaerobic-curing acrylate adhesives. In the so-called no-mix process, an activator (first component) is applied over the entire surface or a large area to one side of the sheet. The adhesive component belonging to the activator (second component) is applied in a spot pattern to the other side of the sheet. Upon contact, a rapid polymerization reaction occurs. The adhesive layer thickness is < 5 µm (usually between 1-3 µm).

[0041] The activator component is used in a non-stoichiometric ratio to the adhesive (and thus overdosed relative to the lamination area). As a result, some of the activator component remains chemically unreacted and is not securely bonded to the surface. These components can be mobilized during operation of the laminated core, e.g., in the electric motor, and cause problems (e.g., corrosion, conductive layers).

[0042] The upper operating temperature of these adhesives is 150 to 180°C, depending on the variant.

[0043] The known bonding methods mentioned above do not allow for large-scale or full-surface bonding.

[0044] Large-area bonding offers advantages such as higher rigidity, mechanical strength, interlaminar sealing function, and avoidance of local elevation of the sheet stack at the bonding points.

[0045] “Classic” two-component adhesives, on the other hand, i.e. those with a defined mixing ratio that are subject to a polyaddition (e.g. epoxy / amine, epoxy / anhydride) or polycondensation mechanism, must be premixed before the adhesive is applied, which activates them and thus can only be dosed in the necessary small quantities with great effort: • The open time limits the processing time after the mixing process • Mixed volumes must be applied within the open time • Viscosity changes may occur during the open time; this has an influence on the dosing behavior • In case of process interruptions, rinsing dosing steps or cleaning steps of the dosing unit must be carried out • 2K adhesives with a long open time require additional process heat to cure quickly.

[0046] The invention is based on the following solution ideas: • The inventive application method using inkjet printing allows two reactive components to be brought into direct contact with the surface of the component to be bonded. Integration into a linked process reduces the time between adhesive application and the bonding process to very short intervals (e.g., < 0.2 s). • The open time thus becomes less important and the reactivity of the adhesive can be designed in favor of a fast curing rate (e.g. at room temperature or at least much less than 180 °C). • Energy-intensive curing processes (e.g. curing at 180 °C) can be avoided (sustainability aspect) • The homogeneous distribution and the mixing ratio of the first and second components are ensured by the printing process. • The application pattern is almost arbitrary - from spot to almost full-surface • The possible adhesive selection is expanded by the classic 2K chemistry: ◯ Higher temperature resistance and higher temperature resistance (e.g. up to 200 °C) ◯ Improved media resistance • Can also be used for anaerobic curing no-mix adhesives: ◯ Improvement of the degree of curing by avoiding excess components ◯ Low risk of contamination from uncured adhesive components • Premature curing of the adhesive within the dosing unit is avoided ◯ fewer flushing intervals ◯ Minimized susceptibility to disruption in the process The invention is based on the following basic idea:

[0047] Two-component adhesives are applied using inkjet printing. Components A and B are applied in the same way as inkjet printing, with two colors overlapping or forming closely spaced droplets. Especially during joining, the components are effectively mixed and react chemically with each other. Application in any print pattern (from spot to almost full-surface) is possible. This concept is suitable for sheet stacks with solid cuts, segmented sheet cuts, or T-segments. However, other applications are not excluded.

[0048] The invention is also based on the finding that three sheet metal joining technologies for E-sheets are known in practice: In a first variant, insulation-coated sheets are punched and joined to form a sheet stack using punching and / or welding. In a second variant, full-surface bonding (baking varnish) takes place. Sheets pre-coated with baking varnish are punched and baked together under pressure and temperature to form a sheet stack. In a third variant, local bonding (liquid adhesive) takes place. Insulation-coated sheets are punched, individual adhesive dots (dotted glue) are applied to the punched sheets, and these sheets are joined to form a complete sheet stack by stacking them using pressure and temperature or using the no-mix process at room temperature.

[0049] The invention is based on the recognition of the following problems: In variant two, adjacent laminations are bonded together almost over their entire surface, resulting in advantages in terms of mechanical rigidity, bond strength, and media impermeability between the sheet metal laminations. Variant two has the disadvantage that the bonding takes place in a separate process step following the punching step. This is comparatively complex and expensive (process time, equipment investment, energy consumption). Variant three is usually integrated into the punching process and offers a joining technology that can be integrated into the part production cycle. Curing takes place at room temperature (contact polymerization using the no-mix process) or by brief heating in the punching tool. The activator or adhesive is usually applied by spraying or using a contact process (stamp-like). Advantages are: time savings, shorter cycle times, and cost savings.Disadvantages include: lower bond strength compared to full-surface bonding; separate tools required for each new print layout.

[0050] In practice, it is also known for a 2K (two-component) adhesive (curing at room temperature) to apply an activator to one flat side of a sheet metal strip using a spray coating process. The adhesive is then applied to the other flat side using a stamping process. Two separate steps are required. Punching and stacking, in turn, are carried out in a single step.

[0051] In practice, it is also known for a 2K high-temperature adhesive (increased permanent temperature resistance at 180 °C, even higher temperatures can be tolerated for short periods) or a 2K (two-component) adhesive (curing at room temperature) to apply an activator in a dot pattern via defined nozzles to one flat side of a sheet metal strip. The adhesive is then applied in a dot pattern via defined nozzles to the other flat side. This occurs in a simultaneous process (synchronous with the punching cycle). Punching and stacking, in turn, take place in a single step.

[0052] The invention is based on the idea of ​​improving variant three: By incorporating inkjet printing technology, the advantages of both variants two and three can be combined: • Full-surface (or at least large-scale) application of the liquid adhesive, • Almost any print layout - thus independent of the print layout can be implemented with one tool, the layout can be easily changed by (any) control of the individual nozzles / matrix nozzles - as with matrix printing, • extremely precise dosing technology (sharpness, application quantity), • high mechanical strength and rigidity in the laminated core (laminated core, similar to baked enamel technology), • variable mechanics of the adhesive joint (adhesive layer between two lamellae) through targeted adhesive selection or modification, since inkjet technology allows for variable adhesives, • Media tightness theoretically feasible, resulting in an interlaminar (i.e. tightness between adjacent lamellas) sealing function • Avoidance of local elevations of the sheet stack at specific bonding points • Integration in the punching process or offline possible, • Joining in the punching cycle (approx. 150 strokes per minute), as no baking step is necessary, cost savings and energy efficiency.

[0053] In addition, it's a contactless dispensing process that minimizes material carryover during the process. This also ensures that any punching waste is sorted and can be more easily recycled.

[0054] The following inkjet printhead arrangements are possible: The dimensions of individual printheads are usually defined by the printhead manufacturer. Adaptation for wider printing areas is achieved by using multiple printheads in a staggered arrangement, e.g., for full cuts, but also for segmented sheet metal cuts or T-segments. Due to limited installation space, a customized printhead with the appropriate width is preferred but essential. The arrangement can be implemented within one or more empty stages of the punching process. The adhesive can be dispensed onto the top or bottom of the sheet (overhead).

[0055] Further features, effects, and advantages of the invention will become apparent from the following description of a preferred embodiment of the invention and the accompanying figures. Each of these figures shows a schematic diagram: Fig. 1 a production facility for producing a sheet metal lamination package, Fig. 2 the basic application of the adhesive in the form of two components, Fig. 3 the principle of applying the components separately and one after the other, Fig. 4 the application of the components one after the other by separate printing modules, Fig. 5 the punching and printing of an exemplary rotor sheet in the production facility Fig. 1, Fig. 6 the corresponding production of a rotor sheet made of Fig. 5 matching stator sheets, Fig. 7 the production of a stator lamination according to Fig. 6 with two printing modules, Fig. 8 the production of a stator lamination according to Fig. 6 with translationally movable pressure module, Fig. 9 the production of a stator lamination according to Fig. 6 with rotatable printing module.

[0056] Fig. 1 shows a production facility 2. This facility is used to manufacture a laminated core stack 4 for an electrical machine (not shown), in this case a rotor core and a stator core for an electric motor. The production facility 2 includes a base frame 6 mounted in a production hall (not shown) and a punching tool 8, which is movable in the direction of the double arrow 10 to perform punching work in conjunction with the base frame 6.

[0057] The plate pack 4 is manufactured from a sheet metal 12, which is provided here as a (in the technical sense endless) belt 14 and is unrolled from a roll 16 and transported in a transport direction 18 (indicated by an arrow) through the production device 2.

[0058] The production device 2 contains four punching modules 20a-d, which successively produce a sheet metal lamella 22 (in Fig. 1 only indicated) from the sheet metal 12 or strip 14 and separated in the punching step SSd. In this process, the sheet metal laminations 22 are successively stacked on top of one another in a collecting container 24 by a stacking module 31 and glued together with adhesive 36, as explained further below.

[0059] The production device 2 contains two printing modules 28a,b, each with five print heads 30a-e (see Fig. 2-6) and a curing station 34, in which the stacked or glued lamination pack 4 is cured with respect to its adhesive 36 (in Fig. 1 only symbolically indicated). A transport module 38 of the production facility 2, not further designated, serves to transport the strip 14 or the individual sheet metal laminations 22 and the lamination pack 4 through the production facility 2.

[0060] In the production facility 2, the following process is now carried out to produce the disk pack 4 for the electrical machine:The sheet metal 12 is provided as strip material in the form of the strip 14 with the two flat sides 40a,b. A plurality of sheet metal lamellae 22, each having two flat sides 40a,b corresponding to the flat sides 40a,b of the strip 14, are manufactured by producing each of the sheet metal lamellae 22 from the sheet metal 12 in the four punching steps SSa-d - each in the punching modules 20a-d. In two printing steps DSa,b - each in the printing modules 28a,b - adhesive 36 is applied to the sheet metal 12 or the lamellae 22 using the print heads 30a-e. In the printing steps DSa,b in the printing modules 28a,b, the adhesive 36 is printed by means of five print heads 30a-e each. The application is carried out on the lower flat side 40b in the figure of each sheet metal lamella 22 to be bonded. The application is carried out by printing on a respective sheet metal lamella 22 using the print heads 30a-e in an inkjet process or in inkjet technology.In a stacking step AS, the laminations 22 separated from the strip 14 are stacked one on top of the other to form the lamination stack or lamination stack 4. This takes place in the collection container 24. Bonding is performed using the adhesive 36. This also involves pressing the individual laminations 22 together in the direction of the double arrow 10 (not explained in more detail).

[0061] The punching steps SSa-d, the printing steps DSa,b, and the stacking step AS are performed as a continuous inline process using the strip material or strip 14 as the starting material. The four punching steps SSa-d are performed sequentially in the four punching modules 20a-d. The printing steps DSa,b are performed between the punching steps SSc,d in the punching modules 20c,d. The adhesive 36 is printed onto the entire flat side 40a of the respective sheet metal lamination 22.

[0062] Fig. Figure 2 illustrates that the adhesive 36 here is a two-component (2K) adhesive comprising the two components 37a and 37b. An example shown is a sheet metal lamination 22, here in the form of a stator lamination, which has not yet been separated from the sheet metal 12 or strip 14, but is already coated with adhesive 36. Fig. 2 shows in section 50 an enlargement of the already applied adhesive 36. Its components 37a,b are arranged in a checkerboard pattern (in Fig. 2 tilted by 45° to the vertical) are printed alternately and offset in rows in an alternating dot pattern as component dots 52 on the flat side 40b of the slat 22. The component dots 52 are printed adjacent to one another, touching one another. The "checkerboard pattern" is shown only as an example for simplified illustration. Other dosing patterns are also considered (e.g., directly overlapping one another).

[0063] Fig. Figure 3 schematically illustrates the printing of the two components 37a,b onto the sheet metal lamella 22 in order to produce the printed lamella 22 from Fig. 2. In or after a punching step SSc, the sheet metal lamination 22 is not yet coated with adhesive 36. In other words, this sheet metal lamination 22 forms a substrate for the subsequent printing of the adhesive 36.

[0064] In a first printing step DSa (inkjet printing), the first component 37a of the adhesive 36 is applied using the printing module 28a. The print heads 30a-e in the printing module 28a therefore only dispense the component 37a or print it onto the sheet metal lamella 22. The component 37A is applied in the form of component dots 52 with “gaps” in between, as shown in detail 50 in Fig. 2 shown, plotted.

[0065] Only after the sheet metal lamination 22 has been transported further to a next station of the punching process in the transport direction 18 does the application (inkjet printing) of the second component 37b in the above-mentioned “gaps” take place in the printing step DSb, also in the form of other component points 52. The printing is carried out here with the aid of the printing module 28b, whose print heads 30a-e exclusively output or print the component 37B.

[0066] Fig. Finally, Figure 3 symbolically shows how a plurality of sheet metal laminations 22 coated with adhesive 36 are stacked one after the other to form the lamination stack 4 and pressed together. This joins the sheet metal laminations 22 to form the lamination stack immediately after the adhesive has been applied (printing steps DSa,b). The components 37a,b or component points 52 flow into one another, react with each other, and the adhesive 36 exerts its adhesive effect. The curing of the adhesive 36 also takes place at this time. Fig. Figure 3 thus shows the general representation of the process according to the invention, namely the printing of a 2K adhesive 36 using inkjet technology.

[0067] Fig. Figure 4 shows a process variant for the surface application of the 2-component adhesive 36 using inkjet technology, here integrated into the punching process. In the example, the sheet metal 12 is moving in the transport direction 18 (dynamic process step) while the adhesive 36 is being printed. In other words, this occurs during the cycle steps 42a-c indicated by arrows. The printing modules 28a,b are rigidly mounted on the base frame 6. The components 37a,b are printed in separate print head stations (printing modules 28a,b).

[0068] In the punching step SSc, the sheet metal lamination 22 is again without the applied adhesive 36. When the cycle step 42a is executed, the component 37a is applied to the sheet metal lamination 22 using the printing module 28a. Only in the subsequent cycle step 42b, which follows at a later time, is the second component 37b additionally applied to the sheet metal lamination 22. The adhesive components are now—at least partially—mixed. In the punching step SSd, the sheet metal lamination 22 is then separated, i.e., punched out of the remaining strip 14.

[0069] Fig. 5 shows the production of rotor laminations 22. Fig. 2 shows a plan view in the direction of arrow II from Fig. 1 to the production facility 2, omitting the basic frame 6. The punching steps SSc,d in the punching modules 20c,d are shown. In a modification of Fig. 1, however, there is only a single printing module 28a with the print heads 30a-e. The printing module 28a rests on the base frame 6. The printing of the adhesive 36 onto the flat side 40b takes place in a respective clock step 42a-c, each of which corresponds to a further transport of the strip 14 by one unit of length LG. Both components 37a,b are applied simultaneously with the help of the printing module 28a. In this case, either the respective print head 30a-e can output both components 37a,b. Alternatively, the print heads 30a,b,c output component 37a, and the print heads 30d,e output component 37b. The punching steps SSa-d in the punching module 20a-d, on the other hand, take place when the strip 14 is at a standstill between two clock steps 42a-c. Such a standstill lasts, for example, 0.2 seconds in a continuous process. This is how much time remains for printing.

[0070] Fig. 6 shows the production of stator laminations 22 (larger than the rotor). In order to achieve optimal coverage of the strip 14 over the entire width (also sufficient for the rotor lamination) and to be able to print the entire strip area / width with adhesive 36, a total of five print heads 30a-e are arranged in two rows offset from one another in the print module 28a (print module 28b is identical in this respect, see below). Fig. 2 and Fig. 3 Therefore, not only a rotor but also a stator lamination 22 can be fully coated with adhesive 36 using the same pressure module 28a.

[0071] The Fig. 2 and Fig. 3 therefore show a sequence of application steps in the punching sequence. A first case is shown here: the application takes place in the feed step (cycle step 42a) of the punching process (sheet metal 12 in motion). The sheet metal 12 is therefore in motion (dynamic process step), and the print heads 30a-e / the print module 28a are rigidly mounted on the base frame 6. Area 48 therefore shows an inkjet printing station in an idle stage of the punching process (application stage). The punching module 20d forms an "outer contour punching stage" (adhesive 36 is dispensed).

[0072] The stator surface (stator lamination 22) may need to be printed with adhesive 36 in two steps: Fig. 7 shows in accordance with Fig. 1 therefore again both printing modules 28a,b, which are arranged spaced apart from one another in the transport direction 18 of the belt 14 or the sheet metal lamellas 22. In a first cycle step 42a, the printing module 28a coats a first half of the sheet metal lamella 22 with adhesive 36, while the second half remains adhesive-free. Only in cycle step 42b is the remaining second half of the sheet metal lamella 22 coated with adhesive 36. The two halves are indicated again by dashed lines, whereby in this case a gapless, seamless application of adhesive 36 actually takes place. Here, too, the components 37a,b are printed simultaneously by each of the printing modules 28a,b.

[0073] Fig. 7 therefore shows a process variant for better surface coverage of the sheet metal cut during adhesive dosing (especially at the stator).

[0074] Fig. Figure 8 shows an exemplary sequence of application steps in the punching sequence, here a second case: dosing in the punching step of the punching process.

[0075] Fig. 8 shows an alternative printing module 28a in the production device 2, which is not arranged stationary on the base frame 6 like the printing modules 28a,b of the Fig. 2 to 4. Here, the printing module 28a is translationally displaceable in a direction of movement 44 (indicated by double arrows) relative to the base frame 6. Here, too, the printing of the components 37a,b is carried out simultaneously by the printing module 28a,b. The direction of movement 44 runs parallel to the flat sides 40a,b and perpendicular to the transport direction 18. Furthermore, in contrast to the Fig. 2 to 4 not during the cycle steps 42a-c, but in cycle pauses between respective cycle steps 42a-c, i.e., when the strip 14 is at rest relative to the base frame 6. Printing is performed by moving the printing module 28a in each direction of the double arrow of the movement direction 44. After the next cycle step 42a-c, the printing module 28a is moved back in the opposite direction and prints the next sheet metal lamination 22 with adhesive 36. Fig. 8 therefore shows, for example, the starting position of the print heads 30a-e (print module 28a) before dispensing at the top of the image, and the final position of the print heads 30a-e after dispensing at the bottom. Here, too, the adhesive application takes place in an idle stage (no punching activity here) of the punching process.

[0076] According to Fig. 8, the sheet metal 12 is stationary (static process step), and the print heads 30a-e are in motion. Their alternating movement occurs transversely to the transport direction 18, also known as the "punching direction." A similar process is used for the rotor.

[0077] Fig. Figure 9 shows an exemplary sequence of application steps in the punching sequence, here a case 3: Dosing in the punching step of the punching process.

[0078] Fig. Figure 9 thus shows a further alternative embodiment of a printing module 28a for applying both components 37a,b. Here, it is also movably mounted with respect to the base frame 6, but here it rotates about a rotation axis 46 for printing, as in Fig. 9 is indicated by arrows. Here, too, the printing of the sheet metal lamella 22 with adhesive 36 takes place between two cycle steps 42a-c, i.e., with the strip 14 or sheet metal lamella 22 at rest relative to the base frame 6.

[0079] Here, too, the sheet metal 12 remains stationary (static process step). The print heads 30a-e are in motion. The print head assembly / print module 28a rotates. Here, too, an analogous process is used for the rotor. Reference symbol 2 manufacturing facility 4 slat pack 6 Basic framework 8 punching tool 10 double arrow 12 sheets 14 volumes 16 rolls 18 Transport direction 20a-d punching module 22 sheet metal slats 24 collection containers 28a,b pressure module 30a-e printhead 31 Stacking module 34 Curing station 36 Adhesive 37a,b component 38 Transport module 40a,b flat side 42a-c bar step 44 Direction of movement 46 axis of rotation 48 Area 50 Details 52 Component Point LE unit of length SSa-d punching step DSa,b pressure step AS stacking step QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2019 / 086634 A1

[0002] Cited non-patent literature

[0000] https: / / de.wikipedia.org / wiki /

[0011] https: / / www.xaar.com / en / products / xaar-printheads

[0017] Laser-Induced Forward Transfer: A Method for Printing Functional Inks“, by J. Marcos Fernandez-Pradas and Pere Serra, Crystals 2020, 10(8), 651; Published: 29 July 2020, Download am 25.04.2023 von https: / / www.mdpi.com / 2073-4352 / 10 / 8 / 651

[0018]

Claims

[1] Method for producing a laminated core (4) for an electrical machine, in which: - at least two sheet metal lamellae (22) each having two flat sides (40a,b) are produced by manufacturing each of the sheet metal lamellae (22) from a sheet metal (12) in at least one punching step (SSa-d), - in at least one printing step (DSa,b) an adhesive (36) is printed onto at least one flat side (40a,b) of each sheet metal lamella (22) to be bonded, - wherein the adhesive (36) is applied to the respective sheet metal lamella (22) by printing on the respective sheet metal lamella (22) with the aid of at least one print head (30a-e) in an inkjet process (over the entire surface, partially or selectively), - wherein the adhesive (36) comprises at least two mutually reactive components (37a,b), and each of the components (37a,b) is dispensed individually from one of the print heads (30a,b) without premixing the components (37a,b) in or before the print heads (30a,b), - in a stacking step (SA) following the punching steps (SSa-d) and the printing steps (DSa,b), the sheet metal laminations (22) are stacked on top of one another to form the lamination pack (4) and are glued to one another by means of the adhesive (36). [2] Method according to claim 1, characterized by that a no-mix adhesive is dispensed as one of the components (37a,b) and an associated activator is dispensed as another of the components (37a,b). [3] Method according to one of the preceding claims, characterized by that a mixing ratio of at least two of the components (37a,b) is adjusted by dosing the output from the print heads (30a,b). [4] Method according to one of the preceding claims, characterized by that at least two of the components (37a,b) are printed as component dots (52) on the flat sides (40a,b) in the manner of an alternating dot pattern. [5] Method according to one of the preceding claims, characterized by that the sheet (12) is provided as a strip (14) with the two flat sides (40a,b). [6] Method according to claim 5, characterized by that the punching steps (SSa-d), the printing steps (DSa,b) and the stacking step (SA) are carried out as a continuous inline process on the strip (14) as starting material. [7] Method according to one of the preceding claims, characterized by that at least two punching steps (SSa-d) are carried out successively and at least one of the printing steps (DSa,b) is carried out between two of the punching steps (SSa-d). [8] Method according to one of the preceding claims, characterized bythat the adhesive (36) is printed onto the entire respective flat side (40a,b) of at least one of the sheet metal lamellas (22). [9] Method according to one of the preceding claims, characterized by that the adhesive (36) is printed onto at least one of the sheet metal lamellae (22) in at least two successive printing steps (DSa,b). [10] Method according to one of the preceding claims, characterized by that the two components (37a,b) are output from different print heads (30a,b) or print modules (28a,b). [11] Method according to one of the preceding claims, characterized by , that - the method is carried out with the aid of or in a production facility (2) with a stationary base frame (6), and - at least one of the print heads (30a-e) rests relative to the base frame (6) during at least one of the printing steps (DSa-b). [12] Method according to one of the preceding claims, characterized by , that - the method is carried out with the aid of or in a production facility (2) with a stationary base frame (6), and - at least one of the print heads (30a-e) moves relative to the base frame (6) during at least one of the printing steps (DSa-b). [13] Method according to claim 12, characterized by that at least one of the print heads (30a-e) moves by moving relative to the base frame (6) in a direction of movement (44) that is not parallel to a transport direction (18) of the sheet metal lamella (22). [14] Method according to one of claims 12 to 13, characterized by that at least one of the print heads (30a-e) moves by rotating relative to the base frame (6) about an axis of rotation (46). [15] Manufacturing device (2) for producing a laminated core (4) for an electrical machine according to a method according to one of the preceding claims, - with at least one punching module (20a-d) which is designed to carry out the punching steps (SSa-d), - with at least one printing module (28a,b), wherein each of the printing modules (28a,b) contains at least one of the print heads (30a,b), wherein the printing modules (28a,b) are adapted to carry out the printing steps (DSa,b), - with a stacking module (31) which is designed to carry out the stacking step (AS).

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