Method for packaging sheet metal parts from an electrical steel strip or sheet to form a laminated core

Abstract

The invention relates to a method for packaging sheet metal parts (4) from an electrical steel strip (3) or sheet to form a laminated core (2). In order to achieve advantageous process conditions, it is proposed that when hot melt adhesive lacquer layers (7) are put under pressure (P) in the axial direction (A) of the stacked sheet metal parts (4), said lacquer layers are put under pressure (P) multiple times by a pressure pulse (10), by applying a pulse pressure (P10) or releasing a pulse pressure (P10), in order to exert the pressure pulse (10).

Description

[0001] Method for bundling sheet metal parts from an electrical strip or sheet into a sheet package

[0002] The invention relates to a method for bundling sheet metal parts made from an electrical strip or sheet to form a sheet stack, in which the sheet metal parts, which have a hot-melt adhesive lacquer layer, in particular a baking lacquer layer, on at least one of their flat sides, are stacked on top of one another, the hot-melt adhesive lacquer layers of the stacked sheet metal parts are heated and, at a first temperature which is greater than the glass transition temperature of the hot-melt adhesive lacquer of the hot-melt adhesive lacquer layers and less than the baking temperature of the hot-melt adhesive lacquer of the hot-melt adhesive lacquer layers, are put under pressure in the axial direction of the stacked sheet metal parts, and subsequently the hot-melt adhesive lacquer layers of the sheet metal parts are heated to a second temperature which is greater than or equal to the baking temperature of the hot-melt adhesive lacquer, and the sheet metal parts are thus baked together.

[0003] When manufacturing laminated cores from sheet metal parts coated with a hot-melt adhesive layer, it is known (WO2021175875A1) to subject the laminated core, and thus the hot-melt adhesive layer, to axial pressure when bonding the sheet metal parts to ensure a desired core height. In addition to a precise core height, full-surface bonding between the sheet metal parts is also necessary – especially if the laminated core is required to be pressure-resistant during liquid cooling – which is particularly the case for laminated cores in the high-performance range, for example, in electric motors.

[0004] Description of the Invention The object of the invention is therefore to further develop a method for producing a laminated core of the type described above in such a way that a laminated core resistant to liquid cooling can be produced with increased reproducibility. Furthermore, the method should be easy to handle and require no additional effort.

[0005] The invention solves the problem by the features of claim 1.

[0006] If the hot melt adhesive layers are subjected to pressure several times in the axial direction of the stacked sheet metal parts by a pressure pulse, their interface properties can be prepared for full-surface bonding. This is true even if temperature differences exist across the hot melt adhesive layer. Furthermore, it is conceivable that the pressure pulse itself could overcome differences in the flow properties of the hot melt adhesive layers – which could further promote full-surface bonding between the sheet metal parts by forming a more homogeneous boundary layer. For example, the pressure pulse can be applied by applying pulsed pressure or releasing the pressure.

[0007] The process thus enables the reproducible creation of a fluid-tight connection between the sheet metal parts, which surprisingly withstands even particularly high hydraulic pressures. Furthermore, the pressure changes on the sheet stack in the form of pressure pulses require no additional or complex handling steps, which makes the process simple to implement – ​​and, compared to other processes that require pressurizing the sheet stack during the bonding process, does not require any additional effort.

[0008] The handling of the method can be simplified, among other things, if the pressure pulse is applied by applying pulse pressure and then at least partially releasing the pulse pressure, in particular by substantially releasing the entire pulse pressure. Preferably, the pulse pressure is completely released. The method can be further improved if the hot melt adhesive layers are essentially free of pressure during the subsequent release of the pulse pressure.

[0009] This pulsed pressure step is preferably kept comparatively short in time, with the duration of the pulsed pressure application and / or the subsequent release of the pulsed pressure being in the range of 0.1 to 20 seconds. This is particularly true if this duration is in the range of 0.5 to 5 seconds. In this way, for example, the risk of hot melt adhesive squeezing out of the bonding gap between the sheet metal parts can be minimized. The duration of the pulsed pressure application is preferably equal to the duration of the subsequent release of the pressure.

[0010] For example, the pressure pulse applies pressure to the hot melt adhesive layers in the range of 0.5 to 10 N / mm 2 (Newton per square millimeter). Preferably, the pressure pulse applies pulse pressure in the range of 2 to 6 N / mm to the hot melt adhesive layers 2in order to minimize the risk of hot melt adhesive squeezing out of the adhesive gap between the sheet metal parts.

[0011] Simple process conditions can be achieved if the first temperature is in the range of 80 to 220 °C. Preferably, the first temperature is in the range of 80 to less than 180 °C. If the first temperature is in the range of 100 to 150 °C, the risk of hot melt adhesive squeezing out of the bonding gap between the sheet metal parts can be minimized.

[0012] If the pressure pulse is applied several times in direct succession, the homogenization of the interfacial properties can be further improved. This is even more so if the pressure pulse is applied several times in a periodic manner. It may also prove advantageous if the hot melt adhesive layers are subjected to pressure pulses several times in a first time period of a pressure curve and to constant pressure in at least one other time period of the pressure curve. The other time period is preferably two to four times longer than the first time period.

[0013] Preferably, the length of the other time period is in the range from 0.5 to 180, in particular from 60 to 120, seconds.

[0014] For example, the length of another second time period may be in the range of 0.5 to 120 seconds, in particular 60 seconds.

[0015] For example, the length of another third time period can be in the range of 30 to 180 seconds, in particular 120 seconds. Preferably, the second time period occurs before the third time period. For example, the first time period can occur between the other second and the other third time period.

[0016] It is conceivable that the hot melt adhesive layers are subjected to pressure several times by the pressure pulse in such a way that a full-surface bond is achieved while avoiding any squeezing of adhesive from the adhesive joints between the sheet metal parts.

[0017] Simple process conditions can be achieved if the second temperature is in the range of 180 °C to 250 °C, in particular from 180 °C to 220 °C.

[0018] Preferably, sheet metal parts are stacked on top of each other, each with a hot-melt adhesive layer, especially a self-bonding layer, on both flat sides. This can, for example, further increase the resistance of the sheet stack to liquid cooling, as the bond is reduced to a single interface between two similar joining partners. Furthermore, the pressure pulse can influence the two viscous hot-melt adhesive layers simultaneously, which can further improve the bond between them and thus the sheet metal parts.

[0019] Preferably, the thickness of each sheet metal part is between 0.09 and 0.49 mm, in particular 0.09 to 0.29 mm, and / or the thickness of the hot-melt adhesive layer of each sheet metal part is between 2 and 12 μm, in particular 4 to 8 μm. This provides particularly advantageous conditions for high reproducibility of the process.

[0020] In the process, it is conceivable, for example, that the pressurization takes place on a preferably pre-bonded sheet stack. This is done by stacking the sheet metal parts in a stacking device. After leaving the stacking device in the form of a, particularly pre-bonded, sheet stack, their hot-melt adhesive layers are repeatedly pressurized by the pressure pulse in a pressure device and subsequently subjected to final heating.

[0021] Alternatively, it is conceivable that the following process steps are carried out in a printing device, avoiding the use of a pre-bonded sheet stack: stacking individual sheet metal parts to form a sheet stack, heating their hot-melt adhesive layers, applying pressure several times using the pressure pulse and, if necessary, subsequent final heating.

[0022] Preferably, the height of the laminated core is recorded several times using a measuring method, at least in a time interval resulting from the package height between two successive pressure pulses. This provides data with which the method can be controlled. For example, by calculating a difference value from each of two successive recorded package heights. If a calculated difference value falls below a predetermined minimum, in particular for the first time, the pressurization of the laminated core by the pressure pulses is terminated. The method can thus become more reliable. A predetermined minimum can, for example, approach zero or represent an absolute minimum calculated from the calculated difference values.

[0023] For example, the measurement method also records the stack height (hp) before the first pressure pulse of the pressure pulses, thus creating a maximum value as the first differential value (Ahp). This allows, for example, the behavior of the laminated core during subsequent pressure pulses to be more accurately predicted.

[0024] Preferably, the specified minimum is 10%, 5%, or 2% of the first calculated difference value (Ahp). For example, 10% may be advantageous for a sequence of comparatively small difference values ​​(Ahp), whereas 5% or 2% may be more advantageous for a sequence of comparatively large difference values ​​(Ahp).

[0025] Short description of the drawings

[0026] The figures show, for example, the subject matter of the invention in more detail using an embodiment variant.

[0027] Fig. 1 is a schematic representation of an apparatus for carrying out the method according to the invention,

[0028] Fig. 2 shows a pressure curve with which a pre-bonded laminated core from Fig. 1 is subjected to pressure in its axial direction,

[0029] Fig.3a is a sectional view of an adhesive gap between two sheet metal parts of the laminated core according to Fig. 2 which has not yet been subjected to impulse pressure,

[0030] Fig.3b a sectional view of an adhesive gap between two sheet metal parts after setting the hot melt adhesive layers under impulse pressure according to Fig. 2 and

[0031] Fig. 4 shows an alternative device for carrying out the method according to the invention.

[0032] Way of carrying out the invention According to Figures 1 and 4, devices 1, 100 are shown with which a laminated core 2 is produced, which is preferably used for electromagnetic components, for example for electrical machines.

[0033] For this purpose, a first device 1 (see Fig. 1) separates several sheet metal parts 4 from an electrical steel strip 3. The electrical steel strip 3 is coated on both flat sides 3a, 3b with a thermosetting hot-melt adhesive layer 7, for example, comprising an epoxy resin base and dicyandiamide as a crosslinking agent. The thermosetting or heat-curing hot-melt adhesive layers 7 can consist of a self-bonding varnish. For example, a catalyzed self-bonding varnish can also be used, such as a self-bonding varnish with a depot coating for faster curing.

[0034] The hot-melt adhesive 7a or the hot-melt adhesive layer 7 is in the B-stage, with the glass transition temperature Tg of the hot-melt adhesive 7a used, for example, being in the range of 65 to 85 °C (degrees Celsius), measured according to ISO 11357-2. The bonding temperature of the hot-melt adhesive 7a used, for example, is in the range of greater than or equal to 180 degrees. However, these characteristics for the glass transition temperature and bonding temperature can vary depending on the hot-melt adhesive 7a used.

[0035] The sheet metal parts 4 are separated using a punching tool 5, which can also be part of a subsequent punching tool (not shown). Other devices for separating sheet metal parts 4, for example, using a laser, are conceivable. Preferably, the thickness of each sheet metal part 4 is between 0.09 and 0.49 mm (millimeters), namely 0.24 mm, and the thickness of each hot-melt adhesive layer 7 is between 2 and 12 pm (micrometers), namely 5 pm. This also applies to the electrical steel strip 3 from which the sheet metal part 4 originates. This results in a thickness for each individual lamination on the laminated core 2 in the range of 0.1 to 0.5 mm.

[0036] The sheet metal parts 4 are pushed by the punch 5a of the punching tool 5 into a stacking device 6. In this stacking device 6, the sheet metal parts 4, which have a hot-melt adhesive layer 7, namely a self-bonding layer, on at least one of their flat sides 4a, are stacked one on top of the other. In the exemplary embodiment—as can also be seen in Fig. 3a—the sheet metal parts 4 have this hot-melt adhesive layer 7 on both of their flat sides 4a, 4b.

[0037] The stacking device 6 heats the hot-melt adhesive layer 7 to a temperature tv that is above the glass transition temperature Tg of the hot-melt adhesive layer 7a, namely to a temperature tv of 100 °C (100 degrees Celsius). In addition, the hot-melt adhesive layers 7 are subjected to a pressure of 3 N / mm 2 (Newtons per square millimeter) for 30 seconds. This pre-bonds the sheet metal parts 4 to form a sheet metal package 2.

[0038] All stacked sheet metal parts 4 leave the stacking device 6 as pre-glued sheet metal packages 2 or are separated into pre-glued sheet metal packages 2 during or after leaving the stacking device 6 - which is not shown.

[0039] These pre-bonded sheet stacks 2 are then subjected to further process steps - namely, the sheet stack 2 is introduced into a first oven 8 in order to preheat the hot-melt adhesive layers 7 of the stacked sheet metal parts 4 to a first temperature tempi, which is above a glass transition temperature Tg of their hot-melt adhesive 7a and below the caking temperature of their hot-melt adhesive 7a.

[0040] However, it is conceivable, which has not been shown in more detail, that the sheet metal parts 2 are brought to this first temperature in the stacking device 6 before leaving it - which makes the process step with the first furnace 8 obsolete.

[0041] In a further step, after the laminated core 2 has left the stacking device 6, it is introduced into a pressure device 9, which, using a press ram 9a, exerts an axial compressive force P on this laminated core 2—that is, in the axial direction A of the laminated core 2, which direction A runs parallel to the stacking direction of the stacked sheet metal parts 4. Two of these stacked sheet metal parts 4 can be seen in Fig. 3a.

[0042] This is done in a special way - see pressure P or compressive force P(t) in Fig. 1 in conjunction with Fig. 2. Thus, it can be seen in Fig. 2 that the pre-bonded laminated core 2 is individually pressurized in its axial direction A several times, five times in the exemplary embodiment, by a pressure pulse 10, by applying pulse pressure P10 and subsequently relieving pressure P. This results in a periodic pulse sequence.

[0043] According to the embodiment 2, the relief corresponds to the applied pulse pressure Pw, whereby it is conceivable that a residue of the pulse pressure P10 remains.

[0044] As can be seen in the pressure curve P(t) according to Fig.2, the hot melt adhesive layers 7 are essentially free of pressure P due to the subsequent relief.

[0045] The illustrated pressure pulse 10 essentially follows a rectangular shape, as can be seen ideally in Fig. 2, for example. Preferably, the pressure pulse 10 has a unipolar pulse shape.

[0046] This pulse pressure P10 reliably compensates for unevenness. This is the case even if, due to temperature differences on the respective sheet metal part 4, the hot melt adhesive has inhomogeneous flow properties across the entire bonding surface. According to the invention, the pressure pulse 10 can overcome these inhomogeneities and thus produce sheet metal packages 2 that are particularly reproducibly resistant to liquid cooling. This pulse pressure P is particularly effective in bonding the hot melt adhesive 7a of the hot melt adhesive layer 7 on a flat side 4a of the sheet metal part 4 to a hot melt adhesive 7a of the hot melt adhesive layer 7 on the flat side 4b of another sheet metal part 4 adjoining it, as shown in Figures 3a and 3b.

[0047] But this can also improve the bonding of the hot melt adhesive 7a of the hot melt adhesive layer 7 to a bare sheet metal part 4, although this has not been shown in more detail. As further shown in Fig. 2, the pre-bonded laminated core is subjected in its axial direction A to five pulse pressures, each of which is of the same level in the exemplary embodiment, by the pressure pulse 10 with a unipolar pulse shape in a first time period 11a of a pressure curve P(t), which pulse occurs periodically with a period duration T. Preferably, when the pressure is relieved by the pulse pressure P, the laminated core 2 is pressure-free - but it is also conceivable for the pressure pulse 10 to be superimposed with a constant compressive force, so that even when the pressure is relieved by the pulse pressure P10, a pressure P still acts on the hot melt adhesive layers 7, although this has not been shown in more detail.

[0048] To generate the pressure pulse 10, the press 9 loads the sheet stack 2 with a pressure P at the level P10 or with the pulse pressure P10 in the range of 0.5 to 20 N / mm 2 , namely 5 N / mm 2 . This application of pressure P and release from this pressure P takes place with an equal duration ti and t2 respectively, which results in a period T in the range from 0.1 to 20 seconds, namely 2 seconds.

[0049] In this process step, the hot melt adhesive has a first temperature tempi in the range of 80 to 220 °C, namely 120 °C.

[0050] Due to minimum control or regulation requirements, a comparatively minimal pressure P of 0.1 N / mm 2 which has not been shown in more detail, which can, for example, represent essentially total relief with pulse pressure P10.

[0051] The pulse pressure P10 may be sufficient to achieve complete bonding of the two hot-melt adhesive layers 7 to one another, thus eliminating the free areas 16 between the hot-melt adhesive layers 7, as can be seen in Fig. 3a. This also significantly improves the bonding of the sheet metal parts 4 to one another, which in turn further increases the stability of the sheet metal stacks 2 produced by the method according to the invention.

[0052] In an optional second time period 11 b of the pressure curve P(t), the laminated core 2 is pressurized with a constant pressure 12b, namely at the level Pi2b in the range of 2 to 10 N / mm 2 , namely 2 N / mm 2 for 60 seconds. The second time period 11 b occurs chronologically before the first time period 11 a.

[0053] In an optional third time period 11 c of the pressure curve P(t), the laminated core 2 is subjected to a constant pressure 12 c, namely at the level Pi2c in the range of 0.5 to 10 N / mm 2 , namely 1 N / mm 2 for 120 seconds. The third time period 11c occurs chronologically after the first time period 11a.

[0054] Also, as can be seen in Fig. 1, the laminated core 2 or its hot-melt adhesive layer ? is maintained at the first temperature tempi during pressing. The three aforementioned time periods 11 b, 11 a, 11 c are also carried out by the pressure device 9.

[0055] Subsequently, the sheet metal parts 4 are baked to form a sheet stack 2, or the hot-melt adhesive 7a is converted to the C-state. For this purpose, the sheet stack 2 is introduced into a second furnace 13, and there the hot-melt adhesive layers 7 of the sheet stack 2 are heated to a second temperature temp2, which is greater than or equal to the baking temperature of the hot-melt adhesive 7a of the hot-melt adhesive layers 7, in order to bake the sheet metal parts 4 together under constant pressure in the axial direction A of the stacked sheet metal parts, exerted by a furnace die 13a, with a sufficiently long baking time. For example, the second temperature temp2 is 200 °C (200 degrees Celsius), the baking time is 1 minute with a compressive load on the sheet stack of 0.3 N / mm 2 .

[0056] The method according to the invention is therefore extremely flexible and produces pressure-resistant sheet stacks 2 with high reproducibility - this while avoiding any squeezing of adhesive from a respective adhesive joint 14 between the sheet metal parts 4. As a result, the formation of a drop 15 - shown as a dashed line in Fig. 3b - outside the adhesive joint 14 is also not to be expected.

[0057] Such a squeeze-out of adhesive is to be expected, for example, if the sheet package 2 according to the state of the art is heated to a temperature of 200 degrees Celsius immediately after stacking the sheet metal parts 4, with a baking time of 1 minute and under a pressure load of 3 N / mm 2 is baked in order to ensure such pressure resistance.

[0058] The risk of adhesive squeezing out of a respective adhesive joint 14 between the sheet metal parts 4 is further reduced by regulating the number of pressure pulses.

[0059] This can be achieved by repeatedly measuring the stack height hp of the laminated core 2 using a measuring method, namely before the first pressure pulse 10 and in each time interval between two consecutive pressure pulses 10 resulting in the stack height (hp). A difference value Ahp is calculated from each of the two consecutively measured stack heights hp.

[0060] This allows the effectiveness of the pressure pulses 10 to be estimated. This is done by terminating the pressurization P of the laminated core 2 by the pressure pulses 10 when a calculated differential value Ahp falls below a predetermined minimum for the first time. The process thus stops in time before adhesive is squeezed out of a respective adhesive joint 14.

[0061] Depending on requirements, this predefined minimum can be set to 10%, 5%, or 2% of the first calculated differential value Ahp. Since the package height hp is recorded before the first pressure pulse 10, the first calculated differential value Ahp also represents the first value in the sequence of differential values ​​Ahp, which significantly improves the control.

[0062] An alternative device 100 is shown in Fig. 4. Here, all process steps for producing a laminated core 2 from sheet metal parts 4 take place in a printing device 9.

[0063] First, individual sheet metal parts 4 are stacked to form a sheet metal stack 2. The sheet metal parts can, for example, originate from a punching device (not shown in detail). Then, the hot-melt adhesive layers 7 are heated to the first temperature tempi and subjected to pressure P using the press ram 9a and a counterholder 9b. The repeated application of pressure (P) by a pressure pulse (10) is carried out as described for Fig. 2.

[0064] Subsequently, the hot-melt adhesive layers 7 are baked and thus converted into state C by heating the hot-melt adhesive layers 7 to a temperature temp2. ​​Here, too, the parameters are set in the same way as described for the second oven 13 in Fig. 1.

[0065] In general, it is noted that "in particular" can be translated into English as "more particularly." A feature preceded by "in particular" is to be considered an optional feature that can be omitted and thus does not constitute a limitation, for example, of the claims. The same applies to "vorzugsweise," translated into English as "preferably."

Claims

P a t e n t a n s p r ü c h e: 1 . Method for bundling sheet metal parts (4) from an electrical strip (3) or sheet to form a sheet stack (2), in which the sheet metal parts (4), which have a hot-melt adhesive lacquer layer (7), in particular a baking lacquer layer, on at least one of their flat sides (4a, 4b), are stacked on top of one another, the hot-melt adhesive lacquer layers (7) of the stacked sheet metal parts (4) are heated and, at a first temperature (tempi ), which first temperature (tempi ) is greater than the glass transition temperature (Tg) of the hot-melt adhesive lacquer (7a) of the hot-melt adhesive lacquer layers (7) and less than the caking temperature of the hot-melt adhesive lacquer (7a) of the hot-melt adhesive lacquer layers (7), are placed under pressure (P) in the axial direction (A) of the stacked sheet metal parts (4), and subsequently the hot-melt adhesive lacquer layers (7) of the sheet metal parts (4) are heated to a second temperature (temp2) which is greater than or equal to the caking temperature of the hot-melt adhesive lacquer (7a),heated and thus the sheet metal parts (4) are baked together, characterized in that when the hot melt adhesive layers (7) are placed under pressure (P) in the axial direction (A) of the stacked sheet metal parts (4), these are placed under pressure (P) several times by a pressure pulse (10) in that an application of pulse pressure (P10) or a relief of pulse pressure (P10) takes place to exert the pressure pulse (10).

2. Method according to claim 1, characterized in that in order to exert the pressure pulse (10), an application of pulse pressure (P10) is carried out and subsequently an at least partial relief from the pulse pressure (P10), in particular from substantially the entire pulse pressure (P10).

3. Method according to claim 2, characterized in that during the subsequent relief from the impulse pressure (P10) the hot melt adhesive layers (7) are substantially free from the pressure (P).

4. Method according to one of claims 1 to 3, characterized in that the duration of the application of pulse pressure (P10) and / or the subsequent relief from the pulse pressure (P10) is in the range from 0.1 to 20, in particular from 0.5 to 5, seconds.

5. Method according to one of claims 1 to 4, characterized in that the pressure pulse (10) presses the hot-melt adhesive layers (7) with pulse pressure (P10) in the range of 0.5 to 10 N / mm 2 , especially from 2 to 6 N / mm 2 , applied.

6. The method according to any one of claims 1 to 5, characterized in that the first temperature (tempi ) is in the range from 80 to 220 °C, preferably 80 to less than 180 °C, in particular from 100 to 150 °C.

7. Method according to one of claims 1 to 6, characterized in that the setting under pressure (P) by the pressure pulse (10) takes place several times directly one after the other and / or periodically.

8. Method according to one of claims 1 to 7, characterized in that the hot-melt adhesive lacquer layers (7) are subjected to pressure (P) several times by the pressure pulse (10) in a first time period (11 a) of a pressure curve P(t) and by a constant pressure (12b, 12c) in at least one other time period (11 b, 11 c) of the pressure curve P(t).

9. Method according to claim 8, characterized in that the length of the other time period (11 b, 11 c) is in the range from 0.5 to 180, in particular from 60 to 120, seconds.

10. Method according to one of claims 1 to 9, characterized in that the hot-melt adhesive lacquer layers (7) are subjected to pressure (P) several times by the pressure pulse (10) in such a way that a full-surface bonding takes place while avoiding any squeezing of adhesive from the bonding joints (14) between the sheet metal parts (4).

11. The method according to any one of claims 1 to 10, characterized in that the second temperature (temp2) is in the range from 180 °C to 250 °C, in particular from 180 °C to 220 °C.

12. Method according to one of claims 1 to 11, characterized in that sheet metal parts (4) are stacked on top of one another, which have the hot-melt adhesive lacquer layer (7), in particular a baking lacquer layer, on both of their flat sides (4a, 4b).

13. Method according to one of claims 1 to 12, characterized in that the thickness of each sheet metal part (4) is between 0.09 and 0.49 mm, in particular 0.09 to 0.29 mm, and / or that the thickness of the hot-melt adhesive layer (7) of each sheet metal part (4) is between 2 and 12 pm, in particular 4 to 8 pm.

14. Method according to one of claims 1 to 13, characterized in that the sheet metal parts (4) are stacked in a stacking device (6), after leaving the stacking device (6) in the form of a, in particular pre-bonded, sheet metal package (2), the hot-melt adhesive lacquer layers (7) of which are placed under pressure (P) several times in a pressure device (9) by the pressure pulse (10) and are subsequently heated.

15. Method according to one of claims 1 to 13, characterized in that the following process steps take place in a printing device (9): individual sheet metal parts (4) are stacked to form a sheet metal package (2), the hot-melt adhesive layers (7) of which are heated, be subjected to pressure (P) several times by the pressure pulse (10) and, if necessary, subsequently heated.

16. Method according to one of claims 1 to 15, characterized in that the package height (hp) of the laminated core (2) is recorded several times using a measuring method, at least in a time interval which results in the package height (hp) between two successive pressure pulses (10), a difference value (Ahp) is calculated from each of two successive package heights (hp), and in the event that a calculated difference value (Ahp) falls below a predetermined minimum, in particular for the first time, the pressure (P) setting of the laminated core (2) by the pressure pulses (10) is ended.

17. The method according to claim 16, characterized in that the package height (hp) is also detected with the aid of the measuring method before the first pressure pulse (10) of the pressure pulses (10).

18. Method according to claim 16 or 17, characterized in that the predetermined minimum is 10%, 5% or 2% of the first calculated difference value (Ahp).

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