Method of forming a stack of plates from a stack of plate pieces made of electrical steel strip or sheet material

Abstract

The invention presents a method for stacking sheet pieces (4) made of electrical steel strip (3) or electrical sheet material into a sheet stack (2), the sheet stack having a stack height (hp) within a tolerance range (Δh) with respect to a predetermined target stack height (hs), respectively.

Description

Technical Field

[0001] The present invention relates to a method for stacking plates made of electrical steel strips or electrical sheet materials into a plate stack, wherein the plates have a hot melt adhesive paint layer, particularly a baked paint layer, on at least one of their flat sides, and the plate stacks have a stack height hp within a tolerance range Δh relative to a predetermined target stack height hs. Background Technology

[0002] In the production of stacks of boards coated with hot melt adhesive from electrical steel strips or electrical sheets, the stack height is typically checked after baking. This involves heating the stacks above the baking temperature of the hot melt adhesive coating for a sufficient duration. Stacks with unsuitable heights are then rejected. Alternatively, the height can be determined after stacking but before baking, allowing for the rejection of stacks with insufficient height or adjustment of the height before baking to reduce scrap. However, this method has the drawback of not being able to reliably predict the stack height after baking. This is due to numerous influencing factors. On one hand, the height of each individual board can vary, for example, within a few micrometers; on the other hand, this can also occur with the height of the hot melt adhesive coating. In the worst case, these factors can accumulate, causing significant variations in the stack height of the baked stacks. This reduces the repeatability of this method for manufacturing stacks with a stack height hp within the tolerance range Δh relative to a predetermined target stack height hs.

[0003] US 2017 / 001258 A1 therefore proposes adjusting method parameters during the baking of the stack. These parameters include, for example, the temperature profile over time, the axial pressure on the stack, and the detected stack height, to influence the stack height. A disadvantage is that the axial pressure on the stack cannot be increased indefinitely to reduce the stack height, as this carries the risk of hot melt adhesive being extruded, potentially causing the stack to lose short-circuit protection. Furthermore, this method cannot be used to adjust the stack height when it is below tolerance; therefore, it is only suitable for reducing the stack height. Thus, this method is not universally applicable and is only suitable for minor adjustments to the stack height. Summary of the Invention

[0004] Therefore, the objective of this invention is to modify the method for manufacturing plate stacks of the type described at the beginning, enabling the manufacture of precise plate stacks in a particularly flexible manner and with high repeatability. Furthermore, the method should ensure continuous and energy-efficient stacking of the plate stacks.

[0005] The present invention solves the proposed task through the features of claim 1.

[0006] If the hot melt adhesive coating of the stacked plates is preheated to a first temperature above the glass transition temperature (Tg) of the hot melt adhesive coating but below its baking temperature, and the hot melt adhesive coating is then subjected to pressure in this preheated state, the possibility of flexibly and precisely adjusting the stack height becomes possible in the stacking method according to the invention. This layer bonding under pressure and heat reduces unevenness between the individual plates, and thus allows the stack to be more precisely transformed to the state it would be in after the hot melt adhesive coating has been baked. Therefore, subsequent measurement of the stack height (hp) of each stack made from the stacked plates can be performed with particular precision using a measurement method.

[0007] If, when the detected stack height hpm is below the tolerance range, at least one additional sheet is applied to the end of the relevant stack as necessary, thereby adjusting the stack height hp to a height within the tolerance range Δh relative to the predetermined target stack height hs, a shape-accurate stack can be provided. This is also feasible because the hot melt adhesive coating is not heated to a temperature above the baking temperature, allowing one or more sheets to be applied to their respective stacks without loss of quality. These shape-accurate stacks can then be baked to fix their stack height or, consequently, to harden their hot melt adhesive coating.

[0008] To this end, the hot melt adhesive paint layer of each stack of boards is finally heated to a second temperature greater than or equal to the baking temperature of the hot melt adhesive paint, and thus the boards are baked together with each other via the hot melt adhesive paint layer.

[0009] Furthermore, this possibility of increasing the height of the stack after assembly can help simplify the manufacturing process, for example, by intentionally setting the number of stacked panels in a way that results in insufficient stack height. This safely avoids oversized panels, which, as is well known, cannot typically be reduced sufficiently by applying pressure to the stack (especially in cases where extrusion of hot melt adhesive paint that impairs or jeopardizes function is intolerable).

[0010] Therefore, the method according to the invention is characterized by high repeatability when manufacturing high-precision stacks of plates from sheet metal.

[0011] Furthermore, utilizing the preheated heat energy during final heating can improve energy efficiency in continuous manufacturing of stacked plates.

[0012] Preferably, at least one panel is applied to the hot melt adhesive coating on the stack of panels. This applies the panel to the warm hot melt adhesive coating, which improves the bonding of the additional panels.

[0013] If the at least one plate is heated before being applied to the stack of plates, a temperature drop can be avoided. In this way, improved bonding of the additional plates becomes possible. Preferably, the additional plates are heated to a first temperature.

[0014] When adjusting the stack height, it is preferable to apply pressure to at least one plate on the end side of the stack. This can further improve the adhesion of the plates on the stack.

[0015] Generally speaking, the applied panels can be the same as those stacked on top of each other, and thus a hot melt adhesive paint layer, particularly a baked enamel layer, can also be present on at least one flat side of the applied panel.

[0016] Simple method conditions can be obtained when the first temperature is in the range of 90°C to 150°C, especially 100°C to 120°C, and / or the second temperature is in the range of 180°C to 250°C, especially 180°C to 220°C.

[0017] If the stack height is checked and / or adjusted while the hot melt adhesive paint layer is in a preheated state, a short cycle time can be guaranteed.

[0018] The continuous process of this method is achieved when the hot melt adhesive paint layer is heated to a first temperature in a stacking device connected to a stamping tool, which places the hot melt adhesive paint layer in the stacking device under pressure.

[0019] One can imagine that the alternative process involves introducing a stack of boards made of stacked plates into a first oven, where the hot melt adhesive paint layer is heated to a first temperature.

[0020] This design scheme, which utilizes the method in the process of moving from one device to the next, can also be simplified in terms of handling, for example, by adjusting the stack height in the stacking device and / or baking the plates in the second oven.

[0021] The repeatability of the method can be further improved by subjecting all stacks to the same pressure. Furthermore, trend analysis of the stack height of the plates can therefore be performed repeatably. Preferably, the pressure is between 2 and 10 N / mm. 2 Especially 3 to 5 N / mm 2 Within the range.

[0022] Preferably, the thickness of each plate is between 0.1 and 0.5 mm, particularly between 0.1 and 0.3 mm, and / or the thickness of the hot melt adhesive coating on each plate is between 2 and 12 μm, particularly between 4 and 8 μm. This is a particularly advantageous prerequisite for achieving high repeatability of the method.

[0023] This method is particularly suitable for relatively high stacks of boards, such as when each stack has more than 100 boards.

[0024] If, when stacking boards to their respective stacks, the stack height exceeds the target stack height, reducing the number of boards by at least one can be beneficial for intentionally prioritizing insufficient stack height when stacking boards, while at least avoiding excessive dimensions in the method. This can further improve the repeatability of the method.

[0025] Furthermore, even if the stack height detected when stacking boards for their respective stacks is lower than the target stack height, at least one more board can be added in quantity.

[0026] Preferably, the number of plates stacked on top of each other to form a plate stack is always selected such that the detected stack height is at least lower than the target stack height of the plate stack by the thickness of one of the stacked plates.

[0027] Adjusting the stack height by applying one to five, particularly one to three, pieces to the ends of the stack can help to significantly increase the stack height. This relatively small adjustment in the number of pieces also helps to avoid other inaccurate factors affecting the shape accuracy of the stack.

[0028] When at least one plate is picked out and used to adjust the stack height before being stacked together, the high fit accuracy of the additional plate relative to the already stacked plates in the stack can be guaranteed. Attached Figure Description

[0029] The inventive subject matter is presented in more detail with reference to several exemplary embodiments in the accompanying drawings. Wherein:

[0030] Figure 1 A schematic diagram of a first apparatus for performing the method according to the invention is shown.

[0031] Figure 2 A schematic diagram of a second apparatus for performing the method according to the invention is shown.

[0032] Figure 3a This shows panels stacked on top of each other according to methods based on existing technology.

[0033] Figure 3b The diagram shows plates stacked on top of each other in the method according to the invention.

[0034] Figure 4a The height curve of the plate stack assembled according to the method according to the prior art is shown, and

[0035] Figure 4bThe height curve of the plate stack assembled according to the method of the present invention is shown. Detailed Implementation

[0036] according to Figure 1 and Figure 2 The diagram shows devices 1a and 1b, used to produce a stack 2 of plates, the stack height hp of which is within a tolerance range relative to a predetermined target stack height hs. The stack 2 is preferably used for electromagnetic components, such as motors.

[0037] Therefore, through such Figure 1 The device 1a shown separates multiple plates 4 from the electrical steel strip 3.

[0038] The electrical steel strip 3 is coated with a thermosetting hot melt adhesive paint layer 7, preferably based on epoxy resin, such as a baked enamel layer. The thermosetting or heat-curing hot melt adhesive paint layer 7 can be made of baked enamel. For example, catalytic baked enamel, such as a baked enamel with a deposition coating for faster reaction, can also be used. Separation of the plates 4 is performed using a stamping tool 5, which may also be part of a subsequent stamping tool (not shown). Other devices for separating the plates 4 are conceivable, such as a laser. The thickness of each plate 4 is preferably between 0.1 and 0.5 mm, and the thickness of each hot melt adhesive paint layer 7 is between 2 and 12 μm.

[0039] The sheet 4 is pushed into the stacking device 6 by the punch 5a of the stamping tool 5. In this stacking device 6, sheets 4 having a hot-melt adhesive paint layer 7, i.e., a baked enamel layer, on at least one flat side 4a are stacked together. Two of these stacked sheets 4 are visible... Figure 3a All the stacked plates 4 leave the stacking device 6 as a plate stack 2, or are separated into plate stacks 2 upon leaving the stacking device 6, which is not shown in detail.

[0040] The stack of plates 2 is then subjected to further process steps, more specifically, the stack of plates 2 is introduced into a first oven 8, so as to preheat the hot melt adhesive paint layer 7 of the stacked plates 4 to a first temperature t1, which is higher than the glass transition temperature Tg of the hot melt adhesive paint 7 and lower than the baking temperature of the hot melt adhesive paint. The first temperature t1 is preferably 90°C.

[0041] In the next step, the plate stack 2 is introduced into the extruder 9, which uses a press head 9a to apply an axial compressive force P acting on the plate stack 2. See [link to relevant documentation]. Figure 3a The compressive force P in the middle.

[0042] The extrusion force P compensates for unevenness, for example, in the joint between the hot melt adhesive paint 7 and the plate 4, or in the joint between the hot melt adhesive paint 7 and subsequent plates 4. For this purpose, see [link to relevant documentation]. Figure 3b .

[0043] The extruder 9 applies the same pressure to all the stacks 2, ranging from 2 to 10 N / mm², preferably 3 to 5 N / mm², i.e., 4 N / mm². For example, this extrusion pressure P can be sufficient to cause complete bonding of the hot melt adhesive layers 7, thereby eliminating free areas between the hot melt adhesive layers 7, such as... Figure 3a As can be seen, this can also significantly improve the bonding between the plates 4, which further enhances the stability of the plate stack 2 manufactured by the method according to the invention.

[0044] like Figure 1 It can be seen that the plate stack 2 or its hot melt adhesive paint layer 7 is maintained at the first temperature t1 during the extrusion process.

[0045] Therefore, all the prerequisites for accurately measuring the stack height hp are provided. For this purpose, the stack 2 is fed to a measuring device 10 in a separate step after the extruder 9, which detects the stack height hpm. Various measurement methods are conceivable, such as optical methods, manual methods, etc., or methods that infer the stack height hpm by positioning the press head 9a of the extruder 9 during or after applying pressure to the stack 4.

[0046] Preferably, the stack height hpm of the board stack 2 when the hot melt adhesive paint layer is in a preheated state is detected, which can further improve the accuracy of the measurement method.

[0047] Then, based on the detected stack height hpm, the stack height hp is adjusted as necessary, more specifically, when the detected stack height hpm is lower than the tolerance range Δh relative to the predetermined target stack height hs. In this case, in the subsequent stack adjustment device 11 of the measuring device 10, an additional plate 4 is applied to the plate stack 2 on the end side 2a of the relevant plate stack 2 to adjust the stack height hp to a height within the tolerance range Δh. In the example, the tolerance range Δh generally (i.e., + / -) corresponds to the thickness d of the plate 4, which is +d / 2 and -d / 2 from the perspective of the target stack height hs.

[0048] This measure ensures the production of particularly precise plate stacks.

[0049] Preferably, the stack height (hp) of the board stack 2 when its hot melt adhesive paint layer 7 is in a preheated state is adjusted, which facilitates the joining of the board 4 and the board stack 2.

[0050] In a subsequent step, the stack of boards 2 is introduced into a second oven 12, where the hot melt adhesive paint layer 7 of the stack of boards 2 is finally heated to a second temperature t2 greater than or equal to the baking temperature of the hot melt adhesive paint, so that the boards 4 are baked together under pressure applied by the oven pressure head 12a for a sufficient baking time. For example, the second temperature t2 is 190°C, and the baking time is 15 minutes.

[0051] Therefore, the method according to the invention is extremely flexible and produces precise plate stacks 2 with high repeatability.

[0052] However, in particular, this method is characterized in that the stack 2 can tend to be undersized by the stacking of plates 4, because it is possible to supplement such an undersized stack 2 with additional plates 4. Therefore, it is unnecessary to bring the oversized stack 2 to standard through pressure during baking, as this can only be achieved to a slight degree. Thus, it is possible to avoid situations that could compromise short-circuit protection between plates 4 or the stack 2. Figure 3b The hot melt adhesive paint extrusion shown in Figure 13.

[0053] according to Figure 2 Device 1b and Figure 1 The main difference with device 1a is that the preheating and pressure loading of the hot melt adhesive paint layer 7 are not performed on the plate stack 2, but in the stacking device 6.

[0054] For this purpose, the stacking device 6 is provided with a wall heater 6a, which heats the hot melt adhesive paint layer 7 to a first temperature t1. On the other hand, the punch 5a pushes the separated plates 4 against the reaction force of the support 6b into the stacking device 6, which causes an axial force to act on the stacked plates 4, and thus puts the preheated hot melt adhesive paint layer 7 under pressure.

[0055] The method is characterized by having fewer method steps and thus resulting in a shorter cycle time for stacking plates with a precise stack height hp.

[0056] Figure 4aA method for stacking boards according to the prior art is disclosed, in which a trend analysis is performed on the height H of 20 stacks. It can be seen that stacks numbered 7 to 13 are oversized, thus exceeding the upper limit of the tolerance range Δh relative to the target stack height hs. This trend is identified by the trend analysis, and the number of boards stacked on top of each other is reduced so that the stack height hp is again within the required tolerance range Δh relative to the target stack height hs. Since the trend of the stack height is decreasing compared to the previous stacks, stack number 16 suddenly becomes undersized. This cannot be corrected in the prior art and becomes scrap. This situation applies at least to stacks numbered 7 to 13, whose oversized dimensions can no longer be compensated for by pressure due to concerns about short circuits caused by hot melt adhesive extrusion.

[0057] Figure 4b The method according to the invention is disclosed, wherein an option exists to supplement the stack 2 of plates 4 with at least one additional plate 4 when necessary. Therefore, the method according to the invention can also be performed when the number of plates 4 stacked on top of each other tends to be insufficient relative to the tolerance range Δh. Therefore, known trend analysis can be ignored, because as previously stated, the stack height hp can always be adjusted to the tolerance range Δh relative to the target stack height hs by applying plates.

[0058] The number of applied plates 4 can be kept small, and preferably one to five plates 4, to ensure the repeatability of the method. For example, according to Figure 4b Two stacked plates 4 are missing in stacks numbered 1, 2, 3, 4, 5, 15, and 19; three stacked plates 4 are missing in stack 16; and one stacked plate 4 is missing in each of the other stacks. This can be seen from the detected stack height hpm.

[0059] The missing plates 4 are applied by the stacking device 6, which ensures that the resulting stack height hp is within the tolerance range Δh relative to the target stack height hs. Therefore, the method according to the invention can produce precisely shaped stacks 3 without defects.

[0060] Adjusting the stack height hs, which is arranged after stacking, can also be relatively easily integrated into this method. This is because the cycle time is essentially predetermined by the fact that the curing time during the final heating period is relatively long.

Claims

1. A method for stacking plates (4) made of electrical steel strip (3) or electrical sheet into a plate stack (2), said plate stacks having a stack height (hp) within a tolerance range (Δh) relative to a predetermined target stack height (hs), wherein, The plates (4) having a hot melt adhesive paint layer (7) on at least one flat side (4a) are stacked on top of each other. The hot melt adhesive paint layer (7) of the stacked plates (4) is preheated to a first temperature (t1), which is higher than the glass transition temperature (Tg) of the hot melt adhesive paint and lower than the baking temperature of the hot melt adhesive paint. The hot melt adhesive paint layer is then placed under pressure in the preheated state. The stack height (hpm) of each stack (2) consisting of stacked plates (4) is detected by a measurement method. If the detected stack height (hpm) is lower than the tolerance range (Δh), at least one additional plate (4) is applied to the end of the relevant stack (2) to adjust the stack height (hp) to a height within the tolerance range (Δh) relative to a predetermined target stack height (hs). The hot melt adhesive paint layer (7) of each stack (2) is finally heated to a second temperature (t2) that is greater than or equal to the baking temperature of the hot melt adhesive paint, thereby baking the boards (4) of the stack together via the hot melt adhesive paint layer (7).

2. The method according to claim 1, characterized in that, Apply at least one plate (4) to a hot melt adhesive layer on a plate stack (2), and / or heat the at least one plate before applying it to the plate stack (2), and / or apply the at least one plate under pressure.

3. The method according to claim 1 or 2, characterized in that, The first temperature (t1) is in the range of 90°C to 150°C, and / or the second temperature (t2) is in the range of 180°C to 250°C.

4. The method according to claim 1 or 2, characterized in that, The stack height (hpm) and / or the stack height (hp) are detected and / or adjusted while the hot melt adhesive paint layer (7) is in a preheated state.

5. The method according to claim 1 or 2, characterized in that, The hot melt adhesive paint layer (7) is heated to the first temperature (t1) in a stacking device connected to a stamping tool, and the stamping tool puts the hot melt adhesive paint layer in the stacking device under pressure.

6. The method according to claim 1 or 2, characterized in that, A stack (2) of boards (4) stacked on top of each other is introduced into a first oven (8) where the hot melt adhesive paint layer (7) is heated to the first temperature (t1).

7. The method according to claim 1 or 2, characterized in that, The stack height (hp) is adjusted in the stack adjustment device (11) and / or the plate (4) is baked in the second oven (12).

8. The method according to claim 1 or 2, characterized in that, All stacks (2) are subjected to the same high pressure, and / or the pressure is between 2 and 10 N / mm. 2 Within the range.

9. The method according to claim 1 or 2, characterized in that, The thickness of each plate (4) is between 0.1 and 0.5 mm, and / or the thickness of the hot melt adhesive paint layer (7) of each plate (4) is between 2 and 12 µm.

10. The method according to claim 1 or 2, characterized in that, Each stack (2) has more than 100 pieces (4).

11. The method according to claim 1 or 2, characterized in that, If the stack height (hpm) of the stack (2) is detected to exceed the target stack height (hs) when the boards (4) are stacked together for their respective stacks (2), at least one board (4) shall be reduced in number.

12. The method according to claim 1 or 2, characterized in that, If the stack height (hpm) of the stack (2) is detected to be lower than the target stack height (hs) when stacking the plates (4) to each other for their respective stacks (2), at least one more plate (4) is added in quantity.

13. The method according to claim 1 or 2, characterized in that, The number of plates (4) stacked together to form a plate stack (2) is always selected such that the detected stack height (hpm) is at least lower than the target stack height (hs) of the plate stack (2) by the thickness of one plate (4) of the stacked plates (4).

14. The method according to claim 1 or 2, characterized in that, The stack height (hp) is adjusted by applying one to five plates (4) to the end of the end side of the plate stack (2).

15. The method according to claim 1 or 2, characterized in that, Before stacking the plates (2), at least one plate (4) is picked out and used to adjust the stack height (hp) before stacking them together.

16. The method according to claim 1, characterized in that, The hot melt adhesive paint layer is a baked enamel layer.

17. The method according to claim 3, characterized in that, The first temperature (t1) is in the range of 100°C to 120°C.

18. The method according to claim 3, characterized in that, The second temperature (t2) is in the range of 180°C to 220°C.

19. The method according to claim 8, characterized in that, The pressure is between 3 and 5 N / mm. 2 Within the range.

20. The method according to claim 9, characterized in that, The thickness of each plate (4) is between 0.1 and 0.3 mm.

21. The method according to claim 9, characterized in that, The thickness of the hot melt adhesive paint layer (7) on each panel (4) is between 4 and 8 µm.

22. The method according to claim 14, characterized in that, The stack height (hp) is adjusted by applying one to three plates (4) to the end of the end side of the plate stack (2).

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