WO2020030513A1

WO2020030513A1 - Device and method for producing fibre stacks

Info

Publication number: WO2020030513A1
Application number: PCT/EP2019/070740
Authority: WO
Inventors: Michael Kaiser; Andreas Pröhl; Marco Göttinger; Andreas Krasel; Marc-Antonio PADILLA; Andreas Silvan; Ingo ENDEL; Arvid Richter
Original assignee: Voith Patent Gmbh; Audi Ag
Priority date: 2018-08-09
Filing date: 2019-08-01
Publication date: 2020-02-13
Also published as: DE102018119368A1

Abstract

A device for producing flat fibre stacks comprising a plurality of layers consisting of sections, placed next to one another, of fibre strips, wherein the fibre strips each comprise a plurality of unidirectional rovings, comprises a first spreading apparatus (2.1), a second spreading apparatus (2.2), a third spreading apparatus (3), and a fault detection unit (10), which is able to detect faults in the spreading quality; wherein the second spreading apparatus (2.2) is arranged under the first spreading apparatus (2.1), and wherein some first rovings (20.1) provided next to one another can be fed first to the first spreading apparatus (2.1) and then to the third spreading apparatus (3) and some second, other rovings (20.2) provided next to one another can be supplied first to the second spreading apparatus (2.2) and then to the third spreading apparatus (3) in such a way that the rovings (20.1, 20.2) are first spread either only in the first spreading apparatus (2.1) or only in the second spreading apparatus (2.2) and all rovings (20.3) are then spread together in the third spreading apparatus (3) in a manner running parallel next to one another.

Description

Device and method for producing fiber stacks

The invention relates to a device for producing flat fiber stacks, which comprise a plurality of layers, each of which consists of sections of fiber tapes placed next to one another, the fiber tapes each comprising a plurality of unidirectional rovings, and the device comprising the following components:

- several unwinding stations for the provision of several endless rovings arranged side by side,

at least one application device for binder or matrix material,

- at least one train,

- at least stockpiling to enable continuous processing of the rovings despite discontinuous storage of the sections,

a laying system comprising a plurality of belt transfer units arranged side by side, each of which can clamp a sliver, a plurality of grippers arranged side by side, each of which grips a fiber sliver at its beginning and can stretch the fiber sliver between the gripper and the belt transfer unit by means of a linear process, a plurality of separating units which divide the fiber sliver into sections can cut through, and a turntable with a storage surface on which the sections can be placed essentially simultaneously next to each other and on which several layers with different fiber directions can be built up to form a fiber stack. The storage system is designed in such a way that each belt transfer unit is assigned a gripper and the grippers can be moved back and forth individually and independently of one another on parallel paths between an individual maximum position and a pick-up position at the belt transfer unit.

Fiber stacks are called a stack of several layers of fibers; they are used as semi-finished products for the production of components made of fiber-reinforced plastic. Fiber-reinforced plastic consists of matrix material and of fibers which are embedded in the matrix material and which, among other things, provide the tensile strength. Fiber-reinforced plastic is used particularly for components that are subject to high loads, which should still be as light as possible. Since the fibers do not impart any strength in the transverse direction, the fibers must be aligned in such a way that their longitudinal direction matches the respective load direction as closely as possible. To achieve this, the fibers often have to be laid in different directions. The better and more precisely the fiber layer is adapted to the load, the better the component will be.

So that the fiber stacks have sufficient dimensional stability for further processing, they are provided with small amounts of glue or binder and fixed after laying down, e.g. by drying or by heating and cooling. Or the fiber tapes are already impregnated with the as yet uncured matrix material and thus deposited.

In order to manufacture a CFRP component, the fiber stacks are shaped in further processing steps using molding tools, if not already provided with matrix material and hardened or consolidated, if necessary also under pressure. The matrix material can be a thermoset plastic, in particular a flarz or a thermoplastic.

If a particularly high strength is to be achieved, so-called continuous fibers, also known as yarn, are usually used as fibers. The multiple unwinding stations can, for example, be designed as a so-called creel. The yarns or rovings can be drawn from bobbins or from bobbins. Numerous yarns that are unwound simultaneously from a spool or from a skein are called yarn bundles or roving. The rovings can consist of up to several tens of thousands of individual yarns, which are also called filaments. Carbon fibers in particular come into consideration as fiber material, but also glass fibers, aramid fibers or the like. DE 102011007018 A1 describes a device for producing flat fiber stacks from unidirectional sections of fiber ribbons. Here a depositing system with several grippers operated in parallel is provided, there is tension regulation and a spreading device and binder material can be applied to the rovings.

For spreading rovings or fiber tapes, there is, for example, prior art in DE 102005008705 B3 or in EP 2138615 B1, which show spreading units with multiple deflection around guide rollers and with a band store.

WO 2012/120064 A1 discloses a device for the continuous production of fiber-reinforced composite materials, which separately spreads at least two rovings in a spreading unit and then brings them together and impregnates them with matrix material. Furthermore, it is disclosed that the spreading quality of the rovings can be measured and the spreading unit can be regulated via a target / actual comparison.

A disadvantage of the devices known in the prior art is that, despite the regulation of tension and spreading, defective sections are always deposited if the control options are insufficient and the whole fiber stack is of lower or fluctuating quality. So it happens again and again that an entire fiber stack has to be discarded as rejects. Due to the relatively high material costs for the fibers, this leads to unacceptable manufacturing costs in many cases. This currently limits the application options for such filing processes or requires manual intervention during manufacture, which in turn limits the manufacturing costs and thus the possible uses for CFRP components.

The object of the invention is to provide a device for producing fiber stacks which is easy to automate and which can be used to reliably produce error-free, uniform and inexpensive fiber stacks. The object is achieved by the device with the features according to claim 1. Further advantageous features are mentioned in the dependent claims.

According to the invention, the device is characterized in that the device comprises the following further components:

- a first spreading device (2.1),

- a second spreading device (2.2),

- a third spreading device (3),

- and an error detection unit (10) arranged between the third spreading device (3) and the belt transfer units (11), which can detect errors in the spreading quality;

the second spreader (2, 2) below the first spreader

(2.1) is arranged,

and wherein a first part of the rovings provided side by side

(20.1) can first be fed to the first spreader (2.1) and then to the third spreader (3) and a second, different part of the rovings (20.2) provided next to one another can first be fed to the second spreader (2.2) and then to the third spreader (3) can be

in such a way that the rovings (20.1, 20.2) can be spread first either only in the first spreader (2.1) or only in the second spreader (2.2) and then together in the third spreader (3), all rovings (20.3) running parallel to one another ,

A significant advantage of the device according to the invention is that on the one hand a higher spreading quality can be achieved and on the other hand defective sections can be recognized online before being deposited. Due to the special design of the spread and the early quality detection, unnecessary rejects of fiber stacks already deposited can be avoided and rovings with lower or fluctuating output quality can also be avoided are processed without the quality of the fiber stacks being impaired. This offers enormous opportunities to automatically produce more cost-effective CFRP components.

The split treatment of the rovings running in parallel in the first and in the second spreading device prevents neighboring rovings which are still running untidily from influencing one another in an undesirable manner. And by arranging the third spreading devices as second spreading stages, different settings for the spreading can then be made, which further increases the possibilities of influencing.

Another advantage is the compact and very space-saving arrangement of the spread. The device can thus be easily integrated into corresponding production lines. Due to the parallel arrangement of several grippers in the deposit system, a high deposit rate and thus good productivity can also be achieved. There is also a high degree of flexibility and good adaptability for the production of different components.

In a particularly preferred variant of the device, the rovings are guided in such a way that the rovings guided next to one another in the width direction are fed alternately to the first spreading device or the second spreading device. The spread rovings are then brought together and passed through the third spreading device.

In particular, it is advantageous if the depositing system is designed such that when a defective section is identified, this section and all sections spanned at the same time next to it can be deposited outside of the layers already deposited and thus can be discharged, in particular placed in a reject container arranged next to or above the storage area can be.

In this context, “outside” means, for example, one in the top view next to the layers that have already been deposited or next to that for storing layers intended area arranged area meant. Alternatively, it can also be an area arranged in the side view above or below the areas already deposited.

By removing the defective sections, it is avoided that an entire fiber stack from layers that are already well laid down becomes rejects. The device can nevertheless be kept relatively simple by also discharging the other sections already spanned parallel to the depositing. For example, the turntable with the storage surface can in particular be moved or shifted laterally in such a way that the sections are placed next to the storage surface provided for faultless locations or on a reject surface arranged under the storage surface. Alternatively, a reject area or a reject container can also be placed between the clamped sections and the storage area, so that the faulty sections can be placed on this reject area and then removed.

Furthermore, the device can be designed in such a way that sections identified as faulty can be discharged without having to interrupt the unwinding of the rovings. For example, there can be a buffer store in the running direction upstream of the depositing system, into which the endless fiber slivers or rovings are moved after the spreading while the defective sections are being discharged.

In particular, it is advantageous if the third spreading device follows the first / second spreading device directly in the running direction of the rovings, that is to say without a further intermediate functional unit. This ensures that the following functional units are fed well-spread fiber slivers. Alternatively, a functional unit such as, for example, a buffer store as storage and / or a train and / or another functional unit can be arranged in the running direction of the rovings between the first / second spreading device and the third spreading device. This arrangement can also increase the spreading quality and reliability. In a particularly advantageous embodiment, the turntable is additionally designed as a lifting table, with the sections being able to be deposited by the lifting table leading the storage area from below to the clamped sections, at least one, preferably two, hold-down devices per section pressing the sections onto the storage area and the grippers and the belt transfer units release the sections. This ensures that the high-quality sections are stored in the correct position and as required. The device thus enables a high and reliable quality of the semi-finished products produced at a high deposit rate.

The storage surface can be a direct part of the turntable, or a separate so-called stack support or board support, which is arranged on the turntable, can be used as the storage surface. After the laying process, the fiber stack can be transported together with the board carrier to further process steps.

At least one of the spreading units is particularly preferred, in particular all three spreading units are designed as a mutual deflection of the rovings by a plurality of spreading rods. This is a simple yet reliable variant to enable a high spreading quality with a high throughput speed.

In addition, at least one IR heater and at least one subsequent cooling device can preferably be provided, at least the cooling device being arranged after the application device for binder or matrix material. As a result, the spread fiber slivers can be stabilized. The applied material can also be solidified so that it can be deposited more easily.

A particular advantage for the deposit rate and the reliability of the process results if the components mentioned are arranged in the order listed. After spreading, the binder or matrix material is applied and the traction mechanism controls the belt run, so that especially the Spreading is constant. The subsequent stocking enables buffer storage of tape length, which causes a decoupling of the speed between the upstream functional units, which require a speed that is as constant as possible, and the filing system, which requires a cyclical tracking of fiber tapes.

In a further preferred embodiment of the device according to the invention, the error detection unit has a light source and a light receiver for detecting gaps and band edges. The components are arranged so that the fiber slivers to be tested can be passed between the light source and the light receiver. Gaps, width differences or other errors can be detected in this way.

In particular, the application device can be provided to apply resin as a matrix material, in particular in the form of an impregnation bath through which the rovings or fiber tapes are guided or in the form of a spray application or in the form of a film application. In this way, all or part of the amount of matrix required for the subsequent component can be applied before the sections are deposited.

The resin can in particular be a thermosetting plastic, for example an epoxy resin or another resin system.

The device can advantageously be designed such that the grippers can each take various individual intermediate positions on their path. This makes it possible to lay sections of different lengths depending on the desired component shape, which means less waste of expensive fiber material.

Furthermore, the belt transfer units can be moved linearly along the paths of the grippers, which offers additional flexibility in the length and position of the sections, and can thus further reduce the waste in the components. The device can be used particularly advantageously if it is designed such that in each case two to four rovings, in particular exactly three rovings, are moved together to form a sliver and are assigned to a gripper. This means that first the two to four rovings are spread apart in the first or in the second spreading device, then the two to four rovings are brought together to form a fiber band and spread together with further fiber bands treated in the same way in the third spreading device.

The device preferably has a total of between 2 and 6 grippers, in particular exactly four grippers. With this number of grippers, there is sufficient flexibility for the production of different components and, at the same time, a sufficiently high deposit rate is possible to reduce the production times.

It is particularly advantageous if two adjacent grippers of the storage system are so far apart laterally that a gap in the width of the sliver or in the width that corresponds to an integral multiple of the width of the sliver arises when the sections are deposited. This means that the grippers can be made slightly wider than the sliver to be clamped and still not interfere with each other. When the sections are put down, for example, only every second of the intended sections is initially generated and placed on the gap, and then the missing sections are placed in the gaps with an offset of a fiber bandwidth. Similarly, the filing can take place in several stages if the width of the gaps is a higher integer multiple of the fiber width.

Further advantageous features of the invention are explained on the basis of exemplary embodiments with reference to the drawings. They show:

Fig. 1 Schematic representation of an embodiment according to the invention

Fig. 2 shows a detail of a variant of the storage area and the reject container The figures and the exemplary embodiment are described in more detail below.

1 shows a schematic representation of the device. The direction of passage of the rovings 20.1, 20.2 and slivers 20.3, 20.4 is from left to right. The fiber material is made available via a plurality of unwinding stations 1, in which the fiber material is provided in the form of bobbins or balls of yarn (so-called bobbins) and which are arranged in several rows next to one another, one behind the other or one above the other. Together this is also known as a creel.

The first spreading device 2.1 is arranged spatially above the second spreading device 2.2. In this example, both spreading devices are designed as a deflection around several rollers. The feeding of the rovings 20.1, 20.2 to the two spreading devices 2.1, 2.2. is preferably carried out in such a way that rovings guided adjacent in the transverse direction are alternately fed to the first spreading device 2.1 or the second spreading device 2.2. This creates sufficient space in the transverse direction for the first spreading of the rovings, which allows more problem-free spreading even when the starting quality is not so good. This means that cheaper raw materials can also be processed well.

Alternatively, a plurality of adjacent rovings, in particular two to four rovings, which are subsequently brought together to form a fiber band 20.3, can also be treated in the same spreading device, that is to say together in the first or together in the second spreading device. The rovings for adjacent fiber slivers are then alternately fed in groups to the first, upper spreading device or the second, lower spreading device.

The rovings 20.1, 20.2, which were treated in the first spreading device 2.1 or in the second spreading device 2.2, are then brought together directly into fiber bands 20.3 and together in the third Spreading device 2.3 spread again. A particularly good spread is thus reliably possible.

In the embodiment shown, binder or matrix material is then applied by the application device 4, for example in the form of powder or as a spray application. Subsequently, the binder or the matrix material is heated via the heater 5, here as an IR radiator or as a hot air heater, so that the applied material bonds well with the fibers. And then it is solidified again with the cooling device 6, so that the fiber tapes 20.4 are fixed in their spread position. The heater 5 can alternatively be arranged in front of the application device 4, so that the applied material immediately connects to the already warmed fiber tapes.

The traction mechanism 7 ensures a constant and uniform transport of the rovings or the fiber slivers through the upstream units. The traction unit 8, also referred to as a buffer store, follows the traction unit 7.

In the storage 8, the path of the slivers can be changed by shifting the upper and / or the lower guide rollers. This means that the sliver length can be briefly saved and reissued in order to enable even production despite timed filing. In particular for the spreading and the application device, it is advantageous if the rovings or slivers are treated at a constant speed. The slivers 20.4 are stored if the system runs faster before the storage 8 than the system afterwards and the path of the slivers is extended. The slivers are output from the storage 8 when the path of the slivers is shortened and the system runs faster after the storage 8. The filing system can thus pull fiber slivers out of the stock 8 in accordance with the desired cycle. The sliver tension is kept constant even with changing speed via a tensor roller 9. The fault detection unit 10 is arranged in front of the storage system. Here, for example, a light source and an opposing light receiver are used to check whether the fiber ribbons 20.4 have the correct width and are free of gaps.

The beginning of each sliver is picked up by the respective gripper 12 at the band transfer unit 11 and stretched as section 20.5. Grippers 12 and possibly also the belt transfer units 11 can be moved linearly in the belt running direction along the guide rails 13. If section 20.5 has the desired length, the sliver is placed on the storage surface of the turntable 14. Preferably in such a way that the turntable 14 is designed to be height-adjustable and is brought up to the sections 20.5 by lifting it up to the sections 20.5. In addition, hold-down devices can be provided on the grippers and belt transfer units, which press the sections 20.5 onto the storage surface. The fiber slivers are separated at the sliver transfer units 11, so that the sections remain on the storage surface of the turntable 14. The storage system then executes the next cycle by the grippers 12 again grasping the newly formed beginnings of the slivers and then repeating the process steps described above.

The turntable 14 can be rotated every cycle or after several cycles so that sections are deposited at different angles. Completely in accordance with the requirements for the later component. In addition, the turntable 14 can also be moved horizontally, so that sections 20.5 of different cycles can also be placed next to one another on the storage surface at different locations, in order to produce a larger position of sections 20.6 aligned in the same way.

If defective fiber slivers are reported by the error detection unit 10, in the embodiment shown all the sections 20.5 spanned in parallel are discarded by moving the rotary table horizontally to such an extent that these sections 20.5 are not placed on the storage surface, but next to the storage surface, for example in one waste container shown separately. So can continue to produce the filing system in the normal cycle. Only sections 20.5 that were spanned with the faulty section are lost. The loss of expensive fiber material is significantly reduced because entire layers or even entire fiber stacks do not have to be discarded. As an alternative to moving the turntable 14 in the horizontal direction, a reject container, for example in the form of a reject plate, can also be introduced horizontally between the gripper 12 and the turntable 14. The defective sections 20.5 are then placed on this inserted reject container and removed again before the next cycle of the storage system follows.

2 shows a detail of the rotary table 14 with sections 20.6 already deposited and the reject container 15 arranged next to it. The rotary table 14 and the reject container 15 can be moved, for example, via a common horizontal movement device, so that, depending on the signal from the error detection unit, the sections are placed on the storage surface of the rotary table 14 or next to it in the reject container 15.

An additional carrier plate can preferably also be present on the turntable 14, which forms the storage surface for the sections and with which the fiber stacks can be removed from the system and transported further after they have been deposited.

LIST OF REFERENCES

1 unwinding station

2.1 first spreader

2.2 second spreader

3 third spreading device

4 application device

5 pickling

6 cooling device

7 train

8 stockpiling

9 tensor roll

10 error detection unit

1 1 belt transfer unit

12 grippers

13 guide rails for gripper and belt transfer unit

14 rotary table

15 reject bins

20.1, 20.2 rovings

20.3 slivers

20.4 Fibers with applied binder or

matrix material

20.5 Section before dropping

20.6 filed section

Claims

claims

1. Device for the production of flat fiber stacks, which comprise several layers each of sections (20.6) of fiber tapes placed next to one another, the fiber tapes (20.3) each comprising several unidirectional rovings (20.1, 20.2) and the device comprising the following components:

- a plurality of unwinding stations (1) for the provision of a plurality of endless rovings (20.1) arranged next to one another,

- at least one application device (4) for binder or matrix material,

- at least one train (7),

- at least one stockpile (8) to enable continuous processing of the rovings (20.1, 20.2) in spite of discontinuous storage of the sections (20.5, 20.6),

a depositing system comprising a plurality of belt transfer units (11) arranged next to one another, each of which can clamp a sliver (20.3), a plurality of grippers (12) arranged next to one another, each gripping a sliver (20.3) at its beginning and the sliver between the grippers (12 ) and the belt transfer unit (11), several separating units that can cut through the stretched fiber slivers into sections (20.5), and a turntable (14) with a storage surface on which the sections (20.6) can be placed next to each other and at the same time that several layers with different fiber directions can be built up to a fiber stack;

wherein the storage system is designed such that each belt transfer unit (11) is assigned a gripper (12) and the grippers (12) individually and independently of one another on parallel paths between an individual maximum position and a pick-up position at the belt transfer unit (11) are movable here

characterized,

that the device comprises the following further components:

- a first spreading device (2.1),

- a second spreading device (2.2), - a third spreading device (3),

the second spreader (2, 2) below the first spreader

(2.1) is arranged,

and wherein a first part of the rovings provided side by side

2. Device according to claim 1

characterized,

that the depositing system is designed so that when a defective section (20.5) is identified, this section and all the sections (20.5) spanned next to it at the same time can be deposited outside of the already deposited layers and can thus be discharged, in particular into one next to or above or below the storage area arranged reject container (15) can be stored.

3. Device according to one of the preceding claims

characterized,

that sections (20.5) identified as faulty can be removed without having to interrupt the unwinding of the rovings (20.1, 20.2).

4. Device according to one of the preceding claims

characterized, that the turntable (14) is additionally designed as a lifting table, the sections being able to be deposited in that the lifting table brings the storage area from below to the clamped sections (20.5), for each section at least one hold-down device presses the sections onto the storage area and the Release the gripper (12) and the belt transfer units (11).

5. Device according to one of the preceding claims

characterized,

that the first and / or the second and / or the third spreader unit (2.1, 2.2, 3) are designed as a mutual deflection of the rovings (20.1, 20.2, 20.3) by several spreader bars.

6. Device according to one of the preceding claims

characterized,

that the following components are arranged in the order listed:

Spreading devices (2.1, 2.2, 3) - traction mechanism (7) - storage (8) - error detection unit (10) - belt transfer units (11) - gripper (12).

7. Device according to one of the preceding claims

characterized,

that at least one IR heater (5) and at least one subsequent cooling device (6) are provided, at least the cooling device (6) being arranged after the application device (4).

8. Device according to one of the preceding claims

characterized,

that the error detection unit (10) is equipped with a light source and a light receiver for the detection of gaps and band edges.

9. Device according to one of the preceding claims

characterized, that the application device (4) is intended to apply resin as a matrix material, in particular in the form of an impregnation bath through which the rovings (20.3) are guided or in the form of a spray application or in the form of a film application.

10. Device according to one of the preceding claims

characterized,

that the grippers (12) can assume various individual intermediate positions on their path.

11. Device according to one of the preceding claims

characterized,

that the belt transfer units (11) can be moved linearly along the paths of the grippers (12).

12. Device according to one of the preceding claims

characterized,

that two to four rovings (20.1, 20.2), in particular exactly three rovings, are moved together to form a sliver (20.4) and a gripper (12)

assigned.

13. Device according to one of the preceding claims

characterized,

that the device has a total of between 2 and 6 grippers (12), in particular exactly four grippers.

14. Device according to one of the preceding claims

characterized,

that two adjacent grippers (12) are laterally so far apart that when the sections (20.6) are deposited there is a gap in the width of the sliver (20.4) or in the width that corresponds to an integral multiple of the width of the sliver (20.4) , arises.