Joining method and machining head and manufacturing machine for carrying out the method

Abstract

A joining method for connecting at least two thermoplastic workpieces is provided to permit the joining even of non-transparent carbon fiber reinforced plastics parts by means of laser welding, in which a splice is produced at the edge regions of the workpieces and the workpieces are subsequently positioned relative to one another in such a manner that the opposite splice regions bound a seam region. Connecting bodies are then inserted into the seam region and heated by means of local heat input by laser beam such that a fixed integrally bonded connection forms between the workpieces and the connecting bodies.

Claims

1. A joining method for connecting at least two thermoplastic workpieces, with the steps of: a) splicing edge regions on a first workpiece and a second workpiece in order to produce splice regions on each of the first and second workpieces region, wherein—at least one of: the splicing takes place by at least one of corresponding fiber placement, material abrasion, laser ablation, machining or milling, the at least one splice region is formed in a stepped manner by a plurality of workpiece layers of the workpiece, the splice region is pretreated by fibers of the workpiece being exposed, the splice region is pretreated by fibers of the workpiece being exposed by means of laser surface treatment, the splice region is pretreated by the first one of the workpieces being coated with a microstructured functional layer, or the splice region is pretreated by the workpiece being plasma-coated with a microstructured functional layer; b) positioning the first and second workpieces relative to one another in such a manner that the splice regions of the first workpiece and the second workpiece bound a seam region and are in mirror relationship forming a gap extending parallel to lengths of the first and second workpieces and between respective lowermost surfaces of the first and second workpieces; c) inserting a connecting body into the seam region and heating part of the connecting body by means of local input of heat in order to form an integrally bonded connection between each workpiece and the connecting body, and when the connecting body layer is inserted, the connecting body is pressed by a pressing device which detects the connecting body, and a counter pressing device which detects the first and second workpieces and the counter pressing device has a blade which is introduced into the gap between the respective lowermost surfaces of the first and second workpieces when the pressing takes place.

2. The joining method as claimed in claim 1, wherein, in step b), the workpieces are positioned in such a manner that a width of the seam region increases or increases step by step in a direction perpendicular to the workpiece layers from a lowermost surfaces to the uppermost surfaces of the first and second workpieces.

3. The joining method as claimed in claim 1, wherein, in step c), the pressing device detects the connecting body on a connecting body wide side facing away from the first and second workpieces.

4. The joining method as claimed in claim 3, wherein the pressing device comprises a pressing roller.

5. The joining method as claimed in claim 1, wherein, in step c), the connecting body is heated on an individual, connecting body wide side.

6. The joining method as claimed in claim 1, wherein, in step c), a plurality of connecting bodies are inserted and heated layer by layer in order to produce a connecting body layer which is connected in an integrally bonded manner to the first and second workpieces.

7. The joining method as claimed in claim 1, wherein the counter pressing device detects a lowermost layer of at least one of the first and second workpieces.

8. The joining method as claimed in claim 1, wherein at least one of: the counter pressing device extends below and between the first and second workpieces; the counter pressing device has a counter pressing roller which is arranged opposite the pressing device.

9. The joining method as claimed in claim 8, wherein the counter pressing roller is arranged on an end region of the blade.

10. The joining method as claimed in claim 1, wherein, in step c), when a second or further connecting body layer is inserted, the connecting body is pressed against the first and second workpieces, only by means of the pressing device which detects the connecting body.

11. The joining method as claimed in claim 10, wherein the connecting body is pressed against a workpiece layer corresponding to the connecting body layer.

12. The joining method as claimed in claim 1, wherein, in step c), the heating takes place by scanning a laser beam over the seam region.

13. The joining method as claimed in claim 1, wherein, in step c), the manufacturing gap is filled by means of filling material during an insertion and heating of a first connecting body layer.

14. The joining method as claimed in claim 1, wherein the connecting body is in the form of a flexible connecting strip; the connecting body contains an at most partially cured fiber reinforced plastic or is manufactured therefrom; the connecting body contains a metal sheet or is manufactured therefrom; the connecting body contains a fiber metal layer or is manufactured therefrom; the connecting body contains a multi-layered, fiber reinforced plastic or is manufactured therefrom; or the connecting body contains a fiber reinforced plastic and the fiber reinforced plastic is one of a carbon fiber reinforced plastic or a glass fiber reinforced plastic.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments will be explained in more detail with reference to the attached schematic drawings, in which:

(2) FIG. 1 shows an exemplary embodiment of a manufacturing machine;

(3) FIG. 2 shows an exemplary embodiment of a machining head;

(4) FIG. 3 shows a detailed view of part of the machining head from FIG. 3;

(5) FIG. 4 shows a cross-sectional view of a seam region;

(6) FIG. 5 shows a perspective view of a seam region;

(7) FIG. 6 shows a view of a pretreated splice region;

(8) FIG. 7 shows an exemplary embodiment of a pretreatment device; and

(9) FIG. 8 shows an exemplary embodiment of a functional layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(10) Reference is first of all made to FIG. 1 which shows a partial view of a manufacturing machine 10. The manufacturing machine 10 extends along a longitudinal direction which may also be referred to as the manufacturing direction.

(11) The manufacturing machine 10 comprises a tool transport device 12 which is designed for transporting different machining heads 14. The tool transport device 12 has two tool transport units 16 which are spaced apart along the manufacturing direction. The machining head 14 is arranged between the two tool transport units 16.

(12) The tool transport units 16 are moved along the manufacturing direction by means of pneumatic or hydraulic cylinders 18. The tool transport units 16 are moved discontinuously here, while the machining head 14 is moved continuously. The tool transport units 16 have guide devices 20 which are spaced apart transversely with respect to the manufacturing direction and are guided on guide rails 24 by means of guide rollers 22. The guide rails 24 are only partially illustrated for the purpose of clarity.

(13) An exemplary embodiment of the machining head 14 is illustrated in more detail in FIG. 2 and FIG. 3. The machining head 14 is designed to connect thermoplastic workpieces 26 to one another by means of a connecting body 28.

(14) The machining head 14 comprises a machining head guide device 30 for guiding the machining head 14 along the manufacturing direction which runs from left to right in FIG. 2.

(15) The machining head 14 comprises a supporting frame 32 which provides fastening regions for different components of the machining head 14. The supporting frame 32 has a pair of cylinder couplings 34 by means of which the machining head 14 can be connected to the cylinders 18.

(16) The machining head 14 furthermore comprises a pressing device 36 with at least one pressing roller 38 which can press the connecting body 28 onto at least one of the workpieces 26 in order to connect the latter to one another in an integrally bonded manner.

(17) For the connection, the machining head 14 can furthermore comprise a laser device 40 which can conduct a laser beam 42 onto the workpieces 26 of the connecting body 28 by means of a scanner module 44. The scanner module 44 comprises at least one scanner mirror 45 which is movable by means of an actuator.

(18) The machining head 14 also has a filling material supply device 46 which is designed to supply a filling material 48, for example thermoplastic resin or thermoplastic.

(19) The machining head 14 can have a counter pressing device 50 which is provided in a releasable manner. The counter pressing device 50 preferably has a counter pressing roller 52. The counter pressing roller 52 can be designed to be smaller in diameter than the pressing roller 38.

(20) Furthermore, the counter pressing device 50 can comprise a blade 54 which extends between the workpieces 26 and on the end region 56 of which the counter pressing roller 52 is arranged.

(21) At least one pair of blade guide rollers 58 can be arranged on the blade 54 and can improve the movement of the blade 54 through the workpieces 26.

(22) The pressing device 36 and the counter pressing device 50 define a gap between them for the workpieces 26 and the connecting body 28 such that they can be pressed.

(23) Reference is made below to FIG. 4 and FIG. 5 which show a seam region 60. A first workpiece 62 and a second workpiece 64 comprise a plurality of workpiece layers 66.

(24) The workpiece layers 66 are designed in such a manner, for example as early as during the production or else by material machining after production, that each workpiece 62, 64 has a splice region 68.

(25) Each workpiece 62, 64 comprises a plurality of workpiece layers 70. The workpiece layers 70 are each placed on one another with a workpiece layer wide side 72 such that a workpiece layer narrow side 74 of one workpiece 62, 64 in each case faces a workpiece layer narrow side 74 of the other workpiece 64, 62.

(26) Lowermost workpiece layers 76 which form the lower-side surface of the workpieces 62, 64 can form a manufacturing gap 78 for the blade 54 of the counter pressing device 50. The manufacturing gap 78 is significantly narrower than the distance between the workpiece layer narrow sides 74.

(27) The lowermost workpiece layer 76 can be adjoined by a plurality of workpiece intermediate layers 80 which in turn each rest on one another with their workpiece layer wide side 72.

(28) Furthermore, uppermost workpiece layers 82 which form the upper-side surface of the workpieces 62, 64 can be provided.

(29) In the present example, the lowermost workpiece layer 76 and the workpiece intermediate layers 80 are formed from fiber-reinforced plastics material, while the uppermost workpiece layer 82 is formed from a metal sheet 84. Reference is also made in this connection to fiber metal laminates, FML for short.

(30) It should be noted that any combination is conceivable here and that this primarily depends on the desired application region.

(31) In order to connect the workpieces 62, 64, the procedure is now as follows. A tape-shaped first connecting body 86 which can be supplied, for example, as a connecting tape 88 on rollers and can likewise be formed from fiber-reinforced plastic is inserted into the seam region 60 bounded by the respective splice regions 68 and optionally the manufacturing gap 78 after the first connecting body 86 and the two workpieces 62, 64 have been heated by the laser beam 42 in such a manner that an integrally bonded connection between the first connecting body 86 and the workpieces 62, 64 subsequently takes place with the aid of the pressing device 36 and the counter pressing device 50. In the same time frame, the filling material 48 which is supplied to the seam region 60 by the filling material supply device 46 can completely close the manufacturing gap 78. In both operations, the laser beam 42 is scanned over the entire width of the seam region 60 by means of the scanner module 44 and therefore heat is introduced locally. In the process, only the surfaces of the workpieces 62, 64 and of the first connecting body 86 melt, and therefore excessive heating of the other regions of these components can be prevented.

(32) In a further working step, first of all the counter pressing device 50 is removed and then the operation is repeated with further connecting bodies 90 until the entire seam region 60 is closed off in a flush manner.

(33) Reference is also made below to FIG. 6 to FIG. 8 which show measures for improving the integrally bonded connection by the strength of the connection being able to be increased.

(34) FIG. 6 shows an enlarged detail of a splice region 92 which has been preheated by means of a laser treatment. The parameters of the laser beam have been selected here in such a manner that the fibers of the splice region 92 have been exposed without destruction by ablation of the matrix material. This measure makes it possible to provide a reproducible, consistent surface structure 94. Furthermore, local treatment of the splice region 92 is possible, and therefore this operation can be simply integrated into the previous process. In addition, complicated bath methods can be avoided. Tests by the applicants have shown that the strength of the integrally bonded connection can be increased with this surface structuring.

(35) FIG. 7 illustrates a plasma source 100 for plasma coating. Plasma sources are known as such. The plasma source 100 is connected to an energy supply 102 which supplies electrical energy to a cathode 104 and an anode 106 in order to form a light arc 108 therebetween. The light arc chamber 110 which is of cylindrical design has a plurality of cascade plates 112 which each contain a plasma chamber 114. A plasma gas 116 is supplied via a plurality of plasma gas connections 118. Furthermore, an inert gas 120 is introduced into the light arc chamber 110. By means of a suitable outlet geometry, a substantially rectangular, uniform plasma jet 122 is produced for the plasma coating of a splice region.

(36) FIG. 8 illustrates, at the top and bottom in different enlargements, a microstructured functional layer which is the result of the plasma coating. By means of the micro structured, fractal geometry, the splice region has a higher effective surface than an untreated splice region. Tests by the applicants have also revealed here that the strength of the connection can therefore be increased.

(37) With the concepts described herein, the application region of laser welding methods can be extended to complex systems of fiber-reinforced plastics materials or workpieces without transparent regions being required or without heat having to be passed through an excessively high amount of the component. Overall, connections between fiber composite components can therefore be produced more simply and more robustly.

(38) While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.

LIST OF REFERENCE SIGNS

(39) 10 manufacturing machine 12 tool transport device 14 machining head 16 tool transport unit 18 cylinder 20 guide device 22 guide roller 26 workpiece 28 connecting body 30 machining head guide device 32 supporting frame 34 cylinder couplings 36 pressing device 38 pressing roller 40 laser device 42 laser beam 44 scanner module 45 scanner mirror 46 filling material supply device 48 filling material 50 counter pressing device 52 counter pressing roller 54 blade 56 end region 58 blade guide roller 60 seam region 62 first workpiece 64 second workpiece 66 workpiece layer 68 splice region 70 workpiece layer 72 workpiece layer wide side 74 workpiece layer narrow side 76 lowermost workpiece layer 78 manufacturing gap 80 workpiece intermediate layers 82 uppermost workpiece layer 84 metal sheet 86 first connecting body 88 connecting tape 90 further connecting bodies 92 splice region 94 surface structure 100 plasma source 102 energy supply 104 cathode 106 anode 108 light arc 110 light arc chamber 112 cascade plate 114 plasma chamber 116 plasma gas 118 plasma gas connections 120 inert gas 122 plasma jet