Method and Device for Producing a Composite Sheet-Metal Part with a Metal Edge Region
The invention relates to a method for producing a composite sheet metal part with a metal edge region comprising two outer covering sheets of metal and at least one layer consisting of a plastic arranged between the covering sheets. The method is characterised in that a selected edge region of the composite sheet metal part is heated in such a way that the plastic layer arranged between the outer covering sheets softens, by applying a force to at least one outer covering sheet in the edge region the covering sheets are pressed against one another at some points or regions, so that the plastic layer in the edge region subjected to the force is expelled, and subsequently or at the same time as the application of the force both covering sheets in the compressed edge region are joined to one another at least over some regions or points.
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This patent application is a continuation of PCT/EP2012/070041, filed Oct. 10, 2012, which claims priority to German Application No. 102011054362.7, filed Oct. 10, 2011, the entire teachings and disclosure of which are incorporated herein by reference thereto.
FIELD OF THE INVENTIONThe invention relates to a method for producing a composite sheet metal part with a metal edge region, which comprises two outer covering sheets of metal and at least one layer consisting of a plastic arranged between the covering sheets. In addition, the invention relates to a device for carrying out the method according to the invention.
BACKGROUND OF THE INVENTIONComposite sheet metal parts are often used in the form of a sandwich sheet, which comprises two outer covering sheets and a non-metallic sheet, normally consisting of a plastic that is arranged between the covering sheets. One reason for the increasing use of composite sheet metal parts is the fact that composite sheet metal parts can have properties that are often mutually excluded in a sheet of solid material. A composite sheet metal part provides for example, despite its low weight, locally extremely good stiffness properties and can at the same time exhibit very good sound-damping properties. Many applications mean, however, that these composite sheet metal parts have to be joined to other sheet metal parts or metal parts. The joining methods commonly used with sheets, such as fusion welding and soldering, cause problems, however, on account of their high energy input. With the high energy input, the composite sheet metal part may be damaged due to the fact that the non-metallic layer or plastic layer arranged between the covering sheets is damaged by the heat input, and as a result a sufficiently good connection between a composite sheet metal part and a metal part can be achieved only with difficulty. Hitherto various approaches have been attempted in order to solve this problem. From Japanese patent application JP 06-087079 A it is known to prepare the edge region, often used for the joining to further parts, of a composite sheet metal part for a weld joint by first of all heating the edge region of the composite sheet metal part, bending the two outer covering sheets over in the edge region, and removing the plastic layer arranged between the covering sheets by employing abrasive means. The covering sheets of the edge region are then welded to one another, so that a composite sheet metal part with a purely metal edge region is made available, which can then be used for conventional joining methods. This method is, however, very complicated and can be automated only with difficulty.
Starting from this prior art the object of the present invention is accordingly to provide a method for producing a composite sheet metal part with a metal edge region that enables a corresponding sheet metal part to be produced economically and with a high degree of automation. In addition, the object of the invention is to propose a device to be used for carrying out the said method.
SUMMARY OF THE INVENTIONAccording to a first teaching of the present invention the afore described object is achieved by a generic method, in which
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- a selected edge region of the composite sheet metal part is heated so that the plastic layer arranged between the outer covering sheets softens,
- by applying a force to at least one outer covering sheet in the edge region the covering sheets are pressed against one another at some points or regions, so that the plastic layer in the edge region subjected to a force is expelled, and
- subsequently or at the same time as the application of the force both covering sheets in the compressed edge region are joined to one another at least over some regions or points.
In contrast to the method known from the prior art the covering sheets are not bent over and the plastic layer is not removed via abrasive means, but due to the application of a force to at least one outer covering sheet the plastic layer is expelled from the edge region. The edge region of a composite sheet metal part is understood to be a region of the composite sheet metal part that is a distance of 10 mm to 100 mm from the edge of the composite sheet metal part. Due to the joining of the two outer covering sheets over some regions or points in the these edge regions, in which the plastic has been removed, a composite sheet metal part is obtained in a simple manner having a purely metal edge region, which to this extent is therefore also suitable for the conventionally employed joining methods, such as for example fusion welding or soldering. Due to the fact that the bending of the outer covering sheets and the removal of the plastic layer by using abrasive means can be dispensed with, it is found that the production of a composite sheet metal part with a purely metal edge region can be implemented significantly more economically. The method can also be automated extremely easily and as a result provides composite sheet metal parts that can be joined very easily.
Particularly preferably composite sheet metal parts whose plastic layer has a greater wall thickness than the associated metallic covering sheets are joined using the method according to the invention. For example, the metallic covering sheets can have a wall thickness of 0.1 mm to 0.3 mm, whereas the plastic sheet has a wall thickness of 0.35 mm to 0.8 mm. Corresponding composite parts have considerable weight advantages compared to solid materials, and can be joined particularly well using the method according to the invention
According to a first arrangement of the method according to the invention the plastic expelled in the edge region is at least partly removed mechanically and/or via a suction device. A mechanical removal of the displaced plastic can, for example, be performed by abrasion using an abrasive device. The combination of a suction device that sucks out the exiting, soft plastic, and an abrasive device is also conceivable, so that a finishing operation of the outer edge region of the composite sheet metal part after the fabrication of the metal edge region is no longer necessary. The abrasive device can also at the same time be used for further tasks, for example electrode cleaning, for example if roller electrodes are used for heating the edge region or for joining the edge regions.
If the heating of the edge region of the composite sheet metal part is carried out convectively, conductively, inductively, by friction and/or using electromagnetic radiation, a heated shape of the edge region of the composite sheet metal part that matches the intended use can be ensured. With convective warming the heat transfer takes place for example by hot gases via convection. Use is made of the fact that the covering sheets can transfer the heat locally extremely efficiently to the plastic layer arranged between them. In the case of conductive heating the heating zone can be limited locally to strictly defined regions, namely the contact points, through which the current is to flow. In addition, the means for conductive heating can also be used for the application of a force. In those cases in which a contact-free, locally strictly limited heating is desired, this can also take place via induction, i. e., by inducing eddy currents. A further possibility of heating the edge region of the composite sheet metal part from which the plastic layer is to be removed is by friction, for example in which a sonotrode transmits ultrasound vibrations to the composite sheet metal part. This heating of the covering sheets of the composite sheet metal part is also very localised and ensures that the plastic layer in the remaining regions of the composite sheet metal part is not adversely affected. At the same time an ultrasound sonotrode, for example, can be used not only to transmit a force but also to weld the outer covering sheets in the edge region. Finally, the use, for example, of electromagnetic radiation, for example laser radiation in the near infra-red region or also near infra-red (NIR) radiators, provides a particularly convenient and effective heating of specific edge regions of the composite sheet metal part. The use of electromagnetic radiation enables the heating region to be widened or limited in a particularly targeted manner.
According to a further advantageous embodiment of the method according to the invention the application of the force takes place using at least one or more rollers. When using rollers, the contours of edge regions that had previously or simultaneously been heated can be followed by the rollers, and in this way for example longitudinal edges of a composite sheet metal part can be provided in a simple manner with a non-metallic edge region. In this connection it is not important whether one roller is used, which exerts a force on an outer covering sheet, the second outer covering sheet being pressed against a dolly bar or counter holder, or whether two rollers, respectively arranged opposite one another, press against the outer covering sheets. In both cases with conductive heating, for example, the roller can also serve as a contact roller, which is suitable for conducting the current and thus allows a punctiform heating of the edge region.
Preferably, by using one or more rollers the edge region of the composite sheet metal part is welded over some points or regions after or during the application of the force. Owing to the use of the rollers a particularly effective production of a composite sheet metal part with a purely metal edge region is ensured. For example, an arrangement of two pairs of rollers viewed in the longitudinal direction of the edge region can be used to conductively heat the selected edge region first of all via the first pair of rollers and to apply a force, and then using the second pair of rollers to weld the compressed edge region of the composite sheet metal part over some points or regions.
In the edge regions of the composite sheet metal part the overall thickness of the composite sheet metal part is reduced as a result of the plastic that has been expelled. According to a further advantageous arrangement of the method according to the invention, in the compressed edge region of the composite sheet metal part at least some regions on one or both sides are provided to compensate the thickness, so that the overall composite sheet metal part has an almost uniform thickness.
According to a next advantageous variant of the method according to the invention, during the heating and expulsion of the plastic layer between the two outer covering sheets of the composite sheet metal part, a force is exerted on at least one outer covering sheet that is greater than that exerted during the joining of the two covering sheets. In this way the heating temperatures in the edge region to be prepared can be kept low at least during the expulsion of the plastic, so that the damage to the plastic layer that adjoins the metal edge region of the composite sheet metal part is small. In addition, a particularly comprehensive expulsion of the plastic between the two outer covering sheets is thereby achieved, so that the subsequent welding of the two outer covering sheets is accomplished particularly easily. The currents employed in a conductive heating and a subsequent conductive joining can, for example, behave exactly inversely. In the expulsion of the plastic the currents are lower, in order simply to soften the plastic layer. With the joining over at least some regions or points of the outer covering sheets a higher current can be chosen, so as to enable a joint to be produced.
According to a further embodiment of the method according to the invention the composite sheet metal part is joined at the same time, i. e. during the fabrication of the metal edge region, to a further metal part. The fabrication of the metal edge region and the joining to a further metal part can thereby be accomplished in a single process step.
If the composite sheet metal part simply comprises one outer covering sheet of metal and a plastic layer arranged on the covering sheet, the second metal covering sheet can be provided by the metal part to which the composite sheet metal part is to be joined, so that the composite sheet metal part in the edge region can be joined without any problem to the metal part by welding. In this way composite sheet metal parts with an outer covering sheet and a plastic layer arranged thereon can easily become an integral component of appliances or devices, for example dishwashers or railway lines, and their sound-damping properties can be utilised.
According to a second teaching of the present invention the object described above is achieved by a device for carrying out the method, which comprises
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- means for positioning a composite sheet metal part,
- means for warming an edge region of the composite sheet metal part over some points or regions,
- means for applying a force by means of a covering sheet of the composite sheet metal part in the heated edge region, in order to press this covering sheet against a further metal sheet, so that the heated and soft plastic layer arranged on the covering sheet is expelled from the edge region, and
- means for joining the covering sheet at least over some regions or points to a further metal sheet in the compressed edge region of the composite sheet metal part.
The second outer covering sheet of a composite sheet metal part with two outer covering sheets and a plastic layer arranged there between can obviously also be used as a metal sheet. The device enables the method according to the invention to be carried out, so that an economic production of the composite sheet metal parts with two outer covering sheets and a plastic layer arranged there between, and also comprising a metal edge region, is ensured. In addition, the device according to the invention also enables a composite sheet metal outer part with a single outer covering sheet and a plastic layer arranged thereon to be joined economically to a further metal part.
In a simple way longitudinally extending edge regions of a composite sheet metal part can in one arrangement of the device according to the invention be produced with a metal edge region, wherein the arrangement of the device according to the invention is provided with one or more rollers for applying a force and/or for heating and/or for joining the edge region of the composite sheet metal part, as well as with means for effecting a relative movement between the composite sheet metal part and rollers. The relative movement between the composite sheet metal part and rollers enables the contours of an edge region to be followed, and at the same time the application of force, a heating, and simultaneously a welding over some points or regions of the two outer covering sheets of a composite sheet metal part or of the outer covering sheet to a further metal part, becomes possible.
A further arrangement of the device according to the invention enables the edge regions to be machined, for example to remove excess plastic, is not necessary by providing an abrasive device and/or a suction device to remove the expelled plastic. On the one hand, as already explained, a further machining of the composite sheet metal part is avoided, and on the other hand it can be ensured via the suction device, which is preferably arranged in the region of the heating and compression of the edge region, that excess plastic does not interfere with the joining process of the two outer covering sheets or of the outer covering sheet to a further metal part.
In addition, the device according to the invention can furthermore be configured so that a first and a second pair of rollers are provided, wherein the first and the second pair of rollers are arranged behind one another seen in the longitudinal direction of the edge region of the composite sheet metal part, wherein the first pair of rollers is used for the heating and compression of the edge region of the composite sheet metal part and the second pair of rollers is used for the joining over some points or regions of the edge region of the composite sheet metal part. The processing speeds for the production of the composite sheet metal parts with a metal edge region can be increased by allocating the processes of heating and expelling the plastic to the first pair of rollers, and allocating the joining over some points or regions of the edge region to the second pair of rollers.
Finally, if a multi-axis arm robot and/or a handling system is provided according to a further arrangement of the device according to the invention, the automation of the production of composite sheet metal parts with a metal edge region can be significantly enhanced. If, for example, the means for the positioning, the means for the heating over some points or regions of an edge region of the composite sheet metal part, the means for the application of a force to the edge region and the means for the joining of the composite sheet metal part over some points or regions are controlled via a multi-axis arm robot or a handling system, a highly automated fabrication of composite sheet metal parts with a metal edge region can be achieved.
The invention will be described in more detail hereinafter with the aid of exemplary embodiments and in conjunction with the drawings, in which:
A first embodiment of the method according to the invention is first of all illustrated in
In the figures the thickness relationships of the covering sheets and of the plastic layers are not shown strictly to scale. The wall thickness of the plastic layer is preferably larger than that of the covering sheets. For example, the metal covering sheets can have a wall thickness of 0.1 mm to 0.3 mm, whereas the plastic layer has a wall thickness of 0.35 mm to 0.8 mm. Composite sheet metal parts with covering sheets of 0.25 mm wall thickness and a plastic layer of 0.4 mm wall thickness are particularly preferred. Corresponding composite parts have significant weight advantages compared to solid materials and can be joined particularly efficiently using the method according to the invention.
A similar exemplary embodiment of the method according to the invention is illustrated in
An embodiment of the method according to the invention is now illustrated in
The force/time diagram and current/time diagram illustrated in
Resistance welding of the edge region of the composite sheet metal part is preferred, however.
Further application possibilities of the method according to the invention are illustrated in
Finally,
Claims
1. Method for producing a composite sheet metal part with a metal edge region, which comprises two outer covering sheets of metal and at least one layer arranged between the covering sheets consisting of a plastic, the method comprising the steps of:
- heating a selected edge region of the composite sheet metal part in such a way that the plastic layer arranged between the outer covering sheets softens,
- applying a force to at least one outer covering sheet in the edge region such that the covering sheets are pressed against one another at some points or regions so that the plastic layer in the edge region subjected to a force is expelled, and
- joining, subsequently or at the same time as the application of the force, both covering sheets in the compressed edge region to one another at least over some regions or points.
2. Method according to claim 1, wherein the plastic expelled in the edge region is at least partially removed mechanically and/or by means of a suction device.
3. Method according to claim 1, wherein the heating of the edge region of the composite sheet metal part takes place by at least one of convectively, conductively, inductively, by friction or by using electromagnetic radiation.
4. Method according to claim 1, wherein the application of the force takes place using at least one or more rollers.
5. Method according to claim 1, wherein the edge region is welded over some points or regions using one or more rollers.
6. Method according to claim 1, wherein the compressed edge region of the composite sheet metal part sheets for thickness compensation are arranged at least over some regions on one or both sides.
7. Method according to claim 1, wherein the force exerted during the heating and expulsion of the plastic layer is greater than during the joining of the two covering sheets.
8. Method according to claim 1, wherein the composite sheet metal part is joined at the same time to a further metal part.
9. Method according to claim 8, wherein the composite sheet metal part comprises only one outer covering sheet of metal and a plastic layer arranged on the covering sheet, and a second metal covering sheet is provided by the metal part to which the composite sheet metal part is to be joined.
10. Device for carrying out a method according to claim 1 comprising:
- means for positioning a composite sheet metal part,
- means for warming an edge region of the composite sheet metal part over some points or regions of an edge region of the composite sheet metal part,
- means for applying a force by means of at least one covering sheet of the composite sheet metal part in the heated edge region in order to press this covering sheet against a further metal sheet so that the heated and soft plastic layer arranged on the covering sheet is expelled from the edge region, and
- means for joining the covering sheet at least over some regions or points to the metal sheet in the compressed edge region of the composite sheet metal part.
11. Device according to claim 10, wherein there are provided one or more rollers for applying a force and/or for heating and/or for joining the edge region of the composite sheet metal part and also means for effecting a relative movement between the composite sheet metal part and rollers.
12. Device according to claim 10, wherein an abrasive device and/or a suction device is provided to remove the expelled plastic.
13. Device according to claim 10, wherein a first and a second pair of rollers are provided wherein the first and the second pair of rollers are arranged behind one another viewed in the longitudinal direction of the edge region of the composite sheet metal part, wherein the first pair of rollers is used for heating and compressing the edge region of the composite sheet metal part and the second pair of rollers is used for joining, over some points or regions, the edge region of the composite sheet metal part.
14. Device according to claim 10 wherein a multi-axis arm robot and/or a handling system is/are provided.
Type: Application
Filed: Apr 7, 2014
Publication Date: Oct 9, 2014
Applicant: ThyssenKrupp Steel Europe AG (Duisburg)
Inventor: Azeddine Chergui (Dortmund)
Application Number: 14/246,604
International Classification: B21C 37/02 (20060101);