Overmolding of metallic workpieces

Abstract

Method for processing a metallic workpiece with the following steps: - Providing a metallic workpiece; - Tempering, in particular heating, the workpiece to a predetermined temperature, which depends on the processing temperature of the material; - Overmolding of the tempered workpiece with a material, especially plastic.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a method for processing a metallic workpiece, in particular a busbar. SUMMARY OF THE INVENTION

[0002] Accordingly, it is provided: - a method for processing a metallic workpiece, comprising the following steps: providing a metallic workpiece; tempering, in particular heating, the workpiece to a predetermined temperature which depends on the processing temperature of the material; overmolding the tempered workpiece with a material, in particular with plastic.

[0003] A busbar is an electrical conductor used to transmit current between a power source and a power consumer. Busbars are often designed to transmit high currents or high voltages. Busbars can be constructed, for example, as solid metal bars or as crimped stranded wires.

[0004] A metallic workpiece contains metal.

[0005] Overmolding is a plastics processing technique. Molten plastic is injected into a mold, also known as an injection mold, to produce three-dimensional components. Overmolding often includes the following steps, which are not necessarily part of the process according to the invention: mold preparation, melting the plastic into a melt, overmolding the molten plastic mass, cooling, opening the mold, and demolding.

[0006] Glass fibers are thin, flexible fibers drawn from molten glass or special glass mixtures.

[0007] Carbon fibers, also known as carbon fibers, are lightweight and tensile fibers that contain carbon atoms arranged in a regular crystal structure.

[0008] The gate point or injection point is the location where the melt is injected into the cavity. This point is often equated with the position of the injection nozzle. On a finished workpiece, a so-called gate point can be seen at this point.

[0009] Turbulence refers to the chaotic and / or irregular movement of liquids or gases. This movement is characterized by eddies and unpredictable flow patterns. Accordingly, a turbulence induction point is the location where fluid, which creates turbulence in the material, is introduced into the cavity mold.

[0010] Turbulent components in the flowing material can be identified after curing by the orientation of the material's fibers. Often, the flow direction of the non-fibrous portion of the material is no longer visible during overmolding.

[0011] Fluids are liquids or gases.

[0012] Material deformations as a result of a temperature change are shrinkage or expansion.

[0013] A rounded edge is an edge or corner of an object that is not sharp or right-angled, but has been rounded or beveled.

[0014] The basic idea of ​​the invention is to heat a metallic workpiece, in particular a busbar, to a predetermined temperature before overmolding in order to adjust, in particular to reduce, the temperature difference between the workpiece and the material to a predetermined level.

[0015] Tests by the applicant have shown that when overmolding workpieces that have not been preheated, tensions arise between the workpiece and the material when the workpiece cools down, since the material and the workpiece shrink to different degrees due to an unadjusted temperature difference during processing.

[0016] Although the applicant's tests have shown shrinkage of both the workpiece and the material, other changes in size, such as combinations of shrinkage and expansion or shrinkage of both components, are also conceivable due to different thermal expansion coefficients of the materials processed.

[0017] Advantageous embodiments and further developments emerge from the further subclaims and from the description with reference to the figures of the drawing.

[0018] According to a preferred development of the invention, the metallic workpiece is designed as a busbar.

[0019] Alternatively, the workpiece can also be another metal-containing component that is overmolded with plastic. This particularly applies to heat-resistant components, such as engine parts such as spark plug caps, valve covers, and engine covers; metallic parts of machinery and industrial equipment; lighting components, especially near heat sources; and components near engines or exhaust systems, such as exhaust system parts or engine parts.

[0020] These components experience significant temperature fluctuations. As a result, their metallic portion experiences different thermal expansion than their sprayed portion. This creates tension between the metallic portion and the sprayed portion, which often leads to cracks in the workpiece.

[0021] Further embodiments of the invention are explained below using a busbar. It is understood that this selection is exemplary in nature and does not limit the scope of protection of this patent application.

[0022] According to a preferred embodiment of the invention, the material comprises fibers. Accordingly, the material may comprise a carrier material to which fibers are admixed. Such materials are also referred to as fibrous materials.

[0023] The fibers can, for example, be formed as glass fibers or carbon fibers that are mixed into a carrier material.

[0024] According to a preferred development of the invention, at least one injection point, at which material is injected into a mold, is provided on the busbar to be overmolded, and at least one turbulence induction point, through which fluid is introduced into the mold, is provided, wherein the material flows in the mold in a first flow direction and the fluid flows in the mold in a second flow direction, wherein the flowing material and the flowing fluid cross each other.

[0025] It is understood that the fluid and the material can be similar or identical. If the fluid is a sprayable material, the injection point is designed, in particular, as the main injection point, and the turbulence induction point is designed, in particular, as a secondary injection point.

[0026] It is advantageous if as much fluid is introduced above the turbulence induction point as is required to deflect the fibers of the flowing material.

[0027] It is advantageous if the fibers of the flowing material are swirled by the fluid which is introduced via the turbulence induction point.

[0028] It is understood that any deflection of fibers from their original orientation induces turbulence, even if the fibers are deflected linearly to a large extent and only a small proportion of the fibers are turbulent.

[0029] It is conceivable that the material and the fluid have an identical carrier with a different proportion of fibers or with different fibers. Furthermore, it is conceivable that the material and the fluid are identical. Furthermore, it is also conceivable that the fluid is introduced merely to deflect the fibers and is in the form of a gaseous fluid.

[0030] Accordingly, it is also conceivable to introduce a gaseous fluid into a mold over a large area and the turbulence induction point can accordingly be designed as a turbulence induction region.

[0031] According to a preferred development of the invention, the busbar is heated to a processing temperature of the material.

[0032] Alternatively, it is also conceivable, starting from a reference temperature, to determine a predetermined temperature to which the busbar is to be heated in order to minimize differences in the material deformation during cooling, for an overmolded busbar, and to heat the busbar to this predetermined temperature.

[0033] According to a preferred development, a busbar with rounded edges is provided or the edges of the busbar are rounded within the scope of the described method.

[0034] Rounding edges reduces stresses in a finished workpiece, resulting in fewer material defects that can occur during manufacture or use of a workpiece in edge areas with rounded edges than in the edge area of ​​a workpiece with non-rounded edges.

[0035] It is understood that a busbar which is overmolded with a fibrous material is advantageous if, at least in one region of the overmolded material, fibers are aligned deviating from an injection direction.

[0036] The injection direction from which a finished material was overmolded can be determined based on the surface structure of the workpiece, starting from a so-called sprue point that can be identified in a finished workpiece. TABLE OF CONTENTS OF THE DRAWINGS

[0037] The present invention will be explained in more detail below with reference to the exemplary embodiments shown in the schematic figures of the drawings. In the drawings: Fig. 1 is a schematic block diagram of an embodiment of the invention; Fig. 2 an illustration of an embodiment of the invention; Fig. 3 a view according to Fig. 2.

[0038] The accompanying drawings are intended to provide a further understanding of embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain principles and concepts of the invention. Other embodiments and many of the noted advantages will be apparent upon review of the drawings. Elements of the drawings are not necessarily shown to scale relative to one another.

[0039] In the figures of the drawings, identical, functionally identical and acting elements, features and components are provided with the same reference symbols, unless otherwise stated. DESCRIPTION OF EMBODIMENTS

[0040] Fig. Figure 1 shows a method for processing a busbar, comprising steps S1 to S3. In step S1, a busbar is provided. In step S2, a busbar is heated to a predetermined temperature. In step S3, a heated busbar is overmolded with a material, in particular plastic.

[0041] Fig. Figure 2 shows the orientation of the fibers in an overmolded workpiece 1, which is designed as an overmolded busbar. A gate point 4, which is designed as the main injection point at which the workpiece 1 was overmolded, is visible. The gate point 4 essentially corresponds to the position of a nozzle through which material is introduced into an injection mold. In relation to the method for processing a busbar, the position of the nozzle is also referred to as an injection point. The secondary injection point, through which the material was injected and by means of which the fibers were deflected, is shown as turbulence induction point 5.

[0042] In Fig. 2 it can be seen that the fibers in a first region 2 are aligned according to the flow direction of the fluid and have not been deflected, whereas the fibers in a second region 3 of the workpiece have been deflected and are essentially perpendicular, i.e. at an angle between 50° and 150°, in particular between 60° and 120°, to the fibers of the first region.

[0043] Due to the inhomogeneous alignment of the fibers or due to the turbulence of the fibers in the second region 3, the risk of crack formation is reduced by homogeneously aligned fiber alignment.

[0044] Fig. 3 shows the busbar according to Fig. 2 without the explanatory illustrations of fiber orientation and gate point 4. Reference symbol S1-S3 process steps 1 overmolded workpiece 2 first area 3 second area 4 Gate point 5 Turbulence induction point

Claims

[1] Method for processing a metallic workpiece comprising the following steps: - Providing (S1) a metallic workpiece; - tempering (S2), in particular heating, the workpiece to a predetermined temperature which depends on the processing temperature of the material; - Overmolding (S3) the tempered workpiece with a material, in particular with plastic. [2] Method according to claim 1, wherein the workpiece is designed as a busbar. [3] Method according to one of the preceding claims, wherein the material comprises fibers, in particular glass and / or carbon fibers. [4] Method according to claim 3, wherein at least one injection point is defined on the workpiece to be overmolded, at which material is injected into a mold, and at least one turbulence induction point is defined through which fluid is introduced into the mold, wherein the material flows in the mold in a first flow direction and the fluid flows in the mold in a second flow direction, wherein the flowing material and the flowing fluid cross each other. [5] Method according to claim 4, wherein the material and the fluid have an identical carrier, in particular are identical. [6] Method according to one of the preceding claims, wherein the workpiece is heated to a processing temperature of the material. [7] Method according to one of the preceding claims, wherein the workpiece is heated to a predetermined temperature such that the material and the workpiece undergo a material deformation during the cooling after overmolding to a reference temperature, wherein the material deformation of the material does not deviate from the material deformation of the workpiece by more than a predetermined amount. [8] A method according to any one of the preceding claims, wherein a busbar is provided with rounded edges or the edges of the busbar are rounded. [9] Busbar, in particular produced by means of a method according to one of the preceding claims, which is overmolded by a fibrous material, wherein at least in one region of the overmolded material fibers are aligned deviating from an injection direction.

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