DE102014217510A1 - Injection molding process for producing a fabric-reinforced injection-molded component - Google Patents

Abstract

Injection molding process for producing an injection-molded component (48) with tissue lying flat on one component side or flatly embedded in the component (48), the method comprising the steps of: - stabilizing a shape-unstable fabric piece (30) in accordance with a shape of a model wall region ( 22a), - inserting the dimensionally stabilized fabric piece (30) into an injection mold (29), - closing the injection mold (29), - injecting softened injection molding compound into the cavity (40) of the injection mold (29), - allowing the injection molding compound to cool down, Opening the injection mold (29) and - removing the injection molding component (48) from the injection mold (29).

Description

The present invention relates to an injection molding method for producing a fabric-reinforced injection-molded component, i. H. an injection-molded component with a surface lying on one side of the component or flatly embedded in the component tissue.

There is the technical problem that an inserted without further measures in a cavity of an injection mold formlabiles fabric is infiltrated upon entry of injection molding compound in the mold cavity under the process prevailing process injection pressures and entry velocities of the entering into the injection molding cavity injection molding and non-planar on the injection molded part thus produced but in an undefined compressed state.

By "planar" is meant that the fabric as the fabric layer usually extends in an extension plane and has dimensions therein, in relation to which the dimension in the material thickness direction of the fabric orthogonal to the extension plane or extension surface is often negligible. A fabric is a sheet of two thread systems crossed under one, preferably right, angle. A tissue laid out on a plane thus has two opposite outer surfaces separated only by the material thickness of the fabric. "Flat-fitting" and "surface-embedded" in the sense of the present application should therefore mean that one (adjacent) or both (embedded) outer fabric surfaces are wetted by unwanted overlapping folds of injection molding material, to which the fabric cohesively by adhesion or / and diffusion processes and / or positively connected by penetration of fabric meshes to the injection-molded component. Due to the curvature caused by forced deformation of an originally flat piece of tissue in a curved shape, occurring wrinkles are unavoidable and should be disregarded in the assessment of a flat concern or a flat embedding. By incorporating tissue into an injection-molded component, its strength properties, in particular tear resistance, can be considerably increased compared to an unreinforced injection-molded component.

For the reliable production of an injection-molded component with integrated tissue, a form-stable piece of tissue can firstly be provided.

According to the invention this formlabile fabric piece is dimensionally stabilized in accordance with a shape of a model wall area. In the simplest and most process-reliable case, this can be done by placing the fabric piece substantially flat on the pattern wall area without overlapping creases and assuming and overlapping the pattern wall complex and essentially adopting a positive shape of the pattern wall region. In this shape, the fabric piece can be dimensionally stabilized. The shape-stabilized piece of fabric does not change its shape under the weight of its own weight or only to a negligible degree. So it keeps its shape even after separation from the model wall section.

The step of shape stabilization can be carried out by applying an originally flowable, spreadable and / or spreadable curable stabilizing substance, in particular a liquid, paste or powder, particularly preferably an adhesive, to the fabric piece, placing the fabric piece on a forming member having the shape of the pattern wall portion and curing of the stabilizing substance. In this case, either the fabric piece can first be placed on a forming component having the shape of the model wall region and then the stabilizing substance can be applied or a fabric piece already provided with stabilizing substance can be applied to the shaping component with the shape of the pattern wall region.

The curing can be carried out by evaporation of solvents from the stabilizing substance, by crosslinking or by melting of stabilizing substance, in particular stabilizing substance particles and solidification or by merely solidifying a stabilizing substance applied as a melt.

In principle, therefore, the tissue piece can also be soaked or penetrated with the stabilizing substance prior to application, so that it is partially or completely penetrated by the stabilizing substance, in particular soaked through. Preferably, however, after application of the fabric piece, the stabilizing substance is applied to the pattern wall section, since with the application there is a spread of air bubbles possibly present between the fabric piece and the pattern wall region and / or a faithful abutment of the fabric piece on wall sections with a high curvature or / and small dimensions can be ensured.

The model wall region can basically be any wall region which can serve as a design specification for the later dimensionally stabilized fabric piece. The only condition that the model wall area has to fulfill is that the fabric piece stabilized thereby has room in the mold cavity of the closed injection mold for which the fabric piece is intended.

The shape stabilization by the above-mentioned thermosetting stabilizing substance can be stopped by curing the stabilizing substance, after which the hardened fabric piece provided with the stabilizing substance, in particular with adhesive, retains its shape given by the pattern wall area.

The model wall area can be realized on any model component that has been created, for example, only for the purpose of shape stabilization. This may therefore be equipped with a surface which does not form an adhesive bond with the stabilizing substance used for curing, so that the tissue piece can easily be lifted off the pattern wall area after curing of the stabilizing substance in a simple manner. The use of a specially created, separately formed from the injection molding tool model component with the model wall area allows parallelization of shape stabilization and urformendem injection molding in the strict sense.

The model wall region may be an image of a cavity wall region of a cavity of the injection mold used or may be the cavity wall region of the injection mold itself. In this case, a model with a model wall area can be saved. However, then the injection mold is not available during the shape stabilization of one or more pieces of fabric for the rest of the injection molding process. In this case, a plurality of fabric pieces can first be dimensionally stabilized with the injection mold or the tool part with the corresponding Kavitätswandabschnitt, wherein an injection molding machine can be prepared after completion of the preparatory form stabilization with the injection mold and then run an injection molding process with advantageously constant cycle time, in which the insertion of the dimensionally stabilized piece of fabric into the injection mold occupies a period of the cycle time.

In principle, the shape-stabilized piece of fabric is thus inserted into an injection mold, after which the injection mold is closed with the shape-stabilized fabric piece inserted therein.

Then, softened injection molding compound is injected into the cavity of the closed injection mold.

Due to the previously made shape stabilization of the fabric piece thereby omitting the otherwise to be feared shifting or / and folding of the fabric piece in the cavity. The fabric piece can therefore be dimensionally stabilized so that it can withstand the injection pressure. This is the case, in particular, when the cavity wall section has a three-dimensional structure with elevations and / or depressions, against which the shape-stabilized fabric piece can lie similar to a form fit. The choice of Anspritzortes can support the retention of a selected during insertion of the dimensionally stabilized piece of fabric in the injection mold positioning. This can be done, for example, by arranging the nozzle for entry of the injection molding compound opposite the shape-stabilized fabric piece inserted into the cavity and with respect to its extension surface in a central area, preferably on the side facing away from the cavity wall area against which the fabric piece rests. Preferably, the nozzle is oriented such that its injection axis, along which an injection of injection molding material takes place, with the surface of the fabric piece, which is incident on the injection axis, an angle of 70 ° -110 °, preferably 80 ° -100 °, more preferably of Includes 90 °.

According to an advantageous development of the present invention, the injection-molding compound can also be fed laterally into the cavity into which the shape-stabilized fabric piece is inserted.

It is likewise conceivable for the injection-molding compound-again preferably in a central region of the fabric piece-to first feed the fabric piece flowing through into the cavity of the injection mold. For this purpose, an opening can be provided in the fabric piece at the location of the feed, through which injection molding material flows during its feeding into the cavity.

After injection of the injection molding compound and sufficient filling of the cavity with the injection molding compound, the injection molding compound in the injection mold is allowed to cool sufficiently, as usual. Subsequently, the injection mold is opened and the injection molded component removed from the injection mold.

If the stabilization of form involves application of hardenable stabilizing substance to the piece of tissue - wherein impregnation of the tissue piece with the stabilizing substance should also be included in the term of applying curable substance to the piece of tissue in the context of the present application - then it is advantageous to use excess ablate applied stabilizing substance from the tissue piece. Thereby, a positive connection between the injection-molding compound and the dimensionally stabilized piece of fabric during injection molding can be improved, since the less the stabilizing substance is applied to the fabric piece, the stronger the stitch-forming fabric structure that is so advantageous for a positive connection. Excess stabilizing substance can lead to an undesirable smoothing of the tissue surface and, associated therewith, to a structure-reducing structural reduction of the tissue piece.

Advantageously, the excess hardenable stabilizing substance is removed by a gas flow, ie by blowing off. This has the advantage that the tissue structure is mechanically influenced as little as possible when removing excess stabilizing substance. Thus, a thread shift and associated unwanted local change of mesh sizes in the tissue can be avoided. According to an advantageous development, hot gas at a higher temperature than that of the ambient atmosphere is used for the blowing off in order to initiate a thermal curing of the stabilizing substance, which may be initiated depending on the stabilizing substance, already during the removal of stabilizing substance.

The person skilled in the art will, after reasonable tests, choose a temperature of the hot gas which, on the one hand, gives him sufficient time to remove excess stabilizing substance depending on the size and shape of the piece of fabric and, on the other hand, already supports the curing process.

Preferably, only sufficient stabilizer substance is applied to the fabric piece or so much excess stabilizer substance removed from the fabric piece after the step of applying stabilizer substance to the fabric piece or for the above-mentioned reasons of an improved positive connection of the injection molding compound with the dimensionally stabilized fabric piece after the step of removing excess stabilizing substance from the fabric piece, at least a plurality of fabric stitches, preferably a majority of the fabric stitches, more preferably at least 75% of the fabric stitches are so free of stabilizing substance that an opening of the fabric mesh bounded by fabric fibers of the fabric piece has a through opening from one side the fabric mesh is to the other side of the fabric mesh.

By exposing the fabric stitches described an enforcement of the mesh with injection molding compound is possible by the edges of the tissue fibers of the fabric piece openings of the respective fabric mesh allows passage of the injection molding compound through the dimensionally stabilized fabric piece in the thickness direction of the fabric piece.

Experiments have shown that suitable curable stabilizing substances can be water-based, ie water-containing, adhesives. These are environmentally friendly, easy to process, and in particular dilutable by adding appropriate amounts of water and thus adjusted as precisely as possible in their adhesion. It is possible to use adhesives with the addition of starch or / and cellulose.

For most efficient reinforcement of the injection molded component thus formed can be provided that the fabric piece glass fibers and / or carbon fibers and / or mineral fibers and / or natural fibers contains or is formed from such fibers. The piece of fabric may be a mixture of said fibers or may be formed solely from one of said fibers, the use of fabric pieces of glass fibers and fabric pieces of carbon fibers for reasons of process reliability in injection molding and due to the achievable gain values in the plastic component is preferred.

In order to be able to ensure positioning of the shape-stabilized piece of fabric in the cavity of the injection mold even at high injection pressures and / or with unfavorable injection directions relative to the position of the fabric piece, the injection molding method described here can be developed such that it comprises a step of fixing the shape-stabilized fabric piece in FIG the injection mold comprises.

The fixing can for example be done adhesively by adhesive. For example, the Kavitätswandbereich on which the shape-stabilized fabric piece is placed when inserted into the injection mold, or the support surface of the fabric piece are at least partially sprayed surface with a spray adhesive before the form-stabilized fabric component is placed. Alternatively, the shape-stabilized fabric component or / and the cavity wall portion of the injection mold can be provided with adhesive tapes, in particular double-sided adhesive tapes. Alternatively or additionally, it may be thought that the fixing takes place mechanically, for example by positive or / and frictional connection, by means provided in the injection mold fixing means. For example, such fixing means could be formed by projecting from a tool part of the injection mold mandrels, pins and / or needles that can protrude even with the injection mold closed in recesses of another tool part of the same injection mold. The said mandrels can enforce openings in the shape-stabilized fabric piece with closed injection mold, if necessary, these form when closing the injection mold by penetration, and thus fix the fabric piece. It can said openings in the shape-stabilized piece of fabric may be located in a region of the green component produced during injection molding, which is separated to form the later end component.

Similarly, areas, such as edge regions of the dimensionally stabilized piece of fabric by clamping means when closing the injection mold can be clamped engaged and thus fixed in position.

Finally, alternatively or additionally, the shape-stabilized piece of tissue can be fixed in position by means of vacuum nozzles.

The injection molding compound may be filled or unfilled. A filling can be done for example by glass fibers.

The method steps from insertion of the dimensionally stabilized piece of fabric until removal of the injection molded component from the injection mold in claim 1, optionally carrying out at least one further preferred intermediate step according to the above description can be repeated iteratively, in particular using different injection molds in each pass to an injection molding with to get complex shape.

The present invention will be explained in more detail with reference to the accompanying drawings. It shows:

1 three tissues with different bonds,

2 a rough schematic cross section through a model component with a model wall area,

3 the model component of 2 with a form-unstable piece of tissue placed on its model wall area,

4 an application of flowable hardenable stabilizing substance to the formlabile fabric piece,

5 a blow-off of excess applied stabilizing substance from the fabric piece and a hardening of the stabilizing substance,

6 a removal of the shape-stabilized fabric piece from the model wall area of the model component,

7 placing the shape-stabilized piece of fabric on a cavity wall region of a cavity of a mold part of an injection mold,

8th the closed injection mold with the tool part of 7 .

9 the injection mold of 8th in cross-section filled with injection molding cavity and

10 the injection mold of 9 after opening, with indicated removal of the injection molded component produced.

All representations of the 2 to 10 FIG. 10 is a rough schematic cross-sectional view to illustrate the operation of the method described herein. FIG. In 1 various tissue configurations are shown, all of which are suitable for use in the method of the present application. The presentation of the 1 is not exhaustive. Therefore, other tissue designs can also be used.

The tissues of the 1a.) to 1c.) is, like all tissues, common that they are a plane of two at an angle, here: a right angle, crossed thread systems. The gray colored threads of the fabric of the 1a.) to 1c.) are warp threads. The white dyed threads are weft threads.

In the production of the fabrics on a loom, the weft threads are crossed with the warp threads to a binding. This is how the fabrics differ 1a.) to 1c.) by the bond produced between weft and warp threads.

In the bonds of the individual tissues of the 1a.) to 1c.) is it in 1a.) a so-called "satin weave", in 1b.) to a so-called "body bond" and in 1c.) around a so-called "plain weave".

The plane defined by the directional vectors of the crossed thread systems of a fabric is in the present application the plane of extent of the fabric.

Between two weft threads immediately adjacent in the warp direction 10 and 12 as well as between two warp threads immediately adjacent in the weft direction 14 and 16 can through the four threads mentioned a stitch 18 be formed, which can form a passage from one outer side of the fabric to the opposite other outer side.

In 2 is a rough schematic cross section of a model component 20 shown what a structural training 22 has, the outer wall 22a as a model wall area for a shape stabilization of an originally form-labile piece of fabric should serve. The model wall area 22a is a cavity wall area 24a (please refer 7 ) of a cavity wall 26 a tool part 28 an injection mold 29 (please refer 8th ) in the scale 1: 1.

The model wall area 22a of the model component 20 may be suitably coated to avoid an adhesive reaction with a hardenable stabilizing substance described below, for example in the form of a liquid adhesive, which is preferably used for shape stabilization of a fabric.

In 3 is the model component 20 with one on the model wall area 22a launched form-labile piece of fabric 30 shown. The fabric piece 30 is preferably formed from glass fibers and / or carbon fibers. Depending on the stiffness of the fabric piece 30 This hugs itself by gravity to the model wall area 22a at.

In the present example is as the model wall area 22a carrying structural education 22 exclusively chosen a survey structure. Additionally or alternatively, the model wall area 22a also be realized as a depression or include such.

In 4 is shown as on the formlabile tissue piece 30 an adhesive is applied as an example of the settable stabilizing substance to the fabric piece 30 stabilize in its shape, which it by pad on and attachment to the model wall area 22a had received. For this purpose, an adhesive applicator, such as a spray nozzle 32 or an in 4 unillustrated brush, over the surface facing away from the model wall area surface 30a emotional. In doing so, the spray nozzle 32 adhesive 34 as a spray on the surface 30a of the piece of tissue 30 Instruct. The spray nozzle 32 can do this relative to the fabric piece 30 be moved to all free surface sections of the surface 30a to supply with adhesive.

In 5 is a combined blow-off and drying process of the adhesive-coated fabric piece 30 shown. This is exemplified by a hot gas nozzle 36 used, which is a hot gas stream, in particular hot air stream 38 , to the exposed surface 30a of the piece of tissue 30 blows, on the one hand, excess adhesive from the fabric piece 30 to blow and on the other a thermal drying to cure the adhesive provided with tissue piece 30 to support. Therefore, the hot gas flow has 38 preferably a relative to the temperature of the ambient atmosphere elevated temperature.

Preferably, so much glue from the fabric piece 30 blown off again that the in 1 recognizable stitches 18 mostly, preferably 75% or more freely and as a passage opening from the side 30a of the fabric piece to that at the model wall area 22a resting support side 30b usable available.

Alternatively or additionally, a drying and thus a curing of the adhesive for shape stabilization of the fabric piece 30 by radiant heat sources such as infrared lamps and the like.

6 shows how the cured shape-stabilized piece of fabric 30 from the the model wall area 22a having structure 22 of the model component 20 lifted and provided for further use in the injection molding process discussed herein.

In 7 is logically shown as the shape-stabilized piece of fabric 30 to the cavity wall section 24a applied or on a Kavitätswandabschnitt having structure 24 of the injection mold part 28 is hung up.

The cavity wall section 24a or / and the page attached to this page 30b of the piece of tissue 30 may be provided with adhesive, such as spray adhesive or double-sided adhesive tape, or with mechanical fixatives, such as needles, mandrels and pins, or / and pneumatic fasteners, such as vacuum cans, to provide position fixation of the fabric piece 30 at the cavity wall section 24a to improve.

In 8th is the injection mold 29 closed, with the formation of a cavity 40 between the cavity wall section 24a having tool part 28 and another injection mold part 42 ,

The shape-stabilized fabric piece 30 it rests in the cavity 40 on the structure 24 and is located on the Kavitätswandabschnitt 24a which preferably has the same shape as the model wall area 22a of the model component 20 is.

The injection mold 29 can be more than merely illustrative in the 8th to 10 shown two tool parts 28 and 42 exhibit.

The positioning of the shape-stabilized fabric piece 30 in the cavity 40 at the cavity wall section 24a during injection of injection molding compound into the cavity 40 can still be supported by the fact that the injection axis E of the feeder 44 with injection nozzle is arranged and oriented so that they relate to the fabric piece 30 in a central area 46 on the exposed surface 30a impinges, if possible at a right angle or in an angle of this preferably by not more than 20 ° deviating angle.

In 9 are complementary to 8th alternative injection situations for filling with a dimensionally stabilized piece of tissue 30 partially occupied cavity 40 shown with injection molding compound.

Alternative to the feeder 44 , which centrally from above on the fabric piece 30 Injection molding compound into the cavity 40 can feed with a side feeder 44 ' Injection molding compound laterally into the cavity 40 be fed.

Further alternatively or additionally, by a feeder 44 '' in the tool part 28 Injection molding compound even from below into the cavity 40 be fed. Thus, during the injection of injection molding compound through the feeder 44 '' the dimensionally stable tissue part 30 not undesirable from the tool part 28 or more precisely from the cavity wall section 24a is lifted, is preferred when using a feeder 44 '' in the tool part 28 the shape-stabilized fabric part 30 at the entry point with an opening 45 provided, which in 9 indicated by dotted line. Thus, from the feeder 44 '' into the cavity 40 fed injection molding compound through the opening 45 pass through and between the tissue piece 30 and the tool part 42 located portion of the cavity 40 fill with injection molding compound.

In 9 is the state of 8th after injecting injection molding compound into the cavity 40 shown. Thus, an injection molding shell was 48 receive. The injection molding compound wets the shape-stabilized fabric piece 30 on its previously exposed surface 30a and binds this by positive engagement of the injection molding compound by the injection molding compound in the mesh of the dimensionally stabilized fabric piece 30 penetrates, flows through and engages behind and thus a firm connection between injection molding compound and dimensionally stabilized fabric piece 30 creates.

In 9 the case of an injection-molded component is shown with tissue lying flat on one side of the component.

Due to the injection pressure, the previously shape-stabilized fabric piece 30 be slightly compressed in the material thickness direction.

In 10 is the removal of the injection molding raw component 48 from the opened injection mold 29 roughly sketched.

The injection molding shell component 48 can now be inserted into another injection mold in which possibly the still exposed side 30b of the piece of tissue 30 is covered with injection molding compound. So that from the injection molding raw component 48 an injection molded component with embedded tissue can be produced.

Claims (10)

Injection molding process for producing an injection-molded component ( 48 ) with surface on one component side adjacent or flat in the component ( 48 ) embedded tissue, the method comprising the following steps: - stabilizing the shape of an originally form-unstable piece of tissue ( 30 ) according to a shape of a model wall area ( 22a ), - inserting the shape-stabilized piece of fabric ( 30 ) in an injection mold ( 29 ), - closing the injection mold ( 29 ), Injection of softened injection molding compound into the cavity ( 40 ) of the injection mold ( 29 ), - allowing the injection molding compound to cool down, - opening the injection mold ( 29 ) and - removal of the injection-molded component ( 48 ) from the injection mold ( 29 ). Injection molding method according to claim 1, characterized in that the step of stabilizing the shape comprises applying a curable stabilizing substance originally capable of flow, spread or scatter ( 34 ), in particular a liquid, paste or powder, on the piece of fabric ( 30 ), placing the tissue piece ( 30 ) to a forming component ( 20 . 28 ) with the shape of the model wall area ( 22a ) and hardening of the stabilizing substance ( 34 ). Injection molding method according to claim 1 or 2, characterized in that the model wall area ( 22a ) an image of a Kavitätswandbereichs ( 24a ) of a cavity ( 40 ) an injection mold ( 29 ) or the cavity wall area ( 24a ) of the injection mold ( 29 ) itself, the injection mold ( 29 ) a tool part ( 28 ) with the cavity wall area ( 24a ) and the shape-stabilized fabric piece ( 30 ) during the step of its insertion into the injection mold ( 29 ) on the cavity wall area ( 24a ) is launched. Injection molding method according to claim 2 or claims 2 and 3, characterized in that the step of stabilizing the shape after the application of the stabilizing substance ( 34 ) on the piece of fabric ( 30 ) removal of excess stabilizing substance ( 34 ), wherein the removal preferably a blow-off, particularly preferably a blow-off with hot gas ( 38 ) at a higher temperature than that of the ambient atmosphere. Injection molding method according to one of claims 2 to 4, including claim 2, characterized in that after the step of applying the stabilizing substance ( 34 ) on the piece of fabric ( 30 ) or after the step of removing excess stabilizing substance ( 34 ) of the fabric piece ( 30 ) at least a plurality of tissue stitches ( 18 ), preferably a majority of the tissue stitches ( 18 ), more preferably at least 75% of the fabric meshes ( 18 ) so free of stabilizing substance ( 34 ) are one of tissue fibers ( 10 . 12 . 14 . 16 ) of the tissue piece ( 30 ) bounded opening of the fabric mesh ( 18 ) a passage opening from one side ( 30a ) of the tissue mesh ( 18 ) to the other side ( 30b ) of the tissue mesh ( 18 ). Injection molding method according to one of claims 2 to 5, including claim 2, characterized in that the stabilizing substance ( 34 ) Contains water. Injection molding method according to one of the preceding claims, characterized in that the piece of fabric ( 30 ) Glass fibers and / or carbon fibers and / or mineral fibers and / or natural fibers contains or is formed from such fibers. Injection molding method according to one of the preceding claims, characterized in that it comprises a step of fixing the shape-stabilized fabric piece ( 30 ) in the injection mold ( 29 ). Injection molding method according to claim 8, characterized in that the adhesive fixing by adhesive, such as a double-sided adhesive takes place. Injection molding method according to claim 8 or 9, characterized in that the fixing mechanically, such as by form and / or adhesion, by in the injection mold ( 29 ) provided mechanical fixing means, such as mandrels, needles or pins, takes place, or / and that the fixing pneumatically, for example by in the injection mold ( 29 ) provided vacuum nozzles takes place.

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