WO2023156199A1

WO2023156199A1 - Injection molded component and injection molding method

Info

Publication number: WO2023156199A1
Application number: PCT/EP2023/052418
Authority: WO
Inventors: Thomas Willerer; Henri Joel NDANGA NGEUMBOU; Burkhard Reinsch
Original assignee: Webasto SE
Priority date: 2022-02-15
Filing date: 2023-02-01
Publication date: 2023-08-24
Also published as: DE102022103497A1

Abstract

The invention relates to an injection molded component (10) which has a first region (12) with a base wall thickness (20), a second region (14) with a wall thickness which is increased in comparison to the base wall thickness (20), and an injection point (18) in the first region (12). According to the invention, a connection region (16) with a likewise increased wall thickness (28) is arranged on the first region (12) starting from the injection point (18), said connection region running from the first region (12) to the second region (14). In a method according to the invention, a holding-pressure channel is provided in the surface of the cavity at a first section of the cavity, for forming the first region (12), so as to run from an injection point (18) to a second section of the cavity, for forming the second region (14), wherein the cross-section of the holding-pressure channel is dimensioned such that a material shrinkage in the second region (14) of the injection molded component (10) is compensated for and/or a warpage of the injection molded component (10) is reduced.

Description

Injection molded component and method for injection molding

The present invention relates to an injection molded component according to the preamble of claim 1 and a method for injection molding an injection molded component according to the preamble of claim 6.

A generic injection molded component has a first area with a base wall thickness, a second area with a wall thickness that is greater than the base wall thickness, and an injection point in the first area. A gate is a portion where material is injected into a cavity of a mold to produce the molded part. Such an injection point remains visible on the injection-molded component after the injection-molded component has been removed from FIG.

A generic injection molded component can be, for example, a frame part for the frame of a sunroof for a vehicle.

In order to save material and weight, injection molded components are designed with the smallest possible wall thickness. However, it is often necessary to make this wall thickness thicker at specified points due to other functional requirements. Such points can be critical areas that have to be stable, such as screw domes for assembling the injection-molded component at an installation location.

Various problems arise when injection molding known injection molded components. When injecting a liquid or foam-like plastic material to produce the injection-molded component from such a plastic, the plastic is injected at a specified injection pressure into a cavity of a mold. Ideally, the plastic only solidifies when this cavity is completely filled. In fact, shrinking processes already take place during the injection or afterwards, which can lead to cavities (so-called vacuoles). Furthermore, the injected plastic can also already solidify before it has filled all areas of the cavity, in particular also the areas with increased wall thickness. Such cavities within the injection-molded component can result in the injection-molded component being incomplete. Increased component distortion can also occur.

To counteract this, an increased injection pressure can be selected in order to mitigate at least some of the error patterns. However, as a result of high injection pressures, there are also high shear loads in the plastic material, which can lead to damage, increased emission values and poorer odors in the finished part.

Several corrections to the cavity are often required, for example to compensate for any component distortion using a tool geometry that deviates from the desired component geometry (provision). Furthermore, the base wall thickness cannot be further reduced in order to save material or reduce distortion, since otherwise functional geometries such as screw bosses cannot be adequately supplied with material.

It is therefore the object of the present invention to provide an injection molded component and a method for injection molding such an injection molded component in which these problems do not occur.

This object is achieved by an injection molded component according to the characterizing part of claim 1 and by a method according to the characterizing part of claim 6.

In an injection-molded component according to the invention, starting from the injection point, a connection area with a likewise increased wall thickness is arranged on the first area, which runs from the first area to the second area.

In the method according to claim 6 according to the invention, a post-pressure channel is provided in a surface of the cavity at a first section of the cavity to form the first area away from an injection point to a second section of the cavity to form the second area. The cross section of the post-pressure channel is dimensioned in such a way that material shrinkage in the second region of the injection-molded component is compensated for and/or distortion of the injection-molded component is reduced. During production of the injection-molded component, the post-pressure channel of the method according to the invention forms the connection area of the injection-molded component, which also has an increased wall thickness and runs from the first area with the base wall thickness to the second area with the increased wall thickness.

An injection molded component according to the invention and the method according to the invention offer the advantage that material shrinkage from the injection point to the area with increased wall thickness can be compensated for in a so-called holding pressure phase until the injection molded component has completely solidified. Advantageously, the geometry of the post-pressure channel, in particular its cross section, can thus be adjusted as a function of a length of a flow path of the material and the base wall thickness. The possible length of the flow path also influences the base wall thickness. In the case of components of a sunroof for a vehicle such as frame parts, engine mounts, guide rails, housing elements and other larger components, the required flow path length can be up to 400 mm. Depending on an injection pressure and a desired flow path length, it can thus be determined which post-pressure channel width and post-pressure channel height must be provided in order to be able to reliably implement a specific base wall thickness.

Such post-pressure channels according to the invention and the connection areas that form such post-pressure channels only slightly increase the material requirements and the weight of the injection-molded component. The base wall thickness can be further reduced compared to known methods for producing injection molded components and the filling of the cavity and the compensation for the material shrinkage can also be ensured in the areas with increased wall thickness. Component distortion can also be reduced. The reduction in the use of material achieved in this way, which is made possible by the connection areas or post-pressure channels according to the invention, leads to a reduction in the production costs. Required emission and odor values can be reliably met.

Advantageous configurations of the invention result from the dependent claims. Advantageously, the injection-molded component has a wall thickness in the connection area that is greater than the base wall thickness.

In the area of the injection point, the injection-molded component can have a wall thickness that is also greater than the base wall thickness.

The injection molded component is preferably made of a plastic and has a base wall thickness of 1 mm to 3 mm, and an increase in the wall thickness in the connection area by 0.2 mm to 1 mm, preferably by 0.4 mm to 0.8 mm.

In a preferred embodiment, the connection area has a length of 50 mm to 400 mm. This allows the flow path lengths of components such as frame components, engine mounts, guide rails, housing elements and other larger components of sunroofs to be covered.

The post-pressure channel is preferably designed as a groove-shaped depression in the surface of the cavity of the injection molding tool.

A cross section of the post-pressure channel is more preferably dimensioned depending on one or more of the following factors: the injection pressure with which the plastic is injected into the cavity, the length of the post-pressure channel, the base wall thickness, the plastic material, the flow path length of the plastic material.

In a preferred embodiment of the inventive method, the post-pressure channel is designed as a groove-shaped depression in the surface of the cavity of the injection molding tool.

The post-pressure channel preferably has a depth of 0.2 mm to 1 mm, preferably 0.4 mm to 0.8 mm. More preferably, the post-pressure channel has a width of 4 mm to 12 mm, preferably 5 mm to 8 mm.

A method in which an injection-molded component according to the invention is formed is particularly preferred, with the post-pressure channel forming the connection area.

The invention is explained in more detail below by way of example with reference to the attached figures.

It shows:

1 shows a perspective view of an injection-molded component according to the invention;

Fig. 2 shows a cross section through a connection area of the

injection-molded component of FIG. 1 ; and

3 shows flow path lengths of an injection molding material as a function of base wall thickness for four different injection pressures.

Figures 1 and 2 show an injection molded component 10 according to the invention in a perspective view from above and in cross section through a connection area 16.

The injection molded component 10 has a first region 12 with a base wall thickness

20 and various second areas 14 with an increased wall thickness 28.

One of the second areas 14 forms a screw dome 26 for fastening the injection-molded component 10. The injection-molded component 10 is reinforced in the area around the screw dome 26 due to the increased wall thickness 28. The injection-molded component 10 is part of a sliding roof, in particular a frame for such a sliding roof, and the injection-molded component 10 can be arranged fixed to the body of a vehicle by means of the screw boss 26 . Due to the fact that the injection-molded component 10 has an increased wall thickness 28 in the second area 14, the screw boss 26 can withstand greater forces record than would be the case if the complete injection molded component 10 were running with the base wall thickness 20.

An injection point 18 is also present on the injection-molded component 10 , which results from the fact that a plastic material for forming the injection-molded component 10 was injected into a corresponding cavity of a mold in this area during the injection molding of the injection-molded component 10 . This injection point 18, which is arranged in the first region 12 with the base wall thickness 20, is connected to the second regions 14 of increased wall thickness 28 of the injection-molded component 10 by a plurality of connection regions 16. Each connecting area 16 extends along the surface of the injection-molded component 10 in the form of a strip on a direct path away from the injection point 18 to the associated second area 14 with an increased wall thickness 28 .

Fig. 2 shows a cross section through the injection-molded component 10 of Fig. 1 and through one of the connection areas 16. As can be seen here, the connection area 16 is also an area with an increased wall thickness compared to the base wall thickness 20, as is already the case with the second Area 14, which forms the screw boss 26, is the case. In the embodiment of FIGS. 1 and 2, the wall thickness in the connection area 16 has the same dimensions as the increased wall thickness 28 in the second area 14 of the injection-molded component 10, which forms the screw dome 26. However, this does not always have to be the case. Accordingly, the wall thickness in the connection area 16 can be greater or less than the increased wall thickness 28 in the second area 14, but it is always greater than the base wall thickness 20 in the first area.

The connecting area 16, which is formed by a post-pressure channel in the mold, ensures that during the injection molding of the injection-molded component 10 there is a sufficient supply of material for forming the second area 14 with an increased wall thickness 28.

To form the connection area 16 is in a non-illustrated cavity of such a mold for forming the injection molded component 10 in a Provided surface of this cavity of the Nachdruckkanal through which additional material can flow in the direction of the second region 14 to fill it completely and thereby compensate for a material shrinkage. Therefore, in a method according to the invention for injection molding of the injection-molded component 10, a corresponding post-pressure channel in a surface of the cavity extends from a first section of the cavity to form the first area 12 away from the injection point 18 to a second section of the cavity to form the second area 14.

A cross section of the post-pressure channel and thus a cross section of the connection area 16 formed by it can be dimensioned such that the material shrinkage of the second area 14 of the injection molded component 10 is compensated and/or distortion of the injection molded component 10 is reduced.

A post-pressure channel height 24 corresponds to a height of the connection area 16 on the injection-molded component 10, with which the base wall thickness 20 is reinforced. Overall, the connecting area 16 has the thickness of the base wall thickness 20 plus the post-pressure channel height 24 .

The size of the corresponding post-pressure channels depends on the length of the flow path of the injected material during production of the injection-molded component 10 and on the base wall thickness 20.

3 shows a matrix representation for measured flow path lengths as a function of the base wall thickness of an injection molded component for a plastic material (Kingfa GFPP-40). The flow path lengths are shown as four different curves for four different injection pressures of 75, 110, 145 and 180 MPa. Flow path lengths of frame parts, motor mounts and other larger components for a sunroof can be up to 400 mm. As can be seen from FIG. 3, with the plastic used here at a pressure of, for example, 110 MPa (second curve from the bottom) with such a flow path length of 400 mm, a basic wall thickness of approx. 1.6 mm can be guaranteed. For frame components, there are typical dimensions for a width of post-pressure channels of 6 mm and a depth of 0.4 mm for a GFPP-40 material and a base wall thickness of 2 mm. These dimensions can be determined and optimized in corresponding test series.

Reference List

10 injection molded part

12 first area

14 second area

16 connection area

18 injection point

20 base wall thickness

24 Downstream Channel Elevation

26 screw dome

28 increased wall thickness

Claims

Expectations

1. Injection molded component (10), which has a first area (12) with a base wall thickness (20), a second area (14) with a wall thickness that is greater than the base wall thickness (20), and an injection point (18) in the first area (12 ), characterized in that starting from the injection point (18) on the first area (12) there is a connection area (16) with a likewise increased wall thickness (28) which runs from the first area (12) to the second area (14).

2. Injection molded component (10) according to claim 1, characterized in that the injection molded component (10) in the connection region (16) has a wall thickness which is greater than the base wall thickness (20).

3. Injection molded component (10) according to one of the preceding claims, characterized in that the injection molded component (10) in the region of the injection point (18) has a wall thickness which is greater than the base wall thickness (20).

4. Injection molded component (10) according to one of the preceding claims, characterized in that the injection molded component (10) consists of a plastic and has a base wall thickness (20) of 1 mm to 3 mm, and an increase in the wall thickness in the connection area (16) by 0.2 mm to 1 mm, preferably around 0.4 mm to 0.8 mm.

5. Injection molded component (10) according to one of the preceding claims, characterized in that the connecting region (16) has a length of 50 mm to 400 mm.

6. Method for injection molding an injection molded component (10), wherein in the course of the method a plastic is injected into a cavity of an injection mold, and the cavity is designed such that the plastic component has a first region (12) with a base wall thickness (20) and a second area (14) with a wall thickness that is greater than the base wall thickness (20), characterized in that in a surface of the cavity at a first section of the cavity to form the first area (12) from an injection point (18) away to a second A post-pressure channel is provided in the section of the cavity for forming the second area (14), with a cross-section of the post-pressure channel being dimensioned in such a way that material shrinkage in the second area (14) of the injection-molded component (10) is compensated for and/or distortion of the injection-molded component (10 ) is reduced.

7. The method according to claim 6, characterized in that the post-pressure channel is designed as a groove-shaped depression in the surface of the cavity of the injection molding tool.

8. The method according to claim 6 or 7, characterized in that the cross section of the post-pressure channel is dimensioned depending on one or more of the following factors: an injection pressure with which the plastic is injected into the cavity, a length of the post-pressure channel, the base wall thickness ( 20), the plastic material, a flow path length of the plastic material.

9. The method according to any one of claims 6 to 8, characterized in that the post-pressure channel is designed as a groove-shaped depression in the surface of the cavity of the injection mold.

10. The method according to any one of claims 6 to 9, characterized in that the post-pressure channel has a depth of 0.2 mm to 1 mm, preferably 0.4 mm to 0.8 mm.

11. The method according to any one of claims 6 to 10, characterized in that the post-pressure channel has a width of 4 mm to 12 mm, preferably 5 mm to 8 mm.

12. The method according to any one of claims 6 to 11, characterized in that by means of the method an injection molded component (10) is formed according to any one of claims 1 to 5, wherein the post-pressure channel forms the connection area (16).