DE102015211634A1 - Injection molded part and method for producing an injection molded part - Google Patents

Abstract

Embodiments relate to an injection molded part (1), which comprises an injection-molded material, with a component interior (2) and an edge region (3). The edge region (3) is arranged between a surface of the injection-molded part (1) and the component interior (2). In the edge region (3) are arranged crystallization cores (5), which differ from the injection molding material.

Description

Embodiments relate to an injection molded part and a method for producing an injection molded part.

Injection molded parts are used in a variety of applications. For example, one such application may be as a component that slides or unrolls with its surface on another surface. In such applications, the properties of the surface or its coefficient of friction are important.

In order to produce components or products for tribological applications, thermoplastics, for example semi-crystalline thermoplastics are often processed by injection molding. Such components may be, for example, gears, plain bearings or the like. When producing a component in an injection molding process, it is often the case that a spray skin is produced on a surface of the injection molded part, possibly for economic reasons, as a result of short injection molding cycles. The spray skin may be, for example, an amorphous edge region of the injection-molded part. In most cases, the edge region or the spray skin has tribologically inferior properties than a core of the injection-molded part, which can be, for example, partially crystalline.

Under unfavorable circumstances, the amorphous shape of the edge region or of the sprayed skin can lead to impaired wear and / or friction properties of the injection-molded part during an operation and / or a running-in phase. Possibly under unfavorable circumstances also a reduced service life of the injection molded part result, since it can offer only a limited stock of wear. This is undesirable.

In some conventional manufacturing processes for injection molded parts, an attempt is made to influence a property of the edge region or of the sprayed skin by process parameters. The sprayed skin can be influenced and minimized by process parameters such as, for example, a temperature of a tool and / or an injection molding compound. However, optimizing the process parameters for minimizing the spray skin can result in a significant lengthening of cycle times. Therefore, a spray skin is often accepted in favor of product costs and shorter cycle times.

There is therefore a need to improve injection molded parts and their production so that their surface is better suited for tribological applications. The injection molding parts or the method according to the independent claims take this demand into account.

Embodiments relate to an injection molded part comprising an injection molding material. The injection-molded part has a component inside and an edge region surrounding the component interior. The edge region is arranged between a surface of the injection-molded part and the component interior. The edge region comprises crystallization cores whose material differs from the injection-molded material. In some embodiments, by virtue of the edge region having the crystallization cores, it is possible for the edge region, which can also be referred to as a spray skin, to form with better tribological properties. This may be possible, for example, because the crystallization cores, which may also be referred to as nuclei, initiate crystallization of the injection molding material in the edge region, which results in the edge region being less amorphous than without the use of the crystallization cores. This can for example be done without or with only a minor influence on a cycle time in the production of the injection molded part.

In some embodiments, the edge region may have a degree of crystallization that corresponds to a degree of crystallinity of the component interior, is comparable to this, or at most by a value of 5%, 10%, 20%, 30%. 50%, 60% deviates from a degree of crystallization of the component interior.

An injection molded part may be, for example, any component or component to be manufactured in an injection molding process. As injection molding material, for example, all sorts of plastics, thermosetting plastics, elastomers, thermoplastics, for example semicrystalline thermoplastics, polyoxymethylene (POM), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET) and / or the like can be used.

The component interior may be, for example, a core of the injection-molded part, which is constructed homogeneously from the injection-molded material. The component interior can be completely or at least partially surrounded by the edge region. The edge region can be arranged, for example, between a surface of the injection-molded part and the component interior. The edge region may under certain circumstances have a thickness which corresponds to a maximum of 10%, 5%, 2%, 1%, 0.5% of a diameter of the injection-molded part. The edge region may possibly have a thickness that corresponds to at least 10%, 5%, 2%, 1%, 0.5% of a diameter of the injection-molded part. The edge region can be a region of the injection-molded part which, during production, is in contact with a surface of an injection-molding tool.

A crystallization core may be, for example, a component that improves a crystallization behavior of a melt, for example an injection molding material. In some embodiments, the nuclei may be present exclusively in the edge region. Thus dust grains or contaminations, air inclusions or other irregularities which may occur during injection molding part production in the injection molded part or on its surface, for example not as crystallization cores of the exemplary embodiments, are or are used. Under certain circumstances, the crystallization cores can also be arranged in the component interior. Then, the nuclei may be present in the peripheral region in a higher or equal concentration than in the interior of the device.

In addition, a crystallization core as a material coal, for example on pitch base (PAN), glass, aramid, copper and / or PTFE have. For example, the nuclei may be, for example, a fiber, such as a carbon fiber, such as pitch based (PAN), a glass fiber, an aramid fiber, a copper particle, PTFE, nanoparticles, and / or core-shell particles. For example, a fiber may be any member that has a linear expansion that is, for example, at least a factor of 10, 20, 30, 40, 50, 80, 100, 200, 500, 1000 greater than a diameter of the component. A particle may have side lengths of similar lengths, for example, over the fiber.

Additionally or alternatively, the crystallization core may have a length which is at least 0.0001 mm and a maximum of 0.5 mm. A length of the crystallization core can be, for example, its largest dimension. Additionally or alternatively, the crystallization core may have a thickness which is at least 0.0001 mm and a maximum of 0.5 mm. A thickness of the crystallization core may be, for example, an extension that is arranged transversely to its length. Additionally or alternatively, a maximum extent of the crystallization core may have at least 0.001%, 0.01%, 0.1% or 0.5% and / or at most 0.001%, 0.01%, 0.1%, 0.5%, 1% of an expansion of the injection-molded part. In some embodiments, a particularly good crystallization behavior can be achieved by the mentioned geometries.

Additionally or alternatively, at least a part of the crystallization cores can be arranged along a main extent perpendicular to the surface of the injection-molded part. In some embodiments, it may thus be possible for the crystallization cores to have a good crystallization capability and still to have a sufficient proportion of a surface of the injection-molded part that the injection-molding material has. Under certain circumstances, all nuclei can have this orientation relative to the surface of the injection-molded part. Eventually, only a part, for example at least 5%, 10%, 20%, 50%, 60%, 70%, 80%, 90%, 98%, 99% of the crystallization core may have the described orientation to the surface.

Optionally, two directly adjacent crystallization cores may have a distance from one another which corresponds to at least a factor 0.5, 1, 2, 3, 4, 5, 10 of a thickness of the crystallization core. In some embodiments, the crystallization cores may form the surface of the injection molded part and / or be covered with the injection molding material.

Additionally or alternatively, the edge region may have further additives. These additives may, for example, be materials which reduce a coefficient of friction of the surface or improve a sliding behavior. These materials may be, for example, plastic, nanoparticles, PTFE and / or similar, a sliding behavior-improving materials.

Additionally or alternatively, the injection molded part may be a gear, a gear element, a sliding bearing, a sliding bearing element, a bearing cage, a bearing cage element, a worm drive, a shaft or other tribologically stressed plastic components, wherein the crystallization cores, which may also be referred to as crystallization particles, at least are arranged in the region of a tribologically stressed surface. In some embodiments, tribologically stressed surfaces with particularly good sliding properties can be produced in these components. Optionally, the nuclei may be arranged only or at least in a higher concentration in areas of the edge region, which is later tribologically stressed, for example as a sliding and / or rolling surface, tooth flank or the like. Alternatively, the crystallization core can be provided in the entire edge region.

Embodiments also relate to a method for producing an injection molded part. In the method, an injection mold is provided. Subsequently, nuclei are applied to a surface of the injection mold. Then an injection molding material is introduced into the injection mold. In some embodiments, the fact that the injection mold is prepared before being filled with the injection molding material with nuclei, the formation of a spray skin can be reduced. In some circumstances, an injection molded part having a less amorphous surface and a higher degree of crystallization getting produced. In some embodiments, therefore, a method for increasing a tribological performance of injection molded, thermoplastic plastic components can be provided.

The application of the crystallization cores to a surface of the injection mold can be done for example by applying, for example with a brush or other tool, a dipping of the mold, spraying, spraying or the like.

The method may additionally include, for example, aligning the crystallization cores. In this case, the crystallization cores can be aligned, for example, so that they protrude along the main extent of the surface of the injection mold. In some embodiments, the largest possible part of the surface of the injection-molded part may include the injection-molding material. In some embodiments, the crystallization cores may be arranged along their main extent, that is, for example, with their length and / or greatest extent perpendicular to the surface of the injection mold and thus also to the surface of the later component. In the later injection-molded part, the crystallization cores may, for example, be completely and / or flush-recessed.

For example, the crystallization cores and / or the injection mold can be polarized to achieve the described orientation. In some embodiments, it can thus be made possible for the nuclei to arrange themselves. Additionally or alternatively, the crystallization cores and / or the injection mold may be statically charged to achieve alignment perpendicular to the surface of the injection mold.

Optionally, the nuclei and / or the injection mold may be exposed to an electrical, a magnetic, an electromagnetic field to achieve polarization and / or static charge. This can be done, for example, before the crystallization cores are applied in the injection mold or its surface or even after the application of the crystallization cores to the injection mold. Optionally, the alignment of the crystallization cores can also take place before or after the introduction of the injection-molding material into the injection mold.

The embodiments disclosed in the foregoing description, the appended claims and the appended figures, as well as their individual features, may be relevant and implemented both individually and in any combination for the realization of an embodiment in its various forms.

Thus, the figures show schematically the following views.

1 shows a schematic cross-sectional view of an injection molded part according to an embodiment;

2 shows a schematic representation of a sequence program of a method for producing an injection molded part according to an embodiment;

3 shows a schematic representation of an injection mold in the manufacture of an injection molded part according to an embodiment.

In the following description of the accompanying drawings, like reference characters designate like or similar components. Further, summary reference numbers are used for components and objects that occur multiple times in one embodiment or in one representation, but are described together in terms of one or more features. Components or objects which are described by the same or by the same reference numerals may be the same, but possibly also different, in terms of individual, several or all features, for example their dimensions, unless otherwise explicitly or implicitly stated in the description.

1 shows a schematic cross-sectional view of a section of an injection molded part 1 according to an embodiment. The injection molded part 1 is a gear. In the 1 a tooth is recognizable. The injection molded part 1 includes a component inside 2 , The component inside 2 is completely from a border area 3 surround. The border area 3 is between a surface 4 of the injection molded part 1 and the component interior 2 arranged. In the border area 2 are a plurality of nuclei 5 arranged, differing from an injection molding material of the injection molded part 1 differ.

In the embodiment of the 1 are the nuclei of crystallization 5 only in the border area 3 arranged and have a length which is in the range of a conventional spray skin thickness, for example in a range of up to 0.5 mm. A length of a nucleus of crystallization 5 For example, the injection molding material, which may also be referred to as the substrate material, may be dependent on a component geometry and / or injection process parameters. The nuclei 5 , which may also be referred to as particles or tribologically active particles, may have a size which in a defined ratio to a component size of the injection-molded part 1 lies. The ratio may be, for example, 1/100, 1/500, 1/1000, 1/5000, 1/10000, 1/50000. The nuclei 5 are formed as carbon fibers on a pitch base (PAN).

In some other embodiments, not shown, materials or materials which are used, for example, as reinforcing fibers and / or particles can be used as crystallization cores, for example glass fibers, aramid fibers, copper particles. In addition, friction-reducing particles and materials can be used, eg core-shell particles, PTFE. The nuclei 5 are arranged perpendicular to the surface. In some other embodiments, not shown, the nuclei may also be at a different angle from the surface 4 protrude. The nuclei 5 are so to the surface 4 arranged that they are the surface 4 with their smallest surface facing. The surface 4 can the nuclei 5 include. Alternatively, all or part of the nuclei can be 5 be covered by the injection molding material.

2 shows a schematic representation of a sequence program of a method 10 for producing an injection-molded part according to an embodiment. In the process 10 is in a process 11 an injection mold provided. In another process 12 For example, a plurality of crystallization cores are applied to a surface of the injection mold. Subsequently, in one process 13 an injection molding material introduced into the injection mold. Eventually, the crystallization cores may be in another process 14 be aligned so that they protrude along a major extent of the surface of the injection mold. The process 14 can, for example, to allow the alignment of the nuclei, a process 15 in which the crystallization cores and / or the injection mold are polarized. In addition or alternatively, the process 14 for aligning the crystallization cores also a static charging of the injection mold and / or the crystallization cores in one operation 16 include.

In other words, the crystallization cores can be applied to the tool surface prior to injecting the injection molding compound. Optionally, the crystallization cores may be mixed with another medium, for example a liquid or a gas. Maybe such an application can be facilitated. The adhesion and orientation of the nuclei can be at least improved or even ensured by a prior static charging or polarizing of the particles. For highly anti-adhesive materials it may be necessary to increase surface energy of the particles before application to improve adhesion, for example by plasma activation of PTFE fibers. Thus, a Einbringprozess can take place similar to a powder coating. If the particles do not have a round shape, but have a greater length than width, for example as fibers, they should be aligned as perpendicular to this when applied to the tool surface. This can possibly be ensured by the polarization of the particles.

3 shows a schematic representation of an injection mold 20 in the production of an injection molded part, not shown, according to an embodiment. nuclei 5 be on a surface 21 that the injection mold 20 limited to the inside, applied. For this, the injection mold 20 into the crystallization cores 5 be dipped or these can be applied with a brush or other tool. The nuclei 5 are aligned with the injection mold 20 arranged. This can be done, for example, by applying a magnetic and electric field, which is schematically represented by the field lines 22 is shown done. Under certain circumstances, the crystallization nuclei 5 or else the injection mold 20 also before the application of the nuclei 5 in the injection mold 20 static charged or polarized. Then an injection molding material 23 in the injection mold 20 brought in. Possibly, the alignment of the crystallization nuclei 5 before, after or overlapping in time, take place with the introduction of the injection molding material.

In other words, some embodiments relate to a method to reduce the negative characteristics of the skin of the skin 3 to improve or eliminate. For this purpose, friction and / or wear-reducing additives in the edge area 3 introduced during a manufacturing or production cycle. For this a medium can be applied to the injection mold 20 , which may also be referred to as an injection mold, are applied, for example by spraying. The medium may possibly improve the tribological properties of the spray skin. This can be achieved, for example, by an artificially increased crystallinity, which can also be referred to as the degree of crystallization, of the sprayed skin. The sprayed-on medium may comprise tribologically active particles, for example the crystallization cores, reinforcing fiber particles, friction-reducing additives and / or a carrier. The carrier may be, for example, a liquid or a gas. Under certain circumstances, the inert can volatilize or evaporate after application.

In order to reliably anchor or store the crystallization cores or the reinforcing fibers and / or the tribologically active particles, which may also be referred to as friction reducers, it may be necessary to remove the particles prior to application in the injection mold, which also acts as a tool can be designated to charge statically. Another possibility may be the use of polarized substances. The crystallization cores or the particles or fibers then lie in some embodiments not flat on the tool surface, but are aligned perpendicular to the tool surface. This may eventually allow complete enclosure or at least encircling of the largest possible surface area of the crystallization core through the melt. In some embodiments, this may result in reduced wear on the run-in, reduced run-in friction, less play increase, improved engagement ratios, improved compliance, and / or extended service life. In addition, a process outlay (in particular the cycle time) may possibly be reduced.

The embodiments disclosed in the foregoing description, the appended claims and the appended figures, as well as their individual features, may be relevant and implemented both individually and in any combination for the realization of an embodiment in its various forms. In some other embodiments, features disclosed as a device feature in other embodiments may also be implemented as method features. Further, features that are implemented as method features in some embodiments may also be implemented as device features in other embodiments.

LIST OF REFERENCE NUMBERS

1

injection molding

2

Internal component

3

border area

4

surface

5

nucleation

10

method

11

Provide process

12

Apply process

13

Insert process

14

Align process

15

Polarize process

16

Process static charging

20

injection mold

21

surface

22

field line

23

Injection material

Claims (10)

Injection molded part ( 1 ) comprising an injection molding material, having the following features: a component interior ( 2 ) a border area ( 3 ) located between a surface of the injection molded part ( 1 ) and the component interior ( 2 ) is arranged, wherein in the edge region ( 3 ) Crystallization cores ( 5 ) different from the injection molding material are arranged. An injection molded part according to claim 1, wherein a material of the crystallization cores ( 5 ), Coal, PAN, glass, aramid, copper, and / or PTEFE or nanoparticles. An injection molded part according to any one of the preceding claims, wherein a crystallization core ( 5 ) have a maximum length of 0.5 mm. An injection molded part according to any one of the preceding claims, wherein a crystallization core ( 5 ) has a thickness which is at most 0.5 mm. Injection molded part according to one of the preceding claims, wherein the crystallization cores ( 5 ), at least in part, along a major extent perpendicular to the surface of the molded part ( 1 ) are arranged. Injection molded part according to one of the preceding claims, wherein the injection molded part ( 1 ) is a gear, a gear element, a sliding bearing, a sliding bearing element, a bearing cage, a bearing cage element, a worm drive or a shaft, wherein the crystallization cores ( 5 ) are arranged at least in the region of a tribologically stressed surface. Procedure ( 10 ) for producing an injection molded part ( 1 ), comprising: providing ( 11 ) an injection mold ( 29 ); Application ( 12 ) of crystallization cores ( 5 ) on a surface ( 21 ) of the injection mold ( 5 ); Introduction ( 13 ) of an injection molding material ( 23 ) in the injection mold ( 5 ). The method of claim 7, further comprising: aligning ( 14 ) of the crystallization cores ( 5 ), so that along their main extent from the surface ( 21 ) of the injection mold ( 5 ) stand out. The method of claim 8 further comprising: polarizing ( 15 ) and / or static charging ( 16 ) of the crystallization cores ( 5 ), so these are along its main extent perpendicular to the surface ( 21 ) of the injection mold ( 20 ) Arrange. Method according to one of claims 8 or 9, comprising: applying a magnetic or static field ( 22 ) to effect the alignment.

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