DE202018104226U1 - Injection molded sliding bearing component with marking - Google Patents

Abstract

Injection molded sliding bearing component (1, 2, 3), which is made of plastic by injection molding as a one-piece plastic body having a first surface (121, 221, 321) and at least one second surface (122, 222, 322), wherein the first Surface comprises a sliding surface (121, 221, 321) for sliding storage of and / or on a sliding partner; characterized,
in that the second surface (122, 222, 322) comprises at least one marker (10, 20, 30) comprising a data code marker (10, 20, 30) with a 2D code encoding data, and
the data code marking (10, 20, 30) is injection-molded into the plastic body and provided on the second surface (122, 222, 322) in a machine-readable manner.

Description

The invention relates generally to the marking of injection molded slide bearing plastic parts for a plain bearing.

Under plain bearings is understood in particular in the sense of mechanical engineering, a device for sliding guide against each other movable components, in particular against each other movable machine components. In a plain bearing, typically at least two sliding partners movable relative to each other are in direct contact with each other through their respective sliding surfaces. In contrast to rolling bearings, the sliding partners slide directly against each other along their sliding surfaces against the resistance caused by a friction of the sliding surfaces (sliding friction). The sliding partners interact with each other through their respective sliding surfaces for storage.

In the present case, the term slide bearing encompasses all bearing types, in particular with regard to the degrees of freedom, for example radial bearings, thrust bearings, linear bearings, spherical plain bearings. The term plain bearing component includes e.g. also a component of a linear guide system which has at least one sliding surface. In the present case, the bearing component as well as the bearing component are also included with the sliding bearing component.

In injection molding directly usable components of plain bearings in mass production or mass production can be produced inexpensively.

More particularly, the invention relates to such a generic injection-molded sliding bearing component, which is made of plastic by injection molding, in particular as a one-piece plastic body. The plastic body has a first surface and at least one second surface, wherein the first surface comprises a sliding surface for sliding storage of and / or on a sliding partner.

In the injection molding process, markings can be made by appropriate design of the negative mold, such as protruding or recessed writing of the surface, e.g. with article number and manufacturer. It is also known to introduce variable markers in injection molding, e.g. to the date of manufacture. This is typically done by so-called "casting watches", i. in the injection mold rotatable stamp, which introduce a kind of time stamp in the plastic body, which is usually visible on the outside. In this case, a marking means in particular optically readable information, whether human-readable and / or machine-readable.

In the marking and marking technology of products in general, so-called 2D codes are increasingly being used, in particular matrix codes. Widespread are e.g. the so-called QR-Code®, in particular according to ISO / IEC 18004, or the so-called DataMatrix ™ code, in particular according to ISO / IEC 16022. These are each optically machine-readable symbols. They offer u.a. Higher information density compared to alphanumeric labeling or EAN barcodes. Two-dimensional codes are used for part identification in manufacturing, for example, in process automation, traceability, quality control, etc. Reliable, fast and accurate identification is also advantageous after manufacture, especially at the user.

An increasingly used technique is the direct parts marking or Direct Marking (DPM) with two-dimensional codes (2D codes) on parts surfaces. DPM relates to methods of applying a permanent mark directly to the surface of a product. Compared to the subsequent application of labels or the like. The direct marking is safer and easier to automate.

Various DPM technologies are known, cf. Introduction to WO 2016/054647 A1 , For example, laser marking is known, which is partly suitable for plastic parts.

For example, the patents describe laser marking of plastic injection molded parts DE 10 2005 017 807 B4 and DE 10 2005 017 808 B4 Injection molded parts for fuel injection valves, which have a special additional plastic layer for laser marking. These injection-molded parts with the special laser-inscribable layer are produced in a 2-component injection molding process and marked later in an additional process step.

Also known are needle markers, scoring markers, needle-scoring engraving systems and similar engraving machines to introduce a mark directly into the part surface. These are mainly used for metal parts. As with laser engraving, it involves intrusive or subtractive methods which subsequently modify the surface of the component in a controlled manner, e.g. to bring in the desired 2D code.

There are also known non-intrusive techniques, in particular additive marking methods, which mark by subsequently applying a layer of media to the surface, e.g. the inkjet marking, cf. Details in Technical Report ISO / IEC TR 24720 (first edition 2008).

The above DPM techniques can be integrated into the production process, mark components later in a separate step. This results in extra effort and an inherent confusion is not given (ie incorrect part marking is possible).

In the metal casting technique has also been proposed to provide parts without additional operation, in the original molding of the molding, with an optically readable code marking. In the patent application WO 02/09018 A2 It has been proposed to use a special mold-making insert of the ceramic casting mold, which produces a negative mold of a desired matrix code, eg a DataMatrix ™ code, in the mold, eg for a rotor blade of a turbine. The special insert is thereby integrated into the model (positive mold), which is used for the production of the mold (negative mold), for a subsequent original molding from the liquid state. The insert and the model are made of waxy fusible material. Both are removed by heating from the mold so that a negative mold of the desired 2D code remains in the mold.

Another approach to the marking of metal castings during the original molding process (original forms from the liquid state) describes the patent DE 10 2008 024 906 B3 , This is to a tamper-evident marking of castings are made possible during the original molding process. In this case, a stamp which can be adjusted with respect to the coding is provided, which generates variably adjustable negative forms of the matrix code elements on the casting wall facing the molten metal, which the casting process fills with melt to form a 2D code. Thus, the code can optionally be reset from one part to the next. Such a mold is complex, cost-intensive and maintenance-intensive or error-prone.

The two above approaches from the foundry technology for metal parts are not readily suitable for plastic injection molding with relatively high pressure (prototyping from the plastic state).

In sliding bearing components is aggravating that the different materials from which they are made, should have a high strength. Such parts can be made of a number of different specialty plastics, in particular tribologically optimized plastics, and are therefore, if at all, only conditionally reliable or can be marked with the same quality using conventional techniques for direct marking. Even a laser inscription is not readily possible with all such plastics. Even with other methods attaching sufficient for machine reading code marks on plastic for industrial sliding bearing components is often not possible.

However, a simple solution for marking injection molded sliding bearing components with additional information is also desirable in the course of the production of sliding bearing components by injection molding from engineering plastics.

It is therefore an object of the invention to provide a cost effective and reliable technique which allows to mark injection molded slide bearing components. The technology should be particularly confusion-proof and as reliable as possible, even at very high quantities.

This object is achieved by an injection-molded sliding bearing component according to claim 1 and independently by a plastic injection molding tool according to claim 28.

It is first proposed according to the preamble of claim 1, an injection-molded sliding bearing component, which consists at least predominantly of a plastic and in the injection molding process, in particular as a one-piece plastic body produced. The plastic body has a first surface and at least one second surface, wherein at least or only the first surface comprises a sliding surface for sliding mounting of and / or on a sliding partner.

In the simplest embodiment, it is proposed according to the invention that the second surface has at least one marking which comprises a data code marking with a 2D code. This data code marking is introduced into the plastic body during production by injection molding or in the injection molding tool and provided on the second surface in a machine-readable manner. Thus, the 2D code can be generated in particular by the injection molding tool itself. The 2D code encodes data and is suitable for capturing this data by a data acquisition device. The detection can be done optically, in particular electro-optically, with a commercially available data acquisition device or code reader. The data code marking is visible at least in the loose or unassembled state.

According to the invention, the data code marking is thus produced together with the actual injection-molded body in the course of its production by injection molding or in a correspondingly designed molding tool or injection molding tool. Due to the fixed allocation in the mold, confusion is excluded. The marking is an integral part of the injection molded part or plastic body and thus can not be separated from the slide bearing component without being destroyed.

The production costs for such a special data code marking are minimized by the integration into the injection molding process, since only one-time costs for the production or subsequent adaptation of the injection mold arise. There are no additional or special marking devices required.

The plastic body can in particular be made of the same material.

In principle, it is possible to produce in the 2-component process, but it is preferred to produce the data code marking with the 2D code from one and the same plastic or the same plastic composition of which the injection-molded body is made of the same material. The data code marking with the 2D code, in particular including the visible surface of the first and second symbol elements, is thus manufactured or molded in one piece with the plastic body, in particular of the same plastic material from the same material. This solution allows a particularly cost-effective production using relatively simple tools.

The plastic may comprise a tribologically optimized material, in particular a tribopolymer, or consist thereof. A tribologically optimized material is understood in particular to mean a material which, in addition to a base polymer, comprises friction-improving and / or wear-improving constituents which reduce the coefficient of friction and / or the wear of the base polymer, in particular of a reinforced base polymer. In particular, a tribologically optimized material can have a coefficient of friction or friction coefficient μ _{G of} ≦ 0.5, in particular of ≦ 0.4, against steel at a contact pressure of 1.2 MPa and a sliding speed v of 0.3 m / s.

The use of tribologically optimized plastic for sliding bearing is particularly advantageous because it eliminates the need for additional lubrication with lubricants, e.g. with grease or oil, can be avoided. Such lubrication-free plain bearings are therefore basically less expensive and particularly advantageous for applications in which a subsequent lubrication is not possible, very expensive and / or very expensive.

The tribologically optimized material may include lubricants, especially solid lubricants. The solid lubricants are preferably as microscopic particles, e.g. with diameter between 1 and 1000 μm, embedded in the material, compounded or incorporated. The preferred solid lubricants lubricate the sliding surfaces during slide bearing and reduce sliding friction. The tribologically optimized material may comprise a base polymer with embedded lubricant particles and other additives, such as e.g. technical fibers and / or fillers.

Without wishing to be bound by theory, it is believed that the solid lubricants embedded in the tribopolymer of the sliding bearing component have a surprisingly favorable effect on the desired optical mode of action of the 2D code, in particular light diffusion (see below).

The plastic may preferably comprise a thermoplastic base polymer, in particular a reinforced thermoplastic base polymer for high strength. The data code marking according to the invention is particularly advantageous in combination with injection-molded parts made from reinforced injection-moldable plastic, which are scarcely or not suitable for laser inscription. This also increases the durability or abrasion resistance of the components of the 2D code. Reinforcing materials, e.g. Fibers, the slide bearing component can additionally stabilize and reinforce, especially for long-term stress, so that high forces or edge loads can be absorbed.

For a substantially continuous monochrome coloring, the plastic may contain colored pigments and / or non-colored pigments, in particular black pigments, e.g. Carbon black. Pigments in the present case are colorants in general, i.a. also dyes, meant. Particularly preferred are pigments which improve the UV resistance of the plastic. The injection molded part may possibly have further, for example subsequently applied color markings, or be substantially monochrome.

The injection molded part should provide sufficient resistance to elastic deformation for use as a sliding bearing component. For this purpose, the plastic preferably has a modulus of elasticity or Young's modulus according to DIN 53457 test methods of at least 1100 MPa, more preferably of at least 2400 MPa.

For good dimensional stability, the plastic may preferably have a heat deflection temperature DIN EN ISO 75-1 to 75-3 of at least 80 ° C, preferably of at least 100 ° C.

The plastic has, inter alia, in order to avoid scratches or unwanted indentations, etc., preferably a Shore D hardness of at least 60, in particular of at least 70 (after DIN 53505 Test method). A combination of one or more of the above plastic properties also has a favorable effect on the Durability of the 2D code, especially in harsh industrial conditions.

For the production of small-sized and / or high-resolution 2D codes with fine structures, it is advantageous if the plastic has suitable flow properties during the injection molding process. The plastic preferably has a melt flow index (Engl DIN EN ISO 1133 , especially DIN EN ISO 1133-1: 2012-03 Melt mass flow rate (MFR)) of at least 3 g / 10 min, preferably of at least 6 g / 10 min, more preferably of at least 20 g / 10 min on. The melt flow index can be determined in cm ^3/10 min and a melt volume-flow rate (MVR). A sufficiently high melt flow index is advantageous for forming 2D codes by injection molding, so that the molten polymer reliably fills even small-sized cavities of an injection mold, which belong to the marking area for a desired 2D code. This makes it possible to reliably realize even very small dimensioned 2D codes, eg with dimensions smaller than 4mm x 4mm.

In a preferred embodiment, a matrix code in an already widespread or standardized format is used as the 2D code in the data code marking. Particularly preferred is, for example, a QR code, in particular according to ISO / IEC 18004. In the present case, QR codes are also understood to mean variants thereof such as micro QR code, SQRC, iQR code or design QR code, etc.

Also common is the format of the so-called DataMatrix ™ code according to ISO / IEC 16022 or a so-called GS1 DataMatrix. Other known 2D codes are possible, e.g. an EZ-Code®.

By "code" is meant here the mapping of data into an optically recognizable symbol. Such codes use for encoding a spatially two-dimensional arrangement of two optically different types of planar elements, code fields or so-called. Symbol modules (hereinafter symbol elements), which together make up the actual data code symbol. Hereinafter, the two different element types will be referred to as first symbol elements and second symbol elements.

In the present case, a symbol element is a planar region which, by way of optical action and / or shape, together with further symbol elements, represents a 2D code symbol. Symbol elements of the first type have a largely similar optical effect and / or shape or are visually equivalent to one another. The same applies to the second symbol elements. However, the first symbol elements differ significantly in their optical effect and / or shape from the second symbol elements. Conventional, printed matrix codes are square cells of typical size as symbol modules in two different optically distinguishable contrasting colors, mostly black / white.

In a preferred embodiment, however, it is provided that the first symbol elements have a different (real) surface finish than the second symbol elements. Due to the different surface characteristics of the symbol elements, an optical contrast in the sense of different light reflection can be recognized, in particular even without different coloring of the substances which represent the symbol elements.

In the approach according to the invention, one and the same plastic is preferably used for the injection-molded sliding-bearing component and the data-code marking. A different color of the symbol elements is not necessary or not provided.

To further simplify the production, it may be provided that the first symbol elements have the same surface finish, which also has a second surface of the injection-molded slide bearing component, in any case over a predominant surface portion of the second surface. The second symbol elements can in particular have a contrasting surface profile or different profile properties concerning the actual surface finish. Surface profile here means the actual surface profile in cross section along at least one of the main directions, preferably along the two directions. The profile preferably has identical or optically equivalent properties throughout the area of all second symbol elements. The surface or profile property can be disordered, uneven and / or chaotic.

The first and second symbol elements may, in particular with regard to their roughness characteristics ( DIN EN ISO 4287 ).

In a preferred embodiment, provision is made in particular for the first symbol elements to have a smoother surface, ie to have a roughness which is smaller in magnitude than the second symbol elements. In this case, all the first symbol elements have a surface texture identical to one another in the technical sense, but a surface texture which is detectably different from all other symbol elements. The roughness can be with itself metrologically record the known technical methods on the surface of the symbol elements.

In a preferred embodiment, it is provided that the first symbol elements have an arithmetic mean roughness Ra in the range from 0.5 μm to 3.5 μm (microns), preferably in the range from 0.75 μm to 2.75 μm, and the second symbol elements have an arithmetic mean roughness Ra in the range of 5 .mu.m to 12 .mu.m, preferably in the range of 6.50 .mu.m to 10.50 .mu.m. The measurement of the arithmetic mean roughness Ra can be done in particular according to Standard DIN EN ISO 4288 (Version 1997) in the stylus method, with Ra as the standardized parameter DIN EN ISO 4287 (Version 1998).

The second surface is preferably not a sliding surface. The data code marking is preferably provided on those surfaces which are not subject to dynamic friction as intended.

The second surface may be curved. The machine-readable data code mark can also be applied by injection molding to surfaces that are not level.

In at least one main direction of the data code marker or the 2D code, the width and / or the length of the symbol elements of the 2D code can be adapted so that this data code marker can be well machine readable in a projection onto a projection plane in this projection plane is or appears. For this purpose, the data code marking can be represented or imaged on the second surface so distorted that its optical projection appears at least approximately flat on a projection plane and machine-readable like a planar code in this projection plane. The distorted data code mark then corresponds to the inverse mapping from said projection plane to the curved, e.g. cylindrical second surface of the sliding bearing component. In this way, even on curved surfaces, e.g. on the outside of a plain bearing bush, map machine-readable QR codes.

To simplify the production of the molds, provision may be made for the first symbol elements to be flush with the data area of the second surface and to be level with them. The first symbol elements can pass smoothly into the surrounding surface of the injection-molded slide bearing component. This arrangement simplifies the mold construction, as this may require special processing only for the second symbol elements.

A particularly simple first production or subsequent adaptation of a suitable or existing injection mold is made possible if the second symbol elements are formed by regions which protrude from the surface of the second surface of the injection-molded sliding bearing component or are raised. This has the advantage, especially with thinner-walled components, of not changing the (macroscopic) geometry of the injection-molded part.

It is advantageous if the marking causes no appreciable weakening of the wall thickness in order not to impair the desired stability of the sliding bearing component.

For optical detection, it is advantageous if the average height difference between the surfaces of the first and second symbol elements is less than or equal to 0.5 mm. This also makes it possible to use symbol elements with relatively smaller, e.g. square base area reliably read even with a very oblique orientation to the optical axis of the data acquisition device. In addition, the component geometry is not noticeably changed.

Specifically, the data code mark may be made together with a structural portion of the injection molded slide bearing component, i. without additional, separate parts area for the marking or corresponding material cost.

Alternatively or additionally, it is possible to provide the data code marking as a whole in a region of the first side of the injection-molded body which is recessed with respect to the second surface. This protects the mark and the like. against abrasion, for example, to interference edges or the like. Likewise, it is possible to additionally or alternatively form the second symbol elements by areas that are recessed or jump back relative to the surface of the second side of the injection-molded sliding bearing component. Irrespective of this, the data code marking should be provided in a surface area of the plastic body which is clearly visible, but which is not susceptible to wear or which is less prone to wear.

Regardless of the chosen surface condition of both types of symbol elements of the 2D code, a preferred embodiment provides that the second symbol elements produce or generate more intense light scattering or more pronounced diffuse reflection than the first symbol elements through their surface with identical light irradiation. Due to different light scattering, a brightness difference can be visually or visually perceived without changing the material properties. In other words, the symbol elements are preferably not discolored, but cause optical contrast only due to different light scattering.

The optical contrast or the optical differentiability of the different symbol elements is thus preferably caused by different optical scattering properties. For example, the first symbol elements may have a roughness or roughness which is as low as possible in terms of technology and accordingly act approximately like an ordinary reflection surface which reflects incident light relatively well (angle of incidence = angle of reflection, taking into account the material-dependent absorption degree). In contrast, the second symbol elements due to the given different surface texture, for example, by appropriate roughening in the injection mold, a predetermined, significantly stronger optical scattering effect with respect to incident light. The stronger light scattering of the second symbol elements in comparison to the first symbol elements can be determined, for example, via the scattering coefficient or the scattering cross section with a known optical method and optionally optimized.

Experiments have shown that even the stronger light scattering by the second symbol elements provides sufficient optical discrimination compared to the first symbol elements to convert conventional matrix codes, for example a QR code, with commercially available devices, e.g. a common smartphone, reliable to recognize.

The light scattering by the second symbol elements ideally should come as close as possible to diffuse reflection (Lambert radiators). For this purpose, the second symbol elements can have a large roughness, in particular on their surfaces, relative to the wavelength range of visible light. Basically, the first and second symbol elements may have different degrees of light reflectance related to the same measuring arrangement, e.g. differ by at least 20%. The first symbol elements can be a smooth z.T. have reflective surface.

In a preferred embodiment, the second symbol elements furthermore generate an optically substantially isotropic light scattering. Assuming a spherical coordinate system with pole axis or Z axis parallel to the surface normal at the base of the 2D code as equatorial plane (eg flush with the surface of the first symbol elements), substantially isotropic light scattering means here that the quantity of light scattering in a selected direction At a constant azimuth angle substantially not dependent on the polar angle. This can usually be checked visually, e.g. if the viewer does not perceive any significant change in brightness on the second symbol elements when the component is rotated about the Z axis and the light is constant.

Such substantially isotropic light scattering can be achieved, for example, by aperiodic, e.g. technically chaotic, to achieve surface profiles adjusted so that the quantitative deviation over the entire polar angle range (from 0 to 2π) is less than a predetermined threshold, e.g. over the entire polar angle range by no more than 15% deviation. An approximately identical (isotropic) light scattering in all directions can be achieved, in particular, if the roughness, or the deviation from an ideally smooth surface, on the second symbol elements is as far as possible independent of both surface directions.

Anisotropic light scattering would also be conceivable, for example. by diffraction gratings or similar periodic structures, e.g. regular hatching of the surface. However, an advantage of isotropic light scattering lies in the fact that the relative orientation of the data code marking to the optics of the data acquisition device is irrelevant with regard to the polar angle.

The inventive generation of the data code marking with the 2D code during injection molding or in the injection mold is in particular allows the 2D code including the visible surfaces of the first and second symbol elements is integrally made of the same plastic as the actual plastic body itself For example, customary for injection-molded sliding bearing components polymers or plastic mixtures, optionally with reinforcing fillers, eg with reinforcing fibers are used. The data code marking is possible, in particular, with the color of the plastic remaining the same throughout, even with a visually black plastic, i. even without materially different colors of the two basic types of symbol elements in the 2D code.

The proposed solution makes it possible, in particular, to produce the data code marking with the 2D code in a tool-falling manner with the plastic body, so that it is already machine-readable without any post-processing. The data code marking can therefore be produced in particular as a direct marking together with the injection-molded sliding bearing component in the same injection mold. This allows a particularly cost-effective marking with a 2D code or a matrix code.

Experiments show that an optically well detectable different surface finish of the first symbol elements compared to the second symbol elements can be achieved if, on the one hand, the first symbol elements have a surface finish which achieves spark erosion of the mold by electroerosive machining or spark erosion (DIN 8580) leaves. On the other hand, a suitable surface finish of the second symbol elements can be achieved if their surface finish corresponds to a laser engraving, in particular a deep laser engraving or 3D laser engraving of the injection mold (molding tool). In this case, the second surface of the injection molded sliding bearing component outside the data code marking can likewise correspond to a spark sinking erosion. The first surface of the injection molded sliding bearing component can have at least predominantly the same surface finish as the second surface. For example, it may have a cylindrical surface machined by machining, eg a cylindrical surface turned on a lathe, and subsequently ground surface quality. Alternatively, a surface quality produced by spark erosion (EDM: electrical discharge machining) is also conceivable. By way of example, relatively small roughness depths of the second surface and optionally of the first symbol elements can be achieved by spark erosion, ie desirably smooth surfaces. Another advantage is that only for the optical contrast of the second symbol elements, a different method in the tool production of the mold is required, for example, a laser machining of the injection mold.

In terms of data technology, the data code marking is preferably a permanent marking which remains the same over all identical injection-molded plain bearing components, i. unchangeable in the injection mold. In this case, the data encoded by the 2D code may in particular comprise a manufacturer-specific URL identifier or a PURL identifier. Thus, the user, for example, the maintenance personnel, using a standard smartphone with software for scanning the 2D code, such as a QR code reader, in the simplest way locally from the injection molded slide bearing component on a corresponding predetermined Internet page of the Be guided by the manufacturer.

In particular for the detection of product counterfeiting, it is advantageous if the data coded by the 2D code comprise encrypted and / or slide bearing component-specific data contents. For this, e.g. an SQRC code (secure QR code) are used.

In addition to the special data code marking, the injection-molded sliding bearing component can furthermore have a conventional user-readable marking, in particular a time marker, which makes it possible to determine the time of manufacture. This can likewise be introduced into the plastic body during injection molding, e.g. by means of a time-variable pouring clock marking punch. Even such conventional, user-readable markings are preferably provided on the second surface of the injection-molded sliding bearing component, on which the data code mark is also provided.

The invention is applicable to the production of injection molded parts for plain bearings. Each individual injection molded sliding bearing component can each have its own permanently assigned 2D code in the corresponding data code marking. Thus, i.a. each item of plain bearing easily identifiable to the user. Alternatively, several different mating plain bearing parts may have the same 2D code.

The invention further relates to a plain bearing, in particular linear plain bearings and / or radial plain bearings, comprising at least one injection-molded sliding bearing component according to one of the preceding embodiments, and in particular a sliding partner for the injection-molded sliding bearing component, with which the injection-molded sliding bearing component by the sliding surface (n ) can interact. The injection-molded sliding bearing component and its sliding partner are movably arranged relative to each other and are in contact with each other through their sliding surfaces. The sliding partner slidably supports the injection molded sliding bearing component or is mounted on the injection molded sliding bearing component. During sliding bearing, the sliding surface of the injection molded sliding bearing member slides along a surface of the sliding partner. The sliding partner may be another injection-molded sliding bearing component or a differently manufactured component, e.g. made of metal, such as a shaft, axle, guide rail or the like., To be.

An advantage of the invention lies in the fact that a cost-effective product marking of the sliding bearing is made possible in total with a 2D code by utilizing the injection-molding process, because a separate marking of the sliding partner is often not required.

The invention consequently also relates to a plastic injection molding tool for the production of injection molded sliding bearing components made of plastic. The injection mold can be made in particular of steel. According to the invention, the injection mold has a predetermined, fixed in the injection molding marking range for a 2D code, which is formed or incorporated in the forming wall to limit the injection molding cavity. The marking area has a Number of first symbol areas. In particular, the first symbol regions can be turned and ground or produced by spark-die erosion. For example, the first symbol areas may be generated together with the production of the boundary wall for the second surface of the injection-molded slide bearing component. Furthermore, the marking area in the molding tool has a number of second symbol areas which have a different surface finish, in particular a larger roughness, than the first symbol areas. The second symbol areas can be generated or provided in particular in the course of the first production or also subsequently, in particular by laser engraving of the injection mold. As a laser engraving in particular a deep laser engraving or 3D laser engraving of the injection mold or the mold into consideration.

The first symbol areas therefore serve to generate the first symbol elements and the second symbol regions to generate the second symbol elements. In particular, a mold half (half-shell) of a two-part mold is understood to mean injection molding tool, since it is sufficient if the data code marking is present on one side.

The proposed data code marking of plastic components of plain bearings offers a wide variety of application advantages. An injection molded sliding bearing component with 2D code can offer different additional benefits. Thus, e.g. the assembly and / or maintenance are simplified or assisted e.g. by calling for information on the design, installation and / or maintenance of the sliding bearing. It is also possible to directly order parts using the 2D code. In this case, the user can by data acquisition of the 2D code with a smartphone, tablet or the like. Directly on the injection molded slide bearing component on a manufacturer's side, e.g. the product series are associated with this associated with injection molded slide bearing component web page, e.g. via a URL created in the QR code.

The website may provide product information, such as Have installation or maintenance instructions, specification data of the items and / or the sliding bearing, etc. It may be additionally or alternatively provided an ordering function for ordering spare parts.

In particular, at least one individual part of a specific plain bearing can be provided with a uniquely assigned own 2D code in order to offer such additional benefits.

Further, optionally after scanning the 2D code, web-based supplementary queries, e.g. with respect to at least one parameter of the injection molded slide bearing component, are directed to the user to provide targeted information. Also conceivable is the call of an application on the terminal, which provides additional benefits to the product.

The data code tag is also useful for detecting counterfeit products, e.g. using encrypted additional data. Additionally and / or alternatively, the user can be guided by data acquisition of the 2D code on the injection-molded sliding bearing component on a manufacturer-side, the injection molded sliding bearing component associated website. Thus, supplementary queries, in particular with regard to at least one identification feature of the injection-molded slide bearing component, can be directed to the user, for example in order to provide information about the authenticity or a forgery.

• 1: ein Ausführungsbeispiel eines zylindrischen Gleitlagers in Perspektivansicht;
• 2A: ein Ausführungsbeispiel eines Gelenklagers in Seitenansicht;
• 2B: eine Gehäusehälfte eines Gelenklagers nach 2A in Seitenansicht;
• 3A: ein Ausführungsbeispiel eines Schlittens für ein Linearlager in Seitenansicht;
• 3B: den Schlitten nach 3A in Draufsicht;
• 3C: eine Vergrößerung der Datencode-Markierung nach 3B;
• 4: einen schematischen Querschnitt der Oberflächenprofile erster und zweiter Symbolelemente in der Datencode-Markierung nach 3C gemäß der Schnittlinie IV-IV in 3C;
• 5: ein Lichtbild einer Formhälfte eines Spritzgießwerkzeugs zur Herstellung eines Gleitlagerbauteils nach 3A, 3B; und
• 6: eine schematische Prinzip-Darstellung zum arithmetischen Mittenrauwert Ra (Kenngröße nach DIN EN ISO 4287:1998 ) an einem aperiodischen Oberflächenprofil (Z(x)) - analog zu den zweiten Symbolelementen in 4 - über eine Messstrecke (lr).

Further details, features and advantages of the invention will become apparent without limitation from the following detailed description of preferred embodiments with reference to the accompanying drawings. These show:

• 1 : An embodiment of a cylindrical plain bearing in perspective view;
• 2A : An embodiment of a joint bearing in side view;
• 2 B : a housing half of a joint bearing after 2A in side view;
• 3A : An embodiment of a carriage for a linear bearing in side view;
• 3B : the sledge after 3A in plan view;
• 3C : an increase in the data code mark after 3B ;
• 4 FIG. 2: a schematic cross section of the surface profiles of first and second symbol elements in the data code marking 3C according to the section line IV-IV in 3C ;
• 5 a photograph of a mold half of an injection mold for producing a sliding bearing component according to 3A . 3B ; and
• 6 : a schematic principle representation of the arithmetic mean roughness Ra (characteristic after DIN EN ISO 4287: 1998 ) on an aperiodic surface profile (Z (x)) - analogous to the second symbol elements in 4 - over a measuring section (lr).

In 1 is a cylindrical injection molded sliding bearing component 1 shown without the associated sliding partner. The injection molded sliding bearing component 1 is designed as a bearing bush and has a tubular section 11 with two longitudinal ends 111 and 112 on. At the first longitudinal end 111 is a Einführschräge trained. At the second longitudinal end 112 points the section 11 a flange-shaped collar 12 on. The tubular section 11 of the injection-molded sliding bearing component 1 has an inside diameter d1 , an outer diameter d2 , and a wall thickness ( d2 - d1 ) / 2. The injection molded sliding bearing component 1 has a first surface 121 , here the internal cylindrical surface, and a second surface 122 , here the outer cylindrical surface. In an operating arrangement (not shown), the injection-molded sliding bearing component is 1 as plain bearing bush in a housing bore o.ä. without play, eg with pressfit (engl. pressfit)), fastened and in it except for the waistband 12 added. The insertion bevel at the first longitudinal end 111 facilitates the assembly.

The first surface 121 is a sliding surface 121 and in the intended operating arrangement, for example, a shaft or axle (not shown), for example made of steel, sliding store eg for rotation about its own longitudinal axis. During this movement, a cylindrical surface of the sliding partner, eg the shaft / axle, slides in sliding contact with and against the sliding surface 121 , The injection molded sliding bearing component 1 outsourced in the example 1 as bearing component the sliding partner as a stored component.

The cylindrical opposite second surface 122 which the outer diameter d2 is defined, in the intended operating arrangement no sliding surface and does not move relative to the inner surface of the housing bore (not shown).

As 1 in an enlarged schematic representation, has the curved second surface 122 a data code marker 10 with a substantially flat, two-dimensional matrix code, here a QR code according to ISO / IEC 18004 , At least in the loose unmounted state, is the data code mark 10 on the second surface 122 visible, eg for manufacturing and logistics purposes. In an operating arrangement, the data code marking must 10 however, not be visible.

In further embodiments, the data code mark may be on the flat face of the collar 12 be arranged.

A suitable QR code as data code marking 10 can be executed as a square code symbol with depending on the version 21 × 21 up to 177 × 177 individual fields for symbol modules or symbol elements. The QR code has a size of eg at least 15x15mm and is machine-readable with a data acquisition device, eg with a smartphone. The coding of a QR code according to ISO / IEC 18004 as a data code marker 10 is known per se and will not be explained here in more detail (exemplary additional benefit can be obtained by scanning the QR code 10 in 2 B be tested).

The injection molded sliding bearing component 1 is one-piece and of uniform material with the data code marking 10 , here a QR code, produced by injection molding from a tribologically optimized material. A preferred material is a reinforced thermoplastic with self-lubricating properties, which is suitable for sliding bearing without additional or subsequent lubrication. The material includes a base polymer with embedded solid lubricant particles and reinforcing fillers. Various variations of the base polymer with fillers or dyes are possible. A variety of suitable for various applications, lubrication-free bearing materials are under the trade name iglidur® of the company igus GmbH, D-51147 Cologne, available.

The plastic can, for example, have a modulus of elasticity (Young's modulus according to DIN 53457) of 7800 MPa, a dynamic sliding friction coefficient (against steel) of 0.08 to 0.15 and a Shore hardness according to DIN 53505 of 81. An exemplary plastic would be e.g. iglidur® G from igus GmbH, D-51147 Cologne. Other similar iglidur® materials, e.g. iglidur® J, iglidur® M250, iglidur® W300, iglidur® X etc. would also be suitable. These materials have a melt flow index in the range of 3 to 50 g / 10 min.

The second surface 122 which the data code marker 10 is in 1 curved, eg circular cylindrical. The data code marker 10 is therefore slightly distorted on the second surface 122 designed so that the width B the data code marker 10 and the individual symbol elements (cf. 3 below) in the circumferential direction of the tubular portion 11 considered longer than the length L in the axial direction of the tubular portion 11 , In a projection to a level in which the code is typically to be read by a data logger, the data code tag appears 10 with appropriate optical distortion in the usual square shape easy to read (see enlargement of the data code marking 10 in 1 ).

2A shows two more injection molded sliding bearing components 2 in a designated operational order, in which they together with a dome 202 to a pillow block bearing, here a joint bearing 200 , are composed. The injection-molded sliding bearing components 2 are set to one another so that they in the illustrated intended operating arrangement a housing 201 with a circular cylindrical mount for the calotte 202 to shape. The housing 201 is in 2A the stored part of the hinge bearing 200 and sliding the calotte 202 as a stored part similar to a ball joint, ie the calotte 202 as a condyle can be relative to the housing 201 to move as a socket. The dome 202 can eg iglidur® J from igus GmbH, D-51147 Cologne.

In 2 B is one of the two injection molded sliding bearing components 2 out 2A shown. The injection molded sliding bearing component 2 has a first surface that serves as a sliding surface 221 for a sliding bearing of the calotte 202 is formed and according to the intended operating arrangement 2A in sliding contact with the calotte 202 as a sliding partner. The injection molded sliding bearing component 2 also has a second surface 222 on, here an outer surface of the housing 201 , which is not a sliding surface or according to the intended operating arrangement 2A not used for slide bearing.

As 2A-2B is at the here flat shaped second surface 222 likewise a visible and machine-readable (eg with a Smartphone) data code marking 20 provided with a QR code according to ISO / IEC 18004. The injection-molded sliding bearing components 2 may be implemented as equal parts and accordingly an identical data code marking 20 exhibit. The data code marker 20 is one-piece material with the injection-molded sliding bearing component 2 produced by injection molding from a tribologically optimized plastic. The plastic, for example, a modulus of elasticity (Young's modulus after DIN 53457 ) of 3200 MPa and a Shore hardness after DIN 53505 of 77. A suitable plastic would be, for example, RN33 of the company igus GmbH, D-51147 Cologne.

In 3A and 3B is another example of an injection molded sliding bearing component 3 shown here for a linear plain bearing. The injection molded sliding bearing component 3 is in 3A-3B - in contrast to 1 and 2A-2B - The mounted part of the sliding bearing, namely a carriage of a linear guide, which is designed for a sliding, eg translational movement along a guide rail (not shown). The injection molded sliding bearing component 3 is stored in operating arrangement on a guide rail (not shown).

The 3A shows the injection molded sliding bearing component 3 in a side view. The injection molded sliding bearing component 3 has an approximately rectangular cross-section and has a receptacle 310 with a round cross-section, for example for a (not shown) threaded spindle of a spindle drive and a receptacle 320 with rectangular cross-section for the guide rail on. The inner surface of the picture 320 belongs to a first surface of the injection molded sliding bearing component 3 and serves as a sliding surface 321 for sliding along the guide rail, eg a steel guide rail. This guide rail is the sliding partner of the injection-molded sliding bearing component 3 ,

3B shows the injection molded sliding bearing component 3 in plan view, also with approximately rectangular shape. A second, in 3A-3B also flat surface 322 of the injection-molded sliding bearing component 3 namely, its outer surface has a highly visible data code mark 30 with a flat two-dimensional matrix code, here a QR code according to ISO / IEC 18004 , on. The at a flat area of the area 322 provided data code marking 30 is here square, here has a size of eg 18 × 18 mm and is in a conventional manner with a data acquisition device, such as a smartphone, even in the installed position readable.

Also the injection molded sliding bearing component 3 to 3A-3B is one-piece and made of the same material by injection molding of a tribologically optimized plastic, such as a thermoplastic polymer with embedded solid lubricant particles. The data code marker 30 is how in 1 and 2A-2B , tool-falling as a kind of direct marking with the injection-molded sliding bearing component 3 produced in the injection mold. A suitable plastic would be, for example, iglidur® P from igus GmbH, D-51147 Cologne, with a modulus of elasticity (according to DIN 53457) of 5300 MPa, a Shore hardness according to DIN 53505 of 75, a dynamic sliding friction coefficient (against steel) of 0 , 06 to 0.21.

3C For illustration only, an enlargement of the data code mark is shown 30 to 3B , A QR code consists, in a manner known per se, of different symbol elements, namely first symbol elements 31 and second symbol elements 32 (shown here in black and white for illustration). 4 shows as a schematic diagram a section in one direction along the line IV-IV out 3C (limited to the in 3C top left position marker of the QR code).

As 4 have illustrated the individual symbol elements of the QR code, namely first symbol elements 31 and second symbol elements 32 , each different surface texture. The second symbol elements have this 32 in particular a rougher cross-sectional profile, ie a greater surface roughness than the first symbol elements 31 , The more pronounced roughness of the second symbol elements 32 is measurable in particular on the basis of the arithmetic mean roughness Ra, that for the second symbol elements 32 should be noticeably larger than for the first symbol elements 31 , eg by a factor of at least 2 times, preferably> 3. The surface smoother first symbol elements 31 can have the same surface finish as the remaining or predominant second surface 322 of the injection-molded sliding bearing component 3 , The surface or cross-sectional profile of both types of symbol elements 31 respectively. 32 is in both directions x . y the level 3C similarly procured and in 4 shown only schematically and representatively. The greater roughness of the second symbol elements 32 is set so that they cause a much stronger light scattering than the first symbol elements 31 , Furthermore, the surface profile of the second symbol elements 32 in both directions x . y the main plane of the injection-molded sliding bearing component 3 aperiodic, to produce a largely isotropic light scattering.

Each injection molded slide bearing component 1 . 2 . 3 If necessary, an associated unique code can be assigned individually in each size, which can be assigned to the 2D code of the data code tag 10 . 20 . 30 is encoded and is transmitted via the recognized URL as a request parameter, for example, with a manufacturer-side website.

5 shows a roughness measurement on a mold half 50 made of steel of a plastic injection mold for producing an injection molded sliding bearing component with a code corresponding 3C , In the mold half 50 of the injection mold after 5 is the tool-generating generation of the data code marking 30 together with the injection molded sliding bearing component 3 (see. 3B) Immediately by injection molding a marking area 53 and immutable incorporated. The marking area 53 corresponds to the negative form of the desired 2D code, such as a QR code, the data code marker 30 to 3B , Demensprechend has the marker area 53 first partly square and field-like symbol areas 51 , The symbol areas 51 can be flush and without any difference in the surface texture to the rest of the smooth boundary wall of the mold half 50 be formed, in particular by spark erosion (EDM: electrical discharge machining). The marking area 53 also has second partly square and field-like symbol areas 52 the opposite to the symbol areas 51 deepened, for example, about 0.4mm deeper, lie. The second symbol areas 52 can be retrofitted by deep laser engraving or 3D laser engraving of the mold half 50 or injection mold are introduced. The laser engraving for the production of the second symbol areas 52 allows sharp-edged transitions and parameter settings to produce the desired aperiodic isotropically scattering surface profile of the second symbol elements 32 (see. 4 ).

On the basis of such a mold half 50 can be a data code marker 30 uniform material with the plastic body of the injection-molded sliding bearing component 3 and tools are produced. Post processing is for machine-readable recognition of the code of the data code tag 30 not mandatory.

Comparative measurements on prototypes show that with the molds after 5 first symbol elements 31 (and a second surface 322 ) with an arithmetic mean roughness Ra in the range of 0.75-2.75 μm, in particular smaller than 2 μm, and on the other hand surface profiles on the second symbol elements 32 with an arithmetic mean roughness Ra in the range of 6.50-10.50 μm or larger. According introduced by injection molding in the plastic body QR codes 30 can be optically captured with standard smartphones from different angles.

6 illustrates as a roughness parameter the arithmetic mean roughness Ra as a characteristic after DIN EN ISO 4287 (1998) , Ra is the arithmetic mean of the amounts of all profile values. Even when determining other characteristics, such as the average surface roughness Rz, by an electric stylus device can be measured profiles. In 6 If Z (x) illustrates a real surface profile purely schematically, it is not a measurement result. Spark erosion can be used as boundary walls of the mold halves 50 To achieve very smooth surfaces, so that pronounced peaks and grooves in the surface profile of the injection mold and thus the injection molded part are avoided (where Ra is meaningful).

LIST OF REFERENCE NUMBERS

• 1 :

  1

  Injection sliding member

  10

  Data code marking (eg QR code)

  11

  tubular section

  111

  first longitudinal end of the tubular portion

  112

  second longitudinal end of the tubular portion

  12

  Federation

  121

  sliding surface

  122

  second surface

  d1

  Inner diameter of the tubular portion

  d2

  Outer diameter of the tubular section

  B

  Width of the data code marker

  L

  Length of the data code mark

• 2A . 2 B :

  2

  Injection sliding member

  20

  Data code marking (eg QR code)

  200

  Spherical plain bearings

  201

  casing

  202

  dome

  221

  sliding surface

  222

  second surface

• 3A . 3B :

  3

  Injection sliding member

  30

  Data code marking (eg QR code)

  310

  Holder for a threaded spindle

  320

  Holder for a guide rail

  321

  sliding surface

  322

  second surface

• 3C . 4 :

  30

  Data code marking (eg QR code)

  31

  first symbol elements

  32

  second symbol elements

  322

  second surface

  x, y

  Surface directions (in the main plane)

• 5 :

  50

  Mold half of an injection mold

  51

  first symbol areas

  52

  second symbol areas

  53

  marking region

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2016/054647 A1 [0009]
• DE 102005017807 B4 [0010]
• DE 102005017808 B4 [0010]
• WO 02/09018 A2 [0014]
• DE 102008024906 B3 [0015]

Cited non-patent literature

• DIN EN ISO 75-1 [0034]
• DIN 53505 [0035, 0091]
• DIN EN ISO 1133 [0036]
• DIN EN ISO 1133-1: 2012-03 [0036]
• DIN EN ISO 4287 [0044, 0046]
• Standard DIN EN ISO 4288 [0046]
• DIN EN ISO 4287: 1998 [0079]
• DIN 53457 [0091]
• DIN EN ISO 4287 (1998) [0102]

Claims (25)

Injection molded sliding bearing component (1, 2, 3), which is made of plastic by injection molding as a one-piece plastic body having a first surface (121, 221, 321) and at least one second surface (122, 222, 322), wherein the first Surface comprises a sliding surface (121, 221, 321) for sliding storage of and / or on a sliding partner; characterized in that the second surface (122, 222, 322) comprises at least one marker (10, 20, 30) comprising a data code marker (10, 20, 30) with a 2D code encoding data, and the data code marking (10, 20, 30) is injection-molded into the plastic body and provided on the second surface (122, 222, 322) in a machine-readable manner. Injection molded sliding bearing component (1, 2, 3) according to Claim 1 , characterized in that the plastic body is made of the same material. Injection molded sliding bearing component (1, 2, 3) according to Claim 1 or 2 , characterized in that the plastic is or comprises a thermoplastic polymer. Injection molded sliding bearing component (1, 2, 3) according to one of the preceding claims, characterized in that the plastic is or comprises a tribologically optimized material, in particular a tribopolymer. Injection molded sliding bearing component (1, 2, 3) according to one of the preceding claims, in particular according to Claim 4 , characterized in that the plastic, in particular the tribologically optimized material lubricants, in particular solid lubricants comprising. Injection molded sliding bearing component (1, 2, 3) according to one of the preceding claims, characterized in that the plastic has a modulus of elasticity of at least 1100 MPa, preferably at least 2500 MPa, and / or that the plastic has a heat deflection temperature ) of at least 80 ° C, preferably of at least 100 ° C. Injection molded sliding bearing component (1, 2, 3) according to one of Claims 1 to 6 , characterized in that the 2D code (10, 20, 30) is a matrix code, preferably a QR code, in particular according to ISO / IEC 18004. Injection molded sliding bearing component (1, 2, 3) according to one of Claims 1 to 6 , characterized in that the 2D code (10, 20, 30) is a matrix code, in particular a Data Matrix code according to ISO / IEC 16022, and / or the 2D code in one piece, in particular of the same material, molded with the plastic body or is formed. Injection molded sliding bearing component (1, 2, 3) according to one of the preceding claims, characterized in that the 2D code (10, 20, 30) for coding comprises first symbol elements (31) and second symbol elements (32), wherein the first symbol elements (31) have a different surface finish than the second symbol elements (32). Injection molded sliding bearing component (1, 2, 3) according to Claim 9 , characterized in that the first symbol elements (31) and the second surface (122, 222, 322) of the injection molded sliding bearing component (1, 2, 3) have the same surface finish and / or the second symbol elements (32) have a different surface profile as the second surface (122, 222, 322). Injection molded sliding bearing component (1, 2, 3) according to Claim 9 or 10 , characterized in that the first symbol elements (31) have a smaller roughness depth than the second symbol elements (32). Injection molded sliding bearing component (1, 2, 3) according to one of Claims 9 to 11 , characterized in that the first symbol elements (31) have an arithmetic mean roughness Ra in the range of 0.5-3.5 μm, preferably in the range of 0.75-2.75 μm, and the second symbol elements (32) have an arithmetic mean roughness Ra in the range of 5-12 μm, preferably in the range of 6.50-10.5 μm. Injection molded sliding bearing component (1, 2, 3) according to one of the preceding claims, characterized in that the second surface (122, 222, 322) is not a sliding surface. Injection molded sliding bearing component (1) according to one of the preceding claims, characterized in that the second surface (122) is curved and that the data code mark (10) in the representation on the second surface corresponds to a projection from one plane onto the second surface is distorted. Injection molded sliding bearing component (1, 2, 3) according to one of Claims 9 to 14 , characterized in that - the first symbol elements (31) lie flush with the second surface (122, 222, 322) in an area adjacent to the data code mark (10, 20, 30); and / or - the second symbol elements (32) are formed by regions projecting with respect to the second surface (122, 222, 322), wherein a height difference between the first symbol elements (31) and the second symbol elements (32) is preferably less than 0.5 mm; and / or - that the data code marking (10, 20, 30) is provided in a recessed area relative to the second surface (122, 222, 322) and / or the second symbol elements (32) are arranged opposite the second surface (122, 222, 322) recessed areas are formed. Injection molded sliding bearing component (1, 2, 3) according to one of Claims 9 to 15 , characterized in that the second symbol elements (32) cause a stronger light scattering than the first symbol elements (31). Injection molded sliding bearing component (1, 2, 3) according to one of Claims 9 to 16 , especially after Claim 17 , characterized in that the second symbol elements (32) generate substantially isotropic light scattering and / or have an aperiodic surface profile. Injection molded sliding bearing component (1, 2, 3) according to one of the preceding claims, characterized in that the data code marking (10, 20, 30) is compatible with the 2D code, in particular including the visible surface of the first and second symbol elements (31, 32), is integrally made of the same plastic as the plastic body. Injection molded sliding bearing component (1, 2, 3) according to one of the preceding claims, characterized in that the data code marking (10, 20, 30) with the 2D code tool falling, in particular as direct marking with the injection molded sliding bearing component (1, 2 , 3) produced in the injection mold, and machine-readable without post-processing. Injection molded sliding bearing component (1, 2, 3) according to one of the preceding claims, characterized in that the data code marking (10, 20, 30) is a permanent marking and the data coded by the 2D code at least one manufacturer-specific URL or PURL Include identifier. Injection molded sliding bearing component (1, 2, 3) according to one of the preceding claims, in particular according to Claim 20 , characterized in that the encoded by the 2D code data encoded and / or slide bearing component-specific data content. Plain bearing, in particular linear plain bearings and / or radial plain bearings, comprising at least one injection-molded sliding bearing component (1, 2, 3) according to one of Claims 1 to 21 and a sliding member slidably supporting the injection-molded slide bearing member (1, 2, 3) or supported on the injection-molded slide bearing member (1, 2, 3), the sliding surface (121, 221, 321) of the injection-molded slide bearing member (1 , 2, 3) is in sliding contact with a surface of the sliding partner. Plastic injection molding tool, in particular of steel, for the production of injection-molded sliding bearing components (1, 2, 3), in particular according to one of Claims 1 to 21 , characterized in that the injection mold has a fixed predetermined marking area (53) for a 2D code, which comprises a number of first symbol areas (51) and a number of second symbol areas (52), which have a different surface finish, in particular a greater roughness than the first symbol areas (51). Plastic injection mold, in particular steel, after Claim 23 , characterized in that the first symbol areas (51) are generated by spark erosion. Plastic injection mold, in particular steel, after Claim 23 or24, characterized in that the second symbol areas (52) are produced by laser engraving of the injection mold.

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