WO2009077400A2 - Method for manufacturing molded articles - Google Patents

Abstract

The invention relates to a method for manufacturing molded articles with a tool which can be opened and closed, wherein a flowable raw material in the tool receives a target form and is then cooled, wherein a decorative or print image is applied prior to introduction of the flowable to at least a partial area of a shaping section of the open tool by means of a printing procedure, wherein the applied decorative or print image after cooling of the flowable raw material is connected solidly and inseparably to the molded article.

Description

 Method for producing molded parts

The invention relates to a method for producing molded parts according to the preamble of claim 1.

From EP 1 115 547 Bl a method for producing coated plastic moldings is known, in which a composite plastic molding is produced. The composite plastic molding has at least one layer of a web material and a plastic body. Here, a web material is first placed between mold halves of an open injection mold. Subsequently, the web material is deformed by closing the tool. The deformed web material is held by means of negative pressure on one side or overpressure on the other side. Plasticized plastic is injected into a residual tool cavity and the tool is opened to a predetermined position. The web material may optionally have a decor, for example for furniture surfaces. This method has proven particularly useful in the production of a design that is essentially identical with respect to the surface decoration. With the disclosed method, however, it is only very cumbersome to produce components which, while not different in their shape, are intended to have a component-specific, individual décor. DE 10 2004 050 290 A1 discloses a method and a device for producing differently coated plastic moldings. In this process, decorative films are prepared, which are produced individually before the injection molding process outside the tool. Such a decorative film is inserted into the opened tool and back-injected by means of a plasticized plastic compound. Various decorative films are stored in different storage containers provided and are inserted by an industrial robot as needed in the injection mold.

This method has also proven itself, but it is necessary to further reduce the number of reservoirs and the cost of preparing decorative films. In particular, the limited number of different decors and / or codes should be avoided.

The object of the invention is therefore to provide a method for the production of molded parts, with which it is possible, without stocking of prefabricated decorative films of different types to produce moldings on which an individual appearance and / or individual identification can be applied. In particular, it should allow the process to produce shaped parts with the batch size 1 individually designed or coded. Furthermore, a free choice of the decoration / the label to be guaranteed immediately before the production of the molding. Furthermore, molded parts should be produced in any order. Furthermore, a simplification of logistics costs, in particular by lower storage for customer-specific parts to be achieved. In addition, reaction times to customer requests regarding component design should be accelerated. These objects are achieved by a method having the features of claim 1. Advantageous embodiments are specified in the subclaims.

The inventive method is characterized in that a decorative or typeface image to be produced is applied by means of a printing process directly in the mold cavity on at least a portion of a forming portion of the mold cavity. Under Werkzeugkavität here is to be understood in particular a metal surface of the mold within the Formteilausnehmung. As applying to a portion of the mold cavity according to the invention, the application of a printed image in the open tool to a support film, which is located on the wall of the Werkzeugkavität understand. It is therefore to be understood with this formulation both a direct application to the surface of the mold cavity as well as an indirect application to a carrier medium, which is located in the mold cavity and rests against the Werkzeugkavität.

Essential to the invention is thus that the decorative or typeface, which is ultimately mounted on the molded part to be produced within the open tool is generated. Here, the method differs significantly from the prior art, are provided in the decorative films outside of the tool with decor and placed with applied decor image in a tool and back-injected.

According to the invention, it has been recognized that certain printing media, for. For example, there are printing varnishes which are suitable for such an application in the tool without the marbling and smearing effects occurring. Particularly suitable for this purpose are pressure-resistant and temperature-resistant lacquers, in particular acrylic lacquers Base of polymethyl methacrylates. These paints combine in the tool during injection molding or pressing back with plastic melt or plasticized plastic mass during cooling with this, so that the printed image after cooling of the molding is firmly and inseparably connected to the molding and this characterizes, decorated or otherwise designed.

Preferably, a computer-controlled or computer-aided customizable printing method is used, which z. B. in the manner of an ink jet printing method, works in the manner of a thermal transfer printing process or in the manner of a pad printing process.

It is particularly preferred that the decorative or typeface image is an individual or unique pattern or a pictogram, or that the decorative or typeface image is a serial number, batch number or otherwise code that codes and identifies the molded article.

As a result, photos of objects or persons, for example, which are introduced by means of printing processes into the tool cavity of the mobile telephone shell, can be generated on customer-specific and person-individualized mobile telephone housing shells. It is also very advantageous, for example, for documentation and security reasons, to associate each manufactured plastic part with an individual serial number, so that a subsequent documentation forgery-proof and with little effort is possible.

The method according to the invention is suitable for all plastic molding processes and forming processes for molded parts. The process of the invention is preferably designed as a plastic injection molding or plastic injection molding process. In principle, however, this method is also conceivable for other raw masses to be processed, provided that sufficiently resistant printing media / lacquers or the like are or will be available in future with regard to the temperature and pressure loading. From the inventive principle, this method is also under the above condition for the manufacture of moldings from z. As metal or glass used.

According to a particular embodiment of the invention, the decorative or typeface image is applied to a carrier medium which is located in the tool cavity. Such a carrier medium may be, for example, a release film or a carrier film for the decorative or typeface image, which is located in the tool cavity in the opened tool. An advantage of this measure is that regardless of the decorative or typeface to be produced, a unit or otherwise common web or carrier material can be used, which is inserted into the mold cavity and formed at least in the area to be printed on the mold cavity. On this carrier medium according to the invention then the decorative or typeface is applied.

In a first variant, the film remains in the mold after the spray or injection-press process. The decorative or typeface image on the foil loosens during the production process and combines with the plasticized plastic mass or the plastic melt. In this case, the foil inserted in the tool acts as a separating film or separating medium. In a second variant of this embodiment, the film remains after the manufacturing process of the molding on the molding and is cohesively with this prevented. In this embodiment, the decorative or typeface is thus located on the finished molded part between the carrier film and the molded part body, so that the carrier film can act as a scratch protection for the decorative or typeface image of the finished molded part.

For special optical or tactile surfaces, it may be expedient to use as the carrier medium, a textile fabric, a carpet or leather or similar mats and / or sheet-like flat body.

In particular, in the case of three-dimensionally strongly contoured or relief-like surface regions which are to be provided with the decorative or typeface image, it is advisable to use a industrial robot with a print head or another device by means of which a printed image is produced in the tool cavity constant distance to the mold cavity or to the surface on which the print image is to be applied to move.

A further possible embodiment of the method according to the invention provides that first of all a decorative or typeface image is applied to a partial region of a tool cavity, which is covered by means of a cover film prior to the injection of the flowable raw material (plastic melt, plasticized plastic compound). In this embodiment, therefore, the carrier film is located on the finished molding between the decorative or typeface and the molding body. In this case, it is of particular advantage that the film with which the printed image is covered in the tool can be optimized in terms of its adhesion properties to the molded part material and to decorative or typeface material and thus an improved connection between the decorative image and the molded part body can be produced , In particular, in a large-scale decor and / or typeface, it is advantageous if the printing medium, for. B. the printing varnishes are applied over a large area and in particular have chemical properties that facilitate the detachment of the finished molded part of the Werkzeugkavität. In such a case, the printing medium acts in addition to the formation of the decorative or typeface image as a separation medium or release agent between the molding of the Werkzeugkavität.

In a particularly simple manner, electrically conductive patterns or patterns can be applied to a component if electrically conductive ink is used for the printing medium. As a result, with the method according to the invention, in particular in a simple manner, a heatable mirror carrier or, for example, heatable window panes and / or lens panes of a motor vehicle can be produced.

If there is a requirement that the finished molded part should have darkening properties, it is advisable to use a so-called LCD color for the printing medium, which can be darkened at least partially by electrical activation. This embodiment of the method according to the invention is particularly suitable for producing fully and semi-transparent molded parts and electrically controllable, darkened molded parts.

To improve the mechanical connection between the printing medium and the molded part, it has been proven, after the application of the printing medium, ie mechanically roughen the printing medium layer by means of a laser and / or structure and / or to activate by means of energy input after producing the decorative or typeface image. As a result, by very small and fine bumps increased binding forces between the printing medium layer and the molded part body is generated, so that the connection of these two layers is improved.

Activation of the surface can, for. B. by laser or plasma treatment or by flame treatment. Here are broken up by the introduced energy bonds, which then make new connections with the carrier again.

In particular, the method according to the invention is suitable for use in a so-called multi-component production process for plastic molded parts. In this case, for example, in a first step, a transparent molded body (first component) is sprayed onto which the decorative or typeface image is applied in a next step, wherein the first component remains in the tool during this time. In a further step, after the application of the decorative or typeface image by injection or pressing in of flowable raw material, another molded part is applied, overmolded or back-injected. This molding is then considered as a second component. As a result, there is thus a molded part, which is formed from two components, for example, two different materials, between which a decorative or typeface is embedded. This embodiment is particularly suitable for components in which the first component is a transparent surface or a transparent surface layer. In this case, in particular the applied decorative or typeface on the finished component is visible.

Of course, the method of this multi-component embodiment is also suitable for materials of the first and second components, which are not transparent. In this embodiment, therefore, a decorative or typeface image is embedded between two non-transparent, ie opaque, plastics and is thus not visible on the finished molded part. Such species of embedded, invisible images or writings can serve as an authenticity feature, for example for combating claims resulting from counterfeiting, in particular for security-relevant components.

In the following the invention will be explained in more detail by way of example with reference to the drawing. It shows:

FIG. 1 shows schematically a flow diagram of a method according to the invention.

A method according to the invention for producing molded parts is designed, for example, as a plastic injection molding process and runs cyclically from the typical process, with a status of the process being selected for the description of this example as the start of the cyclical process, in which an opened tool (step 100) is in an empty, ready-to-operate state an injection molding machine is used. Such an injection molding tool consists of at least two mutually movable mold halves, which enclose a tool cavity between them. The cavity of the mold is to be understood as meaning a cavity in which, by means of an injection process or by means of an extrusion process, flowable raw material, e.g. Plastic melt or plasticized plastic is injected and injected by filling the mold cavity to form a molded part or pressed. Such an open tool has, for example, metallic mold surfaces and often has a three-dimensional contour in shaping areas.

According to the invention, a decorative and / or typeface image is now applied to the wall of the tool cavity on at least one subarea of shaping sections of the molding tool by means of a printing method (step 200). The up- Carrying the printed image is done for example by means of an inkjet, thermal transfer or pad printing process. In an inkjet printing process, for example, a printhead can be moved by motor in the manner of a commercial inkjet printer along linear guides and can apply a printed image by means of a suitable printing medium to the subregion of the mold cavity in question. If the part of the tool cavity to be imprinted has a 3-dimensional contour, e.g. B. relief-like structure, it is particularly advantageous to perform an ink jet print head, for example by means of an industrial robot with a constant distance to the printing surface of the Werkzeugkavität so that a sharp print image is formed.

Acrylic coatings based on polymethylmethacrylate have proven to be suitable printing media in particular. Such coatings have a high resistance to compression deformation under high temperature action, as they typically prevail in a plastic injection molding tool. By means of such a printing process in the tool cavity "into" it is possible to completely save a stockpiling of suitably pre-printed insert films or Einlageträgermedien. After applying the decorative or typeface image, the tool is closed (step 300). Due to possibly existing suitable tempering, z. B. cooling or Aufheizeinrichtungen in the field of decorative printing manages the printed image to dry quickly or cure. In a next step, for example, when the tool is closed, a plasticized plastic material, eg. B. injected a plastic melt into the mold and thus the pressure, ie the decorative or typeface back-injected (step 400). Upon cooling of the melt, the melt of the molding combines with the paint of the printed image to form a one-piece component. In the course of the molding is in the usual way cooled (step 500), the tool opened (step 600) and the molded part taken along with the decorative or typographic imprint (step 700). Possibly. For example, after removal of the finished molded part, the area in which a decorative or typeface imprint is to take place for the next molded part can be tempered by means of suitable tempering devices to temperatures suitable for printing image application. As a result, a pre-hardening and / or curing of the introduced pressure medium (paint / color) can be achieved. Such curing can also be effected by UV radiation.

In the method according to the invention, it is of particular advantage that it is now possible for the first time to be able to inexpensively produce individual plastic parts with batch size 1 by means of an integration of decoration directly into the injection molding process in a simple manner. In this case, it has proven particularly useful to apply the decorative or typeface image directly to the tool cavity by means of a print head and to subsequently inject the resulting "image layer". Thus, comparable to a office printer, the design of the individual print job can be assigned directly to each individual molded part and changed from molded part to molded part. Likewise, additional information, logos, serial or production numbers, customer names or the like can be displayed directly on the molded part.

The principle according to the invention is not left when the pressure in the open mold is applied to a film and the film is back-injected in the manner of a transfer decoration. Here, the film serves as a release agent for Werkzeugkavität. It is equally possible to leave the printed film on the molded part, so that it optionally forms a scratch-resistant layer for the molded part. Especially at high melt temperatures and component geometry related high Shear loads in the printed area is also conceivable that the decorative or typeface image is applied directly to the mold cavity and a film is applied between the printed image and the molded part in order to avoid a flow of the printed image. A connection between the pressure, the protective film and the molded part takes place during cooling during injection molding by temperature and pressure.

In particular, the feeding of printheads by means of industrial robots allows printing on deep cavities (eg cup walls or cup bases). Due to the stamp-like printing technique of a pad printing, a relatively deep geometry can also be printed by means of this method. However, a pad printing method is only limited suitable for creating individual print images. For example, a variety of print images could be generated using suitable pad printing stamps on a turret, i. H. a stamp turret, wherein certain printing stamps are selected and used by machine.

Furthermore, in the invention of particular advantage that a completely free, individual decor or typeface choice for each molding in any arbitrary order can be realized, since a control of the printing process via a standard personal computer is possible. This results in lower logistics requirements, since only a small storage for customer-specific parts is required. In addition, reaction times are shortened to special customer requirements.

If possible, a mobile phone tray with a personal photo or a personal graphic representation or also of individualizable inventory codes of commercially used devices, eg. B. mobile phones. Another advantage of the It is invention that the method is possible in a simple and cost-effective manner in already existing plant technology based on a multi-component system. In addition, the invention proposes to give the printing ink or the printing matrix (the printing medium) additional properties, in which, for example, electrically conductive paint for the production of heatable parts or so-called LCD colors are added, by means of which the electrical signal generated Moldings are darkened or transparent again switchable.

Furthermore, after the application of the print, the printing ink can be patterned by means of a laser, as is usual in the production of prototypes. The resulting miniature grid on the component increases the interaction at the interface between the printed image and the molded part, so that on the one hand a defined refraction of light for the production of anti-reflective parts is possible or a higher mechanical bond between the printed image and the molded part can be achieved ,

Claims

claims 1. A method for producing molded parts with an openable and closable tool, wherein a flowable raw material in the tool receives a desired shape and is then cooled, characterized in that prior to introduction of the flowable raw mass at least on a portion of a forming portion of the opened tool , d. H. on a portion of the mold cavity by means of a printing process a decorative or typeface is connected in a molding process with the flowable raw material and is applied, wherein the applied decorative or typeface image is firmly and inseparably connected to the molding after cooling the flowable raw mass. 2. The method according to claim 1, characterized in that the printing process an individualizable printing process, for. An ink jet printing process, a thermal transfer printing process or a pad printing process. 3. The method according to claim 1 or 2, characterized in that the printing method is performed computer assisted. 4. The method according to any one of the preceding claims, characterized in that the decorative or typeface is an individual and unique pattern or a pictogram. 5. The method according to any one of the preceding claims, characterized in that the decorative or typeface is a serial number, a batch number or otherwise, the molding identifying code. 6. The method according to any one of the preceding claims, characterized in that the flowable raw material is plasticized plastic or plastic melt. 7. The method according to any one of the preceding claims, characterized in that the method is a plastic injection molding method or a Kunststoffspritzpressverfah- ren. 8. The method according to any one of the preceding claims, characterized in that the decorative or typeface is applied to a carrier medium located in the tool. 9. The method according to any one of the preceding claims, characterized in that the carrier medium of a tool wall is adapted at least in the partial region of the shaping portion and adjacent to this film. 10. The method according to any one of the preceding claims, characterized in that the carrier medium is a textile fabric, a carpet or leather. 11. The method according to any one of the preceding claims, characterized in that a print head is moved by means of a robot during the printing process corresponding to the tool surface at a constant distance to this. 12. The method according to any one of the preceding claims, characterized in that the decorative or typeface comprises characters and / or image representation. 13. The method according to any one of the preceding claims, characterized in that the printing medium used to produce the decorative or typeface acrylic paints, in particular based on PMMA (polymethyl methacrylate) are used. 14. The method according to any one of the preceding claims, characterized in that the carrier medium after the forming process remains in the tool and the decorative or typeface of a previous Produktionszyklus- ses is completely detached from the carrier medium. 15. The method according to any one of the preceding claims, characterized in that the carrier medium is firmly connected to the molding and serves as a scratch protection for the surface thereof. 16. The method according to any one of the preceding claims, characterized in that at increased, expected pressure and / or shear stress in the molding process, the decorative or typeface is applied directly to the portion of the tool (the Werkzeugkavität) and covered with a protective film. 17. The method according to any one of the preceding claims, characterized in that by pressure and temperature influence the decorative or typeface with the protective film and the protective film is connected to the molding. 18. The method according to any one of the preceding claims, characterized in that the decorative or typeface image is formed multi-colored. 19. The method according to any one of the preceding claims, characterized in that the pressure medium acts as a release agent. 20. The method according to any one of the preceding claims, characterized in that the decorative or typeface is a wood, aluminum or other surface replica. 21. The method according to any one of the preceding claims, characterized in that the printing medium is an electrically conductive paint. 22. The method according to any one of the preceding claims, characterized in that the molded part is a heated molding, for. B. is a mirror support or a vehicle window. 23. The method according to any one of the preceding claims, characterized in that the printing medium is an LCD color, so that printed areas of the molded part are controllably darkened. 24. The method according to any one of the preceding claims, characterized in that the printing medium is structured by means of laser. 25. The method according to any one of the preceding claims, characterized in that the method according to one or more of the preceding claims is part of a multiple component injection molding process, wherein first in a first step, a transparent surface layer (first component) is produced, then the cooled transparent surface layer by the inventive method according to claim 1 to 24 is printed and then another part (second component) formed, for. B. is injected.