INJECTION MOLDING METHOD WITH METALLIC PIGMENT USING MAGNETIC FIELD

Abstract

An apparatus for molding a part having ferromagnetic pigments is provided by the present disclosure. A magnetic field, generated by an electromagnet, is set up adjacent a wall of the part cavity that will define an A-surface of the part. A ferromagnetic pigment is combined with the resin. When the electromagnet is activated, the magnetic field attracts the ferromagnetic pigment to collect near the cavity wall that will define the A-surface. The apparatus of the present disclosure includes a mold, a part cavity formed in the mold, and an electromagnet positioned adjacent the part cavity whereby a magnetic field can be exerted on the part cavity. The electromagnet may be of any of several types, including a coil or a wire grid. The electromagnet may be embedded in the mold or may be placed adjacent to the mold.

Claims

1. An apparatus for molding a part, the apparatus comprising: a mold; a part cavity formed in said mold; and an electromagnet positioned adjacent said part cavity whereby a magnetic field can be exerted on said part cavity.

2. The apparatus for molding a part of claim 1, wherein said electromagnet is a coil.

3. The apparatus for molding a part of claim 2 further comprising a coil-receiving aperture formed in said mold.

4. The apparatus for molding a part of claim 1, wherein said electromagnet is a wire.

5. The apparatus for molding a part of claim 4, wherein said wire is part of a grid.

6. The apparatus for molding a part of claim 5, wherein said grid is embedded in said mold.

7. The apparatus for molding a part of claim 1, wherein said mold is composed of a metal.

8. The apparatus for molding a part of claim 7, wherein said metal is steel.

9. The apparatus for molding a part of claim 1, wherein the part being molded includes an A-surface and wherein said part cavity includes a wall that forms the A-surface of the part, said electromagnet being positioned adjacent said wall.

10. A system for forming a part having an A-surface, the system comprising: a mold; a part cavity formed in said mold, said part cavity having a wall that defines the A-surface of the part being molded; and an electromagnet positioned adjacent said wall that defines the A-surface of the part being molded.

11. The system for forming a part of claim 10, wherein said electromagnet is a coil.

12. The system for forming a part of claim 11 further comprising a coil-receiving aperture formed in said mold.

13. The system for forming a part of claim 10, wherein said electromagnet is a wire.

14. The system for forming a part of claim 13, wherein said wire is part of a grid.

15. The system for forming a part of claim 14, wherein said grid is embedded in said mold.

16. The system for forming a part of claim 10, wherein said mold is composed of a metal.

17. A method for molding a part comprising the steps of: forming a mold having a part cavity and an associated electromagnet; placing resin in said part cavity, said resin including a ferromagnetic pigment; energizing said electromagnet; and curing said resin.

18. The method for molding a part of claim 17, wherein said ferromagnetic pigment is introduced into said resin before said resin is placed in said part cavity.

19. The method for molding a part of claim 17, wherein said ferromagnetic pigment is introduced into said resin after said resin is placed in said part cavity.

20. The method for molding a part of claim 17, wherein said electromagnet is selected from the group consisting of a coil and a grid.

Description

DRAWINGS

[0014] In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

[0015] FIG. 1 is a diagrammatic illustration of a sectional view of a mold having metallic pigment dispersed in a resin and distributed throughout a part body according to the prior art;

[0016] FIG. 2 is a diagrammatic illustration of a sectional view of a mold having metallic pigment dispersed in a resin and concentrated in a surface of a part under the influence of a magnetic field according to the present disclosure;

[0017] FIG. 3 is a diagrammatic illustration of a sectional view of a mold having an electromagnet formed from coils of wire according to the present disclosure;

[0018] FIG. 4 is a diagrammatic illustration of a perspective view of the mold of FIG. 3 in which the mold has electromagnet formed from coils of wire according to the present disclosure;

[0019] FIG. 5 is a diagrammatic illustration of a sectional view of a mold having an electromagnet formed from a wire grid according to the present disclosure;

[0020] and

[0021] FIG. 6 is a diagrammatic illustration of a perspective view of the mold of FIG. 5 in which the mold has an electromagnet formed from a wire grid according to the present disclosure.

[0022] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

[0023] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0024] In the following figures, the same reference numerals will be used to refer to the same components. In the following description, various operating parameters and components are described for different constructed forms. These specific parameters and components are included as examples and are not meant to be limiting.

[0025] Referring to FIG. 1, a diagrammatic illustration of a sectional view of a mold 10 is illustrated according to the prior art. The mold 10 includes a part cavity 12 formed therein. A resin 14 having metallic pigment 16 dispersed therein is illustrated. As illustrated, the metallic pigment 16 is dispersed throughout the resin 14, resulting in wasted pigment since the metallic appearance is only needed on the A-surface. The wasting of metallic pigment is particularly an issue in the case where a very thick part is being molded. This approach to part molding also may result in undesirable flow marks or dark spots on the A-surface as the orientation of the metallic pigment 16 in the resin 14 cannot be controlled according to previous approaches to part molding.

[0026] The present disclosure overcomes the challenges faced by prior art approaches of molding parts with metallic pigment in the resin. Particularly, the present disclosure provides for the use of ferromagnetic pigment in resins and magnetic field adjacent the mold in the injection molding tool to thereby reduce the use of metallic pigment and, as a result, reduce manufacturing cost while providing an excellent A-surface that is free of flow marks and dark spots.

[0027] FIGS. 2 through 6 illustrate the system for molding parts according to the present disclosure relying on the presence of a magnetic field. In general, ferromagnetic pigment is attracted to a magnetic field. When a magnetic field is introduced to the cavity of tool while resin is still molten, the ferromagnetic pigment will move to the surface of the part. The ferromagnetic pigment may be added to resin before the resin is placed in the part cavity. Alternatively, the ferromagnetic pigment may be added to the resin after the resin is placed in the part cavity. This action is illustrated diagrammatically in FIG. 2 in which a mold 20 having a mold cavity 22 is shown. The mold 20 is typically composed of a metal, such as steel. A resin 24 therein is shown. Ferromagnetic pigment 26 is present in the resin 24. Because of the presence of an electromagnet 28 that generates a magnetic field 30 when energized, the ferromagnetic pigment 26 is concentrated adjacent the electromagnet 28 in an area 32 that, once molded, will become the A-surface 32 of the part.

[0028] By placing the electromagnet 28 relatively close to the mold cavity 22, the electromagnetic field 30 is strong enough to concentrate the ferromagnetic pigment 26 in the A-surface area 32. The electromagnetic 28 may be selectively energized or de-energized by a circuit-interrupting switch.

[0029] FIG. 2 illustrates a generic electromagnet 28. FIGS. 3 through 6 illustrate specific forms of the type of electromagnet that may be used in the system of the present disclosure. It is to be understood that the illustrated and discussed forms of the electromagnet are suggestive only and are not intended as being limiting.

[0030] FIGS. 3 and 4 illustrate one form of the system of the present disclosure in which the electromagnet is a coil. FIGS. 5 and 6 illustrate another form of the system of the present disclosure in which the electromagnet is a grid.

[0031] Referring to FIG. 3, a mold 40 is shown in cross section. A part cavity 42 is formed on the mold 40. The mold 40 includes wire coils 44 placed in holes strategically formed in the mold 40, typically formed of a metal such as steel. The number and placement of the wire coils 44 as shown in FIG. 3 is only suggestive and is not intended as being limiting.

[0032] In FIG. 4, the mold 40 is shown in perspective view. The mold cavity 42 is of a rectangular shape but can be of any shape as the rectangular shape is shown for illustrative purposes only. The wire coils 44 are embedded in the mold 40 at a location below and adjacent to the mold cavity 42.

[0033] As an alternative to wire coils, the electromagnet of the present disclosure may be a sheet of metal or may be a grid, such as is illustrated in FIGS. 5 and 6.

[0034] Referring to FIG. 5, a mold 50 is shown in cross section. A part cavity 52 is formed on the mold 50. The mold 50 includes a wire grid 54 that is illustrated in section view as well as in plan view in FIG. 5. The part cavity 52 may be of the one-piece type as shown in FIGS. 3 and 4 or may be of the two-piece variety. Regardless or the type of part cavity, the wire grid 54 is positioned in the mold 50 at a location below and adjacent to the mold cavity 52.

[0035] In FIG. 6, the mold 50 is shown in perspective view. The mold cavity 52 is of a rectangular shape but can be of any shape as the rectangular shape is shown for illustrative purposes only. The wire grid 54 is embedded in the mold 50 at a location below and adjacent to the mold cavity 52.

[0036] In use, a mold is formed having a part cavity and an electromagnet placed in a location adjacent the part cavity. A quantity of resin is placed in the part cavity, together with a quantity of ferromagnetic pigment. The electromagnet is energized, causing the ferromagnetic pigment to move in the direction of the electromagnetic, thus forming an area of concentrated pigment. This concentrated area is the A-surface once the part is cured. The result is a part free of flow marks and dark spots on the A-surface.

[0037] One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the present disclosure as defined by the following claims.

[0038] The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.