METHOD OF MANUFACTURING A MOLD FOR INJECTION MOLDING

Abstract

A method is provided for manufacturing a mold for injection molding, especially for injection molding of optical components of automotive lighting devices. The method includes at least the following steps: providing a mold body, laser milling a pattern into a surface of the mold body, and coating the surface of the mold body by electroless nickel plating.

Claims

1. A method of manufacturing a mold for injection molding, the method comprising at least the following steps: providing a mold body, laser milling a pattern into a surface of the mold body, and coating the surface of the mold body by electroless nickel plating.

2. The method according to claim 1, wherein after coating, the mold is heat treated at a temperature in the range of 200° C. to 400° C. for a period in the range of 1 hour to 10 hours.

3. The method according to claim 1, wherein laser milling generates the pattern with a spatial resolution in the range of 1 μm to 10 μm.

4. The method according to claim 1, wherein the coating of the surface generates an electroless nickel coating with a thickness in the range of 2 μm to 20 μm.

5. The method according to claim 1, wherein the mold body is provided from a metallic material.

6. A mold for injection molding, wherein the mold is manufactured by a method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Reference is now made more particularly to the drawings, which illustrate the best presently known mode of carrying out the invention and wherein similar reference characters indicate the same parts throughout the views.

[0016] FIG. 1 is an illustration of a cross-section of a mold body according to a first step of the inventive method.

[0017] FIG. 2 is a illustration of a cross-section of a mold body according to a second step.

[0018] FIG. 3 is an illustration of a cross-section of a mold body according to a third step.

DETAILED DESCRIPTION OF THE INVENTION

[0019] Providing 100 the mold body 1 is illustrated in FIG. 1 as the first step of the inventive method. The mold body 1 is advantageously machined from a tool steel by means of milling and/or electrical discharge machining. The surface 11 is oriented towards the cavity of the mold and thus has to be functionalized according to the inventive method in order to provide the desired surface quality of the parts to be molded. The topography of the surface 11 of the as-provided mold body 1 is determined by the machining process, namely the surface waviness and the different orders of surface roughness.

[0020] FIG. 2 illustrates the second step of the inventive method, namely laser milling 200 a pattern 12 into the surface 11 of the mold body 1. To this end, the laser beam 3 travels over the surface 11 along programmed trajectories and yields a local material ablation at a high spatial resolution, e.g., in the range of 1 μm to 10 μm. The laser beam 3 typically operates in pulsed mode, e.g., with femtosecond pulses. Advantageously, a multi-beam laser unit is applied for high surface ablation rates. The pattern 12 in the example of FIG. 2 features the micro-cavities 13, which exhibit hemispherical shapes and are equally spaced in a periodic arrangement. Such a pattern 12 is for instance dedicated to mold an optical component with a surface array of micro-lenses. Beyond the example illustrated here, laser milling is appropriate to generate a vast variety of pattern on complex three-dimensional mold body surfaces for various applications, e.g., micron-sized pattern for molded parts with light-diffracting or light-diffusing properties or for holographic applications.

[0021] FIG. 3 illustrates the third step of the inventive method, namely coating 300 the surface 11 of the mold body 1 by electroless nickel plating, finally forming the inventive mold 1000. The nickel or nickel alloy coating 2 features a thickness 20 advantageously in the range of 2 μm to 20 μm. The microscopic pattern 12 is preserved by the coating 2, but the highest order, nanoscale roughness of the surface 11 of the mold body 1 right after laser milling 200 is advantageously smoothed and the surface 21 of the coating 2 exhibits high brilliance.

[0022] Depending on the detailed plating process, the coating 2 comprises pure nickel or a nickel alloy, e.g., an alloy comprising phosphorus or boron. The coating 2 can additionally comprise incorporations of co-deposited ceramic particles. Advantageously, after the process of coating 300 the mold 1000 is subject to a heat treatment in order to maximise the hardness and thus wear resistance of the coating 2. Hardness levels above 75 HRC can be typically obtained by a heat treatment at a temperature in the range of 200° C. to 400° C. for a period in the range of 1 hour to 10 hours.

[0023] The inventive mold 1000 is thus characterized by the combination of a precisely laser patterned surface with a coating providing brilliant gloss and wear resistance. The inventive mold 1000 is therefore especially appropriate to comply with high surface quality standards for injection molding of optical components, e.g., of automotive lighting devices.

[0024] The present invention is not limited by the embodiment described above, which is represented as an example only and can be modified in various ways within the scope of protection defined by the appending patent claims. [0025] List of Numerals [0026] 1000 mold [0027] 1 mold body [0028] 11 mold body surface [0029] 13 pattern [0030] 13 micro-cavity [0031] 2 coating [0032] 20 coating thickness [0033] 21 coating surface [0034] 3 laser beam [0035] 100 providing the mold body [0036] 200 laser milling into the mold body surface [0037] 300 coating the mold body surface