Method of forming a die

Abstract

A method for forming a die, including forming a pre-formed mold by providing a preliminary layer on a substrate and performing a micro-machining process on the preliminary layer. Due to the micro-machining process, the method can fabricate a pre-formed mold with high precision for forming a mold. The die is fabricated by the mold for performing a molding process to obtain a workpiece with a predetermined shape.

Description

BACKGROUND

The invention relates in general to a method of forming a die to obtain a workpiece with high precision.

Conventional molding processes are widely used in shaping workpieces. A mold is fabricated in which the profile of the mold is opposite to that of workpiece. The mold then presses the workpiece which is complete after removal from the die.

A conventional molding process is shown in FIG. 1. A mold material 10 is provided to form a mold 11 by performing a normal machining process. The machining process can include conventional methods such as drilling, milling, turning, or grinding, to manufacture the mold 11 which has a profile opposite to that of the workpiece. Next, the mold 11 is fixed on a die base 12 to form a die 1. The workpiece 2 is then pressed by the die 1. After removal from the die 1, the workpiece 2 has a predetermined shape.

The mentioned process has many advantages including rapid manufacturing products time, enabling mass production. Recently, elements required in mechanisms and apparatuses, however, with small size cannot be satisfied by the conventional methods because the mold is too small to be shaped thereby. The conventional methods such as drilling, milling, turning, or grinding and the machines corresponding thereto, such as drilling machine, milling machine, turning machine, or grinding machine, are restricted in precision accuracy. Generally, machining precision of the conventional skills is above 1 mm. In some machine tools for drilling, milling, turning, or grinding, precision of machining can be further enhanced. Due to the existed limitations, however, that workpieces manufactured by conventional methods do not conform to the desired precision.

SUMMARY

The invention provides methods of forming a die to obtain workpieces with high precision, satisfying the requirement of small size workpieces.

A method of forming a die for performing a molding process to obtain a workpiece with a predetermined shape, the method comprises providing a substrate; forming a pre-formed mold by providing a preliminary layer on the substrate and performing a micro-machining process on the preliminary layer; providing a mold material on the pre-formed mold to form a mold; and fabricating the die with the mold.

In an exemplary embodiment, the preliminary layer comprises photo-sensitive material and the micro-machining process comprises lithographic process, comprising providing a photo mask above the preliminary layer to form a masked module; exposing the masked module to radiation, wherein a portion of the preliminary layer is exposed to the radiation; and developing the preliminary layer to form the pre-formed mold. In the above mentioned method, the portion of the preliminary layer exposed to radiation or a portion of the preliminary layer unexposed to radiation is removed in the developing step.

In an exemplary embodiment, the micro-machining process comprises precision electrical discharge machining, laser machining or rapid prototyping machining.

In an exemplary embodiment, the rapid prototyping machining is selected from a group consisting of stereo lithography (SL), selected laser sintering (SLS), laser engineering net shaping, three dimensional printing (3DP), fused deposition modeling (FDM), laminated object manufacturing (LOM) and inkjet forming method.

In an exemplary embodiment, the mold material is provided on the pre-formed mold by electroforming or powder metallurgy forming.

In an exemplary embodiment, the molding process is selected from a group consisting of pressing, extruding, die casting, forging, rolling and injection molding.

In an exemplary embodiment, the mold material is nickel-based alloy or chromium-based alloy, selected from a group consisting of nickel cobalt, nickel phosphide, nickel cobalt phosphide, nickel tungsten, nickel rhenium, nickel palladium, nickel chromium, nickel carborundum phosphide, nickel graphite, and nickel manganese.

In an exemplary embodiment, Vickers Hardness Number of the mold is greater than 450HV and precision accuracy of the mold is less than 1 mm.

In an exemplary embodiment, further comprises performing a duration enhancing process on the mold or the die. The duration enhancing process is selected from a group consisting of heat treatment, surface coating, air cooling, and fluid cooling process.

In an exemplary embodiment, the surface coating process comprises coating a protection film on the die with a thickness of 1 to 8 um, the protection film is selected from a group consisting of aluminum nitride, aluminum titanium nitride, chromium nitride, aluminum carbide and diamond-like carbon (DLC).

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a conventional method of forming a die;

FIG. 2 is a schematic diagram of a method of forming a die according to the invention;

FIG. 3 is a schematic diagram of a lithographic process; and

FIG. 4 is a schematic diagram of another method of forming a die according to the invention;

DETAILED DESCRIPTION

An exemplary embodiment is shown in FIG. 2. In a method for forming a die of the invention, a substrate 35 is provided. The substrate 35 is a base for forming a pre-formed mold 36 with a micro-machining process. Preferably, the micro-machining process includes a lithographic process, precision electrical discharge machining or a laser machining. For a convenient and simple description, the lithographic process is given below as an example.

Referring to FIG. 3, a pre-formed mold 36 is formed by providing a preliminary layer 34 on the substrate 35. Preferably, the preliminary layer 34 is formed by deposition in a semiconductor process, but is not limited thereto. The preliminary layer 34 is made by a photo-sensitive material. A photo mask 37 is provided above the preliminary layer 34. A pattern on the photo mask 37 corresponds to the required pre-formed mold 36. A radiation 38 is provided on the photo mask 37. The pattern on the photo mask 37 allows parts of radiation 38 to pass through and further expose the preliminary layer 34. Preferably, the portion of the photo mask 37 allowing radiation 38 to pass through has the same profile as the required pre-formed mold 36, and vice versa, as long as the developer can be matched in the subsequent developing step. The developing step is then preformed in which a developer is used to remove the portion of the preliminary layer 34 exposed by radiation 38 (or the portion of the preliminary layer 34 unexposed to radiation 38), so that the preliminary layer 34 is formed to a pre-formed mold 36.

The lithographic process mentioned can manufacture a pre-formed mold 36 with high precision. Generally, the lithographic process is widely used in a semiconductor process to easily manufacture the pre-formed mold 36 with precision accuracy of less than 1 mm. Otherwise, the pre-formed mold 36 may be manufactured by precision electrical discharge machining, laser machining or rapid prototyping machining. The precision electrical discharge machining comprises providing a pre-formed mold material (not shown) in an electrical discharge machine to operate, such that a pre-formed mold 36 with precision accuracy of less than 1 mm is achieved. In the precision electrical discharge machining, however, the pre-formed mold material is limited to metal. The laser machining comprises providing a pre-formed mold material in a laser machine and requires a high energy laser to operate, such that a pre-formed mold 36 with precision accuracy of less than 1 mm is also achieved. In the laser machining, the type of the pre-formed mold material is not limited. Further, the rapid prototyping machining mentioned is selected from a group consisting of stereo lithography (SL) , selected laser sintering (SLS), laser engineering net shaping, three dimensional printing (3DP), fused deposition modeling (FDM), laminated object manufacturing (LOM) and inkjet forming method, achieving a pre-formed mold 36 with precision accuracy less than 1 mm.

Referring back to FIG. 2, after the pre-formed mold 36 is performed, a mold material (not shown) is provided on the pre-formed mold 36 to form a mold 31. As mentioned, the mold material may be provided on the pre-formed mold 36 by electroforming. The substrate 35 and the pre-formed mold 36 are placed in an electroforming machine, and the mold material is gradually filled on the pre-formed mold 36, forming the mold 31. Otherwise, the mold material may be provided on the pre-formed mold 36 by powder metallurgy forming. The substrate 35 and the pre-formed mold 36 are placed in a powder metallurgy forming machine, the powder of mold material is filled, and the processes of compression and sintering is performed, forming the mold 31.

Sequentially, a die 3 is fabricated by assembling the mold 31 and a die base 32. The die 3 can perform a molding process to obtain a workpiece 4. Preferably, the molding process is a pressing process. Namely, the die 3 is fixed on a pressing machine, so that the die 3 presses the workpiece 4 with the predetermined shape. The molding process is not limited to the above, an extruding, die casting, forging, rolling and injection molding process can also achieve the same result. The material of the mold 31 may be nickel-based alloy or chromium-based alloy, selected from a group consisting of nickel cobalt, nickel phosphide, nickel cobalt phosphide, nickel tungsten, nickel rhenium, nickel palladium, nickel chromium, nickel carborundum phosphide, nickel graphite, and nickel manganese, and Vickers Hardness Number of the mold is greater than 450HV, for forming a more durable mold 31. After the mold 31 is formed, a duration enhancing process such as heat treatment, surface coating, air cooling, or fluid cooling process is performed on the mold 31 or the die 3, so that the structure of the mold 31 is enhanced to facilitate the molding process. That is, the duration enhancing process can raise the reliability of the mold. The surface coating process mentioned comprises a protection film coated on the die 3 or the mold 31. The protection film is selected from a group consisting of aluminum nitride, aluminum titanium nitride, chromium nitride, aluminum carbide and diamond-like carbon (DLC), with a thickness of 1 to 8 um, to enhance the structure of the mold 31. The duration enhancing process is important to the die 3, and especially to the workpiece 4 with precision less than 1 mm. The mold 31 may be broken during the molding process if the strength of the mold 31 is adequate due to the small size. Preferably, the material of the workpiece 4 is selected from copper, copper alloy, aluminum, aluminum alloy, nonmetal and a combination thereof, not limited thereto.

Another exemplary embodiment is shown in FIG. 4. The embodiment is similar to that previously described. The different is that only the protrusion of the mold 31 is formed during fabricating the mold 31. As the mold 31 is connected to the substrate 35, the mold 31 and the substrate 35 is assembled with the die base 32 to form the die 3. The die 3 then performs a molding process to obtain a workpiece 4. In this embodiment, the effect same as the mentioned embodiment is achieved and further reduces the numbers of the steps in method and costs associated with forming the mold 31 with the mold material.

As mentioned above, the invention increases the precision of the mold to obtain a workpiece with high precision, satisfying the requirements of small size products. The pre-formed mold is formed by a micro-machining process. Due to the micro-machining process, the machining precision is enhanced. The method can achieve the object of obtaining a manufactured workpiece with high precision.

While the invention has been described by way of example and in terms of preferred embodiments, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.

Claims

1. A method of forming a die for performing a molding process to obtain a workpiece with a predetermined shape, the method comprising:

providing a substrate;

forming a pre-formed mold by providing a preliminary layer on the substrate and performing a micro-machining process on the preliminary layer;

providing a mold material on the pre-formed mold to form a mold; and

fabricating the die with the mold.

2. The method as claimed in claim 1, wherein the preliminary layer comprises a photo-sensitive material and the micro-machining process comprises a lithographic process, comprising:

providing a photo mask above the preliminary layer;

providing a radiation on the photo mask, wherein a portion of the preliminary layer is exposed by the radiation; and

developing the preliminary layer to form the pre-formed mold.

3. The method as claimed in claim 2, wherein the portion of the preliminary layer exposed to the radiation is removed in the developing step.

4. The method as claimed in claim 2, wherein a portion of the preliminary layer unexposed to the radiation is removed in the developing step.

5. The method as claimed in claim 1, wherein the mold material is provided on the pre-formed mold by electroforming.

6. The method as claimed in claim 1, wherein the mold material is provided on the pre-formed mold by powder metallurgy forming.

7. The method as claimed in claim 1, wherein the die is fabricated by assembling the mold with a die base.

8. The method as claimed in claim 1, wherein the die is fabricated by assembling the mold and the substrate with a die base.

9. The method as claimed in claim 1, wherein the molding process is selected from a group consisting of pressing, extruding, die casting, forging, rolling and injection molding.

10. The method as claimed in claim 1, wherein the mold material is selected from a group consisting of nickel cobalt, nickel phosphide, nickel cobalt phosphide, nickel tungsten, nickel rhenium, nickel palladium, nickel chromium, nickel carborundum phosphide, nickel graphite, and nickel manganese. nickel-based alloy and chromium-based alloy.

11. The method as claimed in claim 10, wherein Vickers Hardness Number of the mold is greater than 450HV.

12. The method as claimed in claim 10, wherein precision accuracy of the mold is less than 1 mm.

13. The method as claimed in claim 1, further comprising performing a duration enhancing process on the mold or the die.

14. The method as claimed in claim 13, wherein the duration enhancing process is selected from a group consisting of heat treatment, surface coating, air cooling, and fluid cooling process.

15. The method as claimed in claim 14, wherein the surface coating process comprises coating a protection film on the die with a thickness of 1 to 8 um, the protection film is selected from a group consisting of aluminum nitride, aluminum titanium nitride, chromium nitride, aluminum carbide and diamond-like carbon (DLC).

16. The method as claimed in claim 1, wherein the material of the workpiece is selected from copper, copper alloy, aluminum, aluminum alloy and nonmetal and a combination thereof.

17. The method as claimed in claim 1, wherein the micro-machining process comprises precision electrical discharge machining.

18. The method as claimed in claim 17, wherein a pre-formed mold material for the pre-formed mold is provided in an electrical discharge machining center to perform precision electrical discharge machining.

19. The method as claimed in claim 1, wherein the micro-machining process comprises laser machining.

20. The method as claimed in claim 19, wherein a pre-formed mold material for the pre-formed mold is provided in a laser machining machine to perform laser machining.

21. The method as claimed in claim 1, wherein the micro-machining process comprises rapid prototyping machining.

22. The method as claimed in claim 21, wherein the rapid prototyping machining is selected from a group consisting of stereo lithography (SL), selected laser sintering (SLS), laser engineering net shaping, three dimensional printing (3DP), fused deposition modeling (FDM), laminated object manufacturing (LOM) and inkjet forming method.