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
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.
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).
An exemplary embodiment is shown in
Referring to
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
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
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.
Number | Date | Country | Kind |
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093124809 | Aug 2004 | TW | national |