US20060086614A1

US20060086614A1 - Reinforced and thickened mold insert and method of manufacturing the same

Info

Publication number: US20060086614A1
Application number: US10/968,981
Authority: US
Inventors: Chia-Hua Chang; Jen-Chin Wu; Ming-Jen Wang
Original assignee: CHUNG SHAN INSTIUTTE OF SCIENCE AND TECHNOLOGY
Current assignee: CHUNG SHAN INSTIUTTE OF SCIENCE AND TECHNOLOGY
Priority date: 2004-10-21
Filing date: 2004-10-21
Publication date: 2006-04-27

Abstract

A reinforced and thickened mold insert and a method of manufacturing the same include the procedures of: first, providing an original mandrel that has an electroformed metal mold insert; next, forming a plurality of protrusive or indented coupling reinforced sections on the electroformed metal mold insert; finally forming a thickened metal layer on the electroformed metal mold insert and the coupling reinforced sections by metal spraying. The coupling reinforced sections can increase the bonding power between the electroformed metal mold insert and the thickened metal layer.

Description

FIELD OF THE INVENTION

The present invention relates to a reinforced and thickened mold insert and a method of manufacturing the same and particularly to a reinforced and thickened mold insert adopted for use in precise electroforming and a method of manufacturing the same.

BACKGROUND OF THE INVENTION

Electroforming is an electroplating technique to fabricate a thick layer of metal shell mold on a mandrel, then peel off the metal shell from the mandrel to become a duplicate of the mandrel and finish by machining and trimming. It can be used to produce precise and complicated molds in large quantity that are difficult to fabricate by conventional machining or take too much manpower.
The duplicate of the mandrel may reach the precision of 2.5 μm and the surface resolution can reach 0.02˜0.05 μm. Hence this molding technique is desirable for fabricating molds used in production of CDs, reflection sheets of car lights, light guiding plates of liquid crystal displays and the like.
However, in the conventional electroforming techniques, depositing speed of electroforming metal is in the range of 0.06˜0.5 mm/hr. Fabrication time could last weeks or even months. Moreover, the corners of the mandrel have uneven electric line distribution. This could result in uneven thickness of the electroformed shell and make machining in the follow on processes difficult.
Therefore the present invention aims to provide a reinforced and thickened mold insert and a method of manufacturing the same to overcome the aforesaid problems.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide a reinforced and thickened mold insert and a method of manufacturing the same to enhance the mechanical strength of the mold insert and increase the bonding power between the thickened layer and the electroformed layer.
In order to achieve the foregoing object, the reinforced and thickened mold insert according to the present invention mainly has a plurality of protrusive coupling reinforced sections on the surface of an electroformed metal mold insert, then forms a thickened metal layer on the electroformed metal mold insert and the coupling reinforced sections by metal spraying. The coupling reinforced sections are planted in the thickened metal layer, thus the bonding power between the electroformed metal mold insert and the thickened metal layer increases. It also resolves the problems of uneven thickness of the electroformed layer and deformation of the electroformed layer caused by a thermal effect during metal spraying for thickening.
The method for manufacturing the reinforced and thickened mold insert mainly includes the following procedures:
First, provide an original mandrel and submerge the original mandrel in an electroforming solution to form an electroformed metal mold insert.
Next, form a plurality of coupling reinforced sections on the surface of the electroformed metal mold insert to increase the structural strength between the electroformed metal mold insert and a thickened metal layer formed in the later process. As the coupling reinforced sections are formed on the surface of the electroformed metal mold insert and are planted in the thickened metal layer, the bonding power between the electroformed metal mold insert and the thickened metal layer increases.
Then separate the original mandrel and the electroformed metal mold insert. Finally form a thickened metal layer on the electroformed metal mold insert and the coupling reinforced sections by metal spraying to finish the fabrication.
The coupling reinforced sections may be integrally formed on the electroformed metal mold insert or may be screws bonded to the electroformed metal mold insert as long as they are protrusive from the electroformed metal mold insert.
There is no limitation on the material of the electroformed metal mold insert and the thickened metal layer. When in use, a complete mold may be formed by fastening the thickened mold insert of the invention to a mold seat.
Before proceeding the metal spraying, an interface metal layer may be formed on the electroformed metal mold insert and the coupling reinforced sections by metal spraying according to requirements to increase the key bonding strength of the two. Moreover, a metal mesh may be added in the thickened metal layer to increase the tensile strength in horizontal direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the flow chart of the manufacturing method of the reinforced and thickened mold insert of the invention.
FIG. 2 is a schematic view of embodiment 1 of the reinforced and thickened mold insert of the invention.
FIG. 3 is a schematic view of embodiment 3 of the reinforced and thickened mold insert of the invention.
FIG. 4 is a schematic view of embodiment 5 of the reinforced and thickened mold insert of the invention.
FIG. 5 is a schematic view of embodiment 6 of the reinforced and thickened mold insert of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Refer to FIG. 1 for the process flow of the manufacturing method of the reinforced and thickened mold insert of the invention.
First, provide an original mandrel (step 100); next, submerge the original mandrel in an electroforming solution to form an electroformed metal mold insert (step 110).
Next, form a plurality of coupling reinforced sections on the surface of the electroformed metal mold insert (step 120) to increase the structural strength between the electroformed metal mold insert and a thickened metal layer formed in the later process.
The coupling reinforced sections may be formed in many ways. For instance, deposit a plurality of silver paste spots on selected locations of the surface of the electroformed metal mold insert and coat an anti-plating paste on other portion, then submerge the entire original mandrel in an electroplating solution to deposit a layer of metal film on the silver paste spots. The protrusive silver paste spots may serve as the coupling reinforced sections. Another approach is to bond screws to the surface of the electroformed metal mold insert through the silver paste, then submerge the entire original mandrel in the electroplating solution to deposit a layer of metal film on the screws. The protrusive screws also may serve as the coupling reinforced sections. Hence different materials or elements may be coupled with different fabrication methods to form the coupling reinforced sections on the surface of the electroformed metal mold insert.
The coupling reinforced sections are formed on the surface of the electroformed metal mold insert, and are planted in the thickened metal layer, thus can improve the bonding power between the electroformed metal mold insert and the thickened metal layer.
Next, separate the original mandrel and the electroformed metal mold insert (step 130); form a coarse surface on the surface electroformed metal mold insert (step 140) by blasting or the like, to facilitate fabrication of a key bonding layer on the surface of the electroformed metal mold insert.
Form the key bonding layer on the surface of the electroformed metal mold insert (step 150) to increase the key bonding strength of the metal during electroforming to enable the electroforming metal to attach to the surface of the electroformed metal mold insert.
Finally, form the thickened metal layer on the electroformed metal mold insert by metal spraying (step 160) to finish the fabrication of the reinforced and thickened mold insert. When in use, a complete mold may formed by fastening the reinforced and thickened mold insert of the invention to a mold seat.
In step 160, one or more metal mesh may be selectively added to the thickened metal layer to increase the tensile strength in horizontal direction.
More details of the invention are discussed by referring to the embodiments below. It is to be noted that they serve only for illustrative purpose, and are not the limitation of the invention.

Embodiment 1

Refer to FIG. 2 for embodiment 1 of the structure of the reinforced and thickened mold insert according to the invention.
First, form a nickel shell 10 (180×70×2.5˜3 mm) by electroforming on an original mandrel (not shown in the drawing); next, deposit a plurality of silver paste spots on the nickel shell on selected locations, and coat an anti-plating paste on the rest portion.
Cure the silver paste, submerge the original mandrel in an electroforming solution of 50° C., electroplate and deposit nickel by current density 1˜5 ASD for about 8-12 hours to form mushroom-shaped coupling reinforced sections 50 on the silver paste spots.
Next, separate the original mandrel and the nickel shell 10; cover one side of the nickel shell 10 by an aluminum foil, blast other side with emery to form a coarse surface, the blasting pressure is about 50-70 psi.
In this embodiment, the metal thicken layer is copper. To increase the bonding effect between the copper layer and the nickel shell 10, a nickel aluminum alloy dissolved in acetylene is sprayed on the nickel shell 10 to jointly form a key bonding layer 20.
Finally, spray copper on the key bonding layer 20 for a duration of 65 minutes, to form a copper layer 30 at a thickness of 20 mm.
As shown in the drawing, the mushroom-shaped coupling reinforced sections 50 formed on the surface of the nickel shell 10 are planted in the copper layer 30. Thus the bonding power between the electroformed metal mold insert and the copper layer 30 increases, and separation of the two is less likely. The finished thickened mold insert may be fastened to a mold seat by screwing to become a complete mold.
Metal spraying operation in the embodiment 1 adopts the following parameters and conditions:

- Compressed air pressure: 70 psi
- Compressed airflow: 53 CFM
- Acetylene pressure: 15 psi
- Acetylene flow: 40 CFM
- Oxygen pressure: 30 psi
- Oxygen flow: 44 CFM

Embodiment 2

The process of embodiment 2 is largely like that of the embodiment 1, however, instead of copper, zinc is used and sprayed on the key bonding layer 20 for a duration of 75 minutes to form a zinc layer 40.

Embodiment 3

Refer to FIG. 3 for embodiment 3 of the structure of the reinforced and thickened mold insert according to the invention.
The process of embodiment 3 is largely like that of the embodiment 2, however, instead of directly depositing silver paste on the nickel shell 10, M5 screws 60 are bonded to the nickel shell on selected locations through silver paste. Then they are submerged in an electroforming solution to deposit nickel. Finally, zinc is sprayed on the key bonding layer 20 for a duration of 75 minutes to form a zinc layer 40. The screws 60 function as the coupling reinforced sections do.

Embodiment 4

Its process is largely like that of embodiment 3 previously discussed. However, copper is sprayed on the key bonding layer 20 for a duration of 65 minutes to form a copper layer 30.

COMPARISON EXAMPLES 1 AND 2

The process of the comparison examples 1 and 2 is substantially like the ones illustrated in embodiments 1 and 2. However, the nickel shell 10 does not form coupling reinforced sections 10 during the electroforming process.

Refer to Table 1 for the operation conditions of the embodiments and the comparison examples.

TABLE 1


Coupling reinforced	Thicken	Thicken Time
section type	metal	(min.)

Embodiment 1	Mushroom shape	Copper	65
Embodiment 2	Mushroom shape	Zinc	75
Embodiment 3	M5 Screw	Zinc	75
Embodiment 4	M5 Screw	Copper	65
Comp. Example	Nil	Copper	65
1
Comp. Example	Nil	Zinc	75
2

Two to three pieces of mode inserts (70×40×10 or 20 mm) fabricated according to embodiments 1 through 4, and the comparison examples 1 and 2 are put to test (by a tensile test machine Instron 4206), under the conditions of load cell 5,000 Kg, and the elongation rate 50 mm/minute. The test results are shown in Table 2.

	TABLE 2


	Average Tensile
	strength (psi)	Rupture condition

Embodiment 1	583	Copper layer damaged
Embodiment 2	536	Zinc layer and nickel shell
		separated
Embodiment 3	575	Nickel shell and zinc layer
		separated partially
Embodiment 4	510	Copper layer damaged
Comp. Example 1	425	Nickel shell and copper
		layer separated, key
		bonding layer damaged
Comp. Example 2	359	Nickel shell and zinc layer
		separated, key bonding
		layer damaged

Based on the test results shown in Table 2, the mold inserts of the invention that have the mushroom-shaped coupling reinforced sections 50 or screws 60 have a tensile strength between 510˜583 psi, and are greater than 359 and 425 psi of the comparison examples. In addition, the rupture conditions show that for embodiments 1 and 4, only the copper layer 30 are damaged, and the bonding between the nickel shell 10 and the nickel aluminum key bonding layer 20 remains intact.
For embodiments 3 and 3, separation occurs to the nickel shell 10 and the zinc layer 40, but the tensile strength is much greater than the comparison examples 1 and 2. The test results show that, in the comparison examples 1 and 2, the nickel shell 10 or nickel aluminum key bonding layer 20 is completely separated from the thickened metal layer 30 or 40.

Embodiment 5

Refer to FIG. 4 for embodiment 5 of the structure of the reinforced and thickened mold insert according to the invention.
The process for embodiment 5 is largely like that of embodiment 1, however, the nickel shell 10 not only has the mushroom-shaped coupling reinforced sections 50 formed thereon, it also is fastened to M5 screws 60. Hence both the mushroom-shaped coupling reinforced sections 50 and the M5 screws 60 can increase the bonding power between the electroformed metal mold insert and the thickened metal layer.

Embodiment 6

Referring to FIG. 5 for embodiment 6 of the structure of the reinforced and thickened mold insert according to the invention.
The process for embodiment 5 is largely like that of embodiment 1, however, while forming the thickened copper layer, a metal mesh 70 is soldered by electroforming around the mushroom-shaped coupling reinforced sections 50, to increase the tensile strength in the horizontal direction.
Although no tensile tests have been conducted for the embodiments 5 and 6, based on their structure, their strengthening effect must be greater than the comparison examples.
Besides forming the protrusive coupling reinforced section on the nickel shell 10 to increase the bonding power between the electroformed metal mold insert and the thickened metal layer, another approach is to form a plurality of indented troughs on the nickel shell 10 by electroforming. When forming a thickened metal layer by metal spraying in the later process, metal will be filled into the indented troughs. This also can increase the bonding power between the electroformed metal mold insert and the thickened metal layer.
Comparing the embodiments of the invention with the comparison examples after being thickened, it is obviously that the invention has successfully overcome the problems of uneven thickness of the electroforming layer, and warping and deformation caused by thermal effect resulting from increasing of thickness by metal spraying.
While the preferred embodiments of the invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments, which do not depart from the spirit and scope of the invention.

Claims

1. A reinforced and thickened mold insert, comprising:

an electroformed metal mold insert;

at least one coupling reinforced section located on the surface of the electroformed metal mold insert; and

a thickened metal layer located on the surfaces of the electroformed metal mold insert and the coupling reinforced section.

2. The reinforced and thickened mold insert of claim 1, wherein the coupling reinforced section is fabricated by depositing at least one silver paste spot on a selected location of the surface of the electroformed metal mold insert and electroforming.

3. The reinforced and thickened mold insert of claim 1, wherein the coupling reinforced section is fabricated by bonding at least one screw to the surface of the electroformed metal mold insert and electroforming.

4. The reinforced and thickened mold insert of claim 1, wherein the coupling reinforced section is fabricated by depositing at least one silver paste spot and bonding at least one screw to the surface of the electroformed metal mold insert and electroforming.

5. The reinforced and thickened mold insert of claim 1 further including a key bonding layer interposed between the electroformed metal mold insert and the thickened metal layer.

6. The reinforced and thickened mold insert of claim 1, wherein the thickened metal layer includes a metal mesh.

7. A method for manufacturing a reinforced and thickened mold insert, comprising the steps of:

providing an original mandrel and forming an electroformed metal mold insert on the surface of the original mandrel;

forming at least one coupling reinforced section on the surface of the electroformed metal mold insert;

separating the original mandrel and the electroformed metal mold insert; and

forming a thickened metal layer on the electroformed metal mold insert and the coupling reinforced section by metal spraying.

8. The method of claim 7, wherein forming at least one coupling reinforced section includes the steps of:

forming at least one silver paste spot on the surface of the electroformed metal mold insert; and

submerging the original mandrel in an electroforming solution to process electroforming and deposit a metal film on the silver paste spot, the protrusive silver paste spot being the coupling reinforced section.

9. The method of claim 7, wherein the forming at least one coupling reinforced section includes the steps of:

fastening at least one screw to the surface of the electroformed metal mold insert; and

submerging the original mandrel in an electroforming solution to process electroforming and deposit a metal film on the screw, the protrusive screw being the coupling reinforced section.

10. The method of claim 7, wherein the forming at least one coupling reinforced section includes the steps of:

forming at least one silver paste spot and fastening at least one screw to the surface of the electroformed metal mold insert; and

submerging the original mandrel in an electroforming solution to process electroforming and deposit a metal film on the silver paste spot and the screw, the protrusive silver paste spot and the screw being the coupling reinforced section.

11. The method of claim 7, wherein the forming at least one coupling reinforced section includes the steps of:

forming at least one indented trough on the surface of the electroformed metal mold insert; and

submerging the original mandrel in an electroforming solution to process electroforming and deposit a metal film in the indented trough to become the coupling reinforced section.

12. The method of claim 7, wherein the separating the original mandrel and the electroformed metal mold insert is followed by forming a key bonding layer on the surface of the electroformed metal mold insert and the coupling reinforced section by metal spraying.

13. The method of claim 7, wherein the forming a thickened metal layer on the electroformed metal mold insert and the coupling reinforced section by metal spraying includes placing a metal mesh in the thickened metal layer.