TECHNIC AL FIELD

The present invention relates to a forging method for manufacturing an article and in particular, to a forging method for manufacturing an article having a thin plate structure and an intermediate product made by the method. BACKGROUND

Articles with thin plate structure are used in many mechanical and electronic devices. For example in hard disk drives, parts such as damper plate, actuator arm and base plate have thin plate structure and as the shapes are relatively more complicated, these parts are typically made by die casting process. Die-casted parts are, however, porous in nature and with high roughness in its surface. Due to the porousness which may lead to acid seeping out after plating, die-casted parts are not suitable for EN plating (Electroless nickel plating) but instead to undergo electrical plating. Forging has been conventionally used to make parts which have a relatively more dense structure and with higher strength and better surface quality compared to die-casted parts. However after failure of many attempts made, conventional forging process has been considered unsuitable for manufacturing articles with thin plate structure such as the damper plate, actuator arm or base plate used in hard disk drives, due to the complicated shape of such parts, the tight structural and/or dimensional tolerance requirements for such parts which exceed the capability of conventional forging process. As a result, such parts are presently still made by die casting process in spite of unsatisfactory performance.

SUMMARY OF THE INVENTION

According to one aspect, embodiments of the present invention provide an improved forging method for manufacturing an article which has a thinner body and a thicker body. A blank of a plastically deformable material, e.g. an aluminum bar is placed between an upper die and a lower die. The upper die is moved towards the lower die to presj^hej^ank^ causm

flows into an impression and a gutter formed in the upper die and lower die. An

intermediate product is formed in which, the blank material forms the thinner body, the thicker body and a flash. The thinner body is formed in a shallow trench of the impression, the thicker body is formed in a deeper trench of the impression, and the flash is formed in the gutter surrounding the shallow trench and the deeper trench. The intermediate product is then extracted from the dies and the flash is trimmed to form the article.

The flash includes a first flash portion closer to the thicker body and a second flash portion away from the thicker body. The first flash portion has a first flash thickness and the second flash portion has a second flash thickness. The first flash thickness is greater than the second flash thickness. In the process of forming the intermediate product, a first gutter area of the upper die and the lower die corresponding to the first flash portion allows more material to flow through than a second gutter area of the upper die and the lower die which corresponds to the second flash portion, and a third gutter area of the upper die and the lower die which corresponds to the third flash portion. In this way, the blocking effect to material flow caused by materials filled in the deeper trench is compromised and compensated and accordingly, material flow at shallow trench is evenly distributed. Applying a method according to the embodiments of the present invention, a hard disk damper plate can be manufactured by forging in which, the main thin plate body portion has an even thickness to satisfy the thickness requirements for use in a hard disk drive.

According to another aspect, a method of manufacturing an article includes determining a profile of a blank, providing an extruded sectional plate material according to the profile, stamping or cutting the extruded sectional plate material to form a blank, and forging the blank to form the article. The blank has a first portion and a second portion. The blank may also have more portions. The first portion has a first initial thickness and first initial surface area, the second portion has a second initial thickness and second initial surface area. The article includes the first portion and the second portion. The first portion has a first final thickness less than the first initial thickness and a first final surface area greater than the first initial surface area. The second portion has a second final thickne^s^e^sJhanJhe^e^OTdJni al thickness and a second-final-surfaee area greater than the second initial surface area.

Other aspects and advantages of the present invention will become apparent from the following detailed description, illustrating by way of example the inventive concept of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will be described in detail with reference to the accompanying drawings, in which: Figs. 1 A and IB are perspective views showing blanks for manufacturing a hard disk damper plate;

Fig. 2 is a perspective view showing a lower die for manufacturing a hard disk damper plate from the blank shown in Fig. 1 A or IB;

Fig. 3 is a perspective view showing an intermediate product made by a method according to one embodiment of the present invention;

Fig. 4 is a partial cross sectional view of Fig. 3 along A-A;

Fig. 5 is a partial cross sectional view of Fig. 3 along B-B;

Fig. 6 is a perspective view showing a finished article made from the intermediate product of Fig. 3;

Fig. 7 is a perspective view showing an intermediate product according to one embodiment of the present invention; Fig. 8 is a perspective view showing an intermediate product according to another embodiment of the present invention;

Fig. 9 is a flow chart showing a method of manufacturing an article according to an embodiment of the present invention.

Fig. 10 is a perspective view showing a sectional material for preparation of blanks for forming thin plate article according to a further embodiment of the present invention.

Fig.11 is a perspective view showing forming of blanks from the sectional material of Fig. 10.

Fig. 12 is a flow chart showing a method of manufacturing an article according to an embodiment of the present invention.

Fig. 13 is a perspective view showing a sectional material for preparation of blanks for forming thin plate article according to still a further embodiment of the present invention.

Fig. 14 is a partial enlarged view of Fig. 13.

Fig. 15 is a perspective view showing forming of blanks from the sectional material of Fig. 13.

Fig. 16 is a perspective view showing a blank formed after the process shown in

Fig. 15.

Fig. 17 is a perspective showing a final article formed after a forging process.

Fig. 18 is a flow chart showing a method of manufacturing an article according to an embodiment of the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A method for manufacturing an article by forging process is provided. In the present embodiment, the article is a hard disk damper plate having a thin plate structure. Figs. 1A and IB show blank 10a, 10b of a plastically deformable material e.g. an aluminum bar, used to produce the hard disk damper plate. The blank may be bent from a straight aluminum bar with various types of cross section, for instance one having a round cross section as shown in Fig. 1A, or a rectangular cross section as shown in Fig. IB. The bent aluminum bar 10a or 10b is heated up to a temperature suitable for hot forging, and placed and pressed between an upper die and a lower die. The upper die and lower die have a complementary structure, shape and dimension and therefore only the lower die 22 is shown in Fig. 2 for illustration.

Lower die 22 includes an impression formed of a shallow trench 220 and three deeper trenches 222, 224 and 226 connected to shallow trench 220. A gutter 228 is formed surrounding shallow trench 220 and deeper trenches 222, 224 and 226. When being pressed between the upper and lower dies, blank 10 is plastically deformed with the material flows and fills in shallow trench 220, deeper trenches 222, 224 and 226 as well as gutter 228. When the pressing process is completed, blank 10 is formed into an intermediate product 20 of an integral structure, as shown in Fig. 3. The blank material filled in shallow trench 220 forms a thin plate body 210. The blank material filled in deeper trenches 222, 224 and 226 form pads 212, 214 and 216, and the blank material filled in gutter 228 forms a flash 218. The thin plate body illustrated in the present embodiment refers to a body structure having a thickness ranging from about 1.3 mm to 3.6 mm, and with a thickness/width ratio ranging from about 0.1 to 0.7.

Further referring to Figs. 4 and 5, flash 218 includes a first flash portion 2181, a second flash portion 2182 and a third flash portion 2183. First flash portion 2181 and second flash portion 2182 are located at a same side of plate body 210 as pad 212, and third flash portion 2183 is located at an opposite side of main body 210 with respect to pad 212. First flash portion 2181 is closer to pad 212 than second flash portion 2182 and third flash portion 2183. First flash portion 2181 has a first flash thickness 2181a greater than a second flash thickness 2182a of second flash portion 2182. First flash thickness 2181 a is also greater than the third flash thickness 2183a of third flash portion 2183.

To form flash 218 with the above-described structure and dimensions, the upper die and lower die are provided with corresponding gutter structure and dimensions as illustrated in Fig. 2. As shown, gutter 228 has a first gutter area 2281 closer to deeper trench 222, a second gutter area 2282 away from deeper trench 222, and a third gutter area 2283 located at an opposite side of shallow trench 220 with respect to deeper trench 222. First gutter area 2281 has a depth greater than that of the second gutter area 2282 and third gutter area 2283.

During the process of pressing blank 10a or 10b to form intermediate product 20, first gutter area 2281 allows more material to flow through to form first flash portion 2181 than second gutter area 2282 and third gutter area 2283. In this way, the blocking effect to material flow caused by the materials filled in deeper trench 222 is compromised and compensated by the deeper first gutter area 2281 and accordingly, material flow at shallow trench 220 is evenly distributed. Upon completion of the pressing process, an intermediate product 20 is obtained in which, the thicknesses of flash 218 at first flash portion 2181 is different from that at second flash portion 2182 and third flash portion 2183. As a result, a plate body 210 is obtained with an even thickness 210a throughout the whole area.

In the present embodiment, intermediate product 20 is to form a damper plate 20' for hard disk drive, after flash 218 is trimmed off, as shown in Fig. 6. An intermediate product 30 is manufactured by a method of the present invention to form a damper plate, as shown in Fig. 7. Intermediate product 30 is partially ring-shaped having a first end 30a, a second end 30b and a middle portion 30c between first end 30a and second end 30b. A first pad 312, a second pad 314 and a third pad 316 are formed spaced apart from each other, to serve as screw mount support. First pad 312 is formed adjacent to first end 30a, second pad 314 is formed adjacent to second end 30b and third pad 316 is formed at middle portion 30c and closer to first pad 312 but away from second pad 314. A first middle flash portion 3181 between first and third pads 312, 316 is thicker than a second middle flash portion 3182 between second and third pads 314, 316. By configuring the flash thickness in this manner, first middle flash portion 3181 and second middle flash portion 3182 assist in better material flow control during the pressing process and as a result, the main body 310 can be formed with even thickness. In an alternative embodiment as shown in Fig. 8, and intermediate product 40 for a hard disk damper plate may be formed with first, second and third pads 412, 414 and 416 having different shape, dimension and mass. For instance, first pad 412 may have a mass greater than second pad 414. In this embodiment, a first flash portion 4181 closer to first pad 412 is thicker than a second flash portion 4182 closer to second pad 414. By configuring the flash thickness in this manner, first flash portion 4181 and second flash portion 4182 assist in better material flow control during the pressing process and as a result, the main body 410 can be formed with even thickness.

According to a method provided by the present embodiment, a hard disk damper plate is formed by an improved hot -forging process, the damper plate has a main body with thickness tolerance meeting the structural and dimensional requirements for use in hard disk drives.

A damper plate formed with the plate body complies with the dimensional tolerance requirements, and also has the advantage in that, the plate body may also serve as a clamping portion and positional/dimensional reference for machining the pads. The pads machined on this basis will also possess necessary dimensional and positioning accuracy for use as screw support to mount the damper plate to a hard disk base plate. After the pads are machined to the desired shape/dimension, the surface of the thinner body and the thicker body may be treated with electroless nickel plating.

Fig. 9 is a flow chart showing a method 900 of manufacturing an article according to an embodiment of the present invention. At step 902, a blank is heated up to a temperature suitable for hot forging. At step 904, the blank is placed between an upper die and a lower die. At step 906, the upper die is moved towards the lower die to press the blank, and cause the blank to plastically deform and to fill in an impression and a gutter formed in the upper die and lower die. An intermediate product is formed in which, the blank material forms the thinner body, the thicker body and a flash. The thinner body is formed in a shallow trench of the impression, the thicker body is formed in a deeper trench of the impression, and the flash is formedJnJhe_gutter._An intermediate-product is formed in which, the blank material forms the thinner body, the thicker body and the flash. The thinner body is formed in a shallow trench of the impression, the thicker body is formed in a deeper trench of the impression, and the flash is formed in the gutter. The flash has a first flash portion closer to the thicker body and a second flash portion away from the thicker body. The first flash portion has a first flash thickness which is thicker than a second flash thickness of the second flash portion. By controlling the thickness of the flash at different portions, the thinner body is obtained with an even thickness. At step 908, the flash is trimmed off to form the article.

In a further embodiment as shown in Figs. 10 and 1 1, a sectional material 1000 is pre-made, by extrusion for instance, for forming a thin plate article e.g. a hard disk damper plate. Sectional material 1000 has thinner portions 1010 with thickness slightly greater than main body 210 (Fig. 6) of the hard disk damper plate. The thickness difference between thinner portion 1010 and main body 210 is within the range of plastic

deformation of the sectional material 1010 when being pressed by cold forging, i.e.

without the heating process. Similarly, thicker portions 1012, 1014 and 1016 each has a thickness the same or slightly greater than that of the pads 212, 214 and 216. As shown in Fig. 11, blanks 1020 are formed by stamping the sectional material 1000, each blank 1020 has a contour dimension slightly greater than the final dimension of the hard disk damper plate. The blank 1020 can then be further pressed by the molding process similar to that illustrated hereinabove, to form the hard disk damper plate.

Fig. 12 is a flow chart showing a method 1200 of manufacturing an article according to an embodiment of the present invention. At step 1202, a blank is provided, for instance, by stamping a sectional material. The sectional material is shaped and dimensioned suitable for being plastically deformed by cold-forging to form the required thin plate part i.e., without heating. At step 1204, the blank is placed between an upper die and a lower die. At step 1206, the upper die is moved towards the lower die to press the blank, and cause the blank to plastically deform and to fill in an impression and a gutter formed in the upper die and lower die. An intermediate product is formed in which, the blank material forms the thinner body, the thicker body and a flash. The thinner body is formed in a shallow trench of the impression, the thicker body is formed in a deeper trench of the impression, and the flash is formed in the gutter. An intermediate product is formed in which, the blank material forms the thinner body, the thicker body and the flash. The thinner body is formed in a shallow trench of the impression, the thicker body is formed in a deeper trench of the impression, and the flash is formed in the gutter. The flash has a first flash portion closer to the thicker body and a second flash portion away from the thicker body. The first flash portion has a first flash thickness which is thicker than a second flash thickness of the second flash portion. By controlling the thickness of the flash at different portions, the thinner body is obtained with an even thickness. At step 1208, the flash is trimmed off to form the article.

In a still further embodiment as shown in Figs. 13 to 18, an extruded sectional plate material 2000 is provided for forming an article, for example a hard disk damper plate 2020. Based on the specification e.g. thickness, surface area of the hard disk damper plate 2020, a profile of the blank 2010 to be formed from the extruded sectional plate material 2000, is determined. One or more blanks 2010 are formed, e.g. by cutting or stamping the extruded sectional plate material 2000. Blank 2010 may be further processed to have predetermined excess parts removed, e.g. the part 2012A shown shaded in Fig. 15, by milling for example.

As shown in Fig. 16, blank 2010 includes a first portion 2011 and a second portion 2012. First portion 2011 has an initial surface flatness, a first initial thickness Ti l, and a first initial surface area Al 1. Second portion 2012 has a second initial thickness T 12, and a second initial surface area A 12. The initial surface flatness of first portion 2011 is the same as that of the extruded sectional plate material 2000.

Extruded sectional plate material 2000 is selected according to the profile of the blank2010, such that on the blank 2010 formed from extruded sectional plate material 2000, first and second initial thickness Tl 1, T21 are slightly greater than the respective first arid second final thickness T12, T22 of the article 2020. Additionally, the first and second initial surface area Al 1, A21 are slightly less than the respective first and second final surface area A 12, A22. In one particular example, the extruded sectional plate material 200 is made of aluminum, and the first and second initial thickness Tl 1, T12 are about 0.1mm to 0.5mm greater than the respective first and second final thickness T12, T22 of the article 2020.

After a forging process, blank 2010 shown in Fig. 16 forms the final article, e.g. a hard disk damper plate 2020, as shown in Fig. 17. The forging process reduces the first and second initial thickness Tl 1, ΤΓ2 to the final first and second initial thickness T21, T22, and causes the material flow such that the first and second final surface area A21, A22 are increased from the first and second initial surface area Al 1, A 12. In the meantime, the forging process improves the surface flatness throughout the whole areas of first portion 2011. The final volume of first portion 2011 , which is determined by the first final thickness T12 and first final surface area A 12, is the same as the initial volume of first portion 2011 determined by the first initial thickness Ti l and the first initial surface area Al l. Likewise, the final volume of second portion 2012 determined by the second final thickness T22 and the second final surface area A22, is the same as the initial volume of second portion 2012 determined by the second initial thickness T21 and the second initial surface area A21. Accordingly, based on the first and second final thickness T12, T22 and first and second final surface area A 12, A22, as that required according to the specification of the article 2020, the profile of the blank, including the first and second initial thickness Tl 1, T21 and first and second initial surface area Al 1, A21 required for the blank 2010, can be determined.

Fig. 18 is a flow chart showing a method 2200 of manufacturing an article according to an embodiment of the present invention. At step 2204, an extruded sectional plate material is provided, according to the determined blank profile. At step 2206, the extruded sectional plate material is cut or stamped, to form a blank. The blank has a first portion and a second portion. The first portion has a first initial thickness and first initial surface area, the second portion has a second initial thickness and second initial surface area. At step 2208, the blank is forged to form the article having the first and second portions. The first portion has a first final thickness less than the first initial thickness and iks finaLsurface^area-greater han he-first4nitiafsto

second final thickness less than the second initial thickness and a second final surface area greater than the second initial surface area.

Although embodiments of the present invention have been illustrated in conjunction with the accompanying drawings and described in the foregoing detailed description, it should be appreciated that the present invention is not limited to the embodiments disclosed. Therefore, the present invention should be understood to be capable of numerous rearrangements, modifications, alternatives and substitutions without departing from the spirit of the invention as set forth and recited by the following claims.