Metal deforming – By use of closed-die and coacting work-forcer – Forcing work into or within closed die; e.g. – forging
Patent
1987-10-27
1989-05-02
Jones, David
Metal deforming
By use of closed-die and coacting work-forcer
Forcing work into or within closed die; e.g., forging
72352, 72374, 72377, 360135, B21D 100
Patent
active
048256803
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of manufacturing, from a metal blank material, metal substrates for memory disks with ultra-precisely formed smooth and flat surfaces. Metal blank as herein referred to shall mean a non-magnetic metal blank material which is made of aluminum, an aluminum alloy, copper, a copper alloy, magnesium, a magnesium alloy, titanium, a titanium alloy, austenite stainless steel or composites thereof, and metal substrates shall have a similar meaning.
BACKGROUND OF INVENTION
Conventionally, memory disks which are used to record and reproduce various types of information (letters, sounds and images, etc.) are composed of doughnut type metal substrates, the surfaces of which are finished with ultra precision, the substrate being, for instance( an aluminum alloy substrate sheet (substrate) covered with a magnetic substance. In order to precisely perform its duty of allowing recording and reproducing by the magnetic head, the surface of a memory disk is required to have a high degree of flatness and smoothness. Since the surface condition of a memory disk is dependent on the surface condition of its metal substrate, the metal substrate is required to have extremely high dimensional preciseness (flatness, such as the minimum possible amount of undulation and warping) and a high quality surface condition (defect-free, mirror-like smoothness).
Conventionally, there exist a number of ways of making these metal substrates for memory disks, for instance, (a) a process wherein machining is carried out ultra-precisely by a natural diamond bit, (b) a process wherein both sides are simultaneously ground with grinding stones, and (c) a process wherein both sides are polished with abrasive grains and hot water by use of a lapping machine. However, since all of the above processes require machining or grinding, problems have been experienced in that they involve a great deal of time resulting n low productivity and also in that they require many production facilities.
SUMMARY OF INVENTION
The present invention, in consideration of the problems inherent in the conventional technology, offers a method of manufacturing a metal substrate for a memory disk, the quality of which is, at the very least, superior to that obtainable by the conventional technology and yet offering high productivity by use of a coining operation performed with a press. Coining work is a type of technology that is normally used in making coins, and it has generally been practiced in such a manner that the object material is pressed with dies having indentations and protrusions forming a design which when compressed against the relevant surfaces form corresponding protrusions and indentations on the surface of the material to be worked. The present invention is different from the normal coining in which a design is formed in this way; the invention offers a method of manufacturing metal substrates for memory disks by using dies with flat and smooth compressing surfaces and by performing a coining operation on the material with these smooth and flat compressing surfaces of the dies and simultaneously finishing both sides of a substrate with ultra precision.
That is to say, in the manufacturing method of the present invention, a metal blank is sandwiched between two flat pressing surfaces of dies within a metal ring member so that the extent to which the material spreads is restricted and is thus subjected to a coining operation. In this case, a core member may be employed as necessary.
The reason why the coining operation on the blank material is performed within the metal mould that restricts the spreading of the blank metal is that, under this restriction of the material's tendency to spread, it becomes easy to impress the precisely finished die surface onto the surface of a product, and as a result, it is made possible to obtain a formed product with excellent surface precision (smoothness). Furthermore, by performing coining in the above manner, the process is capable of obtaining a formed product
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Coe Thomas U.
Yamazaki Atsushi
C. Itoh & Co. Ltd.
Furukawa Aluminum Co., Ltd.
Jones David
Kawasaki Steel Corp.
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