Low melting point metal material injection molding method, injection molding device and body box

• US 6,675,865 B1
• Filed: 06/28/2000
• Issued: 01/13/2004
• Est. Priority Date: 06/30/1999
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yoshida, Tatsuo
• Primary Examiner(s): Elve, M. Alexandra
• Assistant Examiner(s): Tran, Len
• Application Number:
  US09/604,746
• Time in Patent Office: 1,294 Days
• Field of Search: 164/113, 164/312, 164/119
• US Class Current: 164/113
• CPC Class Codes: B22D 17/22 Dies manufacture, see the appropriate class, e.g. B23P15/24; Die plates; Die supports; Cooling equipment for dies; Accessories for loosening and ejecting castings from dies
• CPC Class Codes: Y10S 425/058 Undercut

Abstract

The concave design forming unit with the desired form is formed on the surface of the molded component easily in the case of injection molding by using the low melting point metal material. A low melting point metal material for injecting the molten metal formed of low melting point metal material into the injection molding cavity of the predetermined shape provided in the metal mold, and after mold curing said molten metal, taking out the molded goods from the injection molding cavity; the injection molding cavity will be formed inside by the first metal mold unit and the second metal mold unit contacted and the metal mold having the trapezoidal concave design forming unit with the predetermined height formed on the metal mold inside surface of the first metal mold unit or the second metal mold unit forming said injection molding cavity will be heated to the prescribed metal mold temperature, and the molten metal heated to the predetermined molten temperature will be injected into the injection molding cavity of said heated metal mold at the predetermined injection rate, and after said molten metal injected is being chilled and solidified, separated into the first metal mold unit and the second metal mold unit and the molded component will be taken out from the injection molding cavity.

Claims

1. A metal injection molding method for forming an external case for a notebook personal computer with the external case having formed thereon a concave design pattern and being fabricated from either a metal or a metal alloy having a melting point of 650°

C. or less, the metal injection molding method comprising the steps of;

providing a mold formed by a first die and a second die connected to each other to define an injection molding cavity sized to form the external casing, the first die defining a first die internal surface and the second die defining a second die internal surface disposed apart from one another by a height of the injection mold cavity forming a thickness of the external casing, at least one of the first and second dies including a design pattern forming portion for forming the concave design pattern, the design pattern forming portion projecting from the die internal surface of the at least one of the first and second dies at a design pattern forming portion height being in a range of approximately 25% to 40% of the height of the injection mold cavity, the concave design pattern forming portion having a trapezoidal-shaped as viewed in cross-section and including a sidewall having an inclination angle relative to a line extending perpendicularly to a base of the trapezoidal-shaped cross-sectional view with the inclination angle being in a range of approximately 3° and

5°

in relation to the line that extends perpendicularly to the base, the concave design pattern forming portion including a first circular arc-shaped edge formed between the base and the sidewall with a first radius having a center of radius disposed internally of the concave design pattern forming portion and a second circular arc-shaped portion formed between the sidewall and the die internal surface of the at least one of the first and second dies with a second radius having a center of radius disposed in the injection molding cavity, each one of the first and second radii is in a range of approximately 8% and 17% of the height of the injection molding cavity;

heating the mold at a predetermined metal mold temperature;

heating the metal or metal alloy at a predetermined melting temperature to form a liquid molten state; and

injecting the metal or metal alloy in the liquid molten state into the injection molding cavity at a predetermined uniform velocity.

2. An injection molding method according to claim 1, wherein the predetermined metal mold temperature is approximately 220°

C.

3. An injection molding method according to claim 1, wherein the metal or metal alloy includes a magnesium alloy of code AZ91D according to the Japanese Industrial Standard (JIS).

4. An injection molding method according to claim 1, wherein the metal or metal alloy includes one of magnesium, aluminum, zinc, tin, lead, bismuth, terbium, tellurium, cadmium, thallium, astatine, polonium, selenium, lithium, indium, sodium, potassium, rubidium, cesium, francium, and gallium or an alloy based on any of magnesium, aluminum, zinc, tin, lead, bismuth, terbium, tellurium, cadmium, thallium, astatine, polonium, selenium, lithium, indium, sodium, potassium, rubidium, cesium, fracium, and gallium.

5. A metal injection molding method, comprising the steps of:

providing a metal mold having a first die and a second die connectable together to form an injection molding cavity defined by respective internal die surfaces of the first and second dies when the first and second dies are connected together, the respective internal die surfaces spaced apart from one another at a cavity height with at least one convex part integrally formed with the first die and projecting from the internal die surface thereof into the injection molding cavity, the at least one convex part having, as viewed in cross-section, a base section disposed from the internal die surface of the first die at a convex part height and a pair of sidewalls with each sidewall connected to and extending from the internal die surface of the first die by a first curved portion, each sidewall tapering inwardly toward the base section and connected to the base section by a second curved portion extending between a respective sidewall and the base section, the first curved portion having a first radius with a center of radius disposed in the injection mold cavity and the second curved portion having a second radius disposed internally of the at least one convex part;

heating the mold at a metal mold temperature of approximately 220°

C.;

heating the metal or metal alloy at a predetermined melting temperature to form a liquid molten state; and

injecting the metal or metal alloy in the liquid molten state into the injection molding cavity at a uniform velocity of approximately 80 meters per second wherein,

the base section and each internal die surface is flat with each one of the flat base section and flat internal die surfaces being disposed in a respective plane extending parallel to each other and each sidewall tapers inwardly toward the base section at an inclination angle in relation to a line that extends perpendicularly to the base section in a range of approximately 3° and

5°

, the convex part height is approximately 25% to 40% of the cavity height and each one of the first radius and the second radius is in a range of approximately 8% to 17% of the convex part height.