Molding of die-cast product and method of
A system and method of preventing surface imperfections of die-cast products with the method comprising the steps of loading a volume of molten zinc from a source of molten zinc into a chamber of a dispenser station, dispensing the molten zinc from the dispenser station through a hot runner and into a mold cavity, continually maintaining the molten zinc in a molten state from the source of molten zinc to the mold cavity, interrupting the flow of the molten zinc to the mold cavity, following the contraction of the molten zinc in the mold cavity as the molten zinc solidifies therein; and removing the solidified die-cast zinc product from the mold cavity.
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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTNone
REFERENCE TO A MICROFICHE APPENDIXNone
FIELD OF THE INVENTIONThis invention relates generally to die-casting devices, and more specifically, to a system for die-casting products having reduced surface imperfections and a method of improving the surface properties and inhibiting or preventing surface imperfections and cracking of die-cast products such as zinc products.
BACKGROUND OF THE INVENTIONDie-casting of parts is known in the art and generally has been adequate for most of their intended purposes. However, conventional die-casting methods have been known to produce die-cast products that are prone to develop surface imperfections when the user attempts to place a finish surface treatment on the die-cast product
In order to solve the above problem, the inventor has discovered that when die-cast zinc products are manufactured in which the molten zinc is continually maintained in a molten state from a source of the molten zinc to a die-casting mold, the resultant solidified die-cast product can be subsequently surface treated, such as by electroplating, without development of surface imperfections in the coating on the product. The process for forming solidified die-cast products without surface imperfections in the coating on the product involves maintaining a molten zinc source, a zinc-dispenser station, a portion of a mold station and a runner connecting the dispenser station and the mold station at a temperature that maintains the molten zinc in a molten state until the molten zinc reaches a cavity of the mold station in which the molten zinc is allowed to cool and solidify to form the die-cast product. After the die-cast product is cooled and removed from the mold, a surface finish is applied to the product to create a product free or substantially free of surface blemishes or imperfections.
SUMMARY OF THE INVENTIONThe present invention comprises a system for die-casting products free or substantially free of surface blemishes or imperfections. The system includes a source of molten zinc connected to a dispenser station, a hot runner, and a mold station comprising a mold cover and a mold housing that can provide a closed system for delivery of molten zinc to a mold cavity with minimal or no air contact with the molten zinc as it flows from the dispenser station to the mold cavity. The dispenser station supports a volume of molten zinc from the source of molten zinc and includes a pressure cylinder for loading the molten zinc into the dispenser station and dispensing the molten zinc from the dispenser station. The hot runner connects the dispenser station to the mold cover to transfer the molten zinc from the dispenser station to the mold cavity with the dispenser station, the hot runner, and the mold cover continually maintaining the molten zinc supported therein in a molten state during use. The mold cavity receives the molten zinc and maintains the molten zinc therein at a temperature suitable for molten zinc solidification.
The mold station includes a pathway connecting the hot runner to the mold cavity. Located in the pathway of the mold station is an actuating pin for controlling access of the molten zinc to the mold cavity. Actuating pin also follows the contraction of the molten zinc in the mold cavity as the molten zinc solidifies. Once solidified in the mold cavity, the molten zinc forms a solidified die-cast zinc product. The mold may also includes an ejection pin for removing the solidified die-cast zinc product from the mold. The above system may also include a finishing station for applying a finishing surface treatment on the solidified die-cast products after the die-casting process has been completed.
The present invention also includes a method comprising the steps of loading a volume of molten zinc into a chamber of a dispenser station, dispensing the molten zinc from the chamber of the dispenser station through a hot runner and into a mold cavity defined by a mold housing and a mold cover, continually maintaining the molten zinc in a molten state from a source of molten zinc to the mold cavity, interrupting the flow of the molten zinc to the mold cavity, following the contraction of the molten zinc in the mold cavity by maintaining sufficient pressure on the molten zinc as it solidifies therein to inhibit formation of air bubbles, and removing the solidified die-cast zinc product from the mold cavity. Once removed, a finishing surface treatment may then be applied solidified die-cast zinc product.
Referring to
The dispenser station 11 generally comprises a dispenser housing 18 having a first end 18a and a second end 18b and a chamber 16 for supporting molten zinc 17 therein. A pressure cylinder 19 having a piston 19a can deliver a shot of molten zinc to the mold station 12. Chamber 16 is connected to the source of molten zinc 13 that has an inlet 27a located below the surface of the molten zinc so that air is inhibited or prevented from being drawn in with the molten zinc as it flows into chamber 16. It is noted that the shot of molten zinc is defined as a predetermined or pre-set amount or charge of molten zinc equaling proximal the volume of a cavity of the mold. In regards to the term “molten zinc,” it should be noted that molten zinc or zinc in the molten state refers to zinc that is in a liquefied state and zinc that is in a “slushy state.” The slushy state can be defined as the state in which zinc is between the liquefied state and solid state. Zinc in the slushy state is normally obtained when liquefied zinc is lower to a temperature proximal but above the melting point or melting temperature of zinc which is about 420° C. The slushy state can also be obtained through heating zinc in the solid state to a temperature above the melting point or melting temperature of zinc.
In the slushy state the zinc still possesses some of the characteristics of the zinc in the liquefied state, including the ability to flow through the system 10 without forming blockages in the system 10. That is, similar to zinc in the liquefied state, the properties of the zinc in the slushy state still permits the pressure cylinder 19 to load the zinc 17 from the source of molten zinc 13 into the chamber 16 and dispensing the zinc 17 from the chamber 16 of the dispenser station 11 through hot runner 15 and into the mold station 12. Using the zinc in the slushy state provides the advantage of reducing the required time for solidification of the product since the temperature change of the zinc from the slushy state to the solid state is less then the temperature change of the zinc from the liquid state to the solid state.
In further regards to dispenser station 11, the piston 19a of pressure cylinder 19 includes a piston face 19b that is moveable between a first or up position (shown in
Mold station 12, shown in
The pressure p0 in pressure cylinder 30 is maintained at sufficient pressure so actuating pin 24 follows the contraction of the molten metal in the mold cavity without intensifying the pressure on the molten metal as it solidifies. By applying sufficient pressure to the actuating pin 24 to follow the contraction of the molten zinc without intensifying the pressure in the mold cavity 22 actuating pin 24 inhibits or prevents formation of air bubbles in the solidified die-cast zinc product. That is, actuating pin 24 has a diameter that blocks molten zinc flow through passageway 24 with the volume of the molten zinc in the pathway 23 (see
A feature of the present invention is that the source of molten zinc 13, the dispenser housing 11, the hot runner 15, and the mold cover 20, in use, collectively function to continually maintain the molten zinc 17 in the liquid or slushy state from the source of molten zinc 13 until the molten zinc 17 reaches the mold cavity 22 to form a die-cast product that is free or substantially free of surface blemishes or imperfections after a surface finish is applied to the product. Continually maintaining the molten zinc 17 in the liquid or slushy state from source of molten zinc 13 to the mold cavity 22 also provides that added benefit of preventing potential blockage in the flow of the molten zinc 17 in the system due to solidification of the zinc in the system 10 and also saves energy cost since reheating of the runner 15, mold cover 20, dispenser station 11, and source of molten zinc 13 is not required.
Molten zinc 17 may be maintained in the liquid or slushy state by maintaining an interior temperature of the dispenser housing 11, the hot runner 15, and the mold cover 20 at or above 420° C. (693 K, 788° F.), which is the melting point or melting temperature of zinc. The interior temperature of the source of molten zinc 13, the dispenser housing 11, the hot runner 15, and the mold cover 20 may be maintained at or above the melting temperature of zinc by any of a variety of heating means. For example, the hot runner 15 may include a heating element such as a wire or coiled heating element (not shown) extending throughout the entire length of the hot runner 15 for continually maintaining the molten zinc supported therein in a molten state throughout the entire length of the hot runner 15. A layer of thermal insulation may surround the runner 15 to inhibit loss of heat to the atmosphere.
In regards to mold housing 21, a feature the present invention is that mold housing 21 is maintainable at a temperature suitable for the solidification of molten zinc and includes an ejection pin 25 for removing a solidified die-cast zinc product from the mold cavity obtained from the solidification of the molten zinc 17.
Since mold cover 20 is continually maintained at a temperature sufficient to maintain the molten zinc 17 in the molten state and mold housing 21 is maintainable at a temperature suitable for the solidification of molten zinc, mold station 12 is shown in the embodiment of
Referring back to
In the operation of the system 10, as shown in
At the initiation of the zinc die-casting process, the control system 14 sends a signal to the mold station 12 to bring the mold station 12 from the initial closed condition to the open condition by moving the actuating pin 15 to a position that unblocks the access of the molten zinc 17 to the mold cover pathway 23. The control system 14 then sends a signal to the dispenser station 11 to initiate the dispensing of the molten zinc 17 supported within chamber 16 through displacement of the piston face 19b of pressure cylinder 19 from the first or up position (shown in
Although not required, mold station 12 is shown in
Referring to
The control system 14 then sends a further signal to the mold station 12 to maintain sufficient pressure p0 on actuating pin 24 so that pin 24 follows the solidification contraction of the molten zinc 17 in the mold cavity 22 without intensifying the pressure of the molten zinc therein. Having pin face 24 engaging a portion of the molten zinc 17 during the solidification process of the molten zinc 17 provides for a solidified die-cast zinc product 28 free or substantially free of surface imperfections.
The control system 14 then sends a signal to the dispenser station 11 to initiate the reloading process of molten zinc in chamber 16 through the displacement of the piston face 19a of pressure cylinder 19 from the second or down position (shown in
At the completion of the die-casting process, identified by the solidification of the molten zinc 17 to a die-cast zinc product 28, the mold cover 20 is removed from the mold housing 21 and the solidified die-cast product 28 is removed from the mold housing 21. The portion of the molten zinc 17 that had solidified to close off mold passage 30 may also be removed during the removal stage of the solidified die-cast product 28 from the mold housing 21. Although the solidified die-cast product 28 may be removed from the mold housing 21 by a variety of methods,
Once die-cast zinc product 28 is removed from the mold housing 21 die-cast zinc product 28 is moved to finishing station 26, where a surface finish is applied to the die-cast zinc product 28, with the surface finish of the product 28 being free of blemishes or imperfections. Examples of finishing the surface include the step of electroplating, painting or the like of the die-cast product.
Once the die cast product 28 is removed from the mold housing 21 the mold cover 20 is then mated back to the mold housing 21 and the procedure is then repeated to form another die-cast zinc product without allowing the molten zinc between the source of molten zinc 13 and the mold cavity 22 to solidify. While the invention has been described with regard to molten zinc 17, other metals such as magnesium, aluminum, tin or an alloy thereof may be die cast by the same process with the interior temperature of the source of the molten metal, the dispenser housing 11, the hot runner 15, and the mold cover 20 maintained at or above the melting temperature of the particular metal or alloy used. For example, in die-casting magnesium products, the interior temperature of the source of the molten magnesium, the dispenser housing 11, the hot runner 15, and the mold cover 20 would be maintained at or above 650° C. (650 K, 1202° F.), which is the melting temperature for magnesium.
The present invention also includes a method of improving the surface properties and preventing surface imperfections and cracking of die-cast products comprising the steps of (1) loading a volume of molten metal 17 from a source of molten metal 13 into a chamber 16 of a dispenser station 11; (2) dispensing the molten metal 17 from the chamber 16 of the dispenser station 11 through a hot runner 15 and into a mold cavity 22 defined by a mold housing 21 and a mold cover 20; (3) continually maintaining the molten metal 17 in a molten state from the source of molten metal 13 to the mold cavity 22; (4) interrupting the flow of the molten metal in the mold cavity such as by initiating an actuating pin 24 to close off access of the molten metal to the mold cavity 22; (5) following the contraction of the molten metal 17 in the mold cavity 22 by maintaining sufficient pressure on the molten metal as the molten metal solidifies therein to inhibit formation of air bubbles; and (6) removing a solidified die-cast product 28 from the mold cavity 22 of the mold station 12.
The above method may further include the step of (7) applying a finishing surface treatment on the solidified die-cast product 28; (8) using an ejection pin 25 located on the mold housing 21 to remove the solidified die-cast product 28 from the mold housing 21; (9) using a pressure cylinder 19 to load the molten metal 17 from the source of molten metal 13 into the chamber 16 of dispenser station 11 and using the pressure cylinder 19 to dispense the molten metal 17 from the chamber 16 of the dispenser station 11; (10) loading molten zinc 17, molten magnesium, molten aluminum, molten tin or an alloy thereof into the chamber 16 of the dispenser station 11; (11) continually maintaining the molten metal 17 in a slushy state from the source of molten metal 13 to the mold cavity 22; (12) continually maintaining the temperature within the dispenser station 11, the hot runner 15, and the mold cover 20 at or above 420° C; (13) maintaining the temperature of the actuating pin 24 above 420° C; (14) placing a thermal-insulating barrier 29 between the mold housing 21 and the mold cover 20 to isolate the temperature difference between the mold housing 21 and the mold cover 20; and (15) venting air inside the mold cavity 22 through a mold passage 30 as the mold cavity 22 receives the molten metal 17.
Claims
1. A system for die-casting products with reduced surface imperfections comprising:
- a source of molten zinc;
- a dispenser station having a molten zinc chamber and a piston for loading and dispensing molten zinc from the dispenser station;
- a mold cover continually maintaining the molten zinc supported therein in a molten state;
- a hot runner for transferring the molten zinc from the dispenser station to the mold cover;
- a mold housing mateable with the mold cover to define a mold cavity therein for receiving the molten zinc, the mold cover having a pathway connecting the hot runner to the mold cavity;
- an actuating pin located in the pathway of the mold cover for controlling access of the molten zinc to the mold cavity and for following the contraction of the solidification of molten zinc in the mold cavity without intensifying the pressure of the molten zinc in the mold cavity; and
- a thermal-insulating barrier located between the mold housing and the mold cover to thermally isolate the temperature difference between the mold housing and the mold cover to enable the zinc in the mold cavity to solidify while the zinc in the mold cover remains in a molten state.
2. The system of claim 1 wherein in use the mold cover, hot runner, dispenser station, and source of molten zinc continually maintain the molten zinc supported therein in a slushy state.
3. The system of claim 1 including a mold passage for venting air from the mold cavity as the mold cavity receives the molten metal and an ejection pin for removing a solidified die-cast zinc product from the mold housing.
4. The system of claim 1 wherein in use the dispenser station, the hot runner, and the mold cover continually maintains a temperature therein at or above 420° C.
5. The system of claim 1 including a control system for controlling the operations of the dispenser station and the mold station.
6. The system of claim 1 including a finishing station for applying a finishing surface treatment on the solidified die-cast zinc product.
7. A method of improving the surface properties and preventing surface imperfections and cracking of die-cast products comprising the steps of:
- loading a volume of molten metal into a chamber of a dispenser station;
- dispensing the molten metal from the chamber of the dispenser station through a hot runner and into a mold cavity defined by a mold housing and a mold cover;
- continually maintaining the molten metal in a molten state from the source of molten metal to the mold cavity;
- interrupting the flow of the molten metal to the mold cavity;
- following the contraction of the molten metal in the mold cavity by maintaining sufficient pressure on the molten metal as the molten metal solidifies therein without intensifying the pressure of the molten metal to inhibit formation of air bubbles; and
- removing a solidified die-cast product from the mold cavity of the mold station.
8. The method of claim 7 including the step of applying a finishing surface treatment on the solidified die-cast product.
9. The method of claim 7 wherein the step of removing the solidified die-cast product from the mold cavity comprises using an ejection pin located on the mold housing to remove the solidified die-cast product from the mold cavity.
10. The method of claim 7 wherein the step of loading the volume of molten metal from the source of molten metal into the chamber of the dispenser station and dispensing the molten metal from the chamber of the dispenser station comprises using a pressure cylinder to load the volume of molten metal from the source of molten metal into the chamber of the dispenser station and using the pressure cylinder to dispense the molten metal from the chamber of the dispenser station.
11. The method of claim 7 wherein the step of loading the volume of molten metal comprises loading a volume of molten zinc, molten magnesium, molten aluminum, molten tin or an alloy thereof.
12. The method of claim 7 wherein the step of continually maintaining the molten metal in a molten state comprises continually maintaining the molten metal in a slushy state from the source of molten metal to the mold cavity.
13. The method of claim 7 wherein the step of continually maintaining the molten metal in a molten state from the source of molten metal to the mold cavity comprises continually maintaining the temperature within the dispenser station, the hot runner, and the mold cover above 420° C.
14. The method of claim 7 including the step of maintaining the temperature of the actuating pin above 420° C.
15. The method of claim 7 including the step of placing a thermal-insulating barrier between the mold housing and the mold cover to thermally isolate the temperature difference between the mold housing and the mold cover.
16. The method of claim 7 including the step of venting air inside the mold cavity through a mold passage as the mold cavity receives the molten metal.
17. A method of inhibiting or preventing surface imperfections and cracking of die-cast zinc products comprising the steps of:
- continually maintaining a shot of molten zinc in a molten state from a source of molten zinc to a mold cavity;
- temporarily closing off an access of the shot of molten zinc to the mold cavity;
- maintaining sufficient pressure on the shot of molten zinc in the mold cavity without intensifying the pressure of the molten zinc in the mold cavity to inhibit formation of air bubbles therein; and
- removing a solidified die-cast zinc product from the mold cavity.
18. The method of claim 17 wherein the step of continually maintaining the shot of molten zinc in a molten state comprises continually maintaining the shot of molten zinc in a slushy state from the source of molten zinc to the mold cavity.
19. The method of claim 17 including the step of applying a finishing surface treatment on the solidified die-cast product.
20. The method of claim 18 wherein the step of continually maintaining the shot of molten zinc in a molten state from the source of molten zinc to the mold cavity comprises continually maintaining the temperature of the shot of molten zinc above 420° C.
21. The method of claim 20 wherein the step of applying a finishing surface comprises electroplating a bubble free coating on the solidified die-cast product
Type: Application
Filed: Aug 5, 2008
Publication Date: Feb 11, 2010
Inventor: Robert W. Ratte (North Oaks, MN)
Application Number: 12/221,677
International Classification: B22D 17/00 (20060101); B22D 39/00 (20060101);