EP4580823A1 - Counter-piston central injection die casting - Google Patents

Abstract

A die casting system can employ a counter piston to make central injection of large parts or multiple cavity parts possible. The die casting system can include a shot piston disposed on an injection side and a counter piston disposed on an ejector side. The counter piston can move between a sealing position to seal a liquid in the shot sleeve during pouring and slow injection phases, and an opening position to allow the liquid into the casting cavity during cavity injection phase.

Description

TSLA.705WO / P2394-1NWO PATENT COUNTER-PISTON CENTRAL INJECTION DIE CASTING CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. Provisional Patent Application No. 63/403,236, filed September 1, 2022, the entire contents of which is incorporated by reference in its entirety and for all purposes. TECHNICAL FIELD [0002] The present application relates to a die casting machine and process employing a counter-piston. More particularly, the die casting machine or process employs a counter-piston that enables central injection die casting of large parts and/or multiple cavity parts. BACKGROUND [0003] Die casting is a manufacturing process during which molten metal is poured or forced into molds, also known as dies. The larger the die casting part is, the larger the die casting machine is required to be; and the larger the die casting machine is, the larger clamping force is required. In addition, as the die casting part gets bigger, required molten metal flow length gets longer. The castability of a given part is limited by the maximum allowable flow length. [0004] Conventional die casting methods often use a horizontal cold chamber machine with a biscuit and runner system, which requires a large clamping force and higher material costs. Molten metal flows into the chamber or cavity mainly by pressure from one side. Therefore, conventional die casting methods offer limited design control over the flow of the molten metal during the filling process. It does not allow attachment of the biscuit onto the casting cavity because molten metal could spill or flow into the cavity too early during pouring and slow phase. Such conventional die casting methods can result in a limited die casting process window, high energy losses due to low material yield, and low intensification pressure effectiveness. Various limitations and unpredictability remain with current die casting technologies with regard to casting large parts and/or multiple cavity parts. SUMMARY [0005] The disclosure relates generally to a die casting machine and process with a counter-piston. More specifically, various embodiments of this disclosure relate to a die casting machine or process that uses a counter-piston which enables central injection of large casting parts and/or multiple cavity parts. [0006] An aspect is directed to a die casting machine having an ejector side and an injection side. The counter piston die casting machine can include a counter piston disposed on the ejector side, a shot piston disposed on the injection side, and a shot sleeve configured to receive the shot piston and a liquid. [0007] A variation of the aspect above is, wherein the counter piston is movable between a first position and a second position. [0008] A variation of the aspect above is, wherein when the counter piston is in the first position, the liquid is allowed to flow from the shot sleeve to a casting cavity. [0009] A variation of the aspect above is, wherein when the counter piston is in the second position, the liquid is prevented from flowing from the shot sleeve to a casting cavity. [0010] A variation of the aspect above is, wherein when the counter piston is in the second position, the shot sleeve is sealed off by the counter piston from a casting cavity. [0011] A variation of the aspect above is, wherein the counter piston comprises a tapered edge on a side facing the shot sleeve to create a pressing seal with a tapered edge of the shot sleeve on a side facing the counter piston. [0012] A variation of the aspect above is, wherein the counter piston has a non- uniform surface facing the shot sleeve, the non-uniform surface configured to form a corresponding non-uniform surface on a casting part. [0013] A variation of the aspect above is, wherein the counter piston is further movable to a third position. [0014] A variation of the aspect above is, wherein when the counter piston is in the third position, the counter piston is out of a counter piston sleeve for cleaning and lubrication. [0015] A variation of the aspect above is, wherein the shot sleeve comprises a pour hole configured to allow the liquid to enter the shot sleeve. [0016] A variation of the aspect above is, wherein the shot sleeve comprises a vent port configured to allow air to leave the shot sleeve. [0017] A variation of the aspect above is, wherein the counter piston is connected to a driving cylinder, the driving cylinder configured to control motion of the counter piston. [0018] Another aspect is direct to a die casting process employing a counter piston. The process comprises moving the counter piston to at least partially contact a shot sleeve so as to prevent a liquid from flowing through the shot sleeve to a casting cavity. The process can further include sliding a shot piston inside the shot sleeve so as to remove air from inside the shot sleeve, and moving the counter piston away from the shot sleeve so as to allow the liquid to enter the casting cavity. [0019] A variation of the aspect above further comprises moving the counter piston out of a counter piston sleeve for cleaning and lubrication. [0020] A variation of the aspect above further comprises pouring the liquid into the shot sleeve through a pour hole on the shot sleeve. [0021] A variation of the aspect above is, wherein removing air from inside the shot sleeve comprises removing air from the shot sleeve from a vent port on the shot sleeve. [0022] Another aspect is direct to a die casting machine configured to control a flow of molten metal into a casting cavity during a third phase. The die casting machine can include a housing, a shot sleeve, a shot piston, and a counter piston. The shot sleeve can be slidingly disposed in the housing and forming a receptacle, the receptacle being configured to receive the molten metal and a gas during a first phase. The shot piston can be configured to slide in the shot sleeve so as to remove the gas from the receptacle during a second phase leaving the molten metal. The counter piston can be slidingly disposed in the housing so as to prevent the molten metal from entering the casting cavity during the first and second phases while allowing the molten metal to enter the casting cavity during the third phase. [0023] A variation of the aspect above is, wherein the counter piston comprises a tapered edge on a side facing the shot sleeve to create a pressing seal with a tapered edge of the shot sleeve on a side facing the counter piston. BRIEF DESCRIPTION OF THE DRAWINGS [0024] The present disclosure is described with reference to the accompanying drawings, in which like reference characters reference like elements. [0025] FIG.1A is an illustrative front view of a conventional die casting full shot. [0026] FIG.1B is an illustrative front view of a central injection die casting concept according to an embodiment of the present disclosure. [0027] FIG. 2A is a cross-sectional side view of a counter-piston die casting machine according to a preferred embodiment of the present disclosure in a pouring phase, taken along a central longitudinal axis of the counter-piston die casting machine. [0028] FIG. 2B is a cross-sectional side view of the counter-piston die casting machine from FIG.2A in a slow injection phase, taken along a central longitudinal axis of the counter-piston die casting machine. [0029] FIG. 2C is a cross-sectional side view of the counter-piston die casting machine from FIG.2A in a filling phase, taken along a central longitudinal axis of the counter- piston die casting machine. [0030] FIG. 2D is a cross-sectional side view of the counter-piston die casting machine from FIG. 2A in a solidification phase, taken along a central longitudinal axis of the counter-piston die casting machine. [0031] FIG. 3A is an illustrative sectional view of another embodiment of a counter-piston die casting machine according to this disclosure. [0032] FIG.3B is an illustrative top view of the counter-piston die casting machine from FIG.3A. [0033] FIG.4A is a cross-sectional side view of another embodiment of a counter- piston die casting machine according to this disclosure in a slow injection phase, taken along a central longitudinal axis of the counter-piston die casting machine. [0034] FIG. 4B is a cross-sectional side view of the counter-piston die casting machine from FIG. 4A in a solidification phase, taken along a central longitudinal axis of the counter-piston die casting machine. [0035] FIG.4C is a cross-sectional side view of another embodiment of a counter- piston die casting machine according to this disclosure in a sealing phase, taken along a central longitudinal axis of the counter-piston die casting machine. [0036] FIG. 4D is a cross-sectional side view of the counter-piston die casting machine from FIG. 4C in a solidification phase, taken along a central longitudinal axis of the counter-piston die casting machine. [0037] FIG. 5 is a perspective view of an end face of a shot sleeve of another embodiment of a counter-piston die casting machine according to this disclosure. [0038] FIG. 6A is a perspective view of an end face of a shot block of another embodiment of a counter-piston die casting machine according to this disclosure. [0039] FIG.6B is a perspective view of an end face of a shot sleeve of the counter- piston die casting machine from FIG.6A. [0040] FIG. 7A is a cross-sectional side view of an assembled counter-piston that comprises a counter-piston sleeve and a shot sleeve according to this disclosure showing the counter-piston in an extended position, taken along a central longitudinal axis of the counter- piston die casting machine. [0041] FIG. 7B is a perspective view of an end face of the shot sleeve of the counter-piston die casting machine from FIG.7A. [0042] FIG. 8 is an illustration of an assembled counter-piston that comprises a counter-piston sleeve and a shot sleeve with the assembled counter-piston connected to a motion control system. [0043] FIG.9 is a cross-sectional side view of an assembly of an ejector main insert and a counter-piston with air blow-off channels in a die opening phase. DETAILED DESCRIPTION [0044] Generally described, one or more aspects of the present disclosure relate to a die casting machine and process employing a counter-piston. In certain embodiments, this disclosure relates to a die casting machine or process that employs a counter-piston which enables center injection die casting of large parts and/or multiple cavity parts. [0045] Die casting of large casting parts requires a long metal flow length. In order to shorten the metal flow length, there are two existing central injection methods. One method is central shot die casting through a three-plate die configuration. The three-plate die configuration can be complicated and costly, including an additional central plate, an additional extra die opening stroke, an additional runner removal procedure, an additional heat concentration in the middle plate, etc.. [0046] Another method is conventional die casting with a horizontal cold die casting machine as illustrated in FIG.1A. The horizontal cold die casting machine 10 can have a biscuit 11, one or more runners 12, one or more ingates 13, one or more casting cavities (or casting parts) 14, one or more overflows 15, and one or more vents 16. The conventional method requires a large opening in the casting part 14 and a long runner 12. The runner 12 has to be attached to an upper portion of the biscuit 11, resulting in an inefficient runner system, and uneven flow distribution across the cavity and limiting the die casting process operational window (e.g., the castable sizes of casting parts). Extra metal in the biscuit 11 and runner 12 areas is usually not part of the casting part 14 and is scrapped. Therefore, to die cast a large part (e.g., a vehicle chassis), simply scaling and/or combining existing die casting technologies is not a practical economical solution. [0047] A counter-piston die casting system according to this disclosure can resolve one or more problems discussed above. For example, in certain embodiments, employing a counter-piston to exert control over the flow of molten metal allows direct injection of the molten metal into the cavity. As illustrated in FIG. 1B, the counter piston die casting system 20 can eliminate (or significantly reduce) the runners while also allowing the biscuit 24 to be part of the die casting product, reducing production costs. By employing the counter piston, the counter piston die casting system can offer control over a flow of the molten metal and ensure a uniform flow of the molten metal, thereby making casting of large parts predictable and repeatable. In some embodiments, the counter-piston central injection die casting method disclosed herein can lower the required clamping tonnage of the die casting machine (e.g., by about 15~30%), increase material yield (e.g., to about 90% as compared to about 60% of the conventional die casting method), widen a die casting operational window due to shorter molten metal filling distance, and achieve better die casting quality due to its better intensification pressure effectiveness compared to conventional die casting. [0048] FIGs.2A-2D show an exemplary embodiment of a die casting machine 100 according to this disclosure. In certain embodiments, the die casting machine 100 can include a shot piston 101 from an injection side A and a counter piston 106 from an ejector side B. In certain embodiments, on the injection side A, the die casting machine 100 can include a machine platen 103 and a cover die 104 attached to the machine platen 103. In certain embodiments, a shot sleeve 102 can be positioned inside the cover die 104 and/or the machine platen 103 and configured to receive molten metal 119. The shot piston 101 can be configured to be movable inside the shot sleeve 102 and between a first position and a second position. In some embodiments, the first position can be at an end of the shot sleeve 102 proximate the injection side A; and the second position of the shot piston 101 can be at an end of the shot sleeve 102 proximate the ejector side B. In some embodiments, the shot sleeve 102 can include a vent port 117 allowing air to escape and a pour hole 118 allowing molten metal 119 to enter. A space between the cover die and the ejector main insert can define a casting cavity 116 configured to receive the molten metal 119 and form a casting part. [0049] In certain embodiments, on the ejector side B, the die casting machine 100 can include an ejector main insert 105 (or eject die) and/or an ejector holder block 114 attached to the ejector main insert 105. The ejector main insert 105 can include the counter piston sleeve 115 configured to receive and hold the counter piston 106. The counter piston 106 can be configured to be moveable between a sealing position and an opening position. In some embodiments, the counter piston 106 when in the sealing position can be configured to contact and seal the shot sleeve 102 the ejector side B of the shot sleeve 102. In other embodiments, the sealing position of the counter piston 106 can be further towards the injection side A than the opening position of the counter piston 106. The counter piston 106 when in the opening position can be configured to not contact the shot sleeve 102 such that the shot sleeve 102 is not sealed by the counter piston 106 and instead is open to the casting cavity 116. In some embodiments, the counter piston 106 when in the opening position can be fully received by the counter piston sleeve 115. In other embodiments, the counter piston 106 can be at least partially received by the counter piston sleeve 115. [0050] In some embodiments, the die casting machine 100 can further include an ejector platen 110 and an ejector backplate 111 attached to the ejector platen 110 on the ejector side B. In some embodiments, one or more ejector control bars 109 can be positioned inside the ejector platen 110 and/or the ejector backplate 111. The ejector control bar 109 can be attached to an ejector plate 112 and configured to push or pull the ejector plate 112. The die casting machine 100 can further include one or more counter piston support blocks 107 positioned between the ejector main insert 105 (and/or the ejector holder block 114) and the ejector platen 110 (and/or the ejector backplate 111) as shown in FIG. 2A. The ejector plate 112 can be configured to be movable relative to the counter piston support blocks 107 within a space between the ejector main insert 105 (and/or the ejector holder block 114) and the ejector platen 110 (and/or the ejector backplate 111). One or more ejection pins 113 can be attached to the ejector plate 112 on one end and positioned inside the ejector main insert 105 (and/or the ejector holder block 114) on the other end. [0051] As shown in FIG. 2A, during a pouring phase, molten metal 119 can be poured into the shot sleeve 102 through the pour hole 118 with the shot piston 101 in the first position. In some embodiments, the first position of the shot piston 101 can be positioned further towards the injection side A than the pour hole 118. [0052] During the slow injection phase, as shown in FIG.2B, the molten metal 119 can be gently pushed by the shot piston 101 towards the casting cavity 116 on the ejector side B. In some embodiments, air in the shot sleeve 102 can escape and be removed from the shot sleeve 102 through the vent port 117 during the slow injection phase. The counter piston 106 can stay in the sealing position during the slow injection phase. As shown in FIG. 2B, the counter piston 115, when in the sealing position (e.g. against an end face of the shot sleeve 102), can create two separate air chambers, one in the casting cavity 116 and the other one in the shot sleeve, by sealing an opening of the shot sleeve 102 facing the casting cavity 116. The two separate air chambers can help to achieve a high vacuum level in the die cavity without allowing molten metal 119 to enter. [0053] FIG.2C shows the die casting machine 100 in a filling phase, during which molten metal 119 is allowed to enter the casting cavity 116. During the filing phase, the counter piston 106 can be in the opening position and the casting cavity 116 can be unobstructed by the counter piston 106. In some embodiments, the filing phase can start and the counter piston 106 can move to the opening position after the shot piston 101 moves towards the ejector side B and reaches its second position past the vent port 117 such that substantially all air in the shot sleeve 102 has been removed through the vent port 117. [0054] FIG.2D shows the die casting machine 100 in a solidification phase wherein the casting cavity 116 can be substantially filled up by the molten metal 119. In the solidification phase, the shot piston 101 can arrive at its second position, pushing and maintaining the molten metal 119 inside the casting cavity 116; and the counter piston 106 can stay in the opening position. The molten metal 119 can cool down and form the casting part in the casting cavity 116 during the solidification phase. [0055] During a die casting process, the runner and biscuit sections are used to guide molten metal to flow and achieve certain qualities or properties (e.g., temperature, flow rate, etc.) before entering the casting cavity. In some embodiments, the runner and biscuit sections can be eliminated or reduced by using a counter piston die casting process according to this disclosure as compared to a conventional die casting process. With the help of a counter piston, a flow of the molten metal can be controlled by pressure from both sides, a shot piston and a counter piston. With increased control of the flow, the size of any runner and biscuit sections can be designed (e.g., reduced) without adversely impacting the desirable qualities and properties of the molten metal. [0056] In some embodiments, the biscuit and runner shapes can also be configured to be part of the casting geometry to reduce waste in the runner and biscuit system. With a counter piston, the counter piston die casting process can allow placing the injection point at any desirable location because of the flow of molten metal is controllable by both the counter piston and the shot piston. It is therefore possible to configure the biscuit and runner to be part of the casting geometry or at least reduce waste of material by reducing the sizes of the biscuit and runner. [0057] FIGs. 3A-3B illustrates an example of a counter piston die casting process having a shot piston 201 and a counter piston 206. The counter piston die casting process can be configured to have a runner 213 and a biscuit 214 as part of the casting part 211 with a possible ingate location 212 as shown in FIG.3A. In some embodiments, the minimum biscuit thickness can be equal or greater than the casting part thickness required at the location. In some embodiments, for example, a heavy-duty structure having a thickness over 5 mm and/or with stiffened ribs could be casted with a counter piston die casting process without a runner. [0058] A counter piston die casting process according to this disclosure can also include a seal or vent slot design configured to seal the molten metal 119 in the shot sleeve 102 before the cavity filling phase. In some embodiments, the seal design can be a cone face pressing seal 121 and/or a compound face seal as in FIGs.2A-2B. In some embodiments, the cone face pressing seal 121 is disposed between the tapered edges of the counter piston 106 and the shot sleeve 102. In some embodiments, the seal design can be a cylindrical face-fitting seal 321, as shown in FIGs.4A-4D. In some embodiments, the cylindrical face fitting seal 321 is disposed between the straight angle edges of the counter piston 306 and an inner surface of the shot sleeve 302 (See FIG.4A). [0059] A counter piston 106 with the cone face pressing seal 121 can be advantageous over the cylindrical face fitting seal 321 because the cone face pressing seal 121 can reach its sealing position within a shorter distance from its opening position (See FIGs.2A and 4A). The counter piston 106 with the cone face pressing seal 121 can also be more tolerant to a mismatch between a central axis of the shot sleeve 102 and a central axis of the counter piston 106. A counter piston 306 with the cylindrical face fitting seal 321 can be advantageous in that the casting cavity 316 can have an ejector side surface (e.g., a side of the casting cavity 416 facing an ejector side B) that is not limited by the tapered edges of the cone face pressing seal 121. With a cylindrical face fitting seal 321, in some embodiments, the ejector side surface of the casting cavity 316 can be configured to be flat as shown in FIG. 4B. In some embodiments, the ejector side surface of the casting cavity 316 can be configured to be irregular (e.g., angled) with the cylindrical face fitting seal as shown in FIG. 4D. In correspondence, as shown in FIGs.4C-4D, a shot piston 401 can also have an irregular ejector side surface (e.g., a side of the shot piston 401 facing the ejector side B) and a biscuit having an irregular profile. [0060] A counter piston die casting system can also include an ingate design that includes ingate notches or ridges disposed on an end face of the shot sleeve (e.g., a face of the shot sleeve facing the casting cavity). The ingate notches or ridges can be configured to form a desirable pattern on the casting cavity/part. The ingate notches or ridges can have a size (e.g., a width and a thickness) and locations around the biscuit. The size and the locations can be configured according to the intended casting design. FIG.5 illustrates an end face 51 of a shot sleeve 50 having a plurality of ingate notches 52. The shot sleeve 50 can also include a face fitting seal 53 (e.g., press seal face or leading face) disposed on an inner surface of the shot sleeve 50. In some embodiments, the plurality of ingate notches 52 can be distributed around the circular end face 51 as shown in FIG.5. [0061] In some embodiments, a counter piston die casting system can further include one or more notches or ridges disposed on an end face of the counter piston (e.g., a face of the counter piston facing the casting cavity). The one or more notches or ridges of the counter piston can be configured to cooperate with one or more ingate notches or ridges of the shot sleeve to work as a conventional fixed shot distributor (e.g., shot block or shot sprue). The one or more notches or ridges of the counter piston and the one or more ingate notches or ridges of the shot sleeve, in combination, can be configured to adjust a flow of molten metal to preferably flow in a certain way (e.g., a certain direction or in a certain flow rate) and form a desirable pattern on the casting cavity/part as shown in FIGs.6A-6B. FIG.6B shows an end face 61 of a shot sleeve 61 having an ingate notch 62 and a face fitting seal 63 (e.g., press seal face or leading face). FIG. 6A shows an end face 67 of a counter piston 66 having a ridge 65 disposed on the end face 67 and configured to cooperate with the ingate notch 62. The counter piston 66 can also include a face fitting seal 65 (e.g., press seal face or leading face) disposed on the end face and configured to cooperate with the face fitting seal 63. [0062] An embodiment of a counter piston die casting system that employs a vent slot 716 to facilitate sealing between a shot sleeve 702 and a counter piston 706 is illustrated Figures 7A-7B. As shown in FIG. 7B, the shot sleeve 702 having an end face 721 and a plurality of ingate notches 722 can include the vent slot 716 disposed on the end face 721. FIG. 7A shows that the shot sleeve 702 can be configured to contact the counter piston 706 such that only a lower portion of the end face 721 of the shot sleeve 702 is sealed, and the shot sleeve 702 can be configured to be linked with a casting cavity or ambient air for venting purpose. It may be advantageous to include the vent slot 716 in the sealing design when a conventional venting process (e.g., no venting port in the shot sleeve as shown in FIGs. 2A- 2D) is used. [0063] A counter piston and/or a counter piston sleeve for a counter piston die casting system according to this disclosure can have a structural design similar to that of a conventional solid shot piston and/or a shot sleeve. For example, the fitting clearance between a counter piston and a counter piston sleeve can be maintained to be within a similar range as the fitting clearance between a conventional solid shot piston and a shot sleeve. The counter piston die casting system can also employ a thermal control methodology similar to that of a conventional die casting system, but with a tighter control to maintain a more uniform shape of the end face of the counter piston for seal purposes. In some embodiments, internal cooling can be implemented with the counter piston and its sleeve, for example, with 3-D printing manufacturing. An expected service life of a counter piston can be much longer than a conventional solid shot piston because the counter piston can have a shorter moving stroke and lower moving speed. [0064] In some embodiments, a counter piston’s position can be controlled by a driving cylinder 108 in an ejector box, as shown in FIGs. 2A-2D. The driving cylinder 108 can apply pressure to properly seal surfaces between the counter piston 106 and the shot sleeve 102. In some embodiments, the driving cylinder 108 can also control the motion of the counter piston 106 based on a timing requirement of the die casting process. In other embodiments, as shown in FIG. 8, motion of the counter piston 806 can be controlled by a circuit 800 (e.g., a hydraulic circuit). In some embodiments, the hydraulic circuit 800 can include a two-position servo valve, a pressure release valve, a driving motor, and an oil tank. In some embodiments, the die casting system can further include a die casting machine control system to send signals for controlling a servo valve. [0065] In some embodiments, a counter piston die casting system can include a die opening phase, during which a solidified casting part can be removed from a casting cavity. As shown in FIG. 9, a counter piston 906 can be moved out of a counter piston sleeve 915 towards an injection side A at a third position to push a solidified casting part out of a casting cavity 916 during the die opening phase. In some embodiments, the counter piston die casting system can include one or more air blow-off channels 925 configured to blow air and clean debris, if any, out of a counter piston pocket 926 disposed between the counter piston 906 and the counter piston sleeve 915. In some embodiments, the one or more air blow-off channels 925 can be disposed on a surface (e.g., a surface facing the counter piston) of an ejector main insert 905. In other embodiments, the one or more air blow-off channels 925 can be disposed on one or more shock absorber plates 924 attached to a surface (e.g., a surface facing the counter piston) of an ejector main insert 905. In some embodiments, the one or more air blow- off channels 925 can be implemented on the one or more shock absorber plates 924 by one or more built-in air nozzles. During the die opening phase, after cleaning the counter piston (e.g., the air blow-off cleaning), external oil spray can also be applied onto the counter piston for lubrication. [0066] The foregoing disclosure is not intended to limit the present disclosure to the precise forms or particular fields of use disclosed. As such, it is contemplated that various alternate embodiments and/or modifications to the present disclosure, whether explicitly described or implied herein, are possible in light of the disclosure. Having thus described embodiments of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made in form and detail without departing from the scope of the present disclosure. Thus, the present disclosure is limited only by the claims. [0067] In the foregoing specification, the disclosure has been described with reference to specific embodiments. However, as one skilled in the art will appreciate, various embodiments disclosed herein can be modified or otherwise implemented in various other ways without departing from the spirit and scope of the disclosure. Accordingly, this description is to be considered as illustrative and is for the purpose of teaching those skilled in the art the manner of making and using various embodiments of the disclosed counter-piston die casting system or process. It is to be understood that the forms of disclosure herein shown and described are to be taken as representative embodiments. Equivalent elements, materials, processes or steps may be substituted for those representatively illustrated and described herein. Moreover, certain features of the disclosure may be utilized independently of the use of other features, all as would be apparent to one skilled in the art after having the benefit of this description of the disclosure. Expressions such as "including", "comprising", "incorporating", "consisting of", "have", "is" used to describe and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. [0068] Further, various embodiments disclosed herein are to be taken in the illustrative and explanatory sense, and should in no way be construed as limiting of the present disclosure. All joinder references (e.g., attached, affixed, coupled, connected, and the like) are only used to aid the reader's understanding of the present disclosure, and may not create limitations, particularly as to the position, orientation, or use of the systems and/or methods disclosed herein. Therefore, joinder references, if any, are to be construed broadly. Moreover, such joinder references do not necessarily infer that two elements are directly connected to each other. Additionally, all numerical terms, such as, but not limited to, "first", "second", "third", "primary", "secondary", "main" or any other ordinary and/or numerical terms, should also be taken only as identifiers, to assist the reader's understanding of the various elements, embodiments, variations and/or modifications of the present disclosure, and may not create any limitations, particularly as to the order, or preference, of any element, embodiment, variation and/or modification relative to, or over, another element, embodiment, variation and/or modification. [0069] It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application.

Claims

WHAT IS CLAIMED IS: 1. A die casting machine having an ejector side and an injection side, comprising: a counter piston disposed on the ejector side; a shot piston disposed on the injection side; and a shot sleeve configured to receive the shot piston and a liquid. 2. The die casting machine of Claim 1, wherein the counter piston is movable between a first position and a second position. 3. The die casting machine of Claim 2, wherein when the counter piston is in the first position, the liquid is allowed to flow from the shot sleeve to a casting cavity. 4. The die casting machine of Claim 2, wherein when the counter piston is in the second position, the liquid is prevented from flowing from the shot sleeve to a casting cavity. 5. The die casting machine of Claim 2, wherein when the counter piston is in the second position, the shot sleeve is sealed off by the counter piston from a casting cavity. 6. The die casting machine of Claim 5, wherein the counter piston comprises a tapered edge on a side facing the shot sleeve to create a pressing seal with a tapered edge of the shot sleeve on a side facing the counter piston. 7. The die casting machine of Claim 1, wherein the counter piston has a non- uniform surface facing the shot sleeve, the non-uniform surface configured to form a corresponding non-uniform surface on a casting part. 8. The die casting machine of Claim 2, wherein the counter piston is further movable to a third position. 9. The die casting machine of Claim 8, wherein when the counter piston is in the third position, the counter piston is out of a counter piston sleeve for cleaning and lubrication. 10. The die casting machine of Claim 1, wherein the shot sleeve comprises a pour hole configured to allow the liquid to enter the shot sleeve. 11. The die casting machine of Claim 1, wherein the shot sleeve comprises a vent port configured to allow air to leave the shot sleeve. 12. The die casting machine of Claim 1, wherein the counter piston is connected to a driving cylinder, the driving cylinder configured to control motion of the counter piston. 13. A die casting process employing a counter piston, the process comprising: moving the counter piston to at least partially contact a shot sleeve so as to prevent a liquid from flowing from through the shot sleeve to a casting cavity; sliding a shot piston inside the shot sleeve so as to remove air from inside the shot sleeve; and moving the counter piston away from the shot sleeve so as to allow the liquid to enter the casting cavity. 14. The die casting machine of Claim 13, further comprising moving the counter piston out of a counter piston sleeve for cleaning and lubrication. 15. The die casting machine of Claim 13, further comprising pouring the liquid into the shot sleeve through a pour hole on the shot sleeve. 16. The die casting machine of Claim 13, wherein removing air from inside the shot sleeve comprises removing air from the shot sleeve from a vent port on the shot sleeve. 17. A die casting machine configured to control a flow of molten metal into a casting cavity during a third phase, comprising: a housing; a shot sleeve slidingly disposed in the housing and forming a receptacle, the receptacle being configured to receive the molten metal and a gas during a first phase; a shot piston configured to slide in the shot sleeve so as to remove the gas from the receptacle during a second phase leaving the molten metal; and a counter piston slidingly disposed in the housing so as to prevent the molten metal from entering the casting cavity during the first and second phases while allowing the molten metal to enter the casting cavity during the third phase. 18. The die casting machine of Claim 17, wherein the counter piston comprises a tapered edge on a side facing the shot sleeve to create a pressing seal with a tapered edge of the shot sleeve on a side facing the counter piston. 19. The die casting machine of Claim 17, wherein the counter piston has a non- uniform surface facing the shot sleeve, the non-uniform surface configured to form a corresponding non-uniform surface on a casting part. 20. The die casting machine of Claim 17, wherein the counter piston is connected to a driving cylinder, the driving cylinder configured to control motion of the counter piston.