Patent Application
20180056384
The present disclosure relates to a pressure regulator. More specifically, the present disclosure relates to a displacement-pressure regulator for a casting system.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Current manufacturing processes for producing engine components of a motor vehicle, for example, cylinder blocks include high pressure die cast (HPDC) processes. Typically, as molten metal is directed to a mold, HPDC high velocity fill processes entrain air, generate oxides and have difficulty addressing metal shrinkage from certain regions within the mold. Other processes include precision sand casting which employs a bonded sand core pack mold with a large thermal bulk head chill and head deck risers to achieve desired material properties. Precision sand casting, however, is a costly process reserved for components requiring high integrity and enhanced material properties.
Accordingly, there is a need in the art for a cost efficient casting process for producing high quality and performance cast components.
The present invention provides a system to cast mechanical components. Accordingly, in one aspect of the present invention, a casting system includes a first mold, a second mold, the first mold and the second mold being configured to receive molten metal, the first mold and the second mold exerting pressure on the molten metal to form a mechanical component as the molten metal cools, and a sensor that measures the pressure exerted on the molten metal to provide feedback information to regulate the pressure exerted on the molten metal.
The foregoing aspect can be further characterized by one or any combination of the features described herein, such as: the system further includes a pressure punch that receives the feedback information, the pressure punch varying the exerted pressure on the molten metal; the exerted pressure is varied according to a desired time-pressure profile; the sensor is a hydraulic pressure sensor; the sensor is a stack of Belleville washers; the system further includes a plurality of slides positioned within the first mold and the second mold, the positioning of the plurality of slides exerting the direct pressure on the molten metal; the plurality of slides is four slides; and each slide is an insert that reciprocates along a respective channel.
Accordingly, pursuant to another aspect of the present invention, an apparatus to form a mechanical component includes a first mold, a second mold, the first mold and the second mold being configured to receive molten metal, the first mold and the second mold exerting pressure on the molten metal to form a mechanical component as the molten metal cools, and a feedback mechanism that measures the exerted pressure and varies the exerted pressure to a desired time-pressure profile.
The foregoing aspect can be further characterized by one or any combination of the features described herein, such as: the feedback mechanism includes a sensor that measures the exerted pressure; the feedback mechanism includes a pressure punch that receives feedback information from the sensor, the pressure punch varying the exerted pressure on the molten metal; the sensor is a hydraulic pressure sensor; the sensor is a stack of Belleville washers; the apparatus further includes a plurality of slides positioned within the first mold and the second mold, the positioning of the plurality of slides exerting the direct pressure on the molten metal; the plurality of slides is four slides; and each slide is an insert that reciprocates along a respective channel.
Accordingly, pursuant to yet another aspect of the present invention, a method to control a casting process to form a mechanical component includes one or more of the following steps: pouring molten metal into an interior cavity defined by a first mold and a second mold, exerting pressure on the molten metal to form a mechanical component, and measuring the exerted pressure and regulating the exerted pressure according to a desired time-pressure profile.
The method to control the casting process may be further characterized by one or any combination of the following features: measuring and regulating the exerted pressure includes measuring and regulating with a hydraulic pressure sensor; measuring and regulating the exerted pressure includes measuring and regulating with a stack of Belleville washers; and exerting pressure includes exerting pressure with a plurality of slides positioned within the first mold and the second mold.
Further features, advantages, and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the drawings:
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
Referring now to the drawings, a direct squeeze system to cast structural components embodying the principles of the present invention is illustrated therein and designated at 10. Turning in particular to
In the system 10, the molten metal is poured into the respective system with a slow pour velocity. For example, in some arrangements, the pour velocity through the gates 22 is less than 100 cm/sec, preferably less than 50 cm/sec. In contrast, in high pressure die cast (HPDC) systems, the pour velocity exceeds 2000 cm/sec, and, in some arrangements, approaches 3800 cm/sec. A particular benefit of the low speed pour velocity for the system 10 is the quiescent flow of the molten metal as it flows into the molds 16 and 18, which thereby reduces or eliminates turbulence in the flowing molten metal. In comparison to HPDC systems, the non-turbulent flow of the molten metal reduces the entrainment of air in the molten metal, which reduces the creation of structural voids in the structural component 30. In some arrangements, the surface of the interior cavity 28 is coated with a pressure sensitive coating, which enhances heat transfer and directional solidification, since the coating has a high thermal resistance with no pressure and low or no thermal resistance with high pressure. An example of such a coating is Trabo™ available from REL, Inc.
Generally, molten metal shrinks as it cools. For example, aluminum shrinks about 6% as it solidifies. Another feature of the systems 10 and 100, is the ability to compensate for the shrinkage of the molten metal as it cools and solidifies. Specifically, as shown in
Note also, that the positioning of the top mold 16 and the bottom mold 18 exerts or applies controlled direct pressure on the cooling molten metal as well. For example,
Referring to
Hence, when the system 10 is in use, molten metal 30 is poured into the interior cavity 28 defined by the molds 16 and 18. The pressure punch 82 is pressed into the molten metal 30 to apply a desired pressure 100 (
In sum, the molds 16 and 18 are closed and mechanically locked except for a direct pressure punch detail. Molten metal, such as, for example, aluminum alloy quietly fills the mold cavity with approximately 10% overfill. The mold cavity is vented around the pressure punch or other locations. The direct pressure punch sequences shutting off the flow of molten metal through the downgate 14 and the ingates 22. The desired pressure is set and held until the mechanical component 30 solidifies. The molds 16 and 18 are opened and the mechanical component is removed.
The displacement-pressure regulator can provide basic functions during the castings process, including providing measurement of internal hydrostatic molten metal pressure for feedback control of pressure applied by pressure punch(s), and providing repository for excess molten metal added to compensate the approximately 6% metal shrinkage when aluminum alloy transitions from liquid to solid. Note that 6 to 10% excess molten metal is added to the mold cavity to offset the 6% metal shrinkage, and pressure punch(s) and other moving mold slides are able to move to their dimensional set points and excess metal not used to offset liquid to solid shrinkage such that casting dimensions are met. Further, excess repository metal can be removed by machining. Moreover, the displacement-pressure regulator enables molten metal displacement repositories to act as kinetic risers with the ability to feed metal shrinkage in regions with desirable feed-paths to repositories. Kinetic risers are kept active through insulating or externally heating them to allow molten metal in repositories to remain liquid for an extended period of time.
One or both the sensors 70 and 72 can be a stack of Bellville washers 90 (
The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
