Mold and method for sectionally adjusting cooling efficiency of the mold

Abstract

The present invention provides a method for sectionally controlling a cooling efficiency of a mold. The method comprises steps of: (a) configuring at least a cooling passage including a first section having a first heat-dissipating inner surface area and a second section having a second heat-dissipating inner surface area in the mold; and (b) adjusting the first and the second heat-dissipating inner surface areas unequally by using a heat-dissipating element.

Claims

What is claimed is: 1 . A method for sectionally controlling a cooling efficiency of a mold, comprising steps of: configuring at least a cooling passage including a first section having a first heat-dissipating inner surface area and a second section having a second heat-dissipating inner surface area in the mold; and adjusting the first and the second heat-dissipating inner surface areas unequally by using a heat-dissipating element. 2 . A method as claimed in claim 1 , wherein the mold includes a hot-stamping die. 3 . A method as claimed in claim 1 , wherein the heat-dissipating element includes at least one of a fin and a foil. 4 . A method as claimed in claim 1 , wherein the step of adjusting the first and the second heat-dissipating inner surface areas is performed by increasing at least one of the first heat-dissipating inner surface area and the second heat-dissipating inner surface area. 5 . A method as claimed in claim 1 , wherein the cooling passage includes a first and a second cooling sub-passages having the first and the second heat-dissipating inner surface areas respectively. 6 . A method as claimed in claim 1 , wherein the first and the second sections are disposed in different locations of the mold. 7 . A method as claimed in claim 1 , wherein the cooling passage includes an upstream and a downstream sections, the first section is located at the upstream section, and the second section is located at the downstream section. 8 . A method for sectionally controlling a cooling efficiency of a mold, comprising steps of: configuring a cooling passage having a heat-dissipating inner surface area in the mold; and disposing a heat-dissipating element in the cooling passage for causing the heat-dissipating inner surface area to be inhomogeneous. 9 . A method as claimed in claim 8 , wherein the heat-dissipating element includes at least one of a fin and a foil. 10 . A method as claimed in claim 8 , wherein the cooling passage includes an upstream and a downstream sections, and the heat-dissipating element is disposed at one of the upstream section and the downstream section. 11 . A method as claimed in claim 8 , wherein the cooling passage includes a first and a second cooling sub-passages having different heat-dissipating inner surface areas. 12 . A method as claimed in claim 11 , wherein the first and the second cooling sub-passages are disposed in different locations of the mold. 13 . A method as claimed in claim 8 , wherein the mold includes a hot-stamping die. 14 . A mold for molding an object comprising: a cooling passage device having a heat-dissipating inner surface area; and a heat-dissipating element disposed in the cooling passage device for causing the heat-dissipating inner surface area to be inhomogeneous. 15 . A mold as claimed in claim 14 , further comprising: a lower mold base having a top surface and including a cooling channel disposed on the top surface; and a lower mold cover disposed above the lower mold base, and covering the cooling channel to form the cooling passage device. 16 . A mold as claimed in claim 15 , wherein the heat-dissipating element is disposed on at least one of the lower mold base and the lower mold cover. 17 . A mold as claimed in claim 14 , wherein the mold includes a hot-stamping die. 18 . A mold as claimed in claim 14 , wherein the heat-dissipating element includes at least one of a fin and a foil. 19 . A mold as claimed in claim 14 , wherein the cooling passage device includes a first and a second cooling passages, and the heat-dissipating element is disposed in at least one of the first and the second cooling passages. 20 . A mold as claimed in claim 19 , wherein the first and the second cooling passages are disposed in different locations of the mold.
FIELD OF THE INVENTION [0001] The present invention claims the benefits of priority from the Taiwanese Patent Application No. 100142109, filed on Nov. 17, 2011, the contents of the specification of which are hereby incorporated herein by reference. The present invention relates to a mold and a method for adjusting cooling efficiency, particularly a hot-stamping mold and a method of sectionally adjusting the cooling efficiency of the hot-stamping mold. BACKGROUND OF THE INVENTION [0002] The production method for a cooling water passage according to the prior art is to drill a mold to form tunnels therein for allowing cooling water to flow in the tunnels. Due to the physical limitations of the drilling machine, each of the tunnels formed in the mold is in one direction, i.e. strait lines. However, the contours of a mold are usually curvature. Thus, the distance between the cooling water passages made by drilling inside the mold and the outer surface of the mold cannot be constant, which results in deficiencies such as inhomogeneous cooling effect at different areas and ineffective temperature control during a hot-stamping process using the mold. [0003] The hot-stamping technology has advantages including easy-forming, good mechanical properties of the formed elements, small amount of springing back and etc. The material processed with hot-stamping is heated up to 900 degrees Celsius and then is cooled down rapidly (quenched), which improves the strength of the material in a great deal. Such a quenching effect obtained with a hot-stamping mold (or die) has a large influence to the mechanical properties of the end products, particularly in the field of automobile industry where the hot-stamping process has been broadly adopted. The mechanical properties (for example, hardness and vibration absorption) of the end products of the automobile industry are of series concerns for the sake of safety as well as weight reduction. [0004] The allocation design for those cooling passages according to the prior art is focused the effect of heat release only, but never considers an improvement for homogeneous heat transferring during and after the hot-stamping process which requires precise calculations for better structure designs of the cooling passages. Consequently, the use of many of these hot-stamping molds results in even mechanical properties of the products, or even causes deformations or cracks of the end products. [0005] Some of the prior arts provide methods of changing the cooling rate by controlling the water flow, employing multiple number of cooling passages, or changing the dimensions (such as the cross section of the cooling tunnel) of the mold, which may resolve the issue of broken steel plates due to abrupt cooling. However, such methods involve exhausting calculations for determining the metal mold dimensions based on the cooling speeds, and are not applicable for producing products with different mechanical properties at various portions. Besides, with the restrictions of the shape of the mold, sometimes it is not applicable to increase the density of cooling tunnels inside the mold. SUMMARY OF THE INVENTION [0006] To overcome the abovementioned defects of the prior arts, the present invention provides novel structural designs of the cooling passages for sectionally adjusting the cooling efficiency of a mold, without changing the density of the cooling passages or the cooling water flow rate. The present invention unequally adjusts the heat-dissipation rate or cooling efficiency at different portions of the mold by changing the heat-dissipation surface of the cooling passages at different areas so as to obtain different mechanical properties such as hardness and strength of the products at different areas thereof. [0007] According to one embodiment of the present invention, the present provides a method for sectionally controlling a cooling efficiency of a mold. The method comprises steps of: (a) configuring at least a cooling passage including a first section having a first heat-dissipating inner surface area and a second section having a second heat-dissipating inner surface area in the mold; and (b) adjusting the first and the second heat-dissipating inner surface areas unequally by using a heat-dissipating element. [0008] In accordance with another aspect of the present invention, a method for sectionally controlling a cooling efficiency of a mold is provided. The method comprises steps of: (a) configuring a cooling passage having a heat-dissipating inner surface area in the mold; and (b) disposing a heat-dissipating element in the cooling passage for causing the heat-dissipating inner surface area to be inhomogeneous. [0009] In accordance with a further aspect of the present invention, a mold for molding an object is provided. The mold comprises a cooling passage and a heat-dissipating element. The cooling passage device has a heat-dissipating inner surface area. The heat-dissipating element is disposed in the cooling passage device for causing the heat-dissipating inner surface area to be inhomogeneous. [0010] The above objects and advantages of the present invention will be more readily apparent to those ordinarily skilled in the art after reading the details set forth in the descriptions and drawings that follow, in which: BRIEF DESCRIPTION OF THE DRAWINGS [0011] FIGS. 1A to 1C are schematic diagrams showing a mold having multiple cooling passages in accordance with one embodiment of the present invention; [0012] FIG. 2 is a schematic diagram showing another embodiment of the heat-dissipating element; [0013] FIGS. 3A to 3E illustrates a method for manufacturing a mold having multiple cooling passages according to the present invention; [0014] FIG. 4 is a schematic diagram showing a cross section according to a further embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT [0015] The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for the purposes of illustration and description only; it is not intended to be exhaustive or to be limited to the precise form disclosed. [0016] An objective of the present invention is to provide a novel design for cooling passages in a mold, so as to render a product having different mechanical properties at different portions thereof. The method is to dispose heat-dissipating elements in the cooling passages of the mold for causing the heat-dissipating inner surface area inhomogeneous and resulting in different cooling efficiencies during the cooling period of the product manufacturing process. [0017] Please refer to FIGS. 1A to 1C , which are schematic diagrams showing a lower mold having multiple cooling passages in accordance with one embodiment of the present invention. Notably, the present embodiment is also applicable to an upper mold (not shown). The lower mold 10 illustrated in FIG. 1A can be used in hot-stamping processes or other mechanical manufacturing processes such as die casting. A mold used in the hot-stamping process is sometimes called a hot-stamping die. According to FIG. 1A , the lower mold 10 comprises several cooling passages 11 . FIGS. 1B and 1C illustrate the cross sections A-A and B-B of the lower mold 10 respectively. It is observed that there are heat-dissipating elements 12 , such as fins, configured inside of the cooling passage 11 at the cross section A-A while no heat-dissipating element 12 in the cooling passage 11 at the cross section B-B. For one particular cooling passage 11 , says the one at the upper right corner, it is appreciated that the heat-dissipating inner surface area (not shown) of the section near the cross section A-A is larger than that of the section near the cross section B-B, and therefore the cooling efficiencies of the section near A-A is higher than that of the section near B-B. The coolants available for the embodiment includes water, vapor, liquid helium, oil, air, and any other material applicable for the use of cooling inside a mold. [0018] The heat-dissipating element 12 shown in FIG. 1B can be either a fastened or a replaceable element. Furthermore, any type of element capable of increasing the heat-dissipating surface of the cooling passage can be used as a heat-dissipating element according to the present invention. FIG. 2 illustrates another embodiment of the heat-dissipating element which is a flexible metal foil 20 fastened by a fastening element 21 in a cooling passage 22 . The metal foil 20 may also be attached on the inner wall of the cooling passage 22 by way of wielding or sticking. Optionally, the material of the metal foil 20 can be any metal with good heat conductivity such as, but not limited to gold, silver, copper, aluminum or alloys of the above metals. A variety of shapes are available as options of the metal foil 20 , as long as the area of the heat-dissipating surface can be increased. [0019] The embodiments set forth above according to the present invention can be realized with many manufacturing processes known to the art. The present invention simply provides an embodiment of a method for manufacturing a mold with heat-dissipating elements disposed in at least one cooling passage of the mold. Referring to FIGS. 3A to 3E , the method comprises the following steps: Firstly, providing a mold base 30 which has a shape the same with that of the embodiment shown in FIGS. 1A to 1C ; Secondly, configuring one or plural cooling passages 31 around the working surface of the mold base 30 , wherein each of the cooling passage 31 has a heat-dissipating inner surface area, as illustrated in FIG. 3B ; Thirdly, providing a lower mold cover 32 . Preferably, the lower mold cover 32 is preferably of a constant thickness, so the cooling passages 31 can be completed with a constant distance to the actual working surface of the finished mold as illustrated in FIG. 3E when the lower mold base 31 is covered by the lower mold cover 32 ; Fourthly, disposing heat-dissipating elements 33 in the cooling passages 31 for causing the heat-dissipating inner surface area to be inhomogeneous. Optionally, the heat-dissipating elements 33 may include fins as illustrated in FIG. 3D , the foil 20 in FIG. 2 or other types of element applicable for adjusting the heat-dissipating surface area of the cooling passages 31 . The heat-dissipating elements 33 may be attached on the inner wall of the cooling passage 31 by wielding or sticking, or be fastened with fasteners. Preferably, the heat-dissipating elements 33 are disposed on locations of the lower mold cover 32 corresponding to the required positions inside the cooling passages 31 when the lower mold cover 32 covers the lower mold base 31 (referring to FIG. 3E ). [0020] Due to the existing of the heat-dissipating elements 33 , the heat-dissipating surface area of this portion is larger than that of the other portions without the heat-dissipating elements 33 , i.e., the heat-dissipating surface area in the cooling passage 31 is inhomogeneous. Thus, the cooling effects along the cooling passage 31 can be sectionally controlled by using the heat-dissipating elements 33 . The skilled person in the art may adjust the heat-dissipating inner surface areas unequally by using a heat-dissipating element 33 . For some products that require at least two different types of performance in terms of mechanical properties at different portions, for example one portion of an automobile body to be strong for maintaining its main structure for the safety of the driver and passenger while the other portion to be ductile and vibration absorbable in case of a collision, the present invention provides a method as well as a mold structure that unequally adjusts the heat-dissipation rate or cooling efficiency at different portions of the mold by changing the heat-dissipation surface areas of the cooling passages at different sections so as to obtain different mechanical properties of the products at different portions thereof. [0021] Please refer to FIG. 4 , which schematics a cross section of another embodiment of the present invention. According to FIG. 4 , a mold 40 includes cooling passages 41 , and heat dissipating elements 42 are configured in some of the cooling passages 41 located in the right portion of the mold 40 for increasing the heat-dissipating inner surface area thereof. Comparing the two (right and left) portions of the mold 40 in FIG. 4 , it is appreciated that the cooling efficiency at the right portion is higher than that of the left portion due to the different heat-dissipating inner surface areas thereinbetween. Consequently, the mechanical properties at the two different portions of a product manufactured with the mold 40 will be different. [0022] According to the abovementioned concept of mold design, the heat dissipating element 42 such as a fin can be utilized to adjust or control the heat-dissipating area of the cooling passages 41 inside a mold 40 based on the requirements relevant to the mechanical properties of different portions of the product without changing the locations of the cooling passages 41 . Notably, such adjustment or control includes either an increase or a decrease of the number, density or surface area of the heat-dissipating elements 42 configured in the cooling passages 41 . The present invention has the advantages of increasing the product's quality as well as performance and reducing product defect rate by sectionally controlling the heat-dissipating surface area without changing the mold structure and the layout of the cooling passages inside the mold. [0023] The cooling passage according to the present invention is a device which may be composed of a plurality of sub-passages connected in parallel or not connected, or a single cooling passage route. Therefore, the device can be called a cooling passage device, which is built in one piece when the cooling passage device is either a single passage route or a plurality of sub-passages connected in parallel. Preferably, a negative pressure is applied to the coolant flowing in the cooling passages 11 , 31 , 41 to increase the flow rate and the cooling rate. The negative pressure can be obtained by using a vacuum pump or a negative pressure pump. Another preferred embodiment is to increase or decrease the dimension of a particular portion of the cooling passage to adjust the cooling rate. This concept may be incorporated with the embodiments of using the heat-dissipating elements 12 , 33 , 42 set forth above, to efficiently adjust and control the cooling efficiency. [0024] It is also notable that the at least two portions of the mold 10 , 30 , 40 having different heat-dissipating inner surface area can be considered as a first and a second sections which may be located in right-and-left, front-and-back, upstream-and-downstream, or any different two locations in the mold 10 , 30 , 40 . EMBODIMENTS [0025] 1. A method for sectionally controlling a cooling efficiency of a mold, comprising steps of: [0026] configuring at least a cooling passage including a first section having a first heat-dissipating inner surface area and a second section having a second heat-dissipating inner surface area in the mold; and adjusting the first and the second heat-dissipating inner surface areas unequally by using a heat-dissipating element. [0027] 2. The method of embodiment 1, wherein the mold includes a hot-stamping die. [0028] 3. The method of embodiment 1, wherein the heat-dissipating element includes at least one of a fin and a foil. [0029] 4. The method of embodiment 1, wherein the step of adjusting the first and the second heat-dissipating inner surface areas is performed by increasing at least one of the first heat-dissipating inner surface area and the second heat-dissipating inner surface area. [0030] 5. The method of embodiment 1, wherein the cooling passage includes a first and a second cooling sub-passages having the first and the second heat-dissipating inner surface areas respectively. [0031] 6. The method of embodiment 1, wherein the first and the second sections are disposed in different locations of the mold. [0032] 7. The method of embodiment 1, wherein the cooling passage includes an upstream and a downstream sections, the first section is located at the upstream section, and the second section is located at the downstream section. [0033] 8. A method for sectionally controlling a cooling efficiency of a mold, comprising steps of: [0034] configuring a cooling passage having a heat-dissipating inner surface area in the mold; and [0035] disposing a heat-dissipating element in the cooling passage for causing the heat-dissipating inner surface area to be inhomogeneous. [0036] 9. The method of embodiment 8, wherein the heat-dissipating element includes at least one of a fin and a foil. [0037] 10. The method of embodiment 8, wherein the cooling passage includes an upstream and a downstream sections, and the heat-dissipating element is disposed at one of the upstream section and the downstream section. [0038] 11. A method as claimed in claim 8 , wherein the cooling passage includes a first and a second cooling sub-passages having different heat-dissipating inner surface areas. [0039] 12. The method of embodiment 11, wherein the first and the second cooling sub-passages are disposed in different locations of the mold. [0040] 13. The method of embodiment 8, wherein the mold includes a hot-stamping die. [0041] 14. A mold for molding an object comprising: [0042] a cooling passage device having a heat-dissipating inner surface area; and a heat-dissipating element disposed in the cooling passage device for causing the heat-dissipating inner surface area to be inhomogeneous. [0044] 15. The mold of embodiment 14, further comprising: [0045] a lower mold base having a top surface and including a cooling channel disposed on the top surface; and [0046] a lower mold cover disposed above the lower mold base, and covering the cooling channel to form the cooling passage device. [0047] 16. The mold of embodiment 15, wherein the heat-dissipating element is disposed on at least one of the lower mold base and the lower mold cover. [0048] 17. The mold of embodiment 14, wherein the mold includes a hot-stamping die. [0049] 18. The mold of embodiment 14, wherein the heat-dissipating element includes at least one of a fin and a foil. [0050] 19. The mold of embodiment 14, wherein the cooling passage device includes a first and a second cooling passages, and the heat-dissipating element is disposed in at least one of the first and the second cooling passages. [0051] 20. The mold of embodiment 19, wherein the first and the second cooling passages are disposed in different locations of the mold. [0052] While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims that are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.

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    WO-2015085399-A1June 18, 2015Magna International Inc.Outil d'estampage à chaud et procédé de fabrication de l'outil