CN112848179B - A pith-shaped cooling mold and its forming method - Google Patents

Abstract

The invention discloses a pith-shaped cooling die which comprises a die body and a pith-shaped structure (4) arranged in an inner cavity of the die body, wherein the die body comprises a die working surface (3), a cooling medium inlet (1) and a cooling medium outlet (2) which are arranged on the side surface of the die body, and the cooling medium inlet (1) and the cooling medium outlet (2) are respectively communicated with a cooling medium flowing pith gap (5) in the pith-shaped structure (4). The invention also discloses a forming method of the marrow-shaped cooling die. The invention adopts a pith-shaped structure to replace a hollow tubular runner, and has more uniform temperature distribution, larger cooling space, better cooling effect, higher mold strength and longer service life. The invention can realize the uniform cooling of the working part of the die and the product without blind areas, greatly improves the cooling efficiency and the die service life of the industries of injection molding, casting, stamping and the like, reduces the cost of the finished piece and improves the product quality.

Description

A pith-shaped cooling mold and its forming method

technical field

The invention relates to a pituitary cooling mold and a forming method thereof, belonging to the field of mold manufacturing.

Background technique

Mold, known as the "mother of industry", is an indispensable and important equipment in modern industrial production. The level of mold technology is an important symbol to measure a country's comprehensive manufacturing capacity. The cooling system of the mold is its core part, which determines the product quality, production efficiency and mold life.

In order to quickly adjust the temperature of the mold and realize rapid cooling of the working parts of the mold, the traditional method is to use a drill to drill straight holes on the mold to form a straight-hole cooling channel, and fill the cooling medium (usually cooling water) into the straight-hole cooling channel. or oil) to remove heat, this method has been used for many years and is still commonly used today. The advantage of this technical method is that it is simple and easy to implement. The disadvantage is that the cooling channel can only be arranged in a local area. There is a cooling blind zone), high temperature, and uneven temperature lead to low product quality (such as warping, poor consistency, poor surface quality, etc.), low production efficiency, and short mold life. This problem is especially prominent when the product structure is complex . Fundamentally, this straight-bore cooling runner is the result of straight-line thinking. The emergence of additive manufacturing (3D printing) technology makes it possible to change the traditional straight-hole cooling channel into a curved-hole cooling channel. Using additive manufacturing technology, the cooling channel bends inside the mold and follows the working part The runners arranged in different shapes are usually called conformal cooling runners. On this basis, in order to improve cooling efficiency, such patents with application numbers 201810529989.3 and 201711344657.X partially treat the inner wall of the curved hole conformal cooling channel to promote the formation of turbulent flow and improve heat exchange efficiency; in order to increase the cooling medium The contact area with the mold reduces the cooling blind area. The patent application number 201310559377.6 proposes to set a parallel, series and parallel combination of labyrinth cooling channels in the hollow layer at a certain distance from the surface of the working part.

From the point of view of actual application effect, the curved-hole conformal cooling channel based on 3D printing can improve the cooling effect and product quality of the mold to a certain extent. But fundamentally speaking, this type of conformal cooling channel or improved conformal cooling channel is still the result of curved thinking and an extension of linear thinking, as long as it is linear (whether straight or curved) Runner thinking, there must be cooling blind spots, because there are always areas near and far from the runner. No matter how local improvements are made, the thinking of straight or curved runners cannot give full play to the advantages of 3D printing to construct complex spatial structures. This kind of runner design thinking needs to be completely reformed.

Pill cooling abandons linear and curved flow channel design and application technology thinking. Based on the principle of bionics, it directly uses the three-dimensional structure of the pit cooling method. Through the establishment of a three-dimensional pit structure, the working part of the mold is spatially controlled. And products are uniformly cooled without blind spots. When the cooling medium flows through the medullary gap of the medullary structure, a turbulent flow with high heat transfer effect is naturally formed, which fundamentally solves the problem of uniform cooling of molds and parts in industries such as injection molding, casting, and stamping. performance, cooling efficiency, product quality and mold life issues.

Contents of the invention

The purpose of the present invention is to provide a pith-shaped Cooling (Marrow Cooling, MC for short) mold and its forming method.

The pituitary cooling mold of the present invention comprises a mold body and a pituitary structure arranged in the inner cavity of the body, the mold body includes a mold working surface and a cooling medium inlet and a cooling medium outlet arranged on the side of the mold body, the cooling medium inlet and the cooling medium outlet The cooling medium outlets communicate with the cooling medium flowing medullary spaces in the medullary structure respectively.

Further, the distance between the surface of the working part of the mold and the medullary structure is 2-12 mm, preferably 3 mm.

Further, the medullary structure includes an array unit body, and the shape of the array unit body is a cross, a diamond, an X, or a zigzag, or a combination of two or more of them.

The forming method of pituitary cooling mold of the present invention, comprises the following steps:

(1) Imitate the human skeleton and bone marrow structure, set a bone marrow-shaped structure on the part that needs to be cooled, establish a three-dimensional data model of the medullary cooling mold, and control the cooling by adjusting the distance between the surface of the mold working part and the medullary structure and the flow rate of the cooling medium Speed, the medullary structure is composed of arrayed unit bodies, the unit bodies are connected to each other to form a bone marrow-shaped cooling medium flowing marrow gap, and at the same time play a supporting and strengthening role. The cooling medium can flow through the marrow gap to form turbulent flow and efficiently complete the heating Exchange and take away the heat of the working part to achieve rapid and uniform cooling of the surface of the working part and products;

(2) Using metal 3D printing technology to print the three-dimensional data model, reserve a margin on the surface of the mold during printing, remove the internal stress of the mold through heat treatment after printing, and increase the hardness of the mold at the same time;

(3) According to the surface quality requirements of the working part of the mold, the mold surface allowance is removed by machining and polished to obtain the required pith-shaped cooling mold.

The shapes of the array units in the pituitary cooling mold include but are not limited to cross, diamond, X, Pozi, and combinations of various shapes, and the size and distribution of the units are adjusted according to the mold shape and cooling requirements , the unit cells are preferably a cross-shaped uniform array of the same size.

The cooling medium includes but not limited to water, liquid, oil, gas, preferably cooling oil.

The metal 3D printing technology includes but not limited to selective laser melting technology, electron beam melting technology, ion beam melting technology, laser cladding molding technology, preferably selective laser melting molding.

The reserved margin on the mold surface is 0.2-2 mm, preferably 0.8 mm.

The heat treatment process is formulated according to the mold material. After heat treatment, the mold hardness reaches 50-60HRC. The mold material is preferably 18Ni300 mold steel. When the mold material is 18Ni300 mold steel, the heat treatment method is 490 degrees Celsius for 6 hours, and then cooled with the furnace, the mold The hardness reaches 55HRC.

The machining method for removing the mold surface allowance is preferably CNC machining.

For the medullary cooling mold obtained by forming according to the above-mentioned forming method, in order to avoid contamination and blockage during use, the circulating cooling medium should be filtered.

A kind of pituitary cooling mold and forming method thereof of the present invention have following advantages:

First, the medullary cooling abandons the linear and curved flow channel design and the application of technical thinking, so that the medullary structure spreads over the entire working area that needs to be cooled, and there is no cooling blind area, which fundamentally solves the problem of cooling uniformity;

The second is that the medullary cooling can fundamentally solve the problem of cooling efficiency. There are three reasons: (1) No need to use other additional technologies and structures. High efficiency and low cost; (2) The medullary structure spreads all over the working part area, and the cooling medium can take away the heat in time, and the cooling efficiency is high; (3) The medullary structure is connected to the working part, and the heat from the working part reaches the medullary structure through heat conduction , and the medullary structure is surrounded by cooling medium, the heat can be taken away instantly, and the cooling efficiency is high;

The third is that the pith-shaped cooling enables the working parts of the mold to achieve rapid and uniform cooling, the product surface quality is high, there is no warping deformation, and the product consistency is good, which fundamentally solves product quality problems;

Fourth, the cooling medium can reach any position of the working part, and there is no blind area, so that the temperature distribution of the working part of the mold is even, and there is no thermal stress inside the mold, which improves the service life of the mold;

Fifth, the linear and curved cooling runners form cavities inside the mold. The denser the runners, the more cavities, the lower the strength of the mold, and the medullary structure is connected to each other, which not only ensures that the cooling medium can have no blind spots. It can accurately reach all areas that need to be cooled, and ensure the strength of the mold, fully demonstrating the advantages of light weight and high strength of bone bionics;

Sixth, during the use of the pith-shaped cooling mold, the circulating filtered cooling medium is used to avoid pollution and blockage, and there is no need for complicated special coatings or structural changes. It is simple, easy to implement, low in cost, and has good effects. Application prospect.

Description of drawings

Fig. 1 is a schematic structural view of an embodiment of a pituitary cooling mold of the present invention.

Fig. 2 is a segmental sectional view of an embodiment of the pituitary cooling mold of the present invention.

Fig. 3 is a planar sectional view of an embodiment of the pituitary cooling mold of the present invention.

Fig. 4 is a schematic diagram of a cross-shaped medullary structural unit array of an embodiment of the medullary cooling mold of the present invention.

Fig. 5 is a schematic diagram of a diamond-shaped medullary structural unit array of an embodiment of the medullary cooling mold of the present invention.

Fig. 6 is a schematic diagram of an X-shaped medullary structural unit array of an embodiment of the medullary cooling mold of the present invention.

In the figure: 1. Cooling medium inlet, 2. Cooling medium outlet, 3. Working surface of the mold, 4. Pill-shaped structure, 5. Cooling medium flowing pit.

Detailed ways

The pituitary cooling mold and its forming method of the present invention will be described in detail below with reference to the specific accompanying drawings 1-6 and the embodiments.

As shown in Figures 1-3, a pituitary cooling mold of the present invention includes a mold body and a pituitary structure 4 arranged in the inner cavity of the body, and the mold body includes a mold working surface 3 and a cooling medium arranged on the side of the mold body The inlet 1 and the cooling medium outlet 2 , the cooling medium inlet 1 and the cooling medium outlet 2 communicate with the cooling medium flow medullary space 5 in the medullary structure 4 respectively.

The distance between the surface 3 of the working part of the mold and the medullary structure 4 is 2-12 mm, preferably 3 mm.

As shown in Figures 4-6, the medullary structure 4 includes an array unit body, and the shape of the array unit body is cross-shaped, diamond-shaped or X-shaped, and can also be in the shape of a rice, or in the shape of a cross, diamond-shaped, or X-shaped , M-shaped and other combinations of two or more shapes.

The size and distribution of the unit cells are adjusted according to the mold shape and cooling requirements. Preferably, the unit cells are a cross-shaped uniform array with the same size.

The medullary structure 4 of the present invention is formed by 3D printing.

A kind of forming method of pituitary cooling mold of the present invention, comprises the following steps:

The first step is to imitate the structure of human bones and bone marrow, and set a bone marrow-shaped structure on the part that needs to be cooled, and establish a three-dimensional data model of the marrow-shaped cooling mold. Cooling speed, the medullary structure is composed of arrayed unit bodies, the unit bodies are connected to form a bone marrow-shaped cooling medium flowing in the medullary gap, and at the same time play a supporting and strengthening role. The cooling medium can flow through the medullary gap to form turbulent flow and complete efficiently Heat exchange and take away the heat of the working part to realize rapid and uniform cooling of the surface of the working part;

The second step is to use metal 3D printing technology to print the three-dimensional data model, reserve a margin on the surface of the mold during printing, and remove the internal stress of the mold through heat treatment after printing, and at the same time increase the hardness of the mold;

In the third step, according to the surface quality requirements of the working part of the mold, the surface allowance of the mold is removed by machining and polished to obtain the required pith-shaped cooling mold.

The shape of the array unit body in the pituitary cooling mold includes but not limited to cross, diamond, X, Pozi, and a combination of various shapes, the size and distribution of the unit body are adjusted according to the shape of the mold and cooling requirements, the unit The volumes are preferably a cross-shaped uniform array of equal size.

The cooling medium includes but not limited to water, liquid, oil, gas, preferably cooling oil.

Metal 3D printing technologies include but are not limited to selective laser melting technology, electron beam melting technology, ion beam melting technology, laser cladding molding technology, preferably selective laser melting forming.

The margin reserved on the mold surface is 0.2-2mm, preferably 0.8mm.

The heat treatment process is determined according to the mold material. After heat treatment, the mold hardness reaches 50-60HRC. The mold material is preferably 18Ni300 mold steel. Not less than 55HRC.

The machining method for removing the mold surface allowance is preferably CNC machining.

For the medullary cooling mold obtained by forming according to the above-mentioned forming method, in order to avoid contamination and blockage during use, the circulating cooling medium should be filtered.

Example 1:

Print a pituitary cooling injection mold according to the following technical steps: the first step is to establish a three-dimensional data model of the pituitary cooling mold, the distance between the surface of the mold working part and the pituitary structure is 3mm, and the pith structure consists of a uniform array of diamond-shaped units Composition, using circulating filtered water as the cooling medium, the cooling water flows through the medullary gap to form turbulent flow; the second step is to print the medullary cooling mold by using the mold steel material 18Ni300 through the selective laser melting 3D printing technology, and the printer model is EOSM290, 0.8mm margin is reserved on the surface of the mold during printing. After printing, the mold is kept at 490 degrees Celsius for 6 hours, and then cooled with the furnace to remove the internal stress of the mold and increase the hardness of the mold to 56HRC; the third step is to remove it by CNC machining The surface allowance of the mold is polished, so that the precision grade of the mold is IT7, and the surface quality of the working surface reaches A1, so as to obtain the required pith-shaped cooling mold. Use this pith-shaped cooling mold to carry out injection molding experiments of polypropylene materials, test the cooling time and the warpage of the part (sample code SM-1), and use the traditional straight hole type and the curved hole type with conformal cooling under the same conditions The results obtained by cooling the mold are compared and listed in Table 1.

Example 2:

Print a pituitary cooling die-casting mold according to the following technical steps: the first step is to establish a three-dimensional data model of the pith cooling mold, the distance between the surface of the mold working part and the pith structure is 4mm, and the pith structure is composed of cross-shaped units in a uniform array Composition, the circulating filtered oil is used as the cooling medium, and the cooling oil flows through the marrow gap to form a turbulent flow; the second step is to print the marrow-shaped cooling mold by using the H13 mold steel material through the selective laser melting 3D printing technology, and the printer model is ConceptLaser M2, when printing, reserve 0.6mm margin on the surface of the mold. After printing, the mold is kept at 460 degrees Celsius for 9 hours, and then cooled with the furnace to remove the internal stress of the mold, and at the same time increase the mold hardness to 58HRC; the third step is through CNC machining Remove the mold surface allowance and perform polishing treatment, so that the mold precision grade is IT6 grade, and the surface quality of the working surface reaches A2 grade, so as to obtain the required pith-shaped cooling mold. Use this pith-shaped cooling mold to carry out the die-casting experiment of 6061 aluminum alloy, test the cooling time and the warpage deformation of the part (sample number YZ-1), and use the traditional straight hole type and the curved hole type with conformal cooling under the same conditions The results obtained by cooling the mold are compared and listed in Table 1.

Implementation effect comparison:

The parameter comparison of the implementation effect is shown in Table 1. In the injection molding experiment, the cooling time and part warpage of the curved-hole cooling mold with conformal cooling were reduced by 31.7% and 28% respectively compared with the traditional straight-hole cooling mold, and the pith-shaped cooling mold was faster than the curved-hole cooling mold. The cooling time and workpiece warpage are reduced by 67.9% and 94.4% respectively, which are 78% and 96% lower than those of the straight-hole cooling mold. In the die-casting experiment, the cooling time and part warpage of the curved-hole cooling mold with conformal cooling were reduced by 44.1% and 27.6% respectively compared with the traditional straight-hole cooling mold, and the pith-shaped cooling mold was faster than the curved-hole cooling mold. The cooling time and part warpage are reduced by 61.5% and 85.7% respectively, which are 78.5% and 89.7% lower than those of the straight-hole cooling mold. It can be seen from the implementation process and effect that the traditional straight-hole or curved-hole cooling methods can only arrange cooling channels in local areas. The cooling effect is good and the temperature is low near the cooling channels. The cooling effect is not good in the place where the runner is far away (that is, there is a cooling blind area), the temperature is high, and the uneven temperature leads to low product quality (such as warping deformation, poor consistency, poor surface quality, etc.), low production efficiency, and short mold life. , the more complex the product structure, the more prominent this problem will be.

The medullary cooling provided by the present invention abandons the linear and curved flow channel design and application technical thinking, so that the medullary structure spreads over the entire working part area that needs to be cooled, and there is no cooling blind area, which fundamentally solves the problem of cooling uniformity . Medullary cooling does not need to use other additional technologies and structures. When the cooling oil flows through the medullary structure, it will naturally form turbulent flow, with high heat transfer efficiency and low cost; Walking, high cooling efficiency; the medullary structure is connected to the working part, the heat of the working part reaches the medullary structure through heat conduction, and the surrounding of the medullary structure is full of cooling medium, the heat can be taken away instantly, and the cooling efficiency is high. In this way, the medullary cooling can Fundamentally solve the problem of cooling efficiency. The pith-shaped cooling enables the working parts of the mold to achieve rapid and uniform cooling, the product has high surface quality, no warping deformation, and good product consistency, which fundamentally solves product quality problems. The cooling medium can reach any position of the working part, so that the temperature distribution of the working part of the mold is uniform, and there is no thermal stress inside the mold, which improves the service life of the mold. Both linear and curved cooling runners form cavities inside the mold. The denser the runners, the more cavities, the larger the runners, the larger the cavities, and the lower the strength of the mold, while the medullary structures are connected to each other. , not only ensures that the cooling medium can reach all areas that need to be cooled without blind spots, but also ensures the strength of the mold, which fully demonstrates the advantages of light weight and high strength of bone bionics. During the use of the pituitary cooling mold, the circulating filtered cooling medium is used to avoid pollution and clogging, and there is no need for complicated special coatings or structural changes. .

Table 1 Example parameter comparison

It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should belong to the protection scope of the appended claims of the present invention.

Claims (9)

1. The marrow-shaped cooling die is characterized by comprising a die body and a marrow-shaped structure (4) arranged in an inner cavity of the die body, wherein the die body comprises a die working surface (3), a cooling medium inlet (1) and a cooling medium outlet (2) which are arranged on the side surface of the die body, and the cooling medium inlet (1) and the cooling medium outlet (2) are respectively communicated with a cooling medium flowing marrow gap (5) in the marrow-shaped structure (4); the marrow-shaped structure (4) is formed by 3D printing;

the marrow-shaped structure (4) consists of array unit bodies, and the shape of the array unit bodies is cross-shaped, diamond-shaped, X-shaped or m-shaped and the combination of two or more of the cross-shaped, diamond-shaped, X-shaped or m-shaped; the unit bodies are mutually connected to form a marrow-shaped cooling medium flowing marrow gap, and play a role in supporting and enhancing simultaneously, the cooling medium can flow through the marrow gap to form turbulence, heat exchange is efficiently completed, heat of a working part of the die is taken away, and the surface of the working part of the die is rapidly and uniformly cooled;

the distance between the surface (3) of the working part of the die and the marrow-shaped structure (4) is 2 to 12mm.

2. A method of forming the cooling mold of claim 1, comprising the steps of:

s10: the method comprises the following steps of (1) setting a marrow-shaped structure inside a working part of a mold to be cooled by imitating a human skeleton and marrow structure, establishing a three-dimensional data model of the marrow-shaped cooling mold, and controlling the cooling speed by adjusting the distance between the surface of the working part of the mold and the marrow-shaped structure and the flow rate of a cooling medium, wherein the marrow-shaped structure consists of arrayed unit bodies which are mutually connected to form a marrow-shaped cooling medium flowing marrow gap and play roles of supporting and enhancing simultaneously, the cooling medium can flow through the marrow gap to form turbulence, so that heat exchange is efficiently completed and the heat of the working part of the mold is taken away, and the surface of the working part of the mold is rapidly and uniformly cooled;

s20: printing the three-dimensional data model by adopting a metal 3D printing technology, reserving machining allowance on the surface of a mold during printing, removing the internal stress of the mold through heat treatment after printing, and simultaneously improving the hardness of the mold;

s30: and according to the surface quality requirement of the working part of the mold, removing the allowance on the surface of the mold through machining and polishing to obtain the required pith-shaped cooling mold.

3. The forming method according to claim 2, wherein in step S10, the cooling medium includes water, oil, gas.

4. The method of forming as claimed in claim 3, wherein said cooling medium is cooling oil.

5. The forming method of claim 2, wherein in step S20, the metal 3D printing technique includes a selective laser melting technique, an electron beam melting technique, an ion beam melting technique, and a laser cladding forming technique.

6. The forming method of claim 2, wherein in step S20, the heat treatment process is established according to a mold material, the mold hardness after heat treatment reaches 50 to 60hrc, the mold material is 18Ni300 mold steel, the heat treatment method is that the mold is kept at 490 ℃ for 6 hours, and then furnace cooling is performed, and the mold hardness reaches 55HRC.

7. The forming method of claim 2, wherein the machining method of removing the allowance of the mold surface in the step S30 is CNC machining.

8. Use of the cooling mold according to claim 1 in the injection molding, casting, stamping industry.

9. Use of a method of forming a cooling mold of the pith shape according to any one of claims 2 to 7 in the injection molding, casting, stamping industry.

Images