Frozen sand mold additive manufacturing short-cycle forming method and apparatus

Abstract

The present application relates to the field of frozen sand mold green casting technology, and proposes a frozen sand mold additive manufacturing short process forming method and device, mainly comprising a sand laying box, a vortex refrigerator, a printing device, a supporting plate, a recycling box, a rack, a motor, a switch plate, a flow baffle, a filter screen, a turbine fan, a control plate, a partition plate and a guide rail mechanism. The device and method use sand laying, printing and rapid balanced refrigeration device to make the frozen sand mold, and the vortex refrigerator realizes rapid refrigeration and forming of the thin layer of the sand printing surface by using the heat conduction principle. At the same time, the turbine fan is used to transport low-temperature gas to the forming chamber on both sides, and the balanced refrigeration of the core and the surface of the forming chamber is realized by using the principle of heat convection, thereby realizing the rapid manufacturing and preservation of the complex frozen sand mold. The automatic switch plate is arranged below the forming chamber on both sides, and the rapid sand cleaning of the printing area is realized by using the gravity and fluidity of the sand mold. The frozen sand mold with the size precision requirement is obtained, and the frozen sand mold preparation process is shortened.

Description

TECHNICAL FIELD

[0001] The present application relates to the molding process of sand mold in the field of casting technology, and particularly relates to a quick balanced refrigeration and short process sand cleaning method and device for frozen sand mold additive manufacturing. BACKGROUND

[0002] As a green casting process, frozen casting has high sand reuse rate and no pollution in the casting process, and the obtained castings have excellent organization and performance, so it is a green manufacturing technology with good development potential. The production process of frozen casting mainly includes three processes of molding, freezing and pouring, and the precision of the first two processes determines the forming effect of the poured castings. At present, the mold manufacturing of frozen casting mainly adopts the method of manual sanding molding, that is, the mold is obtained by manually sanding the mold sand mixed with a certain proportion of water and the mold, which is mainly used for manufacturing simple-shaped molds. For complex-shaped molds, on the one hand, the mold manufacturing period is long and the production cost is high, and on the other hand, it is difficult to freeze the mold, and the size precision of the frozen sand mold is low.

[0003] The freezing method of frozen sand mold usually adopts the method of liquid nitrogen refrigeration or refrigerator refrigeration, and the sand mold is frozen and molded by using the principle of heat conduction. The freezing and solidification of the sand mold are gradually realized by heat exchange between the low-temperature environment of the liquid nitrogen or refrigerator and the sand mold interface. Due to the slow heat transfer refrigeration speed, the sand mold freezing and solidification requires a long time, especially the long-time drying refrigeration energy consumption is huge, and the sustainability is not strong. At the same time, the sand mold surface is easy to lose water, which causes the low precision of the sand mold surface, seriously affects the quality of the sand mold, and hinders the engineering application of the frozen sand mold.

[0004] The commonly used sand mold printing needs to be placed for a period of time after printing is completed, and then the mold is manually taken out after the strength of the printed part meets the requirements. Then, the remaining sand in the forming chamber and the mold is cleaned. The sand cleaning process is generally cleaned by manual cleaning, which is time-consuming and laborious, has slow response speed, low refrigeration efficiency, and the real-time sand removal problem of the sand mold printing also needs to be improved to prevent the sand mold surface from sticking to the sand caused by the frozen temperature transmission. SUMMARY

[0005] To solve the above problems, the present application discloses a short process forming method and device for frozen sand mold additive manufacturing, which mainly solves the problems of long process flow, large energy consumption, low size precision and difficult sand removal of the frozen sand mold molding process.

[0006] The short-process forming device for frozen sand mold additive manufacturing in the application comprises a sand laying box, a vortex refrigerator, a printing device, a supporting plate, a recycling box, a rack, a motor, a switch plate, a flow baffle, a filter screen, a fan, a control plate, a partition plate and a guide rail mechanism, and is characterized in that: the motor is installed upside down on the rack and connected with a threaded screw rod in the center of the rack through a belt to control the up-and-down movement of the supporting plate; the sand laying box, the vortex refrigerator and the printing device are placed side by side above the device to realize the refrigeration and sand covering (condensation prevention) process in the frozen sand mold additive manufacturing process.

[0007] The guide rail mechanism is evenly placed on both sides of the device to ensure the reciprocating movement of the sand laying box, the vortex refrigerator and the printing device; the partition plate connects the two guide rail mechanisms to ensure the stability of the whole device; the flow baffle, the filter screen, the control plate and the supporting plate constitute the forming chamber of the frozen sand mold to lay and freeze the molding sand; the recycling box is located on one side of the forming chamber to recycle the excess molding sand laid in the printing process of the forming chamber; and the switch plate is located below the forming chamber to realize the real-time and rapid cleaning of the excess sand outside the frozen sand mold in the freezing chamber.

[0008] As a further design of the scheme, the flow baffle, the filter screen, the control plate and the supporting plate are in sealed connection to ensure the temperature balance in the forming chamber.

[0009] As a further design of the scheme, fans are installed on the front, back and sides of the forming chamber and connected with an external circulating refrigeration pump to provide a low-temperature environment for the forming chamber.

[0010] As a further design of the scheme, three surfaces of the filter screen in contact with the fan are provided with uniformly distributed coarse mesh holes (the diameter of the coarse mesh hole is about 60μm-120μm) to ensure that the cold air is uniformly delivered to the forming chamber, and the center part of the coarse mesh hole is provided with a layer of fixed superfine screen (the diameter of the fine screen is about 20μm-80μm) to prevent the molding sand in the forming chamber from leaking out.

[0011] As a further design of the scheme, the switch plates are symmetrically installed on the front and back of the device to realize the real-time and rapid cleaning of the excess sand below the forming area.

[0012] The application also provides a short-process forming method for frozen sand mold additive manufacturing, which comprises the following steps:

[0013] S1: according to the type of the casting, appropriate molding sand and printing gray scale are selected, the casting geometric model is subjected to layer-by-layer slicing treatment, and two-dimensional slicing information of each layer is determined;

[0014] S2: the molding sand is placed in the sand laying box, the bottom sand is laid on the supporting plate, and then single-layer sand laying is performed according to the sand laying thickness of each layer set by the computer, the initial movement direction is the recycling box to the partition plate direction, and the return direction is the partition plate to the recycling box direction.

[0015] S3: after the unidirectional sand laying is completed, the printing device, the vortex refrigerating device and the liquid nitrogen circulating tank are started in the return direction movement to perform printing forming and refrigeration, and the next layer of sand covering the printing layer is laid;

[0016] S4: after the printing of one layer is completed, the support plate is moved downward by a layer thickness according to the layer thickness information set by the computer, and the printing device returns to the starting position on the side of the partition plate to continue the printing and sand covering operation;

[0017] S5: the liquid nitrogen circulating tank and the vortex refrigerating device are kept in the open state during the printing until the printing is completed;

[0018] S6: after the printing is completed, the support plate is lowered to the switch plate area, and the two side switch plates are opened, and the residual sand in the unformed area flows out under the action of gravity, and after the residual sand in the lower part is cleaned, the support plate is raised to clean the residual sand in the upper part of the frozen sand mold;

[0019] S7: the frozen sand mold is taken out and transported to the sand mold storage room, and the workbench is cleaned.

[0020] As a further design of the scheme, the sand laying box covers sand during the printing to prevent the printing layer from being affected by heat and water vapor in the air.

[0021] As a further design of the scheme, the frozen sand mold additive manufacturing short process forming device can realize the refrigeration effect of superimposed heat conduction and heat convection, which is beneficial to the rapid freezing forming and machining of complex frozen sand molds.

[0022] As a further design of the scheme, the switch plate can realize real-time and rapid cleaning of the residual sand, and shorten the frozen sand mold manufacturing process.

[0023] The beneficial effects of the present application are:

[0024] 1. Compared with the long process flow, large energy consumption and low molding size precision of the traditional frozen sand mold hand modeling, the device can realize automatic modeling, save labor cost, and has high sand mold forming size precision, thereby saving the use amount of raw materials and the machining allowance of the casting product.

[0025] 2. The device solves the low-temperature forming problem in the frozen sand mold additive manufacturing molding process using water as a binder, and realizes rapid and balanced refrigeration of the forming area by using the heat transfer and convection superimposed refrigeration principle of the vortex refrigerating device and the circulating cold air fan, thereby increasing the refrigeration efficiency, and compared with the frozen sand cutting modeling, the device provides more possibilities for the manufacturing of complex structure frozen sand molds.

[0026] 3, The device can realize short process real-time sand cleaning process after printing, shorten the sand molding process, save the sand molding post-processing time, and save the energy consumption. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Structure diagram of the short process forming device for frozen sand type additive manufacturing;

[0028] Figure 2 Structure diagram of the filter screen;

[0029] Figure 3 Structure diagram of the forming chamber part;

[0030] Figure 4 Structure diagram of the fan;

[0031] Figure 5 Structure diagram of the switch board;

[0032] LIST OF REFERENCE NUMERALS

[0033] Wherein 1 is a sand laying box, 2 is a vortex refrigerator, 3 is a printing device, 4 is a supporting plate, 5 is a recycling box, 6 is a rack, 7 is a motor, 8 is a switch board, 9 is a liquid nitrogen flow barrier, 10 is a guide rail mechanism, 11 is a partition plate, 12 is a control plate, 13 is a filter screen, and 14 is a fan. EMBODIMENT

[0034] The present application will be further illustrated in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present application and are not used to limit the scope of the present application. It should be noted that the words "front", "back", "left", "right", "up" and "down" used in the following description refer to the directions in the drawings, and the words "in" and "out" refer to the directions towards or away from the geometric center of a particular component.

[0035] As shown in Figures 1-2 The present application provides a frozen sand type additive manufacturing gradient refrigeration and short process sand cleaning device, which comprises a sand laying box, a vortex refrigerator, a printing device, a supporting plate, a recycling box, a rack, a motor, a switch board, a liquid nitrogen flow barrier, a filter screen, a control plate, a partition plate and a guide rail mechanism. The motor is installed upside down on the rack and connected to the threaded lead screw at the center of the rack through a belt to control the up and down movement of the supporting plate.

[0036] The sand laying box, the vortex refrigerator and the printing device are placed side by side above the device to realize the refrigeration and sand covering (preventing condensation) process during the frozen sand type additive manufacturing process; the guide rail mechanisms are evenly placed on both sides of the device to ensure the reciprocating movement of the sand laying box, the vortex refrigerator and the printing device.

[0037] The baffle, filter screen, control plate and supporting plate constitute a forming chamber of the frozen sand mold, which is used for laying and freezing forming of the molding sand; the recovery box is located on one side of the forming chamber and is used for recovering the molding sand laid in excess during the printing process of the forming chamber; and the switch plate is located below the forming chamber and can realize real-time and rapid cleaning of the excess molding sand outside the frozen sand mold in the freezing chamber.

[0038] The baffle, filter screen, control plate and supporting plate are in sealed connection, so as to ensure temperature balance in the forming chamber; fans are installed on the front, rear and side surfaces of the forming chamber and are connected with an external circulating refrigeration pump to provide a low-temperature environment for the forming chamber; the three surfaces of the filter screen in contact with the fans are provided with uniformly distributed coarse mesh holes, so as to ensure uniform delivery of cold air to the forming chamber; and the center part of the coarse mesh holes is provided with a layer of fixed superfine screen, which is used to prevent the molding sand in the forming chamber from leaking out; and the switch plates are symmetrically installed on the front and rear sides of the device and are used to realize real-time and rapid cleaning of the excess molding sand below the forming area.

[0039] In addition, the embodiment also provides a frozen sand mold additive manufacturing short-process forming method, which comprises the following steps:

[0040] S1: selecting appropriate molding sand and printing gray scale according to the type of the casting, performing layer-by-layer slicing processing on a casting geometric model, determining two-dimensional slicing information of each layer, and setting the thickness of each layer of the molding sand to be 0.2-0.8 mm;

[0041] S2: placing the molding sand into a sand laying box, laying 1-5 cm of bottom sand on the supporting plate, and then laying single-layer sand according to the thickness of each layer of the molding sand set by the computer, wherein the initial movement direction is from the recovery box to the partition plate, and the return direction is from the partition plate to the recovery box;

[0042] S3: after the single-direction sand laying is completed, the printing device, the vortex refrigeration device and the fan are started in the return direction, printing forming and refrigeration are performed, the printing device sprays water-based adhesive, the vortex refrigeration device is kept at-5℃ to-30℃, and the next layer of the molding sand is laid to cover the printing layer;

[0043] S4: after the printing of one layer is completed, the supporting plate moves downward by a layer thickness according to the layer thickness information set by the computer, and the printing device returns to the starting position on the side of the partition plate to continue the printing and sand laying operation;

[0044] S5: the fan and the vortex refrigeration device are kept in the opened state during the printing process until the printing is completed;

[0045] S6: after the printing is completed, the supporting plate is lowered to the switch plate area, the two switch plates are opened, the excess molding sand in the unformed area flows out under the action of gravity, after the cleaning of the excess molding sand in the lower part is completed, the supporting plate is raised to clean the excess molding sand in the upper part of the frozen sand mold;

[0046] S7: the frozen sand mold is taken out and transported to a sand mold storage chamber, and the workbench is cleaned.

[0047] The technical means disclosed in the technical scheme of the present application is not limited to the technical means disclosed in the above-mentioned embodiments, but also includes technical schemes composed of any combination of the above technical features.

Claims

1. A cryogenic sand-mold additive manufacturing short-process forming device, comprising a sand-laying box (1), a vortex cooler (2), a cryogenic printing device (3), a tray (4), a recycling bin (5), a frame (6), a motor (7), a switch plate (8), a baffle plate (9), a filter screen (13), a turbine fan (14), a control plate (12), a partition plate (11), and a guide rail mechanism (10), characterized in that: An inverted motor (7) is installed on the frame (6), which is connected to the threaded screw at the center of the frame (6) via a belt to control the up and down movement of the tray (4); a sand-laying box (1), a vortex cooler (2), and a printing device (3) are placed side by side above the device, and the guide rail mechanism (10) is placed symmetrically on both sides of the device, wherein the bottoms of the sand-laying box (1), the vortex cooler (2), and the printing device (3) are all connected to the guide rail mechanism (10); wherein the baffle plate (9), the filter screen (13), the control plate (12), and the tray (4) constitute the forming chamber of the frozen sand mold, wherein the baffle plate (9) 9) It is sealed and connected to the control plate (12) at the top and bottom. The filter screen (13) is inside the baffle plate (9). The recycling box (5) is on one side of the forming chamber and is used to recycle the excess molding sand laid during the printing process of the forming chamber. The switch plate (8) is located below the forming chamber. The three sides of the filter screen (13) that are in contact with the turbine fan have uniformly distributed coarse mesh holes with a diameter of 60μm~120μm to ensure that the cold air is uniformly delivered to the forming chamber. The center of the coarse mesh hole is a layer of fixed ultrafine screen with a diameter of 20μm~80μm to ensure that the molding sand in the forming chamber cools down quickly and does not leak out.

2. The cryogenic sand mold additive manufacturing short-process forming apparatus according to claim 1, characterized in that: The partition (11) connects two guide rail mechanisms to ensure the stability of the overall device.

3. The cryogenic sand mold additive manufacturing short-process forming apparatus according to claim 1, characterized in that: The baffle (9), filter screen (13), control plate (12), and support plate (4) are sealed to ensure temperature balance in the forming chamber and coordinated control of rapid cooling and long-term heat preservation.

4. The cryogenic sand mold additive manufacturing short-process forming apparatus according to claim 1, characterized in that: Turbine fans (14) are installed at the front, rear and sides of the molding chamber and connected to an external circulating refrigeration pump to provide a low temperature environment for the molding chamber.

5. The cryogenic sand mold additive manufacturing short-process forming apparatus according to claim 1, characterized in that: The switch plate (8) is symmetrically installed on the front and rear sides of the device.

6. The cryogenic sand mold additive manufacturing short-process forming method of the cryogenic sand mold additive manufacturing short-process forming apparatus according to any one of claims 1-5, characterized in that, The method includes the following steps: S1: Select appropriate molding sand and printing grayscale according to the casting type, perform layered slicing of the casting geometric model, and determine the two-dimensional slicing information of each layer; S2: Place the molding sand into the sand-laying box (1), lay the bottom sand on the tray (4), and then lay a single layer of sand according to the thickness of each layer of sand set by the computer. The initial movement direction is: from the recycling box (5) to the partition (11), and the return direction is from the partition (11) to the recycling box (5). S3: After the sand is laid in one direction, the printing device (3), the vortex cooler (2) and the fan (14) are turned on when moving in the return direction to print and cool, while laying the next layer of molding sand to cover the printing layer. S4: After printing one layer, the tray (4) moves down one layer thickness according to the layer thickness information set by the computer, and at the same time the printing device returns to the starting position on one side of the partition (11) to continue printing and covering sand operation. S5: During the printing process, the turbine fan (14) and the scroll cooler (2) remain on until printing is complete; S6: After printing is completed, the tray (4) automatically descends to the switch plate area and opens the switch plates (8) on both sides. The residual sand in the unformed area will flow out under the action of gravity. After the residual sand in the lower part is cleaned, the tray (4) rises to clean the residual sand in the upper part of the frozen sand mold, realizing real-time sand cleaning in a short process. S7: Remove the frozen sand mold and transport it to the sand mold storage room. Clean the printing workbench and complete the printing process.

7. The short-process forming method for cryogenic sand mold additive manufacturing according to claim 6, characterized in that, The sand-covering box (1) is covered with sand during the printing process.

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