Method and device for near-net-shape forming by micro-thermal extrusion of frozen sand molds and numerical control machining

Abstract

The application discloses a kind of frozen sand mould micro-heat extrusion and numerical control processing near net shape forming method and device, the device uses array module to build sand mould cavity preliminary profile, uses sand box lifting plate to extrude sand mould sand in sand box and form preliminary sand compact, by controlling heating suction sand device to preliminary sand compact is heated slightly to obtain preliminary sand mould, simultaneously, the floating sand generated after being heated is discharged through hollow tube, and further rough machining to the whole sand mould is completed, then the sand mould is moved to numerical control cutting machine to complete the finishing of sand mould whole.The device effectively solves the problem of floating sand accumulation generated in the process of frozen sand mould processing, avoids the long time phenomenon of sand mould numerical control processing, improves the forming precision and surface quality of frozen sand mould, lays a foundation for digital composite processing of frozen sand mould, and promotes the development of frozen sand mould processing to short process, composite and flexibility.

Description

Technical Field

[0001] This invention belongs to the field of sand mold net forming, and involves the intersection of cryogenic sand mold manufacturing, near-net-shape forming and precision forming. In particular, it relates to a composite method and apparatus for cryogenic sand mold net forming and CNC machining forming. Background Technology

[0002] Sand casting, as a common casting method, has significant implications for various industries. Widely used in metal casting, sand molds can produce castings with complex shapes and precise dimensions, meeting the needs of industries such as automotive, aerospace, and machinery. Sand casting also boasts advantages such as low cost and high production efficiency. Compared to other casting methods, sand casting requires relatively simple equipment and materials, effectively saving costs. It also has mass production capabilities, producing a large number of castings in a short time, thus improving production efficiency. It can meet the demand for castings with complex shapes, high quality, and dimensional accuracy, while maintaining low cost and high production efficiency. Through continuous innovation and technological advancements, sand casting will have even broader application prospects.

[0003] Traditional sand mold manufacturing involves mold flipping, and energy-saving and environmentally friendly frozen sand molds can also be manufactured using this method. However, the molds used in mold flipping are cumbersome and time-consuming to produce. Currently, frozen sand molds are mostly manufactured by cutting frozen sand blanks. During the cutting process, excessive cutting time can cause some sand mold surfaces to thaw due to heat, resulting in floating sand. This floating sand significantly affects the forming quality of the casting and also generates excessive waste sand. Therefore, the patent application "CN201610049689.6" proposes a method using a flexible extrusion array to adjust the shape of the sand mold, which solves the above problems to some extent. However, this method requires flipping the sand mold for forming, making clamping and positioning difficult. Furthermore, it is difficult to achieve gap-free lifting and lowering between arrays in the flexible extrusion array within the device, thus the frozen sand generated in the gaps also needs to be addressed. After flexible extrusion forming, the frozen sand mold still requires further processing, and problems such as long processing time and difficulty in handling floating sand persist. Summary of the Invention

[0004] To address the aforementioned issues, this invention discloses a method and apparatus for near-net-shape forming of a frozen sand mold using micro-thermal extrusion and CNC machining. The apparatus employs an array module to construct the preliminary contour of the sand mold cavity, uses a sand box lifting plate to extrude the molding sand in the sand box to form a preliminary sand blank, and controls a heating and sand suction device to perform micro-heating on the preliminary sand blank to obtain a preliminary sand mold. Simultaneously, the floating sand generated after heating is discharged through a hollow tube to complete further roughing of the overall sand mold. Then, the sand mold is moved to a CNC cutting machine to complete the overall finishing of the sand mold.

[0005] A method and apparatus for cryogenic sand mold micro-thermal extrusion and CNC machining near-net-shape forming is disclosed. The apparatus comprises a cryogenic sand mold near-net-shape forming machine, a cryogenic sand mold CNC machining machine, a cryogenic sand mold clamping robot arm, and an AGV intelligent transport vehicle. The cryogenic sand mold near-net-shape forming machine consists of a matrix-type sand mold heating and extrusion mechanism, a matrix array lifting mechanism, and a heating and sand suction mechanism. The sand mold extrusion mechanism comprises a sand box, a support fixing box, and a screw drive mechanism. The support fixing plate is fixed to the ball screw mechanism, and the sand box is placed inside the support fixing plate and then fixed. The matrix array lifting mechanism consists of an 8*8 lifting mechanism array. Each lifting mechanism comprises a stepper motor, a fixing plate one, a ball screw mechanism, a connecting rod, a square forming block, a fixing plate two, a heating plate, a motor platform mounting plate, and a forming table bracket. The square box is fixed to the ball screw mechanism via a connecting rod, and the fixing plate two is fixedly connected to the lower end of the ball screw. The stepper motor is connected to... The structure consists of a ball screw, a stepper motor fixed on a fixed plate, a heating plate installed in a square housing, a fixed plate fixed on a motor platform mounting plate, and a motor platform mounting plate fixed on a forming bracket and driven by module one. The heating and sand suction mechanism consists of a steering mechanism, a heating plate, a valve block, module one, module two, a sand suction pipe, and a cylinder. The heating plate is fixed on the sand suction pipe, one end of the sand suction pipe is connected to the valve block, the valve block is connected to the cylinder and rotates with the steering mechanism, the steering mechanism is fixed on module two and moves with module two, and module two is fixed on module one and moves with module one.

[0006] Furthermore, the left and right side panels of the sand box are composed of multiple layers of screens and aluminum alloy perforated plates. Fine and coarse screens are nested on the aluminum alloy perforated plates. The negative pressure interface and liquid nitrogen inlet interface are machined and connected to the outer side of the aluminum alloy plate around the support and fixing box. There is a cut-off on the inner side of the support and fixing box near the sand box. The graphite perforated heating plate surrounds the sand box and is fixed on the inner side of the support and fixing box. There is a 5mm gap between the graphite perforated plate and the sand box.

[0007] Furthermore, the spacing between the square housings of individual lifting mechanisms is 0.5mm, the height of the square housing is 25mm, and the width is 10mm;

[0008] Furthermore, the inner diameter of the sand suction tube is 6mm, the outlet is funnel-shaped, and the heating plate is made of ceramic and fixed on the sand suction tube with a diameter of 20mm.

[0009] Furthermore, one end of the gas valve is connected to an external negative pressure device, and a liquid nitrogen inlet is machined on one side of the supporting and fixing box, while a negative pressure suction port is machined on the other side.

[0010] A near-net-shape forming method using cryogenic sand mold micro-thermal extrusion and CNC machining, the method being:

[0011] Step 1: Generate a near-net-shape 3D model from the 3D model of the sand mold to be processed, and adjust the matrix array lifting mechanism to form the near-net-shape 3D model;

[0012] Step 2: Mix water and molding sand in a certain proportion and put them into the sand box. Embed the extraction mechanism and fix the sand box on the support box. The screw drive mechanism drives the sand box to squeeze upward. After the extrusion molding is completed, turn on the liquid nitrogen device and the negative pressure device to cool the preliminary sand blank.

[0013] Step 3: After the initial sand blank is formed, turn on the heating plate. After a period of time, the square forming block of the matrix array lifting mechanism will thaw and the matrix array lifting mechanism will return to the original position.

[0014] Step 4: Control module one and module two to move the sand suction pipe according to the sand mold cutting path, and the steering mechanism to adjust the rotation of the sand suction pipe. At the same time, the negative pressure device is turned on to suck up and discharge the floating sand until the overall preliminary sand mold processing is completed and the hollow heating tube is returned to the original position.

[0015] Step 5: Power on the graphite perforated heating plate. After a period of time, the outer part of the sand mold will be thawed. The frozen sand mold clamping robot arm will then pick up the frozen sand mold and place it on the AGV trolley. The AGV trolley will then transport it to the processing table of the frozen sand mold CNC machining machine. The magnetic base switch will be rotated to fix the initial sand mold. The cooling device and cutting machine of the frozen sand mold CNC machining machine will be turned on to perform cutting. After the sand mold cavity processing is completed, the sand mold will be placed in the cold storage.

[0016] Furthermore, the near-net-shape 3D model generated in reverse is matrixed to obtain the highest point of the 3D model in each matrix, which is the height of descent of a single lifting mechanism.

[0017] Furthermore, the moving speed of the heated hollow tube satisfies the following condition:

[0018] V = S / D*T

[0019] Where V: the moving speed of the heated hollow tube; D: the thawing rate at temperature T per unit time; S: the depth of the sand mold to be thawed; T: the heating temperature;

[0020] Furthermore, during the processing of heated sand suction, the distance between the sand suction and the sand mold surface should be 2mm, and the processing trajectory should be reduced by 2mm at equal intervals from the original cutting path;

[0021] Furthermore, the heating time must meet the following conditions:

[0022] T = S / V

[0023] Where T is the heating time, S is the distance of the frozen sand mold to thaw, and V is the thawing rate at temperature T, in mm / s;

[0024] Furthermore, to determine whether the filling is complete, the lifting mechanism corresponding to the highest square plane on the surface of the sand mold can be raised. If the surface is flat, the filling is complete; if the surface is uneven, it needs to be filled before lowering the lifting mechanism.

[0025] After adopting the above technical solution, the beneficial effects of the present invention are:

[0026] 1. This device effectively solves the problem of near-net-shape forming of frozen sand molds, realizes near-net-shape forming of the initial sand mold outline, saves molding sand resources, speeds up the processing time of the frozen sand mold, reduces the generation of floating sand during the freezing process, and improves the overall processing accuracy of the frozen sand mold.

[0027] 2. This device uses a hollow heating tube to further shape the frozen sand mold. This method avoids the problem of flying sand solidifying on the surface of the sand mold or accumulating in the corners of the molding sand during the cutting process, which is difficult to clean. Through precise heating and absorption, the frozen sand mold cavity is precisely shaped without waste sand accumulation or floating sand.

[0028] 3. This device and method realize the composite forming of near-net-shape forming of frozen sand molds and CNC machining. The near-net-shape forming completes the precise forming of the initial frozen sand mold without the generation of floating sand and waste sand. Then, the CNC cutting completes the further precise forming of the initial frozen sand mold. This effectively solves the problem of floating sand accumulation during the processing of frozen sand molds, reduces the CNC machining time of sand molds, and improves the forming accuracy and quality of frozen sand molds. It lays the foundation for the digital composite processing of frozen sand molds and promotes the composite development of frozen sand mold processing. Attached Figure Description

[0029] Figure 1 It is an integrated device for near-net-shape forming of cryogenic sand mold micro-thermal extrusion and CNC machining;

[0030] Figure 2 This is a front view of the overall apparatus for net-shape forming of frozen sand molds;

[0031] Figure 3 Top view of the overall apparatus for net-shape forming of frozen sand molds;

[0032] Figure 4 This refers to a single matrix array lifting mechanism within the overall frozen sand mold net forming device;

[0033] Figure 5 This is a magnified view of the heating plate area;

[0034] Figure 6 A cross-sectional view of the sand box in the cryogenic sand mold net forming integral device;

[0035] Figure 7 for Figure 6 Schematic diagram of the various components in the medium sand box;

[0036] Figure 8 This is a flowchart of the overall process for the cryogenic sand mold net forming method;

[0037] Figure 9 This is a schematic diagram of the descent height of the matrix array in the frozen sand mold net forming method;

[0038] Figure 10 This is a schematic diagram of the movement path of the sand suction pipe in the frozen sand mold net forming method;

[0039] Figure Descriptions: 1. Near-net-shape forming machine for cryogenic sand molds; 2. CNC machining machine for cryogenic sand molds; 3. AGV intelligent transport vehicle; 4. Cryogenic sand mold gripping robot arm; 101. Sand box; 102. Support and fixing box; 103. Screw transmission mechanism; 104. Motor platform mounting plate; 105. Forming table bracket; 106. Module two; 107. Overall frame; 108. Stepper motor; 109. Fixing plate one; 110. Ball screw mechanism; 111. Connecting rod; 112. Square box; 113. Fixing plate two; 114. Heating plate; 115. Module one; 116. Cylinder; 117. Valve block; 118. Sand suction pipe; 119. Combined screen; 120. Graphite perforated heating plate; 121. Steering mechanism; 122. Heating plate. Detailed Implementation

[0040] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0041] like Figure 1-6As shown, the cryogenic sand mold micro-thermal extrusion and CNC machining near-net-shape forming device includes a cryogenic sand mold near-net-shape forming machine 1, a cryogenic sand mold CNC machining machine 2, a cryogenic sand mold clamping robot arm 4, and an AGV intelligent transport vehicle 3. The cryogenic sand mold near-net-shape forming machine 1 consists of a sand mold extrusion mechanism, a matrix array lifting mechanism, and a heating and sand suction mechanism. The sand mold extrusion mechanism consists of a sand box 101, a support and fixing box 102, and a screw drive mechanism 103. The support and fixing box 102 is fixed on the screw drive mechanism 103. 01 is placed in the support and fixing box 102 and then fixed; the matrix array lifting mechanism is set on the overall frame 107; the matrix array lifting mechanism is composed of an 8*8 lifting mechanism array, and each lifting mechanism is composed of a stepper motor 108, a fixing plate 109, a ball screw mechanism 110, a connecting rod 111, a square box 112, a fixing plate 113, a heating plate 114, a motor platform mounting plate 104, and a forming table bracket 105. The ball screw mechanism 110 and the square box 112 are also mentioned. 2. A connecting rod 111 is fixed to the ball screw mechanism 110. A second fixing plate 113 is fixedly connected to the lower end of the ball screw mechanism 110. A stepper motor 108 is connected to the ball screw mechanism 110 and fixed to a first fixing plate 109. A heating plate 114 is installed in the square box 112. The first fixing plate 109 is fixed to the motor platform mounting plate 104. The motor platform mounting plate 104 is fixed to the forming bracket 105 and driven by the first module 115; heating and sand suction mechanism. It consists of a steering mechanism 121, a heating plate 122, a valve block 117, a first module 115, a second module 106, a sand suction pipe 118, and a cylinder 116. The heating plate 122 is fixed on the sand suction pipe 118. One end of the sand suction pipe 118 is connected to the valve block 117. The valve block 117 is connected to the cylinder 116 and rotates with the steering mechanism 121. The steering mechanism 121 is fixed on the second module 106 and moves with the second module. The second module 106 is fixed on the first module 115 and moves with the first module 115.

[0042] The left and right side panels of the sand box 101 are composed of multiple layers of screens and aluminum alloy perforated plates. From the outside to the inside, they are respectively arranged with a graphite perforated plate, a sand box perforated plate, a coarse screen, and a fine screen. The graphite perforated plate surrounds the sand box and is fixed inside the support box, with a 5mm gap between the graphite perforated plate and the sand box. One end of the valve block 117 is connected to an external negative pressure device. One side of the support box 102 is machined with a liquid nitrogen inlet, and the other side is machined with a negative pressure exhaust port.

[0043] The spacing between the square housings of individual lifting mechanisms is 0.5mm, the height of the square housing is 25mm, and the width is 10mm.

[0044] The inner diameter of the sand suction tube 118 is 6mm, and the outlet is funnel-shaped. The heating plate 122 is made of ceramic and is fixed on the sand suction tube 118. Its diameter is 20mm.

[0045] like Figure 8-10 As shown, a near-net-shape forming method using cryogenic sand mold micro-thermal extrusion and CNC machining is described. The method is as follows:

[0046] Step 1: Generate a near-net-shape 3D model from the 3D model of the sand mold to be processed, and adjust the matrix array lifting mechanism to form the near-net-shape 3D model;

[0047] Step 2: Mix water and molding sand in a certain proportion and put them into the sand box. Embed the extraction mechanism and fix the sand box on the support box. The screw drive mechanism drives the sand box to squeeze upward. After the extrusion molding is completed, turn on the liquid nitrogen device and the negative pressure device to cool the preliminary sand blank.

[0048] Step 3: After the initial sand blank is formed, turn on the heating plate. After a period of time, the square forming block of the matrix array lifting mechanism will thaw and the matrix array lifting mechanism will return to the original position.

[0049] Step 4: Control module one and module two to move the sand suction pipe according to the sand mold cutting path, and the steering mechanism to adjust the rotation of the sand suction pipe. At the same time, the negative pressure device is turned on to suck up and discharge the floating sand until the overall preliminary sand mold processing is completed and the hollow heating tube is returned to the original position.

[0050] Step 5: Power on the graphite perforated heating plate. After a period of time, the outer part of the sand mold will be thawed. The frozen sand mold clamping robot arm will then pick up the frozen sand mold and place it on the AGV trolley. The AGV trolley will then transport it to the processing table of the frozen sand mold CNC machining machine. The magnetic base switch will be rotated to fix the initial sand mold. The cooling device and cutting machine of the frozen sand mold CNC machining machine will be turned on to perform cutting. After the sand mold cavity processing is completed, the sand mold will be placed in the cold storage.

[0051] Among them, the near-net-shape 3D model generated in reverse is matrixed to obtain the highest point of the 3D model in each matrix, which is the height of descent of a single lifting mechanism.

[0052] The moving speed of the heated hollow tube must satisfy the following condition:

[0053] V = S / D*T

[0054] V: Moving speed of the heated hollow tube; D: Thawing rate at temperature T per unit time; S: Depth of the sand mold to be thawed; T: Heating temperature;

[0055] Among them, the heated sand absorber is 2mm away from the sand mold surface during the processing, and its processing trajectory should be reduced by 2mm at equal intervals from the original cutting path.

[0056] The heating time must meet the following conditions:

[0057] T = S / V

[0058] T is the heating time, S is the distance of the frozen sand mold to thaw, and V is the thawing rate at temperature T, in mm / s.

[0059] To determine whether the filling is complete, the lifting mechanism corresponding to the highest square plane on the surface of the sand mold can be raised. If the surface is flat, the filling is complete; if the surface is uneven, it needs to be filled before the lifting mechanism is lowered.

[0060] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A cryogenic sand mold micro-thermal extrusion and CNC machining near-net-shape forming device, comprising a cryogenic sand mold near-net-shape forming machine (1), a cryogenic sand mold CNC machining machine (2), a cryogenic sand mold clamping robot arm (4), and an AGV intelligent transport vehicle (3); characterized in that: The near-net-shape forming machine for frozen sand molds (1) consists of a sand mold extrusion mechanism, a matrix array lifting mechanism, and a heating and sand suction mechanism; the sand mold extrusion mechanism consists of a sand box (101), a support fixing box (102), and a screw transmission mechanism (103). The support fixing box (102) is fixed on the screw transmission mechanism (103), and the sand box (101) is placed in the support fixing box (102) and then fixed; the matrix array lifting mechanism is set on the overall frame (107); the matrix array lifting mechanism consists of an 8*8 lifting mechanism array; a single lifting mechanism consists of a stepper motor (108), a fixing plate (109), a ball screw mechanism (110), a connecting rod (111), and a square The device consists of a square housing (112), a second fixing plate (113), a heating plate (114), a motor platform mounting plate (104), and a forming table bracket (105). A ball screw mechanism (110) is also present. The square housing (112) is fixed to the ball screw mechanism (110) via a connecting rod (111). The second fixing plate (113) is fixedly connected to the lower end of the ball screw mechanism (110). A stepper motor (108) is connected to the ball screw mechanism (110) and fixed to the first fixing plate (109). The heating plate (114) is installed inside the square housing (112), and the first fixing plate (109) is fixed to the motor platform mounting plate (104). The motor platform mounting plate (104) is fixed on the forming table bracket (105) and driven by module one (115); the heating and sand suction mechanism consists of a steering mechanism (121), a heating plate (122), a valve block (117), module one (115), module two (106), a sand suction pipe (118), and a cylinder (116). The heating plate (122) is fixed on the sand suction pipe (118), one end of the sand suction pipe (118) is connected to the valve block (117), the valve block (117) is connected to the cylinder (116) and rotates with the steering mechanism (121). The steering mechanism (121) is fixed on module two (106) and moves with module two. Module two (106) is fixed. The sand box (101) is fixed on module 1 (115) and moves with module 1 (115); the left and right side plates of the sand box (101) are composed of multiple layers of screens and aluminum alloy perforated plates, and graphite perforated plates, sand box perforated plates, coarse screens and fine screens are set from the outside to the inside respectively; the graphite perforated plates surround the sand box and are fixed inside the support and fixing box, and there is a 5mm gap between the graphite perforated plates and the sand box; the square shell spacing between individual lifting mechanisms is 0.5mm, the square box height is 25mm and the width is 10mm; the inner diameter of the sand suction pipe (118) is 6mm, the outlet is trumpet-shaped, the heating plate (122) is made of ceramic and fixed on the sand suction pipe (118), and its diameter is 20mm.

2. The cryogenic sand mold micro-thermal extrusion and CNC machining near-net-shape forming device according to claim 1, characterized in that: One end of the valve block (117) is connected to an external negative pressure device. The support and fixing box (102) has a liquid nitrogen inlet on one side and a negative pressure exhaust port on the other side.

3. A method for near-net-shape forming of cryogenic sand mold micro-thermal extrusion and CNC machining, implemented based on the cryogenic sand mold micro-thermal extrusion and CNC machining near-net-shape forming apparatus according to any one of claims 1-2, characterized in that: The method is as follows: Step 1: Generate a near-net-shape 3D model from the 3D model of the sand mold to be processed, and adjust the matrix array lifting mechanism to form the near-net-shape 3D model; Step 2: Mix water and molding sand in a certain proportion and put them into the sand box. Embed the extraction mechanism and fix the sand box on the support box. The screw drive mechanism drives the sand box to squeeze upward. After the extrusion molding is completed, turn on the liquid nitrogen device and the negative pressure device to cool the preliminary sand blank. Step 3: After the initial sand blank is formed, turn on the heating plate. After a period of time, the square forming block of the matrix array lifting mechanism will thaw and the matrix array lifting mechanism will return to the original position. Step 4: Control module one and module two to move the sand suction pipe according to the sand mold cutting path, the steering mechanism to adjust the rotation of the sand suction pipe, and at the same time turn on the negative pressure device to suck up and discharge the floating sand until the overall preliminary sand mold processing is completed and the hollow heating tube is returned to the original position. Step 5: Power on the graphite perforated heating plate. After a period of time, the outer part of the sand mold will thaw. The frozen sand mold clamping robot arm will then pick up the frozen sand mold and place it on the AGV trolley. The AGV trolley will then transport it to the processing table of the frozen sand mold CNC machining machine. The magnetic base switch will be rotated to fix the initial sand mold. The cooling device and cutting machine of the frozen sand mold CNC machining machine will be turned on to perform cutting. After the sand mold cavity processing is completed, the sand mold will be placed in the cold storage.

4. The method for near-net-shape forming of cryogenic sand mold micro-thermal extrusion and CNC machining according to claim 3, characterized in that: The near-net-shape 3D model generated in reverse is matrixed to obtain the highest point of the 3D model in each matrix, which is the height of descent of a single lifting mechanism.

5. The method for near-net-shape forming of cryogenic sand mold micro-thermal extrusion and CNC machining according to claim 3, characterized in that: The moving speed of the heated hollow tube must satisfy the following condition: V = S / D*T; Where V: the moving speed of the heated hollow tube; D: the thawing rate at temperature T per unit time; S: the depth of the sand mold to be thawed; T: the heating temperature; the heating time must meet the following conditions: T = S / V; Where T is the heating time, S is the distance of the frozen sand mold to thaw, and V is the thawing rate at temperature T, in mm / s.

6. The method for near-net-shape forming of cryogenic sand mold micro-thermal extrusion and CNC machining according to claim 3, characterized in that: During the processing, the heated sand suction should be 2mm away from the surface of the sand mold, and its processing trajectory should be reduced by 2mm at equal intervals from the original cutting path.

7. The method for near-net-shape forming of cryogenic sand mold micro-thermal extrusion and CNC machining according to claim 3, characterized in that: When determining whether the filling is complete, the lifting mechanism corresponding to the highest square plane on the surface of the rising sand mold will be used. If the surface is flat, the filling is complete; if the surface is uneven, it needs to be filled before the lifting mechanism is lowered.

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