A deformation-resistant engineering plastic filler skeleton structure and its application

Abstract

The purpose of the present invention is to provide an anti-deformation engineering plastic filler skeleton structure and its application, which belongs to the technical field of investment casting manufacturing. The filler skeleton structure is evenly distributed with hole structures to facilitate wax filling, and at the same time, completely identical positioning protrusions are evenly distributed on both sides to ensure that the filler skeleton structure is located in the middle of the wax mold. When the wax mold is made, an engineering plastic skeleton is added to the mold to press wax to wrap the skeleton. Because engineering plastics have good mechanical strength, dimensional stability and rigidity, this type of wax part will not produce permanent plastic deformation during the subsequent trimming, assembly, placement and shell making process, resulting in serious deviations in the casting surface contour. This not only effectively reduces the complexity of the product wax mold structure design, but also avoids a large amount of subsequent processing of the casting, reduces the processing cost of the product, and significantly shortens the production cycle.

Description

Technical Field

[0001] The invention belongs to the technical field of investment casting manufacturing, and in particular provides a deformation-proof engineering plastic filler skeleton structure and application thereof. Background Art

[0002] With the rapid development of my country's aerospace and weapon equipment industries, the demand for aluminum alloy castings is increasing, and the requirements for casting dimensional accuracy, surface quality and internal metallurgical quality are also increasing. They are gradually developing in the direction of large, thin-walled, complex and integrated. For castings with thin-walled curved surfaces that have contour requirements, especially runner surfaces, wax parts generally used for investment casting are prone to distortion, collapse and other deformations that affect the contour, causing the final casting runner surface to be severely deformed, resulting in unqualified castings. The current process measures are to prevent deformation by increasing compensation or adding process ribs.

[0003] Adding compensation or process ribs to prevent deformation will increase the difficulty of casting structure design and reduce the casting yield. It will also cause difficulties in subsequent cleaning and processing, which will not only increase financial expenditures but also extend the production cycle of castings. Summary of the invention

[0004] In order to overcome the problems existing in the prior art, the purpose of the present invention is to provide an anti-deformation engineering plastic filler skeleton structure and its application.

[0005] The technical solution of the present invention is as follows:

[0006] A deformation-resistant engineering plastic filler skeleton structure, characterized in that: the filler skeleton structure is evenly distributed with hole structures to facilitate wax filling, and at the same time, completely identical positioning protrusions are evenly distributed on both sides to ensure that the filler skeleton structure is located in the middle of the wax mold.

[0007] As the preferred technical solution:

[0008] The diameter of the hole structure is 3 to 7 mm, and the interval between two adjacent hole structures is 30 to 50 mm; the wall thickness of the filler skeleton structure is between 1 and 3 mm, and the specific thickness of different parts depends on the thickness of the casting at that location, so as to ensure that the thickness of the wax model on both sides of each location is consistent, and arc transition is used at corners and thick-thin joints.

[0009] The filler skeleton structure is made of engineering plastics. The present invention preferably uses high-rigidity engineering plastics with a Rockwell hardness of ≥115 and a static bending strength of ≥100 MPa. The high-rigidity engineering plastics contain 15 to 25 parts by weight of ABS resin, 75 to 85 parts by weight of SAN copolymer and 0.8 to 1.5 parts by weight of additives, wherein the sum of the added amounts of ABS resin and SAN copolymer must be 100 parts by weight, the additive is a lubricant, and the ABS resin is an emulsion grafting-bulk SAN blending method ABS resin.

[0010] in:

[0011] Every 100 parts by weight of ABS resin contains 14 to 20 parts by weight of ABS grafted powder and 80 to 86 parts by weight of SAN copolymer, wherein the average rubber particle size of the ABS grafted powder is 0.2 to 0.5 μm; the ABS grafted powder is a grafted polymer formed by emulsion polymerization of 50 to 55 wt % of rubber particles formed by polybutadiene rubber and 45 to 50 wt % of SAN copolymer; and the melt index of the ABS resin at a test temperature of 220° C. and a load of 10 kg is 3 to 8 g / 10 minutes.

[0012] Every 100 parts by weight of the SAN copolymer contains 15 to 25 parts by weight of acrylonitrile and 75 to 85 parts of styrene, and the average molecular weight of the SAN resin is 180,000-300,000;

[0013] The lubricant is one or more of vinyl distearate amide and stearate, and the stearate is one or more of magnesium stearate, calcium stearate, zinc stearate and barium stearate.

[0014] The high-rigidity engineering plastic can be obtained by melt-blending and extruding ABS resin, SAN copolymer and lubricant.

[0015] The present invention also provides a method for making a wax mold of an aluminum alloy precision casting with the anti-deformation engineering plastic filler skeleton structure, which is characterized by comprising the following steps:

[0016] 1) According to the structural characteristics of the casting, the anti-deformation engineering plastic filler skeleton structure is designed using 3D modeling software;

[0017] 2) Design and manufacture molds for anti-deformation engineering plastic filler skeleton structures;

[0018] 3) Drying of engineering plastics and preheating of molds;

[0019] 4) Injecting engineering plastics into the mold;

[0020] 5) After the engineering plastic cools and hardens, take the mold;

[0021] 6) Clean the positioning convex points on both sides of the skeleton structure of the engineering plastic filler to ensure that the tops of all positioning convex points are smooth and free of foreign matter;

[0022] 7) heating the engineering plastic filler skeleton structure to remove internal stress, specifically including: placing the engineering plastic filler skeleton structure in a hot air circulation drying oven at 70 to 80° C. for 2 to 4 hours, and then cooling it to room temperature;

[0023] 8) Place the stress-relieved engineering plastic filler skeleton structure into the product wax mold;

[0024] 9) Make wax models on a wax press.

[0025] in:

[0026] In step 2), the mold of the anti-deformation engineering plastic filler skeleton structure is made of stainless steel material through mechanical processing.

[0027] In step 3), before injection molding, the engineering plastic needs to be dried at a temperature of 70 to 85° C. for 2 to 6 hours; the mold needs to be preheated to 50 to 100° C. before injection molding.

[0028] In step 4), the injection temperature of the engineering plastic is 240-265°C.

[0029] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0030] When making the wax model, an engineering plastic skeleton is added to the mold and wax is pressed to wrap the skeleton. Because engineering plastics have good mechanical strength, dimensional stability and rigidity, this type of wax part will not produce permanent plastic deformation during the subsequent trimming, assembly, placement and shell making process, which will lead to serious deviations in the casting surface contour. This not only effectively reduces the complexity of the product wax mold structure design, but also avoids a large amount of subsequent processing of the casting, reduces the processing cost of the product, and significantly shortens the production cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the skeleton structure of anti-deformation engineering plastic filler.

[0032] Figure numerals: 1- filler skeleton structure; 2- hole structure; 3- positioning protrusion. DETAILED DESCRIPTION

[0033] Example 1

[0034] like Figure 1As shown, an anti-deformation engineering plastic filler skeleton structure 1 has hole structures 2 with a diameter of 5 mm evenly distributed thereon, the interval between two adjacent hole structures 2 is 30-50 mm, and completely identical positioning protrusions 3 are evenly distributed on both sides. The wall thickness of the filler skeleton structure 1 is between 1 and 2 mm, and the specific thickness of different parts depends on the thickness of the casting at that place to ensure that the thickness of the wax mold on both sides of each part is consistent, and arc transitions are used at corners and thick-thin joints.

[0035] The filler skeleton structure 1 is made of high-rigidity engineering plastic, including 15 parts by weight of ABS resin (acrylonitrile-butadiene-styrene), 85 parts by weight of SAN copolymer (styrene-acrylonitrile) and 1.5 parts by weight of additives. The ABS resin is an emulsion grafted-bulk SAN blended ABS resin, and the melt index of the ABS resin at a test temperature of 220° C. and a load of 10 kg is 8 g / 10 minutes.

[0036] Relative to 100 parts by weight of ABS resin, it contains 20 parts by weight of ABS graft powder (ABS graft powder is a graft polymer formed by emulsion polymerization of 52% rubber particles formed by polybutadiene rubber and 48wt% SAN copolymer, and the average rubber particle size is 0.4μm) and 80 parts by weight of SAN copolymer.

[0037] The SAN copolymer contains 15 parts by weight of acrylonitrile and 85 parts by weight of styrene relative to 100 parts by weight of the SAN copolymer. The average molecular weight of the SAN copolymer is 290,000.

[0038] The auxiliary agent is magnesium stearate which has both internal and external lubrication.

[0039] The ABS resin, the SAN copolymer and the lubricant are melt-blended and extruded to obtain the high-rigidity engineering plastic having a Rockwell hardness of 121 and a static bending strength of 108 MPa.

[0040] Example 2

[0041] The difference from Example 1 is that the engineering plastic components and their proportions are different, as follows:

[0042] A high-rigidity engineering plastic comprises 20 parts by weight of ABS resin (acrylonitrile-butadiene-styrene), 80 parts by weight of SAN copolymer (styrene-acrylonitrile) and 1.3 parts by weight of an additive, wherein the ABS resin is an ABS resin obtained by an emulsion grafting-bulk SAN blending method, and the melt index of the ABS resin is 8 g / 10 minutes at a test temperature of 220° C. and a load of 10 kg.

[0043] Relative to 100 parts by weight of ABS resin, it contains 16 parts by weight of ABS graft powder (ABS graft powder is a graft polymer formed by emulsion polymerization of 50% rubber particles formed by polybutadiene rubber and 50wt% SAN copolymer, and the average rubber particle size is 0.3μm) and 84 parts by weight of SAN copolymer.

[0044] The SAN copolymer contains 19 parts by weight of acrylonitrile and 81 parts by weight of styrene relative to 100 parts by weight of the SAN copolymer. The average molecular weight of the SAN copolymer is 280,000.

[0045] The auxiliary agent comprises 1.1 parts by weight of EBA internal lubricant and 0.2 parts by weight of magnesium stearate having both internal and external lubrication.

[0046] The ABS resin, the SAN copolymer and the lubricant are melt-blended and extruded to obtain the high-rigidity engineering plastic having a Rockwell hardness of 120 and a static bending strength of 105 MPa.

[0047] Example 3

[0048] Take a certain type of aluminum alloy frame casting as an example, the material is ZL101A, the outline size is 670mm×500mm×210mm, the typical wall thickness is 4mm, the casting is Class I, and the dimensional accuracy is CT7. The specific steps of its implementation are as follows:

[0049] Step 1): The casting has a large thin-walled plane. The anti-deformation engineering plastic filler skeleton structure is designed using UG 3D modeling software according to the plane size and structure. The wall thickness of the engineering plastic filler skeleton structure is 2mm, and there are evenly distributed hole structures with a diameter of 5mm. The interval between two adjacent hole structures is 35mm, and there are 6 identical positioning protrusions on both sides.

[0050] Step 2): According to the anti-deformation engineering plastic filler skeleton structure designed in step 1), a mold of the anti-deformation engineering plastic filler skeleton structure is designed by using the Boolean operation tool of UG 3D modeling software, and then a stainless steel mold is processed by mechanical processing.

[0051] Step 3): The engineering plastics described in Example 1 are placed in a circulating hot air drying oven at a temperature of 75° C. for drying for 3 hours, and the stainless steel mold is preheated to 70° C. at the same time.

[0052] Step 4): Heat and melt the engineering plastic, and when the temperature reaches 250°C, inject it into the preheated stainless steel mold.

[0053] Step 5): After the engineering plastic cools and hardens, remove it from the stainless steel mold.

[0054] Step 6): Clean the positioning protrusions on both sides of the engineering plastic filler skeleton structure taken out in step 5) to ensure that the tops of all positioning protrusions are smooth and free of foreign matter.

[0055] Step 7): Place the cleaned engineering plastic filler skeleton structure in a hot air circulation drying oven at 70° C. for 2 hours to remove internal stress, and cool to room temperature.

[0056] Step 8): Place the stressed engineering plastic filler skeleton structure into the product wax mold, make the wax mold on a wax press, and take out the mold after the wax mold cools down.

[0057] The wax model with a skeleton structure of anti-deformation engineering plastic filler was inspected for size. The wax model did not deform significantly at this plane, which met the casting requirements. Compared with adding process ribs at this thin-walled plane, it saved about 5,000 yuan in costs and shortened the processing cycle by 5 days. The casting was inspected for size, and the dimensional accuracy reached CT7.

[0058] Example 4

[0059] Take a certain type of aluminum alloy rear cabin casting as an example. The material is ZL114A. There is a large air intake curved surface structure. The typical wall thickness is 4mm. The casting is Class I and the dimensional accuracy is CT7. The specific steps of its implementation are as follows:

[0060] Step 1): The casting has a large air inlet curved surface structure, and the wax part is very easy to deform. According to the surface size and structure, the anti-deformation engineering plastic filler skeleton structure is designed using UG 3D modeling software. The wall thickness of the engineering plastic filler skeleton structure is 1.5mm, and there are evenly distributed hole structures with a diameter of 5mm. The interval between two adjacent hole structures is 45mm, and there are 10 identical positioning bumps on both sides.

[0061] Step 2): According to the anti-deformation engineering plastic filler skeleton structure designed in step 1), a mold of the anti-deformation engineering plastic filler skeleton structure is designed by using the Boolean operation tool of UG 3D modeling software, and then a stainless steel mold is processed by mechanical processing.

[0062] Step 3): The engineering plastics described in Example 2 are placed in a circulating hot air drying oven at a temperature of 70° C. for drying for 4 hours, and the stainless steel mold is preheated to 85° C. at the same time.

[0063] Step 4): Heat and melt the engineering plastic, and when the temperature reaches 265°C, inject it into the preheated stainless steel mold.

[0064] Step 5): After the engineering plastic cools and hardens, remove it from the stainless steel mold.

[0065] Step 6): Clean the positioning protrusions on both sides of the engineering plastic filler skeleton structure taken out in step 5) to ensure that the tops of all positioning protrusions are smooth and free of foreign matter.

[0066] Step 7): Place the cleaned engineering plastic filler skeleton structure in a hot air circulation drying oven at 75° C. for 3 hours to remove internal stress, and cool to room temperature.

[0067] Step 8): Place the de-stressed engineering plastic filler skeleton structure into the product wax mold, make the wax mold on a wax press, and take out the mold after the wax mold cools down.

[0068] The wax model with anti-deformation engineering plastic filler skeleton structure was inspected for size. The wax model did not deform significantly at this plane, which met the casting requirements. Compared with adding process ribs at this thin-walled plane, it saved about 10,000 yuan in costs and shortened the processing cycle by 7 days. The casting was inspected for size and the dimensional accuracy reached CT7.

[0069] Comparative Example

[0070] Take a certain type of aluminum alloy rear cabin casting as an example. The material is ZL114A. There is a large air intake curved surface structure. The typical wall thickness is 4mm. The casting is Class I and the dimensional accuracy is CT7. The casting has a large air intake curved surface structure, and the wax part is very easy to deform.

[0071] The wax mold is made directly on the wax press, and the mold is taken out after the wax mold cools down. The size of the wax mold without the anti-deformation engineering plastic filler skeleton structure was inspected, and it was found that the wax part of the large air inlet curved surface structure had obvious deformation. After local repair and correction, it could barely meet the casting requirements. In order to prevent the wax part from deforming during subsequent transportation and shell making, 10 process ribs were evenly bonded on the curved surface. After the casting was poured, the size was scanned and it was found that the dimensional accuracy was only CT8. Then repeated corrections were performed, and the cutting and grinding of the process ribs took a long time. Compared with the wax mold with an anti-deformation engineering plastic filler skeleton structure designed at the thin-walled curved surface, the whole process cost about 20,000 yuan more and the delay cycle was 10 days.

[0072] In summary, the present invention adds an engineering plastic skeleton to the mold during wax model making for wax pressing. Since engineering plastics have good mechanical strength and dimensional stability, this type of wax part will not produce permanent plastic deformation during the subsequent trimming, assembly, placement and shell making process, which will lead to serious out-of-tolerance problems in the contour of the casting surface. This not only effectively reduces the complexity of the product wax model mold structure design, but also avoids a large amount of subsequent processing of the casting, reduces the processing cost of the product, and significantly shortens the production cycle.

[0073] Matters not covered by the present invention are known technologies.

[0074] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A deformation-resistant engineering plastic filler skeleton structure, characterized in that: The filler skeleton structure has evenly distributed hole structures, and at the same time, completely identical positioning protrusions are evenly distributed on both sides of the skeleton structure; The diameter of the hole structure is 3-7 mm, and the interval between two adjacent hole structures is 30-50 mm; the wall thickness of the filler skeleton structure is between 1-3 mm, and arc transition is adopted at the corners and thick-thin joints; The filler skeleton structure is made of engineering plastics, which contain 15 to 25 parts by weight of ABS resin, 75 to 85 parts by weight of SAN copolymer and 0.8 to 1.5 parts by weight of auxiliary agent, wherein the sum of the added amounts of ABS resin and SAN copolymer must be 100 parts by weight, the auxiliary agent is a lubricant, and the ABS resin is an ABS resin obtained by an emulsion grafting-bulk SAN blending method.

2. The anti-deformation engineering plastic filler skeleton structure according to claim 1, characterized in that: Every 100 parts by weight of ABS resin contains 14 to 20 parts by weight of ABS grafted powder and 80 to 86 parts by weight of SAN copolymer, wherein the average rubber particle size of the ABS grafted powder is 0.2 to 0.5 μm; the ABS grafted powder is a grafted polymer formed by emulsion polymerization of 50 to 55 wt% of rubber particles formed by polybutadiene rubber and 45 to 50 wt% of SAN copolymer; Every 100 parts by weight of the SAN copolymer contains 15 to 25 parts by weight of acrylonitrile and 75 to 85 parts by weight of styrene, and the average molecular weight of the SAN copolymer is 180,000-300,000; The lubricant is one or more of vinyl distearate amide and stearate.

3. The anti-deformation engineering plastic filler skeleton structure according to claim 2, characterized in that: The ABS resin has a melt index of 3 to 8 g / 10 minutes at a test temperature of 220° C. and a load of 10 kg.

4. The anti-deformation engineering plastic filler skeleton structure according to claim 2, characterized in that: The stearate is one or more of magnesium stearate, calcium stearate, zinc stearate and barium stearate.

5. A method for making a wax mold of an aluminum alloy precision casting with a deformation-resistant engineering plastic filler skeleton structure as claimed in claim 1, characterized in that: The specific steps include: 1) According to the structural characteristics of the casting, the anti-deformation engineering plastic filler skeleton structure is designed using 3D modeling software; 2) Design and manufacture molds for anti-deformation engineering plastic filler skeleton structures; 3) Drying of engineering plastics and preheating of molds; 4) Injecting engineering plastics into the mold; 5) After the engineering plastic cools and hardens, take the mold; 6) Clean the positioning convex points on both sides of the skeleton structure of the engineering plastic filler to ensure that the tops of all positioning convex points are smooth and free of foreign matter; 7) Place the engineering plastic filler skeleton structure in a hot air circulation drying oven at 70-80°C for 2-4 hours, and then cool it to room temperature; 8) Place the stress-relieved engineering plastic filler skeleton structure into the product wax mold; 9) Make wax models on a wax press.

6. The method for making a wax pattern of an aluminum alloy precision casting with a skeleton structure of an anti-deformation engineering plastic filler according to claim 5, characterized in that: In step 2), the mold of the anti-deformation engineering plastic filler skeleton structure is made of stainless steel material through mechanical processing.

7. The method for making a wax pattern of an aluminum alloy precision casting with a skeleton structure of anti-deformation engineering plastic fillers according to claim 5, characterized in that: In step 3), the drying temperature is 70-85° C. and the drying time is 2-6 hours; the mold is preheated to 50-100° C. before injection molding.

8. The method for making a wax pattern of an aluminum alloy precision casting with a skeleton structure of anti-deformation engineering plastic fillers according to claim 5, characterized in that: In step 4), the injection temperature of the engineering plastic is 240-265°C.

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