A composite molding method for stamping dies for automotive body panels

Abstract

This invention relates to the field of mold design technology, specifically to a composite molding method for automotive body panel stamping dies. The method includes model making, casting process design, coating application, molding, melting, cooling, and casting removal. The molding steps include placing conformal chills at corresponding positions on the mold surface and applying additional coating; setting up ingates, runners, and sprues according to the molding process; after the coating around the conformal chills has dried, placing a sand box on the model, initiating resin sand mixing and sand embedding molding; placing sand-separating chills at the required locations; compacting the mold surface; smoothing the molding sand on the sand box surface; and allowing the resin sand to cure. Compared to existing technologies, this application solves the problems of low molding efficiency and high cost in automotive body panel stamping dies.

Description

Technical Field

[0001] This invention relates to the field of mold design technology, and in particular to a composite molding method for stamping dies for automotive body panels. Background Technology

[0002] The structure of automotive body panel molds mainly includes the molding surface that forms the shape of the body panel and the relief holes formed by the ribs supporting the bottom molding surface. Currently, automotive body panel production mainly adopts lost-mold casting, which involves machining foam boards through CNC programming, assembling them to form a foam model of the mold, coating the foam model, drying it, designing the casting process, connecting the gating system on the molding platform, and using conformal chills to cover the foam model directly on the molding surface or placing sand-isolating chills on the molding surface to ensure that defects such as shrinkage porosity and pitting do not occur in the subsequent molding surface processing of the casting. After molding, the sand box is turned over to embed sand on the bottom surface. After the sand embedding is completed, it is hoisted to the pouring area and connected to the negative pressure pipeline to await pouring.

[0003] In lost foam casting, resin sand is used for molding stamping dies, consuming resin and hardener. Resin sand has poorer fluidity than dry sand, and if the molding sand is not compacted during model embedding, sand adhesion defects will occur after pouring. Workers often damage the model surface with tools like tamping rods to compact the sand, creating defects. To save costs and improve competitiveness, foundries are increasingly replacing lost foam casting with resin sand casting. Lost foam casting uses dry sand, compacted by a vibratory compaction table, resulting in high molding efficiency and saving on resin and hardener costs. However, it cannot place direct conformal chills or sand-separating chills on the model surface because the molding sand is compacted by the vibratory compaction table. If chills are placed, they will shift when the vibratory compaction table is turned on, failing to achieve the desired effect. Therefore, this application discloses a composite molding method for automotive body panel stamping dies to ensure the processing quality of the stamping die while improving molding efficiency and reducing molding costs. Summary of the Invention

[0004] In view of this, the purpose of this invention is to propose a composite molding method for automotive body panel stamping dies, so as to solve the problems of low molding efficiency and high cost of automotive body panel stamping dies in the prior art.

[0005] To achieve the above objectives, the present invention provides a composite molding method for stamping dies of automotive body panels, comprising the following steps:

[0006] S1. Model Making: Make a foam model according to the drawing requirements;

[0007] S2. Casting process design: Set up the casting process according to the real casting method, and attach the inner gate to the model. After the model is inspected, send it to the drying room for coating.

[0008] S3. Coating: Apply coating according to the standard Baumé degree requirements and dry it. After drying, the coating thickness should not be less than 1.5mm. After the model is completely dry, reinforce it as required to improve the model's resistance to deformation under pressure.

[0009] S4. Shaping: Use resin sand to shape the surface on the shaping platform;

[0010] S5. Smelting: Control the temperature of molten iron according to the required pouring temperature. Before pouring, connect the air extraction port of the dry sand negative pressure sand box to the vacuum pump, turn on the vacuum pump, and pour when the negative pressure is controlled at 0.05MPa-0.06MPa.

[0011] S6. Cooling: After vacuum pressure holding in step S5, the cooling system is turned on to cool the sand box.

[0012] S7. Casting Shaking: Separate the molding sand and casting, and cut the gating and riser system to complete the composite molding process of automotive body panel stamping dies.

[0013] Preferably, the model making in step S1 includes the following steps:

[0014] Obtaining Drawings: First, obtain the product's design drawings or 3D model;

[0015] Prepare foam materials: Select suitable foam materials, including polystyrene and polyurethane foam. The materials should have a uniform texture, a smooth surface, and meet the requirements of the product.

[0016] Cutting foam blocks: Based on the size and shape of the product, use a hot wire cutter or CNC cutting equipment to cut the foam material into block-shaped foam model raw materials of the corresponding size;

[0017] Roughing and finishing: Roughing and finishing the foam block, roughly carving out the shape of the product on the foam block according to the product outline, so that it gradually approaches the shape required by the design.

[0018] Manual adjustments: Use planes and sandpaper to manually adjust the foam model to improve the accuracy of the product's outline and curved surfaces;

[0019] Surface treatment: Surface treatment, including sanding, filling and repair processes, is performed to improve the smoothness of the foam model surface and eliminate obvious blemishes and defects;

[0020] Combined with mold making: The foam model is combined with the mold making process. The foam model surface is sprayed with covering materials, including resin and paint, to increase the strength and wear resistance of the model.

[0021] Inspection: Inspect the completed foam model to ensure that its size, shape and surface quality meet the design requirements.

[0022] Preferably, the S4 modeling step includes the following steps:

[0023] Place the conformal chill directly on the corresponding position of the mold surface and apply paint to touch up the coating;

[0024] Set up the ingate, gating system, and sprue according to the molding process. After the paint is applied around the conformal chill and dried, place the sand box on the model.

[0025] Preferably, when placing the sand box on the model, the amount of sand in each direction should not be less than 120mm thick. Start the resin sand mixing and begin the sand embedding molding. Place the sand-insulating chills at the positions where sand-insulating chills are needed, with a sand-insulating thickness of 15mm-25mm. After the molding surface is firmly embedded, scrape the molding sand on the surface of the sand box and let it stand for the resin sand to cure. After 2.5h-3.5h, the resin sand will be completely cured, and then the sand box will be turned over.

[0026] Preferably, the S4 modeling step further includes the following steps:

[0027] Prepare a dry sand negative pressure sand box. Place 150mm thick dry sand on the bottom of the sand box, turn on the vibration to compact and level it. Put the entire sand box made of resin sand into the dry sand negative pressure sand box. Insert foam rods of the same diameter as positioning pins into the sprue. Connect the exposed section to the sprue ceramic pipe. Then add dry sand to bury the bottom surface and the perimeter of the sand box. Turn on the vibration for 30 seconds every 150mm of sand. Bury the entire resin sand mold in the dry sand negative pressure sand box, compact it, and level it.

[0028] Preferably, the S4 modeling step further includes the following steps:

[0029] Lay a layer of plastic sheeting on the surface of dry sand, then place a 50mm-100mm thick layer of dry sand on top of the plastic sheeting. Place the pouring cup at the top of the sprue and pile sand around the pouring cup to prevent it from moving.

[0030] Preferably, the pouring speed of molten iron in the S5 smelting step should follow the principle of "slow first, then fast, and then slow again", and the vacuum holding time after pouring should not be less than 1 hour.

[0031] The beneficial effects of this invention are as follows: This composite molding method for automotive body panel stamping dies requires the installation of various chills on the mold surface. Therefore, resin sand molding is used. After the mold surface and gating system are embedded together with resin sand, the mold is turned over after the molding sand has cured. Then, the entire turned-over mold is placed in a negative pressure sand box to create the bottom surface. The bottom surface has light-reducing holes formed by the intersection of ribs, and the structure is transparent, which is very suitable for dry sand filling and compaction. The bottom surface is embedded in the negative pressure sand box and the sprue is connected. The box is covered with plastic sheeting and the pouring cup is placed. Pour is carried out under negative pressure. By combining solid resin sand molding and dry sand lost foam molding, the processing quality of the stamping die is guaranteed while the molding efficiency is improved and the molding cost is reduced. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0035] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0036] like Figure 1 As shown, the composite molding method for automotive body panel stamping dies includes the following steps:

[0037] S1. Model Making: Make a foam model according to the drawing requirements;

[0038] S2. Casting process design: Set up the casting process according to the real casting method, and attach the inner gate to the model. After the model is inspected, send it to the drying room for coating.

[0039] S3. Coating: Apply coating according to the standard Baumé degree requirements and dry it. After drying, the coating thickness should not be less than 1.5mm. After the model is completely dry, reinforce it as required to improve the model's resistance to deformation under pressure.

[0040] S4. Shaping: Use resin sand to shape the surface on the shaping platform;

[0041] S5. Smelting: Control the temperature of molten iron according to the required pouring temperature. Before pouring, connect the air extraction port of the dry sand negative pressure sand box to the vacuum pump, turn on the vacuum pump, and pour when the negative pressure is controlled at 0.05MPa-0.06MPa.

[0042] S6. Cooling: After vacuum pressure holding in step S5, the cooling system is turned on to cool the sand box.

[0043] S7. Casting Shaking: Separate the molding sand and casting, and cut the gating and riser system to complete the composite molding process of automotive body panel stamping dies.

[0044] When using the above-mentioned process to shape stamping dies for automotive body panels, various chills need to be installed on the mold surface. Therefore, resin sand molding is used. After the mold surface and gating system are embedded together with resin sand, the sand mold is turned over after the molding sand has cured. Then, the entire turned sand mold is placed in a negative pressure sand box to create the bottom surface. The bottom surface has light-reducing holes formed by the intersection of rib plates, and the structure is transparent, which is very suitable for dry sand filling and vibration compaction. The bottom surface is embedded in the negative pressure sand box and the sprue is connected. The plastic sheet is covered and the pouring cup is placed. Pour is carried out under negative pressure. By combining solid resin sand molding and dry sand lost foam molding, the processing quality of the stamping die is guaranteed while improving molding efficiency and reducing molding costs.

[0045] Further, see attached document. Figure 1 The model creation in step S1 includes the following steps:

[0046] Obtaining Drawings: First, obtain the product's design drawings or 3D model;

[0047] Prepare foam materials: Select suitable foam materials, including polystyrene and polyurethane foam. The materials should have a uniform texture, a smooth surface, and meet the requirements of the product.

[0048] Cutting foam blocks: Based on the size and shape of the product, use a hot wire cutter or CNC cutting equipment to cut the foam material into block-shaped foam model raw materials of the corresponding size;

[0049] Roughing and finishing: Roughing and finishing the foam block, roughly carving out the shape of the product on the foam block according to the product outline, so that it gradually approaches the shape required by the design.

[0050] Manual adjustments: Use planes and sandpaper to manually adjust the foam model to improve the accuracy of the product's outline and curved surfaces;

[0051] Surface treatment: Surface treatment, including sanding, filling and repair processes, is performed to improve the smoothness of the foam model surface and eliminate obvious blemishes and defects;

[0052] Combined with mold making: The foam model is combined with the mold making process. The foam model surface is sprayed with covering materials, including resin and paint, to increase the strength and wear resistance of the model.

[0053] Inspection: Inspect the completed foam model to ensure that its size, shape and surface quality meet the design requirements.

[0054] The S4 modeling process includes the following steps:

[0055] Place the conformal chill directly on the corresponding position of the mold surface and apply paint to touch up the coating;

[0056] Set up the ingate, gating system, and sprue according to the molding process. After the paint around the conformal chills dries completely, place the sand box on the model. When placing the sand box on the model, ensure the sand thickness in each direction is not less than 120mm. Start resin sand mixing and begin sand embedding molding. Place sand-separating chills at the locations where they are needed, with a sand thickness of 15mm-25mm. After firmly embedding the molding surface, smooth the molding sand on the surface of the sand box and let it stand for the resin sand to cure. After 2.5-3.5 hours, when the resin sand is completely cured, turn the sand box over. Prepare a dry sand negative pressure sand box, place a 150mm thick layer of dry sand on the bottom of the sand box, turn on the vibration to compact and smooth it, and then place the resin sand... Place the entire sand box into the dry sand negative pressure sand box. Insert foam rods of the same diameter as positioning pins into the sprue. Connect the exposed section to the sprue ceramic pipe. Then add dry sand to bury the bottom surface and the perimeter of the sand box. Vibrate for 30 seconds every 150mm of sand. Bury the entire resin sand mold in the dry sand negative pressure sand box and compact it. Scrape it level. Lay a layer of plastic sheet on the surface of the dry sand, and then add another 50mm-100mm layer of dry sand on top of the plastic sheet. Place the pouring cup at the top of the sprue. Pile sand around the pouring cup to prevent it from moving.

[0057] In the S5 smelting process, the pouring speed of molten iron should follow the principle of "slow first, then fast, and then slow again". After pouring, the vacuum holding time should not be less than 1 hour.

[0058] The molding process requires the installation of various chills, so resin sand molding is used. After the molding surface and gating system are embedded in the resin sand, and the molding sand has cured, the sand mold is flipped over. Then, the flipped sand mold is placed into a negative pressure sand box to create the bottom surface. The bottom surface has light-reducing holes formed by the intersection of ribs, and the structure is transparent, which is very suitable for dry sand filling and compaction. The bottom surface is embedded in the negative pressure sand box and the sprue is connected. It is covered with plastic sheeting, and the pouring cup is placed. Pour is carried out under negative pressure. By combining solid resin sand molding and dry sand lost foam molding, the processing quality of the stamping die is ensured while improving molding efficiency and reducing molding costs.

[0059] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in the details for the sake of brevity.

[0060] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A composite molding method for stamping dies for automotive body panels, characterized in that, include The following steps are required: S1 creates a foam model and sets up the process according to the solid casting method, then attaches the inner gate to the model; S2 is coated with paint according to the standard Baume scale and dried until the coating thickness is not less than 1.5mm. After the model is completely dry, it is reinforced as required to improve its compressive strength and resistance to deformation. S3 Surface Resin Sand Molding: Arrange direct conformal chills at the corresponding positions on the surface and apply paint to the contact surface between the chills and the model. Set up sprues, gating systems and ingates according to the molding process. Control the sand intake in each direction to be no less than 120mm. Bury the sand in the molding and arrange sand-isolating chills at the required positions. The sand isolating thickness is 15–25mm. Let it stand for 2.5–3.5 hours until the resin sand cures, then turn the sand box over. S4 bottom dry sand negative pressure molding: Place 150mm thick dry sand on the bottom of the sand box, turn on the vibration to compact and level it, and put the entire sand mold made of resin sand into the dry sand negative pressure sand box; insert a foam rod of the same diameter as the sprue as a positioning pin in the sprue, and connect the sprue ceramic pipe at the exposed end; fill the sand box with dry sand and vibrate for 30s every 150mm thickness, so that the resin sand mold is completely buried by the dry sand; lay a layer of plastic sheet on the surface of dry sand and then lay another 50-100mm thick layer of dry sand on top of it, and place the pouring cup at the top of the sprue; S5 Smelting and Casting: Connect the air extraction port of the dry sand negative pressure sand box to the vacuum pump, and pour molten iron after pumping to a negative pressure of 0.05–0.06MPa. The pouring speed follows the pattern of "slow first, then fast, then slow again". After pouring, the vacuum pressure holding time shall not be less than 1 hour. S6 Cooling and Sand Removal: After pressure holding, the cooling system is turned on to cool the sand box. After cooling, the molding sand is separated from the casting and the gating and riser system is cut.

2. The method according to claim 1, characterized in that: Sand is piled around the pouring cup to prevent it from moving.

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