Table plate of folding table and manufacturing method of table plate

Abstract

The invention discloses a table board of a folding table and a manufacturing method of the table board, the manufacturing method adopts magnesium alloy die-casting forming of the table board, and the manufacturing method comprises the following steps: step 1, die design and preparation; 2, magnesium alloy smelting; thirdly, die-casting forming is conducted; and 4, carrying out follow-up treatment. The magnesium alloy die-cast table plate is used for replacing a traditional steel or aluminum alloy table plate, the lightweight effect is achieved, accessories of a traditional folding table can be integrated on the table plate, and the assembly process is simplified.

Description

Technical Field

[0001] This invention relates to the field of outdoor folding table technology, and in particular to a folding tabletop and its manufacturing method. Background Technology

[0002] Outdoor folding tables are widely used in camping, picnics, and patio leisure settings due to their portability and space-saving features. Currently, the tabletops of outdoor folding tables on the market primarily utilize the following manufacturing processes and materials: (1) Steel plate stamping + welding process: This is the most common manufacturing method. Cold-rolled steel plates are stamped and then welded to connect the tabletop with connectors, ribs and other components. This technical solution has obvious defects: First, the high density of steel makes the overall weight of the product heavy and difficult to carry, which violates the core requirement of portable outdoor furniture; Second, steel is very easy to corrode and rust in the humid outdoor environment. Although the surface is protected by spraying or plating, once the paint film is damaged, the rust will spread rapidly, affecting the appearance and service life; Finally, there is stress concentration at the weld, which is prone to cracking due to vibration during transportation or use, and the many weld points affect the appearance of the product.

[0003] (2) Wood / plastic panels + metal frame: This type of solution attempts to reduce weight. Wooden tabletops are heavy and prone to moisture, cracking, and mold; plastic tabletops (such as PP and ABS) are lightweight, but they have problems such as insufficient rigidity, easy aging, poor wind resistance, and low quality. They usually require complex metal frames for support, which is structurally redundant and has high production costs.

[0004] (3) Aluminum alloy profile splicing: As an improvement, aluminum alloy reduces weight and improves corrosion resistance to a certain extent. However, it is mainly produced by profile extrusion, CNC machining and bolt connection. The disadvantages are: in order to obtain sufficient strength, the profile wall thickness cannot be too thin, resulting in limited weight reduction effect; splicing structure requires a large number of connectors and assembly steps, resulting in low production efficiency, high cost, poor structural integrity and easy loosening; low design freedom, making it difficult to achieve complex integrated structure.

[0005] In summary, existing outdoor folding tabletop technologies struggle to achieve a good balance between lightweight design, structural strength, environmental weather resistance, production efficiency, and design freedom. Therefore, a new technological solution is urgently needed to address the shortcomings of existing technologies. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for manufacturing a folding tabletop, which produces a tabletop that is lightweight and has high structural strength.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention provides a method for manufacturing a folding tabletop, which is made of magnesium alloy through die casting, and includes the following manufacturing steps: Step 1, Mold Design and Preparation: Design the die-casting mold for the tabletop, then preheat the mold to a temperature ≥180°C and ≤280°C, and then spray the mold cavity with a release agent. The second step, magnesium alloy smelting: The surface of the magnesium alloy ingot is pretreated to improve its purity. Then, the magnesium alloy ingot is placed in a melting furnace for melting at a temperature of ≥650℃ and ≤750℃. A protective gas is introduced into the melting furnace to cover and protect the surface of the molten magnesium alloy to prevent combustion. Finally, the molten magnesium alloy liquid is purified to remove impurities. The third step is die casting: The molten magnesium alloy is transferred to the injection sleeve of the die casting machine, and then injected into the mold cavity at an injection speed of ≥6m / s and ≤10m / s. After injection, the mold is held under pressure for a time of <20ms. After holding the pressure, the mold is cooled. After the magnesium alloy solidifies, the mold is opened and the casting is removed. Step 4, follow-up processing: Remove the gate, flash and / or burrs from the casting, then perform surface treatment on the casting, and finally perform quality inspection on the finished table.

[0008] Furthermore, the process of injecting magnesium alloy liquid into the mold cavity is divided into three stages: First stage, slow injection stage: The injection punch advances at a speed of ≥0.2m / s and ≤0.5m / s to push the molten metal to the gate of the mold, thereby smoothly advancing the molten metal forward and preventing air entrapment. The second stage, the high-speed injection stage: When the molten metal reaches the gate, the injection punch instantly switches to a propulsion speed of ≥6m / s and ≤10m / s, and the cavity filling is completed within tens of milliseconds during this stage; The third stage, the boosting stage: At the moment the cavity filling is completed, the injection system applies a final pressure that is 10% to 20% higher than the injection pressure in the second stage, and holds the pressure for a period of time. This final pressure is transmitted to the inside of the casting through the still unsolidified molten metal to compensate for the casting.

[0009] Furthermore, the release agent is a water-based release agent. A special spray gun is used to evenly spray the water-based release agent onto the surface of the preheated mold cavity. After spraying, high-pressure air is used to blow away the excess release agent to ensure that the release agent film is uniform and free of liquid accumulation.

[0010] Furthermore, before injecting the molten magnesium alloy into the mold cavity, the composition of the molten magnesium alloy needs to be tested. A direct-reading spectrometer is used to sample and analyze the molten magnesium alloy, and the content of each element is adjusted to the standard ratio range.

[0011] Furthermore, the protective gas used in magnesium alloy smelting is a mixture of SF6 and dry air, or a mixture of SF6 and CO2, or a mixture of SF6 and N2.

[0012] Furthermore, during magnesium alloy smelting, refining agents or inert gases are used, and oxide inclusions and hydrogen are removed from the molten magnesium alloy by rotary degassing or static setting, to prevent slag inclusions and porosity in the castings.

[0013] Preferably, the magnesium alloy is of type AZ91D or AM60.

[0014] The present invention also provides a tabletop for a folding chair, which is manufactured using the above-described manufacturing method. The tabletop includes a base plate and a grid integrally formed on the back of the base plate, with the front of the base plate serving as the tabletop.

[0015] Preferably, the back of the substrate is integrally formed with a connection structure, which is a connecting piece with holes and / or a slot.

[0016] Preferably, the grid cells are shaped as one or more of rectangles, squares, hexagons, and triangles; Alternatively, the grid includes multiple first ribs and multiple second ribs, with each first rib being radially and uniformly distributed from the center of the substrate, and each second rib being distributed in concentric circles from the center of the substrate.

[0017] The tabletop of the outdoor folding table manufactured using the magnesium alloy die-casting process of this invention emphasizes lightweight and durability, and has the following advantages compared to existing technologies: 1. Material replacement: Using magnesium alloys (such as AZ91D) to replace traditional steel or aluminum alloys has a lightweight effect. The density of magnesium alloys is only 1 / 4 that of steel and 2 / 3 that of aluminum, which significantly reduces the weight of the final product and improves portability.

[0018] 2. Technological Innovation: The integrated die casting process replaces the traditional "stamping + welding" or "profile splicing" process, improving structural strength and reliability, eliminating stress concentration and potential cracking risks caused by welding points, and resulting in better overall structural integrity and more stable mechanical properties.

[0019] 3. Structural Integration: By adopting magnesium alloy die casting technology, multiple parts such as traditional tabletops, ribs (reinforcing ribs), and mounting supports (connectors) can be integrated into a single die casting. This reduces the number of parts, simplifies the supply chain and production assembly process, and lowers management and assembly costs. Production efficiency is improved because the die casting process has a fast production cycle, making it suitable for mass production and significantly shortening the production cycle of a single piece.

[0020] 4. Performance Optimization: Magnesium alloys have good damping and corrosion resistance. With the addition of subsequent surface treatments (such as micro-arc oxidation), their durability is enhanced. The good damping characteristics extend the product life. After surface treatment, their weather resistance and corrosion resistance are better than ordinary steel, making them more adaptable to harsh outdoor environments. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the first type of folding tabletop according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the second type of folding tabletop according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a grid with hexagonal cells according to an embodiment of the present invention. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0024] This embodiment discloses a method for manufacturing a folding tabletop. The tabletop is made of magnesium alloy through die casting and includes the following manufacturing steps: Step 1, Mold Design and Preparation: Design the die-casting mold for the tabletop, then preheat the mold to a temperature of 180℃ to 280℃, and then spray the mold cavity with a release agent. The second step, magnesium alloy smelting: The surface of the magnesium alloy ingot is pretreated to improve its purity. Then, the magnesium alloy ingot is placed in a melting furnace for melting at a temperature of ≥650℃ and ≤750℃. A protective gas is introduced into the melting furnace to cover and protect the surface of the molten magnesium alloy to prevent combustion. Finally, the molten magnesium alloy liquid is purified to remove impurities. The third step is die casting: The molten magnesium alloy is transferred to the injection sleeve of the die casting machine, and then injected into the mold cavity at an injection speed of ≥6m / s and ≤10m / s. After injection, the mold is held under pressure for a time of <20ms. After holding the pressure, the mold is cooled. After the magnesium alloy solidifies, the mold is opened and the casting is removed. Step 4, follow-up processing: Remove the gate, flash, and burrs from the casting, then perform surface treatment on the casting, and finally conduct quality inspection on the finished surface-treated table.

[0025] The specific contents of mold design and preparation include: (a) Mold Design (1) 3D modeling: Based on the 3D drawings of the folding table, use software to design the 3D model of the die-casting mold for the folding table. The software can be CAD or SW, etc. The design should fully consider the shrinkage rate of magnesium alloy (usually 0.5% to 0.7%), draft angle, and subsequent machining allowance.

[0026] (2) The die casting mold includes: runner system, cooling system and ejection system.

[0027] The runner system includes: ① Gate: The entrance for molten metal to enter the mold cavity. Its location, number, and shape are crucial, directly affecting the filling pattern of the molten metal and the quality of the final product. For large flat parts such as tabletops, fan-shaped gates, wide-side gates, or multi-gate designs are often used to ensure that the molten metal fills the mold cavity smoothly and evenly, avoiding turbulence and air entrapment.

[0028] ② Flow channel: The channel connecting the pressure chamber and the gate.

[0029] ③ Overflow groove: Located in the final filling area of ​​the mold cavity and in places where air may be trapped, it is used to contain cold metal and gas and ensure the density of the product.

[0030] ④ Venting groove: A very narrow and shallow groove (usually less than 0.15 mm deep) used to expel air from the cavity during the injection process and prevent air bubbles from forming inside the product.

[0031] The cooling system operates as follows: a network of pipes is installed inside the mold, and the mold temperature is precisely controlled by circulating cooling water (or oil) to ensure that the casting solidifies quickly and evenly, shortening the production cycle and improving production efficiency.

[0032] Ejection system: The design includes ejector pins, ejector plates, and other mechanisms to ensure that the casting can be smoothly ejected from the mold after cooling without causing deformation or damage.

[0033] (3) Selection of mold material: Hot work mold steel (such as H13 steel) is used because it has extremely high thermal strength, thermal fatigue toughness, wear resistance and tempering stability, so as to withstand the high-speed scouring of magnesium alloy melt and the harsh working conditions of hot and cold alternation.

[0034] (4) Mold processing and assembly: The mold steel is processed into the designed shape by precision processing methods such as CNC (numerical control milling machine), EDM (electrical discharge machining), and wire cutting, and finally assembled, debugged and tested.

[0035] (ii) Mold preheating Before production begins, the assembled mold must be preheated. Typically, a mold temperature controller, gas heater, or electric heating element is used to heat the surface temperature of the mold cavity to ≥180°C and ≤280°C.

[0036] The purpose of mold preheating is to: avoid "quenching" when molten metal comes into contact with a cold mold, which can lead to defects such as insufficient filling and cold shuts; reduce the thermal stress between the mold and the casting, thus extending the mold life; and help the release agent form a uniform film on the surface of the cavity.

[0037] (iii) Spraying release agent Use a dedicated spray gun to evenly spray the water-based release agent onto the surface of the preheated mold cavity. After spraying, use high-pressure air to blow away any remaining liquid and ensure that the release agent film is uniform and free of residue.

[0038] The purpose of spraying release agent: ① Lubrication: helps the cooled casting to be smoothly separated and removed from the mold.

[0039] ② Heat insulation: A protective film is formed on the surface of the mold to reduce the thermal shock of molten metal to the mold.

[0040] ③Auxiliary cooling: The evaporation of moisture in the release agent will take away some heat.

[0041] The specific details of magnesium alloy smelting include: (a) Raw material preparation The main raw material is AZ91D or AM60 magnesium alloy ingots that conform to national standards (such as GB / T19078-2016) or ASTM standards. Before use, the magnesium ingots need to be pretreated, such as by sandblasting or scraping, to remove oxides, moisture and oil adhering to the surface and ensure the purity of the smelting.

[0042] (ii) Smelting The pretreated magnesium ingots are added to a sealed melting furnace. The melting furnace is typically a dual-chamber design: a melting chamber and a supply chamber. In the melting chamber, the magnesium alloy is melted by resistance heating or gas heating and maintained within a precise temperature range of 650°C to 750°C.

[0043] Protective gas: Throughout the smelting and holding process, a protective gas must be continuously introduced into the furnace, typically a mixture of SF6 (sulfur hexafluoride) and dry air or CO2 and N2. SF6 forms a dense layer on the surface of the molten magnesium. and The composite protective film effectively isolates oxygen and prevents the magnesium liquid from burning and excessive oxidation.

[0044] (III) Melt treatment Refining / purification: Using refining agents or introducing inert gases (such as Ar), oxide inclusions and hydrogen in the molten magnesium are removed by rotating degassing or allowing it to stand, preventing slag inclusions and porosity in the casting.

[0045] Composition analysis: The magnesium liquid in the molten pool was sampled and analyzed using a direct-reading spectrometer, and the content of each element was adjusted to the standard ratio range.

[0046] (iv) Transfer of liquid metal The molten, pure magnesium liquid is precisely drawn from the supply chamber using a metering pump (usually an electromagnetic or mechanical pump), and then transported through insulated pipes to the injection sleeve of the die-casting machine. The metering pump's extremely high precision is crucial for ensuring stable weight of the die-cast parts and reducing flash. The entire process is conducted under a protective gas atmosphere, completely avoiding the oxidation and gas intake risks associated with traditional scooping methods.

[0047] The specific details of die casting include: (a) Mold closing and mold locking After the robotic arm or manual cleaning of the mold, the die-casting machine mold and stationary mold close at high speed, applying a huge clamping force. For large tables, the clamping force may need to be hundreds or even thousands of tons to prevent the mold from being forced open under high-pressure injection.

[0048] (ii) Pressure injection This is a precision control process that is carried out in multiple stages: Slow injection stage: The injection punch advances at a slower speed (≥0.2m / s and ≤0.5m / s) to push the molten metal in the pressure chamber to the gate of the mold. This stage aims to smoothly advance the molten metal and prevent air entrapment.

[0049] High-speed injection stage: When the molten metal reaches the gate, the punch instantly switches to an extremely high speed (≥6m / s and ≤10m / s), using extremely high kinetic energy to inject the molten metal into the mold cavity. This stage must complete the filling within a very short time (usually tens of milliseconds) to ensure that the molten metal fills every corner of the cavity before solidification.

[0050] Pressurization stage: At the instant filling is completed, the injection system immediately applies an extremely high final pressure (typically 10% to 20% higher than the specific gravity injection pressure) and maintains it for a period of time (holding pressure). This pressure is transmitted to the interior of the casting through the still-unsolidified molten metal, compensating for the volume shrinkage during solidification, thereby greatly reducing shrinkage cavities and porosity defects, and improving the density and mechanical properties of the casting.

[0051] (III) Cooling and Solidification The molten metal comes into contact with the mold under high pressure, and the heat is rapidly carried away through the cooling channels inside the mold, causing it to solidify and take shape. The cooling time depends on the wall thickness of the casting and the mold temperature control, and is usually from ten to several tens of seconds.

[0052] (v) Mold opening and ejection After solidification, the clamping force is released, the moving mold retracts, and the mold opens. The ejection mechanism (ejector pins, ejector plate) then moves, pushing the formed magnesium alloy table casting out of the mold cavity.

[0053] (vi) Picking up the package A robot or operator uses a clamp to remove the casting and place it in a designated area or on a conveyor belt. Simultaneously, the mold cavity is checked for cleanliness in preparation for the next cycle.

[0054] The parts removed from the die-casting machine are merely blanks, called "die-cast blanks," and must undergo further processing to become qualified products. This subsequent processing includes: (a) Remove gate and burrs Specialized fixtures or robots are used to remove burrs and flash from the gating system, overflow channels, and parting surfaces through sawing, punching, and grinding.

[0055] (ii) Heat treatment Magnesium alloy die castings are typically subjected to T5 aging heat treatment (artificial aging alone) or T6 aging heat treatment (solution treatment + artificial aging).

[0056] T5: Heat the casting to approximately 200°C, hold at that temperature for a period of time, and then air cool. Main purpose: to eliminate internal stress and improve dimensional stability and hardness.

[0057] T6: First, solution treatment (holding at approximately 410°C), water quenching, followed by artificial aging (holding at approximately 200°C). Main purpose: to significantly improve the strength and hardness of the casting, but it is more expensive and carries a greater risk of deformation. For outdoor tabletops where strength requirements are not extreme, T5 treatment is more commonly used.

[0058] (III) Surface Treatment This is a crucial step in ensuring the corrosion resistance of outdoor products.

[0059] (1) Pretreatment: Degreasing (removing oil stains), pickling (removing surface oxides), activation and other chemical treatments are carried out in sequence to prepare for subsequent processes.

[0060] (2) Core processing (choose one or a combination of three) Micro-arc oxidation (MAO): In an environmentally friendly electrolyte, a highly hard, corrosion-resistant, and wear-resistant ceramic oxide film is grown in situ on the surface of magnesium alloys using high voltage. This is currently one of the most advanced surface treatment methods for magnesium alloys, offering excellent performance, but at a high cost.

[0061] Electrophoretic coating (E-coating): The workpiece is immersed in an electrophoretic paint solution, and a direct current is applied. The paint particles move directionally to the workpiece surface and deposit to form a uniform and dense paint film. It has good corrosion resistance and can be used as a base coat.

[0062] Powder coating: This involves spraying charged plastic powder onto the surface of a workpiece, followed by high-temperature baking to cure and form a coating. It offers a variety of colors, is aesthetically pleasing, and has good weather resistance, making it a common final treatment method for outdoor furniture.

[0063] Typical process: Micro-arc oxidation (providing basic protection) + powder coating (providing color and additional protection) is the top configuration for outdoor tabletops.

[0064] (iv) Finishing and Testing (1) Machining: If extremely high flatness or mounting holes are required, CNC precision milling may be necessary.

[0065] (2) Inspection: Dimensional inspection: Use calipers, coordinate measuring machines (CMMs), etc. to inspect critical dimensions.

[0066] Visual inspection: Check the surface for defects such as scratches, pores, and cold shuts.

[0067] Performance testing (spot checks): may require X-ray flaw detection (to check for internal porosity), metallographic analysis, salt spray test (to test corrosion resistance), etc.

[0068] (v) Assembly and Packaging The processed tabletop is then assembled with the magnesium alloy or aluminum alloy frame, hinges, and other components of the folding table before being packaged and stored.

[0069] like Figures 1 to 3As shown, this embodiment also provides a tabletop manufactured using the above-described method. The tabletop includes a base plate 1, side plates 2, and a grid 3. The front of the base plate 1 serves as the tabletop (usable surface for placing items). The side plates 2 and the grid 3 are integrally formed on the back of the base plate 1. The side plates 2 are perpendicular to the base plate 1 and located at the edge of the back of the base plate 1. The side plates 2 and the grid 3 help to improve the strength of the tabletop; therefore, the base plate 1 can be made relatively thin.

[0070] In a preferred embodiment, the substrate thickness is 2.5 mm, the height of the grid protruding from the back of the substrate is 2 mm, the width of each grid is slightly less than the substrate thickness, and the width of the grid is typically 1.5 mm.

[0071] The side plate 2 extends at least partially from the back edge of the substrate 1, thereby increasing the strength of the substrate edge. Preferably, the side plate 2 coincides with the contour of the substrate 1, and the grid 3 is located inside the space enclosed by the side plate 2.

[0072] In a preferred embodiment, such as Figure 2 and Figure 3 The height of the side panel 2 protruding from the base plate 1 is greater than the height of the grille 3 protruding from the base plate 1. When viewed from the side, the grille 3 will be blocked by the side panel 2. Since the appearance requirements of the side panel 2 are usually consistent with the appearance requirements of the front of the table, the appearance requirements of the grille 3 are usually lower. The side panel 2 blocking the grille 3 is beneficial to the aesthetics of the side of the table.

[0073] The back of substrate 1 is formed with a connecting structure for connecting other accessories of the folding table, such as... Figure 2 It is provided with a slot for insertion with table leg 4, or with a connecting piece 5 with holes for hinge connection with table leg 4 or telescopic cylinder (pneumatic cylinder or hydraulic cylinder).

[0074] Some folding tables have more than two tabletops, and when the table is folded, all the tabletops are stacked together. The adjacent tabletops are hinged together, specifically, the side panels 2 of the adjacent tabletops overlap and a hinge hole 6 is provided at the overlap. A hinge shaft is provided in the hinge hole 6, and the hinge shaft can be a rivet, screw, or pin, etc.

[0075] A folding table can also have only one tabletop, whose grid 3 includes multiple first ribs 7 and multiple second ribs 8. Each first rib 7 is radially and evenly distributed from the center of the base plate 1, and each second rib 8 is distributed concentrically around the center of the base plate 1. All first ribs 7 intersect with all second ribs 8. This grid 3 is more suitable for circular and similar regular polygonal tabletops. Preferably, as... Figure 1 The thickness of the first rib 7 protruding from the base plate 1 decreases from the center of the base plate 1 to the edge of the base plate 1, and several insertion holes are formed in the center of the back side of the base plate 1 for inserting table legs 4.

[0076] Grid 3 can also have other structures. For example, the cell shapes of Grid 3 include rectangles and squares, and a mixture of rectangular and square cells. The cell shapes of Grid 3 can also be hexagons or other polygonal structures.

[0077] The cell area of ​​the grid 3 is not necessarily the same. In areas where the tabletop is subjected to greater stress, the cells of the grid 3 can be set more densely, and the strength of the substrate 1 in the stressed areas can be improved by using more ribs.

[0078] The tabletop provided in this embodiment has the following advantages compared to tabletops in the prior art: 1. Material replacement: Using magnesium alloys (such as AZ91D) to replace traditional steel or aluminum alloys has a lightweight effect. The density of magnesium alloys is only 1 / 4 that of steel and 2 / 3 that of aluminum, which significantly reduces the weight of the final product and improves portability.

[0079] 2. Technological Innovation: The integrated die-casting process replaces the traditional "stamping + welding" or "profile splicing" process, improving structural strength and reliability, eliminating stress concentration and potential cracking risks caused by welding points, and resulting in better overall structural integrity and more stable mechanical properties.

[0080] 3. Structural Integration: Multiple parts such as the tabletop, ribs (reinforcing ribs), and mounting brackets (connectors) are integrated into a single die-cast part. This reduces the number of parts, simplifies the supply chain and production assembly process, and lowers management and assembly costs. Production efficiency is improved because the die-casting process has a fast production cycle, making it suitable for mass production and significantly shortening the production cycle of a single piece.

[0081] 4. Performance Optimization: Magnesium alloys have good damping and corrosion resistance. With the addition of subsequent surface treatments (such as micro-arc oxidation), their durability is enhanced. The good damping characteristics extend the product life. After surface treatment, their weather resistance and corrosion resistance are better than ordinary steel, making them more adaptable to harsh outdoor environments.

[0082] The formation principle of the ribs in grille 3: The ribs on the lower surface of the magnesium alloy tabletop are formed in one piece using a die-casting mold. The principle is as follows: Negative shape of the mold cavity: The die-casting mold consists of two halves (moving mold and fixed mold). The lower surface of the table is formed by the moving mold. During the manufacturing of the moving mold, grooves that are completely opposite to the shape of the ribs are engraved on its surface through processes such as CNC machining and EDM.

[0083] High-pressure filling: When molten magnesium alloy is injected into the mold cavity at high speed under high pressure (usually hundreds of tons), the liquid instantly fills every corner, including these carved grooves.

[0084] Rapid cooling and solidification: The molten metal cools and solidifies rapidly upon contact with the mold, perfectly replicating the shape of the mold cavity. Thus, the grooves on the mold become the protrusions, or ribs, on the part.

[0085] Ejection and demolding: After molding, the mold opens, and the ejector mechanism ejects the part. Because magnesium alloys shrink slightly after solidification, and the mold is designed with a certain draft angle (usually 0.5° to 2°), even with complex ribs, demolding can be successful.

[0086] Simply put: Ribs are formed when molten metal fills the "grooves" of the lower mold under high pressure and then cools. They are an integral part of the entire part, not a later connection.

[0087] The technical effects brought by the ribs: (1) Significantly improves rigidity and bending strength: According to the principle of moment of inertia in mechanics of materials, the bending capacity of a material is proportional to the cube of the distance from the neutral axis of its cross section. The ribs significantly increase the material distribution in the thickness direction of the tabletop, which is equivalent to achieving the effect of a "solid thick plate" without significantly increasing the weight. This allows relatively thin tabletops (such as 2mm to 3mm) to withstand large longitudinal loads (such as heavy objects) and lateral loads (such as lateral thrust), preventing the tabletop from bending, deforming or shaking, and ensuring stability and safety in use.

[0088] (2) Achieving lightweight: If the entire tabletop were made into a solid board with the same thickness as the base and ribs, the weight would be enormous. Rib structure is an equal strength design, where material is placed only where it is most needed (stress points), and material is removed where it is not needed (the center of the panel) to form cavities.

[0089] (3) Improve thermal shrinkage behavior and prevent deformation: Die-cast parts shrink unevenly during cooling, and large flat areas are prone to defects such as shrinkage and warping. Regularly arranged ribs divide the large flat surface into multiple small areas, forming uniform cooling channels, making heat dissipation and shrinkage more uniform and consistent. This reduces the overall deformation risk of the tabletop and ensures the flatness of the tabletop.

[0090] (4) Improved heat dissipation and damping: The ribs increase the surface area, which is beneficial for heat dissipation. At the same time, the structure itself can effectively disperse and absorb vibration energy. This improves the comfort of using the product (e.g., faster heat dissipation when placing a hot pot) and the structural stability (reducing resonance).

[0091] Different shapes of ribs form different "ribbed structures", which have different mechanical properties and applicable scenarios.

[0092] Comparison table of technical characteristics and application scenarios of different types of grilles

[0093] From the perspective of stress concentration, triangular meshes exhibit a more pronounced stress concentration effect at their intersections, potentially leading to fracture under extreme overload. Square meshes are less affected. Circular and hexagonal streamlined designs better distribute stress.

[0094] From the perspective of mold manufacturing and demolding, square and triangular grid molds are the easiest to process. Hexagonal and circular molds (especially deep ribs) have higher requirements for mold processing and demolding.

[0095] In conclusion, for outdoor folding tables, hexagonal honeycomb mesh is generally the optimal solution in terms of performance, achieving the best balance between lightweight and rigidity; while square mesh is the most common choice due to its excellent cost-effectiveness. The final choice should be based on a comprehensive consideration of product cost, performance goals, and appearance.

[0096] The core improvement of the new process provided in this embodiment lies in "achieving a synergistic improvement in product performance and production efficiency through material revolution and process innovation".

[0097] From the user's perspective: they have obtained a lighter, more portable, more durable, and more aesthetically pleasing product.

[0098] From the manufacturer's perspective: it enables a more efficient, integrated, and scalable production method.

[0099] Ultimately, magnesium alloy die casting technology provides an excellent technical solution for resolving the contradiction between lightweight, robustness, and production cost in outdoor folding tables.

[0100] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features therein. These modifications or substitutions do not cause the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

Claims

1. A method for manufacturing a folding tabletop, characterized in that, The tabletop is made of magnesium alloy through die casting, and the manufacturing process includes the following steps: Step 1, Mold Design and Preparation: Design the die-casting mold for the tabletop, then preheat the mold to a temperature ≥180°C and ≤280°C, and then spray the mold cavity with a release agent. The second step, magnesium alloy smelting: The surface of the magnesium alloy ingot is pretreated to improve its purity. Then, the magnesium alloy ingot is placed in a melting furnace for melting at a temperature of ≥650℃ and ≤750℃. A protective gas is introduced into the melting furnace to cover and protect the surface of the molten magnesium alloy to prevent combustion. Finally, the molten magnesium alloy liquid is purified to remove impurities. The third step is die casting: The molten magnesium alloy is transferred to the injection sleeve of the die casting machine, and then injected into the mold cavity at an injection speed of ≥6m / s and ≤10m / s. After injection, the mold is held under pressure for a time of <20ms. After holding the pressure, the mold is cooled. After the magnesium alloy solidifies, the mold is opened and the casting is removed. Step 4, follow-up processing: Remove the gate, flash and / or burrs from the casting, then perform surface treatment on the casting, and finally perform quality inspection on the finished table.

2. The method for manufacturing a folding tabletop according to claim 1, characterized in that, The process of injecting magnesium alloy liquid into the mold cavity is divided into three stages: First stage, slow injection stage: The injection punch advances at a speed of ≥0.2m / s and ≤0.5m / s to push the molten metal to the gate of the mold, thereby smoothly advancing the molten metal forward and preventing air entrapment. The second stage, the high-speed injection stage: When the molten metal reaches the gate, the injection punch instantly switches to a propulsion speed of ≥6m / s and ≤10m / s, and the cavity filling is completed within tens of milliseconds during this stage; The third stage, the pressurization stage: At the moment the cavity filling is completed, the injection system applies a final pressure that is 10% to 20% higher than the injection pressure in the second stage, and holds the pressure for a period of time. This final pressure is transmitted to the inside of the casting through the still unsolidified molten metal to compensate for the casting.

3. The method for manufacturing a folding tabletop according to claim 1, characterized in that, The release agent is a water-based release agent. A special spray gun is used to evenly spray the water-based release agent onto the surface of the preheated mold cavity. After spraying, high-pressure air is used to blow it off to make the release agent film uniform and free of liquid accumulation.

4. The method for manufacturing a folding tabletop according to claim 1, characterized in that, Before injecting the molten magnesium alloy into the mold cavity, the composition of the molten magnesium alloy needs to be tested. A direct-reading spectrometer is used to sample and analyze the molten magnesium alloy, and the content of each element is adjusted to the standard ratio range.

5. The method for manufacturing a folding tabletop according to claim 1, characterized in that, The protective gas used in magnesium alloy smelting is a mixture of SF6 and dry air, or a mixture of SF6 and CO2, or a mixture of SF6 and N2.

6. The method for manufacturing a folding tabletop according to claim 1, characterized in that, During magnesium alloy smelting, refining agents or inert gases are used, and oxide inclusions and hydrogen are removed from the molten magnesium alloy by rotary degassing or static setting, to prevent slag inclusions and porosity in the castings.

7. The method for manufacturing a folding tabletop according to claim 1, characterized in that, The magnesium alloy is designated as AZ91D or AM60.

8. A tabletop for a folding chair, characterized in that, The tabletop is manufactured using the manufacturing method described in any one of claims 1 to 7, and includes a base plate and a grid integrally formed on the back of the base plate, with the front of the base plate serving as the tabletop.

9. The tabletop of the folding chair according to claim 8, characterized in that, The back of the substrate has an integrally formed connection structure, which is a connecting piece with holes and / or a slot.

10. The tabletop of the folding chair according to claim 8, characterized in that, The grid cells are shaped like one or more of the following: rectangles, squares, hexagons, and triangles. Alternatively, the grid includes multiple first ribs and multiple second ribs, with each first rib being radially and uniformly distributed from the center of the substrate, and each second rib being distributed in concentric circles from the center of the substrate.

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