A creep molding method for mixed injection molded carbon fiber sheet products

Abstract

This invention relates to the field of material mixing injection molding technology, specifically a creep forming method for mixing injection molding carbon fiber sheet products, comprising the following steps: shaping by applying force with a robotic arm; controlling the temperature to keep the material under stress below plastic deformation for a long time, and continuously baking at a constant temperature to achieve the shaping effect; and correcting the material using a shaping fixture. The main process is to shape the material through creep. This invention has a reasonable technical approach and improves the yield rate of production.

Description

[Technical Field]

[0001] This invention relates to the field of material mixing injection molding technology, specifically a creep molding method for mixing injection molding carbon fiber sheet products. [Background Technology]

[0002] During production, when materials need to be mixed and injection molded according to actual requirements, carbon fiber materials are used in production. However, carbon fiber materials often exhibit different degrees of expansion and contraction with the injection material under different temperatures and pressures. Therefore, when the material is about to be molded or has already been molded, the material product often deforms. We have very high requirements for the specifications and processes of the material products. In order to achieve the current level of precision, the product shaping process is essential.

[0003] The existing method is to use thermal shaping technology to shape the product, that is, to melt and soften the material and then manually shape it to adjust its shape. However, this method often exceeds the elastic limit of the material, causing the material to crack, resulting in a low yield rate and affecting the entire production process. Alternatively, the method of removing burrs is also used, but this often affects the specifications of the material and causes unnecessary waste of raw materials. It may also lead to excessive removal and product scrap.

[0004] In view of this, it is necessary to invent a method that can be applied to material products during injection molding to shape them well and make the product shape successfully. [Summary of the Invention]

[0005] Therefore, the purpose of this invention is to provide a creep aging molding method for mixed injection molding of carbon fiber sheet products. Compared with the previous method, this method can better shape the material product, improve the yield, avoid product cracking, and save material waste.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A creep-forming method for mixed injection-molded carbon fiber sheet products includes the following steps:

[0008] (1) Shaping is performed by applying force with a robotic arm;

[0009] (2) Control the temperature so that the material is under stress below the plastic deformation for a long time and is baked at a constant temperature to achieve the shaping effect;

[0010] (3) Use shaping jigs to correct the shape of material products.

[0011] The robotic arm shaping process utilizes a robotic arm fixture, along with a suction cup, support frame, and shaping column.

[0012] The creep shaping process induces creep in the material while maintaining constant stress.

[0013] During the creep shaping process, the material product is continuously baked and shaped at a constant temperature for a certain period of time.

[0014] The product undergoes creep initially when exposed to temperature baking; the creep occurs instantaneously.

[0015] The shaping fixture is used to correct the material after baking, when there is still residual heat, by using shaping columns, support frames, and shaping fixtures.

[0016] The creep shaping does not change the material's ductility limit.

[0017] Compared with existing technologies, the method of this invention does not result in the material product cracking due to exceeding its elastic strength, nor does it waste raw materials, thus improving the yield rate of the material product. [Attached Image Description]

[0018] Figure 1 This is a schematic diagram of the steps of the method of the present invention.

[0019] Figure 2 This is a schematic diagram of the relationship curve of the method of the present invention.

Detailed Implementation Methods

[0020] To further understand the purpose, technical effects, and technical means of this invention, a detailed description is provided below with reference to the accompanying drawings. Figure 1 , Figure 2 As shown, the present invention provides a creep forming method for mixed injection molding carbon fiber board products. This method mainly utilizes the characteristics of creep and adopts creep forming to achieve the purpose of forming. The creep forming method includes the following steps: S1: robotic arm forming (2), S2: low temperature baking forming (3), S3: forming fixture straightening (4).

[0021] Step S1: In mold production, after the mixed injection molded product (1) is formed, due to the high precision requirements of the molded product, and the fact that the product will have burrs during molding, in order to meet the process requirements, the mixed injection molded product (1) is initially shaped. When the material temperature is about 80°C, the material is opened and injected. Since the material still has residual heat at this time, it is not cooled down. While the material is still at a low temperature, the material is placed on the support frame. At the same time, the suction cup is used to adsorb the material product. Then, the shaping column and the production line are used. During production, robotic arms and other devices shape the product. Suction cups pick up the concave parts of the product, and shaping columns and robotic arms gently press down the irregularly convex parts. Support frames are used to pad the parts of the product that cannot reach the support frames due to their irregularity. Because the product is relatively soft at this stage, the protrusions or concave parts on both sides are padded so that the shaping columns and robotic arms can deform it. At this point, the initial shaping is completed. In order to achieve a higher precision, the product manufacturing process requires post-processing. After post-processing, the material product is shaped again according to actual needs, and then the product is painted.

[0022] Step S2: After the product is painted, the product is baked and shaped at low temperature (3). Generally, when the material is subjected to external force, it deforms and the material itself generates a force that wants to prevent this deformation. This deformation is strain and this force is stress. In general, the stress changes with the strain. When the strain reaches a certain level, the material undergoes plastic deformation, which leads to the material breaking. If it does not exceed the plastic deformation, it is within the elastic limit range. Our low temperature baking and shaping (3) is carried out within this range. Creep refers to a slow change. When the stress of the material remains unchanged, the strain of the material increases with time. Creep will occur at any temperature, but it is not obvious when the temperature is too low. Therefore, we mainly keep the material at a temperature higher than the creep temperature. We usually keep a constant temperature of 85°C and place the material product in a fixed shape and relatively closed fixture to keep a constant temperature of 85°C for five minutes. In actual production, we found that with the creep deformation З as the vertical axis and time T as the horizontal axis, the two satisfy a relationship curve, which is divided into three stages:

[0023] Phase 1: Initially, time is zero, and the material instantly undergoes creep. The creep deformation on the vertical axis does not start from zero. When the product is first subjected to temperature baking, it undergoes instantaneous creep. Afterward, without applying any external force, the material is simply kept at a temperature of 85°C, which is higher than its creep temperature, for continuous baking. Since the creep temperature of the material product in this embodiment is low, the baking temperature is also low. As time progresses, the strain continues to increase, forming a smooth curve. If a straight line is drawn on the cross-section of the curve, it can represent its slope. As time goes by, the slope of the curve decreases, meaning that the creep rate is slowing down.

[0024] Second stage: After the initial creep stage, continue baking at a constant temperature. At this time, the creep basically presents a stable state. The slope of the creep versus time curve is basically fixed. Take ΔT per unit time, and the creep deformation per unit time is ΔЗ. Then the ratio of ΔT to ΔЗ is a constant. The curve of this stage is a straight line, also known as the creep stabilization stage.

[0025] The third stage: After the creep stabilization stage, if low-temperature baking continues, the creep of the material will increase with time. The creep continues to increase, and at this time, the creep deformation versus time curve is a concave upward curve. That is, the slope of the curve in this stage is always increasing, and the rate of increase is faster and faster, eventually reaching the limit and breaking. Therefore, in actual production, we usually achieve the best state by maintaining a constant temperature of 85℃ for five minutes, without over-shaping and without changing the material's elongation limit.

[0026] Step S3: Shaping with a shaping fixture (4). After the material product has been shaped by low-temperature baking (3), in order to prevent over-shaping, the temperature is generally 85°C for five minutes. When the baking is finished, if the shape of the material meets the process requirements, the product can be obtained (5). Otherwise, proceed to the next step: Shaping with a shaping fixture (4). Use the shaping fixture to stabilize and shape the product. When shaping by low-temperature baking (3), since it is shaped by temperature baking, the material product still has residual heat when the shaping is just finished. At this time, place the product on the support frame, make the shaping column in close contact with the product, place the product in the shaping fixture, turn on the switch, and use the shaping column to fix the product.

[0027] Furthermore, since the material is subjected to stress below its elastic limit and is in a creep state for an extended period of time, creep does not affect the material's ductility limit; that is, the material's original stretching limit will not change due to creep.

[0028] After implementing the above methods, the results are good in shaping applications of molded products, especially for fiber-reinforced materials mixed with injection molding. Because the material itself has poor ductility, it is easy to break if it exceeds the elastic limit. Therefore, by using materials below the elastic limit and extending the shaping time, problems such as reduced yield and easy product cracking during traditional shaping can be solved.

[0029] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can conceive of other specific embodiments of the invention without creative effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A creep forming method for mixed injection-molded carbon fiber sheet products, wherein creep forming is employed to achieve the desired result, the creep forming method comprising the following steps: (1) Robotic arm shaping: Shaping is performed by applying force through a robotic arm; (2) Low temperature baking and shaping: The temperature is controlled so that the material is under stress below the plastic deformation for a long time, and the constant temperature is continuously baked to achieve the shaping effect; During the low temperature baking and shaping process, the material product is continuously baked and shaped at a constant temperature of 85°C for five minutes. (3) Shaping with shaping fixtures: Shaping of material products using shaping fixtures; the shaping with shaping fixtures is performed when the material is still warm after baking, using shaping columns, support frames and shaping fixtures.

2. The method for creep molding of mixed injection-molded carbon fiber sheet products according to claim 1, characterized in that: The robotic arm shaping process utilizes a robotic arm fixture, along with a suction cup, support frame, and shaping column.

3. The method for creep molding of mixed injection-molded carbon fiber sheet products according to claim 1, characterized in that: The creep shaping process induces creep in the material while maintaining constant stress.

4. The method for creep molding of mixed injection-molded carbon fiber sheet products according to claim 1, characterized in that: The product undergoes creep initially when exposed to temperature baking; the creep occurs instantaneously.

5. The method for creep molding of mixed injection-molded carbon fiber sheet products according to claim 1, characterized in that: The creep shaping does not change the material's ductility limit.

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