Design of the most popular pultrusion FRP window f

Design of pultrusion FRP window frame mold

1 Status and Prospect of pultrusion FRP window frame

glass fiber reinforced plastic (GFRP, commonly known as FRP) window frame is made of GFRP pultrusion hollow profile (hereinafter referred to as pultrusion profile). It is a new generation of window frames after wood, steel, aluminum alloy and plastic steel window frames. In the early 1980s, Canada successfully developed FRP window frames for the first time; In the 1990s, hydrogel immobilized biomolecules and cells, which rapidly expanded to the United States, Russia, Germany and Japan, have been widely used in analysis, medical diagnosis and other countries, with great prospects for development. At present, China has become the country with the largest output of building window frames. With the rapid development of China's economy, the rise of the real estate industry, the continuous improvement of the level of the construction industry, and the increasingly prominent building energy conservation, glass fiber reinforced plastic window frames make up for the shortcomings of plastic steel window frames such as low strength and easy aging, and are listed as an energy-saving product industry that the State encourages to develop. Because glass fiber reinforced plastic window frames have the advantages that wood window frames, steel window frames, aluminum alloy window frames and plastic steel window frames do not have, Therefore, the market application prospect of FRP window frames is very huge

2 technology of pultrusion FRP window frame

pultrusion FRP window frame is formed by pultrusion process with thermosetting unsaturated polyester resin as the matrix and glass fiber as the reinforcing material. The basic molding process is: the glass fiber is pulled by the traction device to cluster and impregnate with resin glue, and then enters the heated mold for curing and molding through the pre molding mold. Finally, the profiles of various specifications drawn out can be made into FRP window frames after treatment and processing

the pultrusion process of FRP products is shown in Figure 1

Figure 1 FRP pultrusion process flow

1. Steel fiber yarn frame; 2. Yarn guide plate; 3. Resin dipping device; 4. Preformed guide device; 5. Forming mold

6. traction device; 7. Cutting device

3 importance of die design for pultrusion FRP window frame

in the pultrusion process of FRP profile, the die is the intersection of various process parameters and one of the cores of pultrusion process. Compared with the quite mature plastic extrusion molding, pultrusion molding has similarities with it, but the pre grinding is only a physical change process, and the latter is accompanied by dynamic chemical reactions. The working condition of the die is much more complex than the former. At present, the influence theory of various factors has not been completely understood, so the design and manufacture of the pultrusion die is of great significance. It not only relates to the success or failure of the pultrusion process, determines the quality and output of the pultrusion products, but also affects the service life of the pultrusion die

3.1 material selection of mold

for pultrusion mold, the selection of mold material directly affects the performance of the mold, especially the pultrusion window frame profile. Because the window frame profile has a broad market prospect and a large demand, it requires that the service life of the mold itself should be particularly long. Therefore, the selection of window frame mold material requires the following properties

(1) high strength, fatigue resistance and wear resistance

(2) higher heat resistance and smaller thermal deformation

(3) good corrosion resistance

(4) good machinability and surface polishing performance

(5) small thermal deformation and good dimensional stability

3.2 selection of parting surface

pultrusion molds are generally assembled from several molds. In the mold design, the principle of selecting the parting surface is: on the premise of meeting the mold manufacturing, try to reduce the parting surface and ensure tight joint. Due to the complex shape of the pultrusion FRP window frame mold, it is particularly important to select the parting surface. In the mold design diagram of FRP window frame shown in Figure 2, the whole mold is divided into five parts as shown in the figure from the premise of meeting the mold manufacturing. At the same time, in order to ensure tight mold joint, the mold design method shown in the figure is adopted

Figure 2 Lazi mold of FRP window frame

3.3 mold entry design

when the glass fiber enters the molding mold after being impregnated with resin, the fiber bundle enters the mold under the traction of the molding machine. Because the fiber bundle at the entrance of the mold is very loose, it often accumulates and winds at the entrance, causing fiber breakage. Moreover, during the long-term use of the mold, due to the influence of accumulation and winding, it often causes serious wear and tear of the population and affects the product quality. To solve this problem. Pour a 1/4 elliptical section around the entrance of the mold (3) pour the rounded corner of the concrete surface with the strength grade of not less than C20 in the pit. At the same time, the entrance adopts a cone, with an angle of 5 ~ 8 ° and a length of 50 ~ 100mm, which can greatly reduce the occurrence of fiber breakage and improve the quality of glass steel pultruded products

3.4 determination of mold size

due to the thin wall thickness of FRP window frame, the heat conduction in the mold is fast, so the mold length should not be too long, which is also conducive to the smooth progress of mold machining and pultrusion process. Therefore, in the design, the mold length is related to the selection of raw materials. At present, the domestic mold length is generally designed to be about 900mm. Generally, the thickness of the mold is 2 ~ 3 times that of the product. The size of the mold cavity depends on the size and shrinkage of the product. For FRP window frame profiles, unsaturated polyester resin glass fiber system is generally used, and the shrinkage is generally about 2%

FRP window frame profiles are mostly hollow products, so special attention should be paid to the mandrel design. Generally, the effective length of the core mold is 2/3 ~ 3/4 of the mold length. In the process of pultrusion, the fixation and adjustment of the mandrel and the prevention of eccentricity should be considered. In addition, the mandrel should also consider the problem of counterweight. Comprehensively, for the mold with a mold length of about 900mm, the length of the mandrel can be designed to be about 1200mm

4 Conclusion

in recent years, the rapid development of China's FRP Industry and housing industry has provided a broad market for FRP window frames. The FRP window frame market has great potential. There is fierce competition in the FRP window market, which has just taken new steps in the development of (5) new material industry, and this competition is mainly quality competition. And high-quality, high-grade fiberglass window frames can be competitive, of which mold design is the key. Therefore, the design of pultrusion FRP window frame mold is of great significance. (end)