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Hand Lay-up Method Of Glass Steel Mold

Jun 29, 2020

FRP molds generally use hand lay-up molding method, and the molding circuit should be designed before production.

        Steps for making hand-layed glass fiber reinforced plastic sculpture

        Due to the advantages of flexible molding, short production and development cycle, good manufacturability, wear resistance, and long service life, FRP sculptures have been widely used in the sculpture industry, especially the production process of FRP handicraft sculptures based on hand lay-up molding technology has developed more rapidly . Sculpture pasting molding is also called hand lay molding or contact molding. First apply a layer of glue on the mold, then lay a cloth, soak the fiber in the glue and remove the air bubbles, then continue to mount it layer by layer until the layer is finished, and the finished product will be obtained after curing.

        There are two types of resin commonly used in sculpture: unsaturated resin and epoxy resin.

        ①Unsaturated resin molding preparation method: 190# resin 100 parts, cyclohexanone peroxide 4 parts; cobalt naphthenate solution 1-4 parts, appropriate amount of color paste. If it is prepared according to the production conditions by flow-through operation, put 100 kg of resin in the enamel basin, then add 4 kg of cyclohexanone oxide paste, stir well, then add an appropriate amount of titanium green paste, and the color can meet the required requirements. , And set aside. The advantage of unsaturated resins is that they are cheap.

        ②The advantage of epoxy resin is that it has low curing shrinkage rate and excellent electrical insulation performance. It is stable to various acids and alkalis and organic solvents. The tensile strength can reach 45MPa-70MPa and the bending strength can reach 90MPa-120MPa. The matching curing agent can use epoxy resin normal temperature E-999 curing agent. The thinner is acetone (or propylene oxide butyl ether). The mold gel coat adopts the mold gel coat which is resistant to high temperature, high hardness and good toughness. The produced fiber reinforced material uses 33g/m2 alkali-free chopped mat and 0.2mm glass fiber checkered cloth.

        Brush release agent: Before the FRP sculpture hand lay-up, first clean the cavity surface of the female mold; at the same time, cut the glass fiber mat into a shape similar to the shape of the cavity. If the cavity shape is complex, it can be cut into Several pieces of simple shapes are then put together when hand lay up. Apply a mold release agent to the surface of the mold cavity to facilitate smooth release of the molded product. When applying the mold release agent on the prototype and parting surface, it must be applied evenly and thoroughly. It must be applied 2-3 times. After the mold release agent applied in the previous pass is dried, the next pass can be applied. There are many types of mold release agent, one is kerosene (gasoline, etc.) plus floor wax; there is also a petroleum jelly plus engine oil; no matter how useful the paint is.

        Brushing the gel coat layer: After the release agent is completely dried, apply the special gel coat with a brush twice, the coating should be even, and the second layer should be applied after the first layer is initially set. It should be noted here that the gel coat should not be applied too thick to prevent surface cracks and wrinkles. The thickness of the gel coat layer is generally 0.5~0.8mm. The gel coat itself is a kind of resin. This kind of resin is very important when making FRP products by hand. It can not only play the role of a protective layer on the surface of the FRP, but also can play a decorative effect on the surface. Just add color paste to the gel coat. The surface of the product will have a corresponding color. Due to the different use environment and requirements of FRP products, different types of gel coat resins must be selected according to the actual situation. The current grades are: TM-33, TM-35, S-739, gel coat 33, etc. The gel coat can be applied to the mold cavity with a brush, or it can be sprayed onto it with a pneumatic spray gun. The spray gun is more uniform than the brush. The effect is better. At present, the spray coat is generally applied to the gel coat. The natural curing of the gel coat generally takes about half an hour. You can use an oven to speed up the curing time. When the sprayed gel coat is dry, you can start to paste the resin and glass fiber.

        Resin glue preparation of resin: First of all, it should be evenly mixed with the curing agent at a certain ratio to accelerate the curing time of the product. The grade of unsaturated resin is generally 191 and 196# resins. If you are using epoxy resin. According to the viscosity of the room temperature resin, it can be properly preheated. Then mix 100 parts of WSP6101 epoxy resin and 8-10 parts (mass ratio) of acetone (or propylene oxide butyl ether) in a clean container. After stirring well, add 20 to 25 parts of curing agent ( The amount of curing agent added should be appropriately increased or decreased according to the on-site temperature), stir quickly, and perform vacuum defoaming for 1min~3min to remove bubbles in the resin glue, and then it can be used.

        Glass fiber layer-by-layer paste: When the gel coat is initially set and the hand feels soft but not sticky, apply the prepared resin glue to the gel coat, then spread a layer of chopped felt, and use a brush to apply the cloth Laminate compaction to make the glue content uniform and discharge air bubbles. In some cases, you need to use a sharp object to lift the bubbles. The second layer of chopped strand mat must be laid after the first layer of resin glue has set. After that, it can be pasted layer by layer in the form of a cloth and a felt. After pasting 2 to 3 layers each time, after the peak of resin curing and exotherm has passed (that is, when the resin glue is viscous, it is generally at 20 ℃ 60min) before the next layer of paste can be processed until the desired thickness. When pasting, the glass fiber cloth must be flat, the seams between the glass cloths should be staggered from each other, and try not to overlap at the corners. To strictly control the amount of resin glue in each layer, it is necessary to fully infiltrate the fiber and not excessively. The content of glue is high, the bubbles are not easy to be eliminated, and the curing exotherm is large and the shrinkage rate is large. Low glue content, easy to layer. Then brush the resin on the glass fiber mat, so that the resin is immersed in the glass fiber mat. After the entire layer of fiber mat is impregnated with resin, you need to use a brush to brush on the surface of the fiber to drive all the gas between the resin and the fiber mat, otherwise it will affect the quality and appearance of the FRP product. The next step is to repeat the above steps. Lay a layer of fiberglass felt and a layer of resin. The number of layers of glass fiber mat determines the thickness of the product. The thickness of glass fiber mat generally has specifications such as 0.2mm and 0.4mm. The thickness of gel coat plus the thickness of fiber mat multiplied by the number of fiber mat layers is basically equal to the thickness of the product. One or two more layers of fiber mat can be added at the corner because of strength requirements. In some places where deformation and strength need to be prevented, a layer of fiberglass cloth of high-strength material can be added. There are two ways to prevent waste of brushes. One is to soak the brush in resin after it is used up, and the brush can also be washed with acetone, so that the brush can be reused next time. After the resin and glass fiber are pasted on the mold, the product is cured. The curing time is related to the proportion of the curing agent added to the resin and the temperature. In order to have higher productivity, it is more appropriate to control the curing time within 1 to 2 hours. This requires adding more curing agent, but it will Affecting the quality of the product, the solution is to put it in an oven at about 60℃, which can reduce the proportion of curing agent and increase the curing time. The sculpture product can be demolded after curing in the mold. After demolding, the product needs to be cured naturally for about an hour, which is very helpful for the reduction of the size of the product after trimming. The trimming of glass fiber reinforced plastic products generally draws lines according to the required size, and then cuts the material along the line with an electric cutting machine while leaving a margin of 2~3mm, and then uses electric grinding wheels to polish and correct. At this point, the product is finished.

       Stripping and trimming: sculptures made at room temperature (about 20℃) are generally cured and set in 48 hours, that is, they can be demolded. For a complete FRP sculpture product, the subsequent process after molding is still very necessary. After some sculpture products are demoulded, the surface is a little scratched or the docking is not in place. This requires the use of resins of the same brand to stick and repair, and then polish and correct after curing. If it is a sculpture with high finish requirements, generally use 400#~1200# water sandpaper to polish the surface of the sculpture in turn, and use a polishing machine to polish the surface of the sculpture. Some sculpture edges are matched with other parts, and the thickness needs to be ensured. The excessive thickness should be polished on the back of the product to achieve the required thickness. Many FRP sculpture products need to be embedded with other products by embedding sheet metal parts. To embed these sheet metal parts, first put the product and sheet metal parts into the master (the master is a shelf, the product and the The embedded sheet metal parts can be fixed on the position of the required dimensional relationship on it, and then the sheet metal parts are embedded on the product like a paste product through resin and fiberglass felt. These processes will directly affect the quality of the product.

Source:https://www.up-resin.com/

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