1. People's technical quality is very important
Hand pasted fiberglass products and fiberglass are "emotional products". The same materials, the same environment, because of the different quality of people, the products produced are different. Therefore, in the operation process of making FRP mold, we should concentrate on every thought at every moment, and take every operation process seriously, including the characteristics of materials, the role and data between materials (resin reaction basis, fiber's Classification, mechanics of product structure) has a comprehensive understanding of the concept.
2. Material selection is the key
According to the process requirements of production products, in order to meet the needs of the process, choose appropriate materials to make molds, such as RTM, acrylic blister, pouring, hand paste and other materials have different requirements, especially for the auxiliary comparison which is ignored by the upper level and the grass-roots level for a long time, which plays an important role in the quality of glass steel molds, the quality of products and the cost of products for the survival of enterprises Effect.
(1) Gel coat - pay attention to the heat resistance, luster and crack resistance of the mould. Vinyl ester resin is the mainstream.
(2) Surface layer - pay attention to heat resistance and crack resistance. The resin uses surface felt as reinforcement material to reduce the cloth lines on the surface of the mold. The resin of the bright and dark colors is usually vinyl ester resin.
(3) Middle layer - pay attention to the strength, the mechanical distribution of the fiber, the implementation of prestressing the fiber, usually using mold resin or vinyl ester resin or isophthalic acid resin.
(4) Backing layer - pay attention to the protection of strength, water resistance and weather resistance.
(5) Reinforcement layer - pay attention to strain and deformation. The water-resistant plywood is pressed on the back to make it resistant to impact and prevent deformation. However, when it is used for a long time, the surface leveling of the mold often goes bad, which may be caused by the peeling between the FRP layer and the plywood and the rigid fatigue of the plywood. Therefore, the glass fiber fabric of three-dimensional hollow structure can be used instead of plywood, which can solve the original shortage; in addition, 3D steel structure grid can also be used as reinforcement and reinforcement, which can greatly improve the use efficiency of the mold.
New fillers, such as nano calcium carbonate and fibrous wollastonite powder, are used to enhance the overall stability of the mold, especially where they are connected with wood, steel frame and so on.
In terms of fiber composition, the mainstream is the combination of glass fiber felt and plain cloth. The price of aramid and carbon fiber is relatively high, but due to the very good effect in crack resistance and stiffness improvement, it can also be properly selected due to the special needs of the mold.
3. Equipment and tools
It is believed that making FRP mold is a simple process of manual operation, and the main tool of resin distribution is the rough sweep. If the workers use it properly, there will be less small bubbles produced by the broom. If it is not used well, the broom is a tool for making small bubbles. Therefore, we should select the broom (the hair should be neat and the hair root should be straight) before operation.
Roller is the main tool for foam removal. It is not only responsible for discharging bubbles, but also for pressing the fibers tightly. It is also responsible for rolling out the resins that meet the requirements of fiber immersion, so that the smaller the difference between the resin ratio of the mold and the fiber is, the better. This is a very important measure to improve the quality of the FRP mold and the FRP products. On the contrary, the roller shape design that is bought on the market now is in the form of horizontal bars It has become a so-called bubble harvester, which can't discharge bubbles or roll excess resin out, let alone reduce the ratio of resin to fiber, so where does the strength of FRP mold come from? Where does quality come from?
Implementation process of forming process
The FRP mold we need to do well must meet the requirements of product size, good straightness, high strength and good mechanical properties, all through the implementation of reasonable process and operation technology. The relationship among resin, fiber and auxiliary materials of the FRP mold is very complex, and there are many appearance factors such as temperature, relative humidity, completion of operation time, etc Therefore, we need to take some necessary technological measures in the operation process.
Take the necessary demoulding treatment on the master mold, calculate the actual area of the upper gel coat, equip the auxiliary materials according to the quantity, pay attention to the standard operation, and mix the gel coat slowly, or there will be more bubbles, which will affect the quality and effect of the gel coat. For spraying and hand coating, the first layer does not need to be too thick, so that the bubbles in the gel coat will be easily discharged, but it needs to be painted evenly, so that when the first layer of gel coat begins to thicken, the second layer can be applied. At this time, the thickness of the second layer of gel coat should be about 0.55mm ~ 0.6mm in total, and we can also use the gel coat ruler to measure whether it meets the required thickness. When coating the wall, the action direction is from the bottom to the top, try not to brush horizontally, so as to reduce a lot of glue flow. After the two layers of gel coat are basically solidified, a layer of gel coat shall be added. At this time, the coating of the whole gel coat is completed. The surface layer and reinforcement layer can be laid with just gel.
In order to make the quality of FRP mold achieve the expected best performance effect, we use some necessary methods in the laying process to control the whole FRP mold to minimize the deformation and shrinkage, and keep the mechanical properties in the best state. Relatively speaking, the overall comprehensive cost will be reduced.
4. Strict implementation process of forming process
The FRP mold we need to do well must meet the requirements of product size, good straightness, high strength and good mechanical properties, all through the implementation of reasonable process and operation technology. The relationship among resin, fiber and auxiliary materials of the FRP mold is very complex, and there are many appearance factors such as temperature, relative humidity, completion of operation time, etc Therefore, we need to take some necessary technological measures in the operation process.
Take the necessary demoulding treatment on the master mold, calculate the actual area of the upper gel coat, equip the auxiliary materials according to the quantity, pay attention to the standard operation, and mix the gel coat slowly, or there will be more bubbles, which will affect the quality and effect of the gel coat. For spraying and hand coating, the first layer does not need to be too thick, so that the bubbles in the gel coat will be easily discharged, but it needs to be painted evenly, so that when the first layer of gel coat begins to thicken, the second layer can be applied. At this time, the thickness of the second layer of gel coat should be about 0.55mm ~ 0.6mm in total, and we can also use the gel coat ruler to measure whether it meets the required thickness. When coating the wall, the action direction is from the bottom to the top, try not to brush horizontally, so as to reduce a lot of glue flow. After the two layers of gel coat are basically solidified, a layer of gel coat shall be added. At this time, the coating of the whole gel coat is completed. The surface layer and reinforcement layer can be laid with just gel.
In order to make the quality of FRP mold achieve the expected best performance effect, we use some necessary methods in the laying process to control the whole FRP mold to minimize the deformation and shrinkage, and keep the mechanical properties in the best state. Relatively speaking, the overall comprehensive cost will be reduced.
4.1 intermittent method
The intermittent method is to use the time difference to minimize the deformation and shrinkage of the resin. First, a layer of surface felt or short cut felt can be made. Because only one layer of glass fiber is made, the resin consumption is also small, and the overall shrinkage and deformation is very small, so that the layer has enough curing time to shape, and then a layer of fiber can be made. Because the first layer is solidified in the front and the second layer is solidified in the stable shape of the previous layer, the deformation and shrinkage will be greatly reduced. (Note: after each curing, it is necessary to roughen and dewaxing the surface of FRP, otherwise delamination between layers will occur, affecting its strength and quality. ）After that, the number of intermediate layers can be increased by 3 to 5 layers each time until the FRP mold is laid to the expected strength requirements.
4.2 RM method
In the process of laying the middle layer, we adopt the technology of one felt and one cloth, that is, short cutting felt, and square cloth overlapping. When we lay two layers of square cloth, the shearing force between layers is very poor: when we lay and cut the short cutting felt alone, its fiber line is short, the force direction performance is not centralized, and the adhesive content is large. In view of their respective advantages and disadvantages, RM method is used to promote the infiltration between resin fibers and improve the inter layer torque of fiber cloth, so as to get the best effect.
4.3 45 ° paving method
The bending force, jacking force and torsion of fiberglass are all very poor. It has only a strong tensile force. And the force direction of fiberglass cloth is only longitude and latitude, that is to say, the force direction is only four sides, and after 45 ° laying, eight sides are obtained by adding four directions, which is one of them. Second, when there is a right angle in the product or mold structure, one of the fibers at the right angle is 90 ° bending force and the other is torsion force, which are in the worst stress condition. Therefore, 45 ° laying method is adopted at the right angle of the product or mold structure to make two fibers at the right angle form 120 °. At this time, we add light prestress in the operation process to make the fiber The force is pulled more tightly, and the stress on the product structure is exerted better.
Due to the relationship between enterprise benefits, many manufacturers are eager to demould after the mold is laid and solidified for a short time, and then grind it with water abrasive paper, and put it into production immediately after polishing. At this time, the FRP mold is in the incomplete state of curing, the FRP mold has not yet had the best strength, the resin has not yet fully reacted, the stress generated by the shrinkage deformation of the FRP mold material has not been released, and the heat generated in the production of products has an impact on it, so that the problems of the mold in terms of strength and durability, surface finish, deformation and other aspects will gradually surface After exposure, the rubber coat, the appearance of the surface cloth lines and even the cracking of the rubber coat, the white internal injury of the layer, and the overall warpage and deformation of the mold make it impossible to use. Therefore, the post curing treatment of the FRP mold is very important. After a constant temperature of 80 ℃ for 3-4 hours, the stress of the shrinkage and deformation of the FRP mold at different angles on the structure can be released in a buffer way, and the resin can be obtained at a constant temperature of 80 ℃ It can be demoulded only when the reaction is complete and it is in the best condition.
Besides more humanization, the key factor of mold polishing is the quality of water abrasive paper in water grinding process. Good terrazzo paper can achieve twice the result with half the effort (now we use terrazzo paper in addition to MT, there are Japanese, England, Italy, the United States, and the most common one is South Korean Eagle ball sandpaper). At the beginning of water grinding process, 600-800 × should be used. If the mold is too rough, it should be used first. Because the beginning of the use of too thick water sanding paper, its sand marks are very thick. The final water grinding time will be much longer. Remove the last sand mark every time. No water sand mark can be seen until 1500 ~ 2000 × time. This is a very patient and meticulous process. Polishing can only be started after this process can meet the process requirements. Use No. 1 polishing water, all coated on the mold to be polished. In the process of polishing with wool polishing disc, we should pay attention to the turning problem of polishing disc. According to the turning of polishing disc, we should bring in polishing water to achieve the polishing effect, and can't make polishing disc throw out polishing water, so it won't have the polishing effect, which is labor-consuming, time-consuming and material consuming. After the completion of this process, the mold basically appears bright surface. We use No.3 polishing water again. We also need to pay attention to the above problems, because No.3 polishing water has its own sealing agent