Introduction: In life, we often see some beautiful crafts. Those exquisite, seemingly made of glass crafts, looks so exquisite, we often wonder, what kind of a process, to create such beautiful crafts?
Fiberglass reinforced plastic (FRP) process in life is very wide range of applications, from small to our usual common crafts, to hundreds of layers of skyscraper construction, and even aerospace and aviation, are inseparable from the FRP this important production process.
Fiberglass reinforced plastic production process is more, there are a variety of methods such as hand lay-up molding, extrusion molding, laminating molding, winding molding. Among them, hand lay-up molding, extrusion molding, winding molding is the most important FRP production process. The next step is to introduce you to these major production processes.
In our life, we often see some simple FRP products such as glass fiber reinforced plastic crafts are mainly made by the process of hand lay-up molding. Hand lay-up molding is the earliest and most widely used FRP molding process, its principle is to add curing agent to the liquid resin, the mold will be glass fiber and resin mixture bonded together to enhance the strength of the glass fiber, made of glass fiber reinforced plastic. The principle of this process is simple, the equipment as well as the technical requirements are very low, suitable for small enterprises small batch production, in addition, the hand lay-up molding process is not subject to the limitations of the shape and type, suitable for multi-species mass production. Therefore, it is the most common FRP molding process.
Extrusion molding process is the modern society to produce large quantities of glass fiber reinforced plastic main process. The extrusion here mainly relies on the machine using the mold for extrusion, it is the liquid glass into the mold of the machine, through the machine extrusion, so that the shape. This process produces fast production speed, and the FRP produced is of high quality and strength, which is suitable to be used as a building material. And because it is a large machine production, so suitable for mass production, so we often see the life of the building exterior body of the glass fiber reinforced plastic is often produced by this process. But this extrusion process also has a very shortcomings, that is, it produces a single product, and need to use a lot of big machines and equipment, such as dip glue machine, press machine and other large equipment.
Process classification:
The material properties of fiber-reinforced materials, resulting in the following basic molding process: hand-paste molding process, pultrusion molding process, winding molding process, molding process.
Hand lay-up molding
1. Principle of hand lay-up molding
Hand lay-up molding, also known as contact molding, is the earliest and most commonly used molding method in the production of resin matrix composites. Hand lay-up molding process is to add a curing agent resin mixture as a matrix, glass fiber and its fabrics as a reinforcing material, coated with a release agent on the mold by hand lay-up combination, so that the two are bonded together, manufacturing glass fiber reinforced plastic products of a process method. The base resin usually adopts unsaturated polyester resin or epoxy resin, and the reinforcing material usually adopts alkali-free or medium alkali glass fiber and its fabric. In the hand paste molding process, the use of machinery and equipment is less, it is suitable for multi-species, small batch production, and is not subject to the limitations of the product type and shape.
2. Molding process
The process of hand-paste molding process is: first cleaned up or after surface treatment of the mold mold molding surface coated with release agent, to be fully dry and good, will be added with curing agent (initiator), accelerator, pigment paste and other additives and mixing of the gelcoat or resin blend, brush in the mold mold molding surface, followed by the laying of the cut sheet on it. Subsequently laid on the cut glass cloth (felt) and other reinforcing materials, and pay attention to soak the resin, remove air bubbles. Repeat the above laying operation until the design thickness is reached, and then curing and demolding.
3. Molding equipment
The hand-laid molding process uses less equipment, making the model of the equipment has a woodworking lathe, woodworking planer, woodworking circular saws; demolding will generally use the air compressor, lifting equipment and so on.
Molding
1. Principle of the molding method
Thermoset molding is a certain amount of molded material added to the preheated mold, curing and molding of plastic products by heating and pressurization method. The basic process is: a certain amount of pre-treated molded material into the preheated mold, applying high pressure to make the molded material to fill the mold cavity. In a certain pressure and temperature so that the molded material gradually cured, and then the products from the mold, and then the necessary auxiliary processing that is the product.
2. Molding process
Molding process is mainly divided into two stages of preparation and pressing.
3. Molding equipment
(1) dip machine
The main equipment for the preparation of adhesive tape is the dip machine, which consists of several parts such as cloth feeder, heat treatment furnace, dip tank, drying box, and hauling roller. According to the heat treatment furnace and drying box placed in the position, can be divided into horizontal dip glue machine and vertical dip glue machine two kinds.
(2) prepreg unit
The equipment used in this method are cutting machine, kneading machine and tearing machine. Commonly used types of cutters are punch type, wheel blade type, three-roller type and single rotating knife roller type. The role of the kneader is to fully mix the resin system with the fiber system. The mixing paddles are generally of Z-paddle type construction. In the kneading process mainly control the kneading time and the viscosity of the resin system, the two main parameters, sometimes in the mixing chamber structure is equipped with hot and cold water jacket, in order to achieve the control of the mixing temperature. The longer the mixing time, the greater the loss of fiber strength, in some resin systems, too long a kneading time can also lead to significant thermal effects. Mixing time is too short, the resin and fiber mixing is not uniform. Resin viscosity control is not appropriate, also affects the uniformity of the resin on the fiber infiltration and penetration rate, but also on the fiber strength to bring some impact. The main role of the tearing machine is to fluff the doughy material after kneading.
The tearing machine mainly consists of feeding rollers and a pair of tearing rollers, which will tear the incoming mass by the reverse movement of the tearing rollers.
(3) Sheet Molding Compound (SMC) unit
A complete SMC unit consists of 7 main parts such as frame, conveying system, PE film supplying device, scraper, fiberglass cutter, impregnation and compaction device, rewinding device, etc. and 3 main parts such as fiberglass yarn holder, resin paste preparation and feeding system, static eliminator, etc. The system consists of 3 necessary auxiliary systems, such as static electricity eliminator.
(4) press
The press is the main equipment for molding. The role of the press is to provide the molding pressure required and open the mold to take out the products required to take off the mold force, now most of the use of hydraulic presses.
Wrap-around molding
1. Principle of wrap-around molding
Fiber wrap-around molding is one of the main manufacturing processes for resin matrix composites. It is a kind of composite material molding method that under the condition of controlling tension and predetermined line shape, applying special winding equipment to continuously, uniformly and regularly wind continuous fibers or cloth tapes impregnated with resin adhesive on the core mold or inner liner, and then curing them under a certain temperature to make the products of a certain shape.
2. Molding equipment
Fiber winding machine is the main equipment of fiber winding technology, the design and performance of fiber winding products should be realized through the winding machine. According to the form of control, the winding machine can be divided into mechanical winding machine, digital control winding machine, microcomputer control winding machine and computer numerical control winding machine, which is actually the four stages of the development of the winding machine. At present, the most commonly used machines are mechanical and computer numerical control winding machines. Fiber winding machine is the main equipment of fiber winding process, which usually consists of several parts such as machine body, transmission system and control system. The auxiliary equipments include glue dipping device, tension measurement and control system, yarn frame, mandrel heater, pre-soaking yarn heater and curing equipment.
Pultrusion
1. Pultrusion principle
Pultrusion molding process is a continuous traction through the hauling device, so that the yarn frame of untwisted fiberglass roving, felts and other reinforcing materials by the adhesive impregnation, through the heated mold with a fixed cross-section of the shape of the mold, then After passing through a heated mold with a fixed cross-sectional shape, it is cured and formed in the mold, and an automated production process that achieves continuous discharge from the mold is realized.
For the fixed cross-section size of the glass fiber reinforced plastic products, pultrusion process has obvious superiority. First of all, because the pultrusion process is an automated continuous production process, compared with other glass fiber reinforced plastic production process, pultrusion process has the highest production efficiency; Secondly, pultruded products of raw material utilization is also the highest, generally can be more than 95%. In addition, pultruded products have lower cost, excellent performance, stable quality and beautiful appearance. As pultrusion process has these advantages, its products can replace metal, plastic, wood, ceramics and other products, widely used in chemical industry, petroleum, construction, electricity, transportation, municipal engineering and other fields.
2. Molding process
Reinforcement materials (glass fiber untwisted roving, glass fiber continuous mat and glass fiber surface mats, etc.) in the pultrusion equipment under the action of traction, in the impregnation tank fully impregnated with glue, by a series of preform templates reasonably oriented to get the initial shape, and finally into the heated metal mold, mold reaction curing under high temperature. Finally, it enters into the heated metal mold, which reacts and cures under the action of high temperature of the mold, so that continuous, smooth surface, stable size and very high strength FRP profiles can be obtained.
3. Molding equipment
To realize the pultrusion process equipment is mainly pultruder, pultruder can be roughly divided into horizontal and vertical two types. In general, the horizontal pultrusion machine structure is relatively simple, easy to operate, there is no special requirements for the structure of the production plant. And horizontal pultruder can be used in a variety of curing and molding methods (such as hot mold method, high-frequency heating curing, etc.), so it is more in the pultrusion industry. Vertical pultruder processes arranged along the vertical direction, mainly for the manufacture of hollow profiles, this is due to the production of hollow profiles when the mandrel can only be supported at one end, the other end of the free unsupported end, so the vertical pultruder will not be due to the mandrel cantilevered sagging caused by the pultruded products wall thickness is not uniform; this pultruder due to the limitations of the larger, single-product production, has no longer in use. Whether horizontal or vertical pultrusion machine, they are mainly by the yarn feeding device, impregnation device, molding and curing device, hauling device, cutting device and other five parts, they correspond to the process are row yarn, impregnation, into the mold and curing, hauling, cutting.
Another commonly used FRP production process in life is the winding molding production process. It requires the use of special winding equipment, the liquid resin and reinforcement, etc. will be placed on the rotating inner heart of the winding equipment, and then put the glass fiber into the winding equipment. When the machine is turned on, the resin mixture on the inner core is gradually wrapped around the fiberglass as it rotates, and after winding and extruding, a very strong FRP is produced. This is a new technology to produce the process, its prospects are still very big.
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