How to choose materials for rapid prototyping
Different rapid prototyping methods require the use of materials of different properties that are compatible with the molding process. The classification of the molding materials is closely related to the method of determining the speed and the physical state and chemical properties of the materials.
l According to the physical state of the material can be divided into liquid materials, sheet materials, powder materials, filament materials, etc.
2 According to the chemical properties of materials can be divided into resin materials, paraffin materials, metal materials, ceramic materials and composite materials.
3 Classification by material forming method can be divided into: SLA material, LOM material, SLS material, FDM material, etc.
4 According to the material forming step classification can be divided into: direct molding materials (including reactive polymers, non-reactive polymers, paper, metals, sand, ceramics, etc.), indirect replication materials (including silicone rubber, metal matrix composites) , ceramic composite materials, reaction molding plastics, etc.).
Rapid prototyping process requirements for material properties
The core problem of the rapid prototyping process is to add material to the surface to be formed and to cure it by some means in order to obtain a three-dimensional entity with a certain shape size and function. There are two key parameters: the minimum weight when adding material and the minimum geometric resolution for bond curing. The materials currently widely used in the fields of rapid prototyping and rapid prototyping are shown in Table 4-2. In order to achieve a small addition weight, the material form that these materials can exhibit is nothing more than a liquid state and a powder state, and the method of continuously bonding and curing the continuously added materials is mainly a chain reaction curing of a resin or a plastic, and no chemical reaction. The method of melt-bonding curing and bonding the sheet body with an adhesive, the form of bonding each time can be divided into points, lines, and faces.
Material problems related to the molding process The material mainly affects the shape and size after molding and molding. In order to be able to form, the material must be easily cured and bonded. It must have a certain joint strength after molding. In addition to the small spot laser source in the curing bonding process, the material itself has a small heat affected zone, a clear molding boundary, and sintering or The stress generated by the chemical reaction is small, and it should also be easily penetrated by the laser to ensure the depth of formation. The viscosity of the liquid photosensitive resin should not be too high to ensure the flatness of the layup and reduce the waiting time of Z. The particle size and free density of the solid powder should be suitable. The particle is too small and the precision is not easy to be sintered. If the particle is too small, the sintering depth is shallow. The powder is easy to fly. The material wins should be even and stable.
2 Material problems related to the properties of the molded part The whole body has a small shrinkage deformation during the forming process, and it is easy to realize a small layer thickness to ensure the surface roughness. Molded parts must have sufficient strength and toughness, as well as resistance to moisture and external impact. When used as a mold, they also require suitable thermophysical properties, and the molded parts should be stable during the service life. It is non-toxic and harmless to the human body, and sometimes requires a certain color (or transparency). When using SL molded parts as injection molds, the following materials are required to pass: compressive strength, tensile strength, shear strength, flexural strength, impact toughness, wear resistance, surface hardness, thermal expansion coefficient and thermal conductivity. Wait.
Rapid prototyping process for material technology
In the early stages of RP technology development, the automotive industry and the aerospace industry accounted for nearly half of the RP market. Although the RP market has penetrated into many other fields with the development of RP technology, the demand and renewal of materials make these two industries Market share is still not to be ignored.
The automobile industry is a pillar industry of many advanced industrial countries and a major commodity. In the United States, for example, automotive materials, including metals, plastics and rubber, ceramics and glass, total about 60 million tons of materials, accounting for a large share of material consumption. Automotive materials require low cost, easy molding, long life, high reliability, and easy recycling, reducing environmental pollution, so automotive materials are constantly updated, especially high-strength, low-density materials increase faster. Composite materials, engineering plastics and high-strength steels have increased rapidly, ceramic materials have just started, and advanced composite materials have yet to start. In addition, as the degree of automation of automobiles continues to increase, the variety and quantity of functional materials used in automobiles are also rapidly increasing, such as high-performance magnetic materials, developing smart materials, and the like.
The aviation industry is part of the machinery manufacturing industry and has strict requirements on materials because the working conditions of the aircraft and its engines are very demanding, require long life and need to be used repeatedly, and must be absolutely safe. In order to pursue higher payloads, the materials used require high specific strength and specific stiffness, so the development of the aviation industry depends to a large extent on the advancement of materials. At the same time, the demand for materials in the aviation industry has strongly promoted the development of materials. In the future, the proportion of composite materials will increase dramatically. The effect of composite materials on aircraft weight reduction is very significant. For example, carbon fiber reinforced composite materials can produce 3kg of aluminum per kilogram of carbon fiber composite material, so the prototype of a full composite aircraft has emerged. Due to the development of polymers, the progress of polymer materials is changing with each passing day, especially the realization of molecular composites, so that the specific strength of polymers is
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