With the development of the automobile industry, the demand for fiber-reinforced thermoplastics has increased significantly, and its manufacturing technology has also entered a period of rapid development.
The D-LFT process has several outstanding advantages:
Integrate batching and molding, save the preparation of prepreg, and greatly save manpower;
The number of times of heating is small, there is no secondary melting and plasticization, saving energy and reducing consumption;
Avoid the impact of the secondary melting and plasticizing process on the resin and long fibers, and do not excessively damage the added fibers. The performance of the resin matrix and fiber length can have a higher retention rate than LFT-G molding, and the average fiber length is higher than that of LFT-G. The molding is 15%-20% higher, with high-quality product performance. Through product and mold design and optimization of process conditions, the mechanical properties of the product can be close to GMT products;
The process and production cycle are shortened, and the production efficiency is improved. The production cost is low. Compared with long-fiber pellets, the product cost can be reduced by about 40%. The basic process principle is: supply thermoplastics to the coating dipping mold through the extruder, then use high-pressure melt to coat the long fibers and drag them to the cutting knife at the end of the dipping mold, and the cutting knife cuts the coating according to the preset length. The long fibers covered in the melt are cut off, and then the melt enters the injection molding machine for injection molding.
In order to expand the application range of fiber-reinforced thermoplastics and make them suitable for automotive exterior parts with high surface quality requirements, during injection, the temperature of the mold surface in contact with the molten material is kept above the glass transition temperature of the matrix resin or even close to the molten material Obviously, it is easy to obtain products with high surface quality.
However, thermoplastic products must be cooled to below the heat distortion temperature for demoulding, and usual mold cooling is still necessary. In order to improve the molding process of fiber reinforced thermoplastics, rapid change of mold cavity surface temperature becomes the key to problem solving. The latest mold induction heating technology meets this rapid changeover requirement.
In order to realize the rapid transformation of the surface temperature of the mold cavity, a solution of mold induction heating is proposed. Using electromagnetic induction technology, the ideal melt rheological conditions can be obtained by rapidly heating the mold surface to a temperature close to the temperature of the injected plastic melt. The resin is at a similar temperature to the mold surface, so it flows easily.
In order to be more widely used in various occasions, in the mold cavity induction heating technology, other technologies are also combined to introduce two types of mold induction heating systems, namely the cage system and the built-in inductor integrated inside the mold . Successful application of induction heating technology to long fiber reinforced thermoplastic (LFT) injection and compression molding tooling to produce large automotive components with Class A surfaces. The patented method used only heats and cools the surface of the mold cavity, and its cycle time is much faster than traditional methods. Turn on the power of the sensor, and it only takes a few seconds to tens of seconds to heat up. The heating depth is only in the surface layer within 0.2mm below the mold surface, and 99.9% of the mold as a whole is not in a heated state.
