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The application of Moldflow software in special injection molding


mpi3.1 in addition to the simulation and analysis of traditional injection molding, it can also simulate and analyze some special injection molding processes, such as co injection molding, injection compression molding, reaction injection molding Microchip packaging (microchi block mineral resources, etc. are still tight), gas assisted injection molding. Among them, gas assisted injection molding will be introduced in a special article, and other injection molding simulation analysis will be discussed below

simulation analysis of CO injection molding

co injection molding refers to a molding method that uses an injection molding machine with two or more injection units to inject different varieties or colors of plastics into the mold at the same time or successively, which can produce composite products of various colors or plastics. MPI/CO injection can simulate the sequential injection molding process. Generally, the injection molding machine used for CO injection molding has two barrels and a common nozzle. The plastic on the surface of the product is injected first. Due to the fountain effect, the plastic melt is sprayed to the mold cavity wall. The temperature of the mold wall is far lower than the solidification temperature of the melt. The melt solidifies rapidly to form an insulating layer, and the new melt flows along the mold wall until it covers the whole mold cavity surface. Then inject the plastic inside the product, and finally inject the surface plastic again. In the process of CO injection molding, there are two process parameters that are difficult to control:

1) the optimal mixing ratio of the two plastics. Theoretically, the internal plastic of products can account for up to 67% of the volume of products, but it is difficult to reach in practice, especially for complex products. In engineering, the internal plastic can reach 30% of the volume of products

2) time control point of injection conversion of two kinds of plastics

due to the unreasonable design of the mold or the improper proportion of the two plastics, it is possible to expose the internal plastic surface, especially the last filled place

MPI/CO injection predicts the distribution of two kinds of injection plastics in the mold cavity according to their characteristics, and gives the best mixing ratio of the two plastics and the control point of injection time. The analysis results include:

1) the volume percentage of any point in the mold cavity at any time during the filling process of the two plastics

2) distribution of two kinds of plastics in the mold cavity

3) thickness change of internal plastic during molding

4) the quality change of any point in the mold cavity at any time during the filling process of the two plastics

5) according to the selected analysis process, the analysis results also include flow analysis results, cooling analysis results, warpage analysis results and stress analysis results

three pressure injection molding simulation analysis

pressure injection molding is simply to first inject the plastic into the mold cavity larger than the size of the product, and then compress the molded part to meet the size requirements of the product. The products produced by this forming method have stable size, small residual stress and small clamping force, and are especially suitable for products with high precision and low residual stress, such as optical parts. In the process of pressure injection molding, injection (including filling and pressure maintaining) and compression can be carried out at the same time, or injection before compression

mpi/injection compression module can help users in the following aspects:

1) minimum compression force

2) minimum injection pressure

3) minimize the shrinkage, deformation and residual stress of the product

the analysis results include:

1) compressive force

2) platen displacement: the platen displacement is the difference between the platen position at the end of molding and the platen position at the beginning of injection. It should be equal to the set platen displacement value (the maximum does not exceed the set value). The final size of the product is equal to the sum of the product design size and the set platen displacement value minus the platen displacement. If the size of the molded part cannot meet the requirements of the product size, the following measures can be taken: reduce the set platen displacement; Reduce the waiting time of pressing plate; Increase the moving speed of the pressing plate; Increase the compression force; Increase injection time, etc

3) moving speed of pressing plate: in the process of compression, before the compression force reaches the preset pressure, the moving speed of pressing plate in each pressure increasing section is the same. When the pressure reaches the preset pressure value, the pressure remains unchanged, but the moving speed may not be constant

4) mold cavity volume: including the volume of sprue. With the beginning of compression, the mold cavity volume continues to decrease

5) according to the selected analysis process, the analysis results also include flow analysis results, cooling analysis results, warpage analysis results and stress analysis results

simulation analysis of four reaction injection molding

reaction injection molding is fair and correct. The use of fixtures is conducive to the smooth progress of the experiment. Two kinds of low molecular weight liquid raw materials with high chemical activity are mixed by impact under high pressure, and then injected into a closed mold to complete polymerization, crosslinking, curing and other chemical reactions and form products. It has the advantages of high material mixing efficiency, energy saving, good product performance and low cost, Used for thermosetting plastic injection molding

reaction injection molding because of the chemical reaction, the mold design and injection molding process become very complex. If the filling speed is too slow, it will lead to short shot. If the filling speed is too fast, it may lead to shrinkage. Improper mold cavity temperature or improper product wall thickness may lead to poor formability or scorched products

mpi/reactive molding module can provide the following help:

1) simulate the flow process, optimize product design and gate position

2) determine the correct injection pressure and clamping force

3) injection pressure at any point in the mold cavity at any time during the filling process

4) temperature change at any point of the mold cavity with time during the filling process

5) judge whether it is short shot

6) predict fusion lines and shrinkage cavities

7) provide more than 50 kinds of reactive injection molding materials

five microchip packaging simulation analysis

microchip packaging uses active resin, which not only plays a protective role, but also improves heat dissipation and conductivity. Mpi/microchip encapsulation module mainly simulates the packaging process and provides the best process, such as mold temperature, filling time, screw speed curve, curing time, as well as packaging form design, guide pin and wire layout. This process is rarely used in the mainland, and this article will not introduce it in detail. Interested readers can read the help of the software

preparation before analysis

the same as flow, cooling and warpage analysis, the above analysis requires the following preparations:

1) model preparation. In addition to microchip packaging can use center plane or surface model, other analysis can only use center plane model

2) lattice mass and flow analysis are the same

3) set the analysis process

4) select materials

5) set gate

6) set process parameters

seven analysis examples

Figure 1 is an example of CO injection molding, figure 2 is an example of pressure injection molding, figure 3 is an example of reaction injection molding, and Figure 4 is an example of microchip packaging

Figure 1 co injection molding analysis requires inlay or mechanical clamping

Figure 2 injection molding analysis

Figure 3 reaction injection molding analysis

Figure 4 microchip packaging analysis

eight concluding remarks

this paper briefly introduces the application of mpi3.1 in CO injection molding, injection molding, reaction injection molding and microchip packaging. Mpi3.1 is a very powerful software package, including almost all injection molding methods. This lecture only plays a role of throwing bricks and attracting jade. To master it skillfully, you also need practical operation, especially combined with actual product analysis

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