Small knowledge on filling for injection molding in plastic mold factories
Injection molding is a step that many molds need to go through, which is divided into four stages, and filling is the first stage. This does not mean that filling is more important in the injection molding process, as no one can do without each of the four stages. The following mainly discusses filling.
Firstly, we need to understand that filling is the first step in injection molding and needs to start working at the beginning of mold closure. Generally, filling to around 95% is sufficient. Another theory is that the shorter the filling time, the higher the efficiency of molding. However, the injection molding time
It is influenced by many factors. And filling is also divided into high-speed filling and low-speed filling, the specific differences can be seen in the following text.
The shear rate is higher during high-speed filling, and due to the thinning effect of shear, the viscosity of the plastic decreases, reducing the overall flow resistance; The local viscous heating effect can also cause the thickness of the cured layer to become thinner. Therefore, in the flow control phase, the filling behavior often depends on the need to fill
The size of the volume. In the flow control stage, due to high-speed filling, the shear thinning effect of the melt is often significant, and the cooling effect of the thin wall is not obvious, so the efficiency of the rate is the main factor.
When filling with low thermal conductivity, reducing shear rate, relatively high local viscosity, and high flow resistance. Due to the slow rate of thermoplastic replenishment and slow flow, the heat conduction effect is very good, quickly taking away heat and cooling the mold wall. Add a small amount of viscous heating phenomenon,
A thicker solidification layer further increases the flow resistance in the thin-walled portion. Usually, the strength of the weld seam in the high-temperature zone is better because the activity of the polymer is more active at high temperatures, and it can entangle with each other. In addition, the melt temperature in the high-temperature zone is similar, so the thermal properties are also similar, and it can also increase the strength of the weld seam. If it is in the low-temperature zone, the strength will deteriorate.