Hot runner injection molds are also known as runner free injection molds. The difference between their gating systems and ordinary gating systems is that the plastic in the gating system is always in a molten state during the entire sintering process, and the pressure loss during injection molding is small. It is possible to achieve low-pressure injection molding for multi-point casting, multi-cavity molds, and large plastic parts. In addition, this gating system does not have a gating system for solidification, achieving waste free processing, and eliminating the need for gate removal, It can save manpower and material resources.
Due to the special process of hot runner in the molding process, this type of injection molding method has the following characteristics.
① Save materials, energy, and labor. The pouring system of ordinary injection molded parts accounts for a large proportion of material consumption. The secondary utilization of this batch of condensate is to mix fresh material after crushing, extrusion, and granulation to reshape the plastic part. The existing problem is that it is easy to bring in foreign materials and cause pollution, which reduces the performance of the plastic part in secondary molding. Statistics show that the waste rate of plastic parts mixed with secondary recycling increases by about 5 times, Moreover, the materials in the flow path of thermosetting plastics will become completely waste after solidification and cannot be reused.
Without these runners in the hot runner injection mold, the consumption of this portion of plastic is low for thermosetting plastics; For thermally dominant plastics, the recycling of these aggregates is eliminated, thereby eliminating the need to separate, tablet, extrude, and granulate these aggregates from the plastic, saving the energy consumption and labor required for each process in these tasks. Without a flow path for solidification, a smaller mold opening stroke and a smaller projected area can be selected in mold design. For the same plastic part, a smaller injection molding machine can be selected, which not only reduces equipment costs, but also reduces the heating power of the motor, pump, and material sheet of the injection molding machine,
Energy savings in long-term production are considerable.
② Improve the quality of plastic parts. In a hot runner mold, the plastic in the runner is always in a molten state, reducing the melt flow and facilitating the transfer of pressure into the mold cavity: it can make the pressure distribution in the mold cavity more uniform. Reducing the melt temperature difference; Can avoid or improve fusion lines; It can shorten the pressure holding time, reduce the replenishment stress, and minimize the gate trace. In short, it can improve the internal and external quality of plastic parts.
③ Shorten the molding cycle. The injection molding cycle of plastic parts includes mold closing time, mold filling time, feeding time, cooling and solidification time, and demolding and taking time. Using a hot runner mold, these periods of time can be shortened. Without runner solidification and the need to use a three plate mold (even with a point gate), the required mold opening and closing strokes are reduced. The melt in the runner always remains molten, making it easy to maintain pressure and replenish materials. For thicker plastic parts, smaller gates can be used than normal runners, reducing cooling time. For long-term production in large batches, the reduction in labor hours caused by shortened molding cycles is significant.
④ Material saving, energy saving, and labor saving. Generally speaking, the mold cost of hot runner molds increases by about 10-20%, but this increase can be quickly compensated for by the above economic benefits. However, the structure of hot runner injection mold is very complex; In particular, strict temperature control requirements can easily decompose and scorch plastics, and manufacturing costs are high, making them unsuitable for small batch production.
2023-03-24
2023-03-24
2023-03-24
