Application Of Hot Runner Technology For Injection Molds
1. Differences in mold structure
In the molding of oversized plastic products, only the hot runner can be used to balance the plastic flow. For example, in the production of automotive interior linings, appliance housings and other components, more than the need to simultaneously enter the glue or chronologically into the glue, at this time, the hot runner is required to successfully complete this step. In addition, when the side feed is offset from the center of the injection molding machine, the hot runner feeding method can make the mold structure simple, and at the same time make the molding easier, speed up the molding speed, reduce the molding time, and produce no material.
Generally speaking, when the injection is performed by the three-plate method, the heavy master template needs to slide on the guide post, and even if the new mold is difficult to withstand the heavy load caused by the sliding for a long time, the life of the mold is not long. Further, in this manner, the amount of movement of the stencil to take out the flow material from the mold each time it is ejected is greater than the amount of stencil movement required to take out the molded product from the mold.
Therefore, hot runners are usually used when encountering the following conditions:
(1) It is necessary to use a long vertical flow path for the ejection of the side.
(2) In order to avoid problems caused by too long material heads.
(3) Forming some large products that allow eccentricity.
(4) In the use mode of the three-plate mold, the mother template needs to be moved to take out the material head. If the hot runner molding method is used, the mold opening motion can shorten the moving distance required to remove the material. Therefore, the three-plate mold method requires a large molding machine to produce a cold runner, and a small molding machine can be used after the hot runner is used.
(5) For materials with characteristics such as high viscosity, low viscosity or high molding temperature, the hot runner system can solve the problems of difficult molding. For example, in the processing of metal powder, ceramic powder, plastic magnet, plastic bearing and thermoplastic rubber injection molding.
2. Save plastic
1) With the traditional cold runner, there will be a cold head, resulting in additional costs. As a simple example, if the cold head accounts for 68% of the scrap rate (in the case of manufacturing, 1kg of material can only produce 320g of product, while the remaining 680g is a cold head), although the cold head is still recyclable, Due to the influence of human factors and the mixing ratio of recycled materials, in order to maintain normal operation, some cold heads must be accumulated, thus causing the retention of funds.
(2) The hot runner can be used in the field of high speed injection molding. High-speed injection molding not only improves the efficiency of molding, but is also necessary for controlling the wall thickness of products such as cups and containers.
(3) Applied in a laminated mold. For thin-walled and large-volume products, such as CD casings, with a 15% increase in clamping force, an 80% increase in throughput can be achieved over the same injection time.
3. Environmental protection and efficiency of hot runners
Since the hot runner does not produce “garbage”, there is no problem of handling “garbage”. “Garbage” means waste of resources, and the hot runner system is a low-carbon product that does not have environmentally harmful factors.
Due to the wide variety of plastics and often different color, the material accumulated in the injection molding process must be classified, dehumidified, dried and sealed. At the same time, the noise generated by the pulverization will also have an adverse effect on the environment.
In summary, the application of the hot runner to the three-plate mold of the injection mold has the following advantages:
(1) The material head is easy to take out, and the stroke of the material removal head can be reduced;
(2) At the time of injection, the plastic flow is relatively average, and the operating conditions of each injection point can be separately controlled to make plastic injection easier;
(3) Savings on plastic materials and labor costs.