1,How the Hot Runner Works?
The cold runner of a plastic injection mold refers to the section between the mold inlet and the gate. The molten plastic maintains its fluidity inside the runner by virtue of the injection pressure and its own heat. However, as a part of the molding material, the runner is not a product. As a result, when designing a mold, we need to consider not only the filling effects, but also the material-saving effect produced by shortening or downsizing the runner; but in actuality, it is not easy for us to have the best of both worlds.this is why we need hot runner mold
Also known as the runner-less system, the hot runner is a system in which the molten plastic is not solidified after each injection, so when releasing the plastic part, the gate inside the runner does not have to be released. Since the plastic inside the runner is not solidified, the runner still stays unblocked when the next injection takes place.
2,The advantage of Hot Runner Molds compare to cold runner molds
Why has the hot runner system been developed? What benefits can the hot runner system bring us? Engineers familiar with the plastic injection molding process all know that the traditional injection molding is always associated with the following disadvantages:
Hard to fill; b. thin-walled large size parts easy to deform; c. material waste in the runner; d. inconsistent plastic part quality when using a multi-cavity mold, and so forth.
The appearance of the hot runner system has provided an almost perfect solution for these problems. Generally speaking, the hot runner system offers the following benefits:
■ Shorter cycle time
As it is not limited by the runner cooling time, the plastic part can be ejected in a timely manner after being molded and solidified. For the production of thin-walled small parts, the molding cycle can be kept within 5s.
■ Material saving
In a complete hot runner mold, material waste will not occur thanks to the absence of a cold runner. This is of a greater significance to the application projects of the more costly plastic materials. As a matter of fact, global major hot runner manufacturers had witnessed leap forward development during the years when world crude oil and raw plastic materials were expensive. This is because the hot runner technology is an effective way to reduce waste materials and thus lower raw material costs.
■ Reducing defective products, and improving product quality
The temperature of the molten plastic inside the runner system can be accurately controlled during the hot runner injection molding process, so that the plastic is able to flow into each cavity in a more consistent manner, thus guaranteeing consistent quality products. The hot runner gate is of a higher quality, so after mold release, the part produced will have a smaller internal stress, leading to a smaller part deformation. Therefore, many high quality products in the market are all produced with the hot runner mold.
■ Eliminating following steps, helpful for production automation
After being molded with a hot runner mold, the part will be the final product, so there will be no follow-up steps like gate trimming, recycling and runner cooling, thus helpful for production automation. Many manufacturers from both home and abroad have combined the hot runner system with automation, so as to greatly improve production efficiency.
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