Differences Between Injection Molding Hot and Cold Runners

How to distinguish?

If the hot runner system is in the mold, then it belongs to hot runner mold, and if not, it is a  cold runner mold.

Hot runner mold has following remarkable features:

1. Shorten molding cycle

Without the limitation of the cooling time of the sprue system, products can be ejected immediately after solidification. Many thin-walled parts produced with hot runner mold have a molding cycle of less than 5 seconds.

2. Saving raw materials

In the pure hot runner mold, because there is not cold runner, so there is no waste material. This advantage is especially significant for the projects that plastic are expensive. In fact, the main hot runner manufacturers in the world have a rapid development in years when oil and plastic raw material are expensive. Because hot runner technology is an effective way to reduce material costs.

3. Reduce waste and improve product quality

During the hot runner mold forming process, the plastic melt temperature can be controlled accurately in the runner system. Plastics can flow into the cavities in a more consistent state, so that can have a sonsistent quality parts. The hot runner forming parts have good gate quality,low residual stress after demolding, and have small part deformation. Therefore, many high quality products on the market are produced by hot runner molds. Such as : phones, HP printers, and Dell laptops.

4. Eliminate the subsequent processes and help to achieve automatic production. The material formed by hot runner mold then become a finished product, and there is no need to trim the gate or recycle the processed cold runner. Many manufacturers have combined hot runners with automation to increase production efficiency.

5. Expand the application of injection molding technology.

Many advanced plastic molding technology have been developed based on hot runner technology. Such as PET preforming, multi-color co-injection, variety materials co-injection process, STACK MOLD.

Although hot runner molds have many significant advantages compared to cold runner molds, we also need to know some shortcomings of hot runner mold.

1. Mold cost is higher.

Hot runner components are much more expensive, so hot runner mold cost will be higher accordingly. It is not a good choice if the quantity is small. In many developing countries, the high cost of hot runner systems is one of the main reasons affecting the widespread of hold runner molds.

2. Hot runner mold production have high equipment requirement

Precision machinery is an ensurance for hot runner mold. The integration and cooperation requirement between hot runner system and mold are extremely strict, otherwise the mold will occur many serious problems in the production process. Such as the plastic sealing performance is not good, which will cause plastic overflows and damages the hot runner components; the relative position of nozzle insert and the gate is not good, resulting in serious quality problems.

3. Complicated operation and maintenance

Hold runner mold operation and maintenance is complicated compared to cold runner mold. If operate improperly, it will damage hot runner parts easily, can’t continue production successfully and cause huge economic losses. For new users of hot runner molds, it will take a long tile to accumulate experience.