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Injection molding technology: Introduction to hot runner technology
- Categories:Company News
- Time of issue:2021-05-25
(Summary description)As an advanced injection molding technology-hot runner technology, the popularization and use in European and American countries can be traced back to the middle of the last century or even earlier. Because hot runners have many advantages, they are developing rapidly abroad. More than 50% of the molds produced by many plastic mold factories use hot runner technology, and some mold factories even reach more than 80%. In China, this technology is in recent years. It took a few years before it was really promoted and applied. With the continuous development of the mold industry, the proportion of hot runners used in plastic molds has gradually increased. But overall it is less than 10%, and the gap is quite huge.
Injection molding technology: Introduction to hot runner technology
(Summary description)As an advanced injection molding technology-hot runner technology, the popularization and use in European and American countries can be traced back to the middle of the last century or even earlier. Because hot runners have many advantages, they are developing rapidly abroad. More than 50% of the molds produced by many plastic mold factories use hot runner technology, and some mold factories even reach more than 80%. In China, this technology is in recent years. It took a few years before it was really promoted and applied. With the continuous development of the mold industry, the proportion of hot runners used in plastic molds has gradually increased. But overall it is less than 10%, and the gap is quite huge.
- Categories:Company News
- Time of issue:2021-05-25 11:10
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1. The history, present and future of hot runner
As an advanced injection molding technology-hot runner technology, the popularization and use in European and American countries can be traced back to the middle of the last century or even earlier. Because hot runners have many advantages, they are developing rapidly abroad. More than 50% of the molds produced by many plastic mold factories use hot runner technology, and some mold factories even reach more than 80%. In China, this technology is in recent years. It took a few years before it was really promoted and applied. With the continuous development of the mold industry, the proportion of hot runners used in plastic molds has gradually increased. But overall it is less than 10%, and the gap is quite huge.
In recent years, the gradual promotion of hot runner technology in China is largely due to the rapid development of my country’s mold exports to European and American companies. In European and American countries, injection molding production has already relied on hot runner technology. It can be said that molds that do not use hot runner technology are now difficult to export, which has also caused many mold manufacturers to change their awareness of hot runner technology.
Since many foreign hot runner systems are expensive, a large number of domestic manufacturers cannot accept them, so some domestic hot runner system components have appeared. This is of great benefit to the promotion of hot runner technology in China. Although hot runner technology has begun to be promoted, some companies have a utilization rate of more than 20%, and generally use simple tip and pass nozzles. A few companies use the world's advanced level of difficult needle valve hot nozzles, but overall the adoption rate of hot runners is less than 10%, which is far from 50 to 80% abroad.
2. The principle of hot runner
The cold runner refers to the part between the mold entrance and the product gate. The plastic is kept flowing in the runner by the injection pressure and its own heat. The runner is part of the molding material, but it is not a product. Therefore, when we design the mold, we must consider both the filling effect and how to save material by shortening and reducing the runner. This is the ideal situation, but it is difficult to achieve the best of both worlds in practical applications.
Hot runner, also known as no runner, means that the plastic in the runner does not solidify after each injection, and there is no need to remove the nozzle in the runner when the plastic product is demolded. Since the plastic in the runner is not solidified, the runner is still unblocked during the next injection.
In short, the hot runner is an extension of the nozzle of the injection molding machine.
3. The advantages of hot runner molds
Hot runner molds are widely used in various industrial developed countries and regions in the world today. This is mainly because the hot runner mold has the following remarkable features:
1. Shorten the molding cycle of parts
Because there is no limit to the cooling time of the runner system, the parts can be ejected in time after they are solidified. Many thin-walled parts produced with hot runner molds can have a molding cycle of less than 5 seconds.
2, save plastic raw materials
There is no cold runner in the pure hot runner mold, so there is no production cost. This is especially significant for applications where plastics are expensive. In fact, the major hot runner manufacturers in the world have all developed rapidly in the era when petroleum and plastic raw materials were expensive in the world. Because hot runner technology is an effective way to reduce material costs.
3. Reduce waste and improve product quality
During the molding process of the hot runner mold, the temperature of the plastic melt is accurately controlled in the runner system.
Plastic can flow into each cavity in a more uniform state, and the result is a part of consistent quality. The gate quality of the parts formed by the hot runner is good, the residual stress after demolding is low, and the deformation of the parts is small. Therefore, many high-quality products on the market are produced by hot runner molds. For example, many plastic parts in the familiar MOTOROLA mobile phones, HP printers, and DELL laptops are made with hot runner molds.
4. Eliminate follow-up processes, which is conducive to production automation.
The parts are finished after being formed by the hot runner mold, and there is no need for trimming gates and recycling and processing cold runners and other processes. Conducive to production automation. Many foreign product manufacturers combine hot runners with automation to greatly improve production efficiency.
5. Expand the application of injection molding process
Many advanced plastic molding processes are developed on the basis of hot runner technology. Such as PET pre-molding production, multi-color co-injection in the mold, multi-material co-injection process, STACKMOLD, etc.
4. Disadvantages of hot runner mold
Although compared with cold runner molds, hot runner molds have many significant advantages, mold users also need to understand the shortcomings of hot runner molds. In summary, there are the following points.
1, mold costs rise
Hot runner components are more expensive, and the cost of hot runner molds may increase significantly. If the output of parts is small, the proportion of mold tool cost is high, which is not economically expensive. For many mold users in developing countries, the high price of hot runner systems is one of the main problems that affect the widespread use of hot runner molds.
2, hot runner mold making process and equipment requirements are high
Hot runner molds require precision machining machinery as a guarantee. The integration and cooperation requirements of the hot runner system and the mold are extremely strict, otherwise there will be many serious problems in the mold production process. For example, poor plastic sealing leads to plastic overflow and damage to the hot runner components to interrupt production, and the poor relative position of the nozzle insert and the gate leads to a serious decline in product quality.
3. Complicated operation and maintenance
Compared with the cold runner mold, the operation and maintenance of the hot runner mold are more complicated. Improper use and operation can easily damage the hot runner parts, making production impossible and causing huge economic losses. For new users of hot runner molds, it takes a long time to accumulate experience.
5. The composition of the hot runner system
Although there are many hot runner manufacturers and multiple hot runner product series in the world, a typical hot runner system consists of the following parts:
1. Hot runner plate (MANIFOLD)
2. Nozzle (NOZZLE)
3. Temperature controller
4. Auxiliary parts
6. ??The main technical key of hot runner application
A successful hot runner mold application project requires multiple links to guarantee. The most important of these are two technical factors. One is the control of plastic temperature, and the other is the control of plastic flow.
1. Plastic temperature control
The control of plastic temperature is extremely important in hot runner mold applications.
Many processing and product quality in the production process
The problem directly stems from the poor temperature control of the hot runner system. For example, the problem of poor quality of product gate when using hot pin gate method for injection molding, problem of valve pin closing difficulty when molding with valve gate method, and inconsistent filling time and quality of parts in multi-cavity molds. If possible, you should try to choose a hot runner system with separate temperature control in multiple areas to increase the flexibility and adaptability of use.
2. Control of plastic flow
Plastics must flow and balance in the hot runner system. The gates should be opened at the same time so that the plastic fills the cavities simultaneously. For FAMILYMOLD whose parts weight differs greatly, the runner size design should be balanced. Otherwise, there will be problems such as insufficient filling and holding pressure for some parts, excessive filling and holding pressure for some parts, excessive flashing and poor quality. The size design of the hot runner runner should be reasonable. The size is too small and the mold filling pressure loss is too large. If the size is too large, the volume of the hot runner is too large, and the plastic stays in the hot runner system for too long, which damages the material properties and causes the parts to fail to meet the requirements of use after molding. There are already CAE softwares such as MOLDCAE that help users to design the best runners in the world.
七. Application range of hot runner mold
1. Types of plastic materials
Hot runner molds have been successfully used to process various plastic materials. Such as PP, PE, PS, ABS, PBT, PA, PSU, PC, POM, LCP, PVC, PET, PMMA, PEI, ABS/PC, etc. Any plastic material that can be processed with cold runner molds can be processed with hot runner molds.
2. Part size and weight
The smallest part made with hot runner mold is less than 0.1g. The largest is more than 30 kilograms. The application is extremely wide and flexible.
3. Industrial field
Hot runner molds are widely used in various industrial sectors such as electronics, automobiles, medical care, daily necessities, toys, packaging, construction, and office equipment.
8. Brief introduction of hot runner mold production in the world
is extremely active in the production of hot runner molds in the more developed countries and regions in the world. The proportion of hot runner molds continues to increase. Many small mold factories with less than 10 employees are engaged in the production of hot runner molds. Generally speaking, North America and Europe have used hot runner technology for a long time, with more experience and higher level. In Asia, apart from Japan, Singapore, South Korea, Taiwan, and Hong Kong are in a leading position. In North America and Europe, although the level of mold manufacturing is higher, the price is higher and the delivery time is longer. In contrast, Asian hot runner mold manufacturers are more competitive in terms of price and delivery time. The hot runner mold in China is still in its infancy, but it is growing rapidly and the proportion is increasing.
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