Current situation of hot runner in China

As an advanced injection molding technology, hot runner technology can be traced back to the middle of last century or even earlier in Europe and America. As early as194065438+February, E.R.Knowles obtained the patent of hot runner technology. In China, the real popularization and application of this technology is only in recent years.

With the popularization and application of hot runner technology, the proportion of hot runner mold in plastic mold will gradually increase. Due to the above advantages of hot runner technology, the application of hot runner technology has developed rapidly abroad. More than 50% or even 80% of the molds produced by many plastic mold factories use hot runner technology, and the effect is very obvious. Hot runner is also used for production in China, but the total amount is less than 10%, which is quite huge, which means that this industry has considerable market space.

The gradual popularization of hot runner technology in China is largely due to the rapid development of China mold export companies in Europe and America. In European and American countries, injection molding production has relied heavily on hot runner technology. It can be said that it is difficult to export molds that basically do not use hot runner technology, which also makes many mold manufacturers change their understanding of hot runner technology. However, because many imported hot runner systems are expensive, many domestic manufacturers can't accept them, so some domestic commercial hot runner system components appear. This is of great benefit to the popularization of hot runner technology in China. However, although the hot runner technology has been popularized, some factories have adopted more than 20% of internally heated or externally heated hot runner devices, and a few units have adopted needle valve hot runner devices with world advanced level, but the overall hot runner adoption rate is less than 10%, which is far from enough compared with the foreign level of 50-80%.

In recent years, world-famous hot runner technology suppliers have entered the China market in various forms, or set up production bases, or find agents, or set up offices or subsidiaries. It should be said that this trend has played a great role in the rapid upgrading of technology in China mold industry. In this trend, there is no doubt that Korean companies with advantages are the first to start work, and Korean brands such as Yudo (Liudao) and SINO(R) (Xianrui) have considerable influence in China; In addition, Synventive, headquartered in the Netherlands, and Mold Masters, headquartered in Canada, will set up factories in Suzhou and Kunshan respectively. Haschi, a North American injection molding giant, has been committed to the popularization of hot runner technology in China for many years, and its wholly-owned Asian operation center-Haschi Shanghai Technology Center also has strong hot runner supply capacity; At the same time, a large number of emerging private enterprises in China have also recognized the unlimited business opportunities in this field, and set up hot runner production enterprises in succession, which is of great significance for reducing the use cost and popularizing the hot runner technology. However, on the whole, most of the technologies provided by local enterprises in China are still in the primary stage, and the emergence of problems such as small choice space, unstable quality and short maintenance cycle will often affect the trust of downstream enterprises in their products.

The wide application of hot runner technology is a great change in plastic molds. In injection molding, it has many incomparable advantages. It can be said that with the further development and maturity of its technology and the reduction of manufacturing cost, hot runner technology will show its great advantages more and more. It is the key to develop hot runner molds to formulate national standards for hot runner parts, actively produce low-cost and high-quality parts and popularize hot runner technology.

Hot runner system is a complex technology in the field of injection molding. Mold designers and mold users need to consider and pay attention to many problems when purchasing hot runner systems. When designing and manufacturing hot runner molds, mold manufacturing companies do not simply buy hot runner systems from hot runner suppliers and install them on the molds. In fact, from the conceptual design stage of the hot runner mold, to the actual manufacturing process of the mold, and then to the final use of the mold, there are many meticulous and close technical and commercial coordination and cooperation between the mold manufacturing company and the hot runner supplier. Therefore, mold manufacturing companies and mold users should choose good hot runner suppliers. When selecting hot runner suppliers, we should focus on two basic aspects, one is the variety, quantity and quality of hot runner components produced by hot runner suppliers, and the other is the technical support and after-sales service of hot runner suppliers in the area where mold users are located.

1. Variety, quantity and quality of hot runner parts

The hot runner system includes hot tip, gate and valve.

There are three types of valve aggregation. In fact, each type can be subdivided into many product lines. For example, the cross-sectional diameter of the flow channel in the hot tip nozzle can often range from 4 mm to 12 mm, and the nozzle is also made into different size product series. There are also many variants of nozzle gate inserts to meet different application requirements. Therefore, the more products hot runner suppliers want to choose, the better. In this way, users can have greater selectivity for hot runner parts, and the types, sizes, weights and application ranges of plastic parts produced by hot runners are wider, which is more conducive to optimizing injection molding production technology and improving product quality.

When plastic products are processed by injection molding, the hot runner system and hot runner mold bear high temperature and high pressure dynamic loads.

Work. There are many factors leading to the failure of hot runner system components. Injection molding is mainly used for mass production of plastic parts. Once there is any shutdown, the economic loss will be very serious. Therefore, the quality and reliability of the hot runner system are very important. Customers should thoroughly investigate the quality and application history of hot runner components produced by hot runner suppliers. Some excellent hot runner manufacturers have passed the ISO quality standard certification of international organizations.

2. Technical support and after-sales service

When users use hot runner molds, they should not only choose a reliable hot runner system, but also consider whether they can get timely and effective technical support and after-sales service when there are any problems in the hot runner. Many hot runner suppliers have strong technical support and service networks in the countries and regions where their company headquarters are located, and are equipped with full-time service personnel, who can visit customers and troubleshoot at any time. However, in other countries and regions far away from their company headquarters, these manufacturers often only set up some offices dedicated to the sales of hot runner products. Technical support is relatively inferior. Users should pay attention to this factor. Users will involve many specific technical links when purchasing hot runner systems. If users have good technical knowledge about hot runner, it is easy to choose the most suitable hot runner system, thus ensuring the smooth injection molding process and improving product quality.

1. Correct selection of hot runner product series

Hot runner suppliers often make their hot runner components into product series according to the different sizes and weights of processed plastic parts. For example, processing large plastic parts with large-size nozzles and processing small plastic parts with small-size nozzles. Therefore, after the user correctly selects the type of hot runner (hot tip system or valve system), it is the choice of hot runner product series. So as to determine the structural size, design and manufacture of the die. If the hot runner product series is not selected correctly, it will be found in the later stage of mold processing or plastic parts production, and the error is very serious and difficult to save. In order to help correctly select the hot runner product line, each hot runner supplier has some guiding technical documents for reference. Users should work closely with hot runner suppliers to choose a good hot runner product line.

2. Injection pressure loss in hot runner system

Injection pressure loss in hot runner system can not be ignored. Many users of hot runner mold have a misunderstanding that the injection pressure loss of hot runner is much smaller than that of cold runner. The reason is that the plastic solution in the hot runner is always hot during the whole injection process. In fact, many times the situation is just the opposite. Due to the need of hot runner structure design in hot runner mold, the flow distance of solution in hot runner system will be greatly increased. Therefore, the injection pressure loss in the hot runner system is often very large. In practical application, the pressure loss of hot runner system is too large, which leads to the difficulty of injection molding. Therefore, CAE software should be used to analyze and calculate the flow channel of plastics with poor processing fluidity (such as PC and POM). ), the solution in the hot runner system has a long flowing distance, or the parts are heavy. CAE software based on flow channel analysis and calculation includes MoldCAE and so on.

3. Standard and nonstandard hot runner systems

Various hot runner manufacturers provide standard and non-standard hot runner systems. If possible, users should try to choose a quasi-standard hot runner system. Try to select nozzle, hot runner plate, gate insert, etc. Having a standard length and size. Its advantages are that the price of quasi-standard hot runner system is lower than that of non-standard hot runner system, the delivery time is much shorter, and the parts can be interchanged, which is beneficial to future use and maintenance. Once a part is broken, just buy a standard part and install it. The common shapes of standard hot runner plate are 2-cavity row, 4-cavity row, 8-cavity row, 4-cavity X-shape, 8-cavity XX-shape and so on.

4. Select the number and layout of cavities on the mold.

When designing hot runner molds and selecting the number of cavities, users should not only put as many cavities as possible to improve production efficiency, but also consider the design of hot runner. The selection of the number and layout of cavities on the mold should be beneficial to the flow balance of plastic solution in the hot runner system. For example, if several cavities with the same shape are arranged in a row, it is better to choose two or four cavities instead of three. Because the mold is a row of 2 or 4 cavities, its hot runner can be designed as a completely natural balanced system. On the contrary, the 3-cavity mold needs to balance the manual flow of the hot runner distributor. In order to achieve the purpose of flow balance, different channels on the hot runner distributor adopt different channel sizes. The quality of flow balance depends on the work quality of the designer of a specific hot runner. Therefore, users should try their best to choose the number of cavities that are beneficial to the flow balance (for example, choose 16 cavity instead of 15 cavity, etc.). ) to eliminate any errors caused by artificial design of traffic balance.

5. Limitation of minimum cavity distance

When designing a mold for producing micro parts, people generally want to arrange the cavities as close as possible, so that the mold can be compact and more cavities can be placed. However, the minimum cavity distance will be limited by the minimum distance between hot runner elements (such as nozzles). Therefore, users should pay attention to check the minimum allowable nozzle distance when designing molds with close cavity distance. Avoid rework of mold design.

6. Types of processed plastics

When selecting the hot runner system, the type of processed plastic is a very important consideration. If processing glass fiber reinforced plastic (such as glass fiber reinforced plastic nylon material, etc.). ), should choose the gate insert with good wear resistance. If processing easily pyrolytic plastics (such as PVC), we should choose a hot runner system with smooth runner and no flow dead angle. If processing plastics with poor fluidity (such as PC), we should consider choosing a larger nozzle series and using a larger runner cross-section size in the hot runner plate.

7. Maturity of hot runner products

The maturity and application history of each hot runner product are different. A new hot runner product takes a long time to gradually improve. Hot runner manufacturers are constantly introducing new products, but at the same time, they will also eliminate hot runner products that have been proved unsuitable by practice. Therefore, users should try to choose hot runner products with good maturity, high popularity and long application history. For this kind of products, both hot runner manufacturers and other hot runner users have many experiences and successful cases for new users with little experience to learn from.

8. Status of hot runner system before delivery

Some hot runner suppliers will test their hot runner systems before delivering them to users. For very important application projects, even actual injection experiments will be carried out. However, the testing scope of each hot runner supplier before delivery of the hot runner system is different. Users should understand it and be aware of it.

9. Hot runner multi-zone temperature control

If users need to buy a large-scale complex hot runner system, or process plastic with temperature sensitivity and narrow processing parameters, they should choose multi-zone temperature control hot runner design scheme respectively. In this way, users can adjust and control the temperature distribution locally according to their own needs. An ideal hot runner system should have a uniform temperature distribution. But in fact, there are many reasons for the temperature difference in the hot runner. For example, the mass of the heating element of the hot runner, the heat loss at the joint between the hot runner system and the mold is too large, and the shear heat of the plastic melt in the hot runner is different. The larger and more complex the hot runner system is, the more you should choose the hot runner system with multi-zone temperature control.

10。 Application projects with color change requirements

Some users use the same mold to produce the same variety of plastic parts with different colors, which is an application project with color change requirements. When ordering hot runner, try to choose a hot runner system with small runner volume to speed up the color changing process and reduce waste. At the same time, any bend in the hot runner system must be smooth and there can be no dead ends. If the valve hot runner system is used to produce plastic parts with discoloration requirements, there will often be a dead spot behind the valve needle, which needs special attention.

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The balance of flow must be considered when designing the special-shaped multi-cavity die. If the size and weight of the parts are too different, and the injection pressure difference of each cavity is above 200-300BAR, it is difficult to achieve flow balance by changing the size of the runner in the hot runner system. In the special-shaped multi-cavity mold, if the flow is not balanced, there will be problems such as insufficient filling and pressure keeping, too many filling of other parts, large flash and high residual stress. At this time, it is necessary to consider using the valve hot runner system or changing the overall design scheme of the mold. Valve-type system allows users to close the gates of early-filled cavities at an appropriate time to avoid overfilling of these cavities.

12. Proportional relationship between cavity and hot runner volume

Compared with the cavity volume, the runner volume of hot runner system should not be too large. Otherwise, the plastic solution will stay in the hot runner system for too long, which will lead to thermal decomposition. Can't produce qualified plastic parts. If the weight of plastic parts is too small, the scheme of using both cold and hot runner should be adopted. Due to the increase of injection quantity after using cold runner, it is helpful to improve the proportional relationship between cavity and hot runner volume and shorten the residence time of plastic melt in hot runner system.

13. Adopt test mode.

Hot runner molds are expensive, especially hot runner molds with high cavity number (such as 96, 128 cavity, etc.). ) and the price is higher. If you want to open up new application fields, lack experience, or try to use newer hot runner components (such as nozzles or new gates), you can consider making a simple single-cavity trial mold first to verify the feasibility of the scheme. After gaining enough experience, we can make expensive formal tooling.

14. Drawing of hot runner components on the mold drawing

Hot runner suppliers usually make their hot runner components into electronic galleries for users to use. When designing and drawing the mold drawing, the mold designer can select the required nozzle and other component drawings from the electronic library of hot runner components and place them in the appropriate mold position. Because hot runner suppliers often update their hot runner products, users should pay attention to constantly asking hot runner manufacturers for the latest gallery. Although people have begun to design molds with 3D method, the electronic galleries of hot runner components of hot runner suppliers are mostly 2D. Some manufacturers have begun to establish 3D hot runner component library to adapt to the development of 3D mold design.

15. Quality guarantee period

Hot runner suppliers will provide some warranty for their hot runner products. The warranty period varies from one year to five years, depending on the specific hot runner products purchased by hot runner manufacturers and users. During the warranty period, hot runner products have problems under normal operation and use by users, and hot runner suppliers will replace them free of charge. Obviously, the longer the warranty period, the better for users. In order to ensure the validity of the quality warranty period, users should respect the use and maintenance regulations of hot runner, and cannot modify or change any hot runner components without the consent of the hot runner supplier.

16. Location of processed products and aquatic products

As a plastic melt molding product, hot runner product inevitably has a nozzle position in the production process. Users need to fully communicate with the technicians of hot runner manufacturers when choosing products designed and produced by hot runner companies. Cost of hot runner nozzles (flat nozzles, pointed nozzles, multi-head nozzles, needle nozzles, etc.). ) accounts for an important part of the hot runner system. Choose the right hot nozzle. In the design process, it is very important for the whole system to achieve ideal results. On the one hand, the cost can be controlled and the suitable hot nozzle can be selected according to the actual situation, on the other hand, the probability of secondary design in the production and use process can be reduced.

This paper discusses some problems that need to be considered when purchasing hot runner system. Hot runner molds, like traditional injection molds, have a lot of experience and skills, and users need time to gradually accumulate them.