Select And Purchase Hot Runner System Technical Problems
Users in the choice and purchase hot runner system will involve a lot of specific technical aspects. If the user has good technical knowledge related to hot runner, it is easy to choose and purchase the most suitable hot runner system to ensure that the back of the injection molding process and improve product quality smoothly.
1. Hot runner product line the right choice
Hot runner suppliers often according to the size of the plastic parts size and weight will be made of its hot runner components into the product line. Such as large plastic parts using large nozzle processing, small plastic parts with small nozzle size processing. Therefore, the correct selection of hot runner users (both the choice of hot tip or valve system), the hot runner product line is the choice. And thus determine the structure of the mold size and design and manufacturing. If the hot runner product line is not selected properly, it is found that the error is very serious and difficult to save when it is found after the mold processing or when the plastic parts are manufactured. To help you select the right hot runner product line, each hot runner supplier has some technical guidance for your reference. Users should work closely with hot runner suppliers, select the hot runner product line.
2. Injection pressure loss in hot runner system
Hot runner system injection pressure loss can not be ignored. Many hot runner mold users have a misunderstanding, both considered cold runner, hot runner injection pressure loss is much smaller. The reason is that the plastic melt in the hot runner is always hot throughout the injection process. In fact, in many cases the situation is exactly the opposite. Due to the design of the hot runner structure in the hot runner mold, the flow distance of the melt in the hot runner system is greatly increased. Therefore, hot runner system injection pressure loss is also often larger. In practice, due to the hot runner system injection pressure loss is too large, resulting in injection molding difficult situation is very large. So for the processing of poor mobility of plastics (such as PC, POM, etc.), the hot melt flow in the hot runner system, or large parts, such as weight, should be used CAE software for runner analysis and calculation. CAE software focused on runway analysis and calculation includes MoldCAE and others.
3. Standard and non-standard hot runner system
All hot runner manufacturers provide both standard and non-standard hot runner system. If possible, users should try to choose the standard hot runner system. Both try to choose the standard length and size of the nozzle, hot runner plate, gate inserts and so on. The benefits are quasi-standard hot runner system than non-standard hot runner system, low prices, delivery time is much shorter. And parts are interchangeable, is conducive to the future use and maintenance. Once a part is broken, buy another standard part and attach it. The common standard hot runner plate shape has 2 cavities, 4 cavities, 8 cavities, 4 cavities X, 8 cavities XX and so on.
4. Mold cavity number and layout of the choice
Users in the design of the hot runner mold cavity number, in addition to put more cavities to increase production efficiency, hot runner should also consider the design issues. Mold cavity number and layout of the choice should be conducive to the plastic melt flow in the hot runner system balance. For example, if several cavities with the same shape are arranged in a row, it is best to choose two or four cavities instead of three. Because of the 2-cavity or 4-cavity in-line mold, the hot runner can be designed as a completely natural balance of the system. Conversely, a 3 cavity mold requires a manual flow balance of the hot runner manifold. Not only in the hot runner manifold on different flow path using different runner size, in an effort to achieve the purpose of flow balance. Flow balance depends on the quality of the specific hot runner designers work quality. Therefore, users should try their best to choose the number of cavities that will help to balance the flow (such as selecting 16 cavities instead of 15 cavities, etc.) so as to eliminate any mistakes caused by the artificial flow balance.
5. Limits for minimum cavity distance
When designing molds for the production of tiny parts, it is generally desirable to keep the cavities as close as possible, so that the molds can be compact and possibly have more cavities. However, the minimum cavity distance is limited by the minimum distance between hot runner components such as nozzles. Therefore, users in the design of the cavity near the mold, pay attention to check the minimum allowable nozzle distance. To avoid the mold design rework.
6. Processing plastic types
When choosing a hot runner system, the type of plastic processed is a very important consideration. If the processing of glass reinforced plastic (such as glass reinforced nylon material, etc.) should be good wear resistance of the gate inserts. If processed easily pyrolytic plastic (such as PVC) should be used when the runner patency, no flow of hot runner dead angle system. If the processing of poor mobility of plastics (such as PC) should consider the use of a larger nozzle series, and in the hot runner plate larger runner section size.
7. Hot runner product maturity
The maturity of each hot runner product and the history of the application is not the same. A newly released hot runner product takes a long time to gradually improve. Hot-runner manufacturers continue to introduce new products at the same time, will also be eliminated by proven hot runner products inappropriate. Therefore, users should try to choose a good maturity, more popular, long history of hot runner products. For these products, whether it is hot runner manufacturers, or other hot runner users, have more experience and success stories for less experienced new users.
8. Hot runner system before shipment status
Some hot runner suppliers in the hot runner system shipped to users, the system will be a certain test. For very important applications even the actual injection molding experiments. However, each hot runner supplier in the hot runner system before the test range is not the same. Users should be aware of, be aware of.
9. Multi-zone temperature control of hot runner
If you need to buy a large hot runner complex system, or processing temperature sensitive, narrow processing parameters of the plastic, you should choose a multi-zone temperature control hot runner design. This allows the user to adjust and control the temperature distribution locally. An ideal hot runner system should have a uniform temperature distribution. But in fact there will be a variety of reasons lead to different temperatures throughout the hot runner. Such as the quality of hot runner heating elements, hot runner system with the mold with the excessive loss of heat at the plastic melt in the hot runner throughout the shear heat of different. Hot runner system larger and more complex, the more you should choose a hot runner system with multi-zone temperature control.
10. There are applications that require color change
Some users use the same mold to produce plastic parts of the same variety with different colors, which is the application that has color change request. When ordering a hot runner, hot runner systems with small sprue volume should be selected to speed up the color change process and reduce waste. At the same time, any runner in the hot runner system must be round and smooth without any dead ends. If valve hot runner systems are used to produce color changing plastic parts, there will often be DEAD SPOT behind the valve needle which must be given special attention.
11. A mold-shaped multi-cavity mold
In designing a multi-cavity multi-cavity mold design, we must consider the flow of balance. If the part size and weight difference is too large, the pressure difference between the injection molding cavity in more than 200-300BAR, by changing the hot runner system runner size is difficult to achieve flow equilibrium. If the mold in a multi-cavity mold flow imbalance, there will be some parts filling modest pressure is not enough, but other parts are overfilling, flash residual large residual stress problems. At this time should consider the use of valve hot runner system, or change the overall design of the mold. The valve system allows the user to close the early full cavity gate at the right moment in time to avoid overfilling the cavities.
12. The proportional relationship between cavity and hot runner volume
Compared with the cavity volume, hot runner system sprue volume must not be too large. Otherwise, the plastic melt in the hot runner system to stay too long, will produce thermal decomposition. Can not produce qualified plastic parts. If the weight of plastic parts is too small, it should be used with hot and cold runner program. Due to the increased injection volume after using the cold runner, it helps to improve the proportional relationship between cavity and hot runner volume and shorten the residence time of the plastic melt in the hot runner system.
13. Use trial mold
Hot runner mold more expensive, especially the high number of cavity hot runner mold (such as 96,128 cavity, etc.), the price is even higher. If you want to open up a new field of application, lack of experience, or trying to use newer hot runner components (such as nozzles or new gates), you should consider making a simple, single-cavity trial mold, To carry out the program feasibility study verification. After getting enough experience, then make expensive formal formal mold.
14. Drawings of hot runner components on mold drawing
Hot runner suppliers will generally be hot runner components made of electronic library for users to use. Mold designers in the design of the drawing diagram, you can select from the hot runner electronic library components needed nozzle and other components, into the appropriate mold position. Because hot runner suppliers will often replace their hot runner products, so users should pay attention from the hot runner manufacturers continue to obtain the latest galleries. Although people have begun to design molds in 3D, the vast majority of hot runner component electronic libraries for each hot runner supplier are still 2D. Some manufacturers have begun to set up 3D hot runner components gallery to meet the development of 3D mold design
15. Quality warranty period
Hot runner suppliers will provide some of its hot runner products warranty period. Warranty period from one year to five years, depending on the hot runner manufacturers and users to buy hot runner product projects. During the warranty period, if the hot runner products in the normal operation of users under the use of problems, hot runner suppliers will be given free replacement. Obviously the longer the warranty period, the more favorable to the user. In order to ensure the quality warranty period is valid, users should respect the use and maintenance of hot runner, hot runner can not change without the consent of the supplier, modify any hot runner components.
16. The location of the product water treatment
Hot runner products, as a plastic melt forming products, in the production process, the nozzle position is inevitable.Users in the choice of hot runner company design and production of products, the hot runner manufacturers need to fully communicate the technical staff. The cost of the mouth (flat mouth, sharp beak, long mouth, needle valve, etc., the price difference is also relatively large) than the hot runner system is an important part of the choice of design suitable hot mouth, in the design process for the entire system Operation to the desired effect is very important, on the one hand you can control the cost, according to the actual situation to choose the right hot mouth, on the other hand reduce the production and use of the need to secondary design opportunities.
