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Select and buy hot runner system when the technical problems
Dec 09, 2017

Select and buy hot runner system when the technical problems

The user in the selection and purchase of hot runner system will involve many specific technical aspects. If the user has a good knowledge of hot runner-related technology, it is easy to choose and purchase the most suitable hot runner system to ensure smooth and improve the quality of the back of the injection molding process.

1. Hot runner product line of the right choice

Hot runner suppliers are often in accordance with the size of the processing of plastic parts of different size, the hot runner components into a product line. Such as large plastic parts using large-size nozzle processing, small plastic parts with small size of the nozzle processing. Therefore, the user in the correct choice of hot runner type (both hot tip or valve type system), is the hot runner product line of choice. And thus determine the structure of the mold size and design and manufacturing. If the hot runner product line selection is not correct, to the late mold or plastic parts production found, the error is very serious and difficult to save. To help make the right choice of hot runner product line, each hot runner supplier has some guidance for the use of technical documents for reference. The user should work closely with the hot runner supplier to select the hot runner product line.

2. Injection Pressure Loss in Hot Runner Systems

Injection molding pressure loss in hot runner systems can not be ignored. Many hot runner mold users have a misunderstanding, both that the cold runner compared to hot runner injection pressure loss is much smaller. The reason is that the plastic solution located in the hot runner is always hot throughout the injection molding process. In fact, many times the situation is just the opposite. In the hot runner mold due to the needs of hot runner design, will melt in the hot runner system in the flow distance greatly increased. So the hot runner system in the injection pressure loss is often larger. In practice, due to the hot runner system injection pressure loss is too large, resulting in injection molding difficult situation is many. Therefore, the poor flow of plastic processing (such as PC, POM, etc.), the solution in the hot runner system in the flow distance, or parts of a large weight, etc., should be CAE software for channel analysis calculations. CAE software focused on flow path analysis and calculation has MoldCAE and so on.

3. Standard and non - standard hot runner systems

Each hot runner manufacturer provides both standard and non-standard hot runner systems. If possible, users should try to select the standard hot runner system. Both try to select the standard length and size of the nozzle, hot runner plate, gate inserts and so on. The advantage of standard hot runner system than non-standard hot runner system, low price, delivery time is much shorter. And parts are interchangeable, is conducive to future use and maintenance. Once a part is broken, buy another quasi-standard parts installed on the line. Common standard hot runner plate shape has 2 cavities in a row, 4 cavities in a row, 8 cavities in a row, 4 cavity X shape, 8 cavity XX shape and so on.

4. Selection of Number and Layout of Cavity in Mold

Users in the design of hot runner mold selection cavity number, in addition to try to put more cavity to improve production efficiency, but also should consider the hot runner design. The number of cavities on the mold and the choice of layout should be conducive to the flow of plastic melt in the hot runner system balance. For example, if several cavities of the same shape are arranged in a row, it is preferable to select two or four cavities instead of three. Because the mold cavity of 2 cavity or 4 cavity, can design its hot runner completely natural balance system. Conversely, the mold cavity of the 3-cavity requires manual flow balancing of the hot runner manifold. Both in the hot runner manifold for different flow paths using different runner size, in an attempt to achieve the purpose of flow balance. Flow balance depends on the quality of the work of the specific hot runner design. Therefore, the user should try to choose the number of flow-friendly cavity (such as the election of 16-cavity rather than 15-cavity, etc.) in order to eliminate artificial design flow balance caused by any mistakes.

5. Limitation of Minimum Cavity Distance

In the design and production of small parts of the mold, it is generally desirable to arrange the distance from the cavity as close as possible so that mold can be more compact and put more cavity. But the minimum cavity distance is limited by the minimum distance between hot runner elements such as nozzles. Therefore, users in the design cavity close to the mold, we should pay attention to check the minimum allowable nozzle distance. To avoid mold design rework.

6. Types of processed plastics

When selecting a hot runner system, the type of plastic processed is a very important consideration. If the processing of glass-reinforced plastics (such as glass reinforced nylon materials, etc.) should be used on the gate wear good inserts. If the processing is easy to thermal decomposition of the plastic (such as PVC) should be used smooth runner, no flow of hot runner system. If the processing of poor mobility of plastic (such as PC) should consider the choice of larger nozzle series, and in the hot runner plate using a larger runner cross-sectional size and so on.

7. Hot runner product maturity

Each hot runner product maturity and application history is not the same. A new hot runner product is available for a long time to gradually improve. Hot runner manufacturers continue to introduce new products at the same time, will also be eliminated by the practice proved inappropriate hot runner products. So users should try to choose a mature, more popular, long history of hot runner products. For these products, whether hot runner manufacturers, or other hot runner users, have more experience and success stories for the experience of small new users learn.

8. Hot runner system status before shipment

Some hot runner suppliers in the hot runner system shipped to the user before the system will conduct a certain test. For very important applications even the actual injection molding experiment. But each hot runner supplier in the hot runner system before delivery of 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 purchase large-size complex hot runner system, or processing of temperature-sensitive, narrow processing parameters of the plastic, you should choose a multi-zone temperature control were hot runner design. So that the user can according to the needs of the local temperature distribution and control. An ideal hot runner system should have a homogeneous temperature distribution. But in fact there will be a variety of reasons leading to different temperature throughout the hot runner. Such as hot runner heating element quality reasons, hot runner system and die with the Department of excessive heat loss, plastic melt in the hot runner where the heat of the different shear. Hot runner system size larger and more complex, the more should choose a multi-zone temperature control hot runner system.

10. There are color requirements for the application of the project

Some users use the same mold with the production of different colors of the same species of plastic parts, which is the application requirements for color change projects. When ordering hot runner, try to select the runner small size hot runner system to speed up the color change process and reduce waste. While any hot runner system in the corner must be round and smooth, there is no flow dead ends. If the valve-type hot runner system for color-changing requirements of plastic parts, there are often in the valve needle behind the flow of dead ends (DEAD SPOT), to be given special attention.

11. A mold of multi-cavity mold

In the design of a mold heterogeneous multi-cavity to consider the mold, you must consider the flow balance. If the size of the weight difference between the parts is too large, the cavity of the injection pressure difference between 200-300BAR above, by changing the hot runner system in the runner size is difficult to achieve flow balance. If the flow in a mold heterogeneous multi-cavity mold imbalance, there will be some parts filling pressure is not enough, other parts are filling over, large residual stress flash problems. Should consider the use of valve-type hot runner system, or change the overall design of the mold. The valve system allows the user to close early filled cavity gates at appropriate times to avoid overfilling of these cavities.

12. The proportional relation between cavity and hot runner volume

The runner volume of the hot runner system must not be too large compared to the cavity volume. Otherwise the plastic solution in the hot runner system residence time is 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. Increased injection volume due to the use of the cold runner will help to improve the ratio of cavity to hot runner volume and shorten the residence time of the plastic melt in the hot runner system.

13. Using the trial mold

Hot runner mold is more valuable, especially the high cavity number of hot runner mold (such as 96,128 cavity, etc.), the price is even higher. If it is to open up a new application areas, lack of experience, or try to use the newer hot runner components (such as nozzles or new gates), etc., should consider making a simple, single cavity trial mold, To carry out the feasibility of the program validation. To obtain sufficient experience, and then make the price of formal work die.

14. Drawing of hot runner components on mold drawing

Hot runner suppliers generally make their hot runner components electronic library, for users to use. Mold designers in the design drawing mold map, hot runner components from the electronic library can be selected in the nozzle and other components of the map, into the appropriate mold position. As the hot runner suppliers will often update their hot runner products, so users should pay attention from the hot runner manufacturers continue to obtain the latest gallery. Although people have begun to use 3D design of molds, but the hot runner suppliers of the hot runner components, the vast majority of electronic library is still 2D. Some manufacturers have begun to set up 3D hot runner component library, to adapt to the development of 3D mold design

15. Quality Warranty Period

Hot runner suppliers will provide some of their hot runner product warranty period. Warranty period from one to five years, depending on the hot runner manufacturers and users to purchase specific hot runner products. In the warranty period, if the hot runner products in the user's normal operation 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 of the warranty period, the user should respect the use of hot runner and maintenance requirements, not without the hot runner supplier agreed to modify any hot runner components changes.

16. The location of the product water treatment

Hot runner products, as a plastic melt molding products, in the production process, the nozzle position is inevitable. Users in the choice of hot runner design and production of products, and hot runner manufacturers need to fully communicate technical personnel. The cost of the mouth (mouth, mouth, mouth, mouth, needle mouth, the price difference is relatively large) than the hot runner system accounted for an important part.Choose the right design hot mouth, in the design process for the entire system Operation to the desired effect is very important, on the one hand can control costs, according to the actual situation to choose the right hot mouth, on the other hand to reduce the use of the production process requires secondary design probability.

This article discusses some of the issues to consider when selecting and purchasing hot runner systems. Hot runner mold and the traditional injection mold production and use of the same, which has a lot of experience and skills, the user needs time to accumulate.

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