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| Frequently asked questions |
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 Question:What is Hot runner Systems? |
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 Answer: |
Hot runner technology is used in mold injection runner system, which is the hot-point direction for the plastic mold injection crafts development.
The hot runner molding is that the plastic has been kept in liquid status from the injection nozzle to the gate, then the plastic needs not to be taken out as waste after solidification, which can be injected to the cavity next time.
The ideal mold injection system should shape the parts in the same density, which is not effected by the all the runners, gate drooling. Compared with cold runner, hot runner can make these parts by ensuring the plastic in the runner in melting status without sticking on formed parts. Hot runner system is also named as hot collecting pipe system, or non-runner mold injection.
Basically, the hot collecting pipe system can be regarded as machine barrel and the extension of the mold nozzle. The function of the hot runner system is carrying the plastic to each gate.
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| Question:What is the advantage of the hot runner? |
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| Answer: |
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Shortening the processing cycle time to heighten the effect.
Replacing the cold runner to avoid generating materials wastes which needs to be smashed.
Advancing the destiny of the parts to enhance the product quality.
Decreasing the parts stress to avoid the deformation.
Adopting the valve gate by injection in step, to make the part series in different sizes.
Providing more process program-control to precisely adjust the mold injection.
The critical nature of the hot runner system:
Precise controlling the melting plastic temperature to avoid the material degradation.
Balanced manifold design making the parts cavity filling non-uniformity.
The proper size of the nozzle can ensure the smoothly flow of the melting material and the sufficient filling of the cavities.
The correct gate structure and size can ensure the cavities in sufficient filling , and the timely close of the pin valve gate ,to decrease the flashing ,in order to shorten the cycle time.
There is no dead area in the runners to ensure the color changing quickly ,to avoid the materials being degradation.
Making the stress decreased to minimum to decrease the mold locking stress.
Making sure the time is proper.
The correct adoption of the hot runner system will increase the production effect by 20-30%, to make the mold injection be more competitive. |
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| Question:What is the hot runner system's disadvantage? |
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| Answer: |
Comparing with the cold runner and three-plate molding, the operation of hot runner system needs the support of more technicians and the experienced senior maintainers. The molding maintenance needs long time and the parts can be easily damaged. As the heaters can be easily damaged, so the certain electrical maintenance is also required, as the diameter of the hot runner nozzle is very small which can be easily blocked. As to the parts and materials which can be formed under major pressure (such as the thick-wall cover of the hand-set electrical products), the thin nozzle usually will be broken earlier. The pin of the nozzle is required in good thermal conductivity and also can be with good wear-resistance (as it can bear the brush of the periodically high-speed flowing melting materials). The hot runner system has higher requirement on the process precision of the gate. The mismatch of the design and the using parameter can make the internal leakage of plastic. The cost will be caused as the hot runner system will produce the radiation and loosing thermal power. The nozzle without pin valve being long-term open status will be casting, and then there will be solidified plastics on the cavities which need to be removed. The size of the runner needs to be counted carefully, as too small of the size, the stress will be loosed; as too large of the size, the temperature will be uneven due to the bad thermal conduction of the plastic materials. The delivery time of the hot runner system is long normally. As the manifold and the front & back plate need to be made according to the special craft request for each customer, and the design and producing is made against the design of the mold. |
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| Question:The composition of the hot runner system. |
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| Answer: |
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Hot runner plate: The main function is to carry the molten bath thermostatically from the main runner to each single nozzle, during the bath carrying process, the stress of the bath needs to be reduced as little as possible, and the materials is not allowed to be degraded.
The normal used hot runner plates styles are: ¡°1¡± type, ¡°H¡± type, ¡°Y¡± type, ¡°X¡± type. Structurally, there are two kinds: outer-heating hot runner plate and inner-heating hot runner plate.
Nozzle: The hot runner molds are in many kinds according to the different nozzle structures, but these kinds are quite similar¡£ The hot runner systems are different in quality and price, due to the process crafts and using ways are different. Normally there are open type, pin valve type, and other special types.
The technology of pin valve nozzle is advanced, the merits are:
a. There is no gate vestige on the parts, the gate is very smooth.
b. The gate in larger diameter can be used, which can make the cavities quickly be filled, and the injection stress can be decreased further to avoid the parts deformed.
c. The fusible link and casting can be prevented when opening mold.
d. When the mold injection machine screw brad is back, the materials can be prevented efficiently from absorbing to the cavities.
e. It can match the sequential control system to reduce the parts welting mark.
The spare heaters are the main part composed of the hot runner system. The heating precision and life time influences the control of the mold injection and the stable work of the hot runner system. Normally there are heating rod, heat coil, tube heater and spiral heater etc.
Temperature controller is the instrument controlling the temperature of each part in the hot runner system. From bottom to top, there are on-off set and PID control set (proportional-differential ferential control set), new smart control set, etc. The internal other components can be matched to use according to the customer¡¯s request. |
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