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How to operate and maintain the hot runner system?

Date:2020-05-21View:1393

Production, operation and maintenance of hot runner system:


(1) Preparation

The mould worker connects the cooling water channels of the moving mould, the fixed mould and the hot half mould. If the temperature requirements on both sides of the dynamic mold and the fixed mold are different, a separate water path must be connected for rotation. If the product appearance quality requirements are high, it is recommended to separate the mold temperature on both sides of the moving and fixed mold: if the heat generated by the heating of the hot runner on the side of the hot half mold is more, the cooling water can be separately connected; if the heat generated by the heating of the hot runner on the side of the hot half mold is absorbed or lost by the template, the model can be connected with the warm water at the appropriate temperature to compensate for the heat loss.


The heating cable between the hot runner and the thermostat shall be connected correctly according to the mark of the plug, and the plug QQ shall be locked to prevent loosening. If the heating output cable is connected reversely with the heating cable, all thermocouples will be burnt. After the mold is packed, the screw temperature of the first injection molding machine reaches the required set temperature. At the same time, turn on the mold temperature machine for heating, so that the mold temperature reaches the set temperature required for production. Then change the working temperature of the heated hot runner system to plastic.


It should be noted that after the hot runner of the new mold rises to the set temperature, it will take about 5 to 10 minutes (to ensure uniform heating). If the raw material contains fiberglass, it will take longer (about 10 to 15 minutes) because the heat transfer performance of the tungsten steel tip is poor.


(2) Power on

First of all, find out the raw materials used in the last mold test, adjust the temperature of the screw and nozzle of the injection molding machine to the temperature of the raw materials in the melting state, and select the appropriate plastic materials to clean the screw


If the plastic produced contains LCP + 30% glass fiber, clean the hot runner with pure LCP material (without glass fiber). After opening, it should be noted that the rubber outlet is very smooth; when it is found that one or several hot nozzles do not produce materials, there are two situations as follows:


There is cold material in the gate, which can be baked and melted by hot air gun, and then the safety door is closed to spray glue again;

If there is still hot nozzle without material, find out the number of nozzle according to the location map of hot nozzle. The temperature of the nozzle is increased by 10 ~ 20 ℃ on the original basis, and then it is ignited immediately (no more than 3 times). After tapping the glue, cool it to production temperature. At this time, if the gate is still blocked, the production shall be stopped immediately, and the hot nozzle of the blocked rubber shall be removed from the lower mold or the supplier shall be informed to handle it.


3) Stop waiting

Immediately clean the rubber in the hot runner with pure LCP material to keep the residual material in the hot runner and the head of the hot nozzle inside. It is a LCP material with good fluidity in the whole process, and ensure the next test or production to be carried out smoothly. For more than 5 minutes due to machine failure or other reasons, it is necessary to put the hot runner in the insulation state of 250 ℃; if more than 10 minutes, it is set to 120 ℃.


(4) Change the color of raw materials

Clean the barrel and screw with raw materials until the old color is completely clear. Check the machine's nozzles and hot runner gates for old colors. Open the mold core and remove the plastic in front of the nozzle.


(5) Stop machine repair mold

Before separating the hot runner from the core, make sure that the hot runner heating output is closed and the nozzle temperature is cooled to room temperature (< 60 ℃). If the raw material contains glass fiber, use the raw material without glass fiber to remove the raw glass fiber material, otherwise the glass fiber material may be carbonized in the next heating.