Operation and maintenance of hot runner system
Publisher: Administrator Date: 2023-11-02
hot runner systemSwitching on/off operation
(1) Preparation
The mold worker connects the cooling water channels of the moving mold, fixed mold, and hot half mold of the mold. If the temperature requirements on both sides of the moving mold and fixed mold are different, a separate loop water channel must be connected; If there is a high requirement for the appearance quality of the product, it is recommended to connect the mold temperatures on both sides of the moving and fixed molds separately. If the heating of the hot runner on the hot half mold side generates more heat, the cooling water circuit can be connected separately; If the heat generated by the heating of the hot runner on the hot half mold side is absorbed or transferred by the mold, a suitable temperature of mold temperature water can be connected to compensate for the heat loss
The heating cable connection between the hot runner and the temperature controller should be correctly connected according to the plug logo, and the plug lock should be fastened to prevent loosening. For example, reversing the connection between the heating output cable and the temperature sensing cable can cause all thermocouples to burn out, which is an open circuit. After installing the mold, first increase the temperature of the injection molding machine screw to the required set temperature, and also turn on the mold temperature machine for heating to raise the mold temperature to the required set temperature during production, Afterwards, heat the hot runner system to the working temperature of the plastic
It should be noted that after the hot runner of the new mold reaches the set temperature, it needs to wait for about 5 to 10 minutes (to ensure uniform heating). If the raw material contains fiberglass, it takes longer (about 10 to 15 minutes) because the heat transfer of the tungsten steel tip is poor
(2) Power on
First, check which raw material was used during the last mold trial, adjust the temperature of the injection molding machine screw and nozzle to the temperature of the raw material in the molten state, and select a suitable plastic raw material for cleaning the screw
If the plastic produced contains 30% LCP glass fiber, pure LCP material (excluding glass fiber) can be used to clean the hot runner; After the mold is opened, air injection should be carried out, and at this time, it should be seen that the glue discharge from each outlet is very smooth; When it is found that a certain or several hot nozzles do not discharge, there are two situations:
If there is cold material at the gate, it can be baked with a hot air gun to melt the cold material, and then the safety door can be closed and the glue can be sprayed again;
If there is still a certain hot nozzle that does not discharge, find the nozzle number according to the schematic diagram of the hot nozzle position. Correspondingly, increase the temperature of the nozzle by 10-20 ℃ on the original value, and then immediately empty shoot (no more than 3 times). Once the glue is released smoothly, immediately cool down to the production temperature. The problem can be solved by combining the mold and testing the product; If there is still a gate blocked at this time, production needs to be stopped immediately, and the hot nozzle with the blocked glue needs to be removed from the mold for cleaning or the supplier should be notified for handling
(3) Stop waiting
Immediately clean the rubber material inside the hot runner with pure LCP material, which can maintain the residual material inside the hot runner and at the head of the hot nozzle. Throughout the entire production process, it is LCP material with relatively good fluidity, while ensuring the smooth next mold trial or production. If the machine malfunctions or other reasons exceed 5 minutes, the hot runner needs to be set at a insulation state of 250 ℃; If it exceeds 10 minutes, set it to 120 ℃
(4) Change color of raw materials
Clean the material barrel and use raw materials to clean the screw until the old color is completely removed. Check the machine nozzle and hot runner gate for any residue of old color. Open the mold core and remove the plastic in front of the nozzle
(5) Shutdown mold repair
Before separating the hot runner from the mold core, it is necessary to confirm that the heating output of the hot runner is turned off and ensure that the temperature of the hot nozzle has cooled to room temperature (<60 ℃); If the raw material contains fiberglass, remove the original material without fiberglass, otherwise the fiberglass material may carbonize during the next heating
2. Installation precautions for hot runner:
(1) Place the mold, level the upper mold, and clean all hole positions and templates with an air gun
(2) Check the dimensions of each hole position, with a focus on checking the depth. Remove burrs from the template. At the same time, check whether the screw holes of the lock splitter plate, as well as the center nail and anti rotation pin holes, have been processed. The first time making a hot runner mold in this area, the master often misses it
(3) Scan the hot nozzle sealing position and upper stage position that match the mold with red lead
(4) Trial assemble the hot nozzle, then remove it to check if the sealing position 1 has rubbed against the red lead, and if the step position 2 has touched the mold. If not, stop the installation, check the cause of the error, and adjust it to ensure a tight fit without material leakage. During this process, be careful not to damage the nozzle tip
(5) Install all the hot nozzles, and also install the center pad, center pin, and anti rotation pin. Scan the red lead on its surface
(6) Check the nozzle plane and center pad height, and control the error within 0.05mm
(7) Try installing the splitter plate. Be careful not to miss the hot nozzle sealing ring when formally installing the splitter plate
(8) Check the coordination between the splitter plate and the hot nozzle to ensure that they all touch the red lead and do not leak adhesive
(9) Organize the hot nozzle wiring to ensure neatness and aesthetics, and number each group of wires in sequence. Connect the wires to the socket
(10) Formally install the splitter board, tighten the fixing screws of the splitter board (be sure to lock the balance and keep the four corners of the splitter board at the same height), control the splitter board meson to be 0.10-0.15mm higher than the surrounding mold frame plane, and then sweep red lead on the splitter board meson
(11) Trial install the code template and check if the plane touches the meson red lead to ensure that the template presses against the splitter plate meson
(12) Lock the mold tightly, erect the mold, and check whether the matching between the gate and the nozzle tip meets the requirements from the parting surface. Ensure that the nozzle tip is 0.1-0.2mm lower than the gate surface, and the nozzle tip cannot be eccentric. Use a multimeter to carefully check each group of circuits to ensure that there are no short circuits, open circuits, leakage, etc. Each group of circuits corresponds correctly, ensuring that all circuits are normal
(13.) Connect the temperature controller and conduct a trial heating. The first heating should be kept within 100 degrees Celsius for ten minutes for preheating and dehumidification to protect the heater. Then, heat it up to the required temperature. If normal, arrange for the lifting of the mold for trial molding
3. Maintenance of hot runner
(1) Regularly inspect the connecting lines, wire protective sleeves, or wire skins of the hot runner for aging, damage, or pressure damage. If any, promptly handle them (replace with new protective sleeves, properly wrap with electrical tape, cut off the pressure damage and reconnect)
(2) Check if the hot nozzle and splitter plate are deformed, and if so, promptly notify the supplier for handling; Check for rust, if any, carefully check for loose or cracked water channel plugs, and promptly handle them
(3) After a period of production, molds that need to be parked for a long time must undergo rust prevention and removal work
4. Common troubleshooting
The hot runner has malfunctioned and can only be repaired by a dedicated mechanical technician
(1) No heating
Check if the cables are properly connected;
Check if the thermocouple of the mold hot runner is open circuit;
Check the cable for damage and short circuit to ground;
Check if the mold hot runner heater is short circuited to ground;
Check if the mold is leaking water or oil. If it is due to mold leakage, set the temperature of all areas to within 100 ℃ and heat until the water evaporates dry. Then, restart the machine;
Confirm that the set temperature has been adjusted (above room temperature)
After identifying the cause of the problem and resolving it, restart the machine again
(2) The temperature is unstable, fluctuating from high to low
Check if the thermocouple of the mold hot runner is normal; If it is still unstable, check if the different areas of the hot runner thermocouple are reversed
(3) The temperature cannot rise to the set temperature
The hot runner mold is too cold, and due to the good cooling effect of the waterway, it carries too much heat away
(4) When heated, the temperature actually decreases
The thermocouple in this area of the mold hot runner is reversed
(5) Uncontrolled heating temperature, continuous heating
Check if the thermocouple of the mold hot runner is normal; Is the contactor stuck
(6) The screen display is chaotic
The display letters or digits are incomplete, but the heating is normal. The display board is connected to a loose flexible cable, and it is reconnected
(7) No display on the startup screen
Check whether the three-phase power supply is properly connected and whether the switch is turned on; Check if the power supply of the temperature control box power board is normal
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