ABS sheet extrusion molding process control points
(1) Feeding. The material should be fed in time to ensure that the hopper is not empty, in order to prevent the air from directly entering the drying cycle system, affecting the dry return air speed. Different raw materials can not be mixed, pay attention to the grade of the material and the type of material. In addition, the unpacking should be carried out outside the hopper to prevent the ropes, debris and the like from being mixed into the hopper, causing the unloading port to clog or jam the ingredient tray.
(2) Drying. When drying, the temperature setting is required to be correct, and the temperature of the tank is guaranteed to reach the set value. At the same time, check whether the heat and air volume are normal. It is necessary to ensure that there is sufficient circulating air volume, that is, the circulating pipeline is sealed, the filter is not blocked, and the fan is operating normally. And check the drying parameters regularly (such as once every 4h).
(3) Ingredients. The batching time is set correctly, so that the batching motor runs normally, ensuring smooth feeding.
(4) Extrusion molding.
1 The processing temperature, especially the temperature in the barrel area and the die area, should be set reasonably. The temperature of the feed section should not be too high, so as to prevent the pellets from melting too early, affecting the feeding; the temperature of the exhaust section is higher, which is beneficial to the exhaust; and the temperature of the second metering section is not too high to reduce the melt pressure fluctuation. In addition, due to different plate types, the width of the die is not the same, should pay attention to adjust the temperature on both sides of the die;
Too high to prevent discoloration. The temperature of the three rolls should be set reasonably. If the temperature is too high, the entire plate will be off the roll; and if the temperature is too low, the edge of the plate will be off the roll.
2 Control the vacuum to the specified value so that the vacuum port is not blocked to ensure the exhaust effect.
3 Preheat before starting the machine. After each heating temperature reaches the set value and the temperature is constant for 0.5h, it can be turned on. When starting up, according to the load and melt pressure conditions, slowly increase the screw speed, avoid one step in place; if the screw has been emptied, the screw speed must be controlled below 10r/min at the beginning, until the melt pressure rises rapidly. Accelerate to protect the device. Before shutting down, use insulation
The mode can be turned off after the temperature of the barrel is lowered to the holding temperature, which can reduce the degree of carbonization decomposition of the materials in the machine.
4 The opening of the die should be suitable, generally 115% to 130% of the thickness of the plate. Especially when the sheet is extruded, if the opening is too large, the thickness of the plate will be unevenly distributed laterally.
5 The filter screen generally adopts 3 to 5 layers (1 layer is 180um copper mesh, and the rest is 125um steel mesh). It is required to change once every 12h. If the extrusion is stable and there is no impurity, the time can be extended appropriately. Change the net whenever there are more impurities or the melt pressure before the net exceeds the specified value.
6 plate traction tension control, in principle, should adjust the difference between the three-roll line speed and the traction line speed is 0.01m / min -0.06m / min, it is recommended to slightly sag after the plate is over the upper roller.
7) The cooling small roller requires clean and flexible rotation; the shearing machine requires the platform to be smooth and the knife edge to be smooth without rust to prevent the bottom of the board from being scratched.
8) The process parameters should be checked once every 2 hours, and the abnormality is adjusted in time.
5. Treatment of ABS sheet quality problems
When quality problems occur in ABS sheets, first analyze the possible causes of quality defects, and find them one by one, and take corresponding measures for the contributing factors.
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