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Analysis of the cause of yellowing or discoloration on the production surface of plastic sheet equipment
Release time：
2022-05-13 15:30
(1) The heating temperature of the plastic sheet is too low. Increase the heating time and increase the heating temperature as much as possible.
(2) The heating temperature of the plastic sheet is too high. Minimize the heating time and reduce the heating temperature as much as possible. If the part of the plastic sheet is too hot, check whether the electric heater concerned is out of control.
(3) The temperature of the mold shell is too low. Heating and thermal insulation should be carried out to moderately increase the temperature of the mold shell.
(4) The temperature of the pressure-assist plunger pump is too low. Warm as much as possible.
(5) Excessive stretching of plastic sheets. Thicker plastic sheets should be used or plastic sheets with good plasticity and high tensile strength should be used, and this common failure can also be eliminated by changing the mold.
(6) The plastic sheet is refrigerated too early before it is completely formed. Increase the mold rate and pumping time rate of the plastic sheet as much as possible, the mold shell is as insulated as possible, and the plunger pump is heated as much as possible.
(7) The design scheme of the mold design is unreasonable. The following methods can be used to clear:
①Effective design of the mold ejection inclination. Generally, when the female mold is formed, it is not necessary to design the inclination of the die, but some inclinations of the design plan are beneficial to the uniform wall thickness of the product. When the male mold is formed, for butadiene and hard polyethylene plastic sheets, the ejection inclination should be about 1:20; for acrylate emulsion and isoprene rubber plastic sheets, the ejection inclination should be 1:20. More than 1:20.
② Appropriately increase the radius of the arc. When the corners of the product need to have rigidity, the slope can be replaced by the arc, and then the slopes are connected with small arcs.
③ Moderately reduce the Lashen depth. In general, the drawing depth of the product should be combined with the wide width. Considering that when the vacuum pump method is immediately used for forming, the drawing depth should be less than or equal to half of the wide width. When deep drawing is required, a pressure-assist plunger pump or a standard air pressure rolling forming method should be used. Even if this forming method is selected, the deep drawing layer should still be limited to the range less than or equal to the width.
(8) Excessive use of recycled particles. Its usage and quality should be controlled.
(9) The raw material formula does not meet the thermoforming regulations. The formula design scheme should be adjusted appropriately when making plastic sheets
plastic sheet,Equipment
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