Last year, Shanghai completed a total of 571 high-energy-consumption, high-pollution, low-value-added projects, shutting down and switching, and annual statistics saved 1.48 million tons of standard coal. In particular, the closing of the last batch of ferroalloys and small chemical fertilizer companies marked that the “two highs and one low†industries that the country has banned have already completely withdrawn from Shanghai.
It is reported that the focus of this year's industrial restructuring in Shanghai will shift to industries with relatively high energy consumption and pollution, and about 600 projects will be adjusted. For example, to integrate a group of smaller forging or casting process companies to improve the efficiency of energy use, which is too small to be eliminated. Some high-risk chemical companies will gradually shift outwards and strive to retreat beyond the outer ring within three years.
During the injection molding process, when the molten plastic meets in the form of multiple strands in the cavity due to the holes in the insert, the areas where the flow rate is discontinuous, and the area where the filling material flow is interrupted, a linear weld seam is produced because it cannot be completely fused. In addition, when the gate injection molding occurs, a weld seam will also be formed, and the strength and other properties of the weld seam are poor. The main reasons are as follows:
Processing:
The injection pressure and speed are too low, and the barrel temperature and mold temperature are too low, resulting in premature cooling of the molten material entering the mold and the appearance of weld seams.
When the injection pressure and speed are too high, injection will occur and weld seams will appear. The speed should be increased, and the back pressure should be increased to reduce the viscosity of the plastic and increase the density. Plastics should be dry well, recycled materials should be used sparingly, and weld seams may occur if the amount of release agent is too much or the quality is not good. Reduce clamping force and facilitate exhaust.
2. Mould:
If there are too many gates in the same cavity, reduce the gate or set it symmetrically, or set it as close as possible to the weld seam. The exhaust at the weld seam is poor, and an exhaust system should be set up. The sprue is too large, the size of the gating system is improper, and the gate is opened to prevent the melt from flowing around the insert hole, or use as few inserts as possible. If the wall thickness changes too much, or the wall thickness is too thin, the wall thickness of the workpiece should be uniform. If necessary, a fusion well should be opened at the fusion seam to separate the fusion seam from the workpiece.
3. Plastic aspects:
Lubricants and stabilizers should be appropriately added to plastics with poor fluidity or heat sensitivity. Plastic contains a lot of impurities, if necessary, replace the plastic with good quality.
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