The molten plastic in the cavity meets in the form of multiple strands due to the intrusion of the insert holes, the inconsistent flow rate, and the region where the filling flow is interrupted, and a linear weld seam is produced because it cannot be completely fused. In addition, in the case of gate injection molding, a welded joint is formed, and the strength at the welded joint is poor.
1. Processing:
1. The injection pressure and speed are too low, the barrel temperature and the mold temperature are too low, causing the melt entering the mold to cool prematurely and the weld seam appears.
2. When the injection pressure and speed are too high, there will be a spray and a weld seam will appear.
3. The speed should be increased, and the back pressure should be increased to decrease the viscosity of the plastic and increase the density.
4. The plastic should be dried well, and the recycled material should be used less. If the dosage of the release agent is too much or the quality is not good, the welded joint will appear.
5. Reduce the clamping force and facilitate the exhaust.
2. Mold aspect:
1. If there are too many gates in the same cavity, reduce the gate or symmetrical setting, or set it as close as possible to the fusion joint.
2. Exhaust system at the weld joint is poor, and an exhaust system should be installed.
3. If the sprue is too large and the pouring system is not properly sized, the gate should be opened to avoid the flow of the melt around the insert hole or to minimize the use of inserts.
4. If the wall thickness changes too much, or the wall thickness is too thin, the wall thickness of the part should be uniform.
5. If necessary, a fusion well should be opened at the weld seam to disengage the weld joint from the part.
3. Plastics:
1. Lubricants and stabilizers should be added to plastics with poor fluidity or heat sensitivity.
2. Plastics contain a lot of impurities, if necessary, change the quality of the plastic.
