On the surface near the gate of rigid plastic parts such as PS, dense corrugations are formed with the gate as the center, sometimes called shock lines. The reason is that when the melt viscosity is too large and the mold is filled in the form of stagnant flow, the material at the front end will quickly condense Plastic household mould/mold and shrink as soon as it contacts the surface of the cavity, and then the melt will expand and shrink the cold material to continue the process.
The continuous alternation causes the material flow to form surface vibrations as it advances. Solution: (1) Increase the barrel temperature, especially the nozzle temperature, and also increase the mold temperature. (2) Increase the injection pressure and speed to quickly fill the cavity. (3) Improve the size of runners and gates to prevent excessive resistance. (4) The mold exhaust should be good, and a large enough cold slug well should be set up. (5) Do not design the parts too thin. Analysis of the causes of swelling and blistering of injection molded products Some plastic parts will soon appear swelling or blistering on the back of the metal insert or in particularly thick parts after molding and demolding. This is because the plastic that has not completely cooled and hardened releases gas and expands under the action of the internal pressure penalty.
Solution: 1. Effective cooling. Reduce mold temperature, extend mold opening time, and reduce material drying and processing temperature. 2. Reduce the filling speed, reduce the forming cycle, and reduce the flow resistance. 3. Increase the holding pressure and time. 4. Improve the situation that the wall surface of the part is too thick or the thickness changes greatly.
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