First, defects in mold design result in bubbles in injection moulds.
For example, the injection mold gate position is not good, the gate is too small, the gate of the multi gate is asymmetrical, the runner is fine, the mold cooling system is not reasonable so that the mold temperature difference is too big and so on cause the melt flow discontinuous in the mold cavity, blocking the air channel.
Secondly, the mold parting surface lacks the necessary exhaust channel or exhaust channel insufficiency, blockage, poor position, and there is no inlay, thimble and other machining gap exhaust, causing the air in the cavity can not leave at the same time when the plastic is entered. These reasons can also lead to bubbles in injection moulds.
Finally, if the surface roughness of the injection mold is poor, the frictional resistance is large, causing the local excessive hot spot, so that the decomposition of the plastic will also cause the appearance of bubbles.
Of course, in addition to the cause of mold, there will be equipment, technology, material and other reasons, so in the manufacturing process of injection mold, every process needs to be very careful, to avoid the occurrence of bubbles in the injection mold, reduce the bad rate in the production process, in order to compete increasingly. The fierce competition in mold industry has increased the competitiveness of injection mold manufacturers.