Because the ball is solid plastic BB plastic ball roundness, in the molding process, the most prone to poor quality that there will be a bubble, the main reason is the solid plastic ball if the large diameter of the cavity in the air will be wrapped in the center of the ball, because the air in the cavity in the mold or by the reason of the injection speed, not discharged to the outside of the die, so these gases or in the plastic ball outside, forming a gas bag inside the plastic lines, BB ball, on the formation of pores, to make plastic ball to improve air hole in the center of BB, in addition to make the corresponding exhaust in the mold on the outside, but also in the when the injection injection speed adjustment to a reasonable amount, injection speed injection molding machine generally takes half of the fastest numerical can, like the Haitian injection molding machine, injection speed is the fastest 99 is basically the injection Speed to 50-60, the mold made exhaust position, injection speed adjustment of injection molding machine and injection molding, plastic ball basically BB middle bubble problem can be completely solved.