(1) the sprue release difficulties in the process of corrugated pipe extrusion, the sprue sticking in the sprue set, not easy to come off,. When the mold is opened, crack damage occurs in the bellows product. In addition, the operator must use the tip of a copper rod to knock out from the nozzle to loosen it before it can be demolded, which seriously affects the production efficiency. The main reason for this kind of failure is the poor finish of the gate cone hole and the scar in the direction around the inner hole circle. Secondly, the material is too soft, after a period of time after the use of small sections of the cone hole deformation or damage, as well as the curvature of the spherical surface of the nozzle is too small, resulting in the sprue material here to produce willow head. The conical hole of the sprue set is difficult to process, and standard parts should be used as much as possible. If you need to process by yourself, you should also make or buy special reamer. In addition, it is necessary to set up the sprue pulling rod or sprue ejection mechanism.
(2) Damage to the guide pillar The guide pillar mainly plays a guiding role in the bellows mold to ensure that the molding surface of the core and the cavity do not touch each other in any case, and the guide pillar can not be used as a force member or positioning parts. In the following cases, injection, moving, fixed mold will produce a huge lateral offset force: ① bellows wall thickness requirements are not uniform, the material flow through the thick wall of the rate is large, where a greater pressure; ② bellows side asymmetric, such as the ladder parting surface of the mold, the opposite sides of the counterpressure is not equal.