Most of the mold companies will choose the hot runner valve gate for the preform mold, which is pneumatically controlled, and there will be no tail on the preform, which saves more labor costs. Valve gating system performance is also more stable. It is also the best choice for fast cycle times.
Most mold companies are hot runners that make PET mould themselves, which is not common in China. By making hot runners themselves, they can also better control the quality and price of hot runners. However, a stable operation of hot runners requires a high degree of mentality and sophisticated equipment. Therefore, the company needs a huge investment in mold equipment.
Internal threads are usually found in PET moulds but can also be designed in many technical products such as plastic pipe hardware. The planned manufacturing method (molding or post-molding processing) should be considered. If the lid is threaded after molding, the lid mold can be simpler (and less costly) and the designer should understand the amount of production required. As we said before, achieving the lowest total cost product is more important than the most elegant manufacturing method. If the thread must be formed, we have two options again: how to remove the product from the core: by unscrewing or peeling.
The plastic cover mold designer must consider whether the plastic cover can be peeled off the threads. Peeling is the simplest (usually the lowest cost) solution for ejecting the top cover or closer to the top cover; however, the ease of peeling depends on many equally important factors.
The peeling theory is very simple. As the cap mold opens, and after the cavity moves away from the side of the core, the ejection caused by the forward movement of the stripper begins. In doing so, the plastic cap is pushed onto the hump of the core; this causes the plastic to expand so that the part inside the core inside the groove may slide out of the groove.