Analysis of plastic bottle cap threads

Analysis of plastic bottle cap threads

1. Rotating deep thread

1. During the injection molding process, there is a rotating equipment system in the mold. This action can effectively protect the integrity of the bottle cap screw thread. Therefore, the thread shape of the bottle cap can be effectively controlled, and the cap wall will not tilt when rotating the thread of the upper bottle shank.

2. During the capping operation, when the bottle cap is rotated onto the bottle shank thread, it can be converted into a vertical force to tighten the bottle gasket against the bottle shank.

3. Since the threads of the rotating teeth cannot effectively prevent the bottle cap gasket legend from falling off, glue is added to the threaded cap when adding the gasket.

4. Rotating deep threads have the following defects:

A. It is not ideal to add multiple pads to this type of thread.

B. The threaded cap restricts the design of the bottle cap (for example, the bottle cap with blocked threads cannot be rotated in the mold). Of course, threaded cap molds are more complicated to design and more expensive to produce.

C. There is no restriction on the selection of raw materials when making deep thread bottle caps.
2. Forced removal of shallow threads

1. During the injection molding process, the bottle cap can be easily demoulded from the mold without the need for mold rotation. Obviously, when designing the threads of the bottle cap, the threads must be shallow to allow “forced removal” during the injection molding process, and the threads must be moderate enough to cover the bottle shank threads perfectly.

2. It is not necessary to add glue when adding a liner to the force-removing threaded cap. The liner can be effectively restrained by the thread, making the bottle cap gasket legend less likely to fall off.

3. When it is necessary to add multiple layers of gaskets to the cap or to carry out various possible designs for the cap (such as bottle caps with blocked threads), forced thread removal is the first choice.

4. The forced removal of threaded caps has restrictions on raw materials during the injection molding process, among which polyethylene and polypropylene materials are popular choices.