Inner Thread Bottle Cap Mould Design

There are two types of plastic product threads: external and internal. The push-out device called the slider typically forms the external thread. The processing expense is less than that of the rotary dethreading apparatus. 

The internal thread is typically formed by mould dethreading with an automatic dethreading device, which is highly efficient and simple to implement. Mass production is compatible with automation.

The design of bottle caps is an important aspect of the production process. To ensure a smooth and leak-free experience for the consumer, the cap must fit snugly on the bottle. 

The inner thread mould must be carefully designed to create a snug fit without any gaps or spaces that could allow liquid to escape. In this blog post, we will take a closer look at the inner thread mould, and its working principle and discuss some of its design phases.

Inner thread bottle cap mould design

Inner Thread Bottle Cap Mould Design

Figure 1. Inner thread bottle cap mould

Inner thread bottle cap mould is a type of mould that features an inner thread. This mould is specifically designed to create the threaded portion of a bottle cap. The advantage of using an inner thread bottle cap mould is that it provides a more consistent and accurate finish than if the threads were cut by hand. 

In addition, inner thread bottle caps are less likely to strip or cross-thread when screwed on or off. As a result, they provide a smoother and more reliable closure for bottles. This allows for a tight seal on bottles, preventing leakage and ensuring that your product stays fresh. 

A well-designed mould can play an essential role in the success of your business. The right design can help ensure that your products are of high quality and produced quickly and efficiently. 

In addition, a well-designed mould can also help to reduce the cost of production. When choosing a design for your inner thread bottle cap mould, it is vital to consider the type of product you will produce, the production volume, and the desired level of quality. 

Inner thread bottle cap moulds are available in various designs to suit your needs and can be customized to fit any size or shape of the bottle. Whether you need a standard inner thread or a custom design, a bottle cap mould is available to meet your requirements. 

Here is our guide on shampoo bottle cap moulds to understand more about cap moulds.

Design phases of inner thread bottle cap mould

The design of the mould for the inner thread bottle cap is divided into three phases.

Phase 1- Design of automatic unthreading mechanism

The automated unthreading mechanism has been designed to quickly and easily remove the thread from various objects. The bottle cap is suitable for the in-mold rotation method of automatic unscrewing. 

The rotating mechanism is typically powered by electric motors, hydraulic motors, cylinders, and mould-opening stroke drives. When the hydraulic and cylinder are the power sources, the rack must be used in conjunction with them. 

When the mould is opened, the hydraulic cylinder moves the rack, which rotates the gear, causing the threaded core to turn and dethread. When the mould is closed, the hydraulic cylinder drives the rack, which drives the gear, causing the reset of the threaded core. 

When a motor is used as the power source, the motor is typically used to drive the sprocket, which operates the gear transmission, causing the thread core to rotate and unthread. 

To ensure the accuracy of the thread, this type of mould can be equipped with a travel switch that precisely controls the position of the tooth shape and prevents thread tail pulling. 

To ensure the gear’s strength, the diameter of the addendum circle must be greater than two times that of the shaft, and the gear’s surface must be treated with high-frequency quenching. 

To prevent the same position from affecting the gear’s durability each time it meshes, the number of teeth on the two gears that mesh should not be equal.

Phase 2- Design of gating system

The gate is the opening in the mould through which the molten plastic is injected to fill the cavity. The gate location, design, and size are all critical factors that must be carefully considered to produce a high-quality moulded part. 

A pointed gate pouring system is incorporated into the mould. The melt enters the cavity from the top center of the cap, which promotes an even distribution of the filling. 

The slight gate trace ensures the appearance of the plastic parts, and the mould opening process enables the pouring system to condense and produce plastic parts. Automatic shutoff increases production efficiency and simplifies the structure of the mould.

The gate must be located so that it is not visible on the finished part and must be designed to minimize the amount of flash (excess plastic) produced. 

The size of the gate also needs to be carefully considered, as a too-small gate can result in a plugged nozzle, while a too-large gate can cause excessive material flow and sink marks. 

Phase 3- Design of the punch and die

The punch is a cylindrical tool with a point at one end and a blunt end at the other. The die is a similarly shaped tool with a hole in the center slightly smaller than the punch. 

The punch is inserted into the die and rotated to create the threading on the bottle cap. The rotation creates friction, which heats up the metal and allows the punch to slowly sink into the die. As it does so, it forms a spiral groove that matches the internal threads of the bottle cap. 

With each rotation, the spiral becomes deeper until it eventually reaches the desired depth. Then, the punch is withdrawn from the die and cooled so it can be used again. Thanks to this design, an inner thread bottle cap can be created with high precision

Working process of the mould

Figure 2 Working Process of the Mould

The hydraulic motor is employed through the chain drive and gear drive to perform automated unthreading. When the mould is closed, the plastic melt is injected via the nozzle into the mould cavity, and the injection moulding process is completed through the processes of mould filling, pressure holding, feeding, cooling, and setting.

The whole procedure for opening moulds has been separated in half. When the mould is opened, the moveable section of the mould travels in reverse. Under the operation of the moving mould, the fixed template travels with the moving mould in reverse.

Sub-parting; while the movable mould component continues to travel backward under the influence of the tie rod limiter, the fixed plate and the push plate is subdivided, and the motor drives the sprocket and drives the drive shaft to spin through the chain drive.

The matching driven gear is rotated, and the driven gear, in turn, rotates the threaded core. Under the influence of the bottle cap’s anti-rotation construction, the side of the thread core spins, and the side of the plastic component travels axially, allowing the inner thread of the plastic component to be extracted.

To create the threads on the bottleneck’s inner wall. This is accomplished by rotating a die inside of the mould to form the thread grooves. Air is blown into the mould to create the base of the cap.

The inner thread bottle cap mould is an essential piece of equipment for any company that produces bottles with internal threading. Without this mould, it would be challenging to manufacture screw-on-cap bottles. The inner thread bottle cap mould’s operation is very straightforward but needs accuracy and attention to make high-quality products.

If you want to learn, here is a guide on injection moudling.

Conclusion-Inner thread bottle cap mould

An injection mould with automatic unthreading is perfect for bottle caps with internal threads. The inner thread bottle cap mould design is a three-phase design process. The first phase designs the automatic unthreading mechanism, the second phase designs the gating system, and the third phase designs the punch and die.

The top of the point gate is used for pouring, which improves the surface quality of the product; the punch is designed as a single insert, and with the “motor + chain + sprocket + gear” transmission mode, the automatic demoulding of the internal thread is realized, which can avoid the efficiency of a manual thread removal. 

The unthreading mechanism, gating system, and punch and die must all be designed precisely to ensure a smooth working process. With proper design and implementation, an inner thread bottle cap mould can provide many benefits, such as increased productivity and shorter production cycles. 

Go4 mould is a high-quality manufacturer of plastic cap moulds. With over a decade of experience in the industry, we have the knowledge and expertise to produce inner thread bottle cap moulds to the highest quality standards. 

We use the latest technology and state-of-the-art equipment to manufacture our moulds, and our team of skilled technicians can create inner thread bottle cap moulds to meet your specific requirements. Contact us today to discuss your needs or request a quote.

Scroll to Top