Injection Molding of Plastics: An Overview

Many industries require injection molded parts, ranging from automotive to medical devices.

While many manufacturers rely on machine tooling to produce their injection molded parts, some choose to invest in injection molding services to reduce costs and increase efficiency.

There are several benefits to investing in injection molding services.

Many companies offer cost savings, increased flexibility, and superior quality.

However, the decision to purchase molding services comes down to choosing the right provider and ensuring you get value for your money.

So, if you want to know more about plastic injection molding, this post is just for you!

What is Injection Molding?

Injection molding is used by many industries, including plastics manufacturing, packaging, electronics, toys, medicine, and auto components.

The injection molding process involves melting a polymer (a material made of long chains of molecules) or compound at a high temperature, injecting it into a closed cavity under pressure, and allowing the melted material to cool and solidify until it forms an object that has the shape of the cavity.

Once the mold is filled with molten resin, the mold opens and ejects the part while still hot, which allows the part to harden immediately.

This method creates very strong objects since the injected material is cooled quickly, causing the molecules to pack tightly together.

Because the process requires only one shot per mold, it can be highly efficient – especially when compared to other techniques such as blow molding.

What is the injection molding process?

To understand how injection molding works, let’s start by looking at what happens during the molding process.

An extruder melts the polymers or compounds to form a liquid.

This liquid is then fed through a heated barrel, where it heats up and becomes a viscous fluid.

Next, the viscous fluid is forced into a steel cylinder called a screw.

The screw moves forward, pushing the plastic onto the bottom of the mold.

After the screw pushes the liquid out of the barrel, the barrel begins to move back towards the machine, pulling the screw along behind it.

As soon as the barrel reaches the top position, it closes and stops. Since the plastic is now inside the mold, the next step is cooling.

Air vents open and close inside the mold during the cooling cycle, gradually releasing heat.

When all the heat has been removed, the mold opens, and the completed product falls from the mold.

Why use the injection molding process?

If you want to achieve good results with your product, you must choose an efficient solution that allows you to produce the desired result in the shortest possible time.

This is precisely why we decided to introduce injection molding, a groundbreaking manufacturing method.

It offers you many benefits and advantages over traditional manufacturing techniques, allowing you to save money while increasing productivity.

The following are some of the main reasons why injection molding is preferable to other technologies:

Advantage of Injection Molding:

There is a wide range of advantages of injection molding, including:

· Reduced cycle time

· High-quality parts

· Lower production costs

· Increased efficiency

· Low cost

· Fast production

· No waste

· Easy maintenance

· Flexible design

· Simple operation

· Small footprint

· Lightweight

· Long life span

Disadvantages of Injection Molding:

There are disadvantages of injection molding too.

· For instance, because the injection molding process involves heating the mold, Warpage has potential.

· Another disadvantage is that injection molding does not allow for much design freedom compared to other blow molding and die casting methods.

· Also, injection molding cannot create complex shapes; therefore, most products have simple geometries.

· Some companies even use different materials depending on the application. For example, injection-molded car bumpers might feature a hard exterior shell protecting against scratches and making them harder to repair.

· On the other hand, injection-molded sports equipment may have a soft outer layer that provides comfort to users.

· In addition, the raw materials required for injection molding are expensive, so they usually need to be bought in large quantities.

What are Different Types of Injection Molding?

There are five main types of Injection Molding.

Let’s explore each of them:

· Thermoplastics Injection Molding:

These are the simplest forms of plastic injection moldings.

They consist of one piece of thermoplastic (a solid form of plastic) injected into a mold cavity to create a final product.

Thermoplastics are often used for prototyping since they can easily reproduce the end product.

Once the prototype has been tested, the thermoplastics can be removed from the mold.

This process is known as demolding. Demolded thermoplastics are easy to handle and recycle.

· Over-Molding:

This means adding an extra component onto the outside of the original plastic object.

It is mainly used to alter the appearance of the final product.

For instance, over-molded plastic bottles are typically more flexible than regular PET bottles.

It is more difficult to remove the over-molding material once added.

However, this technique is ideal if you want a strong bond between your primary plastic part and the secondary one.

Over-molded plastics are commonly made out of PE and PP.

· Insert Molding:

This is when you add an insert inside the main plastic object.

The insert could be another plastic part or a metal component.

With insert molding, you can include features like channels, holes, or grooves on the surface of the original plastic part.

The quality of the finished part won’t be affected as the insert will not melt during the heating phase of the injection molding cycle.

With insert molding, there is no limitation regarding the size of the part because the insert does not touch the inner walls of the mold.

However, inserts tend to cost more than traditional injection molding techniques.

Depending on the complexity of the design, the insert can be made out of any suitable material such as metals, ceramics, glass, composites, paper, wood, leather, rubber, etc.

Insert molding can be used to produce smaller items.

It takes less time to complete the manufacturing process but requires some expertise in designing the insert.

· Cold Runner Injection Molding:

This involves a two-stage process where the plastic part is first shaped and then inserted into a second mold to produce a hollow structure.

The hot runner system heats the molten plastic while it moves through the barrel in the first step.

Then, the plastic flows into a cold chamber.

The air pressure causes the melted plastic to expand.

After cooling, the plastic is ready to go back into the second mold.

This technique only works for certain materials such as PVC, PC, PS, PMMA, and acrylic.

· Hot Runner Injection Molding:

Unlike cold runner injection molding, hot runner injection molding uses external heaters instead of cold chambers.

The heated plastic has to flow continuously through the small tubes without freezing.

As the plastic travels down the tubing, it's heated from the bottom.

When the plastic reaches the end of the tube, it gets ejected from a nozzle.

A mechanism keeps the plastic moving forward until it fills the cavity.

The hot runner method is widely used for producing large parts and thin-walled products.

One example is the production of toys which often require complex shapes.

Why Choose Plastic Injection Molding For Your Project?

There are numerous reasons to choose plastic injection molding for manufacturing parts.

Some of them are mentioned under:

1. Low Cost

Manufacturing industries that aim to cut costs without compromising quality use Plastic injection molding as an excellent way to reduce overall production expenses.

Unlike metal or ceramic mold casting, plastic injection molding is relatively cheap.

2. Easy to Maintain

Compared to cast molds, plastic injection molding isn't difficult to maintain.

Even if you're working with a small amount of raw material, you'll still manage to make a reasonable profit.

3. High-Speed Production

Another benefit of plastic injection molding is its ability to quickly produce a good quality part.

Since plastic injection molding eliminates additional steps like sanding and painting, the entire process can be completed within hours.

4. Higher Quality/Less Waste

Because plastic injection molding requires less maintenance than traditional methods, there's no need for costly replacement or repair.

As a result, you get to save on both labor and money.

Also, since there's no waste produced during the molding process, you don't need to worry about disposing the leftover material.

5. Good Quality Parts

In addition to saving on cost and time, plastic injection molding also produces quality parts.

Due to its versatility, plastic injection molding enables us to produce almost any shape possible.

This is especially true when it comes to creating prototypes.

If your business needs several samples, you'd likely prefer to use plastic injection molding rather than conventional techniques.

So, If you are interested in learning more about injection molding or want to buy our plastic molding injection services, we recommend contacting us today!

We at Boen offer free consultation services, which means that our experts will come to your location and help you with any questions regarding this technology.