A Basic Introduction to Injection Molding and 3D Printing

Today, companies have more options than ever to make parts from nearly any material. When it comes to producing parts from plastics, most companies end up choosing either injection molding or 3D printing.

But in reality, injection molding and 3D printing aren’t necessarily competitors, as they both fill valuable market niches and offer unique advantages in certain situations. While both can sometimes produce similar results, the processes they use to manufacture are very different.

So, to help you better understand how they work, their most common applications, and their pros and cons, let’s dive into all about injection molding and 3D printing.

1.Basic Principles

Before we begin analyzing the differences between injection molding and 3D printing, we must first understand the basic principles behind each process. Not surprisingly, since both primarily deal with plastics, there are also quite a few similarities. For example, both are extremely precise and can handle even complex designs and produce perfect parts. This means they can be used in industries such as aerospace and medicine, where even the smallest errors cannot be tolerated.

And, both methods are great options if you need to produce and test a variety of part prototypes at a low cost, which is essential for improving a product or testing its functionality. Ultimately, both can produce similar results and even have overlapping features. However, it is the way they achieve their results that makes the biggest difference. So let’s explore the basic principles of both.

①Injection Molding

As you might guess from the name, injection molding uses molds to form plastic materials into complex shapes.
The necessary plastic materials are mixed in a barrel and then melted into a liquid. They are then injected into the mold, where pressure forces the mold to take on the exact shape of the mold, down to the last detail. After that, the temperature is lowered to solidify the material and production of the next part begins.

This process takes very little time, so a large number of parts can be produced quickly. But before you start the process, you need to design and create the injection mold itself, which is actually the most challenging part of the whole process.

In fact, depending on the complexity of the part you want to make, designing an injection mold that meets your requirements can take weeks or even months. Therefore, you should work with an experienced company that has a well-established injection molding process to shorten the time required. You also need to consider hard molds vs soft molds for injection molding, which are more suitable for small batches, while hard molds are more suitable for large-scale production.

②3D Printing

If the injection molding process revolves around molding plastic until it meets the dimensions and requirements of a part, 3D printing takes a completely different approach, building an object layer by layer until it reaches the necessary shape. Plastic material is added to the previous layer and then immediately bonded, ensuring structural integrity and the ability to withstand various external pressures.

Due to the way 3D printing works, it is able to print the most complex shapes, including internal holes, cracks, or unusual shapes, as long as they do not compromise the integrity of the work. Industries that utilize 3D printing include sports, aerospace, automotive, and even the reconstruction of ancient artifacts.

Just like the injection molding process, there are steps that need to be taken before you get started. That is, you need to design the part through CAD software and prepare the machine for a specific printing job. But with 3D, the process is usually shorter and different options can be tested relatively quickly.

2.Advantages and Disadvantages

So, by now, we have established that the two processes are very similar, but there are also fundamental differences in how they work. So, which one is better? Let’s take a look at some of the main advantages and disadvantages of both to figure this out.

①Advantages and Disadvantages of Injection Molding

Advantages:

1. Efficiency. With injection molding, you can produce a large number of parts in a relatively short period of time, especially when you already have a mold design available.
2. Large-scale production. Because the injection molding process is so fast, you can produce millions of parts quickly and at an affordable cost, as long as your service provider has enough equipment.
3. Durability. Parts made using injection molding have strong structural integrity and can be further strengthened by combining different plastics or adding fillers to the liquid resin.
4. Cost-effectiveness. Once the mold design is perfected, the cost per part is very low, which is why many companies use it for mass production.
5. Excellent details. Although the process is inexpensive, injection molding is still one of the most precise production methods, making it possible to create complex parts and ensure that tight tolerances are met every time.
6. Minimal waste. Due to the unique injection molding process, little or no plastic is unutilized, which means that there is almost no material waste, further increasing the effectiveness of this method.

Disadvantages:

1. Limitations. Although the injection molding process is very versatile, it also has its limitations. Certain angles are more difficult to execute correctly, and the complexity of the project depends largely on the experience, capabilities, and knowledge level of the company you work with.
2. Complex mold making. Before you start production, you need to design and make a mold, which is basically the inverse of the part. This process is not easy and you may encounter various problems along the way, so be prepared to spend weeks or months before you can start using it. If there is a problem with the mold, you will have to replace it, which will consume more time and resources.
3. High upfront costs. You may not find a cheaper production method than injection molding once the process starts, but the initial expenses of designing the mold will increase rapidly. Therefore, although injection molding has also been successfully used for prototyping, it does not always make sense for small-scale production.

②Advantages and Disadvantages of 3D Printing

Advantages:

1. Simple adjustments. Since molds are not required when producing parts with 3D printing, it is very simple to adjust the digital design of the part. If something does not go as you want, just try a different approach and you can see the results almost immediately.
2. Low upfront costs. Unlike injection molding, 3D printing does not require a large upfront investment because all processes until the production itself are carried out digitally on a special software platform.
3. Complex design. Because 3D printing uses a layer-by-layer approach, it can print complex shapes, including cracks and holes, which can be an advantage in some cases.

Disadvantages

1. Small part size. One of the biggest disadvantages of using injection molding software is the relatively small size of the parts you can create. The layering process has its limitations in terms of scaling, which will be difficult to overcome.
2. Defects. While the layering method is effective in some ways, it is also prone to defects in the manufacturing process. This is especially true for surfaces, which often appear ridged and a bit uneven.
3. Slow production speed. In the end, no matter how you look at it, 3D printing is not as efficient as the injection molding process. As you can imagine, it takes time to layer plastic materials to produce even one part, let alone try to produce hundreds, thousands, or millions of parts.

3.How to make the right choice

While both methods have their disadvantages, they also have unique advantages that make them well suited for specific situations. If you need to produce large quantities at an affordable price, injection molding is the way to go. At the same time, 3D printing gives you more flexibility and the ability to quickly adjust your design.
If you don’t have a lot of time and need the part now, 3D printing is better. But if you eventually need to scale up, it makes more sense to choose the injection molding process because the time you spend initially will be compensated in the later stages of production.

Since there are so many determining factors that will influence your decision, it makes sense to work with a company that offers both services and can help you figure out which method best suits your needs. At Xavier, we have a team of experts who can answer all of your questions and provide the most cost-effective course of action to meet our requirements. After all, this is a big decision, so it makes sense to take the time to carefully explore your options.