Is injection molding additive manufacturing? This is a frequently asked question, especially from those new to manufacturing sectors. Injection molding is a widely used process that involves melting material and making products of desired shapes. What makes this molding process stand out is its precision and speed.

Interestingly, the additive manufacturing process has many similarities with injection molding. Both are precise, fast, and reliable. This creates confusion in people and leads them to believe that both are the same. However, injection molding is not a form of additive manufacturing. In this article, I’ll discuss injection molding and its differences from additive manufacturing.

Overview of Injection Molding

Let’s first discuss injection molding before discussing whether it is an additive process.

Injection molding is a modern production process. It involves the melting of raw materials (such as rubber or plastics). The molten material is poured into a mold of a specific shape. This molten material cools and solidifies inside the mold. The molten material adopts the shape of the mold during the solidification or curing phase.

The shape of the mold plays a crucial role in the injection molding process. Its shape must be precisely similar to the desired shape of the product. Once the molten material solidifies, it assumes the desired shape. It is then ejected using the specialized injection pin present inside the mold. There are various types of injection molds, each with distinct properties.

Injection molding can utilize a wide range of materials and involves melting them to form a liquid state. Additionally, this process is known for its precision and speed. You can create hundreds and thousands of identical parts in no time. Manufacturers use dedicated injection molding machines to complete this process. You can even make complex shape parts once you have a mold of that shape.

Is Injection Molding Additive Manufacturing?

No. Injection molding is not an additive manufacturing process.

Additive manufacturing is synonymous with 3D printing. It is a process where products are made by adding materials layer by layer. This process involves direct cutting or machining. Materials layers are made with precision to create new materials. In this process, material is added in layers.

The injection molding does not involve the addition of materials in layers. Instead, this process involves melting the raw materials. This molten material is poured into a mold, where it solidifies. The solid part from the mold is ejected using the ejection pin. This process does not add material. So it does not fall in the additive manufacturing category.

Instead, it is a subtractive manufacturing process. Additive manufacturing, also known as 3D printing, is performed using 3D printing technology. These printers work by using computerized instructions and make parts with precision. However, the injection molding process is manual and inexpensive. Its precision also depends on the shape of the mold.

Difference Between Injection Molding and Additive Manufacturing (3D Printing)

Both injection molding and additive manufacturing processes differ from each other. The injection molding process makes parts by melting the material and filling it into the mold. 3D printing is unique in that it creates parts by adding material in layers.

In this method, the shape of the part you need is made using CAD software. This CAD file (design) is fed to the 3D printer. The computerized system of printers analyzes the design. After that, the printer head begins to move and creates a layer according to the automated instructions. After one layer is added, another layer is added, and this process continues.

This addition of layers one over another is done according to computerized instructions. This results in high-quality 3D parts and products that are precisely similar to the desired shape (as specified in the CAD file). There are many differences between injection molding and 3D printing. In the section below, I will make the distinction between these manufacturing processes.

1- Subtractive vs Additive Manufacturing

As I mentioned earlier, injection molding involves melting the material. The molten material is then poured into a mold to make the final part. In this process, the initial material (rubber or plastic) is cut and melted.

This removal or shaving of material makes injection molding a subtractive process. On the other hand, 3D printing is a form of additive manufacturing. It creates high-quality 3D parts by adding materials layer by layer. One layer goes on top of the first layer. This layer formation makes the final part. As the material is added in this process, it is an additive process.

2- Material Compatibility & Waste

Injection molding is a versatile manufacturing method. It is compatible with a wide range of materials. These include rubbers, plastics (of all types), resins, and metals. Additionally, this process does not waste material during production. The molten material is filled into the mold with perfection.

No leakage of waste material happens in injection molding. Contrarily, additive manufacturing (3D printing) has limitations regarding material compatibility. It can be made from soft materials, such as resin or plastics. Its working is not smooth when it comes to metals or hard plastics. Additionally, it can result in material waste compared to injection molding.

3- Design Flexibility & Speed

An injection mold is inferior to additive manufacturing in terms of flexibility. Why? This process uses injection molds to produce parts. This mold is specifically designed for the part’s shape. The engineer designs the mold in the first step before starting production. Once mold is made, it is used to make thousands of identical parts.

However, if you need any design changes, they cannot be made. You’ll need to create a new mold from scratch for the new design. This is a big drawback that limits the design flexibility. On the flip side, additive manufacturing is more versatile. The 3D printer works by interpreting given instructions. You can design in a CAD file and resubmit it to the printer for printing.

The printer will use a new design and produce a modified shape. So, additive manufacturing offers more flexibility. When it comes to speed, injection molding is far ahead. It can create identical parts in bulk quickly. On the flip side, additive manufacturing(3D printing) are slower processes. It produces products by adding layer after layer, which slows down the production process.

4- Lead Time & Production Volume

Lead time and overall speed are two different parameters. Lead time refers to the time taken to start from even preparing the machine. On the other hand, speed is generally used to measure the rate at which a production process occurs. Both of these processes differ in terms of lead time and overall speed.

Injection molding has a long lead time but high speed. Why? Because this process uses an injection mold. Creating this mold is a challenging task that consumes time. So, this initial step increases the lead time. On the other hand, additive manufacturing does not use a mold. A CAD file is all this process needs to make the desired shape parts.

When it comes to production volume, injection molding is the superior option. Why? It uses a single mold and can produce hundreds of identical parts. Large-scale manufacturers prefer injection molding as it produces high volumes of products quickly. On the other hand, 3D printing is slow and is ideal for prototyping and small-scale production.

5- Precision & Strength

I consider injection molding a better option when it comes to precision. The reason is that this process produces parts with consistent quality. For example, you make 100 parts in one production cycle. All of these parts will have the same finishing and quality. Additionally, mold used in this process is designed in high-end software.

So, you get the part that is precisely the same as the mold. The reason is that mold design is made by computerized software. The mold shape is 100% identical to our desired part shape. These molds, when used in injection molding, enable us to produce accurately shaped parts. This process also creates a strong and durable material by using high pressure and moderate temperature inside the mold.

On the other hand, additive manufacturing lags when it comes to precision. You’ll see prominent lining on the parts made with this process. The layer-by-layer formation affects surface smoothness. You’ll need post-processing to get a smooth surface. The parts made with this material are strong and durable.

6- Cost & Upfront Investment

The injection molding process requires a high upfront investment. Why? Because this process depends on the injection mold. You’ll have to make a mold first before starting the injection molding process. Designing and creating the mold is a very costly process. In fact, it can take hundreds of dollars if your shape is very complex.

Once the mold is made, the cost per part decreases significantly. You’ll be able to produce thousands of identical parts without needing to remake the mold. This makes the injection molding process cost-effective in the long run. Conversely, additive manufacturing (3D printing) is more cost-effective and requires no upfront investment.

All you need is material and a 3D printer to start production. However, this process is very slow and takes more time, affecting its cost-effectiveness. The 3D printer will consume more electricity as it will run for an extended period. I consider additive manufacturing suitable for one-off items or small batches. On the other hand, injection molding is cost-effective and ideal for bulk production.

Frequently Asked Questions

What type of manufacturing is injection molding?

Injection molding uses a material to make custom parts. The material undergoes removal and shaving to make parts. This makes injection molding a substractive process.

What is the difference between injection molding and additive manufacturing?

Injection molding is a subtractive process that involves melting the material to create parts. It uses a mold during its operation. Additive manufacturers make parts by adding materials in layers. This process does not use mold and uses specialized 3D printers.

Can 3D printing replace injection molding?

No. Both 3D printing and injection molding offer unique value. They fit different manufacturing needs. 3D printing is used for small-scale production. Injection molding is ideal for large-scale production.

Concluding: Which One Should You Choose, Injection Molding or 3D Printing?

It is noteworthy that 3D printing and additive manufacturing are often used interchangeably. They are used interchangeably. When it comes to injection molding vs 3D printing, individual preferences matter the most. I recommend choosing injection molding for most production needs. This process uses a wide range of materials and can make strong parts. Additionally, this process is fast, inexpensive, and does not result in material waste. However, 3D printing is a suitable option for small production needs.

In summary, injection molding is not a form of additive manufacturing. Instead, it is a subtractive process, involving the removal or shaving of material. There are many differences between injection molding and additive manufacturing (3D printing). Choose between 3D printing and injection molding based on your project’s needs.