3D-printed tools for injection molding: Everything you need to know

As 3D printing continues to develop, the technology is showing growing potential for various aspects of manufacturing, including the production of tools for injection molding. The use of 3D-printed tools for injection molding, while traditionally a complex and time-consuming task, can make prototyping, mold verification and small-batch production more efficient.

However, it is also important to understand the extent to which injection molding and 3D printed tools can impact the additive manufacturing sector. This article gives an overview of what injection molding is, what applications there are and when you should try 3D printed tools for injection molding.

Injection molding is a manufacturing technique that allows detailed parts to be produced in large quantities with precision and repeatability.

In the injection molding process, molten material, often plastic, is injected into a mold or cavity under high pressure. The mold, which is usually made of materials such as steel or aluminum, determines the shape of the end product. As soon as the material is injected, it cools and solidifies in the mold. After the material has hardened, the mold opens and the finished part is ejected and is ready for further processing.

In addition, injection molding is suitable for a range of materials, from common plastics such as ABS and HDPE to more exotic composites such as carbon-filled PEKK or versatile TPUs. This versatility facilitates the manufacture of products with different properties such as strength, flexibility and resistance to heat and chemicals.

Although injection molding has its advantages, its applications for 3D printed tools need to be contextualized precisely. 3D-printed molds are primarily advantageous for prototyping, mold testing and the production of small batches. In certain cases, they can also be used in mass production, but this is not always the best solution.

One aspect where 3D-printed molds can definitely offer advantages is the reduction in lead times. Conventional mold making processes can take weeks or months, depending on the complexity of the design. With 3D printing, this time frame can be reduced to days or even hours, enabling faster turnaround times and higher productivity.

With conventional manufacturing processes, the production of complex geometries can also be difficult and expensive. 3D printing can produce molds with intricate designs without significantly increasing costs, making it a viable option for complex parts in small quantities and for customization in large volumes.

Here are some other advantages of 3D-printed tools for injection molding:

• Lower material costs: In conventional mold making, large metal blocks are shaped into the desired form using subtractive manufacturing processes, which can lead to material waste. With 3D printing, you can produce molds or parts with only the required amount of material and thus significantly reduce material costs.
• Less complex machines: The traditional method of injection molding involves a variety of complex machines for different steps of the mold manufacturing process. With 3D printing, the majority of the process can be carried out with a single 3D printer, significantly reducing the need to invest in multiple machines.
• Eliminate storage costs: 3D printed molds can be created on demand from digital files, reducing the need for significant storage space.

The injection molding process is a systematic sequence of events, a journey from the initial design to the final product.

The first step in the injection molding process is to determine whether your part design is suitable for injection molding. This crucial phase requires a careful evaluation of various factors: the complexity of the design, dimensional tolerances and the planned production volume are all crucial aspects that need to be taken into account.

Not all designs are suitable for injection molding. Specific geometries and undercuts can complicate the mold making process and low production volumes may not justify the initial investment required to produce the molds. Therefore, conducting a feasibility study of the design is essential to ensure that it is well suited for injection molding.

In the second step, the mold is created. The mold is the negative of the end product and is typically made of steel or aluminum.

In the third and final step, the mold is filled with the selected material. In this step, the material is first heated until it reaches a molten state. The molten material is then injected into the mold under high pressure.

Once the mold is filled, allow the material to cool and solidify. Once the part has hardened, the mold is opened and the newly formed part is ejected.

Injection molding is not a uniform process. There are different types, each with unique characteristics, advantages and disadvantages.

Freeform injection molding (FIM) is a new technology developed by Nexa3D that combines 3D printing with injection molding: it accelerates injection molding by 3D printing the molds into which the materials are injected. Nexa3D is a pioneer in 3D printed tooling, helping users additively manufacture complex injection molds in hours instead of weeks or months.

This is how it works:

• Free-form injection molding begins with a CAD file of the part to be molded.
• The design is converted into a mold – a process that is accelerated by automated software called a “mold generator”.
• The user evaluates the shape design and can quickly make changes and iterate new versions if the first version is not satisfactory.
• As soon as the shape is satisfactory, it is 3D printed and reworked.
• The injection molding process can then begin.

The XiPPro industrial 3D printer from Nexa3D is a great option for printing injection molds. Due to the size and speed of the XiPPro, FIM is now many times faster and can be operated on a truly industrial scale.

With freeform injection molding from Nexa3D, a design can go from file to finished part within 24 hours. On average, the entire iteration cycle takes about one to three days – and can be tens of thousands of dollars cheaper than if the tools had to be ordered elsewhere.

Advantages:

• Molds can be produced quickly and cost-effectively
• Ideal for complex designs and geometries
• Enables simple design changes

Disadvantages:

• Not as durable as conventional molds
• Limited production capacity
• The choice of materials for molds is limited

Best for:

Freeform injection moulding is best suited for projects that require a high degree of customization and design complexity, especially for prototyping and small batch production. The speed and adaptability of this method make it ideal for industries where design iterations are frequent and timeframes are tight.

Learn more about FIM

Conventional injection molding has been the industry standard for many years. It uses a high-pressure injection system to press molten material into steel or aluminum molds. These molds are produced with a negative image of the desired part.

Advantages:

• High repeatability and consistency
• Suitable for mass production
• A wide range of materials can be used

Disadvantages:

• High up-front costs for mold production
• Not very suitable for complex geometries
• Changes to the mold can be time-consuming and costly

Best for:

Conventional injection molding is best suited for projects that require large production runs. It is ideal for producing identical parts with high precision and quality, especially when the design is relatively simple and the production volume can justify the increased initial investment.

In 3D-printed plastic injection molding, a 3D printer is used to create the mold. In certain cases, this method can potentially reduce time and cost compared to traditional mold making, especially for complex designs. However, most methods are only compatible with a few polymers and do not necessarily lead to consistent results. Freeform injection molding is a much better option when speed, accuracy and broad material compatibility are important.

Advantages:

• Faster and more cost-effective mold production
• Flexibility for design changes
• Ideal for mold verification and prototyping

Disadvantages:

• Not as durable as conventional molds or FIM molds
• Limited to the use of a small number of thermoplastics
• Lower production volume compared to conventional methods

Best for:

3D-printed plastic injection molding can be particularly effective for prototyping. Given the flexibility that 3D printing technology can offer in these circumstances, this can also be a viable option if the design needs to be changed frequently.

3D-printed metal injection molding combines the advantages of 3D printing with the benefits of metal injection molding tools. In this process, metal powder is used to produce the mold. Utilizing 3D printing can enable performance-enhancing features such as conformal cooling channels for optimal performance.

Advantages:

• Can produce highly complex and durable molds
• Faster production times compared to conventional metal forming
• High precision and attention to detail

Disadvantages:

• Higher costs compared to plastic 3D printing
• Requires post-processing to remove the binder
• Limited to powdered materials

Best for:

3D-printed metal injection molding is well suited to industries that require robust, durable parts with complex geometries, such as the aerospace and medical sectors.

If you need to produce an extremely large quantity of parts from a variety of materials, using the traditional injection molding process is probably best. However, if you are making prototypes, checking molds or carrying out a low-volume manufacturing project, 3D printed tools can make the process more cost-effective and efficient.

This applies in particular to the use of FIM. Free-form injection molding combines the specific advantages of 3D printing technology with the proven efficiency of traditional injection molding.

With Nexa3D, free-form injection molding is faster, more cost-effective and more sustainable. It offers 15% of the cost, 12% of the time and a 75% reduction in carbon emissions compared to conventional steel tools.

Learn more about FIM