Making plastic injection molds with 3D printing

The reason for 3D printing?

It is very important to get a piece that is going to be made with a plastic injection mold – 20 or 20 thousand. In the previous method only created delicate plastic injection molds using CNC machines for fine cutting of metal (steel or aluminum). These materials have very good resistance and are all capable of reproducibility, opening and closing and being exposed to multiple temperatures. In contrast, forming a metal mold is very costly.

For plastic injection, circulation below high resistance and reproducibility no longer plays an important role. Special 3D printing technologies such as SLA, material jetting and polyjet polyjet can make parts with high concentration and completely polished surface. These technologies can be used as a desirable item to create the following circulation plastic injection molds with the first developed heat resistant materials and high freedom that they leave in the hands of the designer. Another application of plastic injection molds is to use them as an important mold example. Prototyping the mold before creating it with metal reduces the risk of depositing on it to several extent.

3D printing templates are used for the following purposes:

High speed formed piece (1-2 weeks vs. 5-7 weeks)
Plastic injection of the following circulation (50-150 pieces)
When there is the ability to change the format
Very small parts (smaller than 150 mm)

3D printing plastic injection mold shapes

There are two types of plastic injection molds that can be created with a 3D printer:

Molds that are installed in aluminum frames: This type of 3D printing mold is the most common type of plastic injection and makes very precise parts. The mold is formed with a 3D printer and placed inside an aluminum frame. This box makes the mold resistant to pressure and temperature changes. The aluminum frame also prevents the transformation of the face and the warping of the mold due to excessive use.
Stand Alone molds: In this case, the plastic injection mold is completely composed of a 3D printer and an aluminum frame is not used in the process. In this case, fine cooling nets can be placed inside the mold. Plastic injection molds made using this method use more raw materials in the 3D printing process and the cost of forming them is higher. The probability of warping and changing the face of these molds with high use is high.

A 3D plastic injection mold is installed inside the aluminum frame.

Implementing a 3D printing plastic injection mold

Raw materials

A good raw material for 3D printing of plastic injection molds should have the following characteristics:

High thermal resistance – One of the most important features that a plastic injection mold should have is the high temperature of transformation of the face, this first material should be able to withstand the thermal and mechanical forces that enter it during injection. Note that the gas bed temperature decreases as it solidifies.
High Suffering and Strength – Opening and closing the mold and using it too much will cause the plastic injection mold to wear and check. In order to prove the mold’s attention at the opportunity, the first material must have high hardness and strength.
High level of detail – One of the most important features that a plastic injection mold should have is the high dimensionality and polished surface. Fine molds can make delicate pieces of construction.

3D printing technologies that can accommodate these specifications are the two technologies of 3D printing SLA and material jetting or playjet. These 3D printers can build parts with very high concentration and are very desirable for forming fine details. Special materials are also available for these technologies that can make a good effort under the name of plastic injection mold. Raw materials such as formaldehyde heat-resistant resin are ideal for SLA 3D printers and Digital ABS resin for 3D jet printers is ideal for plastic injection. The properties of these raw materials and their comparison are given in the table below.

If you have an industrial application, a home SLA 3D printer may not be very desirable for you. A fine comparison between the two most desirable 3D printing materials for plastic injection molds – Digital ABS and PerFORM from Somos – can be seen in this section of the 3D printing school.

A 3D printing plastic injection mold with Digital ABS material

Plastic injection mold application

In this section, we will discuss how to implement a plastic injection mold using a 3D printer. Technical impregnation of a plastic injection mold is a specialized activity and learning it perfectly is not included in this scientific article. Of course, if you have experience in impregnating a plastic injection mold, this section will help you in deploying a mold for 3D printing.

When printing 3D plastic injection molds, it is better to observe the following points:

When unpacking the template for SLA 3D printing, use the orientation of the template when printing so that its inner surface is not in contact with the support. This increases the surface quality of the part and significantly reduces the need for post-printing steps.
Placing shallow air vents (less than 0.05 mm) from the sides of the mold to the sides of the cavities can direct the air trapped in the part to the outside.
If the print format is three