Using 3D Printed Molds for Low-Run Injection Molding


Injection molding is the commonest method of mass production of plastic parts. It is particularly ideal for producing large plastic parts with high tolerance. In the past, 3D printing was applied in designing and manufacturing process only for prototypes verification.

Today, the technology has advanced so much to allow 3D printers to be used directly in molds creation. In this post, we look at the main advantages of using 3D printing when manufacturing injection molds. We also provide the best design practices when using 3D printers to come up with printed injection molds.

What exactly is injection molding?

This is a process of designing a component by injecting the melted material into a die under pressure. The molten material fills predesigned cavities and finally cools to take the shape of the respective solid part.

To keep the associated costs low, every plastic injection molding company targets automating the process. The best parts to make using injection molding are those made with thermoplastics. However, it can also be used with thermosetting plastics.

Notably, the high cost associated with injection molding makes it only ideal for high volume production. However, when it comes to producing low volumes (10-100), the process becomes financially infeasible. This makes 3D printing the perfect alternative to keep the cost low without compromising on quality.

Benefits of using 3d printed molds

When a plastic injection molding manufacturer is working on a mold, the production team must determine whether it will be used to make just 30 parts of 50,000 parts. In the past, molds needed to be CNC machined to guarantee highest possible tolerance. The metal provides better wear resistance from the repeated injection, opening and closing of the mold, and temperature gradient.

If you are working on a low-run mold, the wear resistance ceases to be a critical factor. This makes 3D printers a perfect option for designing parts with top-notch accuracy. When you couple this with special temperature-resistant 3D printing materials, it means that 3D printed molds are a viable option especially for low-run injection mold designs.

The main benefits of using 3D printing in injection molding include;

  • Faster turnaround or about 1 week (compare this to the standard 5-7 weeks).
  • It is applicable where the overall production quantities are very low (about 20-150 parts).
  • It is the best alternative where mold design changes or alterations are highly probable.
  • 3D mold printing is more viable when the sections involved are very small (approximately <150 mm).

The two main configurations of 3D printed injection molds

3D printed injection molds are designed using two standard configurations.

  • The molds insert in aluminium frames: This is the common configuration, and it is used to produce parts with high accuracy. The model is printed using a 3D printer and then inserted into a frame made from aluminium. The frame provides the support against heat and pressure from the injection nozzle and molten plastic. The frames are also very useful in preventing warping.
  • The stand-alone type: In the stand-alone mold configuration, the mold is only 3D printed without using an additional aluminium frame. This means that additional cooling channels can be included in the mold. Most companies use additional 3D printing materials to prevent warping and damage to the parts.

Materials for designing 3D printed injection mold

The right material for designing a 3D printed injection mold should have the following qualities;

  • Extra tough/stiff: Because the part will be removed repetitively, it is likely to rapidly wear the mold. The selected material should, therefore, be very stiff to guarantee mold accuracy over time.
  • High-temperature resistance: The best material should have a high-temperature resistance to withstand both thermal and mechanical loads applied during injection.
  • High level of detail: One critical requirement of any injection mold material is high dimensional accuracy. The material you pick should have a smooth surface to guarantee a better mold and attractive finish for all parts.

When it comes to 3D printed injection molds, the main focus should be picking the best mold maker such as Sosital plastics. Top notch companies not only understand the process, but ensure that clients get the best support, and use the right materials to keep the cost as low as possible. Remember these rules of the thumb when it comes to 3D printed injection molds.

  • 3D printed injection molds are the most cost-effective when working on low-run injection molding.
  • The ideal technologies for 3D printing injection molds are SLA and Material Jetting.
  • Every 3D printed mold can be used for about 30 to 100 rums (depending on the material used).
  • Using wider draft angles (more than 2o) and an appropriate release compound can help to increase the mold lifetime.