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Published on April 14, 2017

3D Printing for Injection Molding

  • 3D printing and injection molding are now being used in combination.
  • In some cases 3D printing can reduce the cost of injection molds or speed up their implementation.

3D printing is often seen as an alternative to injection molding. The two technologies can work in collaboration however. As we’ve discussed before a lot of 3D printing applications take place around molding and casting. In this post we will look more specifically into injection molding and how 3D printing can make injection molding processes faster and less expensive.

Why are companies looking into making inserts and cores using 3D printing?

Time and money. Both time and money are key drivers in many business decisions and the use of 3D printing for injection molding is no exception. Molds and inserts made out of metal require significant investments. Often these items will also take weeks to produce. By making unique geometries available quickly, 3D printing can reduce the lead times on these molds and help bring products to market faster. The time to develop the mold and the production time for the mold are reduced. 3D printed molds are often much less expensive to make than conventionally manufactured ones. Especially when time is critical (with project delays, bridge manufacturing, testing, short run series, etc.) 3D printing can be a solution for injection molds. If one compares 3D printing polymers to making molds out of metal the cost savings can be significant indeed.

In conformal cooling channels or conformal cooling inserts 3D printing also has the ability to manufacture shapes that are not able to be made with another process. Conformal cooling channels can also be made as an integrated part of a mold or produced together with the mold itself in one part.

What is delaying the introduction of 3D printing to molding? 

3D printing is however not a panacea. It can be effectively used for many molding applications but is also restricted.

Size: One issue with 3D printing for molding is in size. Generally, 3D printers are only able to make relatively small objects. Desktop 3D printers are restricted to building objects around 20 by 20 by 20 centimeters. Most industrial additive manufacturing machines have maximum sizes of around 50 by 50 by 50 CM. There are some large scale systems that can print parts that are 1 M or more in length. Generally however for small objects one has a lot of vendors, materials and services to choose from to get your part to 3D print. The larger the object however the fewer vendors and materials will remain and the more restricted the pricing.

Part cost: 3D printing materials are expensive so this increases part cost considerably. At the same time large parts take up more machine time which also adds to cost. Polymer 3D printed molds are generally inexpensive when compared to traditionally made ones. Metal 3D printing is however a costly process. Often several parts have to be designed and printed for the part to work well. This means that replacing large metal molds with metal 3D printed ones is cost prohibitive at the moment. Many companies have realized however that in the long run printing injection molds out of metal will let them gain in flexibility and become more efficient. Generally we can see that many industries, especially automotive, are looking to produce metal 3D printed molds at the moment.

Heat deflection: When 3D printing in polymers using technologies such as stereolithography, Polyjet or fused deposition modeling traditionally heat deflection temperatures have been an issue. When 3D printing technologies were first commercialized low heat deflection temperatures were the norm and 3D printing molds was not feasible. As materials and processes have been refined stronger materials with higher heat deflection temperatures have come on the market. Typically however we can say that for many 3D printing materials heat deflection still is an issue and depending on your molding application 3D printing may not be suited because of this.

Pressure: Similarly part strength was an issue as well. 3D printed parts would fail and not be suited to high pressure molding applications. This issue is being ameliorated through higher strength materials.

Surface roughness: Surface roughness of parts often needs improvement as well. Many 3D printed parts benefit from post processing treatments that make the part surface smoother and suited to molding applications. In some cases parts are vapor smoothed, tumbled or sanded down manually to make them suitable for molding. In 3D printing polymers these steps vary from being quite cost effective (tumbling) to being cost prohibitive (manual support removal and sanding down of the entire part).


What is being done in injection molding at the moment? 

There are many applications being explored at the moment in 3D printing for injection molding.

Entire metal 3D printed mold cores: Automotive companies and others are looking at directly 3D printing large scale injection mold cores with metal 3D printing. Cost and size are still an issue for many molds but serious investments are being done in order to ameliorate this.

3D Printed patterns: 3D printed patterns are also being made using 3D printing which are then cast into mold tooling. Depending on your application this could be a more cost effective way to proceed.

Conformal cooling inserts: Conformal cooling channels and conformal cooling channel mold inserts are being 3D printed. 3D printing lets users explore the optimization of these channels through giving them more design freedom.

Rejuvenating and repairing mold cores: Using technologies such as Directed Energy Deposition metal can be 3D printed on top of a mold. Old end of life molds can in this way be rejuvenated and be 3D printed to lengthen their service life. Especially in ultra high volume applications this is an interesting proposition for manufacturers since rejuvenating an injection mold through 3D printing is (often) less expensive than having a new one made through CNC and other processes.

Polymer 3D printed cores and inserts: Fused Deposition Modeling, Stereolithography and Polyjet are being used to make mold cores and inserts. Not suitable for all applications but very cost effective in short run molding applications and molds that need to be made quickly. This solution is often sought either to speed up the tooling process or to meet deadlines that could not be met when waiting for molds to be made in the traditional way. Increasingly companies are turning to 3D printing to save money as well in more general mold applications. In insert molding and other comparatively low heat and pressure injection molding applications more and more 3D printed cores and inserts are being made.

Images courtesy of Sintef, Unilever, Javelin and Bi Link.