The Best of Both Worlds? 3D Printed Injection Molds

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Traditionally, the roles of 3D printing and injection molding have been clear. 3D printing is for making prototypes and injection molding is for high volume production runs. As 3D printing materials are getting better, a hybrid technique has been introduced to combine the two techniques. Now you can 3D print injection molds.

 

You will see 3D printing companies and some injection molders hailing the benefits of this technique while traditional injection molding companies are quick to point out the shortfalls. But what are the benefits and trade-offs using this technique? When is implementing this technique the right choice?

 

Benefits:

Speed

This is the obvious benefit of all 3D printing, the ability to get your first parts quickly. Now this speed can be used to substantially shorten lead times of injection molded parts. With new, stronger materials, injection molds can now be printed in a day instead of the normal 6-8 week lead-time. Parts can be delivered in days instead of months.

 

Iterations

“Cutting steel” is the point where the design has been frozen and ready to move to production and the injection molds start to be made. This no longer has to be the pivotal point. Using 3D printing to make the molds, if a change in the design in necessary, now molds can be ready in a day incorporating the changes. This technique allows for iterations of design using actual injection molded parts.

 

Design

You can now use injection molded parts in your prototypes and low volume runs. You no longer have to make design modification to allow for other manufacturing techniques to be used during prototyping and proof of concept stages. In some cases, you had to make two prototypes, one 3D printed to show how the product will look and one that was machined to show how the product functions.

 

Price

3D printed molds are about 70% cheaper than their metal counterparts. This enables injection molding to be involved much earlier in the design process than ever before.

 

Limitations:

Volume

3D printed molds have a limited life compared to aluminum or steel molds. For soft plastics, about 100 parts can be made before the mold begins to degrade. Of materials that require higher injection temperatures, less than 25 parts might be obtained before new molds need to be created. This is substantially less than the 10,000+ parts of aluminum molds and 1 million+ parts that steel molds can offer.

 

Quality

There is some question of the quality of the final parts produced. Because of how 3D printing works, the quality of the printer can greatly affect the surface finish of the molded parts. 3D printing builds in layers, so the layer divisions may be seen on the final parts. A quick polishing of the molds can reduce or eliminate this concern.

 

Complexity

You can find both advocates and naysayers for how complex the parts made using this technique can produce. On the negative side, the molds are plastic after all. This can limit some design features as thin walls on the mold will be much less rigid than their metal counterparts. In addition, the maximum volume of parts produced in this way is about 10 cubic inches.

 

Expertise

With plastic molds, the mold cool periods will need to be longer. The gates might have to be designed differently. Ejecting pins placement might have to be optimized. This all leads up to the necessity to find injection molding companies that have experience with using 3D printed molds.

 

When to Use:

Currently, 3D printed injection molds have a limited lifecycle and material selection. These is the main limitations on what you can do with this process making them appealing for R&D, prototypes and short run manufacturing. You should use this process when:

 

1. You need the parts to be same strength as final product
2. Want the feature capabilities that injection molding offers
3. Haven’t finalized the product design
4. Only need a small quantity of parts, typically <100

 

By utilizing 3D printed molds, you can minimize the iterations in design and mold dimensions that can occur when changing for machined to molded parts. Remember that this is still a newer technique so to have the most success, find a vendor that has experience in the process.

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