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3D Printing vs Injection Molding


In this post and video we run through how a simple cube can vary between having it manufactured with injection molding. And having it manufactured with 3D Printing. It is a simple example fo Injection Molding vs 3D Printing.


When you are creating a new product it is very important to consider the final manufacturing process right at the start. The ultimate way your product will be produced informs what kinds of features you can have, how the part will look, and ultimately the cost and business model for it.


For our cube example, we assume that a theoretical client wants to come to us and make a 50 millimeter brick. They want to know what it would cost to produce using injection molding or 3D printing.


Designing a Cube for Injection Molding vs 3D Printing


When designing a cube for injection molding, there are several factors to consider. The first thing you have to do is apply a draft angle. This is necessary to allow the cube to be removed from the mold. At least a 1.5-degree angle must be applied to the side of the cube. But the problem is, now your cube us no longer a cube. Steve Jobs himself came up against this issue when he tried to make is NEZT Computer a perfect cube. Ultimately to get the look he desired he radically increased the cost of the tooling to make the enclosure of the computer.


Steve Jobs NEXT Cube


After that, you cannot have a solid brick or a large mass of plastic anywhere in a mold. Thick features will shrink and cause all sorts of problems with the final part. So this cube must have thin walls. In order to get that you have a create a cavity. Removing an entire face of the cube in the process. We made the thin walls two millimeters thick in order to have it be a nice, rigid, functional part.


Lastly we went around and filleted every single sharp edge because sharp edges do not exist in the real world. This will help your tool-maker a lot.


Designing a Cube for 3D Printing


Designing a cube for 3D printing is much simpler. All you have to do is take the design of the cube and fillet all the edges. There are a few other tricks that can be applied. But these mainly focus on automation and reliability features. For a part this simple they are not really necessary.


Unlike the molded part this is a fully solid cube that is now ready to 3D print, so much less design consideration is necessary. 3D Printed parts generally have much more design freedom. But there are best practices that should be followed in order to make a part mass producible. And these will vary based on what your part is and needs to do.


Requesting a Quote for Injection Molded Part

To compare the cost of the two methods, we had the injection molded cube quoted by a third part. We selected draft quality, 10,000 units, and the material was PLA. We requested a 30-day lead time for this project and sent it off to be quoted. It took about two days to come back.


Requesting a Quote for 3D Printed Part

We did the exact same thing on the Slant 3D website, as any client would who is coming to us. We requested 10,000 units, a 30-day lead time, and mentioned that it is a draft quality part meant to be used as a piece of functional hardware. The quotes come back in about one to two days.


3D Printing Vs Injection Molding


Price for 10,000 Injection Molded Parts

The total cost of the parts for the injection molded version of the part was $1.42 per piece, including the injection mold cost itself.


Price for 10,000 3D Printed Parts

The total cost of the parts for the 3D printed version of the part was $1.55 per piece. If the volume increased then the unit cost would decrease.


Conclusion

So the 3D Printed part was ~10% more expensive than the injection molded piece. But this is in not an exact comparison when looking at 3D Printing vs Injection Molding.


Design is only part of the story.

  • The 3D Printed part was created inside of the USA. Not 12000 miles away.

  • The 3D Printed part can be changed at anytime without notable retooling cost

  • The 3D Printed part can be made 100 at a time and adjusted. It is not one big batch and done.

  • The 3D Printed part does not have to be shipped 12000 miles

  • The 3D Printed part is actually a Cube. Not a cube-shaped dish.


3D Printing vs Injection Molding Infographic

3D Printing has plenty of limitations. And it is not always the best option. But no process is. But it can hit scale. And it provides so much more freedom and supply chain flexibility than many of the alternatives.


Please reach out if you have any questions. And we are happy to quote your specific project and needs.







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