Designing Rules for 3D Printing

Different 3D printing processes have different capabilities and different design restrictions.

The most important thing to remember while designing for 3D printing is the fact that your digital design will become a physical object. In the digital design environment, there are no laws of physics to adhere to, such as gravity.

Anything can be "drawn" in 3D on a digital canvas, but not everything can be 3D printed.

Each 3D printing process has its own limitations. Here are the most important design considerations that apply to all of them that you should keep in mind:

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Overhangs

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All 3D printing processes build parts layer-by-layer. Material cannot be deposited onto thin air, so every layer must be printed over some underline material

Overhangs are areas of a model that are either partially supported by the layer below or not supported at all. There is a limit on the angle every printer can produce without the need of support material. For example, for FDM and SLA this angle is approximately 45o degrees.

It is a good practice to limit the overhangs of a model, as layers printed over support usually have a rougher surface finish.

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Wall thickness

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The second thing to keep in mind when designing a part to be 3D printed is wall thickness. Every 3D printing process can produce accurately features that are thin up to a certain point.

For example, imagine you are an engineer who designs hang gliders for a living. You have come up with a great, new design that you have decided to 3D print scaled down for testing. 3D modeling programs allow you to model the sailcloth of the wing, but you would encounter problems when you would try to 3D print it, as its thickness would be extremely small.

As a good practice, always add thickness to your models. Walls with thickness greater than 0.8 mm can be printed successfully with all processes.

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Level of detail

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When you are creating a 3D model with intricate details, it is important to keep in mind what is the minimum feature size each 3D printing process can produce. The minimum level of detail is connected to the capabilities and mechanics of each 3D printing process and to the selected layer height.

The process and materials used will have an impact on the speed and cost of your print, so determining whether smaller details are critical to your model is an important design decision.

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Rules of Thumb

• Avoid overhangs in your design when possible, by using angles smaller than 45o.

• Add at least 0.8 mm wall thickness to your models.

• Avoid large flat surfaces and use rounded corners to avoid warping.

• Decide what is the minimum level of detail your models require and choose a 3D printing process accordingly.