Key Design Considerations for 3D Printing

Different 3D printing processes have different capabilities and different design constraints. In this article, we will discuss key design considerations that apply to all 3D printing processes.

We assume you already have some knowledge about 3D design and modeling. The specific design software used to create the 3D model doesn’t matter. If you are completely new to 3D modeling, there are many excellent softwares that can introduce 3D design to beginners, and they also offer a powerful series of video tutorials to help you understand the basics.

 digital and physical

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

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

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

General Design Considerations for 3D Printing

 overhang

All 3D printing processes build the part layer by layer. The material cannot be deposited in thin air, so each layer has to be printed on some underline material.

Overhangs are areas of a model that are partially supported or not supported at all by layers below. There are limits to the angles each printer can produce without requiring support material. For example, for FDM and SLA, the angle is about 45°.

Effect of increasing angle on drape quality of FDM prints

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

wall thickness

The second thing to keep in mind when designing 3D printed parts is wall thickness. Each 3D printing process can precisely produce features that are thin to a certain point.

For example, let’s say you’re an engineer who designs hang gliders for a living. You come up with a great new design and you decide to scale it down to 3D print it for testing. 3D modeling programs allow you to model the canvas of the wing, but you have problems trying to 3D print it because it is so thin.

As a good habit, always add thickness to your models. Walls thicker than 0.8mm can be successfully printed by all processes.

warping

An often overlooked point when designing 3D models is that the materials used for 3D printing undergo physical changes: they are melted, sintered or scanned with a laser and cured. Heating and cooling of the material can cause the part to deform as it is printed.

Large, flat surfaces are particularly prone to warping. Warpage can often be avoided by using the correct machine calibration with adequate surface adhesion between the part and the print bed. A good practice is to avoid large flat surfaces and add rounded corners to the 3D model.

200 micron brown ABS showing lower left corner warpage

level of detail

When creating 3D models with intricate detail, it is important to keep in mind the minimum feature size that each 3D printing process can produce. The minimum level of detail is related to the function and mechanics of each 3D printing process and the selected layer height.

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

Printing with 200 micron FDM, 100 micron FDM, SLA and material jetting (left to right)

Rule of thumb:

  1. Use an angle less than 45° as much as possible to avoid overhang in the design.
  2. Add at least 0.8mm wall thickness to your model.
  3. Avoid large flat surfaces and use rounded corners to avoid warping.
  4. Determine the minimum level of detail required for the model and choose the 3D printing process accordingly.

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