Wednesday, February 1, 2017

3D Printing 101 - Anatomy of an FFF 3D Print

So now that we've talked about the 3D printer, let's talk about the anatomy of an FFF 3D print.
Here is a 3D print stopped before it completed. Looking inside this print the parts of an FFF 3D print can be illustrated.

FFF 3D prints are made in layers. The lowest layer is the first, the next layer goes on top of that, and so on, to the top. 

Each layer starts with an outline, or shell, which traces the shape of the layer once or more times. The more shells there are the thicker the wall of the print. Fewer shells save material and time but makes a less rigid and lighter weight print.

Once the shells are drawn there is an infill pattern drawn next. Notice that this 3D print is mostly hollow, which is typical. This also saves material and time. Of course the bottom few layers are completely filled in and a number of top layers are as well, but the layers in between are a sparse infill. Some prints will work successfully without any infill, but if there are any flat areas then infill provides the bridging required to create a smooth top, though it may take a number of top layers to be successful.

As FFF 3D prints are made in layers, with each layer building on the one below it, if there is a portion of a layer without anything underneath it the print may require supports.

The wizard model shown here, when it prints, gets to a number of areas where, when the layer gets up to them, has nothing under them. FFF 3D printers can't print suspended in midair, so a scaffolding structure was built up to that part.

If the supports are made of the same material as the object, because the FFF 3D printer only has the ability to print in one material at a time, they're called breakaway supports as they are designed to break away after printing completes. The goal of breakaway supports is to make them thin and fragile, but not too thin and fragile because they need to stay until they're needed. usually breakaway supports leave some artifact behind, a scar that will need to be cleaned off before the print can be truly presentable.

Some 3D printers make their supports out of a different material than the build material. Usually this different material is designed to be dissolved away after the print finishes and it can be made much more solid. Dissolvable supports often times leave no artifacts that they were ever there, making supported surfaces as clean as top surfaces. But printers that can use dissolvable supports, and use them well, are more expensive than single material printers.

Some 3D prints don't require any supports. A clever 3D designer can make a part friendly to the FFF process by insuring that each layer has something under it to support. That may mean orienting the piece, breaking the print into parts, or limiting the pose of the character to only those that can be FFF 3D printed.

Layers, outlines, infill, and supports. That's really all there is to 3D prints. However, even these simple parts allow for a great deal of customization in the slicer, which will be the topic of the next chapter.

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