APPENDIX B ■ APPENDIX BPreparing to Print
The editable model files are in a proprietary format for each modeling tool. To print them on a 3D printer,
the model must be exported to a commonly understood format. Presently, STL files (STereoLithography) are
the de facto standard.
The advantage of STL files is that almost all of 3D printer software packages can understand that format.
In fact, there are public repositories of STL files where you can find a variety of interesting things to print,
regardless of the modeling tool that originally created them and regardless of your printer. The disadvantage
of STL files is that they are converted to a series of triangles, rather than the primitive shapes that you
originally started with. This makes it difficult to revise or tweak a design.
In Tinkercad, the STL file can be downloaded from the application site. But, regardless of the source, the
printer software must process the file for actual printing. The printer software needs to:
- Include instructions to the printer about the speed and temperature based on
the type of output material - Optionally add rafts and skirts to level the base and ensure the printed object
stays connected to the base platform during printing - Optionally add support columns for thin or floating portions of the model
- Digitally cut the 3D model into hundreds of 2D layers that will be stacked up on
top of each other during printing
Obviously these details differ based on the type of printer and media. Nevertheless, the printer software
converts a standard triangle-based definition of a complex shape into movement instructions that the
specific printer understands.
Printing in 3D
Depending on the printer, the output file can either be copied to a media card or printed directly from the
computer. Printing from the computer lets you view progress, but can destroy a print if the computer crashes
or hangs.
Printing takes a while and can occasionally fail due to a part not staying in place or the media
becoming clogged or stuck. Sometimes a part needs to be resized slightly or reoriented to produce a more
dimensionally accurate piece.
The freshly made part may need some light machining, such as sanding or tapping screw threads.
Consumer 3D printers do not yet have high enough resolution or accuracy to create fine threads, and
threads are difficult to model in beginner modeling programs. So, in this example, the coupler set screw hole
must have threads cut by a thread tapping tool (see Figure B-10).