+ Cost of Machine and Material it Uses

+ Build Plate Size and Build Volume

+ Type and Availability of Filament

+ Speed and Precision of Printing

+ Overall Size andPortability of Machine

+ Ease of Maintenance

There are plenty of reviews and online guides available at sites like all3dp.com and Make Magazine.

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FDM Machines

FDM machines have a spool of filament that is fed through a heated extruder head (imagine a precise hot glue gun). Filament is deposited layer by layer to make a part. Fabrication of parts larger than a few inches can take many hours.

SLA Machines

SLA machines draw parts out of a bin of liquid resin. Focused light is used to selectively cure the resin layer by layer as the part comes out of the liquid. Try this article or one of the many other articles and videos available on the web to get more detail on these processes.

If you have only occasional need for 3D printing, but can't afford your own machine currently, their are many online providers of 3D printing services- you send them a file, and they send back the finished item in a few days.

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Slicer Programs in the 3D Printing Process

For the actual 3D printing process, the maker will also need a "slicer" program. Slicers are the programs that take a solid model (typically an .STL file), and create the tool paths ('G-code') for the printer head to follow in creating each layer of the part. Like the 3D printers themselves, there are many slicer programs and they're evolving quickly, but to help, there are online reviews and guides to assist the user.

The industry standard for 3D models is STL (stereo lithography), which breaks a complex shape into a network of triangles. However, 3D printers typically require a specific file type to generate the required tool paths (G-code) and many have proprietary formats. That means that you can only use the slicer that comes with the printer, which is usually free, and can be very high quality. The takeaway here is that when selecting a 3D printer, be aware that you must choose a 3D printer/slicer combination that works for your user community.